United States
Environmental Protection
Agency
EPA/600/R-19/051.1 | July 2019 | www.epa.gov/research
Atsdr
AGENCY FOR TOXIC SUBSTANCES
AND DISEASE REGISTRY
Synthetic Turf Field Recycled Tire Crumb
Rubber Research Under the Federal
Research Action Plan
FINAL REPORT PART 1-
TIRE CRUMB RUBBER CHARACTERIZATION VOLUME 1
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EPA/600/R-19/051.1
July 2019
Synthetic Turf Field Recycled Tire Crumb
Rubber Research Under the Federal
Research Action Plan
Final Report Part 1 -
Tire Crumb Rubber Characterization
Volume 1
July 25, 2019
By
U.S. Environmental Protection Agency / Office of Research and Development (EPA/ORD)
Centers for Disease Control and Prevention / Agency for Toxic Substances and Disease Registry
(CDC/ATSDR)
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Disclaimer
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
The findings and conclusions in this report have not been formally disseminated by the Centers for
Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry and should not
be construed to represent any agency determination or policy.
Preferred citation: U.S. EPA & CDC/ATSDR. (2019). Synthetic Turf Field Recycled Tire Crumb
Rubber Research Under the Federal Research Action Plan Final Report: Part 1 - Tire Crumb
Characterization (Volumes 1 and2). (EPA/600/R-19/051.1). U.S. Environmental Protection Agency,
Centers for Disease Control and Prevention/Agency for Toxic Substances and Disease Registry.
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Foreword
The U.S. Environmental Protection Agency (EPA) Office of Research and Development (ORD) and the
Centers for Disease Control and Prevention (CDC) Agency for Toxic Substances and Disease Registry
(ATSDR) have worked collaboratively to complete the research activities on synthetic turf playing fields
under the "Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields and
Playgrounds." The Agencies plan to release the research activities' results in two parts. This report (Part
1) summarizes the research effort to characterize tire crumb rubber, which includes characterizing the
components of, and emissions from, recycled tire crumb rubber. The exposure characterization report
(Part 2) will summarize the potential exposures that may be experienced by users of synthetic turf
playing fields with recycled tire crumb rubber infill, such as how people come in contact with the
materials, how often and for how long. Part 2 will be released at a later date, along with results from a
planned biomonitoring study conducted by CDC/ATSDR.
The study is not a risk assessment; however, the results of the research described in this and future
reports will advance our understanding of exposure to inform the risk assessment process. We anticipate
that the results from this multi-agency research effort will be useful to the public and interested
stakeholders to understand the potential for human exposure to chemicals found in recycled tire crumb
rubber used on synthetic turf fields.
This report has been prepared to communicate to the public the research objectives, methods, results and
findings for the tire crumb rubber characterization research conducted as part of the Federal Action
Research Plan. The report has undergone independent, external peer review in accordance with EPA and
CDC policies. A summary of key reviewer recommendations and relevant responses on this part of the
research is provided with this report. A response-to-peer review comments document will be released
with Part 2.
The mission of the EPA is to protect human health and the environment so that future generations inherit
a cleaner, healthier environment that supports a thriving economy. Science at EPA provides the
foundation for credible decision-making to safeguard human health and ecosystems from environmental
pollutants. ORD is the scientific research arm of EPA, whose leading-edge research helps provide the
solid underpinning of science and technology for the Agency. ORD supports six research programs that
identify the most pressing environmental health research needs with input from EPA offices, partners
and stakeholders.
CDC works 24/7 to protect America from health, safety and security threats, both foreign and in the
United States. ATSDR is a non-regulatory, environmental public health agency that was established by
Congress under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980.
ATSDR protects communities from harmful health effects related to exposure to natural and man-made
hazardous substances by responding to environmental health emergencies; investigating emerging
environmental health threats; conducting research on the health impacts of hazardous waste sites; and
building capabilities of and providing actionable guidance to state and local health partners.
Jennifer Orme-Zavaleta
Principal Deputy Assistant Administrator for Science
EPA Office of Research and Development
Patrick Breysee
Director
Agency for Toxic Substances and Disease Registry
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Authors, Contributors, and Reviewers
Lead Authors:
Kent Thomas
Elizabeth Irvin-Barnwell
Annette Guiseppi-Elie
Angela Ragin-Wilson
Jose Zambrana, Jr.
U.S. EPA, Office of Research and Development, National Exposure
Research Laboratory (EPA/ORD/NERL)
Centers for Disease Control and Prevention, Agency for Toxic Substances
and Disease Registry (CDC/ATSDR)
U.S. EPA, Office of Research and Development, National Exposure
Research Laboratory (EPA/ORD/NERL)
Centers for Disease Control and Prevention, Agency for Toxic Substances
and Disease Registry (CDC/ATSDR)
U.S. EPA, Office of Research and Development, National Exposure
Research Laboratory (EPA/ORD/NERL)
Collaborating Federal Organizations:
U.S. Consumer Product Safety Commission
U.S. Army Medical Command, Army Public Health Center
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Contributing Authors:
Authors
Affiliation
Kelsey McCall Benson, Michael Lewin, Zheng Li
CDC/ATSDR
Nichole Brinkman, Matthew Clifton, Carry
Croghan, Peter Egeghy, Steven Gardner, Edward
Heithmar, Ashley Jackson, Kasey Kovalcik,
Georges-Marie Momplaisir, Marsha Morgan,
Karen Oliver, Gene Stroup, Mark Strynar,
Jianping Xue, Donald Whitaker, Larissa
Hassinger (Student Services Contractor [SSC],
Oak Ridge Associated Universities [ORAU])
EPA/ORD/NERL
Barbara Jane George
U.S. EPA, Office of Research and Development,
National Health and Environmental Effects
Research Laboratory (EPA/ORD/NHEERL)
Xiaoyu Liu
U.S. EPA, Office of Research and Development,
National Risk Management Research Laboratory
(EPA/ORD/NRMRL)
Monica Linnenbrink
U.S. EPA, Office of Research and Development,
National Center for Computational Toxicology
(EPA/ORD/NCCT)
Linda Phillips
U.S. EPA, Office of Research and Development,
National Center for Environmental Assessment
(EPA/ORD/NCEA)
Chris Carusiello, Ksenija Janjic
U.S. EPA, Office of Land and Emergency
Management, Office of Resource Conservation
and Recovery (EPA/OLEM/ORCR)
Brandon Law, Aleksandr Stefaniak
CDC, The National Institute for Occupational
Safety and Health (CDC/NIOSH)
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Contributors:
Contributors
Affiliation
Lillian Alston (Senior Environmental Employee
[SEE]), Christine Alvarez (Quality Assurance [QA]),
Fu-Lin Chen, Andrea Clements, Michelle Henderson
(QA), Kathleen Hibbert, Tammy Jones-Lepp, Scott
Keely, Asja Korajkic, James McCord (Oak Ridge
Institute for Science and Education [ORISE]
Participant), Larry McMillan (SEE), Brian McMinn,
Myriam Medina-Vera, Maliha Nash, James Noel
(QA), Gary Norris, Brian Schumacher, Brittany Stuart
(QA), Sania Tong-Argao (QA), Elin Ulrich, Margie
Vazquez (QA), Sandra Utile-Okechukwu (ORISE
Participant), Richard Walker (SEE), Alan Williams,
Ron Williams
EPA/ORD/NERL
Desmond Bannon, Debra Colbeck, Ellyce Cook,
William Darby, Patrick Dickinson, Kevin M. Doherty,
Mike Eck, Sherri Hutchens, Jeffrey Killpatrick,
Daysha C. Liggins, Clint Logan, Mark A. Lucas,
Rolando Mancha, Marybeth Markiewicz, Jeffrey K.
Mason, Walter E. Miller, Kenneth Mioduski, Craig S.
Miser, Matt Nicodemus, Todd Richard, Nathan A.
Silsby, Sandy Toscano, Dawn Valdivia, Robert L. von
Tersch, Jenny Ybarra
U.S. Army Public Health Center (APHC)
Holly Ferguson (QA)
EPA/ORD/NHEERL
LibbyNessley (QA)
EPA/ORD/NRMRL
Ann Richard, Antony Williams
EPA/ORD/NCCT
Gregory Grissom (ORISE Participant)
U.S. EPA, Office of Research and
Development, Sustainable and Healthy
Communities Research Program
Susan Burden, Jacqueline McQueen
U.S. EPA, Office of Research and
Development, Office of Science Policy
(EPA/ORD/OSP)
Kelly Widener
U.S. EPA, Office of Research and
Development, National Center for
Environmental Research (EPA/ORD/NCER)
Matt Allen, Tamira Cousett, Christopher Fuller,
Denise Popeo-Murphy
Jacobs Technology Incorporated (JTI)
Julia Campbell, Justicia Rhodus, Samantha Shattuck
Pegasus Technical Services
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Reviewers:
Reviewers
Affiliation
Eric Hooker
U.S. Consumer Product Safety Commission
Kiran Alapaty, Kevin Oshima
EPA/ORD/NERL
Geoffrey Braybrooke, Michael R. Bell, Debra C.
Colbeck, Jarod M. Hanson, Sherri L. Hutchens,
Mark S. Johnson, Jeffrey G. Leach, Charles E.
McCannon, Robert L. von Tersch
APHC
Bob Thompson
EPA/ORD/NRMRL
Michael Firestone, Kathleen Schroeder (SEE)
U.S. Environmental Protection Agency, Office of
the Administrator, Office of Children's Health
Protection (EPA/OA/OCHP)
Nicole Villamizar
EPA/OLEM/ORCR
Marcus Aguilar
U.S. Environmental Protection Agency, Region 9
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Acknowledgments
Contract support to the EPA was provided by Jacobs Technology, Inc under Contract EP-C-15-008, the
Eastern Research Group, Inc. under Contract EP-C-12-029, and Pegasus Technical Services under
Contract EP-C-15-010. Special acknowledgements are given to Justicia Rhodus of Pegasus Technical
Services for technical editing. Authors and contributors included student service contractors to EPA
Larissa Hassinger under Contract EP-D-15-003, and Oak Ridge Institute for Science and Education
(ORISE) participants Gregory Grissom, James McCord, and Sandra Utile-Okechukwu under an
interagency agreement with the Department of Energy. Larry McMillan, Lillian Alston and Richard
Walker were supported under the Senior Environmental Employment Program.
Special acknowledgements are given to the external peer reviewers who reviewed the draft report under
contract EP-C-17-017 with the Eastern Research Group, Inc.
• Alesia Ferguson, MPH, Ph.D.: Associate Professor, College of Public Health, University of
Arkansas Medical Sciences
• Panagiotis Georgopoulos, Ph.D.: Professor, School of Public Health, Rutgers University
• Tee L. Guidotti, MD, MPH: Consultant, Occupational and Environmental Health
• Maria Llompart, Ph.D.: Professor, Department of Analytical Chemistry, University of Santiago
de Compostela, Spain
• Martin Reinhard, Ph.D.: Professor Emeritus, Stanford University
• P. Barry Ryan, Ph.D.: Professor, Rollins School of Public Health, Emory University
• Clifford P. Weisel, Ph.D.: Tenured Professor, Environmental and Occupational Health Sciences
Institute (EOHSI), Rutgers University
Special acknowledgements are given to collaborators at the U.S. Consumer Product Safety Commission,
Army Public Health Center, the National Toxicology Program of the National Institutes of
Environmental Health Sciences, and the California Environmental Protection Agency's Office of
Environmental Health Hazard Assessment.
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Table of Contents
Disclaimer i
Foreword ii
Authors, Contributors, and Reviewers iii
Acknowledgments vii
Table of Contents viii
Acronyms and Abbreviations xxvii
Executive Summary xxxii
1.0 Introduction 1
1.1 Background 1
1.2 The Federal Research Action Plan 2
1.3 Scope and Objectives of EPA, CDC/ATSDR and CPSC Activities 2
1.3.1 Outreach to Key Stakeholders 3
1.3.1.1 Gather and Share Information 3
1.3.1.2 Informing Stakeholders 4
1.3.2 Data and Knowledge Gap Analysis 5
1.3.3 Tire Crumb Rubber Characterization 7
1.4 Report Organization 8
2.0 Summary of Results and Findings 9
2.1 Overview of Research Activities 9
2.2 Tire Crumb Rubber Characterization: Overview of Research Approach, Results and Key
Findings 10
2.2.1 Research Approach 10
2.2.2 Overview of Results and Key Findings 11
2.2.3 Tire Crumb Rubber Characterization Synopsis 17
2.3 Toxicity Reference Information: Overview of Research Approach, Results and Key
Findings 18
2.4 Detailed Summaries of Research Results 19
2.4.1 Recycling Plant and Synthetic Turf Field Recruitment and Sampling 19
2.4.2 Synthetic Turf Field Operations and Maintenance 19
2.4.3 Tire Crumb Rubber Physical, Chemical and Microbiological Characterization 20
2.4.3.1 Particle Size and Characteristics 20
2.4.3.2 Metals 21
2.4.3.3 SVOCs 24
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2.4.3.4 Field Characteristics and Differences in Chemical Substance Levels.... 29
2.4.3.5 Chemical Variability Within and Between Recycling Plants and Fields 32
2.4.3.6 SVOC Suspect Screening and Non-Targeted Chemical Analysis 34
2.4.3.7 Microbiological 35
2.4.4 Tire Crumb Rubber Exposure-Related Availability Characterization 35
2.4.4.1 VOC Emissions 35
2.4.4.2 SVOC Emissions 37
2.4.4.3 Metals Bioaccessibility 39
2.4.5 Toxicity Reference Information 40
2.5 Research Limitations 41
2.5.1 Research Design Constraints 41
2.5.2 Planned Work Not Completed in this Part of the Study 41
2.5.3 Other Limitations 41
2.6 Future Research Recommendations 42
2.7 Conclusions 43
3.0 Tire Crumb Rubber Characterization Methods 45
3.1 Research Design Summary 45
3.1.1 Target Chemicals 48
3.2 Recruiting Recycling Plants and Synthetic Turf Fields 55
3.2.1 Recycling Plant Recruitment and Selection 55
3.2.2 Synthetic Turf Field Recruitment and Selection 55
3.3 Tire Crumb Rubber Sample Collection Method Summaries 56
3.3.1 Recycling Plant Sample Collection 56
3.3.2 Synthetic Turf Field Sample Collection 57
3.4 Synthetic Field Use and Maintenance Questionnaire Administration 61
3.5 Tire Crumb Rubber Sample Processing Method Summaries 61
3.5.1 Recycling Plant Sample Processing 61
3.5.2 Synthetic Turf Field Sample Processing 62
3.6 Tire Crumb Rubber Sample Analysis Method Summaries 64
3.6.1 Moisture Analysis 64
3.6.2 Sand/Rubber Fraction Analysis 64
3.6.3 Gravimetric Particle Size Analysis 65
3.6.4 SEM and EPMA Particle Characterization 65
3.6.4.1 Background 65
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3.6.4.2 Sample Preparation 66
3.6.4.3 SEM Imaging and Particle Size Distribution Analysis 66
3.6.4.4 Electron Probe Microanalysis 66
3.6.5 Microwave-Assisted Acid Extraction and ICP/MS Metals Analysis 66
3.6.5.1 ICP/MS Analysis 67
3.6.6 XRF Metals Analysis 69
3.6.7 Solvent Extraction and Semivolatile Organic Compound (SVOC) Analysis 69
3.6.7.1 Tire Crumb Rubber Extraction 69
3.6.7.2 GC/MS/MS Analysis for Target SVOCs 70
3.6.7.3 GC/MS Analysis for Non-Target SVOCs 70
3.6.7.4 LC/TOFMS Analysis for Target SVOCs 71
3.6.7.5 LC/TOFMS Suspect Screening and Analysis of Non-target SVOCs 72
3.6.8 Dynamic Chamber Emissions Testing 74
3.6.8.1 Tire Crumb Material Preparation for Emission Chamber Tests 74
3.6.8.2 Selection of Test Chambers and Conditions 74
3.6.8.3 Small Chamber Emission Tests 75
3.6.8.4 Micro-Chamber Emissions Tests 78
3.6.9 Bioaccessibility Testing 80
3.6.9.1 Preparation of Artificial Biofluids 80
3.6.9.2 Extraction of Tire Crumb Rubber Constituents in Artificial Biofluids... 80
3.6.9.3 Analytical Methods for Measuring Metals in Biofluids Extracts 81
3.6.9.4 Calculation of In vitro Bioaccessibility 82
3.6.10 Microbial Analysis 82
3.6.10.1 Isolation of Microbes and Microbial Genomic DNA 82
3.6.10.2 Quantification of Targeted Microbial Genes 83
3.6.10.3 Non-targeted Microbial Gene Analysis 83
3.7 Data Processing and Data Analysis for Select Data 84
3.7.1 Data Processing 84
3.7.2 Data Analysis 85
3.7.3 SVOC Decay Time Half-Live Analysis 87
3.7.4 Field Characteristics Modeling Analysis 87
4.0 Tire Crumb Rubber Characterization Results 89
4.1 Overview 89
4.2 Recycling Plant and Synthetic Turf Field Recruitment 90
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4.2.1 Recycling Plant Selection and Recruitment 90
4.2.2 Synthetic Turf Field Selection and Recruitment 90
4.3 Synthetic Field Use and Maintenance Questionnaires 91
4.4 Tire Crumb Rubber Sample Collection and Sub-Sample Preparation 97
4.4.1 Recycling Plant Sample Collection 97
4.4.2 Synthetic Turf Field Sample Collection 97
4.4.3 Preparation and Scheduled Analysis for Tire Crumb Rubber Samples and Sub-
Samples 99
4.5 Tire Crumb Rubber Particle Characterization Results 102
4.5.1 Tire Crumb Rubber Moisture 102
4.5.2 Infill Sand/Rubber Fractions 103
4.5.3 Particle Size Distributions for Recycling Plants and Fields 105
4.5.4 Scanning Electron Microscopy 110
4.5.4.1 Scanning Electron Microscopy Results 110
4.5.4.2 Electron Probe Microanalysis Results 112
4.5.4.3 Summary of SEM/EPMA Studies 114
4.6 Chemical Measurement Summary Statistics 115
4.6.1 Direct Tire Crumb Rubber Chemical Substance Measurements 115
4.6.1.1 Metals by ICP/MS Analysis 115
4.6.1.2 Metals by XRF Analysis 117
4.6.1.3 SVOCs by GC/MS/MS Analysis 119
4.6.1.4 SVOCs by LC/TOFMS Analysis 122
4.6.2 Chemical Emissions from Tire Crumb Rubber 124
4.6.2.1 VOC Emission Factors Analysis 124
4.6.2.2 SVOC Emission Factors Analysis 128
4.6.3 Comparison of Total Infill vs. Sand Corrected Results 134
4.7 Comparison of Recycling Plants and Synthetic Turf Fields 139
4.7.1 Direct Tire Crumb Rubber Measurements 140
4.7.1.1 Metals by ICP/MS and XRF 140
4.7.1.2 SVOCs by GC/MS/MS 141
4.7.1.3 SVOCs by LC/TOFMS 144
4.7.2 Chemical Emissions from Tire Crumb Rubber 146
4.7.2.1 VOCs Emission Factors 146
4.7.2.2 SVOC Emission Factors 147
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4.8 Comparison of Emission Factors at 25 °C and 60 °C 149
4.8.1 VOC Emission Factors 150
4.8.2 SVOC Emission Factors 152
4.9 Heterogeneity/Homogeneity Assessments 154
4.9.1 Measurement Precision and Sample Variability 155
4.9.2 Variability Within and Between Recycling Plants or Synthetic Turf Fields 160
4.9.2.1 Metals by ICP/MS Analysis 160
4.9.2.2 SVOC Extracts by GC/MS/MS Analysis 164
4.9.2.3 VOC Emission Factors Analysis 170
4.9.2.4 SVOC Emission Factors Analysis 176
4.10 Assessment of Characteristics Potentially Associated with Differences Among Synthetic
Turf Fields 182
4.10.1 Outdoor versus Indoor Synthetic Turf Fields 183
4.10.1.1 Metals by ICP/MS and XRF Analysis 183
4.10.1.2 SVOC Extracts by GC/MS/MS and LC/TOFMS Analysis 184
4.10.1.3 VOC Emission Factors 188
4.10.1.4 SVOC Emission Factors 190
4.10.2 Synthetic Field Installation Age 192
4.10.2.1 Metals by ICP/MS and XRF Analysis 193
4.10.2.2 SVOC Extracts by GC/MS/MS and LC/TOFMS Analysis 195
4.10.2.3 VOC Emission Factors 199
4.10.2.4 SVOC Emission Factors 201
4.10.3 Synthetic Field Installation Age Restricted to Outdoor Fields 203
4.10.3.1 Metals by ICP/MS and XRF Analysis 203
4.10.3.2 SVOC Extracts by GC/MS/MS and LC/TOFMS 206
4.10.3.3 VOC Emission Factors 210
4.10.3.4 SVOC Emission Factors 212
4.10.4 Decay Rates of SVOCs Over Time at Outdoor Fields 214
4.10.5 Geographic Region 219
4.10.5.1 Metals by ICP/MS and XRF 219
4.10.5.2 SVOC Extracts by GC/MS/MS and LC/TOFMS 221
4.10.5.3 VOC Emission Factors 227
4.10.5.4 SVOC Emission Factors 229
4.10.6 Linear Model Analysis for Field Characteristics 231
4.11 Suspect Screening Chemical Analysis 234
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4.12 Non-Targeted Chemical Analysis 237
4.13 Bioaccessibility Testing for Metals 242
4.14 Microbiological Analysis 260
4.14.1 Targeted Microbial Analysis 260
4.14.2 Non-targeted Microbial Analysis 266
4.15 Initial Testing of Silicone Wristbands 267
4.15.1 Dynamic Chamber Testing of Wristbands 267
5.0 Toxicity Reference Information 269
5.1 Background 269
5.2 Approach 269
5.3 Results 271
5.4 Conclusions 281
6.0 References 283
7.0 Appendices 291
List of Figures
Figure 2-1. Average measurement results for metals in tire crumb rubber samples collected from tire
recycling plants and indoor and outdoor synthetic turf fields with tire crumb rubber infill... 11
Figure 2-2. Average measurement results for selected extractable polyaromatic hydrocarbons in tire
crumb rubber samples 12
Figure 2-3. Example close-up photos of tire crumb rubber infill collected at four synthetic turf fields
showing a range of particle sizes 20
Figure 2-4. ICP/MS metal analysis results (mg/kg) for tire crumb rubber collected from tire recycling
plants and tire crumb rubber infill composite samples from synthetic turf fields for lead
and zinc 21
Figure 2-5. Average measurement results for phthalates in solvent extraction samples from tire crumb
rubber collected at tire recycling plants (n=9), indoor synthetic turf fields (n=15), and
outdoor synthetic turf fields (n=25) 24
Figure 2-6. Average measurement results for select semivolatile organic compounds in solvent
extraction samples from tire crumb rubber collected at tire recycling plants (n=9), indoor
synthetic turf fields (n=15), and outdoor synthetic turf fields (n=25) 25
Figure 2-7. Average relative chromatographic peak area count results for select semivolatile organic
compounds in solvent extraction samples from tire crumb rubber collected at tire recycling
plants (n=9), indoor synthetic turf fields (n=15), and outdoor synthetic turf fields (n=25). .. 25
Figure 2-8. Example comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire
rubber collected from tire recycling plants and tire crumb rubber infill composite samples
from synthetic turf fields for pyrene and benzothiazole 26
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Figure 2-9. Comparison of analysis results (mg/kg) between tire crumb rubber infill composite
samples from indoor and outdoor synthetic turf fields for zinc, 4-tert-octylphenol, pyrene
and benzo[a]pyrene 30
Figure 2-10. Analysis results (mg/kg) for tire crumb rubber from tire recycling plants and tire crumb
rubber infill composite samples from synthetic turf fields with different characteristics by
age group 31
Figure 2-11. Within-plant and within-field variability of zinc, pyrene and benzothiazole measurements
at each of the nine tire recycling plants (left side) and each of the five synthetic turf fields
(right side) 33
Figure 2-12. Comparison of volatile organic compound 60 °C emission factor results (ng/g/h) between
tire rubber collected from tire recycling plants and tire crumb rubber infill composite
samples from synthetic turf fields for formaldehyde and methyl isobutyl ketone 36
Figure 2-13. Comparison of volatile organic compound 25 °C and 60 °C emission factor results
(ng/g/h) for tire crumb rubber infill collected from synthetic turf fields for benzothiazole
and styrene 37
Figure 2-14. Comparison of semivolatile organic compound (SVOC) 60 °C emission factor results
(ng/g/h) between tire rubber collected from tire recycling plants and tire crumb rubber
infill composite samples from synthetic turf fields for Suml5PAH and 4-tert-octylphenol. 38
Figure 2-15. Comparison of semivolatile organic compound (SVOC) 25 °C and 60 °C emission
factor results (ng/g/h) for tire rubber infill collected from synthetic turf fields for
Suml5PAH and 4-tert-octylphenol 39
Figure 3-1. Tire crumb rubber characterization research schematic overview 46
Figure 3-2. United States census regions 47
Figure 3-3. Summary of chemical, physical and microbial analyses performed for tire crumb rubber
characterization 48
Figure 3-4. Schematic representation of tire crumb rubber sample collection at tire recycling plants. .. 57
Figure 3-5. Sample collection locations for rectangular synthetic turf fields, including soccer, football
and other rectangular fields 57
Figure 3-6. Sample collection locations for baseball and softball synthetic turf fields with A) turf in
the infield and B) no turf in the infield 58
Figure 3-7. Schematic representation of the four samples that were collected at each of the seven
locations on each field 58
Figure 3-8. Sample collection kit for metal, organic and particle sample collection at synthetic turf
fields 59
Figure 3-9. Sample collection kit for microbial sample collection at synthetic turf fields 60
Figure 3-10. Sample collection methods using A, B) combs and C) spatulas to remove tire crumb
rubber from about the top 3 cm of the synthetic turf field surface 61
Figure 3-11. Schematic showing composite and individual location sample preparation and analysis
for samples collected at synthetic turf fields 63
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Figure 3-12. Small emission chamber set-up, including A) sealed 53-L chamber in incubator
cabinet; B) 15 g tire crumb rubber infill sample prepared for testing; C) chamber interior
with sample in place and mixing fan pulled out; D) external manifold for air sample
collection 76
Figure 3-13. Micro chamber set-up, including A) (J.-CTE™ system; B) 10 g tire crumb rubber infill
samples in micro-chamber cups; C) samples placed in micro chamber for testing 78
Figure 3-14. Example boxplot annotated with descriptive statistics and sample values 87
Figure 4-1. Average % moisture in tire crumb rubber infill from synthetic turf fields, by field ID 102
Figure 4-2. Average % moisture in tire crumb rubber from recycling plants, by plant ID 103
Figure 4-3. Percent sand in tire crumb rubber infill, by synthetic turf field ID 104
Figure 4-4. Example synthetic turf field infill material without sand (Field 14) and with sand
(Field 32) 105
Figure 4-5. Tire crumb rubber particle size distributions for nine recycling plants (three samples from
each plant) 106
Figure 4-6. Tire crumb rubber infill particle size distributions for 40 synthetic turf fields 107
Figure 4-7. Example photos of tire crumb rubber infill collected from five synthetic turf fields 107
Figure 4-8. Example close-up photos of tire crumb rubber infill collected at six synthetic turf fields.. 108
Figure 4-9. Representative electron micrograph of small particles seived from a recycling plant tire
crumb rubber sample 110
Figure 4-10. Representative histogram of the frequency of individual particle areas observed in the
bottom pan sample Ill
Figure 4-11. A) Electron micrograph of small particle cluster from a field sample; B) EPMA
spectrum of the center of the large center particle; C) Spectrum of smaller particle above
the central particle 113
Figure 4-12. Three EPMA element mapping images. A) Original electron micrograph; B) Sulfur map
indicating primary rubber particle; and C) multielement map showing inclusions probably
steel (Fe+Cr) and possibly soil (Si, Ca) 114
Figure 4-13. A) Backscatter electron micrograph of a recycling plant sample, and B) elemental
mapping of sulfur, silicon, and calcium 114
Figure 4-14. ICP/MS metal analysis results (mg/kg) for chromium, cobalt, lead, and zinc from tire
crumb rubber infill composite samples collected from each synthetic turf field 117
Figure 4-15. GC/MS/MS extract analysis results (mg/kg) for phenanthrene, pyrene, benzo[a]pyrene,
and the sum of 15 PAH from tire crumb rubber infill composite samples collected from
each synthetic turf field 121
Figure 4-16. GC/MS/MS extract analysis results (mg/kg) for benzothiazole, 4-tert-octylphenol,
bis(2-ethylhexyl) phthalate, and n-hexadecane from tire crumb rubber infill composite
samples collected from each synthetic turf field 122
Figure 4-17. VOC 60 °C emission factor results (ng/g/h) for formaldehyde, benzothiazole, methyl
isobutyl ketone, and styrene from tire crumb rubber infill composite samples collected
from each synthetic turf field 126
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Figure 4-18. SVOC 60 °C emission factor results (ng/g/h) for pyrene, the sum of 15 PAHs,
benzothiazole, and 4-tert-octylphenol from tire crumb rubber infill composite samples
collected from each synthetic turf field 131
Figure 4-19. Distributions of select metals analyzed by ICP/MS in tire crumb rubber infill samples
collected from synthetic turf fields, with and without correction for infill sand content 136
Figure 4-20. Distributions of select SVOCs in solvent extracts analyzed by GC/MS/MS from tire
crumb rubber infill samples collected from synthetic turf fields, with and without
correction for infill sand content 139
Figure 4-21. Comparison of ICP/MS metal analysis results (mg/kg) between tire crumb rubber
collected from tire recycling plants and tire crumb rubber infill composite samples from
synthetic turf fields for chromium, cobalt, lead, and zinc 141
Figure 4-22. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber collected from tire recycling plants and tire crumb rubber infill composite samples
from synthetic turf fields for phenanthrene, pyrene, benzo[a]pyrene, and the sum of 15
PAHs 143
Figure 4-23. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber collected from tire recycling plants and tire crumb rubber infill composite samples
from synthetic turf fields for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl) phthalate,
and n-hexadecane 144
Figure 4-24. Comparison of LC/TOFMS positive ionization extract SVOC non-quantitative analysis
results (chromatographic area counts) between tire crumb rubber collected from tire
recycling plants and tire crumb rubber infill composite samples from synthetic turf fields
for 2-mercaptobenzothiazole, 2-hydroxybenzothiazole, cyclohexylamine, and di-
cyclohexylamine 145
Figure 4-25. Comparison of VOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
collected from tire recycling plants and tire crumb rubber infill composite samples from
synthetic turf fields for formaldehyde, benzothiazole, methyl isobutyl ketone, and
styrene 147
Figure 4-26. Comparison of SVOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
collected from tire recycling plants and tire crumb rubber infill composite samples from
synthetic turf fields for pyrene, the sum of 15 PAHs, benzothiazole, and
4-tert-octylphenol 149
Figure 4-27. Comparison of VOC 25 °C and 60 °C emission factor results (ng/g/h) for formaldehyde,
benzothiazole, methyl isobutyl ketone, and styrene from tire crime rubber collected from
recycling plants 150
Figure 4-28. Comparison of VOC 25 °C and 60 °C emission factor results (ng/g/h) for formaldehyde,
benzothiazole, methyl isobutyl ketone, and styrene from tire crumb rubber infill collected
from synthetic turf fields 151
Figure 4-29. Comparison of VOC 25 °C and 60 °C emission factor results (ng/g/h) for SumBTEX
from tire crumb rubber collected from recycling plants and tire crumb rubber infill
collected from synthetic turf fields 152
Figure 4-30. Comparison of SVOC 25 °C and 60 °C emission factor results (ng/g/h) for pyrene, the
sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol from tire crumb rubber collected
from tire recycling plants 153
xvi
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Figure 4-31. Comparison of SVOC 25 °C and 60 °C emission factor results (ng/g/h) for pyrene, the
sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol from tire crumb rubber infill
collected from synthetic turf fields 154
Figure 4-32. Within-tire recycling plant variability (left side) and within-synthetic turf field
variability (right side) for ICP/MS metal analysis results (mg/kg) in tire crumb rubber for
cobalt, lead, and zinc 163
Figure 4-33. Within-tire recycling plant variability (left side) and within-synthetic turf field
variability (right side) for GC/MS/MS extract SVOC analysis results (mg/kg) in tire
crumb rubber for phenanthrene, pyrene, benzo[a]pyrene, and the sum of 15 PAHs 167
Figure 4-34. Within-tire recycling plant variability (left side) and within-synthetic turf field
variability (right side) for GC/MS/MS extract SVOC analysis results (mg/kg) in tire
crumb rubber for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl) phthalate, and
n-hexadecane 168
Figure 4-35. Within-tire recycling plant variability (left side) and within-synthetic turf field
variability (right side) variability for VOC emission factor 60 °C analysis results (ng/g/h)
in tire crumb rubber for formaldehyde, benzothiazole, and methyl isobutyl ketone 174
Figure 4-36. Within-tire recycling plant variability (left side) and within-synthetic turf field
variability (right side) variability for SVOC emission factor 60 °C analysis results
(ng/g/h) in tire crumb rubber for pyrene, benzothiazole, 4-tert-octylphenol 180
Figure 4-37. Comparison of ICP/MS metal analysis results (mg/kg) between tire crumb rubber infill
composite samples from indoor and outdoor synthetic turf fields for chromium, cobalt,
lead, and zinc 184
Figure 4-38. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber infill composite samples from indoor and outdoor synthetic turf fields for
phenanthrene, pyrene, benzo[a]pyrene, and the sum of 15 PAHs 186
Figure 4-39. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber infill composite samples from indoor and outdoor synthetic turf fields for
benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl) phthalate, and n-hexadecane 187
Figure 4-40. Comparison of LC/TOFMS extract SVOC non-quantitative positive ionization analysis
results between tire crumb rubber infill composite samples from indoor and outdoor
synthetic turf fields for 2-mercatpobenzothiazole, 2-hydroxybenzothiazole,
cyclohexylamine, di-cyclohexylamine 188
Figure 4-41. Comparison of VOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
infill composite samples from indoor and outdoor synthetic turf fields for formaldehyde,
benzothiazole, methyl isobutyl ketone, and styrene 190
Figure 4-42. Comparison of SVOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
infill composite samples from indoor and outdoor synthetic turf fields for pyrene, the
sum of 15 PAHs, benzothiazole, 4-tert-octylphenol 192
Figure 4-43. Comparison of ICP/MS metal analysis results (mg/kg) between tire crumb rubber infill
composite samples from synthetic turf fields in three installation age groups for
chromium, cobalt, lead, and zinc 193
xvii
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Figure 4-44. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber infill composite samples from synthetic turf fields in three installation age groups
for phenanthrene, pyrene, benzo[a]pyrene, and the sum of 15 PAHs 197
Figure 4-45. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber infill composite samples from synthetic turf fields in three installation age groups
for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl) phthalate, and n-hexadecane 198
Figure 4-46. Comparison of LC/TOFMS extract SVOC non-quantitative positive ionization analysis
results between tire crumb rubber infill composite samples from synthetic turf fields in
three installation age groups for 2-mercaptobenzothiazole, 2-hydroxybenzothiazole,
cyclohexylamine, and di-cyclohexylamine 199
Figure 4-47. Comparison of VOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
infill composite samples from synthetic turf fields in three installation age groups for
formaldehyde, benzothiazole, methyl isobutyl ketone, and styrene 201
Figure 4-48. Comparison of SVOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
infill composite samples from synthetic turf fields in three installation age groups for
pyrene, the sum of 15 PAHs, benzothiazole, and 4-tert- octylphenol 203
Figure 4-49. Comparison of ICP/MS metal analysis results (mg/kg) between tire crumb rubber from
recycling plants and tire crumb rubber infill composite samples from synthetic turf fields
by age group for chromium, cobalt, lead, and zinc 204
Figure 4-50. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber from recycling plants and tire crumb rubber infill composite samples from
synthetic turf fields by age group for phenanthrene, pyrene, benzo(a)pyrene, and the sum
of 15 PAHs 208
Figure 4-51. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber from recycling plants and tire crumb rubber infill composite samples from
synthetic turf fields by age group for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl)
phalate, and n-hexadecane 209
Figure 4-52. Comparison of LC/TOFMS extract SVOC non-quantitative positive ionization analysis
results between tire crumb rubber from recycling plants and tire crumb rubber infill
composite samples from synthetic turf fields by age group. Results for fields are shown
separately for indoor and outdoor fields in two or three installation age groups for 2-
mercaptobenzothiazole, 2-hydroxybenzothiazole, cyclohexylamine, di-cyclohexylamine. 210
Figure 4-53. Comparison of VOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
from recycling plants and tire crumb rubber infill composite samples from synthetic turf
fields by age group for formaldehyde, benzothiazole, methyl isobutyl ketone, and
styrene 212
Figure 4-54. Comparison of SVOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
from recycling plants and tire crumb rubber infill composite samples from synthetic turf
fields by age group. Results for fields are shown separately for indoor and outdoor fields
in two or three installation age groups for pyrene, the sum of 15 PAHs, benzothiazole,
and 4-tert-octylphenol 214
Figure 4-55. Concentrations of select extractable PAHs in outdoor field composite tire crumb rubber
infill samples versus years since field installation 215
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Figure 4-56. Concentrations of select extractable phthalates and other SVOCs in outdoor field
composite tire crumb rubber infill samples versus years since field installation 216
Figure 4-57. Comparison of ICP/MS metal analysis results (mg/kg) between tire crumb rubber infill
composite samples from synthetic turf fields in four U.S. census regions for chromium,
cobalt, lead, and zinc 221
Figure 4-58. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber infill composite samples from synthetic turf fields in four U.S. census regions for
phenanthrene, pyrene, benzo[a]pyrene, and the sum of 15 PAHs 224
Figure 4-59. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between tire crumb
rubber infill composite samples from synthetic turf fields in four U.S. census regions for
benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl) phthalate, and n-hexadecane 225
Figure 4-60. Comparison of LC/TOFMS extract SVOC non-quantitative positive ionization analysis
results between tire crumb rubber infill composite samples from synthetic turf fields in
four U.S. census regions for 2-mercaptobenzothiazole, 2-hydroxybenzothiazole,
cyclohexylamine, di-cyclohexylamine 226
Figure 4-61. Comparison of VOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
infill composite samples from synthetic turf fields in four U.S. census regions for
formaldehyde, benzothiazole, methyl isobutyl ketone, and styrene 227
Figure 4-62. Comparison of SVOC 60 °C emission factor results (ng/g/h) between tire crumb rubber
infill composite samples from synthetic turf fields in four U.S. census regions for pyrene,
the sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol 229
Figure 4-63. Example GC/MS SVOC solvent extraction sample analysis showing total ion current
and extracted ion current chromatograms for a recycling plant sample 238
Figure 4-64. Example GC/TOFMS VOC 60 °C chamber emission sample analysis total ion current
chromatogram for a synthetic turf field 238
Figure 4-65. Mean loglO concentrations of 16S rRNA genes, S. aureus SA0140 protein gene and
mecA methicillin-resistance genes in samples collected from outdoor (n=172) and indoor
(n=104) artificial turf fields 262
List of Tables
Table 2-1. Topic Areas and Specific Activities Described in This Report 9
Table 2-2. Comparison of Select Tire Crumb Rubber Metal Analysis Results Across Multiple Studies 14
Table 2-3. Comparison of Selected Tire Crumb Rubber Extractable SVOC Analysis Results Across
Multiple Studies 14
Table 2-4. Comparison of Tire Crumb Rubber Metal Analysis Results Across Multiple Studies 23
Table 2-5. Comparison of Tire Crumb Rubber Extractable SVOC Analysis Results Across Multiple
Studies 27
Table 3-1. Target Metal Analytes in Tire Crumb Rubber Samples Analyzed by ICP/MS and XRF 49
Table 3-2. Target VOC Analytes in Tire Crumb Rubber Emission Samples Analyzed by GC/TOFMS 50
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Table 3-3. Target SVOC Analytes for Tire Crumb Rubber Extraction and Emission Samples
Analyzed by GC/MS/MS 51
Table 3-4. Target SVOC Analytes for Tire Crumb Rubber Extraction and Emission Samples
Analyzed by LC/TOFMS 52
Table 3-5. Target SVOC Analytes for Suspect Screening Analysis of Tire Crumb Rubber and
Emissions Samples by LC/TOFMS 52
Table 3-6. Sample Preparation and Analysis of Tire Crumb Rubber Samples Collected at Tire
Recycling Plants 61
Table 3-7. HR-ICPMS Method Settings and Parameters 68
Table 3-8. GC/MS/MS Parameters for Target SVOC Analysis 70
Table 3-9. GC/MS Parameters for Non-target SVOC Analysis 71
Table 3-10. HPLC Gradient Program Used for Characterization of Tire Crumb Rubber Samples 72
Table 3-11. List of Target SVOC Analytes for LC/TOFMS Analysis 72
Table 3-12. Reference Masses for Real-time Mass Correction in TOFMS Analysis 74
Table 3-13. TD/GC/TOFMS Parameters for VOC Chamber Emission Sample Analysis 77
Table 3-14. Methods for Measuring Metals in Biofluid Extract 81
Table 4-1. Research Area and Research Activity Results Reported in This Section 89
Table 4-2. Synthetic Turf Field Recruitment Efforts, by U.S. Census Region 90
Table 4-3. Synthetic Turf Fields Recruited, by Field Type (Outdoor and Indoor) and U.S. Census
Region 90
Table 4-4. Synthetic Turf Fields Recruited, by Installation Year Group and U.S. Census Region 91
Table 4-5. Synthetic Turf Fields Recruited, by Field Type (Outdoor and Indoor) and Installation Year
Group 91
Table 4-6. Relationship of Questionnaire Interviewee to Facility 91
Table 4-7. Tire Crumb Rubber Maintenance (Refreshment by Partial Addition or Replacement) at
Recruited Synthetic Turf Fields 92
Table 4-8. Frequency of Tire Crumb Rubber Maintenance at Recruited Synthetic Turf Field(s) Having
Experienced Tire Crumb Refresh or Replacement 92
Table 4-9. Synthetic Turf Field Treatment with Cleaners, Biocides, Herbicides, Insecticides,
Fungicides, or Other Agents 93
Table 4-10. Products Used to Treat Synthetic Turf Fields and Frequency of Treatment 93
Table 4-11. Synthetic Turf Field Maintenance Activities 93
Table 4-12. Frequency of Synthetic Turf Field Maintenance Activities 94
Table 4-13. Synthetic Turf Fields Open to the Public 94
Table 4-14. Synthetic Turf Field Use Limited to Organization or Membership 94
Table 4-15. Open or Free-Play at the Facility 94
Table 4-16. Days per Week Synthetic Turf Fields Open During Each Season 95
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Table 4-17. Average Hours per Day Synthetic Turf Fields Used per Season 95
Table 4-18. Number of People per Day Using Synthetic Turf Fields per Season 96
Table 4-19. Frequencies of Average Number of People per Day Using Synthetic Turf Fields per
Season 96
Table 4-20. Types of Sports Played on Synthetic Turf Fields 96
Table 4-21. Standard Practices in Place to Reduce Tire Crumb Exposure to People Using the
Synthetic Fields 96
Table 4-22. Samples Collected for Analyses at Synthetic Turf Fields 98
Table 4-23. Individual Field Characteristics 98
Table 4-24. Number of Recycling Plant and Synthetic Turf Field Tire Crumb Rubber Samples
Prepared for Analyses 99
Table 4-25. Scheduled Numbers of Sample Analyses for Tire Crumb Rubber Characterization 100
Table 4-26. Moisture Content in Tire Crumb Rubber from Recycling Plants and Infill from Synthetic
Turf Fields 102
Table 4-27. Sand Fraction in Tire Crumb Rubber Infill Collected at Synthetic Turf Fields 104
Table 4-28. Particle Size Fraction Summary Statistics for Tire Crumb Rubber Collected at Tire
Recycling Plants and Tire Crumb Rubber Infill Collected at Synthetic Turf Fields 105
Table 4-29. Comparison of Particle Size Fractions for Tire Crumb Rubber Infill at Outdoor and
Indoor Synthetic Turf Fields 108
Table 4-30. Comparison of Particle Size Fractions for Tire Crumb Rubber Infill at Synthetic Turf
Fields in Three Field Installation Age Groups 109
Table 4-31. Comparison of Particle Size Fractions for Tire Crumb Rubber Infill at Synthetic Turf
Fields in Four Geographic Regions 109
Table 4-32. Particle Areas for Tire Crumb Rubber at Recycling Plants and Synthetic Turf Fields Ill
Table 4-33. Quartile Analyses of Recycling Plant and Synthetic Turf Field Particle Numbers in the
Bottom Sieve Pan (< 0.063 mm) Samples 112
Table 4-34. Summary Statistics for Select Metals Analyzed by ICP/MS in Tire Crumb Rubber
Samples Collected from Tire Recycling Plants and Tire Crumb Rubber Collected from
Synthetic Turf Fields 116
Table 4-35. Summary Statistics for Selected Metals Analyzed by XRF in Tire Crumb Rubber
Samples Collected from Tire Recycling Plants and Tire Crumb Rubber Infill collected
from Synthetic Turf Fields 118
Table 4-36. Summary Statistics for Selected SVOCs Analyzed by GC/MS/MS in Solvent Extracts
for Tire Crumb Rubber Samples Collected from Tire Recycling Plants and Tire Crumb
Rubber Infill Collected from Synthetic Turf Fields 120
Table 4-37. Summary Statistics for Selected SVOCs Analyzed Non-quantitatively by LC/TOFMS
in Solvent Extracts for Tire Crumb Rubber Samples Collected from Tire Recycling Plants
and Tire Crumb Rubber Infill Collected from Synthetic Turf Fields 123
xxi
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Table 4-38. Summary Statistics for Selected VOC 25 °C Emission Factors for Tire Crumb Rubber
Samples Collected from Tire Recycling Plants and Tire Crumb Rubber Infill Collected
from Synthetic Turf Fields 125
Table 4-39. Summary Statistics for Selected VOC 60 °C Emission Factors for Tire Crumb Rubber
Samples Collected from Tire Recycling Plants and Tire Crumb Rubber Infill Collected
from Synthetic Turf Fields 127
Table 4-40. Summary Statistics for Select SVOC 25 °C Emission Factors for Tire Crumb Rubber
Samples Collected from Tire Recycling Plants and Tire Crumb Rubber Infill Collected
at Synthetic Turf Fields 129
Table 4-41. Summary Statistics for Select SVOC 60 °C Emission Factors for Tire Crumb Rubber
Samples Collected from Tire Recycling Plants and Tire Crumb Rubber Infill Collected
from Synthetic Turf Fields 130
Table 4-42. Summary Statistics for Select SVOC 60 °C Emission Samples Analyzed Non-
quantitatively by LC/TOFMS for Tire Crumb Rubber Samples Collected from Tire
Recycling Plants and Tire Crumb Rubber Infill Collected from Synthetic Turf Fields 133
Table 4-43. Summary Statistics for Select Metals Analyzed by ICP/MS in Tire Crumb Rubber Infill
Samples Collected from Synthetic Turf Fields, With and Without Correction for Infill
Sand Content 135
Table 4-44. Summary Statistics for Select SVOCs Analyzed by GC/MS/MS in Solvent Extracts for
Tire Crumb Rubber Infill Samples, With and Without Correction for Infill Sand Content. 137
Table 4-45. Comparison of Selected Metal Analysis Results Between Tire Rubber Collected from
Tire Recycling Plants and Tire Crumb Rubber Infill Composite Samples from Synthetic
Turf Fields 140
Table 4-46. Comparison of Select SVOC GC/MS/MS Analysis Results Between Tire Rubber Solvent
Extracts for Samples Collected from Tire Recycling Plants and Synthetic Turf Fields 142
Table 4-47. Comparison of Select SVOC LC/TOFMS Non-quantitative Analysis Results Between
Tire Rubber Solvent Extracts for Samples Collected from Tire Recycling Plants and
Synthetic Turf Fields 145
Table 4-48. Comparison of Select VOC Emission Factor Results Between Tire Rubber Collected
from Tire Recycling Plants and Tire Crumb Rubber Infill Composite Samples from
Synthetic Turf Fields 146
Table 4-49. Comparison of Select SVOC Emission Factor Results Between Tire Rubber Collected
from Tire Recycling Plants and Tire Crumb Rubber Infill Composite Samples from
Synthetic Turf Fields 148
Table 4-50. Precision and Variability of Tire Crumb Rubber Sample Digestion Metals Measurements
by ICP/MS 156
Table 4-51. Precision and Variability of Tire Crumb Rubber Sample Solvent Extract SVOC
Measurements by GC/MS/MS 156
Table 4-52. Precision of Replicate Extracts Analyses for Chamber Emission SVOC Measurements
by GC/MS/MS 157
Table 4-53. Variability of 25°C and 60°C Chamber Emission SVOC Measurements by GC/MS/MS . 158
xxii
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Table 4-54. Precision and Variability of 25°C Chamber Emission VOC Measurements by
GC/TOFMS
159
Table 4-55. Precision and Variability of 60°C Chamber Emission VOC Measurements by
GC/TOFMS 160
Table 4-56. Select ICP/MS Measurement Results for Individual Tire Crumb Rubber Samples
Collected at Nine Recycling Plants for Assessing Within-Plant Variability 161
Table 4-57. Select ICP/MS Measurement Results for Individual Location Tire Crumb Rubber Infill
Samples Collected at Five Synthetic Turf Fields for Assessing Within-Field Variability.. 162
Table 4-58. Within- and Between-recycling Plant or Field Variability for Select Metal ICP/MS
Analysis Results for Tire Crumb Rubber Collected from Tire Recycling Plants and Tire
Crumb Rubber Infill Collected from Synthetic Turf Fields 164
Table 4-59. Select SVOC Extraction GC/MS/MS Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-Plant
Variability 165
Table 4-60. Select SVOC Extraction GC/MS/MS Measurement Results for Individual Location Tire
Crumb Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing
Within-Field Variability 166
Table 4-61. Within- and Between-recycling Plant or Field Variability for Select SVOC Extraction
GC/MS/MS Analysis Results for Tire Crumb Rubber Collected from Tire Recycling
Plants and Tire Crumb Rubber Infill Collected from Synthetic Turf Fields 169
Table 4-62. Select VOC 25 °C Emission Factor Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-Plant
Variability 170
Table 4-63. Select VOC 25 °C Emission Factor Measurement Results for Individual Location Tire
Crumb Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing
Within-Field Variability 171
Table 4-64. Select VOC 60 °C Emission Factor Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-plant
Variability 171
Table 4-65. Select VOC 60 °C Emission Factor Measurement Results for Individual Location Tire
Crumb Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing
Within-field Variability 172
Table 4-66. Within- and Between-recycling Plant or Field Variability for Select VOC 25 °C Emission
Factor Analysis Results for Tire Crumb Rubber Collected from Tire Recycling Plants
and Tire Crumb Rubber Infill Collected from Synthetic Turf Fields 175
Table 4-67. Within- and Between-recycling Plant or Field Variability for Select VOC 60 °C Emission
Factor Analysis Results for Tire Crumb Rubber Collected from Tire Recycling Plants
and Tire Crumb Rubber Infill Collected from Synthetic Turf Fields 175
Table 4-68. Select SVOC 25 °C Emission Factor Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-Plant
Variability 176
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Table 4-69. Select SVOC 25 °C Emission Factor Measurement Results for Individual Location
Tire Crumb Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing
Within-Field Variability 177
Table 4-70. Select SVOC 60 °C Emission Factor Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-Plant
Variability 178
Table 4-71. Select SVOC 60 °C Emission Factor Measurement Results for Individual Location Tire
Crumb Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing
Within-Field Variability 179
Table 4-72. Within- and Between-Recycling Plant or Field Variability for Select SVOC 25 °C
Emission Factor Analysis Results for Tire Crumb Rubber Collected from Tire Recycling
Plants and Tire Crumb Rubber Infill Collected from Synthetic Turf Fields 181
Table 4-73. Within- and Between-Recycling Plant or Field Variability for Select SVOC 60 °C
Emission Factor Analysis Results for Tire Crumb Rubber Collected from Tire Recycling
Plants 182
Table 4-74. Comparison of Select Metals Analyzed in Tire Crumb Rubber Infill Collected at
Outdoor and Indoor Synthetic Turf Fields 183
Table 4-75. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber
Infill Collected at Outdoor and Indoor Synthetic Turf Fields 185
Table 4-76. Comparison of Select SVOC Extracts Non-quantitative Analysis Results by LC/TOFMS
for Tire Crumb Rubber Infill Collected at Outdoor and Indoor Synthetic Turf Fields 185
Table 4-77. Comparison of Select VOC Emission Factors for Tire Crumb Rubber Infill Collected at
Outdoor and Indoor Synthetic Turf Fields 189
Table 4-78. Comparison of Select SVOC Emission Factors for Tire Crumb Rubber Infill Collected
at Outdoor and Indoor Synthetic Turf Fields 191
Table 4-79. Comparison of Selected Metals in Tire Crumb Rubber Infill Collected from Synthetic
Turf Fields in Three Field Installation Age Groups 194
Table 4-80. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber
Infill Collected from Synthetic Turf Fields in Three Field Installation Age Groups 195
Table 4-81. Comparison of Select SVOC Extracts with Non-quantitative LC/TOFMS Analysis for
Tire Crumb Rubber Infill Collected from Synthetic Turf Fields in Three Field Installation
Age Groups 196
Table 4-82. Comparison of Select VOC Emission Factors in Tire Crumb Rubber Infill Collected
from Synthetic Turf Fields in Three Field Installation Age Groups 200
Table 4-83. Comparison of Select SVOC Emission Factors in Tire Crumb Rubber Infill Collected
from Synthetic Turf Fields in Three Field Installation Age Groups 202
Table 4-84. Comparison of Select Metals in Tire Crumb Rubber Infill Collected from Outdoor
Synthetic Turf Fields in Three Field Installation Age Groups 205
Table 4-85. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber
Infill Collected from Outdoor Synthetic Turf Fields in Three Field Installation Age
Groups 207
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Table 4-86. Comparison of Select SVOC Extracts with Non-quantitative LC/TOFMS Analysis for
Tire Crumb Rubber Infill Collected from Outdoor Synthetic Turf Fields in Three Field
Installation Age Groups 207
Table 4-87. Comparison of Select VOC Emission Factors in Tire Crumb Rubber Infill Collected
from Outdoor Synthetic Turf Fields in Three Field Installation Age Groups 211
Table 4-88. Comparison of Select SVOC Emission Factors in Tire Crumb Rubber Infill Collected
from Outdoor Synthetic Turf Fields in Three Field Installation Age Groups 213
Table 4-89. Estimated Time Decay Half-lives and Chemical Properties for Selected Extractable
SVOCs in Tire Crumb Rubber Infill Samples Collected at Outdoor Fields with a Range
of Ages 218
Table 4-90. Comparison of Select Metals in Tire Crumb Rubber Infill Collected at Synthetic Turf
Fields in Four U.S. Census Regions 220
Table 4-91. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber
Infill Collected at Synthetic Turf Fields in Four U.S. Census Regions 222
Table 4-92. Comparison of Select SVOC Extracts with Non-quantitative LC/TOFMS Analysis for
Tire Crumb Rubber Infill Collected at Synthetic Turf Fields in Four U.S. Census
Regions 223
Table 4-93. Comparison of Select VOC Emission Factors for Tire Crumb Rubber Infill Collected at
Synthetic Turf Fields in Four U.S. Census Regions 228
Table 4-94. Comparison of Select SVOC Emission Factors for Tire Crumb Rubber Infill Collected at
Synthetic Turf Fields in Four U.S. Census Regions 230
Table 4-95. P-values for Final Linear Models of Select Measurement Results for Three Synthetic
Turf Field Characteristics - Outdoor vs. Indoor Field, Field Installation Age Category,
and U.S. Census Region Field Location 232
Table 4-96. Tentative Suspect Screening Chemical Identifications Through Positive Ionization
LC/TOFMS Analysis of Tire Crumb Rubber Solvent Extracts 235
Table 4-97. Tentative Suspect Screening Chemical Identifications Through Negative Ionization
LC/TOFMS Analysis of Tire Crumb Rubber Solvent Extracts 236
Table 4-98. Non-targeted Analysis Frequency Summaries for Highly Tentative Chemical
Identifications 241
Table 4-99. Detection Rates (%) of 19 Metals in Tire Crumb Sample Extracts (Stratified by Artificial
Biofluid) 242
Table 4-100. Summary Statistics of Measured Metal Levels in Artificial Biofluid Extracts of Tire
Crumb Samples, Stratified by Artificial Biofluid 244
Table 4-101. Measured Metal Levels in Artificial Biofluid Extracts of Tire Crumb Samples,
Stratified by Recycling Plant vs. Synthetic Turf Field Samples 247
Table 4-102. Summary Descriptive Statistics of Calculated In Vitro Percent Bioaccessibility Results
for Metals in Tire Crumb Samples that are Bioaccessible in Three Artificial Biofluids 250
Table 4-103. In Vitro Percent Bioaccessibility Results in Three Artificial Biofluids, Stratified by
Recycling Plant vs. Synthetic Turf Field Samples 252
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Table 4-104. Reported In Vitro Bioaccessible Metal Concentrations in Artificial Biofluid Extracts
for Tire Crumb Samples Collected on Synthetic Turf Fields 254
Table 4-105. Reported In Vitro Bioaccessible Metal Concentrations in Artificial Biofluid Extracts for
New/Unused Tire Crumb Samples 257
Table 4-106. Reported In Vitro Percent Bioaccessibility of Metals in Artificial Biofluids, Stratified
by Synthetic Turf Field Samples from this Study vs. the Literature 259
Table 4-107. Summary of the Concentrations of the Targeted Microbial Genes Measured in Samples
from Synthetic Turf Fields 261
Table 4-108. Summary of the Variability in Targeted Microbial Gene Quantities Measured in
Replicate Samples from Each Field 261
Table 4-109. Mean Quantities of Targeted Microbial Genes in Outdoor and Indoor Synthetic Turf
Fields 261
Table 4-110. Mean Quantities of Targeted Microbial Genes in Synthetic Turf Field Samples, by
Installation Age Group 263
Table 4-111. Mean Quantities of Targeted Microbial Genes in Synthetic Turf Field Samples, by U.S.
Geographical Regions 264
Table 4-112. Mean Quantities of Targeted Microbial Genes in Synthetic Turf Fields, with and
without Biocide Application 265
Table 4-113. Summary of Total 16S rRNA Sequence Read Counts Obtained from the Non-targeted
Microbial Community Analysis of Synthetic Turf Fields 267
Table 5-1. Information Sources Used to Compile Reference Toxicity Information 269
Table 5-2. Summary of LRGA Chemical Constituents51 with Available Toxicity Data 271
Table 5-3. Summary of Target Chemical Constituents with Available Toxicity Data 272
Table 5-4. Chemical-specific Toxicity Data for Select Metals 273
Table 5-5. Chemical-specific Toxicity Data for Select VOCs and SVOCs 276
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Acronyms and Abbreviations
ACGM
ACH
AIC
ANOVA
APHC
API
ASTM
AT SDR
BLP
BSD
BTEX
°C
CalEPA
CalOSHA
CAS
CDC
CFU
CICAD
cm
coc
CP
CPSC
CVAA
DAD
DBA + ICDP
ddPCR
DNA
DNPH
dNTP
dsDNA
DSSTox
EI
EOHSI
EPA
EPMA
ESI
eV
FLM
FRAP
g
GC/MS
American Conference of Governmental Industrial Hygienists
Air change per hour
Akaike information criterion
Analysis of variance
U.S. Army Public Health Center
Analytical profile index
American Society for Testing and Materials
Agency for Toxic Substances and Disease Registry
Bacteria-like particles
Backscattered electron detector
Benzene, toluene, ethylbenzene, xylenes
Degrees Celsius
California Environmental Protection Agency
California Division of Occupational Safety and Health
Chemical Abstracts Service
Centers for Disease Control and Prevention
Colony forming units
Concise International Chemical Assessment Documents
Centimeter
Chain of custody
Carcinogenic potency
Consumer Product Safety Commission
Cold vapor atomic absorption
Diode array detector
Sum of Dibenz[a,h]anthracene and Indeno(l,2,3-cd)pyrene
Droplet digital polymerase chain reaction
Deoxyribonucleic acid
Dinitrophenyl hydrazine
Deoxyribonucleotide triphosphate
Double-stranded DNA
EPA's Distributed Structure-Searchable Toxicity Database
Electron impact
Environmental and Occupational Health Sciences Institute
U.S. Environmental Protection Agency
Electron probe microanalysis
Electrospray ionization
Electronvolt
Fence line monitor
Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields and
Playgrounds
Gram
Gas chromatography/mass spectrometry
xxvii
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GC/TOFMS Gas chromatography/time-of-flight mass spectrometry
GS/MS/MS Gas chromatography/tandem mass spectrometry
h Hour
HDPE High density polyethylene
HEAST Health Effects Assessment Summary Table
HPLC High performance liquid chromatography
HR-ICPMS High resolution magnetic sector inductively coupled plasma mass spectrometer
HS High-sensitivity
Hz Hertz
IAC Internal amplification control
IARC International Agency for Research on Cancer
ICP/AES Inductively coupled plasma-atomic emission spectrometry
ICP/MS Inductively coupled plasma/mass spectrometry
ICR Information Collection Request
in Inch
10 AA Immediate Office of the Assistant Administrator
IPCS WHO International Programme on Chemical Safety
IRB Institutional Review Board
IRIS U.S. EPA Integrated Risk Information System
IS Internal standard
ISO International Standards Organization
IUR Inhalation unit risk
JTI Jacobs Technology, Inc.
kg Kilogram
kV Kilovolt
L Liter
LC/MS Liquid chromatography/mass spectrometry
LC/TOFMS Liquid chromatography/time-of-flight mass spectrometry
LOD Limit of detection
LOQ Limit of quantitation
lpm Liters per minute
LRGA Literature Review and Data Gaps Analysis
mg Milligram
m/z Mass-to-charge ratio
MADL Maximum allowable dose levels
Max Maximum
mecA Gene for methicillin resistance
MFE Molecular feature extraction
min Minute
Min Minimum
mL Milliliter
mm Millimeter
mM Millimolar
Mohm Megaohm
mol Mole
MQL Method quantifiable limit
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MRL
Minimum risk level
MRM
Multiple reaction monitoring
MRSA
Methicillin-resistant Staphylococcus aureus
MSD
Mass selective detector
N/A
Not applicable/Not available
NAM
New approach methods
NCCT
U.S. EPA National Center for Computational Toxicology
NCEA
U.S. EPA National Center for Environmental Assessment
NERL
U.S. EPA National Exposure Research Laboratory
ng
Nanogram
NHEERL
U.S. EPA National Health and Environmental Effects Research Laboratory
NIEHS
National Institutes of Environmental Health Sciences
NIOSH
National Institute for Occupational Safety and Health
NIST
National Institute of Standards and Technology
nM
Nanomolar
NR
Not reported
NRMRL
U.S. EPA National Risk Management Research Laboratory
NSRL
No significant risk level
ns
Nanosecond
NTP
National Toxicology Program
OCHP
U.S. EPA Office of Children's Health Protection
OEM
Original equipment manufacturer
OEHHA
California Office of Environmental Health Hazard Assessment
OLEM
U.S. EPA Office of Land and Emergency Management
OMB
U.S. Office of Management and Budget
ORAU
Oak Ridge Associated Universities
ORCR
U.S. EPA Office of Resource Conservation and Recovery
ORD
U.S. EPA Office of Research and Development
ORISE
Oak Ridge Institute for Science and Education
OSF
Oral slope factor
OSHA
Occupational Safety and Health Administration
OSP
U.S. EPA Office of Science Policy
OTU
Operational taxonomic unit
PAH
Polyaromatic hydrocarbon
PCDL
Personal compound database list
PCR
Polymerase chain reaction
PEL
Permissible exposure limit
pM
Picomolar
ppbv
Parts per billion by volume
ppm
Parts per million
PPRTV
Provisional peer-reviewed toxicity value
PSA
Particle size analysis
psi
Pounds per square inch
PUF
Polyurethane foam
QA
Quality assurance
QC
Quality control
REL
Recommended exposure limit/Reference exposure levels
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RF Radio frequency
RfC Reference concentration
RfD Reference dose
RH Relative humidity
RIVM Netherlands National Institute for Public Health and the Environment
RNA Ribonucleic acid
RPM Revolutions per minute
rRNA Ribosomal ribonucleic acid
%RSD Percent relative standard deviation
s Second
SBR Styrene-butadiene rubber
SD Standard deviation
SEE Senior Environmental Employee
SEM Scanning electron microscopy
SF Slope factor
SOP Standard operating procedure
SSC Student Services Contractor
STEL Short term exposure limit
Suml5PAH Sum of 15 of the 16 EPA 'priority' PAHs
SumBTEX Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
SVOC Semi-volatile organic compound
S-W Shapiro-Wilk
TCR Tire crumb rubber
TD Thermal desorption
TIC Total ion current
TIFF Tagged image file format
TLV Threshold limit value
TOFMS Time-of-flight mass spectrometry
TPE Thermoplastic elastomers
TSA Technical systems audit
TSP Total suspended solids
TWA Time weighted average
jam Micrometer
|iL Microliter
UR Unit risk
U.S. United States of America
U.S. EPA United States Environmental Protection Agency
UV Ultraviolet spectrometry
VID Video identification number
V Volt
VOC Volatile organic compound
W Watt
WHO World Health Organization
XRF X-ray fluorescence spectrometry
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Executive Summary
The goal of the research under the Federal Research Action Plan on Recycled Tire Crumb Used on
Playing Fields and Playgrounds (FRAP) is to characterize potential human exposures to the
substances associated with recycled tire crumb rubber used on synthetic turffields. Results of the
effort are being reported in two parts. Part 1 (this document) communicates the research objectives,
methods, results andfindings for the tire crumb rubber characterization research (i. e., what is in the
material). Part 2, to be released at a later date, will characterize potential human exposures to the
chemicals found in the tire crumb rubber material while using synthetic turffields. Neither Part 1
nor Part 2 of this study, separately or combined, will constitute an assessment of the risks associated
with playing on synthetic turffields with recycled tire crumb rubber infill. The results of the research
described in both Part 1 and Part 2 of the final report can be used to inform future risk assessments.
In the United States, synthetic turf fields are used at
municipal and county parks; schools, colleges, and
universities; professional sports stadiums and practice fields;
and military installations and are designed to simulate the
experience of practicing and playing on grass fields.1 First
introduced in the 1960s, synthetic turf fields have evolved
over time from first-generation systems made of tightly
curled nylon fibers to third-generation systems typically made
of polyethylene yarn fibers. These third-generation systems
typically use small pieces of recycled tires, referred to as
"recycled tire crumb rubber" (or simply "tire crumb rubber"),
to fill the space between the polyethylene yarn fibers. The
recycled tire crumb rubber (sometimes mixed with sand or
other raw materials) is added for ballast, support for the
synthetic grass blades, and as cushioning for field users.
Third-generation synthetic turf field systems are widely used
today. There are between 12,000 and 13,000 synthetic turf
fields in the United States, with 1,200 - 1,500 new
installations each year. It is estimated that millions of people
use and/or work at these fields.
Recently, parents, athletes, schools and communities have
concerns about the use of recycled tire crumb rubber on synthetic turf fields. To help address these
concerns, the Centers for Disease Control and Prevention/Agency for Toxic Substances and Disease
Registry (CDC/ATSDR) and the U.S. Environmental Protection Agency (EPA), in collaboration with
the Consumer Product Safety Commission (CPSC), launched a multi-agency research effort in
February 2016.
Key Research Activities
Discussed in Part 1
• Collect tire crumb rubber samples
from tire recycling facilities and tire
crumb rubber infill samples from
synthetic turf playing fields.
• Collect information on synthetic turf
field use and maintenance.
• Characterize the chemical, physical,
and microbiological makeup of
recycled tire crumb rubber.
• Characterize organic chemical
emissions and bioaccessibility of
metals associated with tire crumb
rubber.
• Collate toxicological reference
information on chemical constituents
associated with tire crumb rubber.
1 More information on the intended uses of synthetic turf can be found at:
https://www.SYntheticturfcouncil.org/page/About Synthetic Turf.
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This multi-agency research effort, known as the Federal Research Action Plan on Recycled Tire Crumb
Used on Playing Fields and Playgrounds (FRAP)2, is focused on assessing potential human exposure,
which includes conducting research activities to characterize the chemicals associated with recycled tire
crumb rubber and to identify the ways in which people may be exposed to those chemicals based on
their activities on synthetic turf fields. Also, the FRAP includes characterizing emissions and
bioaccessibility to differentiate what is present in the recycled tire crumb rubber from what people may
actually be exposed to from recycled tire crumb rubber.
The research laid out in the FRAP is not intended to be a risk assessment. Like other studies, this
research has limitations, and risks cannot be inferred from the information and conclusions found in this
study. Prior to initiating the FRAP, most studies examining these potential risks have been considered
inconclusive or otherwise incomplete. Based upon available literature, this research effort represents the
largest tire crumb rubber study conducted in the United States. The information and results from the
effort will fill specific data gaps about the potential for human exposure to chemical constituents
associated with recycled tire crumb rubber used in synthetic turf fields.
A status report was previously released describing FRAP
activities as of December 2016 (EPA/600/R-16/364,
available at: http://www.epa.gov/TireCrumb). The status
report included a summary of stakeholder outreach, an
overview of the tire crumb rubber manufacturing industry,
progress on the research activities, and the final peer-
reviewed literature review/gaps analysis (LRGA) white
paper. The results of the research activities under the
FRAP are being documented in two parts. Part 1
documents the tire crumb characterization activities and
results. Part 2 will document the results from the exposure
characterization research and will be released along with a
planned biomonitoring study to be conducted by CDC/
ATSDR. Part 2 will also include a discussion of potential
follow-up activities that could provide additional insights
into potential exposures to recycled tire crumb rubber
used on synthetic turf fields.
Literature Review/Gaps Analysis
(LRGA)
• Summary of the available literature on
tire crumb rubber and its associated
exposure information.
• Multiple types of information on
constituents, releases, environmental
presence, and exposures were
identified, along with important data
gaps.
• Information was collated, and a final
white paper was made available
(Appendix C of this part of the report).
2 The multi-agency research effort, called the Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields
and Playgrounds (FRAP), was launched in February 2016. Prior to initiating the study, federal researchers developed a
research protocol. Collections Related to Synthetic Turf Fields with Crumb Rubber Infill, which describes the study's
objectives, research design, methods, data analysis techniques and quality assurance/quality control (QA/QC) measures.
These documents are available at: http://www.epa.gov/TireCrumb. CPSC is conducting the work on playgrounds and results
from that effort will be reported separately. While artificial turf is also used at residences, that turf does not typically include
tire crumb rubber; as a result, the use of artificial turf at residences is not part of the FRAP study.
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This Executive Summary provides a review of the tire crumb rubber research (Part 1 of the study).
Section 1 of this report provides introductory information; Section 2 provides a more complete technical
summary of these activities and the study's key findings; Sections 3 and 4 describe the methods and
contain detailed results for the tire crumb rubber characterization activities, with result tables focusing
on select chemicals of interest; and Section 5 provides information on the availability of toxicity
reference information for the chemicals associated with tire crumb rubber. Complete result tables are
provided in the Appendices (Volume 2).
Tire Crumb Rubber Characterization
Tire crumb rubber samples were collected from nine tire
recycling facilities, and tire crumb rubber infill material was
collected from 40 synthetic turf fields located across the
United States. The fields included a range of field types
(indoor versus outdoor), field ages and geographic locations.
Laboratory analyses were conducted to measure the physical,
chemical and microbiological characteristics of the tire crumb
rubber material (Figure ES-1). Results of these analyses
provided information about the number and types of
chemicals associated with recycled tire crumb rubber, the
amount of chemicals released into the air and into simulated
biological fluids, and the range and variability of these
parameters. As expected, the research team found a range of
metals, semivolatile organic compounds (SVOCs), volatile
organic compounds (VOCs) and bacteria in and on tire crumb
rubber infill material. Many of the chemicals measured in this
study have been identified as present in recycled tire crumb
rubber in previous studies. Other VOC and SVOC chemicals
have been tentatively identified in this study but have not been
confirmed. Additional detail on these analyses can be found in
Section 4.12 of this document.
Recycled Tire Crumb Rubber
Characterization
• As expected, a range of metals,
semivolatile organic compounds
(SVOCs), volatile organic compounds
(VOCs) and bacteria were measured
in and on recycled tire crumb rubber
infill.
• Many chemicals were found at similar
concentrations in other studies of
recycled tire crumb rubber, where
comparable data are available.
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Tire Crumb Rubber Sample Collection
Tire Crumb Rubber Infill Samples
from 25 Outdoor Synth eticTurf
Fields
Tire Crumb Rubber Infill Samples
from 15 indoor Synthetic Turf
Fields
Tire Crumh Rubber Samples
from 3 Tire Recycling
Fac li'ies
Direct Chemical Extraction and Analysis and Particle Characterization
Particle Size
Characterization
67 Samples, 469 Size Fractions
Metals ftod Digestion
Analysis neFc ills
SVOC S
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Differences Among Recycled
Tire Crumb Rubber Samples
from Recycling Plants and
Synthetic Turf Fields
Chemicals specifically targeted for analysis in the tire crumb
characterization research included 21 metals, 49 SVOCs and
31 VOCs. Most of the targeted metals and SVOCs, and
several of the VOCs were found to be associated with
recycled tire crumb rubber infill collected at fields across the
United States. Average concentrations for the target analytes
varied widely, by up to four orders of magnitudes for metals
and three orders of magnitudes for polycyclic aromatic
hydrocarbons (PAHs). Additional SVOCs including
phthalates, thiazoles and other compounds associated with tire
rubber were identified in infill samples as well. In general,
where comparable data are available, most target analyte
concentrations measured in this study were similar to
concentrations found in previous studies of recycled tire
crumb rubber. For the microbial analysis, all tire crumb
rubber samples collected from the 40 synthetic turf fields
tested positive for a universal bacterial gene (16s rRNA). This
is not surprising, as bacteria are present in soil and on surfaces
in indoor environments. The research team observed higher
concentrations of total bacteria in outdoor fields relative to
indoor fields, but a gene commonly associated with the
human skin microbiome (i.e., Staphylococcus aureus) was
detected more often in indoor fields than outdoor fields.
The presence of a substance does not directly equate with
human exposure. While there are many chemicals associated
with recycled tire crumb rubber, our laboratory experiments
suggest that the amount of chemicals available for exposure
through release into the air and simulated biological fluids is
relatively low. Air emissions tests were performed at both
25 °C (77 °F) and 60 °C (140 °F), temperatures chosen to represent moderate and high-end field
temperature conditions, respectively. For most VOC and SVOC target chemicals, air emissions were
low at 25 °C and in many cases, not measurable above the detection limit or above background levels.
At 60 °C, higher emissions were measured for some, but not all, VOCs and SVOCs. Overall, methyl
isobutyl ketone and benzothiazole had the highest emission factors among the target analytes in this
study.
Bioaccessibility tests of 19 metals were conducted on the tire crumb rubber samples using three types of
simulated biological fluids (gastric fluid, saliva and sweat plus sebum3). Only small fractions of metals
were released into simulated biological fluids. For all metals, the mean bioaccessibility values averaged
about 3% in gastric fluid and less than 1% in saliva and sweat plus sebum. These results fill important
knowledge gaps about potential bioavailability of chemicals associated with recycled tire crumb rubber.
Based on these results, a default to 100% bioaccessibility should not be used when assessing potential
exposures to most metals in tire crumb rubber.
• When comparing tire crumb rubber
from recycling plants and synthetic
turf fields:
- Concentrations of most metals
were comparable between fields
and recycling plants.
- Many organic chemical
concentrations and emissions
were higher with tire crumb
obtained directly from a recycling
plant.
- A few chemicals had higher
average concentrations in
materials from fields.
• Levels of many organic chemicals were
higher for indoor fields compared to
outdoor fields, suggesting potential
exposures may be greater at indoor
fields.
• Levels of organic chemicals were often
lower in older outdoor fields.
3 Sebum is the oil-like substance produced by the sebaceous glands in the skin.
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Results from this tire crumb rubber characterization research
also suggest that concentrations of many organic chemicals
found in tire crumb rubber infill material vary with synthetic
turf field age and type (i.e., indoor versus outdoor). In
general, concentrations of many organic chemicals appeared
to decrease with increasing field age. These results suggest
that vaporization, weathering and/or other removal
mechanisms may lead to lower concentrations of many
organic chemicals over time, particularly for outdoor fields.
However, since longitudinal measurements at individual
fields were outside the scope of the current activities, it
cannot be ruled out that some differences in chemical
concentrations across fields of different ages are a result of
differences in the initial chemical composition of the tire
crumb rubber. Levels of many organic chemicals also tended
to be higher for indoor fields compared to outdoor fields,
suggesting that exposures may be greater at indoor synthetic
turf fields. Additional research is needed to determine
whether indoor field users experience higher exposures than
those using outdoor fields as a result of these differences.
Univariate statistical analysis did not, in general, show significant differences for fields across the four
U.S. census regions, but multivariate analysis results suggest that differences across regions cannot be
completely ruled out.
The same target analytes were measured in tire crumb rubber collected at tire recycling plants and
synthetic turf fields. The concentrations of most metals in both materials were comparable. Many
organic chemicals had higher concentrations in, and emissions from, tire crumb rubber collected at
recycling plants compared to tire crumb rubber infill collected at synthetic turf fields. A few chemicals
[e.g., lead and bis(2-ethylhexyl) phthalate] had higher average concentrations in infill samples from
synthetic turf fields than in tire crumb rubber samples collected at recycling plants. Additional research
may be needed to better understand whether there are contributions of some chemicals at fields from
sources other than the recycled tire crumb rubber. Emission measurements suggested that several VOCs,
such as benzene and toluene, may be present primarily at the surface of the rubber particles; other
VOCs, such as methyl isobutyl ketone and benzothiazole, appear more likely to be intrinsic to the tire
crumb rubber material.
Organic Chemical Emissions
and Metals Bioaccessibility
Emissions of most SVOCs and many
VOCs were low when tested at 25 °C,
while emissions were higher for
some, but not all at 60 °C.
The amount of metals released into
simulated biological fluids was low,
on average about 3% in gastric fluid
and less than 1% in saliva and sweat
plus sebum.
The emissions and bioaccessibility
measurements suggest that
exposures to most chemicals may be
relatively low but exposure
measurements are being conducted
to confirm these results.
Toxicity Reference Information on
Constituents of Recycled
Tire Crumb Rubber
Toxicity Reference Information
Toxicological reference information was compiled for
potential tire crumb rubber chemical constituents. One or
more toxicity reference values was identified for 167 (about
47%) of the 355 chemical compounds potentially associated
with recycled tire crumb rubber as reported in the LRGA.
When narrowing this down from the LRGA's list of 355 to its
subset of target analytes in this study (95), one or more
toxicity reference values is available for 78 of those analytes
(about 82%). It is important to recognize that some of these
target analytes were not found, or were not consistently
found, in tire crumb rubber in this study.
• Toxicity reference values are
available for some of the potential
chemicals associated with tire crumb
rubber and for most of those in the
target analyte list of this study.
• Not all target analytes were
consistently found in the samples.
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Conclusions
This part of the report communicates the research objectives,
methods, results and findings for the tire crumb rubber
characterization (what is in the material) and fills specific data
gaps about what chemicals are found in recycled tire crumb
rubber used on synthetic turf fields.
As expected, a range of chemicals was found in the recycled
tire crumb rubber, including metals and organic chemicals.
Where comparative data are available concentrations of most
metal and organic chemicals found in tire crumb rubber were
found to be similar when comparing this study to previous
studies. Further, the emissions of many organic chemicals into
air were typically found to be below detection limits or test
chamber background, and releases of metals into simulated
biological fluids were very low (mean bioaccessibility values
averaged about 3% in gastric fluid and less than 1% in saliva
and sweat plus sebum). Together, these findings support the
premise that while many chemicals are present in the recycled
tire crumb rubber, exposure may be limited based on what is
released into air or biological fluids.
Toxicity reference information was available for most of the target analytes. This information will
contribute to the public's understanding of the potential hazards that may exist from chemicals
associated with recycled tire crumb rubber.
Risk is a function of both hazard (toxicity) and exposure; therefore, understanding what is present in the
material (Part 1) and how individuals are potentially exposed (Part 2 to be released at a future date) is
critical to understanding potential risk. It is important to note that the study activities completed as part
of this multi-agency research effort were not designed, and are not sufficient by themselves, to directly
answer questions about potential health risks. Other studies may aid in this regard.4 Overall, we
anticipate that the results from this multi-agency research effort will be useful to the public and
interested stakeholders for understanding the potential for human exposure to chemicals associated with
recycled tire crumb rubber infill material used on synthetic turf fields.
What We Learned
• As expected, a range of metals,
organic chemicals, and bacteria was
found to be associated with recycled
tire crumb rubber.
• Results are comparable to other
studies characterizing tire crumb
where available.
• While many chemicals are present in
the recycled tire crumb rubber,
exposure may be limited based on
what is released into air or biological
fluids.
4 Other research studies in the United States and Europe will also provide data to better understand whether there are human
health risks from playing on synthetic turf fields containing recycled tire crumb rubber. For example, the California Office of
Enviromnental Health Hazard Assessment (OEHHA) will provide tire crumb rubber characterization data for additional
fields in California. They will also characterize additional synthetic turf field component materials and particles in the air
above the synthetic fields as a result of simulated activities and measure the bioaccessibility of inorganic and organic
chemicals from tire crumb rubber. The National Toxicology Program (NTP) is conducting short-term toxicity studies on the
recycled tire crumb rubber material itself not specific chemical constituents found in the material.
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1.0 Introduction
1.1 Background
Synthetic turf systems have been installed in the United States since the 1960s. Currently, there are between
12,000 and 13,000 synthetic turf sports fields in the United States, with approximately 1,200 to 1,500
new installations each year (Synthetic Turf Council et al., 2016). These fields, which are designed to
simulate the experience of practicing and playing on grass fields, are installed at a variety of venues,
including parks, schools, colleges, stadiums and practice fields, and are used by a wide variety of
people, such as professional, college and youth athletes; coaches; referees; and recreational users of all
ages. It is estimated that 95% of synthetic turf fields utilize recycled rubber infill exclusively or in
mixture with sand or alternative infills (Synthetic Turf Council et al., 2016). Infill is added for ballast,
support for the synthetic grass blades and as cushioning for field users. The recycled rubber infill
material used on these fields is produced from waste automobile and truck tires, which are reprocessed
using either an ambient or cryogenic method to create "crumb"-sized material, with reported
approximate diameters ranging from 1 to 6 mm (Lim & Walker, 2009). In addition to its use in synthetic
turf, recycled tire material is increasingly being used for playground surfaces in the Unites States.
Some in the public have raised concerns about the potential for human exposure to chemicals associated
with the tire crumb rubber used on synthetic turf fields and playgrounds. To date, most studies
examining these potential risks have been considered inconclusive or otherwise incomplete. In most
studies of potential tire crumb rubber-related chemicals only a limited number of chemicals were
measured, and there are gaps in exposure information and measurement data for dermal and ingestion
pathways. In addition, no single study has evaluated large numbers of fields or people to
comprehensively characterize potential exposures to tire crumb rubber infill material. Three recent
studies examined potential relationships between synthetic turf fields and cancer; none reported
evidence supporting such a relationship (WDOH, 2017; RIVM, 2017; Bleyer & Keegan, 2018).
Tires are manufactured with a range of materials, including rubber and elastomers; reinforcement filler
material; curatives including vulcanizing agents, activators and accelerators; antioxidants and
antiozonants; inhibitors and retarders; extender oils and softeners; phenolic resins, plasticizers; metal
wire; polyester or nylon fabrics; and bonding agents (NHTSA, 2006; Chem Risk Inc. & DIK Inc., 2008;
Cheng et al., 2014; Dick & Rader, 2014). Chemicals of concern range from polycyclic aromatic
hydrocarbons (PAHs) in carbon black to zinc oxide (ZnO), which is used as a vulcanizing agent and
may contain trace amounts of lead and cadmium. Chemicals in many other classes may be used in tires
as well, including sulphenamides, guanidines, thiazoles, thiurams, dithiocarbamates, sulfur donors,
phenolics, phenylenediamines, and other chemicals (Chem Risk Inc. & DIK Inc., 2008). There is limited
information available to assess whether some of these chemicals may carry impurities or byproducts or
whether they may undergo chemical transformation over time. In addition to chemicals used in their
production, tires may also pick up and absorb chemicals over their lifetime of use, and once installed on
a field, tire crumb rubber may serve as a sorbent for chemicals in the air and in dust that falls onto the
field. For example, one laboratory reported irreversible adsorption of volatile organic compound (VOC)
and semivolatile organic compound (SVOC) analytes spiked onto tire crumb rubber (Lim & Walker,
2009). Alternatively, the tire crumb rubber may also emit VOC and SVOC species into the air,
especially at higher outdoor temperatures (Marsili et al., 2014; CAES, 2010).
Users of synthetic turf fields with tire crumb rubber infill can potentially be exposed to these chemicals
in a variety of ways, including while breathing (i.e., inhalation exposure), when contacting the material
with their skin (i.e., dermal exposure), and/or by ingesting the material (i.e., ingestion exposure).
1
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Concerns have been raised about the potential adverse health effects of these exposures. In addition to
the potential for chemical exposures, concerns have been raised about the potential for exposure to
microbial pathogens at synthetic turf fields. For example, methicillin-resistant Staphylococcus aureus
(MRS A) has caused outbreaks among athletic teams, and artificial turf has been implicated as a fomite
in transmission of MRSA among college athletes (Begier et al., 2004). In general, very few studies have
been conducted regarding the potential for microbial pathogen exposures at synthetic turf fields, and few
potential pathogens have been investigated.
1.2 The Federal Research Action Plan
In light of the data gaps and concerns raised about the safety of recycled tire crumb rubber used in
playing field and playground surfaces in the United States, the U.S. Environmental Protection Agency
(EPA), Centers for Disease Control and Prevention/Agency for Toxic Substances and Disease Registry
(CDC/ATSDR), and Consumer Product Safety Commission (CPSC) released a Federal Research Action
Plan on Recycled Tire Crumb Used on Playing Fields and Playgrounds in F ebruary 2016 (U. S. EPA,
CDC/ATSDR, & CPSC, 2016a). This coordinated federal research action plan (FRAP) includes
outreach to key stakeholders, among its many activities, and has these high-level research objectives:
• Determine key knowledge gaps related to chemical characterization, exposure, human health
hazards.
• Identify and characterize chemical compounds found in tire crumb used in artificial turf fields
and playgrounds.
• Characterize exposures, or how people are exposed to these chemical compounds based on their
activities on the fields.
• Identify follow-up activities that could be conducted to provide additional insights about
potential risks.
The overall purpose of this multi-agency research action plan is to study the potential for human
exposure resulting from the use of tire crumb rubber in playing fields and playgrounds, and in doing so,
provide important information needed for any follow-up evaluation of risk that might be performed.
1.3 Scope and Objectives of EPA, CDC/ATSDR and CPSC Activities
The FRAP defines the scope and agency leads for each of the research efforts, including:
• Stakeholder Outreach (EPA, CDC/ATSDR and CPSC),
• Literature Review/Gaps Analysis (EPA, CDC/ATSDR and CPSC),
• Tire Crumb Characterization Research - Synthetic Turf Fields (EPA and CDC/ATSDR),
• Exposure Characterization Research - Synthetic Turf Fields (EPA and CDC/ATSDR), and
• Playgrounds Study (CPSC).
To support elements of the FRAP, the Agencies developed a research protocol titled, Collections
Related to Synthetic Turf Fields with Crumb Rubber Infill (U.S. EPA & CDC/ATSDR, 2016), which
describes the literature review and gaps analysis and details the research design for characterizing tire
crumb rubber and human exposure associated with synthetic turf fields. The research protocol does not
include tire crumb rubber characterization and exposure characterization research performed for
playgrounds; the CPSC is independently developing and implementing research plans for playgrounds.
The research protocol received independent external peer review, and the information collection
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components of the protocol received review and public comment through the Office of Management and
Budget (OMB) Information Collection Request (ICR) process, as well as review and approval by the
CDC Institutional Review Board (IRB).
This report summarizes research results from EPA and CDC/ATSDR efforts to characterize tire crumb
rubber. It also includes a summary of stakeholder outreach and the literature review and knowledge gaps
assessment conducted by all three agencies. The CPSC efforts to characterize exposures associated with
playgrounds (CPSC 2018a; CPSC 2018b) are not described in this report. Research results from the
exposure characterization research activities will be reported separately.
1.3.1 Outreach to Key Stakeholders
The stakeholder outreach efforts conducted as part of the FRAP had two main objectives: (1) gather and
share information that may be used to inform research efforts, and (2) inform the public, researchers and
research organizations, industry, government organizations and non-profit organizations about the
FRAP, including research progress updates and results.
1.3.1.1 Gather and Share Information
EPA, CDC/ATSDR and CPSC gathered relevant information from stakeholders and shared information
as the activities under the FRAP progressed. The information was gathered and shared by convening
discussions and requesting feedback on components of the research. Information gathering and sharing
activities included:
• Field users providing first-hand perspectives on potential exposures;
• Government agencies regularly meeting to discuss the federal research, share relevant
information from state-level and international studies, request support, and identify current best
practices for minimizing exposures;
• Industry representatives sharing information to help researchers better understand the
manufacturing process and use parameters for recycled tire crumb used in synthetic turf fields
and for recycled tire-derived playground surface materials; and
• The public providing comment on the information collection components of the FRAP, including
the plans for collecting tire crumb samples from fields and manufacturing facilities, and the
exposure characterization study.
Agency researchers gathered information from industry, non-governmental organizations, and others to
inform the design and implementation of the research on synthetic turf fields containing tire crumb
rubber infill. This included collecting information on how tires and tire crumb rubber are manufactured
and how synthetic turf fields are constructed, installed, and maintained. From February to September
2016, the study team held meetings with five industry trade associations, three synthetic turf field
companies, two synthetic turf field maintenance professionals, one academic institution, and five non-
profit organizations. EPA, CDC/ATSDR and CPSC scientists toured a total of five tire recycling
facilities in the south, west, and northeast regions of the United States, where they observed different
types of tire crumb rubber processing technologies. Varying degrees of mechanized technologies to
process the tires were observed at the facilities. The tire crumb rubber infilling process was observed on
two field installations. Through these meetings, tours, and observed field installations, the team gathered
information on the following topics:
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• The current state of tire manufacturing and scrap-tire collection and recycling;
• The nature and varieties of processes and machinery used in the processing of scrap tires into tire
crumb rubber;
• Tire manufacturing standards;
• Tire recycling process standards and tire crumb rubber product standards;
• Tire crumb rubber infill product types;
• Storage, packaging and transportation of tire crumb rubber to fields;
• The number and types of synthetic turf fields; and
• Synthetic turf field construction, installation and maintenance practices.
This information was originally summarized in section I. V. A. "Industry Overview" of the Federal
Research Action Plan on Recycled Tire Crumb Used on Playing Fields and Playgrounds: Status Report
released in December 2016 (U.S. EPA, CDC/ATSDR, & CPSC, 2016b) and is included as Appendix A
of this report for completeness.
1.3.1.2 Informing Stakeholders
EPA, CDC/ATSDR and CPSC informed stakeholder groups about the FRAP when it was released,
provided status updates as the research progressed, and will continue to share research findings.
Following the release of the FRAP, the Agencies established a FRAP website (www.epa.gov/tirecrumb)
and hosted a public webinar to provide an overview of the FRAP.
The Agencies provided updates to stakeholders as the research progressed through a number of outreach
activities:
• Regularly updating the FRAP website with links to the FRAP and the Research Protocol, Tire
Crumb Questions and Answers, government websites that provide recommendations for
recreation on fields with tire crumb, and other information.
• Distributing study updates to an e-mail list of about 800 stakeholders.
• Releasing the Status Report in December 2016 summarizing research progress.
• Communicating with other federal, state, and international government organizations involved in
planning or conducting tire crumb research, including California's Office of Environmental
Health Hazard Assessment, the Washington State Department of Health, the National
Toxicology Program at the National Institute of Environmental Health Sciences, the European
Chemicals Agency, and the Netherlands National Institute for Public Health and the
Environment.
• Presenting about the FRAP at conferences and annual meetings which allowed for interactions
with researchers and the academic community, including the International Society of Exposure
Science Annual Meeting, Society of Environmental Toxicology and Chemistry Annual Meeting,
California Tire Conference, and Recycled Rubber Products Technology Conference, and the
American Public Health Association Annual Meeting.
• Responding to public, media and Congressional inquiries about the FRAP.
The agencies will update the FRAP website and continue outreach efforts to share and discuss research
findings from this and future reports. The Agencies also expect to host webinars to provide the public an
overview of research findings as they are released. In addition, the findings will be presented at
conferences, and the three agencies implementing the FRAP, along with other state and international
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governmental organizations with an interest in tire crumb research, expect to continue to convene to
exchange information.
Stakeholder outreach information was originally summarized in the Federal Research Action Plan on
Recycled Tire Crumb Used on Playing Fields and Playgrounds: Status Report released in December
2016 (U.S. EPA, CDC/ATSDR, & CPSC, 2016b) and is included as Appendix B of this report for
completeness.
1.3.2 Data and Knowledge Gap Analysis
EPA, CDC/ATSDR, and CPSC conducted a Literature Review/Gaps Analysis (LRGA) to provide a
summary of the available literature on tire crumb rubber and to identify data gaps characterized in the
literature. The overall goals of the LRGA were to inform the interagency research study and to identify
potential areas for future research. The LRGA did not include critical reviews of the strengths and
weaknesses of each study, but did provide the authors' conclusions regarding their research, where
applicable. The LRGA also did not make any conclusions or recommendations regarding the safety of
recycled tire crumb rubber used in synthetic turf fields and playgrounds.
The LRGA identified 88 references from bibliographic databases, including PubMed, Medline (Ovid®),
Embase (Ovid®), Scopus, Primo (Stephen B. Thacker CDC Library), ProQuest Environmental Science
Collection, Web of Science, ScienceDirect and Google Scholar. Each reviewed reference was
categorized according to 20 general information categories (e.g., study topic, geographic location,
sample type, conditions, populations studied, etc.) and more than 100 subcategories (e.g., for study
topic: site characterization, production process, leaching, off-gassing, microbial analysis, human risk,
etc.). The peer-reviewed white paper summarizing the LRGA results, State-of-Science Literature
Review/Gaps Analysis, White Paper Summary of Results, was originally published in the FRAP Status
Report (U.S. EPA, CDC/ATSDR, & CPSC, 2016b); it is included in its entirety in Appendix C of this
report for completeness.
Several organizations have published important information on this topic since the FRAP LRGA was
completed and published in December 2016. Brief summaries of some of these research efforts and
publications have been included in the introductory information of Appendix C. For example, one
important study was conducted by the Netherlands National Institute for Public Health and the
Environment (RIVM 2017). The RIVM research effort collected tire crumb rubber samples from 100
fields in the Netherlands, measured a select group of chemicals in all or a subset of fields, assessed the
release of select chemicals, estimated exposures, and evaluated potential risks based on exposures to
PAHs in the tire crumb. Federal researchers have had frequent contact with RIVM researchers, and with
the European Chemicals Agency (ECHA), to share information and to better understand the research
studies.
The data and knowledge gaps identified in the LRGA are summarized in Table 1 of Appendix C. The
FRAP research was designed to address many of these gaps, particularly with respect to tire crumb
rubber characterization and exposure characterization. Some of these data gaps are also being addressed
by other research organizations. However, the U.S. federal study is providing information that cannot be
replaced by state and international organizations, and has unique research elements to provide data not
being produced by other research efforts. Important data gaps that the federal study is addressing are
summarized below.
While a number of research studies have examined tire crumb rubber constituents, most U.S. studies
have been relatively small, restricted to a few fields or material sources, and measured a limited number
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of constituents. Few studies have assessed tire crumb rubber directly from recycling plants for
comparison to infill at synthetic turf fields to assess potential changes due to weathering or the potential
for increases in some chemical constituents from external sources. Few studies have compared infill and
exposures at indoor fields to those at outdoor fields; it may be important to understand potential
differences for exposure assessment. Many of the U.S. studies have examined metal constituents and a
modest number have measured VOCs, PAHs and benzothiazole, but relatively few studies have tried to
systematically measure or look for the presence or absence of many other organic chemicals potentially
associated with tire materials across a large range of samples from around the U.S. Also, most of the
synthetic field measurements from the studies conducted to date have been for particles, metals or
organics in air; only a few studies measured chemicals present on field surfaces or in field dust.
A few small studies have investigated bacterial loads and the occurrence of select pathogens in synthetic
turf athletic fields. The investigations that have been conducted did not focus directly on tire crumb
rubber infill material; rather, the samples were collected from the fields and few potential pathogens
were investigated. Furthermore, all studies reported to date have used traditional culture methods to
detect and quantify total bacteria and pathogen densities. These methods can underestimate densities
because culture media cannot support the growth of all bacteria and pathogens. Furthermore, bacteria
can enter a viable, but nonculturable state in some environments (Oliver, 2005), which prohibits their
detection by culture methods. The use of molecular methods, like polymerase chain reaction (PCR) and
high throughput sequencing, are not hindered by these limitations and can provide a more thorough and
robust analysis of bacteria and pathogens in tire crumb rubber infill.
While research efforts have tended to focus on characterizing tire crumb rubber constituents and
environmental concentrations of related chemicals, less research has been performed to examine human
exposures and potential risks to people using synthetic turf fields and playgrounds, especially for
children. With respect to exposure characterization, human exposure measurement data for synthetic turf
field users are limited. There are significant data gaps in human activity parameters for various synthetic
turf field activities, and this information is essential for estimating exposures and evaluating risks from
contact with tire crumb rubber constituents. While the potential for inhalation exposures has been
characterized for some constituents, there is far less information for characterizing dermal and ingestion
exposures. Improved exposure factor information is needed to estimate and model exposures from the
inhalation, dermal, and ingestion pathways. There are also significant limitations in the methods that
have been developed and used to characterize human exposure from activities on synthetic turf fields.
These include challenges collecting relevant surface, dust, and personal air samples; limited
measurements of dermal exposures; and limited collection of urine or blood samples, which could be
used for measuring biomarkers of exposure to chemicals in crumb rubber infill.
Some elements of the research design outlined in the Research Protocol (U.S. EPA & CDC/ATSDR,
2016) were intended to fill these knowledge gaps and address the limitations of prior studies. There are
two on-going studies in the United States that are providing information complementary to that under
the FRAP. California's Office of Environmental Health Hazard Assessment (OEHHA, 2019) began a
study in 2015 under contract with CalRecycle to examine synthetic turf and potential human health
impacts. OEHHA researchers are also conducting research aimed at reducing data gaps for tire crumb
rubber constituents and human exposures. The federal research team regularly consults with OEHHA
scientists to discuss how the two studies can be mutually informative. The federal and state researchers
have attempted to identify and implement methods and approaches that will, where feasible, produce
comparable data. This could effectively expand the overall U.S. research sample size and will provide
additional insight into potential exposure variability. There are also important differences between the
federal and OEHHA studies that will provide complementary data addressing different data gaps. The
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complementary approaches conserve resources for each study and will expand our knowledge for
improved exposure assessment. Additionally, the National Toxicology Program (NTP) of the National
Institutes of Environmental Health Sciences (NIEHS) has performed recent research to characterize
chemicals in 'fresh' tire crumb rubber from two recycling plants, assessed methods for conducting
toxicity testing of the material, and performed short-term in-vivo and in-vitro toxicity testing (Cristy,
2018; Gwinn, 2018; Richey, 2018; Roberts, 2018).
The results of the FRAP research will complement research efforts by providing information not being
produced by other organizations. FRAP research is characterizing tire crumb rubber collected from
recycling plants, indoor fields and outdoor fields across the United States; assessing releases of
chemicals into the air and into simulated biological fluids; performing exposure measurements to better
understand the potential exposures from inhalation, dermal and ingestion pathways; and conducting
biomonitoring studies for children and adults using synthetic turf fields. Results from the FRAP, along
with research results from other organizations, will fill multiple data gaps and will be essential for
improving exposure and risk assessment.
1.3.3 Tire Crumb Rubber Characterization
The tire crumb rubber characterization portion of the study was a pilot-scale effort that involved
collecting tire crumb rubber material from nine tire recycling plants and 40 synthetic turf fields around
the United States, with laboratory analysis for a wide range of metals (21 target analytes), VOCs (31
target analytes), SVOCs (49 target analytes) and microbes. As defined in the research protocol (U.S.
EPA & CDC/ATSDR, 2016), there were three primary aims or objectives for the tire crumb
characterization research:
Aim 1: Characterize a wide range of chemical, physical and microbiological constituents and
properties for tire crumb rubber infill material collected from tire recycling plants and synthetic
turf fields around the United States;
Aim 2: Collect information from facilities around the United States to better understand how
synthetic turf fields with tire crumb rubber infill are operated, maintained, and used with regard
to characteristics potentially impacting human exposure to tire crumb rubber constituents; and,
Aim 3: Identify and collate existing toxicity reference information for selected chemical
constituents identified through the tire crumb rubber characterization measurements.
To meet the first research objective, the Agencies collected and tested different types of tire crumb
rubber to better understand the constituents that are present and might be emitted from the material, as
well as constituents that can be transferred from tire crumb when a person comes into contact with it
(e.g., when tire crumb comes in contact with sweat on the skin or is accidentally ingested by athletes
playing on synthetic turf fields). Tire crumb rubber samples were collected directly from tire recycling
plants to provide information on constituents in unused material, while samples from outdoor and indoor
synthetic turf fields were collected to provide a better understanding of constituents potentially available
for exposure in different weathering conditions and facility types. Characterization utilized multiple
analytical methods, including direct extraction and analysis of metals and SVOC constituents of tire
crumb rubber, dynamic emission chamber measurements of VOC and SVOC emissions and emission
rates from tire crumb rubber, and bioaccessibility testing of metals. The emissions and bioaccessibility
experiments provided important information about the types and amounts of chemical constituents in the
tire crumb rubber material available for human exposure through inhalation, dermal, and ingestion
pathways. A combination of targeted quantitative analysis, suspect screening, and non-targeted
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approaches was applied for VOCs and SVOCs to ascertain whether there may be potential chemicals of
interest that have not been identified or reported in previous research. Physical characteristics, such as
particle size, sand content and moisture content, were also examined to better understand potential
exposures, and analyses were employed to address gaps in knowledge regarding microbial pathogens
associated with tire crumb rubber on synthetic turf fields.
To meet the second objective, questionnaires were administered to facility owners and managers to
obtain information about potential factors that may affect exposures, including source materials, material
age, tire crumb rubber addition or replacement frequencies, maintenance procedures, facility operations,
and facility use.
To meet the third objective, toxicity reference information was identified and collated from existing on-
line databases and literature sources for select chemical constituents. The selection of chemicals to
include in toxicity reference information gathering was based on a combination of factors, such as
presence/absence, frequency of detection, relative concentration magnitude, and other information
identified in the LRGA.
The data collection components of the tire crumb rubber characterization study went through the OMB
Information Collection Request review process. On August 5, 2016, EPA and CDC/ATSDR received
final approval to begin the research.
1.4 Report Organization
This report is organized into two volumes - Volume 1 contains the body of the report; Volume 2
contains the appendices. Volume 1 consists of seven sections:
• Section 1 provides background and an introduction to the federal research action plan and its
objectives.
• Section 2 provides a summary of the research results and main conclusions from the tire crumb
rubber characterization study, along with important limitations.
• Section 3 provides detailed methods for the tire crumb rubber characterization research.
• Section 4 provides detailed results for the tire crumb rubber characterization, with result tables
and figures focusing on select chemicals of interest.
• Section 5 summarizes toxicity reference information for tire crumb rubber chemicals.
• Section 6 contains the references.
• Section 7 contains a listing of appendices.
Volume 2 of this report consists of 22 appendices:
• Appendices A-C are included from the FRAP Status Report (U.S. EPA, CDC/ATSDR & CPSC,
2016b) for completeness.
• Appendix D contains a list of standard operating procedures (SOPs) used for the tire crumb
rubber characterization study.
• Appendix E contains the Quality Assurance/Quality Control section.
• Appendix F contains the study questionnaire for the tire crumb characterization research effort.
• Appendices G-U include more complete reporting of results from the tire crumb characterization
research activities.
• Appendix V contains a summary of external peer review comments.
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2.0 Summary of Results and Findings
This section is divided into several parts: 1) an overview and 2) detailed summary of the results of
individual components of this part of the research study, specifically focusing on the tire crumb rubber
characterization and toxicity reference information and the associated findings based on those results;
and, a discussion of 3) research limitations; 4) recommendations for next steps; and 5) major
conclusions.
Technical details of the methods and detailed research results are provided in subsequent sections (3-5)
and their associated appendices. A list of research standard operating procedures (SOPs) is provided in
Appendix D, and the SOPs will be published in a separate report. Quality assurance and quality control
results can be found in Appendix E.
2.1 Overview of Research Activities
The federal research described in this report provides new and additional data needed for more complete
tire crumb rubber characterization that will be useful for improving exposure estimation for individuals
using synthetic turf fields with recycled tire crumb rubber infill. The study is not a risk assessment;
however, the results of the research described in this and future reports should advance the
understanding of exposure to inform the risk assessment process. Specific activities undertaken and
described in this report are summarized in Table 2-1.
Table 2-1. Topic Areas and Specific Activities Described in This Report
Topic Area
Activities
Recycling Plant and Synthetic
Turf Field Recruitment and
Sampling
Recruiting and collecting samples at multiple tire recycling facilities producing tire
crumb rubber and multiple synthetic turf fields with tire crumb rubber infill across the
United States
Synthetic Turf Field Operations
and Maintenance
Collecting information from synthetic turf field owners/managers to better understand
field operations, types and numbers of field users, field maintenance practices and the
use of chemical or other product treatments on the fields
Tire Crumb Rubber Chemical,
Physical and Microbiological
Characterization
Preparing the samples collected from tire recycling plants and synthetic turf fields for
several types of characterizations and analyses
Measuring particle size ranges and other particle characteristics of 'fresh' tire crumb
rubber from tire recycling plants and tire crumb rubber infill from synthetic turf fields
across the United States, with further exploration of particle size and morphology using
scanning electron microscopy
Completing quantitative characterization of the inorganic and organic chemical
substances found in the sampled tire crumb rubber from tire recycling plants and tire
crumb rubber infill from synthetic turf fields
Providing insight on differences between chemical substances associated with 'fresh'
tire crumb rubber produced at recycling plants and what is found in tire crumb rubber
infill on synthetic turf fields
Examining emissions of organic chemicals from tire crumb rubber material at two
temperatures for improved understanding of the potential for inhalation exposures
Assessing variability of chemicals associated with tire crumb rubber within and
between recycling plants, as well as within and between fields
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Table 2-1 Continued
Topic Area
Activities
Tire Crumb Rubber Chemical,
Physical and Microbiological
Characterization (Continued)
Examining the range of chemical concentrations found in tire crumb rubber infill from
fields across the United States and some of the important characteristics associated with
those differences across fields, including indoor vs. outdoor fields, fields with a wide
range of installation dates and fields in different U.S. regions
Using suspect screening and non-targeted analysis approaches to elucidate the
potentially larger range of chemicals for which additional information may be needed to
better understand exposures and risks
Measuring the bioaccessibility of metals from tire crumb rubber as an important
characteristic for improving understanding of potential exposure
Performing targeted and non-targeted microbial assessments to elucidate
microbiological populations associated with tire crumb rubber infill at synthetic turf
fields and characteristics associated with differences across a range of fields in the
United States
Toxicity Reference Information
Identifying and collating toxicity reference information on potential chemical
constituents of tire crumb rubber from existing on-line databases and literature sources
2.2 Tire Crumb Rubber Characterization: Overview of Research Approach, Results
and Key Findings
2.2.1 Research Approach
The tire crumb rubber characterization part of the FRAP's study involved the collection of crumb rubber
material from tire recycling plants and synthetic turf fields across the United States, with laboratory
analysis for a wide range of metals/metalloids, volatile organic compounds (VOCs), and semivolatile
organic compounds (S VOCs).5 Analyses of physical characteristics were performed to measure tire
crumb particle size fractions, particle characteristics, moisture content, and sand content. Laboratory
analyses included direct quantitative analysis of select target metals, following acid digestion, and
SVOCs, following solvent extraction. Chamber tests were performed to estimate the amounts of VOCs
and SVOCs released into the air (emission factors) under different temperature conditions.
Bioaccessibility tests were performed to measure the amounts of metals released from tire crumb rubber
using three simulated biological fluids (i.e., gastric fluid, saliva, and sweat plus sebum). The emissions
and bioaccessibility experiments were designed to provide information about the types and amounts of
chemicals in the recycled tire crumb rubber material available for human exposure through inhalation,
dermal, and ingestion pathways. In addition to quantitative target chemical analyses, additional analysis
methods (suspect screening and non-targeted analysis) were used to determine whether there may be
other VOCs and SVOCs that have not been identified or reported in previous research. The tire crumb
characterization research effort also included collecting recycled tire crumb rubber infill from synthetic
turf fields to assess microbial populations.
5 Among the target analytes, arsenic and antimony are commonly considered metalloids, while selenium is sometimes
considered a metalloid; these elements are included in the 'metals' category in this report for simplicity.
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2.2.2 Overview of Results and Key Findings
Synthetic turf field recycled tire crumb rubber infill particles
were found in sizes predominantly ranging from 0.25 to 4
mm in diameter, with a great deal of variability within this
range. While the proportion of small particles in synthetic turf
field infill (sizes < 0.063 mm) was relatively low (mean =
0.63 g/kg; median = 0.1 g/kg), their presence was consi stently
found at synthetic turf fields. These smaller particles may be
important for inhalation exposures and for exposure through
dermal contact and ingestion.
Most of the target analytes among the 21 metals and 49 SVOCs, and several of the 31 target VOCs were
found in tire crumb rubber infill collected at fields across the United States. Average concentrations
ranged from <1 mg/kg for several metals and extractable SVOCs up to 15,000 mg/kg for zinc. Examples
of these measurement results are highlighted in Figure 2-1 for metal target analytes and in Figure 2-2 for
select polycyclic aromatic hydrocarbon (PAH) analytes. In addition, suspect screening and non-targeted
analyses demonstrated that other VOCs and SVOCs may be associated with the material. Several
SVOCs tentatively identified through suspect screening analysis included chemicals reported to be used
as accelerators, anti-oxidants or anti-ozonants in rubber manufacture; however, more work would be
needed to confirm chemical identities.
~ Recycling plants (n=9) B Indoor fields (n=15) D Outdoor fields (n=25)
Figure 2-1. Average measurement results for metals in tire crumb rubber samples collected from tire
recycling plants and indoor and outdoor synthetic turf fields with tire crumb rubber infill.
Particle Size
Particles < 0.063 mm iri size were
consistently found in synthetic turf
field infill. Although the proportion
of these particles was relatively low,
small particles like these may be
important for potential exposures.
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¦ Recycling plants (n=9) B Indoor fields (n=15) O Outdoor fields (n=25)
Figure 2-2. Average measurement results for selected extractable polyaromatic hydrocarbons in tire
crumb rubber samples. [DBA + ICDP = Sum of Dibenz[a,h|anthracene and Indeno( 1,2,3-cd)pyrene; Suml5PAH =
Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene,
Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene,
Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
Comparison of chemical measurements from 'fresh' tire cnimb
rubber samples produced at recycling plants (i.e., tire crumb
rubber not yet installed at a field) to tire crumb rubber infill
from synthetic turf fields showed that most of the chemicals
found in synthetic turf infill were also present in the 'fresh' tire
crumb nibber from recycling plants. Many of the SVOCs and
VOCs were found at average higher levels in tire crumb rubber
from recycling plants. Additional research involving
longitudinal studies at individual fields would be needed to
confirm that vaporization, weathering, and/or other
mechanisms may lead to lower concentrations of these
chemicals overtime when installed on playing fields. A few
chemicals, including lead and bis(2-ethylhexyl) phthalate, had
higher average levels in tire crumb rubber infill from synthetic
turf fields compared to tire crumb rubber from recycling plants.
Similarly, additional research would be needed to determine if
external sources may contribute to the levels of some
chemicals found in the tire crumb rubber infill at synthetic turf
fields.
One synthetic turf field had a substantially higher measured
concentration of lead (160 mg/kg) in its composite tire crumb
rubber infill sample than other fields, while another field had
similar levels in two of seven individual location samples.
These results suggest sources of lead other than tire crumb
rubber may be present at some locations
Chemical Constituents
• Most metals and many semivolatile
organic compounds (SVOCs) found in
previous tire crumb rubber studies
were found at similar concentrations
in the infill of synthetic turf fields.
• Some SVOCs and VOCs not widely
reported in previous studies have
been tentatively identified but not
confirmed.
'Fresh' Tire Crumb vs. Tire
Crumb Rubber Infill
• Most tire crumb rubber metals were
present in synthetic turf field infill at
levels similar to those in 'fresh' tire
crumb rubber from recycling plants.
• Many organic chemicals were present
in synthetic turf field infill at levels
lower than those in 'fresh' tire crumb
rubber from recycling plants.
• A few chemicals, including lead and
bis(2-ethylhexyl) phthalate, were
present, on average, at higher levels
in the infill of synthetic turf fields
compared to 'fresh' tire crumb
rubber.
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This study afforded the largest sample size to date in the United
States to examine variability in chemicals associated with tire
crumb rubber infill at synthetic turf fields and field
characteristics related to those differences. In general, the
variability in chemical concentrations between fields was much
greater than the variability within fields for most organic
chemicals (VOCs and SVOCs), with more mixed results found
for metals. Most organic chemicals were found at higher levels
at indoor fields compared to outdoor fields. Many organic
chemicals, particularly those in the more volatile ranges,
showed a pattern of decreasing concentration with increasing
field installation age at outdoor fields.
Measurement results in this study for metal and extractable
SVOC target analytes were compared to those reported in other
studies. Table 2-2 shows select metal concentration results
obtained in this study compared to results in several previous
studies. In general, concentrations measured in this study were
consistent with, and within the range of, concentrations found
in previous studies. Table 2-3 shows select extractable SVOC
concentrations measured in this and other studies. In general,
concentrations measured for outdoor fields in this study were within the range of measurements from
other studies for most analytes where comparable data are available. Benzothiazole and bis(2-
ethylhexyl) phthalate measurements in this study were higher than results obtained in two recent studies.
There were relatively few measurements available for comparisons with recycling plant and indoor field
samples from previous studies.
Variability in Organic
Chemical Concentrations
• Most organic compounds were found
at higher levels at indoor fields
compared to outdoor fields.
• At outdoor fields, lower levels of
organic chemicals, particularly VOCs
and the more volatile SVOCs, were
found with increased age of the
synthetic turf field.
• For most organic chemicals there was
more variability in levels between
different fields than at different
locations within a field.
13
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Table 2-2. Comparison of Select Tire Crumb Rubber Metal Analysis Results Across Multiple Studies3
Chemical
This Studv
Cristv
IMarsili
This Studv
This Studv
Celeiro
IMarsili
Ruffino
Kim
IMcnichini
U.S. EPA
Bocca
Zhang
2019-
2018-
2014-
2019 -
2019 -
2018-
2014-
2013
2012-
2011 -
2009-
2009-
2008-
Rccycling
Rccvcling
New
Indoor
Outdoor
Outdoor
Outdoor
Outdoor
Outdoor
Outdoor
Outdoor Fields
Outdoor
Outdoor Fields
Plants
Plants
Unused
Fields
Fields
Fields
Fields
Fields
Fields
Fields
(n=4 fields;
Fields
(n=2 fields;
(n=9)
(n=2)
(n=5)
(n=15)
(n=25)
(n—2)
(n=4)
(n=4)
(n=50)
(n=4)
n=26 samples)
(n=32)
n=4 samples)
Arsenic
0.30
0.81
N/A
0.37
0.39
0.71
N/A
N/A
N/A
0.19
0.24
0.24
1.4
Cadmium
0.55
0.65
1.8
1.1
0.86
0.84
1.5
N/A
0.46
1.3
0.70
0.37
0.30
Chromium
1.8
N/A
7.0
1.5
1.7
1.4
3.5
N/A
11
2.5
0.56
6.2
1.0
Cobalt
190
145
N/A
139
135
184
N/A
112
N/A
28
N/A
15
N/A
Lead
13
13
21
31
20
21
26
96 (26)b
39
21
28
22
17
Zinc
17000
16800
6437
15000
15000
14150
4809
13125
3752
13514
8749
10229
7849
a All results are mean values with exception of median values reported in Bocca 2009; All results are in mg/kg; N/A = not applicable
b Tire crumb rubber at one field had a lead concentration of 308 mg/kg. The average is 26 mg/kg without that field included.
Table 2-3. Comparison of Selected Tire Crumb Rubber Extractable SVOC Analysis Results Across Multiple Studies3
Chemical
This Studv
IMarsili
Gomes
This Studv
Salonenb
This Studv
Celeiro'
RIVMd
IMarsili
Ruffino
IMcnichini
Zhang'
2019-
2014-
2010 -
2019 -
2015 -
2019-
2018-
2017-
2014-
2013-
2011-
2008 -Outdoor
Rccycling
New
Recycling
Indoor
Indoor
Outdoor
Outdoor
Outdoor Fields
Outdoor
Outdoor
Outdoor
Fields (n=4
Plants
Unused
Plant
Fields
Fields
Fields
Fields
(n=91 fields or
Fields
Fields
Fields
fields, n=7
(n=9)
(n=5)
(n=l)
(n=15)
(n=4)
(n=25)
(n=15)
n=7 fields)
(n=4)
(n=4)
(n=5)
samples)
Phenanthrene
3.6
0.74
1.4
4.8
6.0
0.76
0.75
<0.6
0.34
N/A
N/A
1.2
Fluoranthene
6.1
2.4
4.5
6.2
9.9
3.5
3.5
3.4
1.4
N/A
N/A
4.9
Pyrene
18
5.2
14
19
26
8.8
8.0
7.5
4.0
22
6.6
6.3
Benzo[a]pyrene
0.74
0.25
1.2
0.98
1.4
0.66
1.0
<1.1
0.26
0.96
3.6
2.0
Benzo [ghijperylene
1.3
0.55
<0.08
1.6
5.0
1.1
3.3
4.1
0.40
2.5
N/A
2.3
Benzothiazole
79
N/A
N/A
19
N/A
5.6
1.9
2.7
N/A
N/A
N/A
N/A
4-tert-octylphenol
30
N/A
N/A
20
N/A
3.5
N/A
4.5
N/A
N/A
N/A
N/A
Diisobutyl phthalate
0.50
N/A
N/A
2.7
N/A
0.36
2.5
<0.5
N/A
N/A
N/A
N/A
Bis(2-ethylhexyl)
12
N/A
N/A
65
N/A
29
8.7
7.6
N/A
N/A
N/A
N/A
phthalate
11 All results are mean values with exception of a single measurement in Gomes 2010 and median values reported inRIVM 2017; All results are in mg/kg; N/A = not applicable
bFor the several values that were below the limit of detection, one-half the limit of detection was substituted for calculating a mean result.
0 Mean values reported in Celeiro et al. (2018) Table 2 were based only on reported (non-missing) values. It was assumed that the missing values were non-detects. A substitution of one-
half the lowest reported value was made for missing results to calculate overall means for this table. Mean results in this table differ from means in Celeiro et al., as a result.
dThis study included 546 samples from 91 fields for many PAHs and two phthalates [bis(2-ethylhexyl) phthalate and diisobutyl phthalate]; 43 samples from 7 fields for the
remaining phthalates; and 7 samples from 7 fields for several PAHs, phenols, and thiazoles.
e Substituted detection limits for non-detects.
14
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Measurement of emissions of organic chemicals from tire crumb
rubber infill was conducted to improve our understanding of the
potential for human exposures through the inhalation pathway.
This study generated emission test results for VOCs and
SVOCs using dynamic emissions testing chambers in the
laboratory. Tests were performed at 25 °C and 60 °C. For
most VOC and SVOC target analytes, emissions were low at
25 °C and in many cases, not measurable above the method
limit of detection or above chamber background levels. At
60°C, higher emissions were measured for some, but not all,
VOCs and SVOCs. The less volatile SVOCs had very low or
non-measurable emissions, with the 5- and 6-ring PAHs
generally not measurable above the limit of detection at either
25 °C or 60 °C.
Emissions for most VOCs and SVOCs were higher for tire
crumb rubber from recycling plants compared to tire crumb
rubber infill from synthetic turf fields. Higher emissions were
observed for most chemicals from infill collected at indoor
fields compared to outdoor fields, and several of the VOC and
SVOC target analytes showed a pattern of decreasing
emissions with increasing field installation age at outdoor
fields.
The amount of chemicals released from tire crumb rubber and
solubilized into body fluids (bioaccessibility) characterizes the
potential exposure of a receptor to the chemical, which in turn
determines what is available for absorption (bioavailability).
The bioaccessibility of metals in the tire crumb rubber and tire
crumb rubber infill samples collected in this study was
measured using three artificial biological fluids, specifically
gastric fluid, saliva, and sweat plus sebum. For metals, only
small fractions were released into simulated biological fluids
(e.g., the average bioaccessibility values for lead from tire
crumb rubber infill were approximately 3% for gastric fluid
and less than 0.1% for saliva and sweat plus sebum). For all
metals, the mean bioaccessibility values averaged
approximately 3% in gastric fluid, and less than 1% in saliva
and sweat plus sebum. These results fill important knowledge
gaps about potential bioavailability of recycled tire crumb rubber.
While it is recognized that presence of a chemical in a material
does not mean that the chemical is available for absorption, exposure and risk assessments often default
to using 100% of the chemical being bioaccessible and/or bioavailable in the absence of medium-
specific information (U.S. EPA, 2007). Findings from this study support the premise that while many
chemicals are present in the recycled tire crumb rubber, exposure may be limited based on what is
released into air or biological fluids. A default to 100% bioaccessibility should not be used when
assessing potential exposures to most metals in tire crumb rubber.
Organic Chemical Emissions
Measuring emissions of organic
chemicals is important for
understanding the potential for
inhalation exposures associated with
tire crumb rubber.
Emissions tests were performed at
25 °C and 60 °C to reflect moderate
and high-end field temperature
conditions.
At 25 °C, emissions of most organic
chemicals were low, and in many
cases, not measurable above the
detection limit or background level.
At 60 °C, emissions increased for some
organic chemicals; some chemical
emissions remained very low or non-
measurable even at higher
temperatures.
Among the chemicals examined, methyl
isobutyl ketone and benzothiazole had
the highest emission factors.
Higher emissions were observed for
most chemicals at indoor fields
compared to outdoor fields.
At outdoor fields, lower emissions of
several organic chemicals were found
with increased age of the synthetic turf
field.
People may also inhale small particles
of tire crumb rubber at fields; this type
of exposure was not assessed in the
chamber emission testing.
15
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Tire crumb rubber infill samples collected from synthetic turf
fields were analyzed for select targeted microbe genes; non-
targeted analysis was also performed to assess the wider
microbial community. All samples tested from the 40 fields
were positive for bacteria genes, showing widespread microbial
presence at synthetic turf fields. Synthetic turf fields contain
diverse bacterial communities, as 1,424 unique bacterial taxa
were detected across the fields examined. Fields that were in
outdoor settings tended to have higher concentrations of
bacteria than indoor fields. However, indoor fields showed a
higher occurrence of methicillin resistance genes than outdoor
fields. Likewise, a gene for Staphylococcus aureus, a common
member of the human skin microbiome and potential carrier of
methicillin resistance genes, was detected more frequently in
indoor fields than outdoor fields. Although methicillin
resistance genes were detected in the community of bacteria in
synthetic turf fields, it is uncertain if these genes were carried
by potential human pathogens.
There were no directly-comparable genetic studies found for
either synthetic turf or grass playing fields. Small studies that
cultured bacteria have found more colony forming units (CFU)
for some bacteria at grass fields compared to synthetic turf
fields (McNitt et al., 2007; Vidair, 2010), and two independent
studies showed that the addition of rubber to soil significantly
reduced concentrations of culturable bacteria and the metabolic
activity of the natural microbial community (Goswami et al.,
2017; Pochron et al., 2017). The presence of a bacterial
community in synthetic turf fields is not surprising, however.
Bacteria have been reported at similar concentrations in
environments that humans encounter, such as indoor air (5.6
logio bacteria-like particles [BLP]/m3), outdoor air (8.4 logio
BLP/m3; Prussin, et al. 2015) and common household items,
including mobile phones (4.2 logio gene copies of 16S
ribosomal ribonucleic acid (rRNA) genes per phone; Koljalg et
al., 2017) and kitchen hand towels (7.2 logio CFU per towel;
Gerba et al. 2014). It should also be noted that the human body
harbors an estimated 13.6 logio bacteria (Sender et al., 2016).
In another study (Vidair, 2010), researchers cultured
Staphylococcus and methicillin-resistant Staphylococcus
aureus (MRSA) from samples collected at five synthetic turf
field and two grass fields. In that study, 2 of the 30 samples
collected from synthetic turf were positive for a species of
Staphylococcus compared to 6 of 12 samples collected from
natural turf. No MRSA was detected on synthetic turf, while a
single sample of blades from natural turf was positive for MRSA.
Vidair (2010) concluded that their data indicated that the new
generation of synthetic turf containing crumb rubber infill harbors
fewer bacteria than natural turf, including Staphylococcus and MRSA.
Bioaccessibility of Metals
Bioaccessibility of metals for
absorption by the human body was
tested by measuring the amount of
metals released from tire crumb
rubber and able to be solubilised in
three artificial body fluids (gastric
fluid, saliva, and sweat plus sebum).
For all metals, the mean
bioaccessibility values averaged
approximately 3% in gastric fluid, and
less than 1% in saliva and sweat plus
sebum.
Average bioaccessibility values for
lead from tire crumb rubber infill
were approximately 3% for gastric
fluid and less than 0.1% for saliva and
sweat plus sebum.
Microbes and Bacteria
All synthetic turf field samples tested
positive for bacteria, but this is not
surprising given that bacteria have
been reported at similar
concentrations in indoor air, outdoor
air and on common household items.
The bacterial community present in
synthetic turf fields is diverse - over
1,424 unique bacteria were found in
the samples tested.
Outdoor fields tended to have higher
overall levels of bacteria compared to
indoor fields; however higher levels
of two specific bacteria genes were
found at indoor fields.
16
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2.2.3 Tire Crumb Rubber Characterization Synopsis
Based upon available literature, this research represents the largest and most robust study of synthetic
turf fields and tire crumb rubber to date in the United States. Tire crumb rubber samples were collected
from nine tire recycling facilities, and tire crumb rubber infill was collected from 40 synthetic turf fields
across the United States. The fields represented a range of field types, field ages and geographic
locations and included both indoor and outdoor fields. Multiple analytical techniques were applied to
measure physical, chemical and microbiological attributes of the various groups of samples. Tire crumb
rubber characterization results from this portion of the research provide insight into the number and
types of chemicals associated with the material, the amount of chemicals released into the air and
biological fluids, and the range and variability of these parameters.
• As expected, because of the complexity of the material, many chemicals were found to be
associated with tire crumb rubber collected from tire recycling plants and tire crumb rubber infill
collected from fields across the United States, including a range of metals, PAHs, phthalates and
other tire rubber related chemicals. Suspect screening and non-targeted analyses showed an
additional number of organic chemicals, many of which had not been characterized in previous
studies, however, further work would be needed to confirm identities of these chemicals. In
general, concentrations of chemicals measured in outdoor synthetic turf field infill were similar
to those measured in other studies where comparable data are available.
• Concentrations of many organic chemicals appeared to decrease with increasing field age. These
results support the idea that vaporization, weathering (including leaching from rainfall or
irrigation) and/or other mechanisms for removal lead to lower concentrations of many organic
chemicals over time, particularly for outdoor fields. While an alternative explanation that there
may have been different concentrations of chemicals in recycled tires over time cannot be ruled
out, the patterns seen across vapor pressure and water solubility, and differences between indoor
and outdoor fields of similar ages appear to favor a weathering explanation for the differences.
Additional research, including longitudinal studies at individual fields, would be needed to
confirm this.
• Organic chemical concentrations were generally higher at indoor fields, which have reduced
weathering effects. When combined with the lower ventilation rates for indoor facilities
compared to outdoor fields, these results suggest that exposures to organic chemicals associated
with tire crumb rubber may be higher for people using indoor fields. Additional research would
be needed to confirm this. Results from two sets of indoor air measurements in other studies
support this finding (Norwegian Institute of Public Health and the Radium Hospital, 2006;
Simcox et al., 2010), however, relatively few indoor fields have been studied.
• VOC and SVOC laboratory chamber emission experiments provided information about the
potential for chemicals associated with tire crumb rubber to be released into the air and to
become available for inhalation exposure. Most of the target organic chemicals had relatively
low or non-measurable emissions at 25 °C. Some, but not all, had higher emissions at 60 °C.
Methyl isobutyl ketone and benzothiazole had among the highest emission factors and have also
been measured in the air at synthetic turf fields in other studies, above ambient background
levels. In the few studies taking measurements at indoor field facilities, chemicals associated
with tire crumb rubber have been shown to have higher concentrations in indoor air compared to
the air at outdoor fields. Releases and exposures are also likely to be higher for some organic
chemicals as the field temperature increases. Emissions data from this and other studies as well
as field measurement data could be further developed in modeling approaches to estimate air
17
-------
concentrations and inhalation exposures under different conditions for both vapor- and particle-
phase chemicals associated with tire crumb rubber.
• While the characterization measurements demonstrate that there are many chemicals detected in
tire crumb rubber, the in vitro bioaccessibility measurements of the metals in three simulated
biological fluids indicate that the amounts that can be released from the material for absorption
are relatively low when compared to a default assumption of 100% bioaccessibility. For all
metals, the mean bioaccessible fractions averaged approximately 3% in artificial gastric fluid,
and less than 1% in saliva and in sweat plus sebum. Although bioaccessibility of organic
chemicals, such as PAHs, was not measured in this study, other studies suggest they too are
bioaccessible at low percentages - < 10% of PAHs into simulated gastrointestinal tract and
< 0.1% into simulated sweat in two studies (RIVM, 2017; Pronk et al., 2018) and below the
detection limits in another study (Pavilonis et al., 2014).
• The presence of many chemicals in combination with low bioaccessibility suggest the
complexity and challenge to accurately assess cumulative exposures for synthetic turf field users
that can occur through different exposure pathways.
2.3 Toxicity Reference Information: Overview of Research Approach, Results and Key
Findings
Extant toxicological reference information was compiled for potential tire crumb rubber chemical
constituents identified in the tire crumb rubber Literature Review and Gap Analysis (LRGA; released
December 30, 2016 and included as Appendix C in this report). Eleven sources of toxicity reference
information were searched. At least one source of extant toxicity reference information was available for
167 (47%) of the 355 potential constituents examined. When narrowing this down from the LRGA's list
of 355 to its subset of target chemicals in this study (95), toxicity reference information is available from
at least one source for 78 of those (about 82%).
In summary, some toxicity reference information is available
for almost half of the list of potential chemicals associated with
tire crumb rubber and for most of those in the target analyte list
of this study. It is important to recognize that some of these
target analytes were not found, or were not consistently found,
in tire crumb rubber in this portion of the study. Some potential
toxicity-related information beyond the sources reviewed may
be available in the literature but was not evaluated here. In
addition to the target chemicals measured in this study, the
presence of many other organic chemicals was found through
non-targeted assessment. Further work would be needed to
positively identify chemicals and their amounts, and to
determine the availability of toxicity information for these
chemicals.
Toxicity testing of the whole material vs. individual constituents (being performed by the National
Toxicity Program) is a reasonable approach for assessing cumulative toxicity for a complicated multi-
chemical material such as tire crumb rubber. While the National Toxicology Program has recently
presented short-term toxicity results for the recycled tire crumb rubber material itself using in vivo and
in vitro testing (Gwinn et al., 2018; Richey et al., 2018; Roberts et al., 2018), more comprehensive data
may be needed for both cumulative toxicity and risk assessments.
Toxicity of Recycled
Tire Crumb Rubber
• Toxicity reference information was
identified for 167 of 355 potential
tire crumb rubber constituents.
• When narrowing this down from
the LRGA's list of 355 to its subset
of target constituents in this study
(95), toxicity reference
information is available for most
(78) of those (about 82%).
18
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2.4 Detailed Summaries of Research Results
2.4.1 Recycling Plant and Synthetic Turf Field Recruitment and Sampling
Organizations across the United States were recruited to allow for collection of tire crumb rubber
samples for analysis. These included tire recycling facilities producing "fresh" tire crumb rubber for use
on synthetic turf fields and owners of synthetic turf fields with tire crumb rubber infill.
• CDC/ATSDR and EPA reached sample collection agreements with six tire recycling companies
that manufacture recycled tire crumb rubber infill at nine tire recycling facilities where tire
crumb rubber samples were collected.
• The nine tire recycling facilities from which samples were collected used two different processes
to manufacture the recycled tire crumb rubber - three used a cryogenic process and six used an
ambient process.
• A total of 40 synthetic turf fields with tire crumb rubber infill were recruited for sample
collection, including 21 community fields and 19 synthetic turf fields at U.S. Army military
installations.
• The distribution of the 40 synthetic turf fields included 25 outdoor synthetic turf fields and 15
indoor fields across the four U.S. census regions, with nine fields in the Northeast, 13 in the
South, eight in the Midwest, and 10 in the West.
• The synthetic turf fields sampled included a variety of ages, with 11 fields installed between
2004 and 2008, 18 fields installed from 2009 to 2012, and 11 fields installed from 2013 to 2016.
2.4.2 Synthetic Turf Field Operations and Maintenance
A total of 40 questionnaires were administered over the phone to field owners or managers of the 40
synthetic turf fields recruited in this study to obtain information on field use and field maintenance
practices. A majority of the interviewed facility persons reported they were managers of the synthetic
turf fields (87.5%).
• Replacing all tire crumb rubber infill on the fields was not commonly reported. Only one indoor
field and one outdoor field reported replacing all tire crumb rubber infill.
• Interviewees for indoor fields were more likely to report refreshing or adding tire crumb rubber
(60%) than outdoor fields (46%).
• Interviewees for indoor fields were more likely to report treatment with cleaning agents, anti-
static agents, or with biocides than outdoor fields (50% and 17%, respectively).
• Brushing and leveling were commonly-reported infill maintenance practices for both indoor
fields (60%) and 40%, respectively) and outdoor fields (56% and 52%, /respectively).
• A large majority of the fields (85%) reported they did not have standard practices in place to
reduce exposure to tire crumb rubber.
19
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2.4.3 Tire Crumb Rubber Physical, Chemical and Microbiological Characterization
2.4.3.1 Particle Size and Characteristics
Particle size analysis was performed for three tire crumb rubber samples collected from each of the nine
tire recycling plants and from composite tire crumb rubber infill samples collected at each of the 40
synthetic turf fields. A sieving method was used to generate seven particle size fractions for each
sample, ranging from < 0.063 to > 4.75 mm, for weighing.
• For 'fresh' tire crumb rubber samples from recycling plants, on average, a majority of the tire
crumb was found in the > 1- to 2-nim size fraction (780 g/kg), with smaller amounts in the >
0.25- to 1-mm (140 g/kg) and the > 2- to 4.75-mm (86 g/kg) size fractions. On average, 1.2 g/kg
was measured in the > 0.125- to 0.25-mm fraction, 0.35 g/kg was measured in the > 0.063- to
0.125-mm fraction, 0.089 g/kg in the > 4.75-mm fraction and 0.037 g/kg in the < 0.063-mm
fraction.
• For synthetic turf field tire crumb rubber infill samples, on average, the majority of the tire
crumb was also found in the > 1- to 2-mm size fraction (580 g/kg), with smaller amounts in the >
2- to 4.75-mm (250 g/kg) and the > 0.25- to 1-mm (170 g/kg) size fractions. On average, 0.75
g/kg was measured in the > 0.125- to 0.25-mm fraction, 0.63 g/kg in the < 0.063-mm fraction,
0.47 g/kg was measured in the > 0.063- to 0.125-mm fraction and 0.18 g/kg in the > 4.75-mm
fraction.
• While a majority of the tire crumb rubber was found in the > 1- to 2-mm size fraction, there was
substantial variability across the amounts measured in the > 0.25- to 1-mm, > 1- to 2-mm, and >
2- to 4.75-mm size fractions for infill collected at synthetic turf fields.
• On average, there were higher amounts of the smallest particle size fraction on fields as
compared to 'fresh' tire crumb aibber from recycling plants. It could not be directly determined
if the higher amounts of these smaller particles present at the synthetic turf fields was a result of
the breakdown of larger tire rubber particles. Particles from crustal, atmospheric deposition and
biogenic sources are also likely to be present at the fields, but the relative amounts of non-rubber
particles were not measured.
• Examples of the different size ranges of tire crumb rubber infill collected at synthetic turf fi elds
are shown in Figure 2-3.
Figure 2-3. Example close-up photos of tire crumb rubber infill
collected at four synthetic turf fields showing a range of particle
sizes. Scale gradations are 1 mm.
20
-------
• With one exception, there were no statistically-significant differences in size fractions of tire
crumb rubber infill samples grouped by field characteristics, including indoor vs. outdoor,
installation age, and geographic region. For the > 2- to 4.75-mm size fraction, mean values
ranged from 100 to 390 g/kg at fields across the four U.S. census regions, and the differences
among regions was statistically significant at the a = 0.05 level (p = 0.0168).
• The average moisture content in tire crumb rubber samples from recycling plants was 0.81%
(range 0.52 to 0.99%). In tire crumb rubber infill from synthetic turf fields, the average moisture
content was 1.0% (range 0.40 to 6.2%). All chemical analysis measurement results were adjusted
for moisture and reported as amount per dry tire crumb rubber material.
• Sixteen fields (40%) had sand in the tire crumb rubber infill samples. The average sand content
among the infill samples collected from the surface of those sixteen fields was 19% by weight
(range 0.33 to 53%). Chemical analysis measurement results in this report have not been adjusted
for sand fraction in the synthetic turf field infill.
2.4.3.2 Metals
Tire crumb rubber from recycling plants and tire crumb rubber infill from synthetic turf fields was
quantitatively analyzed for 21 metals by acid extraction and inductively coupled plasma/mass
spectrometry (ICP/MS) analysis, with 20 of those metals measurable above the detection limit in most
samples. Selenium was not measured above the method detection limit in any sample. (Mercury was
analyzed only in the bioaccessibility samples and is not reported here).
• Examples of average metal measurement results for samples collected at recycling plants vs.
synthetic turf fields include chromium (1.8 vs. 1.6 mg/kg), lead (13 vs. 24 mg/kg), cobalt (190
vs. 140 mg/kg) and zinc (17,000 vs. 15,000 mg/kg).
• Maximum values of these four metals in synthetic turf field samples were 3.7, 160, 290 and
22,000 mg/kg for chromium, lead, cobalt, and zinc, respectively.
• Examples of the measurement results and comparisons between recycling plant samples and
synthetic turf field samples are shown in Figure 2-4 for lead and zinc.
Lead Zinc
16CH
20000
ro 80
D)
^:
ra16000
E
12000
Recycling Plants
Fields
Recycling Plants
Fields
Figure 2-4. ICP/MS metal analysis results (mg/kg) for tire crumb rubber collected
from tire recycling plants and tire crumb rubber infill composite samples from
synthetic turf fields for lead and zinc.
21
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• Lead was found, on average, at statistically significant higher levels (p-value = 0.0060) on
synthetic turf fields compared to 'fresh' material coming from recycling plants (24 vs. 13 mg/kg,
respectively). Additional research would be needed to confirm this trend at individual fields; if
confirmed, possible explanations include atmospheric deposition or transport from nearby soils,
track-in by field users, and/or presence in and release from other synthetic turf field materials. It
is also possible that tires recycled in years prior to 2016 had higher levels of lead than tires being
recycled now, but no evidence of this was found in the literature.
• Zinc was found, on average at statistically significant lower levels (p-value = 0.0063) on
synthetic turf fields compared to 'fresh' material coming from recycling plants (15,000 vs.
17,000 mg/kg, respectively). Zinc has been shown to leach from tire crumb rubber in water. If
additional research confirmed this trend at individual fields, rainfall and/or irrigation could be
one possible explanation for the lower levels found at fields. In this study, however, there was no
statistically significant difference in levels of zinc found in crumb rubber collected at outdoor
and indoor fields, both had average concentrations of 15,000 mg/kg.
• Table 2-4 shows a comparison of average metal measurement results in this study to
measurements obtained in other studies. The comparison studies were restricted to those
analyzing uncoated tire crumb rubber from synthetic turf fields or recycling plants. In general,
measurements in this study were within or near to the range of measurements from other studies.
There were fewer comparable studies with results for indoor fields or recycling plants. No
directly comparable data were found for some of this study's target analytes, and some other
studies provided results for analytes that were not quantitatively analyzed in this study.
22
-------
Table 2-4. Comparison of Tire Crumb Rubber Metal Analysis Results Across Multiple Studies"
Chemical
This Study
2019-
Recvclinjj
Plants
Mean
(n=9)
Cristy
2018-
Rccyclinjj
Plants
Mean
(n=2)
Marsili
2014-
New
Unused
Mean
(n=5)
This Study
2019-
Indoor
Fields
Mean
(n=15)
This Study
2019-
Outdoor
Fields
Mean
(n=25)
Cclciro
2018-
Outdoor
Fields
Mean
(n=2)
Marsili
2014-
Outdoor
Fields
Mean
(n=4)
Ruffino
2013-
Outdoor
Fields
Mean
(n=4)
Kim
2012-
Outdoor
Fields
Mean
(n=50)
Mcnichini
2011 -
Outdoor
Fields
Mean
(n=4)
U.S. EPA
2009-
Outdoor
Fields Mean
(n=4 fields,
n=26 samples)
Bocca
2009-
Outdoor
Fields
Median
(n=32)
Zhang
2008-
Outdoor
Fields Mean
(n=2 fields,
n=4 samples
Aluminum
1000
1060
N/A
1100
1400
512
N/A
828
N/A
407
321
755
N/A
Antimony
1.2
N/A
N/A
1.0
0.91
N/A
N/A
N/A
N/A
0.65
N/A
1.1
N/A
Arsenic
0.30
0.81
N/A
0.37
0.39
0.71
N/A
N/A
N/A
0.19
0.24
0.24
1.4
Barium
7.4
5.2
N/A
7.8
8.6
5.1
N/A
819
N/A
8.9
38
22
N/A
Beryllium
0.015
N/A
N/A
0.0035
0.011
N/A
N/A
N/A
N/A
0.018
N/A
0.040
N/A
Cadmium
0.55
0.65
1.8
1.1
0.86
0.84
1.5
N/A
0.46
1.3
0.70
0.37
0.30
Chromium
1.8
N/A
7.0
1.5
1.7
1.4
3.5
N/A
11
2.5
0.56
6.2
1.0
Cobalt
190
145
N/A
140
140
184
N/A
112
N/A
28
N/A
15
N/A
Copper
42
45
37
25
26
37.5
28
42
N/A
17
9.7
12
N/A
Iron
490
432
1778
430
710
509
682
723
N/A
354
271
305
N/A
Lead
13
13
21
31
20
21
26
96 (26)b
39
21
28
22
17
Magnesium
290
344
N/A
340
320
426
N/A
435
N/A
408
N/A
456
N/A
Manganese
5.7
5.9
N/A
6.3
8.5
5.2
N/A
2.4
N/A
3.7
4.6
5.2
N/A
Molybdenum
0.22
N/A
N/A
0.16
0.15
N/A
N/A
N/A
N/A
0.19
N/A
0.20
N/A
Nickel
3.2
5.9
11
3.1
2.5
N/A
5.1
N/A
N/A
1.9
2.6
2.0
N/A
Rubidium
1.8
N/A
N/A
1.6
2.0
N/A
N/A
N/A
N/A
1.6
N/A
1.7
N/A
Strontium
2.9
N/A
N/A
3.4
3.4
N/A
N/A
N/A
N/A
4.6
N/A
1.2
N/A
Tin
1.8
2.0
N/A
1.6
1.6
N/A
N/A
268
N/A
1.5
N/A
12
N/A
Vanadium
1.7
N/A
N/A
1.7
2.0
N/A
N/A
N/A
N/A
2.1
N/A
2.2
N/A
Zinc
17000
16800
6437
15000
15000
14150
4809
13125
3752
13514
8749
10229
7849
a All results in mg/kg; N/A = not applicable
b Tire crumb rubber at one field had a lead concentration of 308 mg/kg. The average is 26 mg/kg without that field included.
23
-------
2.4.3.3 SVOCs
Tire crumb rubber from recycling plants and tire crumb rubber infill from synthetic turf fields was
quantitatively analyzed for 39 target SVOCs by solvent extraction and gas chromatography/'tandem mass
spectrometry (GC/MS/MS) analysis. An additional 10 target SVOCs were analyzed non-quantitatively
by liquid chromatographv/time-of-flight mass spectrometry (LC/TOFMS). Target analytes included
PAHs, phthalates, other tire rubber chemicals or degradates, and several chemicals previously reported
in other studies. Most extractable target SVOC analytes were measurable above the detection limit in all
samples.
• Average extractable SVOC measurement results for samples collected at recycling plants vs.
synthetic turf fields and analyzed by GC/MS/MS include pyrene (18 vs. 12 mg/kg),
benzo[a]pyrene (0.74 vs. 0.78 mg/kg), benzothiazole (79 vs. 11 mg/kg), 4-tert-octylphenol (30
vs. 9.8 mg/kg) and bis(2-ethylhexyl) phthalate (12 vs. 43 mg/kg).
• Average measurement results are shown in Figure 2-5 for select phthalates and in Figure 2-6 for
benzothiazole, 4-tert-octylphenol, aniline, and n-hexadecane. Non-quantitative results are
reported for two thiazoles and three cyclohexylamines in Figure 2-7.
~ Recycling plants P Indoor fields ¦ Outdoor fields
Figure 2-5. Average measurement results for phthalates in solvent extraction samples from tire
crumb rubber collected at tire recycling plants (n=9), indoor synthetic turf fields (n=15), and
outdoor synthetic turf fields (n=25).
24
-------
¦ Recycling plants ¦ Indoor fields B Outdoor fields
Benzothiazole
4-tert-Octylphenol
Aniline
n-Hexadecane
Figure 2-6. Average measurement results for select semivolatile organic compounds in solvent
extraction samples from tire crumb rubber collected at tire recycling plants (n=9), indoor
synthetic turf fields (n=15), and outdoor synthetic turf fields (n=25).
~ Recycling plants H Indoor fields B Outdoor fields
Figure 2-7. Average relative chromatographic peak area count results for select semivolatile
organic compounds in solvent extraction samples from tire crumb rubber collected at tire
recycling plants (n=9), indoor synthetic turf fields (n=15), and outdoor synthetic turf fields (n=25).
These results are not quantitative, but compound identities were confirmed.
25
-------
• Maximum values for pyrene, benzo[a]pyrene, benzothiazole, 4-tert-octylphenol, and bis(2-
ethylhexyl) phthalate in synthetic turf field samples were 25, 3.0, 54, 33, and 170 mg/kg,
respectively.
• Many analytes on the more volatile end of the SVOC spectrum were found at higher levels in
'fresh' material from tire recycling plants than found in synthetic turf field infill samples. If
additional research confirmed this trend through longitudinal assessments at individual fields, a
possible explanation for the lower levels found at synthetic turf fields could include volatilization
from the rubber on the fields over time and, possibly, rain- or irrigation-driven leaching.
• Many of the less volatile SVOC analytes, including the five- and six-ring PAH chemicals,
showed little to no difference between average concentrations in tire recycling plant samples and
average concentrations in synthetic turf field samples.
• Several phthalate chemicals were found, on average, at higher levels in samples from synthetic
turf fields than in 'fresh' material coming from tire recycling plants. If additional research
confirmed this trend of higher levels of phthalates at individual fields, possible explanations
could be: atmospheric deposition; track-in by field users or releases from shoes, clothing or other
personal products; presence in and release from other synthetic turf field materials; or from
chemical treatments applied to fields.
• Examples of measurement results and comparisons between tire recycling plant samples and
synthetic turf field samples are shown in Figure 2-8 for pyrene and benzothiazole.
Pyrene Benzothiazole
25
100
20
O)
O)
O)
25
Recycling Plants Fields Recycling Plants Fields
Figure 2-8. Example comparison of GC/MS/MS extract SVOC analysis results (mg/kg)
between tire rubber collected from tire recycling plants and tire crumb rubber infill
composite samples from synthetic turf fields for pyrene and benzothiazole.
• Table 2-5 shows a comparison of selected average extractable SVOC measurement results in this
study compared to measurements obtained in other studies. The comparison studies were
restricted to those analyzing uncoated tire crumb rubber from synthetic turf fields or recycling
plants. In some cases, assumptions were made in other studies' results to allow a comparison of
values, for example substitution of values below detection limit results to calculate study
averages.
26
-------
Table 2-5. Comparison of Tire Crumb Rubber Extractable SVOC Analysis Results Across Multiple Studies8
Chemical
This Study
2019-
Rccycling
Plants
Mean
(n=9)
IMarsili
2014-
New
Unused
Mean
(n=5)
Gomes
2010-
Rccyclinjj
Plant
Result
(n=l)
This Study
2019 -
Indoor
Fields Mean
(n=15)
Saloncnb
2015-
Indoor
Fields
Mean
(n=4)
This Study
2019-
Outdoor
Fields Mean
(n=25)
Cclciro'
2018-
Outdoor
Fields
Mean
(n=15)
RIVMd
2017-
Outdoor
Median
(n=9.1 fields
or n=7 fields)
IMarsili
2014-
Outdoor
Fields
Mean
(n=4)
Ruffino
2013-
Outdoor
Fields
Mean
(n=4)
Menichini
2011 -
Outdoor
Fields
Mean
(n=5)
Zhang'
2008-
Outdoor
Fields Mean
(n=4 fields,
n=7 samples)
Phenanthrene
3.6
0.74
1.4
4.8
6.0
0.76
0.75
<0.6
0.34
N/A
N/A
1.2
Fluoranthene
6.1
2.4
4.5
6.2
9.9
3.5
3.5
3.4
1.4
N/A
N/A
4.9
Pyrene
18
5.2
14
19
26
8.8
8.0
7.5
4.0
22
6.6
6.3
Benzo[a]pyrene
0.74
0.25
1.2
0.98
1.4
0.66
1.0
<1.1
0.26
0.96
3.6
2.0
Benzo [ghijperylene
1.3
0.55
<0.08
1.6
5.0
1.1
3.3
4.1
0.40
2.5
N/A
2.3
Benzothiazole
79
N/A
N/A
19
N/A
5.6
1.9
2.7
N/A
N/A
N/A
N/A
Dibutyl phthalate
0.68
N/A
N/A
2.9
N/A
0.63
1.6
N/A
N/A
N/A
N/A
N/A
Bis(2-ethylhexyl)
phthalate
12
N/A
N/A
65
N/A
29
8.7
7.6
N/A
N/A
N/A
N/A
Aniline
3.8
N/A
N/A
1.2
N/A
0.38
N/A
N/A
N/A
N/A
N/A
N/A
4-tert-octylphenol
30
N/A
N/A
20
N/A
3.5
N/A
4.5
N/A
N/A
N/A
N/A
n-Hexadecane
3.6
N/A
N/A
2.2
N/A
0.20
N/A
N/A
N/A
N/A
N/A
N/A
Naphthalene
1.4
0.88
0.16
0.067
0.28
0.014
0.038
N/A
0.50
N/A
N/A
0.20
1 -Methylnaphthalene
1.6
N/A
N/A
0.12
N/A
0.0085
N/A
N/A
N/A
N/A
N/A
N/A
2-Methylnaphthalene
1.8
N/A
N/A
0.20
N/A
0.016
N/A
N/A
N/A
N/A
N/A
N/A
Acenaphthylene
0.37
N/A
N/A
0.090
0.70
0.020
0.15
N/A
N/A
N/A
N/A
N/A
Fluorene
0.37
5.6
0.12
0.43
0.54
0.036
0.029
N/A
2.6
N/A
N/A
0.35
Anthracene
0.59
0.12
0.13
1.2
0.64
0.13
0.13
<0.5
0.075
N/A
N/A
0.037
1 -Methylphenanthrene
1.4
N/A
N/A
2.8
N/A
0.87
N/A
N/A
N/A
N/A
N/A
N/A
2 -Methylphenanthrene
1.4
N/A
N/A
5.9
N/A
1.2
N/A
N/A
N/A
N/A
N/A
N/A
3 -Methylphenanthrene
2.1
N/A
N/A
4.2
N/A
1.2
N/A
N/A
N/A
N/A
N/A
N/A
Benz(a)anthracene
1.1
0.72
1.3
2.3
1.3
2.2
1.0
<0.9
0.14
10
0.37
0.59
Chrysene
4.3
1.9
2.8
3.4
4.5
2.0
1.2
1.3
0.68
2.6
2.1
2.4
Benzo(b)fluoranthene
1.6
6.8
<0.08
1.6
1.3
1.2
1.3
N/A
3.7
3.8
N/A
1.1
Benzo(k)fluoranthene
0.44
0.56
<0.08
0.58
0.37
0.38
0.42
<0.5
1.1
1.9
N/A
1.5
Benzo(e)pyrene
1.7
N/A
N/A
2.4
N/A
1.6
N/A
2.8
N/A
N/A
N/A
N/A
Coronene
0.82
N/A
N/A
0.69
N/A
0.45
N/A
N/A
N/A
N/A
N/A
N/A
Dibenzothiophene
0.42
N/A
N/A
0.66
N/A
0.096
N/A
N/A
N/A
N/A
N/A
N/A
27
-------
Table 2-5 Continued
Chemical
This Studv
IMarsili
Gomes
This Studv
Saloncnb
This Studv
Celeiro'
RIVMd
IMarsili
Ruffino
Mcnichini
Zhang'
2019-
2014-
2010-
2019 -
2015-
2019-
2018-
2017-
2014-
2013-
2011 -
2008-
Rccycling
New
Rccvcling
Indoor
Indoor
Outdoor
Outdoor
Outdoor
Outdoor
Outdoor
Outdoor
Outdoor
Plants
Unused
Plant
Fields Mean
Fields
Fields Mean
Fields
Median
Fields
Fields
Fields
Fields Mean
Mean
Mean
Result
(n=15)
Mean
(n=25)
Mean
(n=9.1 fields
Mean
Mean
Mean
(n=4 fields,
(n=9)
(n=5)
(n=l)
(n=4)
(n=15)
or n=7 fields)
(n=4)
(n=4)
(n=5)
n=7 samples)
Dimethyl phthalate
0.04
N/A
N/A
065
N/A
0.004
N/A
N/A
N/A
N/A
N/A
N/A
Diethyl phthalate
0.091
N/A
N/A
1.5
N/A
0
2.2
N/A
N/A
N/A
N/A
N/A
Diisobutyl phthalate
0.50
N/A
N/A
2.7
N/A
0.36
2.5
<0.5
N/A
N/A
N/A
N/A
Benzyl butyl phthalate
0.64
N/A
N/A
2.4
N/A
0.44
0.07
N/A
N/A
N/A
N/A
N/A
Di-n-octyl phthalate
0.32
N/A
N/A
0.44
N/A
0.13
N/A
N/A
N/A
N/A
N/A
N/A
" All results in mg/kg; N/A = not applicable
bFor the several values that were below the limit of detection, one-half the limit of detection was substituted for calculating a mean result.
0 Mean values reported in Celeiro et al. (2018) Table 2 were based only on the reported (non-missing) values. It was assumed that the missing values were non-detects. A
substitution of one-half the lowest reported value was made for missing results to calculate overall means for this table. Mean results in this table differ from means in Celeiro et
al., as a result of the substitutions.
dThis study included 546 samples from 91 fields for many PAHs and two phthalates [bis(2-ethylhexyl) phthalate and diisobutyl phthalate]; 43 samples from 7 fields for the
remaining phthalates; and 7 samples from 7 fields for several PAHs, phenols, and thiazoles.
e Substituted detection limits for non-detects.
28
-------
• In general, most measurements for outdoor fields in this study were within or near to a range of
measurements from other studies. Benzothiazole and bis(2-ethylhexyl) phthalate were found at
higher levels in this study compared to two recent studies. There were fewer comparable studies
with results for indoor fields or recycling plants. No directly comparable data were found for
some of this study's target analytes, and some studies reported results for SVOC analytes that
were not quantitatively analyzed in this study.
• Ten additional target SVOCs were analyzed non-quantitatively by liquid chromatography/time-
of-flight mass spectrometry (LC/TOFMS) following solvent exchange from the extracts used for
GC/MS/MS analyses. These analyses showed the presence of 2-mercaptobenzothiazole, 2-
hydroxybenzothiazole, and three cyclohexylamine compounds in 100% of the recycling plant
samples and >70% of the synthetic turf field samples.
2.4.3.4 Field Characteristics and Differences in Chemical Substance Levels
In addition to examining differences in chemical measurements from tire crumb rubber samples taken at
tire recycling plants and synthetic turf fields, the research design allowed exploratory analysis of
potential differences in chemical measurements at synthetic turf fields and their association with other
synthetic turf field characteristics, including:
• outdoor versus indoor field locations,
• the age of fields (installation year age groups 2004 - 2008, 2009 - 2012, 2013 - 2016), and
• across the four U.S. census regions (Northeast, South, Midwest, West).
29
-------
Outdoor us. Indoor Fields - Twenty-five study fields were outdoor synthetic turf fields, and 15 fields
were indoor fields.
• No statistically significant differences in metal concentrations were observed in tire crumb
rubber infill from outdoor fields versus indoor fields.
• Most extractable SVOCs were found at statistically significant higher levels (p-values < 0.05;
often < 0.0001) in tire crumb rubber infill from indoor fields than outdoor fields. Average SVOC
levels were 1.5 to 10 times higher in tire crumb rubber infill from indoor fields than outdoor
fields.
• The more volatile SVOCs had higher indoor/outdoor concentration ratios than less volatile
SVOCs. A likely contribution to these differences is increased weathering at outdoor locations,
including sunshine, ventilation rates and rainfall.
• Figure 2-9 shows examples of the observed differences in select metal and SVOC measurements
in tire crumb rubber infill from outdoor and indoor synthetic turf fields.
Zinc 4-tert-Octylphenol
20000
CT)
O) 16000
o>
O)
12000
Indoor Outdoor Indoor Outdoor
Pyrene Benzo(a)pyrene
20
O)
U)
O)
Indoor Outdoor Indoor Outdoor
Figure 2-9. Comparison of analysis results (mg/kg) between tire crumb rubber
infill composite samples from indoor and outdoor synthetic turf fields for zinc,
4-tert-octylphenol, pyrene and benzo[a]pyrene.
Field Age - An assessment of differences in chemical substance concentrations was performed for all
fields across the installation age groups: 2004 - 2008 (n=l 1), 2009 - 2012 (n=18), and 2013 - 2016
(n=ll).
30
-------
Some differences were observed for metals, but generally not in a monotonically decreasing or
increasing direction.
Assessing differences in extractable SVOC concentrations among the three age groups was
complicated, because most indoor fields were in the two older age groups, and the
indoor/outdoor differences were relatively large.
When analyses were restricted to outdoor fields only, many SVOCs had statistically significant
different (p-values < 0.05) concentrations among age groups, with an inverse relationship of
decreasing average SVOC levels with increasing field installation age group. These results
provide supporting evidence for the contribution weathering might be expected to play in
changes to concentrations of some SVOCs in tire crumb rubber used on fields.
Figure 2-10 shows examples of the observed differences in select metal and SVOC
measurements in tire crumb rubber from recycling plants versus synthetic turf fields, outdoor
versus indoor fields, and field installation age groups.
Zinc
20000-
C)16000-
e
QufcfcXtfFMcK
Benzothiazole
indoof Fiotds
2016 20GQ-2012 2004 - 2008 2013 - 2016 20Q9-2Q12 2004 - 200&
Age Group
Pyrene
25-
20-
QB
£
2016 2009 - 2012 2004 -2006 2013-2016 2009-2012 2C04 - 2006
Age Group
Sum15PAH
IntfoerFitito OA&xw
£
i t
2016 2009 - 2012 2004 - 2009 2013-2016 20W-2012 20CM-2008
Age Group
200®-2012 2004 - 2008 20*3 - 2016 2000 - 2012 2004 - 2000
Age Group
Figure 2-10. Analysis results (mg/kg) for tire crumb rubber from tire recycling
plants and tire crumb rubber infill composite samples from synthetic turf fields
with different characteristics by age group. [Suml5PAH = Sum of 15 of the 16 EPA
'priority' PAHs, including Acenaphthylene. Anthracene, Benz[a]anthracene, Benzo[a]pyrene,
Benzo(b)fluoranthene, Benzo[ghi]peiylene, Benzo(k)fluoranthene, Chiysene, Dibenz[a,h|anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene. Phenanthrene, Pyrene]
31
-------
Field Region - Synthetic turf fields were recruited across the four U.S. census regions, including the
Northeast (n = 9 fields), South (n = 13 fields), Midwest (n = 8 fields) and West (n = 10 fields).
• Few consistent differences were observed for metals or extractable SVOCs in tire crumb rubber
infill samples collected from fields across the four U.S. census regions.
• Analysis by field region was complicated, because there was a much higher percentage of indoor
fields in the Midwest region, and a lower percentage of indoor fields in the South region. It was
also limited by the relatively small numbers of fields in each region.
• Multivariate analyses (statistical analyses that consider field type, age, and location together)
showed statistically significant interactions (p-values < 0.05) among field characteristics,
including field region, for some chemicals associated with tire crumb rubber, suggesting that
differences between regions cannot be ruled out.
2.4.3.5 Chemical Variability Within and Between Recycling Plants and Fields
The research was designed to provide information for assessing the variability of chemicals associated
with tire crumb rubber within and between recycling plants and within and between synthetic turf fields.
Three samples were collected at each recycling plant. For five synthetic turf fields, seven samples
collected at different locations on the field were analyzed to assess variability within fields.
• Variability of metals in tire crumb rubber collected at tire recycling plants differed by metal. For
example, zinc and chromium had greater between-plant variability than within-plant variability.
On the other hand, arsenic, cadmium, cobalt and lead exhibited greater within-plant variability.
• For metals in synthetic turf field infill, higher between-field variability was measured for cobalt
and zinc, while arsenic, cadmium, chromium, and lead had higher within-field variability.
• Variability of extractable SVOCs in tire crumb rubber collected at tire recycling plants differed
by SVOC. For example, pyrene, benzothiazole, and 4-tert-octylphenol had greater between-plant
variability than within-plant variability, while benzo[a]pyrene and bis(2-ethylhexyl) phthalate
exhibited greater within-plant variability.
• For SVOCs in synthetic turf field infill, there was uniformly higher between-field variability than
within-field variability, with the amount of total variance accounted for by between-field
differences typically greater than 75%.
• The variability in measurements of zinc, pyrene, and benzothiazole in samples from tire
recycling plants and synthetic turf fields are shown as examples in Figure 2-11.
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Zinc
Zinc
2&X»
20000
15000
2MOO
20000
1M00
A6CDEFGH I
Recycling Planl ID
Pyrene
16 20 26
Field ID
Pyrene
A&CDEF GN I
Recycling Planl ID
Benzotliiazole
16 20 28
Re Id ID
Bervzothiazole
so
P«o
M
Recycling Plan? ID
F«ld ID
Figure 2-11. Within-plant and within-field variability of zinc, pyrene and benzothiazole
measurements at each of the nine tire recycling plants (left side) and each of the five
synthetic turf fields (right side). Within-plant variability shows the variability in the
three samples taken at each tire recycling plant and within-field variability shows the
variability in the seven individual samples taken at each of the five synthetic turf fields.
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2.4.3.6 SVOC Suspect Screening and Non-Targeted Chemical Analysis
In addition to targeted chemical analyses of extractable SVOCs in tire crumb rubber, suspect screening
and non-targeted analyses were applied to help elucidate the potentially-wider range of organic
chemicals associated with tire crumb rubber material.
Through a review of published literature and reports, 89 chemicals were selected a-priori for suspect
screening; these chemicals were reported in previous tire crumb rubber studies or were potentially an
ingredient, component, or degradate in tire rubber. Suspect screening analyses were performed by
LC/TOFMS in both positive and negative ionization modes for solvent extracts from tire crumb rubber
samples from recycling plants and tire crumb rubber infill samples from synthetic turf fields.
• Recycling plant samples had, on average, 12 suspect screening chemical matches; outdoor fields
had, on average, 10 matches; and indoor fields had, on average, 11 suspect matches.
• Several of the tentatively-identified chemicals are potential tire rubber ingredients or degradates.
Examples of chemicals tentatively identified through suspect screening include 2,2,4-Trimethyl-
1,2-dihydroquinoline (TMQ, a tire rubber antioxidant) and other potential tire rubber chemicals
that may be used as rubber vulcanization accelerators, rubber antioxidants or rubber
antiozonants, such as:
o N,N'-Diphenyl-p-phenylenediamine (DPPD),
o N,N'-Ditolyl-p-phenylenediamine (DTPD),
o N,N-Dicyclohexyl-2-benzothiazolesulfenamide (DCBS),
o N-tert-Butyl-2-benzothiazolesulfenamide (TBBS), and
o N-Isopropyl-N'-phenyl-p-phenylenediamine (IPPD).
• It is important to emphasize that the suspect screening results are tentative and require further
confirmation through analysis of chemical standards.
Non-targeted assessment was performed for a subset of recycling plant tire crumb rubber samples and
synthetic turf field tire crumb rubber infill samples. Both GC/MS and LC/TOFMS methods were applied
to solvent extracts and emission samples for SVOCs, and GC/TOFMS methods were applied to
emission samples for VOCs. This approach yielded only highly-tentative and non-quantitative chemical
identifications and should be considered only the first step of a multi-step process that would ideally be
used to confirm chemical identities and, eventually, lead to quantitative analyses.
• GC/MS analysis of SVOC solvent extracts from tire recycling plant samples yielded 49 tentative
chemical matches with unique names. Outdoor field samples had 53 tentative chemical matches
with unique names, and indoor field samples had 54 tentative chemical matches with unique
names.
• LC/TOFMS analysis of SVOC solvent extracts from tire recycling plant samples had 295
tentative chemical matches in positive ionization mode and 86 in negative ionization mode.
Outdoor field samples had 228 tentative chemical matches in positive ionization mode and 101
matches in negative ionization mode; and indoor field samples had 293 tentative chemical
matches in positive ionization mode and 91 matches in negative ionization mode.
• GC/TOFMS analysis of VOCs in 60 °C emission tests of recycling plant samples had 151
tentative chemical matches with unique names. Outdoor field samples had 115 tentative
chemical matches with unique names and indoor field samples had 136 tentative chemical
matches with unique names.
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• It is important to emphasize that the non-targeted analysis results, while illustrating the presence
of numerous organic chemicals that were not target analytes, are highly tentative and require
further confirmation through analysis of chemical standards. Due to the tentative nature of the
results, no attempts were made to try to identify toxicity reference information for these
chemicals.
2.4.3.7 Microbiological
Tire crumb rubber infill samples collected from synthetic turf fields were analyzed for select targeted
microbial genes, and non-targeted analysis was performed to characterize a wider microbial community.
• Targeted analysis was performed to determine concentrations of the 16S rRNA gene (an
indicator of total bacteria), a protein gene for the Staphylococcus aureus bacteria, and a gene for
methicillin resistance in bacteria (mecA methicillin resistance gene).
• Every sample from the 40 fields was positive for 16S rRNA genes. A total of 17 fields (42%)
had at least one sample with quantifiable Staphylococcus aureus genes, while 28 fields (70%)
had a least one positive sample for the methicillin resistance gene.
• Outdoor fields had statistically significant higher (p-value < 0.0001) quantities of 16S rRNA
genes than indoor fields, while indoor fields had statistically significant higher (p-values
< 0.0001) quantities of Staphylococcus aureus and methicillin resistance genes than outdoor
fields.
• When considering samples from outdoor fields only, older fields had statistically significant
increased (p-value < 0.0001) concentrations of 16S rRNA genes than younger fields, but field
age was not associated with concentrations of Staphylococcus aureus or methicillin resistance
genes.
• For non-targeted microbial analysis, 1,424 different bacterial types were found across the 40
fields.
• At this time, there are no analogous non-targeted bacterial assessment studies available for grass
fields for comparison. Small studies have previously found more colony forming units for some
bacteria at grass fields compared to synthetic turf fields.
2.4.4 Tire Crumb Rubber Exposure-Related Availability Characterization
2.4.4.1 VOC Emissions
The release of chemicals associated with tire crumb rubber into the air is, potentially, an important
mechanism leading to human exposure. Dynamic small-chamber emissions testing was performed to
measure emission factors for 31 VOC target analytes in tire crumb rubber from recycling plants and tire
crumb rubber infill from synthetic turf fields. All samples were tested at both 25 °C and 60 °C, after a
24-hour equilibration period.
• For tests conducted at 25 °C, more VOCs were measurable above limits of detection for tire
crumb rubber from recycling plants than for tire crumb rubber infill from synthetic turf fields.
• Analytes with > 60% of the measurements above the limit of detection in 25 °C emissions tests
of recycling plant samples included methyl isobutyl ketone, benzothiazole, toluene, styrene, m/p-
xylenes, and o-xylene. For synthetic turf field samples, analytes with > 60% of the measurements
above the limit of detection included benzothiazole and o-xylene.
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• Median 25 °C emission factors from synthetic turf field infill samples included 15 ng/g/h for
benzothiazole, 0.87 ng/g/h for methyl isobutyl ketone, and 0.044 ng/g/h for the sum of BTEX
compounds (benzene, toluene, ethylbenzene, m/p-xylenes, and o-xylene).
• VOC emission factors at 25 °C were higher in tire recycling plant samples than synthetic turf
field samples. For example, mean benzothiazole emission factors were 6 times higher in
recycling plants, and the emission factors for the sum of BTEX compounds were 5.5 times
higher.
• For tests conducted at 60 °C, more VOCs were measurable above limits of detection than at
25°C.
• Examples of median 60 °C emission factors from synthetic turf field infill samples included 68
ng/g/h for benzothiazole, 34 ng/g/h for methyl isobutyl ketone, 15 ng/g/h for formaldehyde, and
0.40 ng/g/h for styrene.
• VOC emission factors at 60 °C were higher in tire recycling plant samples than synthetic turf
field samples. For example, mean methyl isobutyl ketone emission factors were 3.3 time higher
in recycling plant samples, benzothiazole emission factors were 3.9 times higher, formaldehyde
emission factors were 2.5 times higher, and styrene emission factors were 2.4 times higher.
Examples of the differences in VOC emission factors between recycling plant and synthetic turf
field samples are shown in Figure 2-12 for formaldehyde and methyl isobutyl ketone.
Formaldehyde Methyl Isobutyl Ketone
T emperature=60°C T emperatu re=60°C
160
120
40
40
Recycling Plants Fields Recycling Plants Fields
Figure 2-12. Comparison of volatile organic compound 60 °C emission factor results
(ng/g/h) between tire rubber collected from tire recycling plants and tire crumb rubber
infill composite samples from synthetic turf fields for formaldehyde and methyl
isobutyl ketone.
• Many target VOC compounds had higher emission factors in emission experiments performed at
60 °C than 25 °C. Examples of these differences are shown for benzothiazole and styrene in
Figure 2-13.
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120
Benzothiazole
Styrene
en 60
25 60 25 60
Temperature (°C) Temperature (°C)
Figure 2-13. Comparison of volatile organic compound 25 °C and 60 °C emission
factor results (ng/g/h) for tire crumb rubber infill collected from synthetic turf fields
for benzothiazole and styrene.
• Several compounds did not show appreciable differences in emissions at the two temperatures,
including several of the BTEX chemicals. It appeared that some VOCs were driven off the tire
crumb during the 24-hour equilibration period in the test chamber at 60 °C, prior to sample
collection (i.e., there was also some evidence to support this in the small number of emissions
time series tests performed). This may have implications for understanding whether some
chemicals may be found at the surface of tire crumb rubber particles, perhaps from atmospheric
absorption, versus chemicals intrinsic to the rubber material. More experimental work would be
needed to better understand these dynamics.
• Most VOC chemicals followed patterns similar to the SVOC extract samples with regard to
differences associated with different field characteristics. Emission factors were higher for
indoor fields versus outdoor fields. Several VOCs also showed an inverse association of
decreasing emission factors with increasing field installation age, when the analysis was limited
to outdoor fields.
2.4.4.2 SVOC Emissions
Dynamic micro-chamber emissions testing was performed to measure emission factors for 39 SVOC
target analytes in tire crumb rubber from tire recycling plants and tire crumb rubber infill from synthetic
turf fields. All samples were tested at both 25 °C and 60 °C after a 24-hour equilibration period with
analysis by GC/MS/MS. An additional 10 SVOC analytes were analyzed non-quantitatively by
LC/TOFMS in the 60 °C samples only.
• For tests conducted at 25 °C, approximately 50% of the target GC/MS/MS SVOCs were
measurable above limits of detection in at least 60% of the samples. Rates of detection were
higher for the more volatile SVOCs and lower for the less volatile SVOCs.
• Emission factors for SVOCs at 25 °C in synthetic field tire crumb rubber infill were low.
Examples of median 25 °C emission factors included 1.8 ng/g/h for benzothiazole, 0.16 ng/g/h
for aniline, and 0.082 ng/g/h for 4-tert-octylphenol.
• Emission factors at 25 °C were higher for 10 of the 18 SVOCs that had > 60% of the samples
above the detection limits in recycling plant samples versus synthetic turf fields. For example,
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mean benzothiazole emission factors were 9.8 times higher in recycling plant samples and
aniline emission factors were 10 times higher.
For tests conducted at 60 °C, approximately 70% of the target SVOCs were measurable above
limits of detection in at least 60% of the samples. Rates of detection remained higher for the
more volatile SVOCs and lower for the less volatile SVOCs. The 5- and 6-ring PAH compounds,
for example, were rarely measured above the detection limits.
Examples of median 60 °C emission factors from synthetic turf field infill samples included 18
ng/g/h for benzothiazole, 0.81 ng/g/h for aniline, 5.1 ng/g/h for 4-tert-octylphenol, and 0.22
ng/g/h for pyrene.
Emission factors at 60 °C were higher for most SVOCs in tire recycling plant samples versus
synthetic turf fields. For example, mean benzothiazole emission factors were 15 times higher in
recycling plant samples, aniline emission factors were 6.6 times higher and 4-tert-octylphenol
factors were 3.4 times higher. Examples of the differences between recycling plant and synthetic
turf field emission factors are shown in Figure 2-14 for the sum of 15 PAH analytes and 4-tert-
octylphenol.
Sum15PAH
Te m pe ratu re=60° C
4-tert-Octylphenol
Temperature=60°C
20
o>
c
10
Recycling Plants Fields Recycling Plants Fields
Figure 2-14. Comparison of semivolatile organic compound (SVOC) 60 °C emission
factor results (ng/g/h) between tire rubber collected from tire recycling plants and
tire crumb rubber infill composite samples from synthetic turf fields for Suml5PAH and
4-tert-octylphenol. [Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including
Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene,
Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
• Most target SVOCs had higher emission factors in emission experiments performed at
60 °C than at 25 °C. Examples are shown for the sum of 15 PAH analytes and 4-tert-octylphenol
in Figure 2-15.
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Sum15PAH 4-tert-Octylphenol
7,5
2.5
0.0
25 60 25 60
Temperature (°C) Temperature (°C)
Figure 2-15. Comparison of semivolatile organic compound (SVOC) 25 °C and 60 °C
emission factor results (ng/g/h) for tire rubber infill collected from synthetic turf fields
for Suml5PAH and 4-tert-octylphenol.[Suml5PAH = Sum of 15 of the 16 EPA 'priority'
PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene,
Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
• Most SVOC emission factors were higher for indoor fields versus outdoor fields. Many SVOCs
also showed an inverse association with increasing field installation age group, when the analysis
was limited to outdoor fields.
• Benzothiazole was analyzed in both VOC and SVOC emissions testing. Higher maximum levels
were observed in the SVOC testing than in the VOC testing. The VOC upper benzothiazole
emission rates may be underestimated due to approaching upper calibration limits during
analysis. Other differences may be the result of testing in two different chamber systems with
different characteristics (including chamber wall surface area).
2.4.4.3 Metals Bioaccessibility
Bioaccessibility testing was performed for 20 metal target analytes in 27 tire crumb rubber samples from
recycling plants and tire crumb rubber infill samples from synthetic turf fields using three artificial
fluids (gastric, sweat with sebum, and saliva). The amount of each metal released in each artificial fluid
was determined, and the percentage of the total amount of metal in the tire crumb rubber that was
released was calculated (i.e., % in vitro bioaccessibility) for 19 metals.6
• For metals in tire crumb samples, in vitro bioaccessibility was the highest in artificial gastric
fluid followed by sweat with sebum, while metals' bioaccessibility in artificial saliva was near
zero, based on both bioaccessible metal concentrations in artificial fluid extracts and calculated
percent in vitro bioaccessibility.
• Among the metals tested for bioaccessibility, zinc had the highest median concentrations in all
three artificial biofluid extracts, at 129, 11, and 0.72 mg/kg in artificial gastric fluid, sweat with
sebum, and saliva, respectively.
6 Mercury was not measured by ICP/MS in the tire crumb samples; therefore, percent bioaccessibility could not be calculated
for mercury.
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• Manganese had the highest median percent in vitro bioaccessibility values in artificial gastric
fluid (12%) and sweat with sebum (1.5%). In saliva, magnesium had the highest median percent
in vitro bioaccessibility at 0.2%.
• For lead in tire crumb samples, the median (range) bioaccessible concentrations were 0.29 mg/kg
(0.056-2.8 mg/kg), 0 mg/kg (0-0.19 mg/kg), and 0 mg/kg (0-0.048 mg/kg) in artificial gastric
fluid, sweat with sebum, and saliva, respectively. Median (range) percent bioaccessibility values
for lead were 1.9% (0.2-13.5%), 0% (0-1.9%), and 0% (0—0.5%) in artificial gastric fluid, sweat
with sebum, and saliva, respectively.
• For lead, average gastric fluid bioaccessible concentrations and % bioaccessibility were
significantly higher (p-values < 0.001) in synthetic turf field infill samples compared to tire
crumb rubber from recycling plants (0.54 vs. 0.18 mg/kg; 3.2% vs. 1.8%). The observed higher
lead concentrations in artificial gastric fluid from field samples could in part be driven by the
higher lead concentrations in the field samples, as reported earlier in the section. Another
possible explanation for the observed higher bioaccessibility from field samples is that some of
the lead in synthetic turf field infill could come from external sources and be available on the
surface of the infill rubber.
• Based on the findings, metals in tire crumb samples had low bioaccessibility in artificial gastric
fluid, saliva, and sweat with sebum when compared to a default assumption of 100%
bioaccessibility.
• Based upon available literature, this is the largest study on in vitro bioaccessibility of metals in
tire crumb samples, in terms of number of samples tested and number of metals evaluated.
• Our results are generally consistent with a previous scoping study conducted by EPA for lead
(U.S. EPA, 2009) and a 2017 report by the Netherlands National Institute for Public Health and
the Environment (cadmium, cobalt, lead; RIVM, 2017). However, caution should be taken while
interpreting and comparing bioaccessibility results across studies.
2.4.5 Toxicity Reference Information
One objective of the effort to characterize tire crumb rubber materials was to identify and collate
existing toxicity reference information for select chemical constituents. To achieve this goal, a list of
chemical constituents was developed as part of the Literature Review/Gaps Analysis (LRGA), based on
chemicals identified in the various studies reviewed and supplemented by additional chemicals
measured in this study. Searches were performed for a total of 355 chemicals in 11 different toxicity
reference data sources.
• The percentage of chemicals with toxicity reference information available in the 11 extant
reference data sources ranged from 7% to 28%.
• A total of 101 chemicals were found in EPA's Integrated Risk Information System (IRIS), 96
chemicals were found in the International Agency for Research on Cancer (IARC) references, 89
in California Occupational Safety and Health (CalOSHA) sources, 78 in sources from the
National Institute for Occupational Safety and Health (NIOSH), 83 from the American Council
of Government Industrial Hygienists, and 81 in OSHA sources.
• More information was available when narrowing to a subset of constituents in the target analyte
list. For 95 constituents on the target list that were examined, toxicity reference information was
available for 78 of them.
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• Not all of the chemicals included in the toxicity reference information search had large or even
measurable concentration results in tire crumb rubber analyses portion of this study.
2.5 Research Limitations
2.5.1 Research Design Constraints
A representative sampling design was considered, but the time required to develop and implement a
study based on a national sampling frame of synthetic turf fields was beyond the scope of the research
effort. Another design constraint was a decision to focus characterization research on the recycled tire
crumb rubber infill and not to include other synthetic turf field materials (e.g., synthetic grass blades and
backing material) due to the expanded scope that would be needed for a high-quality characterization of
all these materials.
2.5.2 Planned Work Not Completed in this Part of the Study
Not all research goals for this portion of the study were completely met. Bioaccessibility measurements
were planned for SVOCs using three simulated biological fluids. However, there were no validated
methods for SVOCs; therefore, this work could not be done at the time of the sample analysis.
Quantitative analyses of approximately 10 extractable SVOC chemicals were planned for the liquid
chromatography/time-of-flight mass spectrometry (LC/TOFMS) analyses, but only non-quantitative
analyses were completed. The results from these non-quantitative analyses were still informative as to
the presence of select SVOCs and relative amounts and differences between recycling plants and fields,
and among fields with different characteristics.
2.5.3 Other Limitations
The research described in this report was exclusively aimed at synthetic turf fields with recycled tire
crumb rubber infill. While it may be desirable for reasons noted below to include other types of fields, it
was beyond the scope of this study to investigate other types of fields (e.g., natural grass, synthetic fields
with natural product infill, or synthetic fields with ethylene propylene diene terpolymer [EPDM] or
thermoplastic elastomer [TPE] infill). It was also beyond the scope of this part of the study to evaluate
the use of recycled tire crumb rubber as a soil amendment or natural grass top dressing. While there is
concern about chemical exposures resulting from the use of recycled tire and other materials in synthetic
fields, it is important to recognize that some of the chemicals are likely to be present in other types of
fields, including natural grass fields. For example, metals (including lead) and PAHs (including
benzo[a]pyrene) of potential concern at synthetic turf fields with tire crumb rubber infill are also often
found in surface soil in the United States and may be present at natural grass playing fields. Insecticides
and herbicides may be used on some natural grass fields, leading to exposures that may not be
experienced by synthetic turf field users. Because many recreational and sports field users spend time on
both natural grass and synthetic fields (either concurrently or during different life stages),
characterization of chemical and microbiological agents at all relevant field types and an understanding
of relative exposures across the different field types might be needed for risk assessment and
epidemiological investigations.
There are several potential limitations affecting the ability to interpret the laboratory chamber emission
test results. First, we selected 60 °C as an upper-bound temperature condition, but this selection was
based on sparse and incomplete information. In a report based on a field in Connecticut at a measured
air temperature of approximately 36 °C, the maximum field surface temperature for the grass fibers was
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69 °C, but the maximum crumb rubber temperature at a 1-inch depth was 44 °C (Milone & MacBroom,
2008). It is not clear which temperature is most relevant for emissions from the crumb rubber.
Information compiled from several studies and summarized in the Toronto Health Impact Assessment
showed field surface temperatures ranging from 47 to 78 °C for artificial turf with black infill on warm
to hot days in direct sunlight (Toronto Public Health, 2015). However, temperature measurements in the
infill itself were not reported. (The on-going California Office of Environmental Health Hazard
Assessment (Cal-OEHHA, 2017) study has performed a set of high-quality field and air temperature
measurements at multiple depths and heights above the field for up to 35 synthetic turf fields; these data
should be informative regarding potential temperature profiles potentially affecting emissions and
exposures. Second, we have highlighted later in the report some findings that may affect interpretation
of the laboratory chamber emissions test results. Several findings related to the emissions testing suggest
a better understanding of the dynamics of chemical emissions from tire crumb rubber is needed. Relating
the laboratory chamber results to actual field conditions is challenging. We noted that for some VOCs,
such as the benzene, toluene, ethylbenzene and xylene (BTEX) compounds, it appears that the chemicals
might be primarily surface absorbed from the atmosphere rather than intrinsic to the rubber in
substantial amounts; these VOCs were largely depleted during the 24-hour equilibration period in the
test chamber at 60 °C prior to air sample collection whereas, for example, the intrinsic VOC chemical
methyl isobutyl ketone was not. The chamber emission experiments may also be producing
measurements that overestimate long-term emissions occurring at fields, particularly for the SVOCs;
longer duration tests might improve our understanding of emissions as they occur at the fields. In
general, though, we believe the chamber experiments provided important information regarding
differences in emissions between 'fresh' material from recycling plants and tire crumb rubber infill at
synthetic turf fields, show the decreases in emission rates over time at outdoor fields, and highlight
important differences in emission rates at indoor versus outdoor fields.
Finally, data were not collected to directly address the potential for ecological exposure and risks
beyond performing chemical characterization of the tire crumb rubber material.
2.6 Future Research Recommendations
While this part of the study added considerable new information for better understanding tire crumb
rubber to inform exposure assessment for chemical substances and microbes at synthetic turf fields,
ongoing exposure research is being conducted and additional research could be performed to further
inform and improve future exposure and risk assessments.
• Given the complex nature of tire crumb, it is not
unexpected that many chemicals were observed during
characterization testing. The ability to resolve which, if
any, of those that were tentatively identified are
relevant for further evaluation is further complicated by
the limitations on toxicity information that may be
available for many chemicals. Approaches for whole
material toxicity testing, such as those used by the
National Toxicology Program, could be further
developed and applied for assessing potential effects of
the material.
Recommended Follow-up
Activities
• Approaches for whole material toxicity
testing, such as those used by the
National Toxicology Program, could be
further developed and applied for
assessing potential effects of the
material
• Further research to understand the
increased potential for exposure to
chemicals associated with tire crumb
rubber at indoor synthetic turf fields
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• Results in this study and other studies suggest that organic chemicals associated with recycled
tire crumb rubber infill can be higher at indoor synthetic turf fields as compared to outdoor
fields. Higher concentrations in, and emissions from tire crumb rubber, when combined with the
reduced ventilation rates at indoor fields, suggest that indoor field users may experience higher
exposures to some chemicals. Future studies might be directed at collection of more air and
exposure measurements at indoor facilities to assess the potential differences in exposures
between indoor and outdoor field users.
2.7 Conclusions
• Based upon available literature, this research effort represents the largest tire crumb rubber study
conducted in the United States, and the information and results from the effort will fill specific
data gaps about the potential chemical constituents found to be associated with recycled tire
crumb rubber infill material.
• This report provides new and additional data on tire crumb rubber characterization of samples
collected from 40 synthetic turf fields and 9 recycling plants located across the United States.
Extensive physical, chemical and microbiological characteristics of the tire crumb rubber material
obtained in this research will be useful for improving exposure estimation for individuals using
synthetic turf fields with recycled tire crumb rubber infill.
• As expected, a range of metals, organic chemicals, and bacteria was found to be associated with
recycled tire crumb rubber.
• These results are generally comparable to other studies characterizing tire crumb where available.
• While many chemicals are present in the recycled tire crumb rubber, exposure may be limited
based on what is released into air or biological fluids.
• The study is not a risk assessment; however, the results of the research described in this and
future reports should advance the understanding of exposure to inform the risk assessment
process. The study activities completed as part of this multi-agency research effort were not
designed, and are not sufficient by themselves, to directly answer questions about potential
health risks.
• Risk is a function of both hazard and exposure; therefore, improved understanding through this
research regarding what is present in the material and how individuals are exposed is critical to
understanding the risk. Ongoing exposure characterization research being performed under the
FRAP will further extend and improve our ability to apply the tire crumb rubber characterization
results included in this report in an exposure context.
Overall, we anticipate that the results from this multi-agency federal research effort, along with studies being
performed by other organizations, will be useful to the public and interested stakeholders for understanding the
potential for human exposure to chemicals of potential interest and concern found in recycled tire crumb rubber
infill material used on synthetic turf fields.
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3.0 Tire Crumb Rubber Characterization
Methods
3.1 Research Design Summary
As described in the Federal Research Action Plan (U.S. EPA, CDC/ATSDR, and CPSC, 2016a) and in
the research protocol, Collections Related to Synthetic Turf Fields with Crumb Rubber Infill (U.S. EPA
and CDC/ATSDR, 2016), this portion of the research was aimed at providing information and data for
characterizing tire crumb rubber used at synthetic turf fields. The tire crumb rubber characterization
study was designed to collect tire crumb rubber material from tire recycling plants and synthetic turf
fields around the United States and analyze the material in the laboratory for a wide range of metals,
volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs), as well as particle
and microbial characterizations. A schematic outline of the tire crumb rubber characterization research,
as implemented, is shown in Figure 3-1.
The research design included recruiting up to nine tire recycling plants that produce tire crumb rubber
for use on synthetic turf fields to provide tire crumb rubber material samples. The samples from the tire
recycling plants represents 'fresh' tire crumb rubber material newly manufactured from used tires that
has not undergone weathering and was collected for comparison with tire crumb rubber material from
synthetic turf fields, which had undergone weathering and active play. Tire recycling plants that use
both ambient production processes and cryogenic production processes were recruited for collection of
the tire crumb rubber samples. Samples were collected from three different flexible intermediate bulk
containers at each plant. These containers typically held one ton of tire crumb rubber for storage and
transport and were closed at the top to prevent rainwater intrusion. In most cases, the bulk containers
sampled were outdoors at the recycling plant. No researcher efforts were implemented to assess whether
storage conditions might affect the presence or concentrations of chemicals or microbes prior to
installation at synthetic turf fields.
The research design included recruiting up to 40 facilities with synthetic turf fields with tire crumb
rubber infill across the continental United States. Fields were recruited from across the four U.S. census
regions (Figure 3-2). The geographic extent of the recruitment was intended to provide a range of
material weathering conditions for outdoor fields and potentially, differences in tire crumb rubber source
material. Consideration of facility type (indoor vs. outdoor fields) was also integrated in the study design
at the facility identification and recruitment stage. Higher air concentrations of organic chemicals
potentially associated with tire crumb rubber have been measured in some studies of indoor facilities
compared to levels measured at outdoor fields. Stratification of tire crumb rubber characterization by
facility type could help determine whether the potential exposures vary by facility type and if so,
whether the variation is due to differential weathering and its effect on the amounts and types of
chemicals available for exposure or is a function of ventilation rates at indoor facilities. Although not an
explicit stratification characteristic, fields were also recruited across a range of synthetic turf ages to
allow potential differences in chemical content and particle size distribution to be assessed with age.
Samples were collected from seven set locations at each field to allow for analysis of between-field and
within-field variation. Questionnaires were also administered to facility owners and field managers to
obtain information on types and numbers of field users, maintenance practices, and any uses of cleaning
or other treatment products on the field.
45
-------
Tire Crumb Rubber infill Samples
from 25 Outdoor SynthetlcTurf
Fields
Tire Crumb Rubber Sample Collection
Tire Crumb Rubber Infill Samples
from 15 indoor Synthetic Turf
Fields
Tire Crumb Rubber Samples
from 9 Tire Recycling
Facilities
Direst Chemical Extraction and Analysts and Particle Character! atton
DartideSize
Characterization
67 Samp's,*i63 S refractions
Scanning tlectron
Microscopy
ISSanp s
Metals Acid Digestion
Analysts fC3/MS Targeted
1ZC Sanp es
Meta's Surface Analysis
XRF Targeted
ICDEanp'es
Extraeta bie SVOC Analysis
GC/WS/MS Targeted
sanpes
Extractable SVOCAnalysis
GC/MS Non-Targeted
16 Samples
Extractable SVOC Analysis
LC/MS Targeted/Suspect
i;2Sanpes
Extractabie SVOC Analysis
LC/MS Mon-Targeted
16 Samp es
Dynamic Chamber Emissions Testing and Analy i
VOC Emissions Analysis
GC/MS Targeted 25 °C
S2 5a np s
VOC Em ssions Ana lysis
GC/MS Targeted 50 =C
32 Sa'ip'es
SVOC Emissions Analysis
GC/MS Targeted 25 °C
32 Sanp'es
SVOC Emissions Analysis
GC/MS Targeted 60 cC
22 5amp'«
Fornasdehyde Emissions
Analysis N^LC/UV 25 -C
52 Samp s
Formaldehyde Emissions
Analysis HPLC/UV 60 °C
E2 5anp's
SVOC Emissions6C ZC
LC/MS Targeted/Suspect
E2 Lanp'es
VOC Emissions 60 °C
GC/MS Non-Targeted
16 Sample;
SVOC Emissions 60 °C
GC/MS Non-Targeted
ISSamp es
SVOC Emissions60 =C
LC/MS Non-Targeted
16 Sim pis
VOC ^missionsTime Series
bC/MS Targeted 25 -C
2 Sanp es 5TineFo-nts
VOC EmissionsTtrne Series
GC/MS Targeted 60 :C
2 Sarip>e$8~ nePo nts
SVOC EmissionsTime Series
GC/MS Targeted 25 cC
2 SampiesS~inePo,ns
SVOC EmissionsTime Series
GC/MS Targeted 60 SC
2 5a m pies 5 Ti me Points
SVOC S'liccne Wristband
toC/MS Targeted 25 "C
j Samp es 3 A r & I Wi srbsnd
Bioaccessibility Extraction and Analysis
Metals Bioaccessibslity Analysis
Metais Bioaccessibility Analysis
Metals Bioaccessibility Analysis
IC5/MS
ICP/MS
ICP/MS
Simulated Gastric Fluid
Simulated Saliva
Simulated Sweat plus Sebum
32 Ssmp-es
B2Sanp.es
£2ianpls
Microbial Analysis
Microbial Analysis- Targeted
230 5a m pies | FieldsOnlyS
Microbial Analysis- Non-Targeted
280 Sa m pies [ RehfcOnly)
Figure 3-1. Tire crumb rubber characterization research schematic overview.
46
-------
PACIFIC
Census Regions and Divisions of the United States
MIDWEST
MB
CENl
,o PACIFIC
SOUTH
Figure 3-2. United States census regions.
The wide range of chemical, physical and microbiological analyses conducted on the tire crumb rubber
collected at the tire recycling plants and synthetic turf fields for this study are summarized in Figure 3-3.
Laboratory analyses included:
• characterization for particle size, sand content (synthetic turf field samples only) and moisture
content;
• direct extraction and analysis of metals and SVOCs in tire crumb rubber;
• dynamic emission chamber measurements for formaldehyde, VOCs and SVOCs under two
temperature conditions - 25 and 60 degrees Celsius (°C);
• bioaccessibility measurements for metals using synthetic sweat, saliva, and gastric fluids; and
• for synthetic turf field samples, targeted and non-targeted characterization of microbes.
The emissions and bioaccessibility experiments were conducted to provide important information about
the types and amounts of chemical constituents in the tire crumb rubber material available for human
exposure through inhalation, dermal, and ingestion pathways. In addition to quantitative target chemical
analyses, suspect screening and non-targeted analysis methods were applied for VOCs and SVOCs to
identify whether there may be potential chemicals of interest that have not been identified or reported in
previous research. Chemical constituents from indoor and outdoor synthetic turf field samples were
compared with the samples of 'fresh' tire crumb rubber from recycling plants to better understand the
impact of weathering and facility use on the types and amounts of constituents available for human
47
-------
exposure. The tire crumb rubber infill from synthetic turf fields was also analyzed to assess microbial
populations using targeted and non-targeted analyses. A final piece of this research activity was to
identify and collate extant toxicity reference data for selected chemical constituents and contaminants
identified through the laboratory analyses.
Exposure-Related
Small Chamber Emissions
Formaldehyde - HPLC/UV
VOCs -GC/TOFMS
Micro Chamber Emissions
SVOCs - GC/MS/MS
SVOCs - LC/TOFMS
Bioaccessibility
Metals - Sweat - ICP/MS
Metals - Saliva - ICP/MS
Metals - Gastric - ICP/MS
Constituents
Solvent Extraction
SVOCs-GC/MS/MS
SVOCs -LC/TOFMS
Acid Digestion
Metals-ICP/MS
Spectrometry
Metals-XRF
Particle Characterization
Particle Size - Gravimetric
Moisture Content
Rubber/Sand Content
Particle Size/Morphology - SEM/EPMA
Microbial Characterization
Targeted Species - ddPCR
Non-Targeted Species - PCR
Figure 3-3. Summary of chemical, physical and microbial analyses performed for tire crumb rubber
characterization. Microbial characterization and analysis of rubber/sand content was only performed for
samples from synthetic turf fields. [ddPCR = Droplet digital polymerase chain reaction; EPMA = Electron probe
microanalysis; GC/MS/MS = Gas chromatography /tandem mass spectrometry; GC/TOFMS = Gas chromatography/time-of-
flight mass spectrometry; HPLC/UV = High performance liquid chromatography/ultraviolet spectrometry; ICP/MS =
Inductively coupled plasma/mass spectrometry; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry;
PCR = Polymerase chain reaction; SEM = Scanning electron microscopy; SVOC = Semi volatile organic compound; VOC
= Volatile organic compound; XRF = X-ray fluorescence]
3.1.1 Target Chemicals
An important goal of this research was to apply a range of sensitive and specific analytical methods that
were likely to provide quantitative measurement or presence/absence data for a wide range of chemicals
potentially associated with tire crumb rubber. Proposed metal, VOC and SVOC target analytes are
shown in Tables 3-1 through 3-5. Target analyte selection was based on a combination of information
from previous tire crumb rubber research studies, information on potential tire manufacturing chemical
ingredients, and analytical laboratory and method capabilities. The Literature Review/Gaps Analysis
(Appendix C) identified several hundred chemicals that have been reported in the literature based on
analysis of tire crumb rubber or playground surface rubber, rubber leachate, headspace analysis or
environmental measurements. In some cases, the literature reported only presence of chemical
constituents, without quantitative measurements. Some chemicals were included in the analysis because
they were reported through the literature or other sources to be potential tire manufacturing components,
48
-------
process chemicals or degradates. Many of the VOC secondary analytes were included because the
existing standards were available and included in mixtures typically analyzed in the laboratory.
Chemical lists are divided into primary and secondary analytes for reporting efficiency in this report.
Results for the primary analytes are included in the body of this report. Results for both primary and
secondary analytes are included in report appendices. The primary analytes highlighted in the body of
the report were selected from the larger list of chemicals based on their reported potential association
with tire crumb rubber in this study or other studies, and in part because of their potential interest as
well-known chemicals. Many SVOC chemicals were proposed for suspect screening LC/TOFMS
analysis based on previous reports that they may be associated with tire crumb rubber and where mass
spectra may be available to identify the presence of the chemical with some degree of confidence (Table
3-5). A subset of VOC and SVOC samples was also analyzed using non-targeted approaches, which
generated characteristic mass spectra that were explored to tentatively identify or propose chemical
presence for further investigation.
Table 3-1. Target Metal Analytes in Tire Crumb Rubber Samples Analyzed by ICP/MS and XRF
Metal
Analvtc
Category
CAS
Number1*
ICP/
MS
XRF
Literature Review/Gaps Analysis Reference ID
(see Appendix C)
Arsenic
Primary
7440-38-2
Yes
Yes
6, 7, 17, 36, 45, 49, 51, 60, 63, 66, 71, 79
Cadmium
Primary
7440-43-9
Yes
Yes
6, 7, 17, 28, 34, 45, 47, 49, 51, 60, 63, 66, 71, 79, 89
Chromium
Primary
7440-47-3
Yes
Yes
6, 7, 17, 28, 32, 36, 45, 47, 49, 51, 57, 60, 63, 66, 71, 76, 78, 79, 89
Cobalt
Primary
7440-48-4
Yes
Yes
6, 7, 49, 63
Lead
Primary
7439-92-1
Yes
Yes
6, 7, 16, 17, 20, 28, 32, 34, 36, 45, 47, 49, 51, 57, 60, 63, 66, 71,
78, 79, 89
Zinc
Primary
7440-66-6
Yes
Yes
6, 7, 17, 28, 32, 34, 36, 47, 49, 51, 54, 57, 61, 63, 66, 71, 72, 79, 89
Aluminum
Secondary
7429-90-5
Yes
No
6, 7, 36, 49, 63,66,71
Antimony
Secondary
7440-36-0
Yes
Yes
6, 7, 49
Barium
Secondary
7440-39-3
Yes
Yes
6, 7, 17,36, 49,51,57, 63,71,78
Beryllium
Secondary
7440-41-7
Yes
No
6, 45, 49, 60
Copper
Secondary
7440-50-8
Yes
Yes
6, 7, 17, 36, 45, 47, 49, 51, 57, 60, 63, 66, 71
Iron
Secondary
7439-89-6
Yes
Yes
6, 7, 36, 47, 49, 57, 63,66,71
Magnesium
Secondary
7439-95-4
Yes
No
6, 7, 36, 45, 49, 60, 66
Manganese
Secondary
7439-96-5
Yes
Yes
6, 17, 36, 49, 57, 63,66,71
Mercury0
Secondary
7439-97-6
No
No
6, 7, 28, 49,51,71,78, 89
Molybdenum
Secondary
7439-98-7
Yes
Yes
6, 7, 49, 66
Nickel
Secondary
7440-02-0
Yes
Yes
6, 7, 17, 47, 49,51,57, 63,66,71
Rubidiumd
Secondary
7440-17-7
Yes
Yes
6, 36, 49
Selenium
Secondary
7782-49-2
Yes
Yes
6, 7, 34, 45,49,51,60, 66,71
Strontium
Secondary
7440-24-6
Yes
Yes
6, 36, 49
Tin
Secondary
7440-31-5
Yes
Yes
6, 28, 49, 63,71,89
Vanadium
Secondary
7440-62-2
Yes
No
6, 7, 45, 49, 60
a ICP/MS = Inductively coupled plasma/mass spectrometry; XRF = X-ray fluorescence spectrometry
b Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
0 Mercury was a target analyte only in the bioaccessibility measurements
dNot analyzed in bioaccessibility analyses
49
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Table 3-2. Target VOC Analytes in Tire Crumb F
Lubber Emission Samples Analyzed by GC/TOFMS3
VOC
Analvtc
Category
CAS
Numbcrh
Literature Review/Gaps Analysis Reference ID
(see Appendix C)
Formaldehyde0
Primary
50-00-0
55, 94
Methyl isobutyl ketone
Primary
108-10-1
15, 16, 32, 54, 55, 57, 71
Benzothiazole
Primary
95-16-9
7, 12, 15, 16, 17, 34, 36, 46, 51, 54, 55, 57, 71, 82
1,3-Butadiene
Primary
106-99-0
N/A
Styrene
Primary
100-42-5
11, 12, 15, 16, 55
Benzene
Primary
71-43-2
2, 10, 11, 12, 15, 16, 32, 55, 57, 63, 65, 71
Toluene
Primary
108-88-3
8, 10, 11, 12, 15, 16, 32, 55, 57, 61, 63, 65, 71, 76, 78
Ethylbenzene
Primary
100-41-4
10, 11, 15, 16, 57,61
m/p-Xylene
Primary
108-38-3,
106-42-3
8, 10, 11, 12, 15, 16, 32, 55, 57, 61, 63, 65
o-Xylene
Primary
95-47-6
16, 55, 57, 61
SumBTEXd
Primary
N/A
N/A
trans-2-Butene
Secondary
624-64-6
N/A
cis-2-Butene
Secondary
590-18-1
N/A
4-Ethyltoluene
Secondary
622-96-8
8, 16
1,3,5 -T rimethylbenzene
Secondary
108-67-8
16,61
1,1 -Dichloroethene
Secondary
75-35-4
N/A
1,1 -Dichloroethane
Secondary
75-34-3
N/A
cis-1,2-Dichloroethene
Secondary
156-59-2
61
1,2-Dichloroethane
Secondary
107-06-2
16
1,1,1 -T richloroethane
Secondary
71-55-6
12
Carbon tetrachloride
Secondary
56-23-5
16, 32, 57
1,2-Dichloropropane
Secondary
78-87-5
16
Trichloroethylene
Secondary
79-01-6
16
Tetrachloroethylene
Secondary
127-18-4
16, 57
Chlorobenzene
Secondary
108-90-7
16
m-Dichlorobenzene
Secondary
541-73-1
N/A
p-Dichlorobenzene
Secondary
106-46-7
57
o-Dichlorobenzene
Secondary
95-50-1
N/A
Trichlorofluoromethane (Freon™ 11)
Secondary
75-69-4
16, 32, 57
Dichlorodifluoromethane (Freon™ 12)
Secondary
75-71-8
16, 32, 57
1,1,2-Trichlorotrifluoroethane (Freon™
113)
Secondary
76-13-1
16
11VOC = Volatile organic compound; GC/TOFMS = Gas chromatography/time-of-flight mass spectrometry; N/A = Not
applicable
b Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
0 Formaldehyde was analyzed by HPLC/UV
d SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
50
-------
Table 3-3. Target SVOC Analytes for Tire Crumb Rubber Extraction and Emission Samples Analyzed by
GC/MS/MS3
SVOC
Analytc
Category
CAS
Number1*
Literature Review/Gaps Analysis Reference ID
(sec Appendix C)
Phenanthrene
Primary
85-01-8
7, 10, 12, 15, 17, 23, 28, 45, 46, 47, 61, 65, 72, 79, 82, 89
Fluoranthene
Primary
206-44-0
7, 10, 12, 15, 17, 23, 28, 45, 46, 47, 61, 65, 72, 79, 82, 89
Pyrene
Primary
129-00-0
7, 10, 12, 15, 17, 23, 28, 45, 46, 47, 49, 61, 63, 65, 72, 79, 82, 89
Benzo[a]pyrene
Primary
50-32-8
12, 15, 23, 28, 45, 46, 47, 49, 63, 65, 79, 82, 89
Benzo [ghijperylene
Primary
191-24-2
12, 15, 23, 28, 46, 47, 49, 63, 65, 79, 89
Suml5PAH°
Primary
N/A
N/A
Benzothiazole
Primary
95-16-9
7, 12, 15, 16, 17, 34, 3646, 51, 54, 55, 57, 71, 82
Dibutyl phthalate
Primary
84-74-2
23, 46, 54, 57, 61, 72, 82
Bis(2-ethylhexyl) phthalate
Primary
117-81-7
23, 36, 46, 54, 57, 61, 72, 82
Aniline
Primary
62-53-3
7, 36, 54, 57
4-tert-octylphenol
Primary
140-66-9
16, 17, 34,51,61,72
Hexadecane
Primary
544-76-3
17, 34
Naphthalene
Secondary
91-20-3
7, 10, 12, 15, 17, 23, 28, 45, 46, 47, 57, 61, 72, 79, 82, 89
1 -Methy lnaphthalene
Secondary
90-12-0
15, 17, 23
2-Methylnaphthalene
Secondary
91-57-6
15, 17, 23
Acenaphthylene
Secondary
208-96-8
12, 15, 23, 28, 45, 46, 61, 82, 89
Fluorene
Secondary
86-73-7
7, 15, 23, 28, 45, 46, 47, 61, 72, 79, 82, 89
Anthracene
Secondary
120-12-7
12, 23, 28, 45, 46, 47, 61, 72, 79, 82, 82, 89
1 -Methy lphenanthrene
Secondary
832-69-9
23
2-Methylphenanthrene
Secondary
2531-84-2
23
3 -Methy lphenanthrene
Secondary
832-71-3
23
Benz[a]anthracene
Secondary
56-55-3
12, 15, 23, 28, 45, 46, 47, 49, 63, 65, 79, 82, 89
Chrysene
Secondary
218-01-9
7, 12, 15, 23, 28, 45, 46, 47, 49, 63, 65, 79, 82, 89
Benzo(b)fluoranthene
Secondary
205-99-2
7, 12, 15, 28, 45, 46, 47, 49, 63, 65, 79, 82, 89
Benzo(k)fluoranthene
Secondary
207-08-9
12, 15, 28, 45, 46, 47, 63, 79, 82, 89
Benzo(e)pyrene
Secondary
192-97-2
12, 15, 23
DBA + ICDPd
Secondary
53-70-3;
193-39-5
12, 23, 28, 45, 46, 47, 49, 63, 65, 79, 82, 89
Coronene
Secondary
191-07-1
12, 23
Dibenzothiophene
Secondary
132-65-0
12, 23, 46
2-Bromomethylnaphthalene
Secondary
939-26-4
36
n-Butylbenzene
Secondary
104-51-8
55,61
Dimethyl phthalate
Secondary
131-11-3
23, 46, 61, 72
Diethyl phthalate
Secondary
84-66-2
23, 46, 54, 57, 61, 72, 82
Diisobutyl phthalate
Secondary
84-69-5
46, 54, 82
Benzyl butyl phthalate
Secondary
85-68-7
23, 46, 54, 61, 72, 82
Di-n-octyl phthalate
Secondary
117-84-0
23, 61, 72, 82
51
-------
Table 3-3 Continued
SVOC
Analytc
Category
CAS
Numbcrb
Literature Review/Gaps Analysis Reference ID
(see Appendix C)
2,6-Di-tert-butyl-p-cresol
(BHT)
Secondary
128-37-0
15, 16, 17, 34, 46, 54, 82, 94
Bis-(2,2,6,6-tetramethyl-4-
piperidinyl) sebacate
Secondary
52829-07-9
54
Cyclohexyl isothiocyanate
Secondary
1122-82-3
54, 57
a GC/MS/MS = Gas chromatography/tandem mass spectrometry; N/A = Not applicable
b Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
dDBA + ICDP = Sum of Dibenz[a,h]anthracene and Indeno(l,2,3-cd)pyrene
Table 3-4. Target SVOC Analytes for Tire Crumb Rubber Extraction and Emission Samples Analyzed by
LC/TOFMS3
SVOC
CAS
Number1*
Literature Review/Gaps Analysis Reference ID
(see Appendix C)
Di(2-ethylhexyl) adipate
103-23-1
7, 46, 82
Diisononyl phthalate
28553-12-0
23, 46, 61, 72
Diisodecyl phthalate
26761-40-0
23, 46, 72
2-Mercaptobenzothiazole (MBT)
149-30-4
46, 57, 71, 94
2-hydroxybenzothiazole
934-34-9
7, 36, 54, 57, 71
Dicyclohexylamine
101-83-7
7, 54
Cyclohexanamine
108-91-8
54
N-cyclohexyl-N-methylcyclohexanamine
7560-83-0
54, 57
Phthalimide
85-41-6
7, 57
Resorcinol
108-46-3
71, 94
a SVOC = Semivolatile organic compound; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry
b Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
Table 3-5. Target SVOC Analytes for Suspect Screening Analysis of Tire Crumb Rubber and Emissions
Samples by LC/TOFMS3
SVOC
CAS
Number1*
Literature Review/Gaps Analysis Reference ID
(see Appendix C)
1,3 -Dicyclohexylurea
2387-23-7
54
N,N'-diphenyl-l,4-Benzenedi amine
74-31-7
36, 94
Dehydroabietic acid
1740-19-8
36
2-( 1 -phenylethyl) -phenol
26857-99-8
54
2-(Methylthio)benzothiazole
615-22-5
54
2-(4-morpholinothio)benzothiazole (MB S)
102-77-2
2,71, 94
2,2,4-Trimethyl-l,2-dihydroquinoline (TMQ)
147-47-7
94
2,2'-Methylene-bis-(4-methyl-6-tert-butylphenol) (BPH)
119-47-1
94
2,4-Dimethylphenol
105-67-9
57
52
-------
Table 3-5 Continued
svoc
CAS
Numbcrh
Literature Review/Gaps Analysis Refcrcnee ID
(see Appendix C)
2,6-Di-tert-butyl-4-methylphenol (BHT)
128-37-0
15, 16, 17, 34, 46, 54, 82, 94
2,2'-Dithiobis(benzothiazole) (MBTS)
120-78-5
94
2-Ethylanthracene-9,10-dione
84-51-5
36
2-Morpholinodithiobenzothiazole (MBSS)
95-32-9
94
2-Phenylbenzimidazole
716-79-0
36
2-Phenylbenzothiazole
883-93-2
36
3,5-Di-tert-Buty 1-4-hy droxybenzaldehyde
1620-98-0
54
4-Nonylphenol
104-40-5
54, 61, 72
4-tert-Butylphenol
98-54-4
46
5-Methyl-2-hexanone
110-12-3
54
Acetophenone
98-86-2
54, 57
Isocyanatobenzene
103-71-9
54
Benzoic acid
65-85-0
55, 57
Benzyl alcohol
100-51-6
54, 57
Biphenyl
92-52-4
23, 55
Butylated hydroxyanisole (isomeric mixture)
25013-16-5
17
Caprolactam disulfide (CLD)
23847-08-7
94
Carbazole
86-74-8
45, 57
p-Cresol
106-44-5
57
o-Cresol
95-48-7
57
Isocyanatocyclohexane
3173-53-3
54
Cyclohexanone
108-94-1
7, 54
Cyclohexylthiophthalimide (CTP)
17796-82-6
N/A
Di-(2-ethyl)hexylphosphorylpolysulfide (SDT)
Not Found
94
Dibenzofuran
132-64-9
23
Dicyclohexylamine
101-83-7
7, 54
Dimethyldiphenylthiuram disulfide (MPTD)
53880-86-7
94
Di-ortho-tolylguanidine (DOTG)
97-39-2
94
Dipentamethylenethiuram tetrasulfide (DPTT)
120-54-7
94
Diphenylamine
122-39-4
2, 36
Dithiodimorpholine (DTDM)
103-34-4
94
Docosanoic acid
112-85-6
36
Dodecanoic acid
143-07-7
54
Dotriacontane
544-85-4
36
Drometrizol
2440-22-4
54
Eicosane
112-95-8
36
Eracylamide
112-84-5
54
1 -(2-Butoxyethoxy)ethanol
54446-78-5
54
2-Butoxyethanol
111-76-2
54
Ethanone, 1,1 '-(1,3 -phenylene)bis-
6781-42-6
54
Ethanone, 1,1 '-(1,4-phenylene)bis-
1009-61-6
54
l-[4-(l-methylethenyl)phenyl]ethanone
5359-04-6
54
53
-------
Table 3-5 Continued
SVOC
CAS
Literature Review/Gaps Analysis Refcrcnee ID
Numbcrh
(see Appendix C)
Ethylenethiourea (ETU)
96-45-7
94
N-Cyclohexylformamide
766-93-8
54
Heptadecane
629-78-7
36
Hexa(methoxymethyl)melamine
3089-11-0
54
Hexacosane
630-01-3
36
2-Ethylhexanoic acid
149-57-5
54
Isononylphenol
11066-49-2
61,72
Isophorone
78-59-1
57
N,N'-Bis( 1,4-dimethylpentyl)-p-phenylenediamine
(7PPD)
3081-14-9
94
N,N-Dicyclohexyl-2-benzothiazolesulfenamide (DCB S)
4979-32-2
94
N,N'-Diethylthiourea (DETU)
105-55-5
94
N,N'-Diphenylguanidine (DPG)
102-06-7
94
N,N'-Diphenyl-p-phenylenediamine (DPPD)
74-31-7
36, 94
N,N'-Ditolyl-p-phenylenediamine (DTPD)
27417-40-9
94
N-( 1,3 -dimethylbutyl)-N'-phenyl-p-phenylenediamine
(6PPD)
793-24-8
94
N-Cyclohexyl-2-benzothiazolesulfenamide (CB S)
95-33-0
94
N-Isopropyl-N'-phenyl-p-phenylenediamine (IPPD)
101-72-4
54, 71, 94
N-Methyl-2-pyrrolidone
872-50-4
54
N-Nitrosodiphenylamine
86-30-6
57
Nonadecane
629-92-5
36
N-Oxvdiethvlcncdithiocarbaim i-N' -
oxydiethylenesulfenamide (OTOS)
13752-51-7
94
N-tert-Butyl-2-benzothiazolesulfenamide (TBB S)
95-31-8
94
Octadecane
593-45-3
N/A
Methyl stearate
112-61-8
36
o-Cyanobenzoic acid
3839-22-3
7, 36
Pentacosane
629-99-2
36
2,4-Bis( 1,1 -dimethylethyl)phenol
96-76-4
54
2,4-Bis( 1 -methyl-1 -phenylethyl)phenol
2772-45-4
36, 54
m-tert-butylphenol
585-34-2
54
p-Phenylenediamine (PPD)
106-50-3
71
Pyrazole
288-13-1
36
Pyrimidine, 2-(4-pentylphenyl)-5-propyl-
94320-32-8
36
Tetrabenzylthiuram disulfide (TBZTD)
10591-85-2
71, 94
Tetrabutylthiuram disulfide (TBTD)
1634-02-2
71, 94
Tetracosane
646-31-1
36
Tetramethylthiuram disulfide (TMTD)
137-26-8
94
Tetramethylthiuram monosulfide (TMTM)
97-74-5
94
Tricosane
638-67-5
36
a SVOC = Semivolatile organic compound; LC/TOFMS = Liquid chromatography/time-of-flight spectrometry; N/A = Not
applicable
b Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
54
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3.2 Recruiting Recycling Plants and Synthetic Turf Fields
3.2.1 Recycling Plant Recruitment and Selection
Researchers aimed to recruit and seek consent from nine tire recycling plants producing tire crumb
rubber for use as synthetic turf infill - five plants using an ambient production process and four plants
using a cryogenic production process. Another goal was to recruit tire recycling plants across the four
U.S. census regions. CDC/ATSDR and EPA participated in the recruitment effort and contacted seven
companies operating tire recycling plants that produce tire crumb rubber for synthetic turf infill. Sample
collection agreements were reached with six of those companies, resulting in successful sample
collection at nine tire recycling plants operated by those six companies. The nine recycling plants were
located across all four U.S. census regions. Six recycling plants used ambient processing and three used
cryogenic processing.
3.2.2 Synthetic Turf Field Recruitment and Selection
Researchers aimed to recruit and seek consent from 40 synthetic turf fields with recycled tire crumb
rubber infill - 10 fields in each of the four U.S. census regions. However, if the study team could not
obtain the maximum sample size in a specific U.S. census region by the end of the recruitment period,
researchers consented and sampled field(s) in alternate census regions. There were no restrictions on
field age, "grass blade" composition or color, or field type (i.e., soccer, baseball, or softball).
Researchers requested field size information, but that was not a specific exclusion criterion. The study
team did exclude synthetic turf fields with encapsulated, colored or painted tire crumb rubber and
limited participation to two outdoor fields per facility. To include two fields at one facility, the fields
had to meet one of two criteria: the fields must be of different ages or the fields must be installed by
different manufacturers. Researchers did allow two fields from the same facility of the same age if one
was an indoor field and the other was an outdoor field.
CDC/ATSDR used a convenience sampling approach to recruit community facilities with synthetic turf
fields. Researchers found prospective facilities using online search engines and the following key search
terms: "recreational fields," "sports training facilities," "sports training," "sport fields," "sporting
fields," "soccer fields," "baseball fields," "football fields," and "parks and recreation." The researchers
used these key search terms combined with the state or area of focus. Additionally, potential facilities
and fields were allowed to self-identify if interested in participating.
Between August and November 2016, CDC/ATSDR researchers initiated contact with a total of 306
community facility and field owners. Potential facilities and fields were classified into one of six
categories based on the initial contact: (1) no answer (a voicemail was left, if applicable); (2) incorrect
contact person (correct contact information was requested); (3) immediate declination; (4) requested
additional information; (5) non-eligible (i.e., did not have a synthetic turf field); and (6) verbal consent.
Contact with facilities in categories 1 and 2 was limited to five times. For those immediately declining
participation in the study, researchers requested information regarding the declination. In general, those
declining to participate gave reasons that were limited to three main issues:
• Liability: Contacted field owners and managers expressed concern about the potential liability
associated with sampling their fields.
• Confidentiality: As expressed in the agreement forms, individual facility names and locations
would not be released in the public reports, although the number of fields sampled per U.S.
55
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census region would be noted. CDC/ATSDR and EPA could not, however, assure the facility of
complete anonymity or confidentiality.
• Not at this time: Although many field owners and managers were interested in the study, they
declined participation in the current study.
For those facility or field owners/managers requesting additional information, CDC/ATSDR researchers
sent a fact sheet describing the study and the facility agreement form via email. For those agreeing to
participate, researchers administered the eligibility screening and sent the agreement form to those
facilities deemed eligible. The researchers categorized eligible fields as indoor or outdoor and by age
(2008 or older, 2009 to 2012, and 2013 to 2016). The researchers contacted the facilities that verbally
agreed to participate weekly until (1) obtaining written agreement, (2) attaining the maximum number of
facilities consented for the census region, or (3) reaching the project recruitment period end, which was
in early November 2018.
For inclusion in the study, facility owners or managers had to provide written agreement to recycled tire
crumb rubber sample collection at their facility and answering a questionnaire on field maintenance
procedures and field use. CDC/ATSDR researchers obtained participation agreements from 21
community fields, including 9 outdoor fields and 12 indoor fields. Researchers also collaborated with
the U.S. Army Public Health Center (APHC) to identify 19 synthetic turf fields at Army installations
across the United States for participation in the study, including 16 outdoor fields and 3 indoor fields.
3.3 Tire Crumb Rubber Sample Collection Method Summaries
Standard operating procedures (SOPs) were developed for all tire crumb rubber sample collection and
processing methods. A list of SOPs is provided in Appendix D. Brief method summaries are provided
below.
3.3.1 Recycling Plant Sample Collection
Researchers collected recycled tire crumb rubber samples of the size category used in synthetic turf
fields (typically 10 to 20 mesh or 0.84 to 2 mm) from nine tire recycling plants around the United States.
The samples were collected from three different storage containers (typically flexible intermediate bulk
containers) at each plant. The samples collected from each sack were placed into pre-cleaned 1-liter (L)
glass or high-density polyethylene (HDPE) wide-mouth jars (see Figure 3-4). From each storage
container, researchers filled two 1-L HDPE jars for metals analysis, two 1-L amber glass jars with
Teflon™-lined lids for organic chemical analysis, and one 1-L HDPE jar for particle characterization. At
most plants, the study team used pre-cleaned stainless-steel scoops to gather tire crumb rubber for
organics analysis and pre-cleaned plastic scoops to gather tire crumb rubber for metals analysis and
particle characterization. At one plant, researchers collected samples from storage containers using the
plant's established equipment and protocol; samples were collected using a stainless-steel sampling
spike designed to include material from multiple levels of the storage container in the vertical and
horizontal dimensions.
56
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Recycling
Plant
Storage
Container
1
Storage
Container
2
Storage
Container
3
ii as
J j m i i
Organics
Metals
Particles
.1
| J -M A
Figure 3-4. Schematic representation of tire crumb rubber sample
collection at tire recycling plants. All collections made into 1-L
pre-cleaned glass or high-density polyethylene (HDPE) jars.
3.3.2 Synthetic Turf Field Sample Collection
Researchers collected tire crumb rubber samples from 40 synthetic turf fields to support characterization
of chemical constituents and to examine microbial species. Substantial variability in tire crumb rubber
chemical concentrations have been reported; therefore, researchers used a composite sample collection
approach at synthetic turf fields. Researchers used specified sampling locations for rectangular fields,
such as soccer and football fields (Figures 3-5) and for baseball and softball fields (Figure 3-6).
©
¦ Sample Collection locations
Figure 3-5. Sample collection locations for rectangular synthetic
turf fields, including soccer, football and other rectangular fields.
57
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Figure 3-6. Sample collection locations for baseball and softball synthetic turf
fields with A) turf in the infield and B) no turf in the infield.
Researchers collected samples from each of the seven locations at each field for organic chemical (VOC
and SVOC), metal, microbial, and particle characterization analyses (Figure 3-7). At each location,
researchers filled one 250-milliliter (mL) HDPE jar for metals analysis, one 250-mL amber glass jar
with a Teflon™-lined lid for organic chemical analysis, one 250-mL HDPE jar for particle
characterization, and one sterile 50-mL tube for microbial analysis.
Repeated at all 7 field locations
Particles
Microbes
Orqanics
Figure 3-7. Schematic representation of the four samples that were collected
at each of the seven locations on each field. Samples for chemical and
particle characterization were collected into 250-mL pre-cleaned amber
glass or high-density polyethylene (HDPE) jars. Microbial samples were
collected into sterile 50-mL tubes.
58
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Synthetic turf fields were recruited for sample collection from across the continental United States,
which precluded being able to drive directly from a central location to the various fields. And often, the
fields were only available for sample collection for short time periods during the scheduled sampling
day. In addition, samples collected for microbial analysis had to be shipped cold, as soon as possible
after collection, for arrival at the laboratory the following morning. Due to these constraints, the study
team developed self-contained sampling kits - one for tire crumb rubber sample collection for metals,
organics and particle analyses (Figure 3-8) and one for tire crumb rubber sample collection for microbial
analysis (Figure 3-9). These kits could be rapidly shipped to sampling locations, contained all required
sampling materials, and provided for rapid overnight return shipment using the same packaging
materials. With these sampling kits, sample collection could usually be completed in 1.5 to 2.0 hours.
Field sampling most often occurred in the morning, allowing samples to be transported to a delivery
service office for overnight shipment to the appropriate laboratories, and sampling was only scheduled
Monday through Thursday to allow overnight shipment and laboratory receipt Tuesday through Friday.
Shipping 'Overpack' Box
Nitrile Gloves
Field ID Code
Safety Glasses ShippingTape
COC Forms
Sample Form
Shipping Label
Location Marking Flags
Secondary Containment
Bags
HDPE 'Particles' Jar
Plastic Sampling Comb
Inner Box w8 HDPE
'Particles' Jars
HDPE 'Metals' Jar
Inner Box w8 HDPE
'Metals' Jars
Inner Box w 8 Glass
'Organics' Jars
Trash Bag
'Organics' Glass Jar
w Bubble Wrap Pouch
Stainless Steel Sampling
Comb
Figure 3-8. Sample collection kit for metal, organic and particle sample collection at synthetic turf
fields. | COC = Chain of custody; HDPE = High-density polyethylene]
59
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Shipping Cooler and Box
Ice Packs (12 total)
Sterile Falcon® Tubes (8)
Tube Tray
iButton temperature
logging system stored in
Tube
COC Forms
Shipping Label
rUSSAiiASmlJB -w-
PERISHABLE ¦
Safety Glasses
Nitrile Gloves
Sterile Spatulas (8)
Disposable lab coat not
shown
Figure 3-9. Sample collection kit for microbial sample collection at synthetic turf fields.
[COC = Chain of custody]
Researchers collected tire crumb rubber samples for organic chemical, metal, and particle analyses by
removing tire crumb rubber from about the top 3 centimeters (cm) of the synthetic turf field surface,
using either a comb or spatula (Figure 3-10). The 3-cm depth was selected because it is likely that most
exposures occur to tire crumb rubber infill available near the surface of the field. Researchers collected
samples for organics (SVOC and VOC) analysis, using a small handheld metal comb or spatula to pull
tire crumb rubber from the field at each location, and placed the collected tire crumb rubber into
certified pre-cleaned 250-mL amber glass wide-mouth containers with Teflon™-lined lids. For metals
analysis, researchers used a small handheld plastic comb or spatula to pull tire crumb rubber from the
field at each location and placed the collected tire crumb rubber into certified pre-cleaned 250-mL
HOPE wide-mouth jars. For samples to be used for particle characterization, researchers used a small
handheld plastic comb or spatula to pull tire crumb rubber from the field at each location and placed
collected tire crumb rubber into certified pre-cleaned 250-mL HDPE wide-mouth jars. At some fields
(e.g., older fields with greater wear and higher blade and rubber compression), samples that were to be
collected by comb, had to alternatively be collected by spatula.
Researchers also collected individual samples for microbe analysis from each of the seven locations at
each field. Researchers employed aseptic techniques when collecting tire crumb rubber samples for
microbial analysis by wearing a new disposable lab coat, wearing clean nitrile gloves at all times, and
donning new gloves at each location on the field. A new, sterile polypropylene spatula was used at each
of the seven locations to collect the sample for microbial analysis. At each of the seven locations,
researchers inserted the sterile spatula into the syntheti c turf field surface to a maximum depth of about
3 cm from the surface, moved it forward to collect tire crumb material, and placed the tire crumb rubber
into a new, sterile 50-mL polypropylene tube with volumetric lines (Figure 3-10). The tubes were filled
with tire crumb rubber material to the 25-mL line. Once samples were collected, the researchers
immediately placed them into a cooler with ice packs and shipped the samples the same day they were
collected, in a container with ice packs, to the appropriate laboratory by overnight shipment.
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A Organics B Metals & Particles
C Microbes
Figure 3-10. Sample collection methods using A, B) combs and C) spatulas to
remove tire crumb rubber from about the top 3 cm of the synthetic turf field surface.
3.4 Synthetic Field Use and Maintenance Questionnaire Administration
A copy of the questionnaire was provided to each field owner/manager prior to questionnaire
administration as some of the questions required time in advance to find specific answers. The interview
was conducted via phone, lasted approximately 30 minutes, and included questions on the type of
synthetic turf field, how the facility was used, and the standard operating procedures (SOPs) for
maintenance of the field. The interviewer entered the answers to these questions directly into an Epi
Info™ Version 7.2 database (CDC, 2017). After completion of the questionnaire, the field
owner/manager was given contact information for any further questions. The questionnaire is provided
in Appendix F.
3.5 Tire Crumb Rubber Sample Processing Method Summaries
3.5.1 Recycling Plant Sample Processing
As described in section 3.3.1, researchers collected tire crumb rubber samples from three different
storage containers at each plant. The three samples collected from each recycling plant were kept as
individual samples and a portion of each sample was prepared for metals, organics, and particle analysis
(Table 3-6). Tire crumb rubber from recycling plants was not analyzed for microbes.
Table 3-6. Sample Preparation and Analysis of Tire Crumb Rubber Samples Collected at Tire Recycling Plants
Sample Analyses"
Type of Analysis
Sample Preparation
SVOC Extraction
Organics
All samples
Metals Digestion - ICP/MS
Metals
All samples
Metals - XRF
Metals
All samples
VOC Emissions
Organics
All samples
SVOC Emissions
Organics
All samples
Particle Size - Gravimetric
Particle
All samples
Metal Bioaccessibility
Metals
All samples
Moisture Content
Particle
All samples
61
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Table 3-6 Continued
Sample Analyses"
Type of Analysis
Sample Preparation
SVOC Extraction Non-Targeted
Organics
Subset of samples
VOC Emission Non-Targeted
Organics
Subset of samples
SVOC Emission Non-Targeted
Organics
Subset of samples
Particle Characterization - SEM
Particle
Subset of samples
Particle Characterization - EPMA
Particle
Subset of samples
VOC Emission Time Series
Organics
Subset of samples
SVOC Emission Time Series
Organics
Subset of samples
SVOC Chamber Wristband Tests
Organics
Subset of samples
a SVOC = Semivolatile organic compound; ICP/MS = Inductively coupled plasma/mass spectrometry;
XRF = X-ray fluorescence spectrometry; VOC = volatile organic compound; SEM = scanning electron
microscopy; EPMA = electron probe microanalysis
3.5.2 Synthetic Turf Field Sample Processing
As described in section 3.3.2, researchers collected individual tire crumb rubber samples from seven
locations at each field for organics (VOC and SVOC), metals, microbial and particle characterization
analyses. For microbial analyses, all seven individual location samples from each field were scheduled
for separate analysis (Figure 3-11). The microbial samples were shipped cold, as soon as possible after
collection, to the laboratory for analysis; all other samples were sent to a central processing laboratory,
where they were processed for individual or composite analysis. Figure 3-11 shows the approach for
preparation and analysis of composite and individual tire crumb rubber samples collected from synthetic
turf fields.
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Analyses of Composite Samples (Subset of Fields)
- SVOC Extraction Non-Targeted - SVOC Emission Time Series
- VOC Emission Non-Targeted - VOC Emission Time Series
- SVOC Emission Non-Targeted - SVOC Chamber Wristband
Analyses of Composite Samples (All Fields)
- SVOC Extraction - SVOC Bioaccessibility- Sweat
- SVOC Emissions - SVOC Bioaccessibility- Saliva
- VOC Emissions - SVOC Bioaccessibility- Gastric
3 8 9 9 3. 2
Analyses of Composite Samples (All Fields)
- Metals Digestion- ICP/MS - Metals Bioaccessibility- Sweat
- Metals XRF - Metals Bioaccessibility- Saliva
- Moisture - Metals Bioaccessibility- Gastric
Analyses of Individual Samples (5 Fields)
All 7 Field Locations:
- SVOC Extraction
Field Locations 1, 2 and 3:
- SVOC Emissions
- VOC Emissions
- SVOC Bioaccessibility- Sweat
- SVOC Bioaccessibility- Saliva
- SVOC Bioaccessibility- Gastric
Organics
Composite Sample
Combine 35 g from
each sample
Organics Samples from 7 Field Locations
iiiinsaa
d ra ra ra ra ra
Metals
Composite Sample
Combine 35 g from
each sample
Metals Samples from 7 Field Locations
V [3f3pf3pf3ra—
/ j J j j J J j
Analyses of Individual Samples (5 Fields)
All 7 Field Locations:
- Metals Digestion- ICP/MS
Field Locations 1, 2 and 3:
- Metals XRF
- Metals Bioaccessibility- Sweat
- Metals Bioaccessibility- Saliva
- Metals Bioaccessibility- Gastric
Particles
Composite Sample
Combine entire contents
from each sample
Analyses of Composite Samples (All Fields)
- Particle Size - Sieve/Gravimetric
- Rubber/Sand Content
Analyses of Individual Samples (All Fields)
- Microbial Targeted Species- ddPCR
- Microbial Non-Target Species - PCR
Analyses of Composite Samples (Subset of Fields)
- Particle Size - SEM
- Particle Size - EPMA
Figure 3-11. Schematic showing composite and individual location sample preparation and analysis for samples collected at synthetic turf fields.
63
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To support between-field assessments of chemical constituents in a cost- and time-effective manner, the
researchers took portions of the seven individual samples collected from each field for metals and
organics analysis and created a single metals composite sample and organics composite sample for each
field. For organics analyses, researchers added 35 grams (g) of the tire crumb rubber material from each
of the seven individual organics samples to a single certified pre-cleaned 500-mL amber wide-mouth
glass container with Teflon™-lined lid and mixed the composite sample thoroughly. Researchers then
removed sub-samples of the composite sample and added them to smaller, pre-cleaned and certified
amber glass containers to distribute to the analysis laboratories (Figure 3-11). Researchers used the same
procedure to prepare composite samples and sub-samples for metals analysis from the seven individual
metals samples, using certified pre-cleaned HDPE containers (Figure 3-11). Sub-samples prepared for
moisture analysis also came from the metals composite samples. To support a within-field variability
assessment of chemical constituents, researchers also prepared sub-samples of three to seven of the
individual location samples from a subset of five fields for separate metals and organics analyses (Figure
3-11). For particle characterization analysis, the researchers combined the entire contents of the seven
250-mL individual location samples collected from each field for particle analysis and mixed to form a
single particles composite sample for each field (Figure 3-11). Researchers retained the remaining
composite and individual samples in their sealed containers and stored all samples in a freezer at -20 °C.
3.6 Tire Crumb Rubber Sample Analysis Method Summaries
Standard operating procedures (SOPs) were developed for all tire crumb rubber sample analyses. A list
of SOPs is provided in Appendix D. Brief method summaries are provided below.
3.6.1 Moisture Analysis
A portion of each of the three tire crumb rubber samples collected from the recycling plants and a
portion of the synthetic turf field composite tire crumb rubber sample for metals analysis were analyzed
for moisture content. This analysis was performed so that chemical analysis results could be reported
consistently in terms of the amount of chemical per the amount of dry tire crumb rubber.
Moisture analysis was performed using a HE53 halogen moisture analyzer (Mettler Toledo, Columbus,
OH, USA). To determine the moisture content, the tire crumb rubber sample was removed from the
freezer and allowed to reach room temperature while the moisture analyzer was set up. Prior to
measurement, the balance calibration was verified using certified check weights. When the sample had
equilibrated to room temperature, the moisture analysis process was started. A disposable sample pan
was placed onto the moisture analyzer and tared. Tire crumb sample (2 g) was then spread in a thin,
even layer across the total surface of the pan and the weight was recorded on a moisture analysis form.
The moisture analysis was then started, with the analyzer heating the sample to 110 °C, and continued
until the mass loss was less than 1 milligram (mg)/30 seconds (s). The percent moisture content
displayed on the HE53 halogen moisture analyzer was then recorded on the form. All moisture analyses
were performed on duplicate samples (a second portion of tire crumb rubber from the same bottle) and
the average of the two measurements was used.
3.6.2 Sand/Rubber Fraction Analysis
Infill used on synthetic turf fields is sometimes installed as a mixture of tire crumb rubber and sand, and
sand may also be used as a base layer in some synthetic turf field installations. A number of the
synthetic turf field samples had a visible sand component, so an analysis was conducted to determine the
sand/rubber fraction of all synthetic turf field samples. Measurement of the sand fraction was performed
to allow calculation of analysis results as either the amount of chemical analyte (metal or organic
64
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analyte) per kilogram of infill (rubber plus sand) or amount of chemical analyte per kilogram of tire
crumb rubber in the infill.
One sample had a small fine gravel/coarse sand component that was retained on Number (No.) 4 and
No. 10 (4.75- to 2.00-millimeter [mm]) sieves. This material was separated by hand and weighed. In 15
samples, the sand was confined to the infill material (rubber plus sand) retained on a No. 60 (0.25-mm)
sieve. To separate the sand fraction from these samples, a floatation technique was employed. A salt
solution of either a sulfate or calcium chloride was mixed to create a solution that had a density higher
than the tire crumb, but lower than the mineral sand. The tire crumb material floated to the top of the
solution and was removed. The tire crumb and sand fractions were then rinsed, dried and weighed. The
percentage of sand and tire crumb in the No. 60 sieve fraction was then calculated, along with the
percentage of sand and tire crumb in the total sample.
Unless otherwise noted, the synthetic turf field tire crumb rubber infill samples prepared for physical,
chemical and microbial analyses included the sand fraction, when it was present, as part of the infill
material collected.
3.6.3 Gravimetric Particle Size Analysis
Tire crumb rubber from recycling plants and synthetic turf fields was analyzed for particle size analysis
(PSA). The total weight of the composited particles samples from each synthetic turf field ranged from
800 to 1100 g. The three samples collected from the recycling plants for particle analysis each weighed
between 400 and 525 g and were analyzed individually. All samples were air dried for at least 24 hours
in a fume hood before analysis. After drying, blades of synthetic turf in the field samples were removed
by hand.
The PSA was done using a stack of Hogentogler & Co, Inc. (Columbia, MD, USA) No. 10 (2.00-mm),
18 (1.00-mm), 60 (0.25-mm), 120 (0.125-mm), and 230 (0.63-mm) U.S. Standard Series test sieves
conforming to American Society for Testing and Materials (ASTM) Standard El 1 (ASTM International,
2017) specifications. For larger field samples, a No. 4 (4.75-mm) sieve was added on top of the stack
because the sample volume was too great to fit in the top (No. 10) sieve before analysis. The sieve stack
was placed on a vibratory sieve shaker (CSC Scientific, Inc., Fairfax, VA, USA), and the shaker was set
on intensity 5 and run for 15 minutes. After shaking, the mass of tire crumb retained on each sieve was
recorded and the percentage of each fraction was calculated. In synthetic turf field samples that
contained sand as part of the infill material, the rubber and sand were not separated as part of this
particle size assessment.
3.6.4 SEM and EPMA Particle Characterization
3.6.4.1 Background
The surface area-to-mass ratio of particles is inversely proportional to particle size; therefore, the size
distribution and elemental composition of the smallest sample size fractions separated by gravimetric
PSA could be useful data in assessing exposure potential to the chemical constituents of the tire crumb
rubber. Particles retained on the No. 230 sieve (0.63- to 0.125-mm nominal sieve opening) and the
particles collected in the pan in the PSA (< 0.63 mm) were analyzed by scanning electron microscopy
(SEM) and electron probe microanalysis (EPMA) to characterize size distribution and qualitative
elemental composition, respectively. Because of the complexity and time-intensiveness of these
65
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analyses, a subset of nine recycling plant and nine synthetic turf field samples were analyzed by SEM
and EPMA.
3.6.4.2 Sample Preparation
The entire contents of either the No. 230 sieve or the collection pan were transferred to a 76.2-mm (3-in)
diameter aluminum pan. The sample size was reduced by a cone and quarter method (U.S. EPA, 1993).
The process was repeated until the remaining material appeared to be sufficient for a loosely-spaced
layer over about a 38.1-mm (1.5-in) diameter area. This material was transferred to the center of a
second 3-in diameter aluminum pan, and the pan was gently tapped and tilted until such a layer was
formed. A 25.4-mm (1-in) diameter double-sided adhesive carbon PELCO tab™ on an aluminum SEM
stub (Ted Pella, Inc., Redding, CA, USA) was pressed onto the center of the layer to collect the
subsample to be analyzed.
3.6.4.3 SEM Imaging and Particle Size Distribution Analysis
Pre-determined locations in a 17-point double-cross pattern (i.e., on four bisecting lines) covering the
entire 25.4-mm (1-in) diameter sample were imaged at 25-kilovolt (kV) accelerating voltage.
Photographs were recorded at 150x and 1200x magnification, with a Sigma VP SEM backscattered
electron detector (BSD; Carl Zeiss AG, Oberkochen, Germany). The BSD provided qualitative
differentiation of particles according to the atomic number of the major constituent element (i.e.,
particles composed primarily of heavier elements appeared brighter). The tagged image file format
(TIFF) photographs from the BSD were processed using ImageJ freeware (ImageJ/Fiji, version 1.46r,
National Institutes of Health, Bethesda, MD; Ferreira and Rasband, 2012). The images were scaled
using the Set Scale function and adjusted with the Threshold function to minimize noise without losing
significant particle area. Areas with obvious substrate features and the metadata banner were cleared,
and the remaining area was processed with the Analyze Particles function for particle projected area in
square micrometer (|im2). A minimum area corresponding to 9 pixels was set to eliminate most
remaining noise. The projected particle area values from the 17 imaged locations were combined in a
Microsoft Excel spreadsheet. Histograms of particle projected area in two ranges - about 400 to 25,000
|im2 and 1 to 400 |im2 (corresponding to spherical particles about 20- to 173-|im and 1- to 20-|im
diameter in size, respectively) - were constructed, and the median and mean projected areas were
calculated.
3.6.4.4 Electron Probe Microanalysis
A Quantax energy dispersive EPMA system (Bruker Corporation, Billerica, MA, USA) on the SEM was
used for electron probe microanalysis. The 25-kV accelerating voltage of the SEM allowed elements
through about the first transition element series to be detected. A few particles from each imaged
location were selected for point analysis (i.e., stationary electron beam on a single point in the image).
The particles were selected to include a range of brightness, and therefore, presumably, a range of
elemental compositions. The X-ray spectrum of each particle was integrated over 30 s, and the peaks
were identified using the spectrometer software.
3.6.5 Microwave-Assisted Acid Extraction and ICP/MS Metals Analysis
A microwave-assisted extraction protocol was optimized to handle tire crumb rubber samples composed
of particles of varying sizes. This extraction protocol used EPA Method 3051A (U.S. EPA 2017a) as the
core digestion procedure and included a pre-digestion step. Optima™ grade concentrated hydrochloric
acid (HC1), 70% nitric acid (HNO3), and 30% hydrogen peroxide (H2O2) in water (Fisher Scientific
66
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International, Inc., Hampton, NH, USA) were used as reagents in the extraction, and a custom multi-
element standard solution (SCP Science, Quebec, Canada; Catalogue No. AQ0-008-122) was used as a
matrix spike standard. Tire crumb rubber from recycling plants and synthetic turf fields was dried and
weighed (250 mg) into a 100-mL XP-1500 Plus microwave digestion vessel with TFM® liner (CEM
Corporation, Matthews, NC, USA). A handheld static neutralizer gun (Quantum Instruments, Inc.,
Hauppauge, NY, USA) was used to reduce static charges within or on the surface of the rubber particles
and release particles clinging to the vessel's surface. Nitric acid and hydrochloric acid, 3:1 by volume,
was added to each sample. A total of 24 samples, including quality control (QC) samples, were prepared
at a time. The mixture of tire crumb and acids was allowed to react at room temperature for at least 30
minutes (min). The TFM® vessels were then sealed and placed in a MARS-5™ microwave digestion
unit fitted with a ESP-1500 Plus pressure sensor and RTP-300 Plus fiber optic temperature sensor
(temperature range -40 to 250 °C; CEM Corporation, Matthews, NC, USA), where the samples were
gently warmed to 120 °C within 30 min and kept at this temperature for an additional 20 min. This pre-
digestion step allowed enough time for the larger rubber particles to disintegrate rather than exploding in
the vessel. The microwaved samples were stored at room temperature overnight, giving additional time
for the acid mixture to permeate the rubber particles. After venting the vessels to release excess pressure
and replacing the safety membranes, the sample slurries were subjected to the full microwave digestion
regiment at 200 °C. Hydrogen peroxide (750 microliters [|iL]) was added to each cooled sample, which
was then diluted to 50 g with 18.2 megaohm (Mohm) deionized water and transferred into acid-cleaned
polyethylene bottles to await high resolution magnetic sector inductively coupled plasma mass
spectrometer (HR-ICPMS) analysis.
3.6.5.1 ICP/MS Analysis
Quantitative elemental concentration measurements of tire crumb rubber samples were carried out using
an Element 2™ HR-ICPMS (Thermo Finnigan, Bremen, Germany). The sample introduction system
consisted of a PFA micro nebulizer, cyclonic quartz spray chamber, and platinum sampler and skimmer
cones. All sample handling and analysis was performed in an ISO Class 5 Clean Room (ISO, 2015).
Tire crumb rubber sample acid digests (described above) were received as 18% HNO3, 6% HC1, and
1.5% H2O2 volume to volume (v/v) and gravimetrically diluted with 2% HNO3 and 0.5% HC1 (v/v).
External calibrations were performed with multi-element standards (High-Purity Standards, Charleston,
SC, USA), and prepared with 2% HNO3, 0.5% HC1, and 1% ethanol (v/v). An internal standard (IS)
solution (2 parts per billion [ppb] indium) was prepared at the matrix acid levels and introduced in-line
along with samples to account for analytical signal drift. National Institute of Standards and Technology
(NIST)-certified standard reference materials (SRM® 1640a and SRM® 1643f; NIST, Gaithersburg,
MD, USA) were used to verify instrument performance and analytical accuracy. Two instrument
methods were used based on the elements of interest, the instrument resolutions, and the sample dilution
factor. Instrument settings and method parameters are listed in Table 3-7. Although more isotope data
was collected, only the reported elements are listed in Table 3-7.
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Table 3-7. HR-ICPMS Method Settings and Parameters3
Instrument Setting
Value
Radio frequency (RF) power
1200-1260 watts (W)
Gas flow rate - Cool
17 liters per minute (1pm)
Gas flow rate - Auxiliary
0.9 - 1.2 1pm
Gas flow rate - Sample
0.9 - 1.20 1pm
Sample update rate
-100 |iL/min
Sampler cone (Pt)
1.1 -mm orifice diameter
Skimmer cone (Pt)
0.8-mm orifice diameter
Nebulizer
100-|iL Teflon microneb
Spray chamber
Cyclonic quartz
Detector dead time
30 nanoseconds (ns)
Internal standard solution
2.0 ppb solution of Indiuml 15 and Iridiuml93
Instrument Resolution
Reported Isotopes'*
Low resolution (LR)
Be9, Rb85, Sr88, Mo95, Cdlll, Sbl21, Bal37, Pb206, Pb207, Pb208, (Inll5,
Irl93)
Medium resolution (MR)
Mg24, A127, V51, Cr52, Fe57, Co59, Ni60, Cu63, Zn66, Snll8, (Inll5, Irl93)
High resolution (HR)
As75, Se77, Se78, Snll8, (Inll5, Irl93)
Acquisition Parameter
Low Resolution
Medium Resolution
High Resolution
Mass task window, %
100
125
150
Samples/peak
30
20
15-20
Sample time/ns
10
20-50
100-500
Scan type
E Scan
E Scan
E Scan
Detector mode (analog/counting)
Both
Both
Both
No. replicates (runs)
3
3
3
No. scans per replicate (pass)
2
2
2
Evaluation Parameters
Low Resolution
Medium Resolution
High Resolution
Search task window, %
100
100
80-100
Integration task window, %
40
60
60-70
Integration type
Avg
Avg
Avg
Calibration type
Weighted
Weighted
Linear
Internal standard (Indium/Iridium)
Indium
Indium
Indium
aHigh resolution magnetic sensor inductively coupled plasma mass spectrometry (HR-ICPMS) was conducted using an
Element 2™ HR-ICPMS.
b A1 = Aluminum; As = Arsenic; Ba = Barium; Be = Beryllium; Cd = Cadmium; Co = Cobalt; Cr = Chromium; Cu = Copper;
Fe = Iron; In = Indium; Ir = Iridium; Mg = Magnesium; Mo = Molybdenum; Ni = Nickel; Pb = Lead; Rb = Rubidium; Sb =
Antimony; Se = Selenium; Sn = Tin; Sr = Strontium; V = Vanadium; Zn = Zinc
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3.6.6 XRF Metals Analysis
Tire crumb rubber from recycling plants and synthetic turf fields was analyzed for X-ray fluorescence
(XRF). Tire crumb rubber samples from recycling plants were received as three 10-g samples, and
samples from synthetic turf fields were received as either 10-g composites prepared from all field
sampling locations or as 5-g samples from individual locations. All 5- or 10-g samples received for XRF
analysis were split into two samples using a soil splitter and placed into HDPE analysis cups covered
with a Mylar membrane.
Samples analyzed for particle size (gravimetric PSA) were also prepared for XRF analysis. For all
particle size fractions where enough material was retained on a sieve, two samples were taken from the
size fraction and placed into HDPE analysis cups covered with a Mylar membrane.
The XRF analysis was performed using an Innov-X Alpha Series™ X-Ray Fluorescence Spectrometer
(Innov-X Systems, Woburn, MA, USA). This unit is a portable analyzer with a mode for testing soil
media. The Innov-X XRF spectrometer was used in a test stand, with the sample cups placed Mylar side
down on the analysis window for testing. The XRF spectrometer was set to analyze for 300 seconds in
standard mode for heavy metals and 300 seconds for light element analysis. The analyzer then combined
the data from the two modes to give concentration data (in parts per million [ppm]) for a range of
elements. The data was downloaded from the analyzer and the target element results were reported for
each sample.
3.6.7 Solvent Extraction and Semivoiatiie Organic Compound (SVOC) Analysis
3.6.7.1 Tire Crumb Rubber Extraction
Prior to beginning extractions of tire crumb rubber for SVOC analysis, several solvents and solvent
combinations were tested as potential extraction fluids for the tire crumb rubber material. A 1:1 mixture
of acetone and hexane appeared to provide extracts with the greatest number/intensity of
chromatographic features, while not dissolving the tire rubber material, which was observed when
methylene chloride was used as the extraction solvent.
The solvent extraction method used in this study is not likely to completely extract all of the target
chemicals contained in the tire crumb rubber particles. While this method is not a total extraction
method, it is likely relevant with regard to the potential for human exposure. When combined with
ceramic homogenizers, the vortex extraction method was fairly aggressive and very efficient in terms of
throughput, which was very important given our tight timeline for completing the laboratory work. Prior
to using this method, multiple sequential extractions were evaluated using this technique and it was
determined that the majority of extractable organics were removed in the first extraction cycle. This
method was also evaluated for linearity across tire crumb mass, as well as precision of replicates and
was found to perform well across the range of semivoiatiie organics we were measuring. This method
has an advantage compared to more aggressive extraction techniques in that it minimizes the potential
for analyte losses due to no heating, solvent evaporation, or extensive sample handling. The use of
solvents or methods that would approach total SVOC extraction would result in residues that could
rapidly impair analytical systems, likely require more extensive time and effort in sample clean-up and
result in greater potential for analyte losses. (It is also important to note that the results of this study are
in general agreement with extractable SVOC measurement results from several other studies [shown in
tables in section 2] that used different extraction methods).
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Tire crumb rubber samples were stored in a freezer at -20 °C after receipt at the EPA laboratory. Prior to
extraction, the samples were allowed to warm to room temperature. The samples were homogenized
inside of their storage jars by shaking to cycle the contents from the bottom of the jar to the top of the
jar. Two separate 1-g aliquots were removed from each sample, shaking the sample jar between each
aliquot. Each 1-g aliquot was transferred to a clean 50-mL polypropylene centrifuge tube. An internal
standard solution (100 |iL) was added to each tube along with a ceramic homogenizer. A 10-mL volume
of 1:1 acetone:hexane was then added to each sample tube. The tubes were capped and vortex-mixed for
1 min, allowed to sit for 2 min, then vortex-mixed for an additional 1 min. The tubes were then
centrifuged at 4,000 revolutions per minute (RPM) for 5 min. The solvent was removed and transferred
to a 15-mL vial. A 1-mL aliquot of the extract was transferred to an autosampler vial for gas
chromatography tandem mass spectrometry (GC/MS/MS) analysis. The remaining extract was stored in
a freezer at -20 °C.
3.6.7.2 GC/MS/MS Analysis for Target SVOCs
SVOC extraction samples were analyzed using an Agilent Model 7890 gas chromatograph equipped
with a VF-5ms column (30 m x 0.25 mm, 0.25 |im) and a Model 7010 triple quadrupole mass
spectrometer (Agilent Technologies, Santa Clara, CA, USA). The GC/MS/MS parameters in Table 3-8
were used for data acquisition. The instrument was standardized using High Sensitivity Electron Impact
(EI) Autotune and was calibrated for target analytes in the range of 0.1 nanograms (ng)/mL to 500
ng/mL. Calibration checks were run using a mid-level standard between every 10 samples. Quantitation
was performed using linear regression curves generated from the responses and nominal concentrations
of calibration standard solutions.
Table 3-8. GC/MS/MS Parameters for Target SVOC Analysis3
System Component
Parameter
Value
Gas Chromatograph
Injector Mode
Capillary injector in splitless mode
Gas Chromatograph
Injector Split Ratio
Pulsed splitless at 25 pounds per square inch (psi) for 0.5 min,
then split at 50 mL/min at 1 min
Gas Chromatograph
Injector Temperature
250 °C
Gas Chromatograph
Injector Liner
Single gooseneck glass, deactivated
Gas Chromatograph
Injection Volume
1 nL
Gas Chromatograph
Column Flow
1.2 mL/min
Gas Chromatograph
Temperature Program
50 °C for 2 min to 325 °C at 10 °C/min, hold 5 min
Mass Spectrometer
Detector Mode
Electron Impact (EI) operating in Multiple Reaction
Monitoring (MRM)/Scan mode
Mass Spectrometer
Detector Tuning
Electron Multiplier Voltage by Gain Curve
Mass Spectrometer
Detector Transfer Line
Temperature
300 °C
a Gas chromatography tandem mass spectrometry (GC/MS/MS) was conducted using an Agilent 7890 gas chromatograph
with a VF-5ms column and an Agilent 7010 Triple Quadrupole mass spectrometer. SVOC = semivolatile organic compound
3.6.7.3 GC/MS Analysis for Non-Target SVOCs
A subset of the tire crumb extraction samples was subsequently submitted for non-targeted analysis
using an Agilent Model 6890 gas chromatograph equipped with a VF-5Sil ms column (60 m x 0.25 mm,
0.25 |im) and Model 5973 mass selective detector (MSD; Agilent Technologies, Santa Clara, CA, USA).
The instrument was standardized using EI Standard Spectrum Tune and was operated using the
parameters listed in Table 3-9. The mass spectral data were analyzed by deconvolution and spectral
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matching to the NIST (2011) Mass Spectral Database using Agilent MassHunter Workstation
Quantitative Analysis (Version B.07.01, Agilent Technologies, Santa Clara, CA, USA) Unknowns
Analysis.
Table 3-9. GC/MS Parameters for Non-target SVOC Analysis"
System Component
Parameter
Value
Gas Chromatograph
Injector Mode
Capillary injector in splitless mode
Gas Chromatograph
Injector Split Ratio
Splitless, then split at 50 mL/min at 0.75 min.
Gas Chromatograph
Injector Temperature
250 °C
Gas Chromatograph
Injector Liner
Single gooseneck glass, deactivated
Gas Chromatograph
Injection Volume
1 nL
Gas Chromatograph
Column Flow
1.2 mL/min
Gas Chromatograph
Temperature Program
40° C for 2 min to 340° C at 5° C/min, hold 5 min.
Mass Selective Detector
Detector Mode
Electron Impact (EI) operating in Scan mode
Mass Selective Detector
Detector Scan
Mass Range: 50-550 m/z (mass-to-charge ratio), Scan Rate:
Parameters
1.52 scans/s, Threshold: 1000
Mass Selective Detector
Detector Tuning
Electron Multiplier Voltage = Tune + 400
Mass Selective Detector
Detector Transfer Line
Temperature
300 °C
a Gas chromatography mass spectrometry (GC/MS) was conducted using an Agilent Model 6890 gas chromatograph with a
VF-5Sil ms column and an Agilent Model 5973 mass selective detector. SVOC = semivolatile organic compound
3.6.7.4 LC/TOFMS Analysis for Target SVOCs
Liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) analysis was performed to focus
on target SVOCs that were difficult to analyze by GC/MS/MS. A 1-mL aliquot of each of the 1:1
acetone:hexane sample extracts prepared for GC/MS/MS analysis was transferred to a vial and used for
LC/TOFMS analysis. A solvent exchange was used to prepare the sample extracts for analysis. The
extracts were first placed in a hood, and the solvent was allowed to evaporate at room temperature. This
was done to avoid the target analyte loss that can occur at temperatures greater than 60 °C. After
evaporation was complete, 1 mL of methanol was added to each vial to reconstitute the extract for
LC/TOFMS analysis.
A portion of the sample extract was added to a propylene autosampler vial containing 2-millimolar
(mM) ammonium acetate buffer to match the starting conditions (75% water:25% methanol) of the
mobile phase gradient used. Each vial was capped and vortexed to ensure mixing of the organic sample
with the aqueous buffer. The bottom of each vial was checked for air bubbles and if present, bubbles
were removed by tapping on the vial. After making sure that there were no air bubbles, the samples were
placed in the high-performance liquid chromatography (HPLC) autosampler and analyzed.
The LC/TOFMS analysis was performed using an Agilent 1100 HPLC equipped with an Eclipse Plus
C18 HPLC column (2.1 mm x 50 mm, 3.5 |im) with an injection volume loop of 40 |iL and interfaced
with an Agilent Model G1969A LC/MSD TOF System (Agilent Technologies, Santa Clara, CA, USA).
A 45-min gradient HPLC run was used with mobile phase components of methanol and 2-mM formate
or acetate buffer, at a flow rate of 300 |iL/min (Table 3-10). Electrospray ionization was used in the
mass spectrometer source, which was maintained at 325 °C. Molecular weights for the 10 LC/TOFMS
target analytes are shown in Table 3-11.
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Table 3-10. HPLC Gradient Program Used for Characterization of Tire Crumb Rubber Samples'
Time (min)
Flow Rate (mL/min)
%Ab
%BC
0
0.2
75
25
25
0.2
20
80
40
0.2
0
100
45
0.2
0
100
Post time (4 mins)
0.2
75
25
a High-performance liquid chromatography (HPLC) analysis was conducted using and Agilent 1100 HPLC System.
b Mobile phase component A consisted of 2-mM ammonium formate or acetate in deionized water
0 Mobile phase component B consisted of methanol; acetonitrile was used for additional assay, if needed
Table 3-11. List of Target SVOC Analytes for LC/TOFMS Analysis
Target SVOC Analytes1*
CAS Number1
Molecular Weight
grams/mole (g/mol)
Resorcinol
108-46-3
110.11
Phthalimide
85-41-6
147.13
1 -Hydro xypyrene
5315-79-7
218.26
Cyclohexylamine
108-91-8
99.18
Dicyclohexylamine
101-83-7
181.32
N-cyclohexyl-N-methylcyclohexanamine
7560-83-0
195.35
2-Mercaptobenzothiazole
149-30-4
167.25
2-Hydroxybenzothiazole
934-34-9
151.19
Diisononyl phthalate
28553-12-0
418.62
Diisodecyl phthalate
26761-40-0
446.67
11 Liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) was conducted using an Agilent 1100 HPLC
equipped with an Eclipse Plus C18 HPLC column (2.1 mm x 50 mm, 3.5 |im) and an Agilent Model G1969A LC/MSD TOF
System
b SVOC = semivolatile organic compound
0 Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
3.6.7.5 LC/TOFMS Suspect Screening and Analysis of Non-target SVOCs
Suspect screening and non-targeted screening of tire crumb rubber sample extracts were performed
using an Agilent 1100 HPLC equipped with an Eclipse Plus C18 HPLC column (2.1 mm x 50 mm, 3.5
|im) with an injection volume loop of 40 |iL and interfaced with an Agilent Model G1969A LC/MSD
TOF (Agilent Technologies, Santa Clara, CA, USA). The same solvent exchange procedure and
chromatographic procedure used for target SVOC analysis was applied to all the extracts. A portion of
the reconstituted sample extract was added to a propylene auto-sampler vial containing 2-mM
ammonium acetate buffer to match the starting conditions (75% water:25% methanol) of the mobile
phase gradient used. Each vial was capped and vortexed to ensure mixing of the organic sample with the
aqueous buffer. The bottom of each vial was checked for air bubbles and if present, bubbles were
removed by tapping on the vial. After making sure that there were no air bubbles, the samples were
placed in the HPLC autosampler and analyzed. A 45-min gradient HPLC run was used with mobile
phase components of methanol and 2-mM formate or acetate buffer at a flow rate of 300 |iL/min.
Electrospray ionization was used in the mass spectrometer source, which was maintained at 325 °C.
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Non-targeted analysis (NTA) and suspect screening do not use traditional calibration standards.
However, a series of known calibration compounds in an original equipment manufacturer (OEM)
solution can be used to mass calibrate the instrument daily before its use and to auto-tune the TOFMS
instrument. Agilent ESI-L Low Concentration Tuning Mix (Agilent Part No. G1969-85000, Agilent
Technologies, Santa Clara, CA, USA) was used to assure the mass accuracy of the instrument on a
regular basis. In addition, solutions with a second set of known compounds (called reference
compounds) were continually infused into the TOFMS for real-time mass correction. These reference
compounds and their source solutions were:
• purine [exact mass = 120.043596]:
5-mM purine in acetonitrile:water (Agilent Part No. 18720242, Agilent Technologies, Santa
Clara, CA, USA),
• HP0921 hexakis (lH,lH,3H-tetrafluoropropoxy) phosphazene [exact mass = 921.002522]:
2.5-mMHP0921 in acetonitrile:water (Agilent Part No. 18720241, Agilent Technologies, Santa
Clara, CA, USA), and
• tetrahydroperfluorononanoic acid (THPNA) [exact mass = 391.0009]:
1000 ng/|iL THPNA (not Agilent reference solution)
Reference solutions were created for both the positive and negative analytical modes of the analysis
using these reference compounds:
• Reference Solution for Positive Mode Dual Electrospray Ionization (ESI) Analysis
o 500 mL of Acetonitrile:deionized water (90:10)
o 1.5 mL of Agilent 5-mM purine solution
o 750 |iL Agilent 2.5-mM HP0921 solution
• Reference Solution for Negative Mode Dual ESI Analysis
o 1000 mL of Acetonitrile:deionized water (90:10)
o 300 |iL of Agilent 5-mM purine solution
o 150 |iL Agilent 2.5-mM HP0921 solution
o 100 |iL of 1000 ng/|iL solution of THPFNA
In addition, any known compound that was not expected to be present in the samples and had an exact
mass could be added. Depending on the polarity of the instrument and the mobile phase modifiers used,
different reference masses were seen. Refer to Table 3-12 for additional references masses and forms
used in this analysis.
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Table 3-12. Reference Masses for Real-time Mass Correction in TOFMS Analysis3
Species
Positive Ion m/z
Negative Ion m/z
CF3 (trifluoro acetic acid [TFA] fragment)
N/A
68.995758
TFA anion
N/A
112.985587
purine
121.050873
119.036320
HP0921
922.009798
N/A
HP0921 (formate adduct)
N/A
966.000725
HP0921 (acetate adduct)
N/A
980.016375
HP0921 (TFA adduct)
N/A
1033.988109
THPFNA
N/A
391.0009
aTOFMS= Time-of-flight mass spectrometry; m/z = Mass-to-charge ratio; CF3 = Trifluoromethyl; N/A = Not
applicable; TFA = Trifluoro acetic acid; THPFNA = Tetrahydroperfluorononanoic acid
All method and matrix blanks, quality control samples, calibration standards, replicates, and unknown
samples were subjected to the same sample preparation and analysis. The samples were analyzed in both
positive and negative modes and subjected to a molecular feature extraction (MFE) algorithm to identify
peaks for further exploration. Features identified for suspect screening purposes were compared to
EPA's Distributed Structure-Searchable Toxicity (DSSTox) Database of approximately 750,000
chemicals (https://www.epa.gov/chemical-research/distributed-structure-searchable-toxicitv-dsstox-
database). Chemicals matching within 5 ppm of the suspect chemical according to accurate mass and
scoring >80% were deemed as a provisional match. Features not matching were subjected to a non-
targeted screening workflow where the features were prioritized based on occurrence and abundance
into discrete data packets. Features were also compared with a personal compound database list (PCDL)
that included previously reported SVOCs in the literature related to tire crumb.
3.6.8 Dynamic Chamber Emissions Testing
3.6.8.1 Tire Crumb Material Preparation for Emission Chamber Tests
Tire crumb rubber samples from tire recycling plants and synthetic turf fields were received in amber
glass bottles with chain of custody records. The samples were then stored in the freezer at < -15 °C until
several hours before testing, at which time they were removed from the freezer and allowed to warm to
room temperature before being placed in the testing chambers.
3.6.8.2 Selection of Test Chambers and Conditions
Constituents such as VOCs and SVOCs can be released to the environment from tire crumb rubber
under different environmental conditions. Laboratory chamber dynamic emission tests were performed
to characterize the emissions of VOCs and SVOCs from tire crumb rubber and tire crumb rubber infill
under two different chamber conditions (i.e., 25 °C and 50% relative humidity [RH]; and 60 °C and
approximately 7% RH) and defined air change rates. The selection of appropriate testing chambers and
test conditions is an important part of the testing. For VOCs, the small (53-L) chamber tests were
selected to be consistent with methods described in the ASTM Standard Guide D5116-10 (ASTM,
2010). A chamber air exchange rate of one air change per hour, an equilibration period of 24 h, and a
15-g sample size were selected both for consistency with the ASTM method and through initial testing
to determine the best conditions for obtaining usable analysis results. Selecting appropriate chamber
systems and conditions for measuring SVOC emissions is more challenging. SVOC adsorption to
chamber walls limits the use of chambers with large relative surface areas (such as the 53-L chamber) to
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experiments requiring long equilibration durations (many days to weeks). Therefore, micro-chambers
were selected, having volumes of 44 or 114 mL, minimizing chamber to sample surface area ratios.
Chamber air exchange rates of 28 - 32 air changes per hour, an equilibration period of 24 h, and a 10-g
sample size were selected through initial testing for determining the best conditions for obtaining usable
analysis results in reasonable time periods.
3.6.8.3 Small Chamber Emission Tests
Small Chamber Emission Test Method for VOCs
VOC and formaldehyde source emission tests were conducted in 53-L electro-polished stainless-steel
chambers in Model SCN4-52 temperature-controlled incubators (So-Low Environmental Equipment
Co., Inc., Cincinnati, OH, USA; Figure 3-12A). An OPTO 22 Data Acquisition System (OPTO 22,
Temecula, CA, USA) was used for continuous recording of the outputs of the mass flow controllers,
temperature, and relative humidity (RH) probes in the chambers. Emissions of VOCs and formaldehyde
were measured under two different chamber environmental conditions: 1 h"1 air change per hour (ACH),
25 °C, and 45% RH; and 1 h"1 ACH, 60 °C and 7% RH.
Chamber background samples were collected prior to the test material being loaded into the chambers.
During tests, clean VOC-free air was supplied to the chambers. For each test, 15 g of tire crumb rubber
material was placed in the center of the small chamber floor on an aluminum weighing pan (Figure 3-
12B, C). After the test material had been in the chamber for 24 hours, air samples were collected at the
chamber exhaust glass manifold using Carbopack™ X Fence Line Monitor (FLM) tubes (Sigma-
Aldrich, Saint Louis, MO, USA) at 100 mL/min for 60 minutes and 2, 4-dinitrophenylhydrazine
(DNPH) cartridges (Waters Corporation, Milford, MA, USA) at 400 mL/min for 90 minutes (Figure 3-
12D). Field blank and duplicate samples were collected, and 12 duplicate tests were conducted. After
sampling, Carbopack™ X samples were capped and placed individually into glass culture tubes in the
refrigerator at < 4 °C until analysis.
Tests with two tire crumb materials (one recycling plant sample and one synthetic turf field sample)
were also conducted using these same small chamber environmental conditions and air sample
collection procedures to determine VOC and formaldehyde emission profiles. Carbopack™ X and
DNPH samples were collected at 1, 2, 4, 8, 24, and 48 hours after materials were placed inside the
chamber.
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Figure 3-12. Small emission chamber set-up, including A) sealed 53-L
chamber in incubator cabinet; B) 15 g tire crumb rubber infill sample
prepared for testing; C) chamber interior with sample in place and
mixing fan pulled out; D) external manifold for air sample collection.
Silicone wristbands are increasingly being used as personal exposure samplers. They operate by
passively absorbing organic chemicals from a person's environment while they are worn. To understand
how silicone wristbands might be used in future exposure measurement studies of synthetic field users, a
separate set of wri stband tests were conducted in the small chambers with four different tire crumb
rubber materials (one recycling plant sample and three synthetic turf field samples) at 25 °C, 1 h"1 ACH,
and 45% RH. For each test, 60 g of tire crumb material was used to cover a wristband in an aluminum
foil tray with an internal diameter of 9 cm. The tray was then placed in the center of the chamber floor.
Another two wristbands were suspended over the tray. SVOC air samples were collected on ORBO™
1000 pre-cleaned small polyurethane foam (PUP) cartridges (Sigma-Aldrich, Saint Louis, MO, USA)
after the chamber was sealed. Air sample collections began at 0, 48, and 112 hours, and the sampling
durations for the three PUF sample collections were 48, 64, and 48 hours at 100 mL/min. Wristbands
were moved out of the chamber to tightly sealed glass jars after the test and stored in the freezer until
solvent extraction.
HPLC/UV Analysis of Chamber Emission Samples for Formaldehyde
Air samples collected on DNPH cartridges were extracted with 5 mL acetonitrile within 7 days after
sampling and analyzed using an Agilent 1200 JTPLC equipped with an Eclipse XDB-C18 column (4.6 m
x 150 mm, 5(.im) and a diode array detector (DAD; Agilent Technologies, Santa Clara, CA, USA). The
HPLC was calibrated using an external standard method with formaldehyde-DNPH in the range of 0.03
to 15 jig/mL. Formaldehyde-DNPH detection in selected samples was confirmed by LC/TOFMS.
TD/GC/TOFMS Analysis of Chamber Emission Samples for VOCs (Targeted and Non-Targeted
Analysis)
Carbopack™ X Fence Line Monitor (FLM) sorbent tube samples transferred to the VOC laboratory by
the Chamber Emissions Testing staff were removed from the refrigerator (where they were stored at 6
°C) and were allowed to come to room temperature prior to analysis. Samples were analyzed using a
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Unity 2™ Ultra 50:50™ thermal desorption (TD) system (Markes International, Inc., Gold River, CA,
USA) interfaced to an Agilent 7890B gas chromatograph equipped with an Rxi-ms column (60 m x 0.32
mm, 1 |am; Agilent Technologies, Santa Clara, CA, USA) and a Markes International BenchTOF™
Select MSD System (Markes International, Inc., Gold River, CA, USA). The instrument was tuned using
the AutoOpt function and was calibrated using an internal standard method with concentrations of target
compounds in the nominal range of 0 to 50 parts per billion by volume (ppbv) per compound. Internal
standards were manually loaded onto all tubes analyzed, including calibration tubes, QC samples, and
field samples. The actual mass loading (in ng/tube) depends on the molecular weight of the individual
compound and the loaded volume of gaseous calibration standard. For example, mass loadings in the
nominal range of 0 to 160 ng/tube benzene and 0 to 260 ng/tube benzothiazole were observed for the
calibration curve. Calibration checks were run using a low-level standard between every 11 samples.
The TD/GC/TOFMS instrument operating parameters are shown in Table 3-13.
MSD ChemStation Enhanced Data Analysis Software (Version E.02.02.1431, Agilent Technologies,
Santa Clara, CA, USA) was used for peak identification/integration and combination of individual files
into a database. The database was exported to Microsoft® Excel (Office 365, Microsoft Corporation,
Redmond, WA, USA) for final data reduction. Quantitation was performed using quadratic curves
generated from the relative response ratios and concentration ratios of internal standards and calibration
standards. Inherent artifacts of target compounds found on Carbopack™ X sorbent (e.g., benzene) were
addressed through the use of blank corrected calibration curves. VOC results were reported as ng/tube.
The volume of chamber air pulled through the Carbopack™ X FLM sorbent tube was used to calculate
the analyte concentration (ng/L).
Table 3-13. TD/GC/TOFMS Parameters for VOC Chamber Emission Sample Analysis3
System Component
Parameter
Value
Thermal Desorption System
Trap
TO-15/TO-17 air toxics focusing trap
Thermal Desorption System
Split Flows
Inlet split - none; Outlet split - 25:1
Gas Chromatograph
Column Flow
1.5 mL/min
Gas Chromatograph
Temperature Program
Initial: Set point 30 °C, hold for 10 min
Ramp 1: Rate 5 °C/min to set point 130 °C, hold 0 min
Ramp 2: Rate 20 °C/min to set point 200 °C, hold 5.5 min
Ramp 3: Rate 20 °C/min to set point 220 °C, hold 7.5 min
Mass Selective Detector
Mass Range
Mass range: 35-350 mass to charge ratio (m/z)
Mass Selective Detector
Data Rate
3 Hertz (Hz)
Mass Selective Detector
Transfer Line Temperature
250 °C;
Mass Selective Detector
Ion Source Temperature
280 °C
Mass Selective Detector
Voltage
Ionization Voltage = 70 electronvolt (eV); Filament
voltage =1.6 volt (V)
Mass Selective Detector
Filament Drops
10.40 to 11.67 min: 1.53 V
22.33 to 23.25 min: 1.53 V
38.10 to 38.49 min: 1.53 V
a Thermal desorption/liquid chromatography/time-of-flight mass spectrometry (TD/LC/TOFMS) was conducted using a Unity
2™ Ultra 50:50™ Thermal Desorption (TD) system interfaced to an Agilent 7890B gas chromatograph equipped with a Rxi-
ms column (60 m x 0.32 mm, 1 |im) and Markes International BenchTOF™ Select Mass Selective Detector System. VOC =
Volatile organic compound
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3.6.8.4 Micro-Chamber Emissions Tests
Micro-Chamber Emission Test Method for SVQCs
Emissions testing for SVOCs was not performed using the same small chambers used for VOCs because
the relatively large chamber wall surface area, and SVOC adsorption to those walls would result in
prohibitively long times to reach steady-state conditions. To minimize chamber wall surface effects and
to speed emissions testing, SVOC source emission tests were conducted using two micro-chamber
systems - the Model u-CTE™ and M-CTE250™ Micro-Chamber/Thermal Extractor™ (Markes
International, Inc., Gold River, CA, USA). The Model M-CTE250™ system consists of four 114-mL
micro chambers, and the Model u-CTE™ system (Figure 3-13 A) consists of six 44-mL micro chambers
that allow up to six sample materials to be tested simultaneously at the same temperature and flow rate
(Figure 3-13C). During tests, clean air flow from the same clean air system used in the small chamber
was supplied to the micro chambers. The micro chambers were operated at a flow rate of 60 mL/min,
resulting in an air exchange rate of 82 ACH at 25 °C or 72 ACH at 60 °C for the ji-CTE™ system and
32 ACH at 25 °C or 28 ACH at 60 °C for the M-CTE250™ system. Both systems have temperature and
humidity control, which allowed the tests to be conducted at 45% RH at 25 °C or 7% RH at 60 °C.
Temperature, RH, and air flow measurements were manually recorded. Prior to each test, the micro
chambers were cleaned.
Figure 3-13. Micro chamber set-up, including A) ji-CTE™ system; B) 10 g tire
crumb rubber infill samples in micro-chamber cups; C) samples placed in micro
chamber for testing.
For each of the emission tests, 10 g of tire crumb rubber sample material was placed in a micro chamber
(Figure 3-13B). After the test material had been in the chamber for 24 hours, one SVOC air sample was
collected on a PL F cartridge at the exhaust port of each micro chamber at 60 mL/min for 180 minutes.
Chamber background and field blank samples were collected. Twelve duplicate tire crumb rubber
sample tests were also conducted. After sampling, PUF samples were capped, wrapped in clean
aluminum foil in pre-labeled plastic bags, and stored in the refrigerator at < 4°C until transfer to the
analysis laboratory.
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Tests with two tire crumb materials (one recycling plant sample and one synthetic turf field sample)
were also conducted using the same micro chamber environmental conditions and air sample collection
procedures to determine SVOC emission profiles. PUF samples were collected at 1.5, 5.5, 9, 24, and 48
hours.
GC/MS/MS Targeted Analysis of Chamber Emission Samples for SVOCs
Micro chamber emissions samples for SVOC analysis were collected on 22-mm x 7.6-cm PUF plugs.
After collection, the glass sample tubes containing the PUF plugs were wrapped in foil and were placed
into individual zip-top bags. The samples were stored in a freezer at approximately -20 0 C until
removed for extraction. For each sample, a 250-mL narrow-mouth glass collection bottle was labelled
and fitted with a glass funnel. After the samples had warmed to room temperature, they were removed
from the bag and foil and the PUF plug was transferred to an appropriately-labelled, clean 60-mL glass
sample jar, using stainless steel forceps. The glass tube that contained the PUF plug was rinsed into the
corresponding collection bottle with approximately 5 mL of 1:1 acetone:hexane. Each sample jar was
filled with 50 mL of 1:1 acetone:hexane and sealed with a polytetrafluoroethylene (PTFE)-lined cap.
The jars were placed in an ultrasonic cleaner with water level well below the level of the jar cap. The
ultrasonic cleaner was then turned on for 15 minutes. Sample jars were removed from the cleaner and
the extracts were transferred through funnels into the corresponding collection bottles. The funnels were
rinsed with 1:1 acetone:hexane from a wash bottle after the extracts were added. The solvent addition,
extraction and transfer was repeated two more times. The combined extracts in the collection bottles
were then evaporated to 2-5 mL using a parallel evaporator (Buchi Multivapor model P-6, Flawil,
Switzerland). The concentrated extracts were transferred to a 15-mL graduated glass tube, along with
two 2-mL 1:1 acetone:hexane rinses of the collection bottle, prior to being concentrated to a final
volume of 1 mL under nitrogen. The extracts were then transferred to autosampler vials (Agilent
Technologies, model 5182-0716, Santa Clara, CA, USA) for analysis.
Emissions sample extracts were analyzed using an Agilent Model 7890 gas chromatograph equipped
with a VF-5ms column (30 m x 0.25 mm, 0.25 |im) and a Model 7010 triple quadrupole mass
spectrometer (Agilent Technologies, Santa Clara, CA, USA). The same parameters previously described
in Table 3-8 were used for data acquisition. The instrument was standardized using High Sensitivity EI
Autotune and was calibrated for target analytes in the range of 0.1 ng/mL to 500 ng/mL. Calibration
checks were run using a mid-level standard between every 10 samples. Quantitation was performed
using linear regression curves generated from the responses and nominal concentrations of calibration
standard solutions. Data were processed using Agilent MassHunter Workstation Quantitative Analysis
(Version B.07.01), Agilent Technologies, Santa Clara, CA, USA) and exported to Microsoft Excel
(Office 365) for further data reduction.
GC/MS Non-Targeted Analysis of Chamber Emission Samples for SVOCs
A subset of the emissions sample extracts was subsequently submitted for non-targeted analysis using an
Agilent Model 6890 gas chromatograph equipped with a VF-5Sil ms column (60 m x 0.25 mm, 0.25
|im) and Model 5973 mass selective detector (MSD; Agilent Technologies, Santa Clara, CA, USA). The
instrument was standardized using EI Standard Spectrum Tune and was operated using the same
parameters previously listed in Table 3-9. The mass spectral data were analyzed by deconvolution and
spectral matching to the NIST (2011) Mass Spectral Database using Agilent MassHunter Workstation
Quantitative Analysis (Version B.07.01, Agilent Technologies, Santa Clara, CA, USA) Unknowns
Analysis.
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LC/TOFMS Targeted Analysis of Chamber Emission Samples for SVOCs
A subset of the emissions samples generated for SVOC analyses was analyzed by LC/TOFMS to
explore whether significant emissions of chemicals amenable to LC/MS analysis could be observed. All
samples collected under the 60 °C emission test condition and a smaller number of the samples collected
under the 25 °C emission test condition were analyzed by LC/TOFMS. The solvent exchange procedure
and the analyses procedures described in section 3.6.7 for LC/TOFMS analysis of target SVOCs were
also used for LC/TOFMS analysis of the SVOC emission sample extracts.
3.6.9 Bioaccessibility Testing
All in vitro bioaccessibility testing was conducted at CDC's National Institute of Occupational Safety
and Health (NIOSH). Validated in vitro bioaccessibility methods did not exist for metals in tire crumb
rubber samples when this study was conducted. Therefore, the methods used in this study were based on
modifications of existing in vitro bioaccessibility methods for other solid materials, such as EPA
Method 1340, "In Vitro Bioaccessibility Assay for Lead in Soil" (U.S. EPA, 2017c).
3.6.9.1 Preparation of Artificial Biofluids
In vitro bioaccessibility testing was conducted to assess bioaccessibility of 20 metals in three artificial
biofluids (i.e., gastric fluid, saliva and sweat plus sebum). The artificial biofluids used in the in vitro
accessibility testing were prepared based on previously published formulations, after removing
ingredients that contained metals of interest. Artificial gastric fluid was prepared using an existing
formulation by Stefaniak et al. (2010a), after removing copper (II) chloride dihydrate and cobalamine
concentrate. Artificial sweat was prepared using an existing formulation by Harvey et al. (2010), after
removing cadmium chloride anhydrous, copper (II) chloride dehydrate, iron sulfate heptahydrate,
manganese (II) chloride, and lead, nickel and zinc reference solutions. Artificial saliva and sebum were
prepared using previously published formulations by Simoneau and Rijk (2001) and Stefaniak et al.
(2010b), respectively, without any modification.
For artificial gastric fluid, saliva and sweat, 5 L of each artificial biofluid was prepared, aliquoted into
500-mL bottles, and stored at -20 °C until usage. For artificial sebum, 500 mL was prepared and stored
at 4 °C until usage.
3.6.9.2 Extraction of Tire Crumb Rubber Constituents in Artificial Biofluids
Eighty-two tire crumb rubber samples (27 individual recycling plant samples and 55 individual or
composite synthetic turf field samples) were placed in the artificial biofluids for bioaccessibility testing.
All experiments were performed at a typical body temperature of 37 °C. Extraction of tire crumb rubber
constituents in artificial saliva and gastric fluid was conducted using a protocol modified after EPA
Method 1340 (U.S. EPA, 2017b). A 2±0.005 g portion of each of the tire crumb rubber samples
identified for bioaccessibility testing was weighed on a calibrated Mettler B303 balance (Mettler-
Toledo, LLC, Columbus, OH, USA) and put in a 15-mL polypropylene conical centrifuge tube (BD
Biosciences, San Jose, CA, USA). Artificial biofluids (8 mL at 37 °C) were dispensed into each tube and
rotated (220±2 rpm, 25.4-mm (1-in) stroke) at 37 °C for one hour, using a New Brunswick Innova® 40
shaking incubator (Eppendorf, Hauppauge, NY, USA). The sample mixture was then centrifuged using a
Sorvall™ Super T21 (ThermoFisher Scientific, Waltham, MA, USA) at 1500 x g relative centrifugal
force (RCF) for 30 min, after which 5-6 mL of the artificial biofluid extract was decanted to a clean
conical centrifuge tube, capped, and refrigerated at 4 °C until analyses for metals.
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Tire crumb rubber samples were also extracted in artificial sweat and sebum with compositions that
closely approximated human sweat. First, 0.5 mL of artificial sebum was used to coat each centrifuge
tube, and the coated tube was allowed to dry for 1 hour. The tubes were then inverted and allowed to
drip dry for an additional 30 minutes. The extraction of tire crumb rubber constituents in artificial sweat
was conducted in the sebum-coated tubes following the same protocol used to extract the tire crumb
rubber constituents in artificial saliva and gastric fluid.
3.6.9.3 Analytical Methods for Measuring Metals in Biofluids Extracts
Measurements of 20 metals (shown in Table 3-14) were carried out in the artificial biofluid extracts by
Maxxam Laboratories (Novi, MI, USA) following established EPA methods.
Table 3-14. Methods for Measuring Metals in Biofluid Extract
Analvtc
Method"
Aluminum
ICP/AES
Antimony
ICP/MS
Arsenic
ICP/MS
Barium
ICP/MS
Beryllium
ICP/MS
Cadmium
ICP/MS
Chromium
ICP/MS
Cobalt
ICP/MS
Copper
ICP/MS
Iron
ICP/AES
Lead
ICP/MS
Magnesium
ICP/AES
Manganese
ICP/MS
Mercury
Cold vapor atomic absorption
Molybdenum
ICP/MS
Nickel
ICP/MS
Selenium
ICP/MS
Strontium
ICP/MS
Tin
ICP/AES
Zinc
ICP/AES
11ICP/AES = inductively coupled plasma/atomic emission spectrometry;
ICP/MS = inductively coupled plasma/mass spectrometry
For metals analysis (with exception of mercury), artificial biofluid extracts were first subjected to acid
digestion following the EPA Method 3010 (U.S. EPA, 1992). All samples were then analyzed using
both inductively coupled plasma-atomic emission spectrometry (ICP/AES) following EPA Method
6010D (U.S. EPA, 2014a) and inductively coupled plasma-mass spectrometry (ICP/MS) following EPA
Method 6020B (U.S. EPA, 2014b). For these analyses, 2.0 mL of the sample aliquot was combined with
1.5 mL of 15.6-M nitric acid and 2.5 mL of 12.1-M hydrochloric acid and heated for 30 min at 95 °C.
After cooling to room temperature, the digestates were brought up to a final volume of 20 mL (1:10
dilution) and analyzed using both an Agilent 7900 ICP-MS (Agilent Technologies, Inc., Santa Clara,
CA, USA) and a Dual-view Optima™ 5300DV ICP-OES (PerkinElmer Inc., Waltham, MA, USA).
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For mercury analysis, artificial biofluid extracts were digested and analyzed using a cold vapor atomic
absorption procedure following the EPA Method 7470 (U.S. EPA, 1994). A 2.0-mL portion of the
sample aliquot was combined with 0.63 mL of 15.6-M nitric acid, 1.3 mL of sulfuric acid, and 3.75 mL
of 5% potassium permanganate (KMnC>4), diluted to 20 mL (1:10 dilution) with deionized water, and
heated for two hours at 95 °C. After cooling to room temperature, the digestates were brought up to a
final volume of 30 mL and analyzed using a QuickTrace® M-7600 Cold Vapor Atomic Absorption
(CVAA) Mercury Analyzer (Teledyne Leeman Labs, Hudson, NH, USA).
3.6.9.4 Calculation of In vitro Bioaccessibility
The amount of target analyte in the in vitro bioaccessibility extraction was calculated by multiplying the
analyte concentration in extract with the volume of the biofluid extract and dividing by the weight of the
tire crumb rubber sample used. The in vitro percent bioaccessibility value was determined by dividing
the amount of analyte extracted in the in vitro extraction by the concentration of the corresponding
analyte in the tire crumb rubber sample and multiplying by 100.
In vitro percent bioaccessibility was calculated for 19 of the 20 measured metals. Mercury was not
measured in the tire crumb constituent analyses, and therefore, in vitro percent bioaccessibility of
mercury could not be calculated.
In vitro bioaccessibility testing was not completed for SVOCs in the tire crumb rubber due to the large
number of target SVOC analytes, insufficient knowledge of SVOC levels in the tire crumb rubber
samples, lack of an existing validated method for in vitro bioaccessibility test of SVOCs in other solid
materials, and insufficient time and capacity for method development and optimization.
3.6.10 Microbial Analysis
3.6.10.1 Isolation of Microbes and Microbial Genomic DNA
Upon receipt, the individual location samples for microbe analysis were held at 4 °C. All samples were
processed the day they were received. From each sample, 5 g of tire crumb rubber was transferred to a
sterile, 50-mL polypropylene conical tube. To collect microbes from the tire crumb rubber, 20 mL of a
filter-sterilized solution composed of 0.005% weight-to-volume (w/v) sodium polyphosphate, 0.005%
(v/v) Tween®-80, and 0.0005%) (v/v) Antifoam Y-30 Emulsion (all manufactured by Sigma-Aldrich
Corporation, St. Louis, MO, USA) was added to the tube. The tube was then vortexed at max speed for 2
min using a Vortex-Genie (Scientific Industries, Inc., Bohemia, NY, USA). The supernatant was then
filtered through a 0 .45 - (am nitrocellulose membrane filter (Pall Corporation, Port Washington, NY,
USA), and the filter apparatus was washed twice with 15 mL of sterile IX Dulbecco's Phosphate Buffer
Saline (Sigma-Aldrich Corporation, St. Louis, MO, USA). The membrane filters were then aseptically
transferred to a bead tube from the PowerWater® DNA Isolation Kit (MoBio Laboratories, Inc.,
Carlsbad, CA, USA) and stored at -20 °C. The genomic deoxyribonucleic acid (DNA) of the microbes
recovered from the tire crumb rubber was extracted using the PowerWater® DNA Isolation Kit, per the
manufacturer's instructions. Genomic DNA was eluted in 100 |iL of elution buffer, and the total DNA
yield was determined immediately using the Qubit™ Double-stranded DNA (dsDNA) High-Sensitivity
(HS) Assay Kit (ThermoFisher Scientific, Waltham, MA, USA), per the manufacturer's instructions.
DNA extracts were stored at -80 °C. Positive and negative controls were implemented for elution from
tire crumb rubber and extraction of genomic DNA (all quality control results are reported in
Appendix E).
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3.6.10.2 Quantification of Targeted Microbial Genes
The QX200™ AutoDG™ Droplet Digital™ PCR System (BioRad Laboratories, Inc., Hercules, CA,
USA) was used to determine the quantities of 16S ribosomal ribonucleic acid (rRNA) genes (an
indicator of total bacteria), the Staphylococcus aureus SA0140 protein gene, and the gene for methicillin
resistance (mecA) in the tire crumb rubber samples. For each sample, duplicate 25-|iL droplet digital
PCR (ddPCR™) reactions were prepared that contained IX ddPCR Supermix for Probes (No dUTP,
BioRad Laboratories, Inc., Hercules, CA, USA), 5 |iL of extracted sample, 900 nanomolar (nM) each of
forward and reverse primer, and 250 nM probe. When necessary, dilutions of extracted DNA were made
with 10-mM Tris-HCl at pH 8.5. The BACT2 primer-probe assay described by Suzuki et al. (2000) was
used to quantify the 16S rRNA gene. The S. aureus and mecA genes were quantified using the primer-
probe assays from Kelley et al. (2013). An internal amplification control (IAC) was implemented for
each sample to monitor potential PCR inhibition. A synthetic custom minigene (Integrated DNA
Technologies, Inc., Coralville, IA, USA) containing the sequence to the IAC described in EPA Method
1615 was obtained and detected with the primer and probe assay described in EPA Method 1615 (Fout
et al., 2016). Droplets were made in the QX200™ AutoDG™ Droplet Digital™ PCR, which was
operated at 95 °C for 5 min, followed by 50 cycles of 95 °C for 30 sec and 60 °C (55 °C for mecA) for 1
min, and a final incubation at 98 °C for 10 min. PCR amplification was determined with the QX200™
Droplet Reader. An IAC was implemented for each sample to monitor potential PCR inhibition. To
determine gene concentrations in each ddPCR™ reaction, thresholds were set manually at the amplitude
mean +10 times the standard deviation (SD) of the droplets in the negative control reactions. Quantities
of the microbial genes per gram were determined after accounting for l/20th of the genomic DNA
extract used in the ddPCR™ reaction and considering that the total volume of the genomic DNA extract
was from 5 g of tire crumb rubber. Results were reported as targeted molecules per gram of tire crumb
rubber. Non-parametric t-test and one-way analysis of variance (ANOVA) were performed in
SigmaPlot™ (Version 13.0, Systat Software, Inc., San Jose, CA, USA).
3.6.10.3 Non-targeted Microbial Gene Analysis
Variable regions 1, 2 and 3 of the 16S rRNA gene were amplified using the 27F and 534 primers
described by Bradley et al. (2016) and barcoded with dual indices outlined by Kozich et al. (2013). PCR
reactions were carried out in triplicate with the Roche FastStart™ High Fidelity PCR System (Sigma-
Aldrich Corporation, St. Louis, MO, USA). The 50-|iL reactions were comprised of 5 |iL of 10X
Reaction Buffer, 1 |iL of dimethyl sulfoxide (DMSO), 1 |iL of 10-mM deoxyribonucleotide triphosphate
(dNTPs), 2 |iL each of 10-|iM forward and reverse primers, 0.5 |iL of Enzyme Blend, and 1 ng total
DNA. The PCR was operated at 95 °C for 2 min, followed by 25 cycles of 95 °C for 30 sec, 55 °C for 30
sec, and 72 °C for 1 min, and final extension at 72 °C for 10 min. The replicate reactions were pooled,
and amplicons were purified and normalized using the SequalPrep™ Normalization Plate Kit
(ThermoFisher Scientific, Waltham, MA, USA) per the manufacturer's instructions and exercising the
option of using two wells per sample. Samples were then pooled by volume and the concentration of
libraries was assessed using KAPA Library Quantification Kit (Kapa Biosystems, Inc., Wilmington,
MA, USA) and the Agilent High Sensitivity DNA Kit (Agilent Technologies, Inc., Santa Clara, CA,
USA). For amplicon sequencing, the library was diluted to 5.6 picomolar (pM) and mixed with PhiX
Control v3 (Ulumina Inc., San Diego, CA, USA). Sequencing was carried out with the MiSeq system
(Illumina, Inc., San Diego, CA, USA) using the 600-cycle MiSeq Reagent Kit V3 (Ulumina Inc., San
Diego, CA, USA) as prescribed by the manufacturer. Quality controls for PCR reactions were run with
every 30 tire crumb rubber samples and were subsequently sequenced to determine sequencing. Positive
controls were a 10-member microbiome, containing a mixture of equal concentrations of genomic DNA
of Streptococcus pneumoniae, Staphylococcus aureus, Porphyromonas gingivalis, Neisseria
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meningitidis, Listeria monocytogenes, Lactobacillus gasseri, Deinococcus radiodurans, Acinetobacter
baumannii, Bacillus cereus, andRhodobacter sphaeroides (American Type Culture Collection,
Manassas, VA, USA). Negative controls contained a volume of 10-mM Tris-HCl at pH 8.5, the same
solution used to dilute genomic DNA for ddPCR analysis. The sequence reads generated by the MiSeq
system were processed using mothur (Version 1.39.5, Schloss et al., 2009). Quality processing of the
reads included filtering to accept those with a Phred quality score of Q30, and maximum lengths of 544
nucleotides, while excluding those with any ambiguous base calls and more than eight homopolymers.
Chimeric sequences were detected and removed with the VSEARCH algorithm of the USEARCH
software (Edgar, 2010). Reads were classified using the Ribosomal Database Project Classifier and
training set 16, using a minimum bootstrap of 80% (Wang et al., 2007).
3.7 Data Processing and Data Analysis for Select Data
This section describes the data processing and data analysis procedures undertaken for the particle size
fraction data, ICP/MS and XRF tire crumb metals data, SVOC extraction data, and the VOC and SVOC
emissions data. Data analyses performed for scanning electron microscopy results (sections 3.6.4 and
4.5.4), bioaccessibility measurements (sections 3.6.9 and 4.13), and microbial measurements (3.6.10 and
4.14) are described in their respective method and/or results sections.
3.7.1 Data Processing
Following secondary data review by an independent expert, the particle size fraction data, ICP/MS and
XRF tire crumb metals data, SVOC extraction data, and the VOC and SVOC emissions data sets were
submitted to the project's data manager. The data manager uploaded data sets using SAS/STAT® 13.1
(SAS Institute Inc., Cary, NC, USA) and performed a series of organizational, review, cleaning, and
output steps. Following initial intake and organization, the data manger provided data reports to the
analyst and project manager to review for potential data issues or labeling problems and to determine
whether any additional cleaning or organization was required. Following resolution, final draft data files
were created for further data processing operations. The analysts and data manager then consulted with
the project manager to interpret the quality control results for each analysis (shown in Appendix E) and
make decisions on required adjustments (if any) and calculation requirements to bring measurement data
into the correct final result. Analytical data file processing was undertaken for several of the analyses in
this study:
• For ICP/MS metals analysis data files, the digestion and analytical files were combined to
generate final amounts of metals measured per kilogram of tire crumb rubber. Samples had been
dried prior to analysis, so no moisture content adjustment was performed. Results were adjusted
by subtracting the method blank values from the samples measurement results on a batch-
specific basis.
• For SVOC extraction with GC/MS/MS analysis, the measurement results were calculated
amounts of SVOC analyte per kilogram of crumb rubber. Concentrations were adjusted for tire
crumb rubber moisture content and adjusted further by subtracting the average method blank
values from the sample measurement results. Due to apparent differences in response across
batches of sample analyses, batch-specific recovery corrections were performed by multiplying
the measurement result by the average reagent spike result across all batches and dividing that
batch's reagent spike result.
• For LC/TOFMS analysis of SVOCs extracted from tire crumb rubber, the non-quantitative
results were reported as chromatographic area counts. Results were adjusted by subtracting the
average method blank area count values from the sample measurement results.
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• For GC/TOFMS analysis of VOCs in chamber emission samples, the measurement results were
calculated as emission factors by incorporation of chamber ventilation conditions, sampling rates
and times, and amounts of tire crumb rubber placed in the chamber. Concentrations were
adjusted for tire crumb rubber moisture content. Results were further adjusted by subtracting the
average chamber background measurement result for each chamber experiment batch from the
sample measurement result for samples in that chamber experiment batch. Each chamber
experiment batch was conducted at either 25 °C or 60 °C, so the chamber background
adjustments were effectively on a temperature-specific basis.
• For GC/MS/MS analysis of SVOCs chamber emission samples, the measurement results were
calculated as emission factors by incorporation of chamber ventilation conditions, sampling rates
and times, and amounts of tire crumb rubber placed in the chamber. Concentrations were
adjusted for tire crumb rubber moisture content. Results were further adjusted by subtracting the
average chamber background measurement result for each chamber experiment batch from the
sample measurement results for samples in that chamber experiment batch. Each chamber
experiment batch was at either 25 °C or 60 °C, so the chamber background adjustments were
effectively on a temperature-specific basis.
• For HPLC/UV analysis of formaldehyde in chamber emission samples, the measurement results
were calculated as emission factors by incorporation of chamber ventilation conditions, sampling
rates and times, and amounts of tire crumb rubber placed in the chamber. Concentrations were
adjusted for tire crumb rubber moisture content. Results were adjusted by subtracting the average
chamber background measurement across all batches, separately for 25 °C and 60 °C
experiments.
• For LC/TOFMS analysis of SVOCs in chamber emission samples, the non-quantitative results
were reported as chromatographic area counts. Results were adjusted by subtracting the average
chamber background area count result for each chamber experiment batch from the sample
measurement area count for samples in that chamber experiment batch. Each chamber
experiment batch was conducted at either 25 °C or 60 °C, so the chamber background
adjustments were effectively on a temperature-specific basis.
The final processed measurement data were then placed into data analysis files. Separate data analysis
files were prepared for recycling plants, synthetic turf field composite samples, and synthetic turf field
individual location samples. A file was also created with the various types of duplicate measurement and
replicate analysis measurement data. Some chemical measurement results did not meet quality control
requirements and were flagged as "not acceptable". These data were retained in the processed data files,
but not included in the final data analysis files. Finally, other types of information needed for data
analysis were added to the final data analysis files (e.g., recycling plant and synthetic turf field
information, chamber experiment temperatures, chemical names and reporting orders, and analysis
grouping variables).
3.7.2 Data Analysis
Chemical concentration, emission, and particle size measurement values and their summary statistics
were presented in tables generated using SAS/STAT® 13.1 (SAS Institute Inc., Cary, NC, USA; SAS
Institute Inc., 2013a) and in graphics, with data reported at two significant figures. Boxplots, scatterplots
and bar charts were prepared in the R package ggplot2 (Wickham, 2009) scatterplots, while modeled
curves and bar charts were prepared in the SAS/GRAPH® 9.3 procedure SGPLOT (SAS Institute Inc.,
2016).
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For chemical concentration value, emission factor, and particle size tables, tests for equality of group
means were performed in log-scale by 1-way ANOVA models fitted in the SAS MIXED procedure
(SAS/STAT® 13.1). The logarithmic transformations for these tests of group means were based on the
Shapiro-Wilk test for normality, which showed for a majority of the analytes the hypothesis of a normal
distribution was not rejected following log transformation. Results of Shapiro-Wilk testing for
untransformed and transformed data are shown in Appendix G. A conservative approach was taken to
suppress reporting p-values when any chemical-specific or particle size data values represented in a
table was zero or negative, since log-transformation could not be performed, and the result was a less
than complete data set.
Tables for selected (primary) chemicals are given in the report body (Volume 1); full tables (with
primary and secondary analytes) are given in Appendices I through Q (Volume 2). Chemical
concentration and emission factor tables present and summarize results for a combination of sample
sources (e.g., recycling plant and synthetic turf field samples) and, when applicable (e.g. for emission
factors), also present temperature data. Summary statistics tables cover all chemicals and give the
number of samples, percent of samples where the chemical was detected above the quantifiable limit,
mean and standard deviation of the sample values, percent relative standard deviation (i.e., coefficient of
variation), and selected percentiles. Other concentration and emission factor tables are restricted to
chemicals with at least 60 percent detection above the quantifiable limit; these tables compare group
means (e.g., recycling plants versus synthetic turf fields; indoor versus outdoor synthetic fields;
synthetic fields in three installation age categories; and synthetic fields across four census regions).
Additional analyses explore variance components, such as within- and between-field variations
(estimated by random effects models fitted in the SAS MIXED procedure, with group as the random
effect), synthetic turf field composite and individual sample values, recycling plant individual sample
values, and duplicate/replicate data. Other tables present and summarize recycling plant and synthetic
turf field particle size distributions and differences among fields with different characteristics. All
laboratory-reported values were used in data analyses, even when below the quantifiable limit (in-lieu of
using substitution or other censored data approaches). Some results appear as negative values due to
subtraction of blank or background measurements; these negative values were retained in tables, figures,
and calculations and were not arbitrarily set to zero.
Boxplots and scatterplots present chemical-specific exposure factor or concentration sample values and
summary statistics by selected categorical variables, including synthetic turf field and recycling plant
sites, and for synthetic turf fields, installation year groups, indoor/outdoor status, and census regions. An
example boxplot annotated with descriptive statistics and individual sample values is given in Figure 3-
14.
86
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• - individual data value
! - upper whisker length is at most 1.5 * interquartile range
1 and does not extend beyond the maximum data value
1
1
i- mean
!
- 75th percentile
- median
- 25th percentile
- lower whisker length is at most 1.5* interquartile range
and does not extend beyond the minimum data value
Figure 3-14. Example boxplot annotated with descriptive
statistics and sample values.
3.7.3 SVOC Decay Time Half-Live Analysis
Outdoor synthetic turf field composite mean and recycling plant mean extractable SVOC concentrations
were analyzed using generalized linear models with the categorical fixed effect of field/recycling plant
installation year. These composite concentration models were fitted using the SAS GLIMMIX
procedure (SAS Institute Inc., 2013b), where the exponential distribution was specified for the
composite concentrations with (default) log link function. Chemical substance half-life estimates (years
since field installation) were calculated based on model-predicted composite concentrations using
recycling plant model predictions as initial values for the exponential decay constants; recycling plant
year was approximated as mid-2016 (Stewart, 1991). Chemical substance half-life estimates were also
calculated omitting recycling plants using model predictions for fields installed in 2016 as initial values
for the exponential decay constants.
3.7.4 Field Characteristics Modeling Analysis
Fifteen chemical analyte concentrations and/or emission factors for composite infill samples collected
from synthetic turf fields were selected for analysis using a linear model with categorical fixed effects of
age group, indoor vs. outdoor field, and census region. These 15 concentration or emission factor
models were fitted using the SAS MIXED procedure in backward elimination, starting with the full
factorial model and stopping with the final reduced model for each of the chemical substances
considered. Model selection was based on main effect and interaction term p-values using a=0.05, the
Akaike information criterion (AIC) statistic, and model residuals. Model residuals were assessed
graphically in SAS MIXED and tested for normality using the Shapiro-Wilk statistic in the SAS
UNIVARIATE procedure (SAS/STAT® 13.1). Models for log-transformed composite concentrations
were fitted as indicated by the residuals analysis.
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4.0 Tire Crumb Rubber Characterization
Results
4.1 Overview
The tire crumb rubber characterization results are reported in this section for specific research areas and
research activities as summarized in Table 4-1.
Table 4-1. Research Area and Research Activity Results Reported in This Section
Research Area
Research Activities
Recycling Plant and Synthetic
Turf Field Recruitment and
Sampling
Recruiting and collecting samples at multiple tire recycling facilities producing tire
crumb rubber and multiple synthetic turf fields with tire crumb rubber infill across
the United States
Synthetic Turf Field Operations
and Maintenance
Collecting information from synthetic turf field owners/managers to better
understand field operations, types and numbers of field users, field maintenance
practices, and the use of chemical or other product treatments on the fields
Tire Crumb Rubber Chemical,
Physical, and Microbiological
Characterization
Preparing the samples collected from tire recycling plants and synthetic turf fields
for several types of characterizations and analyses
Measuring particle size ranges and other particle characteristics of tire crumb
rubber from tire recycling plants and tire crumb rubber infill from synthetic turf
fields across the United States, with further exploration of particle size and
morphology using scanning electron microscopy
Completing quantitative characterization of the inorganic and organic chemical
substances found in the sampled tire crumb rubber from tire recycling plants and
tire crumb rubber infill from synthetic turf fields
Providing insight on differences between chemical substances associated with
'fresh' tire crumb rubber produced at recycling plants and what is found in tire
crumb rubber infill on synthetic turf fields
Examining emissions of organic chemicals from tire crumb rubber material at two
temperatures for improved understanding of the potential for inhalation exposures
Assessing variability of chemicals associated with tire crumb rubber within and
between recycling plants, as well as within and between fields
Examining the range of chemical concentrations found in tire crumb rubber infill
from fields across the United States and some of the important characteristics
associated with those differences across fields, including indoor vs. outdoor fields,
fields with a wide range of installation dates, and fields in different U.S. regions
Using suspect screening and non-targeted analysis approaches to elucidate the
potentially larger range of chemicals for which additional information may be
needed to better understand exposures and risks
Measuring the bioaccessibility of metals from tire crumb rubber as an important
characteristic for improving understanding of potential exposure
Performing targeted and non-targeted microbial assessments to elucidate
microbiological populations associated with tire crumb rubber infill at synthetic
turf fields and characteristics associated with differences across a range of fields in
the United States
89
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4.2 Recycling Plant and Synthetic Turf Field Recruitment
4.2.1 Recycling Plant Selection and Recruitment
CDC/ATSDR and EPA contacted seven companies operating tire recycling plants that produce tire
crumb rubber for synthetic turf infill. CDC/ATSDR and EPA reached agreements with six companies to
collect samples at nine recycling plants operated by those companies across the United States. Six
recycling plants used the ambient process, and three used the cryogenic process (see Appendix A for
more information on these processes). The nine recycling plants were located across all four U.S. census
regions.
4.2.2 Synthetic Turf Field Selection and Recruitment
Between August and November 2016, CDC/ATSDR researchers contacted a total of 306 community
field owners (Table 4-2). The majority of those owners did not respond to the recruitment attempts,
some owners declined participation for the reasons discussed in section 3.2.2 (i.e., liability,
confidentiality or timing), and some fields were not eligible to participate in the study. The researchers
obtained participation agreements to sample at 21 community fields with synthetic turf. Researchers also
collaborated with the U.S. Army Public Health Center (APHC) to identify synthetic turf fields at
military installations across the U.S. This recruitment effort resulted in the inclusion of 19 additional
U.S. Army fields for sampling, bringing the recruited fields to 40 total (Table 4-2). Characteristics of the
recruited fields are enumerated in Tables 4-3 through 4-5.
Table 4-2. Synthetic Turf Field Recruitment Efforts, by U.S. Census Region
Region
Number of
Community
Fields
Contacted"
Number of
Community
Fields
Ineligible
Number of
Community
Fields
Declined1*
Number of
Community
Fields
Recruited
Number of
U.S. Army
Fields
Recruited
Northeast
118
22
20
4
5
Midwest
96
10
9
8
0
South
40
11
13
5
8
West
52
8
9
4
6
Total
306
51
51
21
19
a Facilities with more than one field were only counted as n=l.
b Facilities that did not return phone calls or other attempts (i.e., email) at recruiting are not included in the number of fields
declining; the majority of community fields contacted failed to respond to recruitment attempts.
Table 4-3. Synthetic Turf Fields Recruited, by Fie
d Type (Outdoor and Indoor) and U.S. Census Region
Region
Number of Outdoor Fields
Number of Indoor Fields
Total Number of Fields
Northeast
5
4
9
Midwest
2
6
8
South
11
2
13
West
7
3
10
Total
25
15
40
90
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Table 4-4. Synthetic Turf Fields Recruited, by Installation Year Group and U
S. Census Region
Region
Number of Fields Installed
2004 - 2008
Number of Fields Installed
2009-2012
Number of Fields Installed
2013-2016
Northeast
3
5
1
Midwest
2
5
1
South
2
5
6
West
4
3
3
Total
11
18
11
Table 4-5. Synthetic Turf Fields Recruited, by Field Type (Outdoor and Indoor) and Installation Year Group
Field Installation
Year
Number of Outdoor Fields
Number of Indoor Fields
Total Number of Fields
2004 - 2008
5
6
11
2009 -2012
10
8
18
2013 -2016
10
1
11
Total
25
15
40
4.3 Synthetic Field Use and Maintenance Questionnaires
The questionnaire responses received from owners and/or managers of the recruited synthetic turf fields
are summarized in this section for several topics, including tire crumb refreshment/replacement, field
maintenance, treatment of fields with chemical products, and field uses and users. Most of the
interviewed facility personnel (87.5%) reported they were managers of the synthetic turf fields (Table 4-
6).
Table 4-6. Relationship
of Questionnaire Interviewee to Facility
Position at Synthetic
Turf Field/Facility
Number of Interviewees
Percent of Interviewees
Manager
35
87.5%
Owner
3
7.5%
Other
2
5.0%
Total
40
100%
Tire crumb maintenance (i.e., replacing or refreshing the tire crumb rubber infill) varied among the
synthetic turf fields. Replacing all the tire crumb rubber was not commonly reported; only one indoor
field (6.7%) and one outdoor field (4.2%) had tire crumb rubber infill completely replaced. Refreshing
or adding tire crumb rubber was more common, with 60% of indoor fields and 48.5% of outdoor fields
having had the tire crumb infill refreshed, but the majority of outdoor fields never had tire crumb rubber
refreshed or replaced (Table 4-7). The frequency in which the tire crumb rubber was refreshed or
replaced at these fields varied from every six months to rarely (Table 4-8).
91
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Table 4-7. Tire Crumb Rubber Maintenance (Refreshment by Partial Addition or Replacement)
at Recruited Synthetic Turf Fields"
Tire Crumb Maintenance
Number of
Indoor Fields
Percent of
Indoor Fields
Nu mber of
Outdoor Fields
Percent of
Outdoor Fields
Refresh Tire Crumb
9
60%
11
45.8%
Replace Tire Crumb
1
6.67%
1
4.2%
Did Not Refresh or Replace Tire Crumb
5
33.3%
12
50.0%
11 Missing responses from one outdoor field; Indoor fields (n=15) and outdoor fields (n=24).
Table 4-8. Frequency of Tire Crumb Rubber Maintenance at Recruited Synthetic Turf Field(s) Having
Experienced Tire Crumb Refresh or Replacement3
Frequency of
Number of Indoor
Number of Indoor
Number of Outdoor
Outdoor Fields
Tire Crumb
Fields with Tire
Fields with Tire
Fields with Tire
with Tire Crumb
Maintenance
Crumb Refreshed
Crumb Replaced
Crumb Refreshed
Replaced
Every 6 months
2
0
2
0
Yearly
1
0
3
0
Every 2-3 years
2
0
0
0
Every 3-5 years
0
0
1
0
Every 5-7 years
1
0
0
0
Never/Rarely
3
1
2
1
Don't know
0
0
2
0
Missing
0
0
1
0
11 Includes only those indoor fields (n= 10) and outdoor fields (n= 12) for which tire crumb rubber replacement or refreshment
was performed.
Field owners or managers were asked whether their fields had ever been treated with biocides,
herbicides, insecticides, fungicides, or other agents. More indoor fields than outdoor fields were reported
to have been treated (50% to 16.7% respectively; Table 4-9); however, one response was missing from
each type of field, indoor and outdoor. No insecticide or herbicide treatments were reported at any field.
Other agents were reported to have been used at two of the indoor fields and two outdoor fields; an
unknown biocide was also reported to have been used at two indoor fields (Table 4-10). Common
chemicals reported to be used in field treatment include PureGreen24 disinfectant fungicide (Pure
Green, LLC, Nashville, TN, USA), Simple Green® (Sunshine Makers, Inc., Huntington Beach, CA),
hydrogen peroxide, Waxie 710 multi-purpose disinfectant cleaner (WAXIE Sanitary Supply, San Diego,
CA, USA), and fabric softener (Table 4-10).
92
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Table 4-9. Synthetic Turf Field Treatment with Cleaners, Biocides, Herbicides, Insecticides,
Fungicides, or Other Agentsa,b
Field Treatment
Number of
Percent of
Number of
Percent of
Indoor Fields
Indoor Fields
Outdoor Fields
Outdoor Fields
Yes
7
50.0%
4
16.7%
No
5
35.7%
19
79.2%
Don't Know
1
7.1%
1
4.2%
Refused
1
7.1%
0
0%
Total
14
100%
24
100%
a Missing responses from one indoor and one outdoor field; indoor field responses (n=14) and outdoor field
responses (n=24); N/A = Not applicable.
b No herbicide or insecticide treatments were reported at any field.
Table 4-10. Products Used to Treat Synthetic Turf Fields and Frequency of Treatment
Field Type
Product Used to Treat Field
Frcqucncy of Treatment
Indoor
PureGreen24 disinfectant fungicide
2 times a month
Indoor
Disinfectant/sterilant made by Pioneer
Yearly
Indoor
Hydrogen peroxide, fabric softener
2 times a year
Indoor
Fabric softener
Not reported
Indoor
Waxie 710 multipurpose disinfectant cleaner
1 time a month
Indoor
Unknown Biocide
2 times a month
Indoor
Unknown Biocide
Not reported
Outdoor
Simple Green® and water
4 times a year
Outdoor
Simple Green® and water
4 times a year
Outdoor
Fabric softener and a disinfectant
Not reported
Outdoor
Fabric softener
Yearly
a Includes only those fields for which treatment with cleaners, biocides,
or other agents was reported.
herbicides, insecticides, fungicides,
The most commonly reported field maintenance activities were brushing and leveling for both indoor
and outdoor fields (Table 4-11). Magnet sweep (32%), aerating fields (28%), and other field
maintenance activities were more commonly performed at outdoor fields than indoor fields; the
frequency at which this field maintenance was conducted is shown in Table 4-12. For field maintenance
procedures, a common response included in the other category was sanitization with ultraviolet (UV)
light.
Table 4-11. Synthetic Turf Field Maintenance Activities3
Maintenance Activity
Number of
Indoor Fields
Percent of
Indoor Fields
Nu mber of
Outdoor Fields
Percent of
Outdoor Fields
Brushing
9
60%
14
56%
Leveling
6
40%
13
52%
Deep Cleaning
5
33.3%
5
20%
Magnet Sweep
4
27%
8
32%
Aerating
2
13%
7
28%
Other
2
13%
5
20%
a Indoor fields (n=15); Outdoor fields (n=25).
93
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Table 4-12. Frequency of Synthetic Turf Field Maintenance Activities3
Field Maintenance
Nu mber of Fields
Performing
Maintenance
Weekly or Less
Number of Fields
Performing
Maintenance
Monthly
Number of Fields
Performing
Maintenance
Yearly
Number of Fields
Missing Response
Regarding
Frequency
Indoor Fields - Brushing
1
3
4
1
Outdoor Fields - Brushing
3
6
4
1
Indoor Fields - Leveling
1
1
3
1
Outdoor Fields - Leveling
4
5
4
0
Indoor Fields - Deep Cleaning
0
2
3
0
Outdoor Fields - Deep Cleaning
0
1
4
0
Indoor Fields - Magnet Sweep
0
2
2
0
Outdoor Fields - Magnet Sweep
0
6
2
0
Indoor Fields - Aerating
0
0
2
0
Outdoor Fields - Aerating
0
4
3
0
Indoor Fields - Other
0
1
1
0
Outdoor Fields - Other
0
4
1
0
Over half of the synthetic turf fields were reported as not open to the public (52.5%), with a majority of
use limited to organizational or membership use (67.5%; Tables 4-13 and 4-14). Additionally, only
32.5%) of both indoor and outdoor fields were reported to offer open or free-play (Table 4-15), with
outdoor fields more likely to have open or free-play (48%>) than indoor fields (6.'
Table 4-13. Synthetic Turf Fields Open to the
Jublic
Field Open to Public
Number of Fields
Percent of Fields
Yes
17
42.5%
No
21
52.5%
Refused
2
5.0%
Total
40
100%
Table 4-14. Synthetic Turf Field Use Limited to Organization or
Field Use Limited to
Organization/Membership
Nu mber of Fields
Percent of Fields
Yes
27
67.5%
No
11
27.5%
Refused
2
5.0%
Total
40
100%
Membership
Table 4-15. Open or
Free-Play at the Facility
Open or Frec-Plav
Offered
Number of
Indoor Fields
Percent of
Indoor Fields
Number of
Outdoor Fields
Percent of
Outdoor Fields
Total Number
of Fields
Percent of
Total Fields
Yes
1
6.7%
12
48.0%
13
32.5%
No
13
86.7%
12
48.0%
25
62.5%
Refused
1
6.7%
1
4.0%
2
5.0%
Total
15
100%
25
100%
40
100%
94
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The synthetic turf fields were most commonly reported to be open an average 7 days per week for all
seasons (Table 4-16). The average number of hours per day the fields were used per season varied
(Table 4-17). These two survey questions were not answered for all fields.
Table 4-16. Days per Week Synthetic Turf Fields Open During Each Season
Days per Week
Field Open
Number of Fields
in Fall
Nu mber of Fields
in Winter
Number of Fields
in Spring
Number of Fields
in Summer
0
0
2
0
1
3
1
1
2
3
5
4
4
5
5
6
3
1
2
2
7
30
29
29
27
Total
38
37
38
38
Table 4-17. Average Hours per Day Synthetic Turf Fields Used per Season
Hours per Day
Field Used
Number of Fields
in Fall
Nu mber of Fields
in Winter
Number of Fields
in Spring
Number of Fields
in Summer
0
0
3
0
1
2
0
1
0
0
3
2
0
2
4
4
1
1
2
2
5
5
3
5
3
6
1
2
3
4
7
3
2
1
1
8
7
6
6
3
9
1
1
1
0
10
3
4
3
3
11
1
1
1
3
12
3
5
1
1
14
6
4
8
7
15
2
2
2
2
16
0
0
0
1
20
1
0
1
1
Total
36
35
36
36
The highest average number of daily field users for indoor fields occurs in winter, while spring and
summer have the highest averages for outdoor fields sampled (Table 4-18). The maximum number of
daily users for indoors fields was 300 field users less than the outdoor fields - 900 and 1200 people,
respectively. For almost all seasons, the most commonly reported frequency of people per day was the
under 200 people category for both the indoor and outdoor fields (Table 4-19).
95
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Table 4-18. Number of People per Day Using Synthetic Turf
Statistic
Indoor
Fields -
Fall
Indoor
Fields -
Spring
Indoor
Fields -
Summer
Indoor
Fields -
Winter
Outdoor
Fields -
Fall
Outdoor
Fields -
Spring
Outdoor
Fields -
Summer
Outdoor
Fields -
Winter
Average
223
191
149
284
303
305
305
252
Minimum
25
25
0
0
20
27.5
27.5
0
Median
135
120
110
200
175
200
200
160
Maximum
700
900
500
900
1200
1200
1200
1000
ields per Season
Table 4-19. Frequencies of Average Number of People per Day Using Synthetic Turf Fields per Season
Dailv Field
Indoor
Indoor
Indoor
Indoor
Outdoor
Outdoor
Outdoor
Outdoor
Users
Fields -
Fields -
Fields -
Fields -
Fields -
Fields -
Fields -
Fields -
Fall
Spring
Su mmcr
Winter
Fall
Spring
Summer
Winter
<200
8
10
9
5
11
10
10
11
200 - 399
2
1
2
5
5
6
6
5
400 - 599
0
0
1
0
2
2
2
2
600 - 799
2
0
0
1
0
0
1
1
800 - 999
0
1
0
1
1
1
0
0
1000+
0
0
0
0
2
2
2
2
The most commonly reported types of sports or other activities played on synthetic turf fields include
soccer (80%), physical training (67.5%), and football (55%). Other sports reported but not listed on the
questionnaire include lacrosse, track and field, and flag football (Table 4-20). Furthermore, a large
majority (85%) of the fields did not state they had standard practices in place to reduce tire crumb
exposure (Table 4-21).
Table 4-20. Types of Sports Played on Synt
letic Turf Fields
Sport
F requcncy
Percentage
Soccer
32
80%
Physical Training
27
67.5%
Football
22
55%
Softball
14
35%
Ultimate Frisbee
12
30%
Baseball
11
27.5%
Rugby
11
27.5%
Other1
20
50%
a Facilities reported other types of sports frequently played on the fields that were not already listed in the questionnaire.
Table 4-21. Standard Practices in Place to Reduce Tire Crumb Exposure to
People Using the Synthetic Fields
Practices in Place to Reduce
Tire Crumb Exposure
Nu mber of Fields
Percent of Fields
Yes
6
15%
No
34
85%
Total
40
100%
96
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4.4 Tire Crumb Rubber Sample Collection and Sub-Sample Preparation
4.4.1 Recycling Plant Sample Collection
Researchers collected recycled tire crumb rubber samples from nine tire recycling plants around the
United States. These plants produced tire crumb rubber of the size category used as infill for synthetic
turf fields (typically 10 to 20 mesh). Three of the plants used a cryogenic process for creating tire crumb
rubber, whereas the remaining six plants used an ambient process. Researchers generated a total of 27
samples for organic chemical analysis (including extraction, emissions testing, and bioaccessibility
analysis), 27 samples for metals analysis (including digestion, spectroscopy, and bioaccessibility
analysis), and 27 samples for particle characterization.
4.4.2 Synthetic Turf Field Sample Collection
Researchers collected tire crumb rubber infill samples from 40 synthetic turf fields to support
characterization of chemical constituents, particle characterization, and examination of microbial
species. Following training by EPA and CDC/ATSDR researchers, APHC personnel collected the
samples at the 19 synthetic turf fields located at Army installations across the United States -16 outdoor
fields and 3 indoor fields. Trained CDC/ATSDR and EPA staff collected samples at the 21 community
fields. The total numbers of fields included in sample collection are shown in Table 4-22.
Researchers collected tire crumb rubber infill from the top 3 centimeters (cm) of the synthetic turf field
surface for chemical and particle characterization and microbial analysis. Chemical characterization
included analysis of SVOC and metal analytes, metals bioaccessibility analysis, and emissions testing of
VOCs and SVOCs; and particle characterization included analysis of moisture content, sand content,
particle size, and SEM for a subset of samples. Microbial analysis included isolation and quantification
of microbial genes.
Information about the numbers of samples collected from synthetic turf fields in the four U.S. census
regions for each type of analysis is shown in Table 4-22. Between 8 and 13 fields in each census region
were sampled. Sampling took place at 25 outdoor fields and 15 indoor fields - one field was a
baseball/softball field, three were Army physical training fields, and the remainder were soccer/football-
type playing fields (Table 4-23). Field installation dates ranged from 2004 to 2016 (Table 4-23). The
characteristics for each individual synthetic turf field where tire crumb rubber infill samples were
collected are described in Table 4-23. This table provides a reference for figures and tables later in this
section that show results for individual fields.
97
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Table 4-22. Samples Collected for Analyses at Synthetic Turf Fields3
Region
Number
of Fields
Number of
Individual
Location Samples
for Organ ics
Analysis
Number of
Individual
Location
Samples for
Metals Analysis
Number of
Individual
Location Samples
for Particle
Characterization
Number of
Individual
Location Samples
for Microbial
Analysis
Total
Composite
Samples
Prcparcdb
Northeast
9
63
63
63
63
27
Midwest
8
56
56
56
56
24
South
13
91
91
91
91
39
West
10
70
70
\o
o
70
30
Total
40
280
280
279
280
120
11 At each of the 40 fields, samples were collected from seven individual locations.
b For each synthetic turf field, one composite sample was prepared in the laboratory from the seven individual location
samples for organic chemical analyses, one composite sample was prepared for metals analyses, and one composite sample
was prepared for particle size fraction analysis.
0 The cap came off one sample collection container during transport, resulting in an unusable sample.
Table 4-23. Individual Field Characteristics
Field ID
Outdoor or Indoor Field
Installation Age Category
U.S. Census Region Location
1
Outdoor
2009-2012
South
2
Outdoor
2013 -2016
South
3
Outdoor
2004 - 2008
Northeast
4
Indoor
2009-2012
Northeast
5
Outdoor
2013 -2016
Northeast
6
Indoor
2009-2012
Northeast
7
Indoor
2009-2012
Northeast
8
Outdoor
2013 -2016
West
9
Outdoor
2004 - 2008
West
10
Outdoor
2009-2012
West
11
Outdoor
2013 -2016
South
12
Outdoor
2009-2012
South
13
Outdoor
2009-2012
West
14
Outdoor
2013 -2016
West
15
Outdoor
2013 -2016
South
16
Outdoor
2013 -2016
South
17
Outdoor
2009-2012
South
18
Outdoor
2013 -2016
South
19
Outdoor
2009-2012
West
20
Indoor
2004 - 2008
South
21
Outdoor
2013 -2016
South
22
Indoor
2009-2012
South
23
Outdoor
2004 - 2008
West
24
Indoor
2009-2012
Midwest
25
Indoor
2009-2012
Midwest
98
-------
Table 4-23 Continued
Field ID
Outdoor or Indoor Field
Installation Age Category
U.S. Census Region Location
26
Outdoor
2013 -2016
Midwest
27
Indoor
2013 -2016
West
28
Indoor
2009-2012
Midwest
29
Indoor
2009-2012
Midwest
30
Indoor
2004 - 2008
Midwest
31
Outdoor
2009-2012
Northeast
32
Outdoor
2004 - 2008
Northeast
33
Indoor
2004 - 2008
Northeast
34
Outdoor
2009-2012
Northeast
35
Outdoor
2009-2012
Midwest
36
Indoor
2004 - 2008
Midwest
37
Indoor
2004 - 2008
West
38
Indoor
2004 - 2008
West
39
Outdoor
2004 - 2008
South
40
Outdoor
2009-2012
South
4.4.3 Preparation and Scheduled Analysis for Tire Crumb Rubber Samples and Sub-
Samples
Table 4-24 shows the total number of samples and subsamples prepared for the range of analyses to be
applied. This table includes the totals from both tire recycling plants and synthetic turf fields but does
not include quality control samples and analyses. The numbers and types of sample analyses scheduled
for tire crumb rubber characterization analysis are further described in Table 4-25. Tire crumb rubber
material was analyzed by laboratories for a wide range of volatile and semi-volatile organic (VOC and
SVOC) and metals constituents. Quantitative analyses were performed for some target analyte chemicals
(Tables 3-1 through 3-4). Metals analyses were performed using both ICP/MS and XRF, and SVOC
analyses were performed using both GC/MS/MS and LC/TOFMS methods to capture a wide potential
range of chemicals with differing chemical and physical properties. Suspect screening analyses for
additional SVOCs was performed by LC/TOFMS, and non-targeted analysis methods were applied to a
subset of VOC and SVOC samples.
Table 4-24. Number of Recycling Plant and Synthetic Turf Field Tire Crumb Rubber Samples Prepared for
Analysesa'b'c
Analyses
Sample Type
Number of
Composite
Samples
Number of
Individual
Samples
Total
Number of
Samples
Particle Characterization
Particle size characteristics
40
27
67
Particle Characterization
SEM and EPMA analysis
9
9
18
Particle Characterization
Moisture content
40
9
49
Particle Characterization
Sand/Rubber fraction analysis
40
0
40
Direct Chemical Constituent
Metals constituent ICP/MS analyses
40
60
100
Direct Chemical Constituent
Metals constituent XRF analyses
40
60
100
Direct Chemical Constituent
Targeted SVOC constituent GC/MS/MS analyses1'
40
62
102
Direct Chemical Constituent
Targeted SVOC constituent LC/TOFMS analyses1'
40
62
102
99
-------
Table 4-24 Continued
Analyses
Sample Type
Number of
Composite
Samples
Number of
Individual
Samples
Total
Number of
Samples
Dynamic Chamber Emissions
Experiments
Chamber experiments for VOCs at 25 °C
40
42
82
Dynamic Chamber Emissions
Experiments
Chamber experiments for VOCs at 60 °C
40
42
82
Dynamic Chamber Emissions
Experiments
Chamber experiments for SVOCs at 25 °C
40
42
82
Dynamic Chamber Emissions
Experiments
Chamber experiments for SVOCs at 60 °C
40
42
82
Emissions Sample
Targeted VOC emissions GC/TOFMS analyses'1
80
84
164
Emissions Sample
Formaldehyde emissions analyses
80
84
164
Emissions Sample
Targeted SVOC emissions LC/TOFMS an ii\ ses1'
80
84
164
Emissions Sample
Targeted SVOC emissions GC/MS/MS an il\ ses1'
80
84
164
Bioaccessibility
Metals bioaccessibility - simulated saliva
40
42
82
Bioaccessibility
Metals bioaccessibility - simulated gastric fluid
40
42
82
Bioaccessibility
Metals bioaccessibility - simulated sweat
40
42
82
Microbial
Microbial analyses - targeted
0
280
280
Microbial
Microbial analyses - non-targeted
0
280
280
aDoes not include quality control/quality assurance samples or analyses; does not include chamber background samples.
b The total numbers of samples are based on 40 synthetic turf field composite samples, 15 to 35 synthetic turf field individual
location samples, and 27 individual recycling plant samples from 9 recycling plants; except for microbial analysis where all
280 individual synthetic turf field location samples are scheduled for analysis.
0 EPMA = Electron probe microanalysis; GC/MS/MS = Gas chromatography/tandem mass spectrometry; GC/TOFMS = Gas
chromatography/time-of-flight mass spectrometry; ICP/MS = Inductively coupled plasma/mass spectrometry; LC/TOFMS =
Liquid chromatography/time-of-flight mass spectrometry; PCR = Polymerase chain reaction; SEM = Scanning electron
microscopy; SVOC = Semivolatile organic compound; VOC = volatile organic compound; XRF = X-ray fluorescence
d In addition to analysis for target analytes, 16 of the samples will be selected for non-targeted analysis.
Table 4-25. Scheduled Numbers of Sample Analyses for Tire Crumb Rubber Characterization3
Analyses
Sample Type
Number of
Analyses'*
Additional Information
Particle Characterization
Moisture analysis
49
Field composite and plant samples
Particle Characterization
Sand fraction analysis
40
Field composite samples
Particle Characterization
Particle size analysis
469
7 size fractions for 67 samples
Particle Characterization
SEM and EPMA analysis
18
9 plant and 9 field composite samples
Direct Constituent
Metals TCP/MS analyses
102°
N/A
Direct Constituent
Metals XRF analyses
102°
N/A
Direct Constituent
Targeted SVOC GC/MS/MS analyses
102°
N/A
Direct Constituent
Non-targeted SVOC GC/MS analyses
16
Subset of plant and field samples
Direct Constituent
Target and suspect screening SVOC
LC/TOFMS analyses
204
Both positive and negative modes
Direct Constituent
Non-targeted SVOC LC/TOFMS
analyses
32
Subset of plant and field samples
100
-------
Table 4-25 Continued
Analyses
Sample Type
Number of
Analysesb
Additional Information
Dynamic Chamber
Emissions Experiments
Chamber experiments for VOCse
328
82d experiments at 25 °C and 60 °C
Dynamic Chamber
Emissions Experiments
Chamber experiments for SVOCse
328
82d experiments at 25 °C and 60 °C
Dynamic Chamber
Emissions Experiments
Chamber time series experiments for
VOCsf
8
4 experiments at 25 °C and 60 °C
Dynamic Chamber
Emissions Experiments
Chamber time series experiments for
SVOCsf
8
4 experiments at 25 °C and 60 °C
Dynamic Chamber
Emissions Experiments
Wristband experiments for SVOCs8
4
25 °C only
Emissions
Samples for formaldehyde analyses
328
N/A
Emissions
Samples for targeted VOC GC/TOFMS
analyses
376
N/A
Emissions
Samples for non-targeted VOC
GC/TOFMS analyses
16
Subset of plant and field samples
Emissions
Samples for targeted SVOC GC/MS/MS
analyses
376
N/A
Emissions
Wristband samples for SVOC
GC/MS/MS analyses
24
N/A
Emissions
Samples for non-targeted SVOC GC/MS
analyses
16
Subset of plant and field samples
Emissions
Samples for SVOC LC/TOFMS analyses
376h
Both positive and negative modes
Emissions
Samples for non-targeted SVOC
LC/TOFMS analyses
32
Subset of plant and field samples
Bioacccssibilily
Metals bioacccssibilily ICP/MS analyses
246
82d samples; 3 simulated fluids
Microbial
Microbial targeted analyses
280
N/A
Microbial
Microbial non-targeted analyses
280
N/A
a EPMA = Electron probe microanalysis; GC/MS = Gas chromatography/mass spectrometry; GC/MS/MS = Gas
chromatography/tandem mass spectrometry; GC/TOFMS = Gas chromatography/time-of-flight mass spectrometry; ICP/MS =
Inductively coupled plasma/mass spectrometry; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry; N/A =
Not applicable; PCR = Polymerase chain reaction; SEM = Scanning electron microscopy; SVOC = Semivolatile organic
compound; VOC = Volatile organic compound; XRF = X-ray fluorescence
b Does not include quality control/quality assurance samples or analyses.
0 The total of 102 samples is based on 40 synthetic field composite samples, 35 synthetic field individual samples, and 27
individual recycling plant samples.
dThe total of 82 samples is based on 40 synthetic field composite samples, 15 synthetic field individual samples, and 27
individual recycling plant samples.
e Each emission experiment included a chamber background sample followed by a tire crumb emission sample.
f Each time series experiment generated 6 samples.
g Each wristband experiment generated 6 samples.
h Only a subset of the SVOC emission samples were analyzed by LC/TOFMS.
101
-------
4.5 Tire Crumb Rubber Particle Characterization Results
4.5.1 Tire Crumb Rubber Moisture
Moisture content was measured in tire crumb rubber collected at nine recycling plants and in tire crumb
rubber infill collected at 40 synthetic turf fields (Table 4-26). Moisture measurements were made in one
of the three samples collected at recycling plants for metals analysis, and in the metals composite sample
prepared for each synthetic turf field. All moisture measurements were made in duplicate. Average
percent moisture results are shown in Figures 4-1 and 4-2.
Moisture content in all recycling plant tire crumb rubber samples was < 1%, with a median value of
0.87%. Moisture content in tire crumb rubber infill collected at synthetic turf fields ranged from 0.4% to
6.2%, with a median value of 0.81%. Samples collected from several synthetic turf fields had visible
moisture, which was reflected in the measurements, as six fields had > 3% moisture content. The visible
moisture may have been a result of slight precipitation or heavy dew present at the time of sample
collection.
In order to provide more comparable results, when measurements were based on a weighed amount of
tire crumb rubber used for analysis, many of the chemical analysis results were adjusted for moisture
content prior to data analysis. The adjustment was not performed for metals ICP/MS or XRF analyses
because these samples were dried prior to analysis.
Table 4-26. Moisture Content in Tire Crumb Rubber from Recycling Plants and Infill from Synthetic
Turf Fields
Tire Crumb Rubber
Sampling Location
N
Mean
% Moisture
Standard
Deviation (%)
Median
% Moisture
Minimum
% Moisture
Maximum
% Moisture
Recycling Plants
9
0.81
0.17
0.87
0.52
0.99
Synthetic Turf Fields
40
1.39
1.38
0.81
0.40
6.22
O)
=5
UO
O
<
3.36
0.88
0.6i
ll
4.96
4.23
0.S2 o.76
0.67 0-73 0.48 |
rn m 11
1.67
1.06
"1.11
1.06
10.551
1.7S
1.261
0.79
0.63.
ll
0.53
I
6.22
4.21
137
x 0.84 1.16
0.7367| a79 °-69l
0.4
1.95
0.84
0.61
0.76 i
|0.59i0.52
III
3.47
SyntheticTurf Field ID
Figure 4-1. Average % moisture in tire crumb rubber infill from synthetic turf fields, by field ID.
102
-------
1.2
1 0.94
0.8
0.6
!«_
=5
4-J
'o
£
v
03
ra
<
0.2
0.87
0.87
0.9
0.94
0.99
0.59
0.67
0.52
A B C D E F G
Recycling Plant ID
H I
Figure 4-2. Average % moisture in tire crumb rubber from recycling plants, by plant ID.
4.5.2 Infill Sand/Rubber Fractions
Sand is sometimes added as an infill component in a mixture with tire crumb rubber and in other cases,
it is used as a base layer prior to tire crumb rubber deposition. There may also be some cases where
windblown or tracked-in sand is present on fields. Synthetic turf field tire crumb rubber infill collected
from the upper 3 cm of the infill at 40 fields was analyzed for sand content and results are shown in
Table 4-27 and Figure 4-3. There were 24 fields with no measured sand content and 16 fields with sand
content in the collected infill ranging from 0.33% to 53.3%. Of those with sand content, six fields had
sand content values of < 10%, while ten fields had sand content values between 10% and 39%. No sand
was observed in tire crumb rubber samples collected at tire recycling plants, so analyses were not
performed, and the material was assumed to be 100% tire crumb rubber. Examples of infill material with
and without sand are shown in Figure 4-4.
Most of the chemical characterization analyses were performed using weighed portions of synthetic turf
field tire crumb rubber infill. Results from these analyses can be considered in two ways - a) as the
amount of chemical per the amount of synthetic turf infill, or b) the amount of chemical per the amount
of tire crumb rubber in the infill. It may be of interest to consider both of these metrics, the first as
perhaps being most relevant for exposure assessment, and the second perhaps being most relevant for
more direct comparisons of tire crumb rubber constituents. Where applicable, measurement results were
calculated both with and without adjustment for % sand content, allowing for both data assessments to
be performed. Except where otherwise noted, results in this report are shown using measurement results
that have not been adjusted for % sand content. An assessment of the potential differences in chemical
measurement results resulting from correcting and not correcting for sand content is presented in section
4.6.3.
103
-------
Table 4-27. Sand Fraction in Tire Crumb Rubber Infill Collected at Synthetic Turf Fields
Sand Fraction Measure
Synthetic Turf Fields Value"
Mean % Sand
7.7
Standard Deviation (%)
13.1
Minimum % Sand
0
Median % Sand
0
Maximum %Sand
53.3
Number of Fields 0% Sand
24
Number of Fields 1 - 9% Sand
6
Number of Fields 10 - 19% Sand
3
Number of Fields 20 - 29% Sand
3
Number of Fields 30 - 39% Sand
3
Number of Fields 40 - 49% Sand
0
Number of Fields 50 - 59% Sand
1
Number of Fields > 59% Sand
0
a Synthetic Turf Fields (n = 40)
60
53.3
50
40
T3
C
ro
on
a 30
M
ra
<
20
10
32
.9 33
?S,5
-1 31
.4
1C 3
23
.1
18.7
L5
.a
7.5
7.2
9.4
13
.3
¦ 3.6
1 1
3.2
0.33
11 - i III
1
III
i 1
J
inuif— ODCTiO'-ffN(riq-Lnixir-.cocrio-HfNfn'^rmi£)f^coiTiO
SyntheticTurf Field ID
Figure 4-3. Percent sand in tire crumb rubber infill, by synthetic turf field ID. If % sand value is not
shown there was no sand in the infill from that field.
104
-------
Figure 4-4. Example synthetic turf field infill material without sand (Field 14) and with sand
(Field 32). Scale gradations are 1 mm.
4.5.3 Particle Size Distributions for Recycling Plants and Fields
Particle size analysis was performed for three tire crumb rubber samples collected from each of nine tire
recycling plants and from composite tire crumb rubber infill samples collected at each of the 40
synthetic turf fields. A sieving and gravimetric method was used to generate seven particle size
fractions, ranging from < 0.063 to > 4.75 mm. A summary of size fraction results for recycling plants
and synthetic turf fields is reported in Table 4-28.
Table 4-28. Particle Size Fraction Summary Statistics for Tire Crumb Rubber Collected at Tire Recycling Plants
and Tire Crumb Rubber Infill Collected at Synthetic Turf Fields11,1'
Particle Size
Fraction
(mm)
Recycling
Plants
Mean
(g/kg)
Recycling
Plants
Standard
Deviation
(g/kg)
Recycling
Plants
Minimum
(g/kg)
Recycling
Plants
Median
(g/kg)
Recycling
Plants
Maximum
(g/kg)
Synthetic
Turf
Fields
Mean
(g/kg)
Synthetic
Turf
Fields
Standard
Deviation
(g/kg)
Synthetic
Turf
Fields
Minimum
(g/kg)
Synthetic
Turf
Fields
Median
(g/kg)
Synthetic
Turf
Fields
Maximum
(g/kg)
>4.75
0.089
0.37
0
0
1.9
0.18
0.53
0
0
2.8
>2-4.75
86
70
0.1
80
270
250
290
0.4
75
930
>1-2
780
120
380
810
930
580
240
73
550
990
>0.25 - 1
140
130
0.5
110
620
170
200
0.5
61
640
>0.125-0.25
1.2
1.6
0
0.6
5.9
0.75
1.3
0
0.3
5.7
>0.063 -0.125
0.35
0.42
0
0.1
1.3
0.47
1.1
0
0.1
5
< 0.063
0.037
0.069
0
0
0.2
0.63
2.1
0
0.1
13
a Results are reported in grams of rabber in a size fraction per kilogram of total robber collected. This is effectively a proportion
of the amount of robber falling within each size fraction.
b Recycling plants (n 27): Synthetic turf fields (n=40)
Results for each recycling plant and each field are reported in Appendix H. For recycling plant tire
crumb rubber samples, on average, a majority of the tire crumb was found in the > 1- to 2-mm fraction
(780 g/kg), with smaller amounts in the > 2- to 4.75-mm (86 g/kg) and the > 0.25- to 1-mm (140 g/kg)
size fractions. On average, 0.35 g/kg was measured in the > 0.063- to 0.125-mm fraction and 0.037 g/kg
in the < 0.063-mm fraction. Size distribution measurements may have been impacted to some extent by
collecting samples only from the top of 1-ton storage bags at eight of nine recycling plants.
105
-------
For synthetic turf field tire crumb rubber infill samples, on average, a majority of the tire crumb was
found in the > 1- to 2-mm fraction (580 g/kg), with smaller amounts in the > 2- to 4.75-mm (250 g/kg)
and the > 0.25- to 1-mm (170 g/kg) size fractions. On average, 0.47 g/kg was measured in the > 0.063-
to 0.125-mm fraction and 0.63 g/kg in the < 0.063-mm fraction. Sixty-five percent of the fields had <
0.1 g/kg in the < 0.063-mm fraction, while the maximum amount measured in that size fraction was 13
g/kg.
The distribution of particle size fraction proportions is shown in Figure 4-5 for recycling plants and
Figure 4-6 for synthetic turf fields. Examples of tire crumb rubber infill collected at synthetic turf fields
with different size ranges are shown in Figures 4-7 and 4-8. Photos of tire crumb rubber collected from
each recycling plant and each field are shown in Appendix FT.
Particle Size Replicate Distributions
1000
Q
l -
¦4—'
H -|
i_
03
G -|
Q_
F-l
O)
F-l
r
o
>>
o
B -
a>
OC
A "|
250 500 750 1000
9 i-I
£ H-
J5 G -
a. f-[
05 E -¦
E D-i
>. C-
o B -
A I
or A -I
0 250 500 750 1000
Proportions [g/kg]
£0.063 mm >0.125 - 0.25 mm >1-2 mm >4.75 mm
>0.063-0.125 mm >0.25 - 1 mm >2-4.75 mm
Figure 4-5. Tire crumb rubber particle size distributions for nine recycling plants
(three samples from each plant).
106
-------
Particle Size Distributions
40-
39-
38-
37-
36-
35-
34-
33-
32-
31 -
30-
29-
28-
27-
26-
25-
24-
23-
Q 22-
T3 21 "
0 20-
u- 19-
18-
17-
16-
15-
14-
13-
12-
11 -
10-
9-
8-
7-
6-
5-
4-
3-
2-
1 -
£0.063 mm
>0.063 - 0.125 mm
>0.125-0.25 mm
>0.25- 1 mm
>1-2 mm
>2-4.75 mm
>4.75 mm
250
500
Proportions [g/kg]
750
1000
Figure 4-6. Tire crumb rubber infill particle size distributions for 40 synthetic turf fields.
Figure 4-7. Example photos of tire crumb rubber infill collected from five
synthetic turf fields. Scale gradations are 1 mm.
-------
J HIIJ till. 11- I'M MMMMaaMMMMMI *:***
Figure 4-8. Example close-up photos of tire crumb rubber infill collected at six synthetic turf fields. Scale
gradations are 1 mm.
There was substantial variability across the amounts measured in the > 0.25- to 1-mm, > 1- to 2-mm,
and > 2- to 4.75-mm size fractions for infill collected at synthetic turf fields. Particle size fractions were
further examined for differences among the three primary field characteristic categories, including
indoor vs. outdoor, installation age groups, and the four geographic regions. Results for these
comparisons are shown in Tables 4-29, 4-30, and 4-31. The only statistically significant result was for
differences among the four geographic regions, where a smaller average proportion in the >2 - 4.75 mm
size fraction was found in samples from Northeast fields and higher mean fractions in Midwest fields.
There were some other non-significant differences, including lower proportions of >1 - 2 mm and
greater proportions of >0.25 - 1 mm size fractions for fields in the oldest installation age group
compared the two newer installation age groups.
Table 4-29. Comparison of Particle Size Fractions for Tire Crumb Rubber Infill at Outdoor and Indoor
Synthetic Turf Fields a'b
Particle Size
Fractions
(mm)
Outdoor Fields
Mean (g/kg)
Outdoor Fields
Standard Deviation
(g/kg)
Indoor Fields
Mean (g/kg)
Indoor Fields
Standard
Deviation (g/kg)
F-test
p-valuec
>4.75
0.28
0.65
0.02
0.077
NR
>2-4.75
230
290
290
310
0.3152
>1-2
570
240
590
260
0.7769
>0.25-1
200
220
110
150
0.6600
>0.125-0.25
0.72
1.1
0.80
1.5
NR
>0.063 -0.125
0.44
1.0
0.52
1.2
NR
<0.063
0.78
2.6
0.38
0.98
NR
a Results are reported in grams of rubber in a size fraction per kilogram of total rubber collected. This is effectively a
proportion of the amount of rabber falling within each size fraction.
b Outdoor fields (n=25); Indoor fields (n=15)
0 NR = Not Reported; one or more measurement results were 0, precluding natural log-transformed testing for the complete
data set.
108
-------
Table 4-30. Comparison of Particle Size Fractions for Tire Crumb Rubber Infill at Synthetic Turf Fields
in Three Field Installation Age Groupsa'b
Particle Size
Fractions
(mm)
Fields
Installed
2004 - 2008
Mean
(g/kg)
Fields
Installed
2004 - 2008
Standard
Deviation
(g/kg)
Fields
Installed
2009-2012
Mean
(g/kg)
Fields
Installed
2009-2012
Standard
Deviation
(g/kg)
Fields
Installed
2013-2016
Mean
(g/kg)
Fields
Installed
2013-2016
Standard
Deviation
(g/kg)
F-test
p-valuc'
>4.75
0.027
0.090
0.14
0.40
0.39
0.86
NR
>2-4.75
220
280
310
340
170
220
0.4893
>1-2
490
190
570
280
690
200
0.1811
>0.25-1
280
280
110
140
130
170
0.2592
>0.125-0.25
1.2
1.6
0.56
0.88
0.65
1.4
NR
>0.063 -0.125
0.62
1.4
0.49
1.2
0.29
0.49
NR
<0.063
0.45
1.1
0.87
3.0
0.43
0.97
NR
a Results are reported in grams of rubber in a size fraction per kilogram of total rubber collected. This is effectively a
proportion of the amount of rubber falling within each size fraction.
b Fields installed between 2004 and 2008 (n=ll); between 2009 and 2012 (n=18); and between 2013 and 2016 (n=ll).
0 NR = Not Reported; one or more measurement results were 0, precluding natural log-transformed testing for the complete
data set.
Table 4-31. Comparison of Particle Size Fractions for Tire Crumb Rubber Infill at Synthetic Turf Fields in Four
Geographic Regionsa'b
Particle Size
Fractions
(mm)
Northeast
Mean
(g/kg)
Northeast
Standard
Deviation
(g/kg)
South
Mean
(g/kg)
South
Standard
Deviation
(g/kg)
Midwest
Mean
(g/kg)
Midwest
Standard
Deviation
(g/kg)
West
Mean
(g/kg)
West
Standard
Deviation
(g/kg)
F-tcst
p-valuc'
>4.75
0
0
0.22
0.78
0
0
0.44
0.52
NR
>2-4.75
100
150
280
320
390
270
220
340
0.0168
>1-2
650
220
630
290
520
220
500
230
0.6418
>0.25-1
250
240
78
100
83
140
270
250
0.1452
>0.125-0.25
0.56
0.68
1.3
2.0
0.33
0.42
0.59
0.70
NR
>0.063 -0.125
0.26
0.28
0.96
1.8
0.15
0.15
0.28
0.47
NR
<0.063
0.17
0.14
1.6
3.6
0.088
0.11
0.22
0.39
NR
a Results are reported in grams of rubber in a size fraction per kilogram of total rubber collected. This is effectively a
proportion of the amount of rubber falling within each size fraction.
bNortheast (n=9); South (n=13); Midwest (n=8); West (n=10)
0 NR = Not Reported; one or more measurement results were 0, precluding natural log-transformed testing for the complete
data set.
109
-------
4.5.4 Scanning Electron Microscopy
4.5.4.1 Scanning Electron Microscopy Results
A typical electron micrograph of sieved small particles from a recycling plant sample is shown in Figure
4-9. Bright sampled particles appear against the gray background of the adhesive-coated carbon SEM
tab (Ted Pella, Inc., Redding, CA, USA). Micrographs also invariably contained artifacts that appear as
holes and tears on the adhesive surface. Field samples and recycling plant samples presented similar
electron micrographs. Particles were very polydisperse - generally, several large particles (50-100 (am)
were present along with many smaller particles. In the case of the sieve No. 230 samples, the particles
were often smaller than the 63-urn sieve openings. These could have been adsorbed on or aggregated
with larger particles during sieving and subsequently been released during storage. Bottom pan particle
distributions were also polydisperse (see example in Figure 4-10), with most particles having projected
areas less than 700 jim2per particle. These areas correspond to nominal diameters of less than about 30
j.im, assuming spherical particle shape.
Particle area analyses were conducted on the 16 images obtained from each sample, using Image J
software (ImageJ/Fiji, version 1.46r, National Institutes of Health, Bethesda, MD, USA; Ferreira and
Rasband, 2012). Given the background noise from the SEM tabs, a lower limit of 30 jim2 projected area
was set for particle analysis. Summary results for the 9 field samples and 9 recycling plant samples are
shown in Table 4-32 (one bottom pan fraction had insufficient sample to analyze). Using a two-tailed t-
test with a significance level of 0.05, the null hypothesis that the means of the field and recycling plant
mean areas are the same can be rejected for the Sieve 230 fraction, but it cannot be rejected for the
bottom pan (nominally < 63 um) fraction.
100 |jm
EHT = 25.00 kV
Signal A = NTS BSD
Date :31 Aug 2017
WD = 6.7 mm
Sample ID =
Mag = 151X
Figure 4-9. Representative electron micrograph of small particles
seived from a recycling plant tire crumb rubber sample.
110
-------
1000
Particle Area (um2)
Figure 4-10. Representative histogram of the frequency of individual particle areas observed
in the bottom pan sample, fim = micrograms
Table 4-32. Particle Areas for Tire Crumb Rubber at Recycling Plants and Synthetic Turf Fields
Particle Size Fraction
Recycling
Plants
n
Recycling
Plants
Mean (//m2)
Recycling
Plants
Standard
Deviation
(//m2)
Synthetic
Turf Fields
n
Synthetic
Turf Fields
Mean (//m2)
Synthetic
Turf Fields
Standard.
Deviation
(//m2)
Sieve 230 fraction
(0.063- to 0.125-mm)
9
1000
300
9
2400
1200
Bottom pan fraction
(< 0.063 mm)
8
1000
420
9
1300
630
A more detailed inspection of the bottom pan results was conducted by dividing the particles into area
ranges of 30-314 |im2, > 314-962 |im2, > 962- 1963 |im2, > 1963 -3318 |im2, and > 3318 |im2. These
ranges correspond to nominal diameters (assuming spherical particles) of about 5-20 |im, >20-35
|im, > 35-50 |im, > 50-65 |im, and > 65 |im. Quartiles were then calculated for the field samples and
recycling plant samples separately. The results are presented in Table 4-33. While the smallest fraction
(< 20-|im nominal diameter) ranged from 12% to 57% of the total particle number for field samples, it
always accounted for at least 34%, and up to 76%, of the particles from recycling plant samples. The
reason for the more uniformly fine particles in the plant samples is not clear but given that particles in
the < 20-|im range are probably more relevant to inhalation exposure, this property may be important.
ill
-------
Table 4-33. Quartile Analyses of Recycling Plant and Synthetic Turf Field Particle Numbers in the Bottom Sieve
Pan (< 0.063 mm) Samples
Tire Crumb
Rubber Sampling
Location
Quartile
Bounds
% Bottom
Pan Particles
30 - 314 fim2
% Bottom
Pan Particles
> 314 - 962 fim2
% Bottom
Pan Particles
> 962 - 1963 fim2
% Bottom
Pan Particles
> 1963 - 3318 fim2
% Bottom
Pan Particles
> 3318 fim2
Recycling Plants
Minimum
34%
11%
6.9%
3.2%
2.0%
Recycling Plants
Quartile 1
52%
12%
7.9%
4.6%
3.5%
Recycling Plants
Quartile 2
57%
15%
14%
9.3%
5.7%
Recycling Plants
Quartile 3
67%
17%
15%
11%
9.1%
Recycling Plants
Max
76%
19%
23%
14%
11%
Synthetic Turf
Fields
Minimum
12%
4.1%
10%
5.5%
2.3%
Synthetic Turf
Fields
Quartile 1
28%
12%
15%
7.2%
2.8%
Synthetic Turf
Fields
Quartile 2
34%
23%
22%
12%
10%
Synthetic Turf
Fields
Quartile 3
47%
26%
26%
15%
13%
Synthetic Turf
Fields
Maximum
57%
31%
28%
33%
23%
4.5.4.2 Electron Probe Microanalysis Results
Electron probe microanalysis (EPMA) was performed on selected particles to evaluate its utility for
determination of particle composition. Two EPMA modes were used. In the first, the electron beam was
maintained at one location for the entirety of the X-ray acquisition. This single-point mode maximizes
the signal-to-noise ratio and allows the elemental composition of very small particles to be determined.
In Figure 4-11 A, EPMA results are shown for two particles. The large particle in the center of the
electron micrograph has X-ray peaks for sulfur (S) and zinc (Zn; Figure 4-1 IB), which is consistent with
a rubber particle. However, the small particle above the large central particle has prominant aluminum
(Al), silicon (Si), potassium (K), and iron (Fe) peaks, along with a little sulfur (S), which is definitely
not rubber and could be an alumina silicate dust or soil particle.
112
-------
Figure 4-11. A) Electron micrograph of small particle cluster from a field sample; B) EPMA spectrum of
the center of the large center particle; C) Spectrum of smaller particle above the central particle. [EPMA =
Electron probe microanalysis; A1 = Aluminum; Fe = Iron; K = Potassium; Na = Sodium; O = Oxygen; S = Sulfur; Si =
Silicon; Y = Yttrium; Zn = Zinc]
EPMA was also performed in the elemental-mapping mode, in which X-ray spectra are obtained for
every point in the electron micrograph as the electron beam rasters. This mode is much less sensitive
than the single-point mode, but it allows visualization of the distribution of the major elemental
components of a particle. In Figure 4-12A, the sulfur distribution in the particle indicates that the main
body is consistent with rubber. The multi-element maps (Figure 4-12B and C) show the distribution of
several elements in separate smaller particles on the surface of the large particle. Note the co-occurrence
of iron (Fe) and chromium (Cr) in Figure 4-12B, possibly indicating steel particles.
In future studies, elemental mapping could also give a rough estimate of the fraction of rubber versus
non-rubber particles. Figure 4-13 shows a backscatter electron micrograph of a recycling plant sample,
as well as an elemental mapping of sulfur, silicon, and calcium (Ca). Assuming that only particles with
high sulfur content are tire crumb nibber (an upper estimate, given that there could be, for example,
inorganic sulfate particles as well), it appears that there are a number of rubber particles in this area of
the SEM tab. There are also several particles of high Si or Ca content, possibly crustal in origin. Also,
note that particles with high calcium are easily distinguished from Si- or S- bearing particles even in the
backscatter electron micrograph, due to the greater primary electron scatter of the higher atomic number
Ca.
113
-------
1183Date:9/19/2017 10:18:27 PMImage
size: 1000 x 750Mag:150xHV:25.0kV
, " ,
»* //; y -
yf:
¦»>J' % .*• %
Si 2
c
Figure 4-12. Three EPMA element mapping images. A) Original electron micrograph; B) Sulfur map
indicating primary rubber particle; and C) multielement map showing inclusions probably steel
(Fe+Cr) and possibly soil (Si, Ca). [EPMA = Electron probe microanalysis; Ca = Calcium; Cr = Chromium: Fe =
Iron; Mg = Magnesium; S = Sulfur; Si = Silicon]
1186Date:9/19/2017 10:51:19 PMImage
size: 1000 x 750Mag:150xHV:25.0kV
Figure 4-13. A) Backscatter electron micrograph of a recycling plant sample, and B) elemental
mapping of sulfur, silicon, and calcium. [Ca = Calcium; S = Sulfur; Si = Silicon]
4.5.4.3 Summary of SEM/EPMA Studies
The SEM analysis of bottom pan and sieve No. 230 samples demonstrated that these size fractions are
generally very polydisperse, although it appears that the bottom pan fractions from recycling plants have
a higher fraction of very small particles than do those from field samples. The minimum size analyzed in
this study was approximately 5-^m nominal diameter, limited by the image analysis noise caused by the
adhesive-coated sample tabs. The analysis approach did not allow study of potential tire crumb rubber
particles < 5-|iin nominal diameter, which limits current understanding about the presence of, and
potential for exposures to, fine particles and nanoparticles. Before future SEM studies are conducted to
determine particle size distributions and particle morphology, alternative means of sampling using
114
-------
smoother SEM stub substrates, as well as the use of optical microscopy, should be investigated.
Nanoparticle analysis is probably outside the scope of SEM analysis until very different sampling
procedures are developed.
The selected EPMA analyses were conducted as a proof-of-concept study and demonstrated high
elemental sensitivity on small particles in the single-point mode. The elemental-mapping mode could
possibly be used to selectively analyze rubber particles, as well as investigate adsorption of metals on
rubber particles.
4.6 Chemical Measurement Summary Statistics
4.6.1 Direct Tire Crumb Rubber Chemical Substance Measurements
Several types of quantitative analyses of target analytes were performed to measure chemical substances
potentially associated with tire crumb rubber from recycling plants and tire crumb rubber infill from
synthetic turf fields. Summary statistics were generated from the 27 samples collected from nine
recycling plants and from 40 composite samples collected from synthetic turf fields. Summary statistic
results are reported here for a subset of the chemical substances selected for highlighting, with complete
results for all target analytes shown in Appendix I. Results for the following analysis types are included
in this summary statistics reporting subsection for tire crumb rubber sampled from recycling plants and
synthetic turf fields:
• Metals analyzed by ICP/MS
• Metals analyzed by XRF
• SVOCs analyzed in solvent extracts by GC/MS/MS
• SVOCs non-quantitative analysis of solvent extracts by LC/TOFMS
• VOC emission factors from analysis by GC/TOFMS
• SVOC emission factors from analysis by GC/MS/MS
• SVOC non-quantitative emission results from analysis by LC/TOFMS
More direct comparisons of results between recycling plants and synthetic turf fields are described in
section 4.7, so much of the narrative in this section focuses on results from synthetic turf fields.
4.6.1.1 Metals by ICP/MS Analysis
Tire crumb rubber from recycling plants and tire crumb rubber infill from synthetic turf fields was
quantitatively analyzed for 21 metals by acid extraction and ICP/MS analysis, with 19 of those metals
measurable above the method detection limit in 100% of the samples. Selenium was not measured above
the method detection limit in any sample. Compounds of two metals, zinc and cobalt, are used in tire
manufacturing, and several other target analyte metals may be present if steel belts and cords are not
fully excluded in the tire recycling process.
Summary statistics are reported in Table 4-34. Average values for metal concentrations in tire crumb
rubber from synthetic turf fields ranged from 0.38 mg/kg for arsenic up to 15000 mg/kg for zinc.
Average concentrations of cobalt and lead were 140 mg/kg and 24 mg/kg, respectively. Maximum
values for synthetic turf field samples were 160 mg/kg, 22,000 mg/kg, 290 mg/kg, and 3.7 mg/kg for
lead, zinc, cobalt, and chromium, respectively. Examples of the measurement results across the 40
synthetic turf fields are shown in Figure 4-14 for chromium, cobalt, lead, and zinc.
115
-------
Table 4-34. Summary Statistics for Select Metals Analyzed by ICP/MS in Tire Crumb Rubber Samples Collected from Tire Recycling Plants and Tire
Crumb Rubber Collected from Synthetic Turf Fields3
Tire Crumb Rubber
Sampling Location
Chemical
n
%
> LOD
Mean
(m«/k«)
Standard
Deviation
(m«/k«)
% Relative
Standard
Deviation
10th
Percentile
(m«/k«)
25th
Percentile
(mg/kg)
50th
Percentile
(m«/k«)
75th
Percentile
(mg/kg)
90th
Percentile
(m«/k«)
Maximum
(mg/kg)
Recycling Plants
Arsenic
27
100
0.30
0.088
29
0.20
0.24
0.28
0.37
0.45
0.51
Recycling Plants
Cadmium
27
100
0.55
0.13
23
0.40
0.45
0.55
0.63
0.73
0.93
Recycling Plants
Chromium
27
100
1.8
0.70
39
1.0
1.2
1.7
2.0
2.4
3.6
Recycling Plants
Cobalt
27
100
190
87
46
96
120
180
250
280
440
Recycling Plants
Lead
27
100
13
10
78
7.7
9.4
10
14
22
61
Recycling Plants
Zinc
27
100
17000
3500
20
13000
14000
16000
20000
21000
25000
Synthetic TurfFiclds
Arsenic
40
100
0.38
0.20
52
0.19
0.26
0.34
0.45
0.60
1.1
Synthetic TurfFiclds
Cadmium
40
100
0.95
0.68
72
0.49
0.57
0.70
1.1
1.7
4.2
Synthetic TurfFiclds
Chromium
40
100
1.6
0.84
51
0.97
1.2
1.6
1.9
2.7
3.7
Synthetic TurfFiclds
Cobalt
40
100
140
60
44
68
85
120
180
220
290
Synthetic TurfFiclds
Lead
40
100
24
26
110
9.3
11
14
25
55
160
Synthetic TurfFiclds
Zinc
40
100
15000
3000
20
11000
13000
14000
16000
19000
22000
11 ICP/MS = Inductively coupled plasma/mass spectrometry; LOD = Limit of detection
116
-------
Chromium
Cobalt
or
01
200-
5 10 1S 20 25 30 35 40
Field ID
5 10 15 20 25 30 35 40
Field ID
Lead
Zinc
o> 80
10 15 20 25 30 35
Field ID
20000
Oi 16000
15 20 25 30 35 40
Field ID
Figure 4-14. ICP/MS metal analysis results (mg/kg) for chromium, cobalt, lead, and
zinc from tire crumb rubber infill composite samples collected from each synthetic turf field.
[ICP/MS = Inductively coupled plasma/mass spectrometry]
4.6.1.2 Metals by XRF Analysis
Tire crumb rubber from recycling plants and tire crumb rubber infill from synthetic turf fields was
quantitatively analyzed for 17 metals by x-ray fluorescence spectroscopy analysis, with 10 of those
metals (chromium, cobalt, lead, zinc, barium, copper, iron, molybdenum, rubidium, and strontium)
measurable above the method detection limit in 100% of the samples and seven metals below 10%
measurable above the method detection limit (arsenic, cadmium, antimony, manganese, nickel,
selenium, and tin).
Summary statistics are reported in Table 4-35. Average values for metal concentrations in synthetic turf
fields ranged from 14 mg/kg for chromium up to 33,000 mg/kg for zinc. Average concentrations of
cobalt and lead were 39 mg/kg and 36 mg/kg, respectively. Maximum values for synthetic turf field
samples were 110 mg/kg, 47,000 mg/kg, 69 mg/kg, and 20 mg/kg for lead, zinc, cobalt, and chromium,
respectively.
117
-------
Table 4-35. Summary Statistics for Selected Metals Analyzed by XRF in Tire Crumb Rubber Samples Collected from Tire Recycling Plants and Tire
Crumb Rubber Infill collected from Synthetic Turf Fields3
Tire Crumb Rubber
Sampling Location
Chemical
n
%
> LOD
Mean
(m«/k«)
Standard
Deviation
(m«/k«)
% Relative
Standard
Deviation
10th
Percentile
(m«/k«)
25th
Percentile
(mg/kg)
50th
Percentile
(m«/k«)
75th
Percentile
(mg/kg)
90th
Percentile
(m«/k«)
Maximum
(mg/kg)
Recycling Plants
Arsenic
27
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Recycling Plants
Cadmium
27
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Recycling Plants
Chromium
27
100
15
4
26
10
12
15
18
21
25
Recycling Plants
Cobalt
27
100
58
35
61
24
31
52
72
130
150
Recycling Plants
Lead
27
100
35
8.6
25
23
29
37
41
47
54
Recycling Plants
Zinc
27
100
39000
8800
22
30000
32000
36000
48000
54000
58000
Synthetic Turf Fields
Arsenic
40
3
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
12
Synthetic Turf Fields
Cadmium
40
8
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
27
Synthetic Turf Fields
Chromium
40
100
14
2.9
21
10
12
13
16
17
20
Synthetic Turf Fields
Cobalt
40
100
39
17
44
15
22
43
52
61
69
Synthetic Turf Fields
Lead
40
100
36
22
61
15
22
33
44
54
110
Synthetic Turf Fields
Zinc
40
100
33000
7100
22
26000
29000
31000
37000
45000
47000
11 XRF = X-ray fluorescence; LOD = Limit of detection
*Values reported only when % >LOD is > 60%.
118
-------
Average XRF measurement results were substantially higher than ICP/MS measurements for arsenic,
cadmium, chromium, lead and zinc, and substantially lower for cobalt. The ICP/MS approach was based
on known analyte concentration calibration solutions, while the XRF method did not have an exact
analog to the tire crumb rubber for calibration assessment. Given some of the substantial differences in
measurement results between XRF and ICP/MS, it appears more work may be needed before applying
XRF as a field measurement method for obtaining accurate measurements.
4.6.1.3 SVOCs by GC/MS/MS Analysis
Tire crumb rubber from recycling plants and tire crumb rubber infill from synthetic turf fields was
quantitatively analyzed for 39 target SVOCs by acetone/hexane solvent extraction and GC/MS/MS
analysis. Target analytes included PAHs, phthalates, other tire rubber chemicals or degradates, and
several chemicals previously reported in other studies. Most analytes were measurable above the method
detection limit in 100% of the samples.
Summary statistics are reported in Table 4-36 for SVOCs analyzed by GC/MS/MS. Average values for
SVOC concentrations in tire crumb rubber infill collected from synthetic turf fields ranged from 0.67
mg/kg for aniline to 43 mg/kg for bis(2-ethylhexyl) phthalate. The average value for pyrene, the most
abundant of the quantified PAHs, was 12 mg/kg, while the average result for the sum of 15 PAH
compounds was 29 mg/kg. Examples of average measurement results for samples collected at recycling
plants vs. synthetic turf fields include pyrene (18 vs. 12 mg/kg), benzo[a]pyrene (0.74 vs. 0.78 mg/kg),
benzothiazole (79 vs. 11 mg/kg), 4-tert-octylpheol (30 vs. 9.8 mg/kg) and bis(2-ethylhexyl) phthalate
(12 vs. 43 mg/kg). Maximum values for SVOCs in synthetic turf field samples were 25 mg/kg, 3.0
mg/kg, 54 mg/kg, 33 mg/kg, and 170 mg/kg, respectively, for pyrene, benzo[a]pyrene, benzothiazole, 4-
tert-octylphenol, and bis(2-ethylhexyl) phthalate.
Examples of the measurement results across the 40 synthetic turf fields are shown in the Figure 4-15 and
4-16 scattergraphs for eight SVOC analytes. For some SVOCs, the majority of the measurements at the
40 fields were below a certain concentration (e.g., majority of samples below 5 mg/kg for phenanthrene,
below 1 mg/kg for benzo[a]pyrene, below 20 mg/kg for benzothiazole, below 10 mg/kg for 4-tert-
octylphenol, below 50 mg/kg for bis(2-ethylhexyl) phthalate, and below 2 mg/kg for n-hexadecane);
while other showed different patterns.
119
-------
Table 4-36. Summary Statistics for Selected SVOCs Analyzed by GC/MS/MS in Solvent Extracts for Tire Crumb Rubber Samples Collected from Tire
Recycling Plants and Tire Crumb Rubber Infill Collected from Synthetic Turf Fields3
Tire Crumb Rubber
Sampling Location
Chcmicalb
n
%
> LOD
Mean
(mg/kg)
Standard
Deviation
(mg/kg)
% Relative
Standard
Deviation
10th
Percentile
(mg/kg)
25th
Percentile
(mg/kg)
50th
Percentile
(mg/kg)
75th
Percentile
(mg/kg)
90th
Percentile
(mg/kg)
Maximum
(mg/kg)
Recycling Plants
Phenanthrene
27
100
3.6
1.3
35
1.8
2.6
3.6
4.5
5.8
5.9
Recycling Plants
Fluoranthene
27
100
6.1
1.7
27
4.3
4.8
5.8
6.7
8.6
10
Recycling Plants
Pyrene
27
100
18
2.4
13
16
17
18
20
22
23
Recycling Plants
Benzo[a]pyrene
27
100
0.74
0.39
52
0.39
0.47
0.64
0.95
1.4
1.9
Recycling Plants
Benzo [ghijperylene
27
100
1.3
0.59
45
0.82
0.97
1.1
1.3
2.0
3.4
Recycling Plants
Suml5PAH
27
100
41
8.9
22
31
34
39
49
53
62
Recycling Plants
Benzothiazole
27
100
79
19
24
54
61
79
96
100
110
Recycling Plants
Dibutyl phthalate
27
100
0.68
0.44
65
0.27
0.31
0.44
0.85
1.5
1.7
Recycling Plants
Bis(2-ethylhexyl)
phthalate
27
100
12
14
120
2.9
3.5
6.1
15
34
58
Recycling Plants
Aniline
27
100
3.8
1.8
47
2.3
2.3
2.6
5.5
6.3
7.2
Recycling Plants
4-tert-octylphenol
27
100
30
6.2
21
23
25
30
34
40
46
Recycling Plants
n-Hexadecane
27
100
3.6
1.8
51
1.8
2.1
2.7
5.5
6.5
6.6
Synthetic Turf Fields
Phenanthrene
40
100
2.3
2.6
110
0.26
0.44
1.1
3.3
6.1
10
Synthetic Turf Fields
Fluoranthene
40
100
4.5
2.6
57
2.0
2.4
3.9
6.5
8.1
10
Synthetic Turf Fields
Pyrene
40
100
12
6.2
49
4.2
7.0
13
17
21
25
Synthetic Turf Fields
Benzol ajpvrcnc
40
100
0.78
0.52
66
0.38
0.43
0.62
0.91
1.4
3.0
Synthetic Turf Fields
Bcn/.o|ghi|pcrvlcnc
40
100
1.3
0.64
49
0.47
0.64
1.4
1.8
2.0
2.8
Synthetic Turf Fields
Suml5PAH
40
100
29
15
51
13
17
27
38
49
68
Synthetic Turf Fields
Bcn/.othia/.olc
40
100
11
13
120
1.1
1.8
7.0
14
31
54
Synthetic Turf Fields
Dibutvl phthalate
40
100
1.5
1.5
100
0.054
0.26
0.97
2.3
3.5
6.6
Synthetic Turf Fields
Bis(2-ethv lliexv 1)
phthalate
40
100
43
42
100
4.9
7.8
28
58
100
170
Synthetic Turf Fields
Aniline
40
100
0.67
0.53
79
0.16
0.27
0.57
0.96
1.2
2.4
Synthetic Turf Fields
4-tcrt-oclylphcnol
40
100
9.8
9.7
99
0.90
2.5
5.6
16
27
33
Synthetic Turf Fields
n-Hexadecane
40
100
0.94
1.3
130
0.079
0.10
0.26
1.3
2.6
5.4
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry; LOD = Limit of Detection
b Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
120
-------
Phenanthrene
100-
25
Pyrene
20-
7.5
Be nzo(a )pyre ne Su m 15 PAH
20
40
35
40
25
20-
Field ID Field ID
Figure 4-15. GC/MS/MS extract analysis results (mg/kg) for phenanthrene, pyrene,
benzo[a]pyrene, and the sum of 15 PAH from tire crumb rubber infill composite samples
collected from each synthetic turf field. [GC/MS/MS = Gas chromatography /tandem mass spectrometry;
Suml5PAH = Sum of 15 of the 16 EPA "priority' PAHs, including Acenaphthvlene. Anthracene,
Benz[a]anthracene. Benzo[ajpyrene. Benzo(b)fluoranthene, Benzo|ghi]perylene, Benzo(k)fluoranthene,
Chiysene, Dibenz[a,h]antliracene, Fluoranthene. Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene,
Phenantlirene, Pyrene]
121
-------
Berizothiazole 4-tert-OctyIphenol
O)
30-
20-
20-
5 10 15 20 25 30 35 40 5 10 15 20 25 30 35 40
Field ID Field ID
Bis(2-ethylhexyl) phthalate n-Hexadecane
150
100
o>
on
20
40
Field ID Field ID
Figure 4-16. GC/MS/MS extract analysis results (mg/kg) for benzothiazole, 4-tert-octylphenol,
bis(2-ethylhexyl) phthalate, and n-hexadecane from tire crumb rubber infill composite samples
collected from each synthetic turf field. [GC/MS/MS = Gas chromatography/tandem mass spectrometry]
4.6.1 A SVOCs by LC/TOFMS Analysis
Summary statistics are reported in Table 4-37 for SVOCs analyzed by LC/TOFMS. This analysis was not
quantitative based on analysis of target analyte calibration solutions. However, known chemical
standards were used to confirm retention times and spectra for these analytes. Results are shown for
chromatographic peak area counts to gauge the relative amounts of chemicals present. The analytes 2-
hydroxybenzothiazole, cyclohexylamine, di-cyclohexylamine, N-cyclohexyl-N-methylcyclohexanamine,
and diisononylphthalate were measured in 100% of the tire crumb rubber infill samples collected at
synthetic turf fields. The analytes 2-mercaptobenzothiazole and diisodecylphthalate were measured above
the method detection limit in at least 73% of the samples.
122
-------
Table 4-37. Summary Statistics for Selected SVOCs Analyzed Non-quantitatively by LC/TOFMS in Solvent Extracts for Tire Crumb Rubber Samples
Collected from Tire Recycling Plants and Tire Crumb Rubber Infill Collected from Synthetic Turf Fieldsa b c
Tire Crumb
Rubber Sampling
Location
Chemical
n
%
> LOD
Mean
Area
Counts
Area Counts
Standard
Deviation
% Relative
Standard
Deviation
10th
Percentile
Area
Counts
25th
Percentile
Area
Counts
50th
Percentile
Area
Counts
75th
Percentile
Area
Counts
90th
Percentile
Area
Counts
Maximum
Area
Counts
Recycling Plants
2-mercaptobenzothiazole
27
100
1.5E+04
1.8E+04
130
1.1E+03
1.9E+03
4.1E+03
2.8E+04
4.9E+04
5.3E+04
Recycling Plants
2-hydroxybenzothiazole
27
100
3.1E+05
1.1E+05
37
2.0E+05
2.6E+05
3.1E+05
3.7E+05
4.8E+05
5.5E+05
Recycling Plants
cyclohexylamine
27
100
2.1E+06
1.4E+06
70
3.3E+05
6.0E+05
2.2E+06
3.3E+06
3.7E+06
5.6E+06
Recycling Plants
di-cyclohexylamine
27
100
1.4E+07
1.8E+07
130
9.0E+05
1.2E+06
4.3E+06
2.9E+07
4.3E+07
5.8E+07
Recycling Plants
N-cyclohexyl-N-
methylcyclohexanamine
27
100
1.9E+06
1.7E+06
94
2.6E+05
5.5E+05
1.0E+06
2.5E+06
4.5E+06
6.6E+06
Recycling Plants
diisononylphthalate
27
96
7.9E+04
1.6E+05
200
-1.3E+04
-1.3E+04
-1.2E+04
1.7E+05
3.2E+05
5.6E+05
Recycling Plants
diisodecylphthalate
27
93
5.5E+03
6.2E+03
110
7.2E+02
1.7E+03
3.1E+03
5.6E+03
1.7E+04
1.9E+04
Synthetic Turf
Fields
2-mercaptobcn/.olhia/.olc
40
73
1.9E+03
3.4E+03
190
< LOD
< LOD
3.1E+02
1.8E+03
6.6E+03
1.5E+04
Synthetic Turf
Fields
2-hydroxybcnzolhiazolc
40
100
1.0E+05
1.2E+05
120
1.7E+03
6.9E+03
3.2E+04
1.8E+05
3.1E+05
4.2E+05
Synthetic Turf
Fields
cyclohexylamine
40
100
4.9E+05
7.9E+05
160
8.9E+03
2.2E+04
1.2E+05
4.1E+05
2.0E+06
2.7E+06
Synthetic Turf
Fields
di -cvc lo hexv la mi nc
40
100
9.0E+06
8.5E+06
95
4.6E+05
1.4E+06
8.1E+06
1.3E+07
2.2E+07
3.2E+07
Synthetic Turf
Fields
N-cvclohexyl-N-
mclhylcyclohcxanaminc
40
100
2.3E+05
3.0E+05
130
8.1E+03
4.2E+04
1.3E+05
3.7E+05
5.0E+05
1.7E+06
Synthetic Turf
Fields
diisononvlphlluilalc
40
100
2.8E+04
9.4E+04
330
-1.1E+04
-9.8E+03
-7.4E+03
8.6E+02
1.8E+05
4.2E+05
Synthetic Turf
Fields
diisodecylphthalate
40
85
4.8E+04
2.7E+05
560
< LOD
2.1E+03
4.3E+03
7.5E+03
1.7E+04
1.7E+06
a SVOC = Semivolatile organic compound; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry; LOD = Limit of detection
bNo quantitative analysis was performed. Chromatographic area counts were reported. Chemical identities and retention times confirmed with purchased chemical
standards.
0 Several results are reported as negative values. This is a result of the subtraction of blank values from the sample measurement results. Although this does not represent a
physical reality, the negative results are retained as part of the distribution of corrected results.
123
-------
4.6.2 Chemical Emissions from Tire Crumb Rubber
4.6.2.1 VOC Emission Factors Analysis
Tire crumb rubber from recycling plants and tire crumb rubber infill from synthetic turf fields was
quantitatively analyzed for 31 target VOCs by chamber emission testing at 25 °C and at 60 °C with
HPLC/UV analysis for formaldehyde and GC/TOFMS analysis for the remainder of the VOC analytes.
Emission factor results are reported in units of ng/g/h, which is nanograms of analyte emitted per gram
of tire crumb rubber per hour. Some emission factor statistics are reported as negative values; this is
because some measurements were below the average chamber background measurements, resulting in
slightly negative results following chamber background subtraction.
The target analytes included methyl isobutyl ketone and benzothiazole, which have been previously
reported in tire crumb rubber headspace analysis and samples in the air above synthetic turf fields. Other
analytes include the BTEX chemicals benzene, toluene, ethylbenzene, the co-eluting m/p-xylenes, and
o-xylene. Styrene and 1,3-butadiene were measured as potential chemicals of interest as well, because
tires are often constructed with styrene-butadiene rubber (SBR). There is minimal information from
previous studies regarding the presence and emissions of styrene and 1,3-butadiene from tire crumb
rubber, and it is important to understand the extent that these two elastomer-building monomers might
remain present and available for exposure. Formaldehyde was also included since it was previously
reported in emissions testing of tire-derived flooring and is reportedly used in tire manufacturing. Many
of the other analytes, including chlorinated VOCs and Freon™ chemicals were included on the list as
typical chemicals for ambient air monitoring, with some having been reported in previous tire crumb
rubber studies.
VOC Emissions at 25 °C -The complete VOC 25 °C emission factor measurement dataset is reported in
Appendix I, Table 1-9. Nine (9) of the 31 analytes from synthetic turf field tire crumb rubber infill
samples were not measured above the method detection limit, with the remainder having between 3 and
100% measurable. Benzothiazole, o-xylene, the sum of BTEX chemicals, trichlorofluoromethane (Freon
11), and dichlorofluoromethane (Freon 12) were the only analytes with > 60% of measurements above
the method detection limits. Their average emission factors were 25 ng/g/h, 0.032 ng/g/h, 0.31 ng/g/h,
0.034 ng/g/h, and -0.022 ng/g/h, respectively. Their maximum emission factors were 110 ng/g/h, 0.34
ng/g/h, 2.9 ng/g/h, 1.1 ng/g/h, and 0.056 ng/g/h, respectively. Notably, all formaldehyde measurements
were below quantifiable limits for synthetic field tire crumb rubber infill, while 1,3-butadiene and
styrene measurements were above quantifiable limits in only a few samples and the emission factors
were low for these few samples (<1.0 ng/g/h). Overall, VOC emission factors were low for most of the
target analytes, often below the method detection limit and/or the chamber background levels. Summary
statistics are reported in Table 4-38 for 25 °C VOC emission factor measurement results for select
analytes.
124
-------
Table 4-38. Summary Statistics for Selected VOC 25 °C Emission Factors for Tire Crumb Rubber Samples Collected from Tire Recycling Plants and
Tire Crumb Rubber Infill Collected from Synthetic Turf Fieldsa'b
Tire Crumb Rubber
Sampling Location
Chemical'
N
%
> LOD
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
10"'
Percentile
(ng/g/h)
25th
Percentile
(ng/g/h)
50th
Percentile
(ng/g/h)
75th
Percentile
(ng/g/h)
90th
Percentile
(ng/g/h)
Maximum
(ng/g/h)
Recycling Plants
Formaldehyde
26
11
*
*
*
< LOD
< LOD
< LOD
< LOD
8.8
25
Recycling Plants
Methyl isobutyl ketone
27
96
24
16
65
5.7
14
21
31
48
72
Recycling Plants
Benzothiazole
27
96
150
41
28
93
130
150
180
180
180
Recycling Plants
1,3-Butadiene
27
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Recycling Plants
Styrene
27
85
0.31
0.21
69
< LOD
0.16
0.23
0.41
0.70
0.87
Recycling Plants
Benzene
27
44
*
*
*
< LOD
< LOD
< LOD
0.33
0.76
1.4
Recycling Plants
Toluene
27
93
0.39
0.35
91
0.027
0.095
0.24
0.61
0.99
1.3
Recycling Plants
Ethylbenzene
27
41
*
*
*
< LOD
< LOD
< LOD
0.086
0.17
0.27
Recycling Plants
m/p-Xylene
27
96
0.86
0.81
95
0.13
0.32
0.63
1.2
1.6
3.7
Recycling Plants
o-Xylene
27
93
0.21
0.20
93
0.0077
0.095
0.16
0.32
0.45
0.89
Recycling Plants
SumBTEX
27
100
1.7
1.3
77
0.10
0.86
1.5
2.7
3.4
5.4
Synthetic Turf Fields
Formaldehyde
38
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Synthetic Turf Fields
Methyl isobutyl ketone
38
58
*
*
*
< LOD
< LOD
0.87
1.4
4.5
20
Synthetic Turf Fields
Bcn/.othia/.olc
38
63
25
28
110
< LOD
< LOD
15
40
72
110
Synthetic Turf Fields
1.3-Butadicnc
38
13
*
*
*
< LOD
< LOD
< LOD
< LOD
0.094
0.23
Synthetic Turf Fields
Styrene
38
21
*
*
*
< LOD
< LOD
< LOD
< LOD
0.30
1.0
Synthetic Turf Fields
Benzene
38
18
*
*
*
< LOD
< LOD
< LOD
< LOD
0.74
2.2
Synthetic Turf Fields
Toluene
38
26
*
*
*
< LOD
< LOD
< LOD
0.081
0.27
0.77
Synthetic Turf Fields
Ethylbenzene
38
26
*
*
*
< LOD
< LOD
< LOD
0.032
0.089
0.48
Synthetic Turf Fields
m/p-Xvlcnc
38
50
*
*
*
< LOD
< LOD
0.0082
0.13
0.21
0.70
Synthetic Turf Fields
o-Xylene
38
76
0.032
0.09
290
< LOD
-0.028
0.0088
0.077
0.14
0.34
Synthetic Turf Fields
SumBTEX
38
89
0.31
0.84
270
< LOD
-0.23
0.044
0.54
1.3
2.9
11 VOC = Volatile organic compound; LOD = Limit of detection
b Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
0 SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene results.
*Values reported only when % > LOD is > 60%.
125
-------
VOC Emissions at 60 °C - The complete VOC 60 °C emission factor measurement dataset is reported in
Appendix I, Table 1-10. Seven (7) of the 31 analytes from synthetic turf field tire crumb rubber infill
samples were not measured above the method detection limit, with the remainder having between 3 and
100% measurable. Benzothiazole, methyl isobutyl ketone and formaldehyde had average emission
factors of 56 ng/g/h, 42 ng/g/h, and 16 ng/g/h, respectively. Their maximum emission factors were 110
ng/g/h, 96 ng/g/h, and 48 ng/g/h, respectively. Interestingly, the BTEX chemical emission factors were
not higher than those in the 25 °C emissions tests and were often below the average chamber
background levels. For 1,3-butadiene, measurements were above quantifiable limits in only a few
samples, and for both 1,3-butadiene and styrene the emission factors were low (< 1.3 ng/g/h). Examples
of the emission factor measurement results across the 40 synthetic turf fields are shown in Figure 4-17
for benzothiazole, methyl isobutyl ketone, styrene, and formaldehyde. Summary statistics are reported in
Table 4-39 for 60 °C VOC emission factor measurement results for select analytes.
Further comparisons of VOC emission results at the two chamber test temperatures are illustrated and
discussed in section 4.8.1.
Formaldehyde
Benzothiazole
Temperalu re *60 C
Temperatore=60!'C
Field ID
Field ID
Methyl Isobutyl Ketone
Styrene
Temperature=80 'C
Temper8lure-60 C
40
10
Field ID
Field ID
Figure 4-17. VOC 60 °C emission factor results (ng/g/h) for formaldehyde, benzothiazole,
methyl isobutyl ketone, and styrene from tire crumb rubber infill composite samples
collected from each synthetic turf field. [VOC = Volatile organic compound]
126
-------
Table 4-39. Summary Statistics for Selected VOC 60 °C Emission Factors for Tire Crumb Rubber Samples Collected from Tire Recycling Plants and
Tire Crumb Rubber
Sampling Location
Chemical'
n
%
> LOD
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
10"'
Percentile
(ng/g/h)
25th
Percentile
(ng/g/h)
50th
Percentile
(ng/g/h)
75th
Percentile
(ng/g/h)
90th
Percentile
(ng/g/h)
Maximum
(ng/g/h)
Recycling Plants
Formaldehyde
27
96
40
16
40
20
24
40
49
62
73
Recycling Plants
Methyl isobutyl ketone
27
100
140
15
11
110
130
130
150
160
160
Recycling Plants
Benzothiazole
27
100
220
8.3
3.7
210
220
220
230
230
240
Recycling Plants
1,3-Butadiene
27
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Recycling Plants
Styrene
27
100
1.1
0.58
53
0.33
0.55
1.0
1.6
1.9
2.1
Recycling Plants
Benzene
27
89
0.21
0.45
220
< LOD
-0.098
0.027
0.64
0.92
1.2
Recycling Plants
Toluene
27
100
1.1
0.95
85
0.20
0.30
0.64
1.7
2.6
3.2
Recycling Plants
Ethylbenzene
27
100
-0.0055
0.26
-4800
-0.22
-0.18
-0.13
0.092
0.52
0.68
Recycling Plants
m/p-Xylene
27
100
1.2
0.71
57
0.36
0.60
1.1
1.6
2.1
2.9
Recycling Plants
o-Xylene
27
100
-0.40
0.43
-110
-0.80
-0.73
-0.49
-0.28
0.23
0.79
Recycling Plants
SumBTEX
27
100
2.1
2.2
100
-0.57
0.36
1.9
3.4
5.7
7.7
Synthetic Turf Fields
Formaldehyde
40
75
16
9.5
58
< LOD
11
15
19
24
48
Synthetic Turf Fields
Methyl isobutyl ketone
37
100
42
26
61
15
22
34
61
87
96
Synthetic Turf Fields
Bcn/.othia/.olc
37
95
56
39
70
8.0
14
68
93
100
110
Synthetic Turf Fields
1.3-Butadiene
37
11
*
*
*
< LOD
< LOD
< LOD
< LOD
0.12
0.81
Synthetic Turf Fields
Styrene
37
100
0.45
0.41
91
-0.016
0.092
0.40
0.73
0.96
1.3
Synthetic Turf Fields
Benzene
37
49
*
*
*
< LOD
< LOD
< LOD
0.21
0.55
0.73
Synthetic Turf Fields
Toluene
37
100
0.15
0.31
200
-0.15
-0.048
0.07
0.22
0.72
0.91
Synthetic Turf Fields
Ethylbenzene
37
100
-0.082
0.22
-270
-0.33
-0.27
-0.16
0.14
0.28
0.40
Synthetic Turf Fields
m/p-Xvlcnc
37
100
0.24
1.0
410
-0.96
-0.58
0.16
0.73
1.7
2.5
Synthetic Turf Fields
o-Xylene
37
100
-0.35
0.66
-190
-0.99
-0.88
-0.44
-0.024
0.61
1.5
Synthetic Turf Fields
SumBTEX
37
100
-0.085
2.2
-2600
-2.5
-2.3
-0.40
0.94
3.3
4.6
11 VOC = Volatile organic compound; LOD = Limit of detection
b Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
0 SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene results.
*Values reported only when % >LOD is > 60%.
127
-------
4.6.2.2 SVOC Emission Factors Analysis
Tire crumb rubber from recycling plants and tire crumb rubber infill from synthetic turf fields was
quantitatively analyzed for 39 target SVOCs by chamber emission testing at 25 °C and at 60 °C with
GC/MS/MS analysis, and non-quantitatively for 10 target SVOCs at 60 °C with LC/TOFMS analysis.
Emission factor results are reported in units of ng/g/h, which is nanograms of analyte per gram of tire
crumb rubber per hour. Some emission factor statistics are reported as negative values; this is because
some measurements were below the average chamber background measurements, resulting in slightly
negative results following chamber background subtraction.
SVOC Emissions at 25 °C - The complete SVOC 25 °C emission factor measurement dataset is reported
in Appendix I, Table 1-13. Six of the 39 analytes from synthetic turf field tire crumb rubber infill
samples were not measured above the method detection limit, with the remainder having between 3 and
100% measurable. Eighteen of the analytes had > 60% of measurements above the method detection
limits. Average emission factors for benzothiazole, 4-tert-octylphenol and the sum of 15 PAH
compounds were 4.2 ng/g/h, 0.85 ng/g/h, and 0.62 ng/g/h, respectively. Their maximum emission factors
were 19 ng/g/h, 16 ng/g/h, and 3.1 ng/g/h, respectively. Overall, SVOC emission factors were low for
most of the target analytes, often below the method detection limit and/or the chamber background
levels. Summary statistics are reported in Table 4-40 for 25 °C SVOC emission factor measurement
results for selected analytes measured by GC/MS/MS.
SVOC Emissions at 60 °C - The complete SVOC 60 °C emission factor measurement dataset is reported
in Appendix I, Table 1-14. Seven of the 39 analytes from synthetic turf field tire crumb rubber infill
samples were not measured above the method detection limit, with the remainder having between 3 and
100%) measurable. Twenty-five of the analytes had > 60%> of measurements above the method detection
limits. Average emission factors for benzothiazole, 4-tert-octylphenol, pyrene, and the sum of 15 PAH
compounds were 34, 5.8, 0.29 and 2.0 ng/g/h, respectively. Their maximum emission factors were 220,
21, 0.89 and 9.4 ng/g/h, respectively. Emission factors for the five- and six-ring PAH compounds (e.g.,
benzo[a]pyrene, benzo(a)pyrene, benzo(k)fluoranthene, coronene) were rarely above the method
detection limits. Summary statistics are reported in Table 4-41 for 60 °C SVOC emission factor
measurement results measured by GC/MS/MS for select analytes. Examples of the emission factor
measurement results across the 40 synthetic turf fields are shown in Figure 4-18 for pyrene, the sum of
15 PAHs, benzothiazole, and 4-tert-octylphenol.
128
-------
Table 4-40. Summary Statistics for Select SVOC 25 °C Emission Factors for Tire Crumb Rubber Samples Collected from Tire Recycling Plants and Tire
Crumb Rubber Infill Collected at Synthetic Turf Fieldsa b
Tire Crumb Rubber
Sampling Location
Chemical'
n
%
> LOD
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
10"'
Percentile
(ng/g/h)
25th
Percentile
(ng/g/h)
50th
Percentile
(ng/g/h)
75th
Percentile
(ng/g/h)
90th
Percentile
(ng/g/h)
Maximum
(ng/g/h)
Recycling Plants
Phenanthrene
27
100
-0.0071
0.07
-980
-0.12
-0.02
0.014
0.037
0.051
0.087
Recycling Plants
Fluoranthene
27
22
*
*
*
< LOD
< LOD
< LOD
< LOD
0.0074
0.024
Recycling Plants
Pyrene
27
22
*
*
*
< LOD
< LOD
< LOD
< LOD
0.01
0.034
Recycling Plants
Benzo[a]pyrene
27
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Recycling Plants
Benzo [ghijperylene
27
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Recycling Plants
Suml5PAH
27
100
2.3
1.1
46
0.84
1.2
2.3
3.2
3.7
4.2
Recycling Plants
Benzothiazole
27
100
41
26
65
16
20
38
52
65
140
Recycling Plants
Dibutyl phthalate
27
100
-0.021
0.67
-3200
-0.50
-0.36
-0.067
0.14
0.44
2.9
Recycling Plants
Aniline
27
100
3.5
2.0
58
0.42
2.0
4.1
4.7
6.4
6.9
Recycling Plants
4-tert-octylphenol
27
100
0.47
0.25
52
0.21
0.31
0.42
0.63
0.80
1.3
Synthetic Turf Fields
Phenanthrene
40
100
0.025
0.049
200
-0.015
-0.00032
0.018
0.043
0.093
0.15
Synthetic Turf Fields
Fluoranthene
40
28
*
*
*
< LOD
< LOD
< LOD
0.0034
0.0085
0.016
Synthetic Turf Fields
Pyrene
40
20
*
*
*
< LOD
< LOD
< LOD
< LOD
0.011
0.04
Synthetic Turf Fields
Benzol a|pyrcnc
40
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Synthetic Turf Fields
Bcnzo|ghi Ipcrvlcnc
40
3
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
0.02
Synthetic Turf Fields
Suml5PAH
40
100
0.62
0.63
100
0.23
0.27
0.34
0.72
1.2
3.1
Synthetic Turf Fields
Benzolhia/.olc
40
100
4.2
5.2
120
0.043
0.49
1.8
5.3
12
19
Synthetic Turf Fields
Dibutvl phthalate
40
100
-0.011
0.38
-3500
-0.50
-0.20
-0.044
0.20
0.54
0.83
Synthetic Turf Fields
Aniline
40
88
0.34
0.45
130
< LOD
-0.0026
0.16
0.53
1.1
1.5
Synthetic Turf Fields
4-lerl-octylphenol
40
85
0.85
3.3
390
< LOD
-0.00074
0.082
0.23
0.43
16
a SVOC = Semivolatile organic compound; LOD = Limit of detection
b Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene.
*Values reported only when % >LOD is > 60%.
129
-------
Table 4-41. Summary Statistics for Select SVOC 60 °C Emission Factors for Tire Crumb Rubber Samples Collected from Tire Recycling Plants and Tire
Crumb Rubber Infill Collected from Synthetic Turf Fieldsa'b
Tire Crumb Rubber
Sampling Location
Chemical'
n
%
> LOD
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
10"'
Percentile
(ng/g/h)
25th
Percentile
(ng/g/h)
50th
Percentile
(ng/g/h)
75th
Percentile
(ng/g/h)
90"'
Percentile
(ng/g/h)
Maximum
(ng/g/h)
Recycling Plants
Phenanthrene
26
100
0.83
0.34
41
0.4
0.63
0.76
1.0
1.3
1.6
Recycling Plants
Fluoranthene
26
100
0.16
0.054
33
0.11
0.12
0.15
0.20
0.25
0.27
Recycling Plants
Pyrene
26
100
0.34
0.072
22
0.23
0.28
0.34
0.40
0.44
0.45
Recycling Plants
Benzo[a]pyrene
26
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Recycling Plants
Benzo [ghijperylene
26
4
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
0.013
Recycling Plants
Suml5PAH
26
100
13
7
56
4.8
7.6
13
16
18
38
Recycling Plants
Benzothiazole
26
100
520
340
66
220
290
400
690
950
1500
Recycling Plants
Dibutyl phthalate
26
100
0.21
0.72
350
-0.49
0.014
0.085
0.34
0.95
3
Recycling Plants
Aniline
26
100
23
7.2
31
18
19
21
25
34
46
Recycling Plants
4-tert-octylphenol
26
100
20
8.8
43
14
15
18
23
35
47
Synthetic Turf Fields
Phenanthrene
40
100
0.58
0.71
120
0.035
0.069
0.29
0.89
1.4
3.1
Synthetic Turf Fields
Fluoranthene
40
98
0.16
0.11
73
0.046
0.068
0.12
0.23
0.33
0.46
Synthetic Turf Fields
Pyrene
40
98
0.29
0.21
73
0.083
0.15
0.22
0.40
0.62
0.89
Synthetic Turf Fields
Benzol ajpvrcnc
40
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Synthetic Turf Fields
Bcnzo|ghi Ipcrvlcnc
40
0
*
*
*
< LOD
< LOD
< LOD
< LOD
< LOD
< LOD
Synthetic Turf Fields
Suml5PAH
40
100
2.0
1.9
93
0.55
0.70
1.5
2.7
3.7
9.4
Synthetic Turf Fields
Bcn/.olhia/.olc
40
100
34
50
150
1.9
3.1
18
34
120
220
Synthetic Turf Fields
Dibutvl phthalate
40
100
0.14
0.41
290
-0.3
-0.15
0.073
0.38
0.63
1.5
Synthetic Turf Fields
Aniline
40
100
3.5
5.1
150
0.12
0.26
0.81
3.8
11
22
Synthetic Turf Fields
4-tert-octylphenol
40
98
5.8
5.5
94
0.50
1.2
5.1
9.1
14
21
a SVOC = Semivolatile organic compound; LOD = Limit of detection
b Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene.
*Values reported only when % >LOD is > 60%.
130
-------
Tem pe ratu re=6Cr C
Pyrene
Sum15PAH
Temperature=60''C
O)
B>
0.75
7.5'
0.50
0,25
2.5
0.00
0.0
5 10 15 20 25 30 35 40
Field ID
5 10 15 20 25 30 35 40
Field ID
Benzothiazole 4-tert-Octylphenol
T emperature=60°C Temperature=60l>C
200-
150-
Field ID Field ID
Figure 4-18. SVOC 60 °C emission factor results (ng/g/h) for pyrene, the sum of 15 PAHs,
benzothiazole, and 4-tert-octylphenol from tire crumb rubber infill composite samples collected
from each synthetic turf field. [SVOC = Semivolatile organic compound; Suml5PAH =
Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Bcn/.o|ghi|pcrylcnc. Benzo(k)fluoranthene, Chryscnc.
Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphtlialene, Phenanthrene, Pyrcnc|
Summary statistics are reported in Table 4-42 for 60 °C SVOC emission factor measurement results for
selected analytes measured by LC/TOFMS. These analyses were non-quantitative and are based on
chromatographic area counts. Six analytes were not reported; 2-mercaptobenzothiazole because it was
not measured in the emission samples, and diisononyl phthalate, diisodecyl phthalate, di(2-ethyhexyl)
adipate, phthalimide, and resorcinol because they were not distinguishable from chamber background
levels. Two remaining analytes, 2-hydroxybenzothiazole and N-cyclohexyl-N-methylcyclohexanamine,
were measurable in fewer than 60% of the samples. Cyclohexylamine and di-cyclohexylamine were
measurable in 100% and 93% of the samples, respectively.
131
-------
Benzothiazole was analyzed in both VOC and SVOC emissions testing. Higher maximum levels were
observed for the SVOC testing than for the VOC testing. The VOC upper benzothiazole emission rates
may be underestimated due to approaching the upper calibration limits during analysis. Differences may
also be a result of testing in two different chamber systems with different characteristics. The small
chambers used for VOC testing had greater chamber wall surface area than did the microchambers used
for SVOC testing, possibly resulting in wall adsorption effects in the VOC chamber tests.
Further comparisons of SVOC emission results at the two temperatures are illustrated and discussed in
section 4.8.2.
132
-------
Table 4-42. Summary Statistics for Select SVOC 60 °C Emission Samples Analyzed Non-quantitatively by LC/TOFMS for Tire Crumb Rubber
Samples Collected from Tire Recycling Plants and Tire Crumb Rubber Infill Collected from Synthetic Turf Fieldsa,b,c
Tire Crumb
Rubber
Sampling
Location
Chemical
n
%
> LOD
Mean
Area
Counts
Area Counts
Standard
Deviation
% Relative
Standard
Deviation
10th
Percentile
Area
Counts
25th
Percentile
Area
Counts
50"'
Percentile
Area
Counts
75th
Percentile
Area
Counts
90th
Percentile
Area
Counts
Maximum
Area
Counts
Recycling
Plants
N-cyclohexyl-N-
methylcyclohexanamine
27
96
1.9E+04
4.6E+04
250
-2.7E+01
2.5E+00
5.0E+02
1.1E+04
5.7E+04
1.9E+05
Recycling
Plants
2-hydroxybenzothiazole
27
78
5.0E+02
8.5E+02
170
< LOD
2.0E+02
2.4E+02
5.8E+02
1.2E+03
4.4E+03
Recycling
Plants
Cyclohexylamine
27
100
3.4E+05
2.8E+05
83
5.1E+04
1.5E+05
2.6E+05
4.4E+05
6.8E+05
1.2E+06
Recycling
Plants
Di-cyclohexylamine
27
100
7.3E+05
1.3E+06
180
6.8E+04
1.2E+05
2.3E+05
5.5E+05
3.7E+06
4.8E+06
Synthetic Turf
Fields
N-cyclohexyl-N-
methylcyclohexanamine
40
55
*
*
*
< LOD
< LOD
0.0E+00
6.2E+01
4.5E+02
3.2E+03
Synthetic Turf
Fields
2-hydroxybenzothiazole
40
40
*
*
*
< LOD
< LOD
< LOD
3.0E+02
7.9E+02
1.3E+03
Synthetic Turf
Fields
Cyclohexylamine
40
100
2.4E+04
6.3E+04
260
-8.4E+03
-5.6E+03
6.2E+02
2.5E+04
6.8E+04
3.3E+05
Synthetic Turf
Fields
Di-cyclohexylamine
40
93
1.2E+05
2.3E+05
180
-7.1E+02
-3.0E+02
7.6E+02
1.1E+05
4.8E+05
9.2E+05
a SVOC = Semivolatile organic compound; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry; LOD = Limit of detection
b No quantitative analysis was performed. Chromatographic area counts were reported. Chemical identities and retention times confirmed with purchased chemical standards.
0 Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
*Values reported only when % >LOD is > 60%.
133
-------
4.6.3 Comparison of Total Infill vs. Sand Corrected Results
Sand is sometimes used as a base layer or as a mixture with tire crumb rubber in synthetic turf fields.
Sand and other crustal materials may also be present at fields from windborne deposition and track-in by
field users. As stated previously, 16 of the 40 fields in this study had sand in the tire crumb rubber infill
samples. The average sand content among the infill samples collected from the surface of those sixteen
fields was 19.2% by weight (range 0.33 to 53.3%; Figure 4-3).
Chemical analysis measurement results included in this report have not been adjusted for sand fraction
in the synthetic turf field infill. This decision was based on two factors - a) the results not corrected for
sand are likely to be a better metric for exposure assessment, and b) the report would become
unreasonably lengthy if both uncorrected and corrected results were presented.
It is, however, useful to provide examples showing the potential differences between using results that
are not corrected for sand content versus results that are corrected for sand content. Results corrected for
sand content reflect the amount of target analyte per amount of tire crumb rubber in the infill. Table 4-43
shows summary statistic results for select metals using measurements not corrected and corrected for
infill sand content. Overall, the results for the mean and median statistics are similar, with differences
typically < 15%. The maximum sand corrected result for zinc was 26,000 mg/kg as compared to the
uncorrected result of 22,000 mg/kg. Figure 4-19 presents the uncorrected and corrected distribution of
results graphically for chromium, cobalt, lead, and zinc.
134
-------
Table 4-43. Summary Statistics for Select Metals Analyzed by ICP/MS in Tire Crumb Rubber Infill Samples Collected from Synthetic Turf Fields,
With and Without Correction for Infill Sand Content3
Correction Type
Chemical
n
%
> LOD
Mean
(m«/k«)
Standard
Deviation
(m«/k«)
% Relative
Standard
Deviation
10th
Percentile
(m«/k«)
25th
Percentile
(m«/k«)
50th
Percentile
(m«/k«)
75th
Percentile
(m«/k«)
90th
Percentile
(m«/k«)
Maximum
(mjj/kg)
Without sand correction
Arsenic
40
100
0.38
0.20
52
0.19
0.26
0.34
0.45
0.60
1.1
Without sand correction
Cadmium
40
100
0.95
0.68
72
0.49
0.57
0.70
1.1
1.7
4.2
Without sand correction
Chromium
40
100
1.6
0.84
51
0.97
1.2
1.6
1.9
2.7
3.7
Without sand correction
Cobalt
40
100
140
60
44
68
85
120
180
220
290
Without sand correction
Lead
40
100
24
26
110
9.3
11
14
25
55
160
Without sand correction
Zinc
40
100
15000
3000
20
11000
13000
14000
16000
19000
22000
With sand correction
Arsenic
40
100
0.43
0.25
59
0.19
0.28
0.34
0.60
0.76
1.3
Willi sand correction
Cadmium
40
100
1.1
0.74
71
0.53
0.61
0.78
1.3
1.9
4.2
Willi sand correction
Chromium
40
100
1.8
0.98
53
0.99
1.2
1.8
2.4
3.1
4.2
With sand correction
Cobalt
40
100
150
73
48
73
92
130
210
250
320
With sand correction
Lead
40
100
26
27
100
9.9
12
14
28
59
160
With sand correction
Zinc
40
100
16000
4000
24
13000
14000
15000
19000
23000
26000
11 ICP/MS = Inductively coupled plasma/mass spectrometry; LOD = Limit of detection
135
-------
Chromium
Cobalt
300
OJ200
100
Not Sand Corrected
Sand Corrected
Not Sand Corrected
Sand Corrected
Lead
Zinc
a> 80
25000
20000
Cl
E
15000
10000
Not Sand Corrected
Sand Corrected
Not Sand Corrected
Sand Corrected
Figure 4-19. Distributions of select metals analyzed by ICP/MS in tire crumb rubber infill samples
collected from synthetic turf fields, with and without correction for infill sand content. [ICP/MS =
Inductively coupled plasma/mass spectrometry]
Table 4-44 shows summary statistic results for select SVOCs from solvent extract GC/MS/MS analysis
using measurements not corrected and corrected for infill sand content. Overall, the results for the mean
values are typically < 10% different and the median values are typically < 20% different. The maximum
sand corrected result for the sum of 15 PAHs was 71 mg/kg as compared to the uncorrected result of 68
mg/kg. Figure 4-20 presents the uncorrected and corrected distribution of results graphically for pyrene,
benzothiazole, the sum of 15 PAHs, and 4-tert-octylphenol.
Differences between not corrected and corrected results are relatively small for the overall statistics in
this study because only 40% of the fields had sand in the infill and because the average sand fraction
was only 19%. However, for the field that had a sand fraction of 53%, the sand fraction corrected results
would be approximately 50% higher than the not corrected results. The impact in other studies that
might have more combined rubber + sand infill samples or higher fractions of sand in the infill could be
larger than the relatively modest impact for this study.
136
-------
Table 4-44. Summary Statistics for Select SVOCs Analyzed by GC/MS/MS in Solvent Extracts for Tire Crumb Rubber Infill Samples, With and
Without Correction for Infill Sand Content3
Correction
Type
Chcmicalb
n
%
> LOD
Mean
Standard
Deviation
(ms/ks)
% Relative
Standard
Deviation
10"'
Percentile
(mg/kg)
25th
Percentile
(mg/kg)
50th
Percentile
(m«/k«)
75th
Percentile
(m«/k«)
90th
Percentile
(mg/kg)
Maximum
(mg/kg)
Without sand
correction
Phenanthrene
40
100
2.3
2.6
110
0.26
0.44
1.1
3.3
6.1
10
Without sand
correction
Fluoranthene
40
100
4.5
2.6
57
2.0
2.4
3.9
6.5
8.1
10
Without sand
correction
Pyrene
40
100
12
6.2
49
4.2
7.0
13
17
21
25
Without sand
correction
Benzo[a]pyrene
40
100
0.78
0.52
66
0.38
0.43
0.62
0.91
1.4
3.0
Without sand
correction
Benzo [ghijperylene
40
100
1.3
0.64
49
0.47
0.64
1.4
1.8
2.0
2.8
Without sand
correction
Suml5PAH
40
100
29
15
51
13
17
27
38
49
68
Without sand
correction
Benzothiazole
40
100
11
13
120
1.1
1.8
7.0
14
31
54
Without sand
correction
Dibutyl phthalate
40
100
1.5
1.5
100
0.054
0.26
0.97
2.3
3.5
6.6
Without sand
correction
Bis(2-ethylhexyl)
phthalate
40
100
43
42
100
4.9
7.8
28
58
100
170
Without sand
correction
Aniline
40
100
0.67
0.53
79
0.16
0.27
0.57
0.96
1.2
2.4
Without sand
correction
4-tert-octylphenol
40
100
9.8
9.7
99
0.90
2.5
5.6
16
27
33
Without sand
correction
n-Hexadecane
40
100
0.94
1.3
130
0.079
0.10
0.26
1.3
2.6
5.4
Willi sand
correction
Phcnanlhrcnc
40
100
2.4
2.6
110
0.27
0.51
1.1
3.5
6.1
11
Willi sand
correction
Fluora.nl.hcne
40
100
4.8
2.5
52
2.0
2.7
4.6
6.6
8.3
10
With sand
correction
Pyrene
40
100
13
6.0
45
5.2
8.6
14
17
22
25
Willi sand
correction
Bcn/.o|a|pvrcnc
40
100
0.84
0.52
62
0.40
0.50
0.75
1.0
1.4
3.1
137
-------
Table 4-44 Continued
Correction
Type
Chemicalb
n
%
> LOD
Mean
(m«/k«)
Standard
Deviation
(m«/k«)
% Relative
Standard
Deviation
10th
Percentile
(m«/k«)
25th
Percentile
(m«/k«)
50th
Percentile
(m«/k«)
75th
Percentile
(m«/k«)
90th
Percentile
(m«/k«)
Maximum
(m«/k<0
Willi sand
correction
Bcn/.o|ghi|pcrvlcnc
40
100
1.4
0.64
46
0.51
0.87
1.6
1.9
2.1
2.8
Willi sand
correction
Suml5PAH
40
100
31
14
46
14
19
31
39
49
71
Willi sand
correction
Bcn/.olhia/.olc
40
100
11
13
120
1.3
2.0
7.0
14
31
54
Willi sand
correction
Dibulvl phlhalalc
40
100
1.6
1.6
100
0.061
0.29
1.0
2.4
3.9
6.6
Willi sand
correction
Bis(2-clhvlhcxyl)
phlhalalc
40
100
45
43
95
4.9
12
33
61
100
170
Willi sand
correction
Aniline
40
100
0.71
0.54
75
0.2
0.28
0.61
0.98
1.3
2.4
Willi sand
correction
4-lcrl-oclylphcnol
40
100
10
9.8
96
1.3
2.8
5.9
17
27
35
With sand
correction
n-Hcxadccanc
40
100
0.99
1.3
130
0.084
0.14
0.26
1.5
2.6
5.4
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry; LOD = Limit of detection
b Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
138
-------
Pyrene Sum15PAH
60-
20-
10-
Not Sand Corrected Sand Corrected Not Sand Corrected Sand Corrected
Benzothiazole 4-tert-Octylphenol
40-
Not Sand Corrected Sand Corrected Not Sand Corrected Sand Corrected
Figure 4-20. Distributions of select SVOCs in solvent extracts analyzed by GC/MS/MS from tire
crumb rubber infill samples collected from synthetic turf fields, with and without correction for
infill sand content. [SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography /tandem mass
spectrometry; Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene,
Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene,
Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
4.7 Comparison of Recycling Plants and Synthetic Turf Fields
Comparisons were performed of chemical measurements in tire crumb rubber samples from recycling
plants and tire crumb rubber infill collected from synthetic turf fields. These comparisons are designed
to provide information about differences in the presence and amounts of specific chemicals in 'fresh'
tire crumb material from recycling plants and the chemicals found in the synthetic turf field infill to help
determine:
• Whether there are chemicals appearing in synthetic turf field infill that may have sources other
than the tire rubber material, and
• Whether there are differences in chemical concentrations that may be attributable to losses or
removal of chemicals over time following installation at the fields.
139
-------
Comparison results are reported here for a subset of the chemical substances selected for highlighting,
with complete results for all target analytes shown in Appendix K. Results for the following analysis
types are included in this reporting sub-section:
• Metals analyzed by ICP/MS
• Metals analyzed by XRF
• SVOCs analyzed in solvent extracts by GC/MS/MS
• SVOCs non-quantitative analysis of solvent extracts by LC/TOFMS
• VOC emission factors from analysis by GC/TOFMS
• SVOC emission factors from analysis by GC/MS/MS
• SVOC non-quantitative emission results from analysis by LC/TOFMS
4.7.1 Direct Tire Crumb Rubber Measurements
4.7.1.1 Metals by ICP/MS and XRF
Table 4-45 shows results for mean concentrations of selected target metal analytes for recycling plants
and synthetic turf fields. Results are shown for both the ICP/MS analysis and the XRF analysis.
Examples of the measurement results and comparisons between recycling plant samples and synthetic
turf field samples are shown in Figure 4-21 for chromium, cobalt, lead, and zinc.
Examples of average measurement results for samples collected at recycling plants vs. synthetic turf
fields include lead (13 vs. 24 mg/kg), zinc (17,000 vs. 15,000 mg/kg), cobalt (190 vs. 140 mg/kg), and
chromium (1.8 vs. 1.6 mg/kg).
Table 4-45. Comparison of Selected Metal Analysis Results Between Tire Rubber Collected from
Tire Recycling Plants and Tire Crumb Rubber Infill Composite Samples from Synthetic Turf Fields3
Analysis1'
Analytc
Recycling
Plants
Mean
(nig/kg)
Recycling Plants
Standard
Deviation (nig/kg)
Synthetic
Turf Fields
Mean
(mg/kg)
Synthetic Turf
Fields Standard
Deviation
(mg/kg)
t-test
p-valuc'
ICP/MS Analysis
Arsenic
0.30
0.088
0.38
0.20
0.2261
ICP/MS Analysis
Cadmium
0.55
0.13
0.95
0.68
0.0002
ICP/MS Analysis
Chromium
1.8
0.70
1.6
0.84
NRd
ICP/MS Analysis
Cobalt
190
87
140
60
0.0056
ICP/MS Analysis
Lead
13
10
24
26
0.0060
ICP/MS Analysis
Zinc
17000
3500
15000
3000
0.0063
XRF Analysis
Chromium
15
4.0
14
2.9
0.0702
XRF Analysis
Cobalt
58
35
39
17
0.0208
XRF Analysis
Lead
35
8.6
36
22
0.4630
XRF Analysis
Zinc
39000
8800
33000
7100
0.0019
a Recycling Plants (n=27); Synthetic Turf Fields (n=40)
b ICP/MS = Inductively coupled plasma/mass spectrometry; XRF = X-ray fluorescence spectrometry
0 Statistical tests performed using ln-transformed measurement values.
b NR = Not Reported; one or more measurement results were <0, precluding ln-transformed testing for the complete data set.
140
-------
Chromium Cobalt
300
o>2
oi
100
Recycling Plants Fields Recycling Plants Fields
Lead Zinc
160
20000
120
12000
Recycling Plants Fields Recycling Plants Fields
Figure 4-21. Comparison of ICP/MS metal analysis results (mg/kg) between tire crumb
rubber collected from tire recycling plants and tire crumb rubber infill composite samples
from synthetic turf fields for chromium, cobalt, lead, and zinc. [ICP/MS = Inductively coupled
plasma/mass spectrometry]
The reason that lead was found, on average, at higher levels on fields compared to 'fresh' material
coming from recycling plants is not certain. Possible explanations include higher levels of lead in tires in
earlier years compared to tires being recycled in 2016 (although no literature citations could be
identified to support this), atmospheric deposition or transport from nearby soils, track-in by field users,
presence in and release from other synthetic turf field materials, or from trace contamination of chemical
treatments applied to the synthetic fields.
When considering these comparisons, it is important to recognize that recycling plant samples were
100% tire crumb rubber while, on average, the synthetic turf field infill contained 19% sand in this
study. As noted in section 4.6.3, the results for sand corrected synthetic turf field infill measurements
(perhaps a more direct comparison of tire crumb rubber) would have been about modestly higher (<
15%) on average.
4.7.1.2 SVOCs by GC/MS/MS
Table 4-46 shows results for mean concentrations of select target SVOCs analyzed by GC/MS/MS in
solvent extracts of samples collected from recycling plants and synthetic turf fields. Examples of mean
measurement results for samples collected at recycling plants versus synthetic turf fields include pyrene
(18 vs. 12 mg/kg), benzo[a]pyrene (0.74 vs. 0.78 mg/kg), benzothiazole (79 vs. 11 mg/kg), 4-tert-
octylphenol (30 vs. 9.8 mg/kg) and bis(2-ethylhexyl) phthalate (12 vs. 43 mg/kg).
141
-------
Many analytes on the more volatile end of the SVOC spectrum (e.g. aniline, hexadecane, benzothiazole,
phenanthrene) were found at higher levels, on average, in 'fresh' material from recycling plants
compared to levels found in synthetic turf fields. The likely explanation for the differences includes
volatilization from the rubber on the fields over time and, possibly, rain- or irrigation-driven leaching for
compounds with a higher degree of water solubility (e.g. aniline, benzothiazole, 4-tert-octylpheonol).
Water-based leaching has been demonstrated in the laboratory for several tire crumb rubber-associated
analytes, including some metals and several more water-soluble organic, but with less evidence for PAH
analytes (see Literature Review /Gaps Analysis report in Appendix C). Many of the less volatile SVOC
analytes, including the five and six-ring PAH chemicals, showed little to no difference between average
concentrations in recycling plant samples compared to synthetic turf field samples. However, it is also
possible that differences in concentrations between recycling plant and field infill samples could be a
result of differences in the original concentrations of chemicals in tires at different times. Longitudinal
studies at individual fields would be needed to confirm that weathering effects are primarily responsible
for these differences.
Examples of the measurement results and comparisons between recycling plant samples and synthetic
turf field samples are shown in Figures 4-22 through 4-23 for eight select SVOCs analyzed by
GC/MS/MS.
When considering these comparisons, it is important to recognize that recycling plant samples were
100% tire crumb rubber while, on average, the synthetic turf field infill contained 19% sand in this
study. As noted in section 4.6.3, the results for sand corrected synthetic turf field infill measurements
(perhaps a more direct comparison of tire crumb rubber) would have been modestly higher (< 10%) on
average.
Table 4-46. Comparison of Select SVOC GC/MS/MS Analysis Results Between Tire Rubber Solvent
Extracts for Samples Collected from Tire Recycling Plants and Synthetic Turf Fieldsa b
Analytc'
Recycling
Plants
Mean
(nig/kg)
Recycling
Plants Standard
Deviation
(mg/kg)
Synthetic
Turf Fields
Mean
(mg/kg)
Synthetic Turf
Fields Standard
Deviation
(mg/kg)
t-tcst
p-valucd
Phenanthrene
3.6
1.3
2.3
2.6
<0.0001
Fluoranthene
6.1
1.7
4.5
2.6
0.001
Pyrene
18
2.4
12
6.2
<0.0001
Benzo[a]pyrene
0.74
0.39
0.78
0.52
0.9556
Benzo [ghijperylene
1.3
0.59
1.3
0.64
0.5983
Suml5PAH
41
8.9
29
15
<0.0001
Benzothiazole
79
19
11
13
<0.0001
Dibutyl phthalate
0.68
0.44
1.5
1.5
0.6508
Bis(2-ethylhexyl) phthalate
12
14
43
42
<0.0001
Aniline
3.8
1.8
0.67
0.53
<0.0001
4-tert-octylphenol
30
6.2
9.8
9.7
<0.0001
n-Hexadecane
3.6
1.8
0.94
1.3
<0.0001
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry
b Recycling Plants (n=27); Synthetic Turf Fields (n=40)
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
d Statistical tests performed using ln-transformed measurement values.
142
-------
Phenarithrene Pyrene
10.0
7.5
CT>
o>
™ 5.0
2.5
0.0
25-
20-
10-
Recycling Plants Fields Recycling Plants Fields
Benzo(a)pyrene Sum15PAH
60-
20-
Recycling Plants Fields Recycling Plants Fields
Figure 4-22. Comparison of GC/MS/MS extract SVOC analysis results (nig/kg) between tire crumb
rubber collected from tire recycling plants and tire crumb rubber infill composite samples from
synthetic turf fields for phenanthrene, pyrene, benzo[a]pyrene, and the sum of 15 PAIIs. [SVOC =
Semivolatile organic compound; GC/MS/MS = Gas chromatography/ tandem mass spectrometry; Suml5PAH =
Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene. Benz[a]anthracene, Benzo [a]pyrene,
Benzo(b)fluoranthene, Benzo[ghijperylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene,
Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
143
-------
Benzothiazole 4-tert-Octylphenol
100
CD
Recycling Plants Fields Recycling Plants Fields
Bis(2-ethylhexyl) phthalate n-Hexadecane
150
o>
CD
TO
Recycling Plants Fields Recycling Plants Fields
Figure 4-23. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between
tire crumb rubber collected from tire recycling plants and tire crumb rubber infill composite
samples from synthetic turf fields for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl)
phthalate, and n-hexadecane. [SVOC = Semivolatile organic compound; GC/MS/MS = Gas
chromatography/tandem mass spectrometry]
Several phthalate chemicals were found, on average, at higher levels on fields compared to 'fresh'
material coming from recycling plants. Benz(a)anthracene and the unresolved mixture of indeno[l,2,3-
cdjpyrene and dibenzo[a,h]anthracene (DBA + ICDP) were also found at higher average levels in
synthetic field samples compared to recycling plant samples (Appendix K, Table K-3). Higher levels of
phthalates at fields could result from atmospheric deposition; track-in by field users or releases from
shoes, clothing or other personal products1; presence in and release from other synthetic turf field
materials; or from chemical treatments applied to fields.
4.7.1.3 SVOCs by LC/TOFMS
Seven additional target SVOCs were analyzed by LC/TOFMS following solvent exchange from the
extracts used for GC/MS/MS analyses. While these analyses were not performed quantitatively, valuable
non-quantitative results based on chromatographic peak areas were obtained. The three cyclohexylamine
compounds, 2-mercaptobenzothiazole, and 2-hydroxybenzothiazole followed the pattern of having
higher amounts in recycling plant tire crumb rubber versus synthetic field tire crumb rubber infill (Table
4-47). Diisononyl phthalate was present at somewhat higher levels in recycling plant samples compared
to synthetic turf field samples, while the reverse was true for diisodecyl phthalate. Table 4-47 shows
non-quantitative results for target SVOCs in solvent extracts analyzed by LC/TOFMS and Figure 4-24
provides examples of the measurement results and comparisons between recycling plant samples and
synthetic turf field samples for four select SVOCs.
144
-------
Table 4-47. Comparison of Select SVOC LC/TOFMS Non-quantitative Analysis Results Between Tire
Rubber Solvent Extracts for Samples Collected from Tire Recycling Plants and Synthetic Turf Fieldsa b
Analytec
Recycling
Plants
Mean Area
Counts
Recycling Plants
Area Counts
Standard
Deviation
Synthetic
Turf Fields
Mean Area
Counts
Synthetic Turf
Fields Area
Counts Standard
Deviation
t-test
p-value'1
2-mercaptobenzotliiazole
1.5E+04
1.8E+04
1.9E+03
3.4E+03
NR
2-hydroxybenzothiazole
3.1E+05
1.1E+05
1.0E+05
1.2E+05
NR
Cyclohexylamine
2.1E+06
1.4E+06
4.9E+05
7.9E+05
NR
D i -eye 1 o hexy la mi ne
1.4E+07
1.8E+07
9.0E+06
8.5E+06
0.5898
N-cy clohexyl-N -
methylcyclohexanamine
1.9E+06
1.7E+06
2.3E+05
3.0E+05
<0.0001
Diisononylphthalate
7.9E+04
1.6E+05
2.8E+04
9.4E+04
NR
Diisodecylphtlialate
5.5E+03
6.2E+03
4.8E+04
2.7E+05
NR
a SVOC = Semivolatile organic compound; LC/TOFMS = Liquid cliroinatography/time-of-flight mass spectrometry
b Recycling Plants (n=27); Synthetic Turf Fields (n=40)
0 Statistical tests performed using In-transformed measurement values.
dNR = Not Reported; one or more measurement results were <0. precluding In-transformed testing for the complete data set.
2-mercaptobenzothiazole
2-hydroxybenzothiazole
3e+06
4e+05
40000
3e+05
30000
2e+05
-------
4.7.2 Chemical Emissions from Tire Crumb Rubber
4.7.2.1 VOCs Emission Factors
Table 4-48 shows select target VOC mean emission factors at 25 °C and 60 °C for samples collected
from recycling plants and synthetic turf fields. Emission factors at 25 °C were higher for VOCs in
recycling plant samples versus synthetic turf fields. For example, mean benzothiazole emission factors
were 6 times higher, and the sum of BTEX compounds 5.5 times higher. Emission factors at 60 °C were
higher for VOCs in recycling plant samples versus synthetic turf fields. For example, mean methyl
isobutyl ketone emission factors were 3.3 time higher, benzothiazole 3.9 times higher, formaldehyde 2.5
times higher, and styrene 2.4 times higher. Examples of the measurement results and comparisons
between recycling plant samples and synthetic turf field samples are shown in Figure 4-25 for methyl
isobutyl ketone, benzothiazole, styrene, and formaldehyde for the 60 °C emissions results.
Many VOC analytes showed higher emission factors, on average, in 'fresh' material from recycling
plants compared to levels found in synthetic turf fields. The likely explanation for the difference is the
volatilization from the rubber on the fields over time; however, longitudinal studies at individual fields
would be needed to confirm this.
Table 4-48. Comparison of Select VOC Emission Factor Results Between Tire Rubber Collected from
Tire Recycling Plants and Tire Crumb Rubber Infill Composite Samples from Synthetic Turf Fieldsa'b,c
Emissions Test
Analytc'1
Recycling
Plants
Mean
(ng/g/h)
Recycling
Plants
Standard
Deviation
(ng/g/h)
Synthetic
Turf Fields
Mean
(ng/g/h)
Synthetic
Tu rf Fields
Standard
Deviation
(ng/g/h)
t-tcst
|)-valucc'r
Emission Factors at 25 °C
Benzothiazole
150
41
25
28
NR
Emission Factors at 25 °C
o-Xylene
0.21
0.20
0.032
0.090
NR
Emission Factors at 25 °C
SumBTEX
1.7
1.3
0.31
0.84
NR
Emission Factors at 60 °C
Formaldehyde
40
16
16
9.5
NR
Emission Factors at 60 °C
Melhvl isobutyl ketone
140
15
42
26
<0.0001
Emission Factors at 60 °C
Bcn/.olhia/.olc
220
8.3
56
39
<0.0001
Emission Factors at 60 °C
Styrene
1.1
0.58
0.45
0.41
NR
Emission Factors at 60 °C
Toluene
1.1
0.95
0.15
0.31
NR
Emission Factors at 60 °C
Elhvlbcnzcnc
-0.0055
0.26
-0.082
0.22
NR
Emission Factors at 60 °C
m/p-Xvlcnc
1.2
0.71
0.24
1.0
NR
Emission Factors at 60 °C
o-Xylcnc
-0.40
0.43
-0.35
0.66
NR
Emission Factors at 60 °C
SumBTEX
2.1
2.2
-0.085
2.2
NR
" VOC = Volatile organic compound
b Recycling Plants (n=27); Synthetic Turf Fields (n=38 for emissions tests at 25 °C; n=37 for emissions tests at 60 °C, with
exception of formaldehyde at n=40)
0 Several results are reported as negative values. This is a result of the subtraction of chamber background values from the
sample measurement results. Although this does not represent a physical reality, the negative results are retained as part of
the distribution of corrected results
d SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene results.
e Statistical tests performed using ln-transformed measurement values.
f NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
146
-------
Formaldehyde Benzothiazole
T emperature=60°C T emperature=60°C
60-
200
150
40-
o>
O)
O)
o>
C 100
Recycling Plants Fields Recycling Plants Fields
Methyl Isobutyl Ketone Styrene
T emperature=60"C T emperatu re=60°C
160
120
TO
a
0.5
0.0
Recycling Plants Fields Recycling Plants Fields
Figure 4-25. Comparison of VOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber collected from tire recycling plants and tire crumb rubber infill
composite samples from synthetic turf fields for formaldehyde, benzothiazole,
methyl isobutyl ketone, and styrene. [VOC = Volatile organic compound]
4.7.2.2 SVOC Emission Factors
Table 4-49 shows select target SVOC mean emission factors at 25 °C and 60 °C for samples collected
from recycling plants and synthetic turf fields. Emission factors at 25 °C were higher for some SVOCs
in recycling plant samples versus synthetic turf fields. For example, mean benzothiazole emission
factors were 9.8 times higher and aniline was 10 times higher. Emission factors at 60 °C were higher for
most SVOCs in recycling plant samples versus synthetic turf fields. For example, mean benzothiazole
emission factors were 15 time higher, aniline was 6.6 times higher, and 4-tert-octylphenol was 3 .4 times
higher.
Examples of the 60 °C emission measurement results and comparisons between recycling plant samples
and synthetic turf field samples are shown in Figure 4-26 for pyrene, the sum of 15 PAHs,
benzothiazole, and 4-tert-octylphenol.
147
-------
Table 4-49. Comparison of Select SVOC Emission Factor Results Between Tire Rubber Collected from Tire
Recycling Plants and Tire Crumb Rubber Infill Composite Samples from Synthetic Turf Fieldsa,b,c
Emissions Test
Analvtc'1
Recycling
Plants
Mean
(ng/g/h)
Recycling
Plants
Standard
Deviation
(ng/g/h)
Synthetic
Turf Fields
Mean
(ng/g/h)
Synthetic
Turf Fields
Standard
Deviation
(ng/g/h)
t-tcst
p-valuc1,1
Emission Factors at 25 °C
Phenanthrene
-0.0071
0.07
0.025
0.049
NR
Emission Factors at 25 °C
Suml5PAH
2.3
1.1
0.62
0.63
<0.0001
Emission Factors at 25 °C
Benzothiazole
41
26
4.2
5.2
NR
Emission Factors at 25 °C
Dibutyl phthalate
-0.021
0.67
-0.011
0.38
NR
Emission Factors at 25 °C
Aniline
3.5
2.0
0.34
0.45
NR
Emission Factors at 25 °C
4-tert-octylphenol
0.47
0.25
0.85
3.3
NR
Emission Factors at 60 °C
Phenanthrene
0.83
0.34
0.58
0.71
NR
Emission Factors at 60 °C
Fluoranthene
0.16
0.054
0.16
0.11
NR
Emission Factors at 60 °C
Pyrene
0.34
0.072
0.29
0.21
NR
Emission Factors at 60 °C
Suml5PAH
13
7.0
2.0
1.9
<0.0001
Emission Factors at 60 °C
Bcn/.othia/.olc
520
340
34
50
NR
Emission Factors at 60 °C
Dibutyl phthalate
0.21
0.72
0.14
0.41
NR
Emission Factors at 60 °C
Aniline
23
7.2
3.5
5.1
NR
Emission Factors at 60 °C
4-tcrt-oclylphcnol
20
8.8
5.8
5.5
NR
a SVOC = Semivolatile organic compound
b Recycling Plants (n=27 for emissions tests at 25 °C; n=26 for emissions tests at 60 °C); Synthetic Turf Fields (n=40)
0 Several results are reported as negative values. This is a result of the subtraction of chamber background values from the
sample measurement results. Although this does not represent a physical reality, the negative results are retained as part of
the distribution of corrected results.
d Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
e Statistical tests performed using ln-transformed measurement values.
f NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
148
-------
Pyrene
Temperature=60°C
0.75
; 0.50
O)
O)
c
0,25
0.00
Recycling Plants Fields
Sum15PAH
Temperature=60c'C
Recycling Plants Fields
Benzothiazole
T emperalure=60X
4-tert-Octylphenol
T ernperature=60 "C
900
300
Recycling Plants Fields Recycling Plants Fields
Figure 4-26. Comparison of SVOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber collected from tire recycling plants and tire crumb rubber infill
composite samples from synthetic turf fields for pyrene, the sum of 15 PAHs,
benzothiazole, and 4-tert-octylphenol. [SVOC = Semivolatile organic compound; Suml5PAH
= Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene. Antliracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Clirysene,
Dibenz[a,h] anthracene, Fluoranthene, Fluorene. Indeno(1.2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
4.8 Comparison of Emission Factors at 25 °C and 60 °C
Comparisons were performed for chemical emission measurements obtained at two different
temperatures for tire crumb rubber samples from recycling plants and tire crumb rubber infill collected
from synthetic turf fields. These comparisons are designed to provide information about differences in
emission factors that may be temperature dependent.
The 25 °C and 60 °C measurement results were previously reported as part of the summary statistics
sub-section (section 4.6.2). Temperature comparison results are reported here using graphical
149
-------
representations to illustrate important differences. Results for the following analysis types are included
in this reporting subsection:
• VOC 25 °C and 60 °C emission factors from analysis by GC/TOFMS
• SVOC 25 °C and 60 °C emission factors from analysis by GC/MS/MS
4.8.1 VOC Emission Factors
Differences in 25 °C and 60 °C emission factor distributions for formaldehyde, benzothiazole, methyl
isobutyl ketone, and styrene are shown in Figures 4-27 and 4-28 for tire crumb rubber samples collected
at tire recycling plants and tire crumb rubber infill samples collected at synthetic turf fields, respectively.
These target VOC analytes showed higher emission factors in emission experiments performed at 60 °C
than at 25 °C. The differences between the 60 °C and 25 °C emission factors were somewhat larger for
recycling plant samples than the differences for synthetic turf field samples. Except for benzothiazole, a
majority of the measurements at 25 °C were below the method detection limit or chamber background
levels. At 60 °C, a majority of measurements for the chemicals shown in Figures 4-27 and 4-28 were
above the method detection limit, but this was not the case for many of the other VOC target analytes.
Formaldehyde
Recycling Plants
60
5 40
D)
C
20
160
120
CD
o) 80
c
25 60
Temperature (°C)
Methyl Isobutyl Ketone
Recycling Plants
40
25 60
Temperature (°C)
Benzothiazole
Recycling Plants
200
120
25 60
Temperature (°C)
Recycling Plants
Styrene
05
25 60
Temperature (°C)
Figure 4-27. Comparison of VOC 25 °C and 60 °C emission factor results (ng/g/h)
for formaldehyde, benzothiazole, methyl isobutyl ketone, and styrene from tire
crime rubber collected from recycling plants. [VOC = Volatile organic compound]
150
-------
Fields
Formaldehyde
Benzothiazole
Fields
25 60
Temperature (°C)
Methyl Isobutyl Ketone
100
25 60
Temperature (°C)
Fields
120
]5i 60'
30-
Fields
25 60
Temperature (°C)
Styrene
g> 50
25 60
Temperature (°C)
Figure 4-28. Comparison of VOC 25 °C and 60 °C emission factor results (ng/g/h)
for formaldehyde, benzothiazole, methyl isobutyl ketone, and styrene from tire
crumb rubber infill collected from synthetic turf fields. [VOC = Volatile organic
compound]
Several compounds did not show appreciable differences in emissions for the two temperatures,
including most of the BTEX chemicals (benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene).
Distributions for SumBTEX 25 °C and 60 °C emission factors are shown in Figure 4-29 for recycling
pl ants and synthetic turf fields. The overall results are lower in the 60 °C tests as compared to the 25 °C
tests. In fact, a majority of the synthetic turf field measurements at 60 °C were below the average
chamber background measurements, resulting in slightly negative results following background
subtraction. It appeared that some VOCs were driven off the tire crumb during the 24-hour equilibration
period in the test chamber at 60 °C prior to chamber air sample collection. This may have implications
for understanding whether some chemicals may be found at the surface of tire crumb rubber particles,
perhaps from atmospheric absorption, versus chemicals intrinsic to the rubber material that would
continue to replenish what is lost at the particle surface. Based on the experimental results, it would
appear that chemicals like benzothiazole, methyl isobutyl ketone, and styrene are intrinsic to the tire
crumb rubber, while the BTEX chemicals are not, or at least not at substantial concentrations. More
experimental work is needed to better understand these emission dynamics.
151
-------
SumBTEX SumBTEX
Recycling Plants Fields
5,0
5.0
€ 2.5
-2*
O)
Ol
0.0
0.0
-2.5
-2.5
25 60 25 60
Temperature (°C) Temperature (°C)
Figure 4-29. Comparison of VOC 25 °C and 60 °C emission factor results (ng/g/h) for
SumBTEX from tire crumb rubber collected from recycling plants and tire crumb rubber
infill collected from synthetic turf fields. [VOC = Volatile organic compound; SumBTEX =
Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene results]
While the emissions testing performed in this study provides valuable information to help understand the
types and ranges of chemical emissions from tire crumb rubber, it is not clear how well the test methods
apply to the wide range of conditions at synthetic turf fields and whether the results can be successfully
applied to estimating real-world emissions to inform exposure assessment. Conditions such as short-
term changes in temperature (e.g., daily diurnal cycle), infill depth, effective ventilation rates at indoor
and outdoor fields, or other factors may affect emissions variability and net emissions at fields. More
directed experimental work at fields and in the laboratory would improve our understanding about how
well laboratory emissions testing can be used to model or predict exposures under different situations.
4.8.2 SVOC Emission Factors
Differences in 25 °C and 60 °C emission factor distributions for pyrene, the sum of 15 PAHs,
benzothiazole, and 4-tert-octylphenol are shown in Figures 4-30 and 4-31 for tire crumb rubber samples
collected at tire recycling plants and tire crumb rubber infill samples collected at synthetic turf fields,
respectively. These target SVOC analytes showed higher emission factors in emission experiments
performed at 60 °C than at 25 °C. The differences between the 60 °C and 25 °C emission factors were
somewhat larger for recycling plant samples than the differences for synthetic turf field samples. Many
of the emission factor measurements performed at 25 °C were below the method detection limit and/or
the chamber background. Most of the more volatile SVOCs showed similar results, with emission
factors at 60 °C exceeding those at 25 °C; however, the five- and six-ring PAH compounds were
generally below the method detection limits in both 60 °C and 25 °C emissions tests, consistent with
their very low vapor pressures.
152
-------
Recycling Plants
Pyrene
0.4
0.3
0.0
Sum15PAH
Recycling Plants
25 60
Temperature (°C)
Benzothiazole
Recycling Plants
25 60
Temperature (°C)
4-tert-Octyl phenol
Recycling Plants
900
oj6QQ-
o>
c
300-
30-
€20-
t
O)
c
10-
•
1
o-
25 60
Temperature (°C)
25 60
Temperature (®C)
Figure 4-30. Comparison of SVOC 25 °C and 60 °C emission factor results (ng/g/h) for
pyrene, the sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol from tire crumb
rubber collected from tire recycling plants. [SVOC = Semivolatile organic compound;
Sum 15 PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene,
Benz[a]antliracene, Benzo[a]pyrene, Benzo(b)fluoranthene. Benzolghi|perylene. Benzo(k)fluoranthene,
Clirysene, Dibenz[a,h]antliracene. Fluoranthene, Fluorene. Indeno(l,2,3-cd)pyrene, Naphtlialene,
Phenantlirene, Pyrene]
153
-------
Pyrene Sum15PAH
Fields Fields
0.75
7.5
^ 0.50
O)
0.25
2.5
0.00
0.0
25 60 25 60
Temperature <°C) Temperature (°C)
Benzothiazole 4-tert-Octylphenol
Fields Fields
200
150
25 60 25 60
Temperature (°C) Temperature ("C)
Figure 4-31. Comparison of SVOC 25 °C and 60 °C emission factor results (ng/g/h) for
pyrene, the sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol from tire crumb
rubber infill collected from synthetic turf fields. [SVOC = Semivolatile organic compound;
Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene,
Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene,
Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphtlialene,
Phenanthrene, Pyrene]
4.9 Heterogeneity/Homogeneity Assessments
An important gap exists for information about the variability of chemicals associated with tire crumb
rubber, both within synthetic turf fields and between fields in different locations. This is important for
several reasons. First, there are few U.S. studies with data available for assessing the range of tire crumb
rubber chemical concentrations across the country, and thus, the potential range of exposures people
may experience. Likewise, there are few data to assess differences in chemicals associated with tire
crumb rubber within a field. Within-field differences are important for understanding whether there
might be different exposure potentials across a given field and how best to collect samples to provide
representative results for a field.
This federal research study was designed to help fill gaps in knowledge about within-field and between-
field variability in chemicals associated with tire crumb rubber infill. Measurements were performed at
several different scales to assess measurement precision, homogeneity, and variability. The following
types of precision, homogeneity, and variability assessments have been performed and are reported in
this section. These assessments build in scale from analytical precision up to between-field variability:
154
-------
• For metal digestion and SVOC solvent extraction analyses, replicate injections of the digestate or
extract were performed to assess analytical precision.
• For VOC chamber emission experiments, duplicate samples were collected during a subset of
chamber experiments to assess emissions measurement precision.
• For metals digestion and SVOC extraction, duplicate portions of tire crumb rubber from the
same sample bottle were digested or extracted to assess homogeneity and variability of
chemicals associated with tire crumb rubber at a very small spatial scale.
• For SVOC and VOC chamber emissions experiments, duplicate portions of tire crumb rubber
from the same sample bottle were used in two entirely separate emissions experiments to assess
homogeneity and variability of chemicals associated with tire crumb rubber at a very small
spatial scale.
• For all analyses, tire crumb rubber infill samples collected at a subset of five fields, at different
locations on the field, were analyzed separately. This was done to assess within-field variability
of chemicals associated with tire crumb rubber at the spatial scale of a single field. This was also
accomplished for tire recycling plants through analysis of samples collected from three different
storage sacks at each plant.
• For all analyses, samples collected from multiple fields were used to examine between-field
differences in chemicals associated with tire crumb rubber infill. This was first done for the
subset of five fields that also had measurements for individual field locations, so that within- and
between-field relative variances could be calculated. In later sections, differences between
composite samples prepared from tire crumb rubber infill collected at 40 fields were examined
for several field characteristics (indoor vs. outdoor, field installation age, and U.S. census
region). Samples collected from tire recycling plants were also assessed for between- and within-
plant variability.
4.9.1 Measurement Precision and Sample Variability
Precision and variability measurement results were only reported if both members of the paired
measurements had measurement values exceeding zero. Measurement results near the method detection
limit were retained, but the precision of measurements near detection limits is often relatively poor and
may influence the overall results.
Table 4-50 reports both the analytical precision for replicate analyses of select metals in sample
digestates (replicate sample digest analysis) and homogeneity of those metals through analysis of
duplicate portions of tire crumb rubber sample removed from the same sample jar (duplicate tire crumb
sample analysis). A very high level of analytical precision was obtained, with average percent relative
standard deviations (%RSDs) for paired measurements < 2%. For duplicate portions of tire crumb
rubber from the same jar, average %RSDs for the paired measurements ranged from 4.8 to 32%.
Relatively high variability in lead levels from samples in the same collection bottle have been previously
reported; in this study, the lead %RSD was 25% for portions of tire crumb from the same jar, compared
to an analytical precision %RSD of 1.3%. Cobalt and zinc, two other metals associated with tire crumb
rubber, had %RSDs of 13% and 4.8%, respectively, in duplicate portions of tire crumb rubber from the
same sample jar.
155
-------
Table 4-50. Precision and Variability of Tire Crumb Rubber Sample Digestion Metals Measurements by
ICP/MSabc
Chemical
Replicate
Sample
Digest
Analysis
%RSD -
n
Replicate
Sample
Digest
Analysis
%RSD -
Mean
Replicate
Sample
Digest
Analysis
%RSD -
Minimum
Replicate
Sample
Digest
Analysis
%RSD -
Maximum
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
n
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
Mean
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
Minimum
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
Maximum
Arsenic
10
1.3
0.33
3.6
10
32
7.1
58
Cadmium
10
0.47
<0.1
1.4
10
20
4.4
37
Chromium
11
1.5
<0.1
5.8
8
15
1.5
33
Cobalt
11
0.72
0.12
2.3
9
13
2.4
29
Lead
10
1.3
0.32
3.1
10
25
0.20
96
Zinc
11
0.81
0.17
2.6
9
4.8
1.0
8.7
a ICP/MS = Inductively coupled plasma/mass spectrometry
b Replicate Sample Digest Analysis = replicate analyses of the same digest from a sample; %RSD is the percent relative
standard deviation between pairs of measurements.
0 Duplicate Tire Crumb Sample Analysis = Two different portions of tire crumb rubber samples from the same bottle
extracted and analyzed separately; %RSD is the percent relative standard deviation between pairs of measurements.
Table 4-51 reports both the analytical precision for replicate analyses of select SVOCs in sample
extracts (replicate sample extract analysis) and homogeneity of those SVOCs through analysis of
duplicate portions of tire crumb rubber sample removed from the same sample jar (duplicate tire crumb
sample analysis). Modest levels of analytical precision were obtained, with average percent relative
standard deviations (%RSDs) for paired measurements ranging from 11% to 34% for most analytes and
63% for 4-terty-octylphenol. These results may have been affected by a large maximum value, which in
turn may have been affected by results near the detection limit. For duplicate portions of tire crumb
rubber from the same jar, average %RSDs for the paired measurements ranged from 4.8 to 20%. All tire
crumb rubber samples produced for SVOC extraction analysis had duplicate measurements, so this
represents a robust assessment of small spatial scale homogeneity of SVOC chemicals associated with
tire crumb rubber.
Table 4-51. Precision and Variability of Tire Crumb Rubber Sample Solvent Extract SVOC Measurements by
GC/MS/MSa,b,c
Chemical
Replicate
Sample
Extract
Analysis
%RSD -
n
Replicate
Sample
Extract
Analysis
%RSD -
Mean
Replicate
Sample
Extract
Analysis
%RSD -
Minimum
Replicate
Sample
Extract
Analysis
%RSD -
Maximum
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
n
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
Mean
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
Minimum
Duplicate
Tire Crumb
Sample
Analysis
%RSD -
Maximum
Phenanthrene
7
13
3.3
25
101
4.8
0.12
40
Fluoranthene
7
15
0.96
49
101
4.9
<-0.1
50
Pyrene
7
32
4.3
120
101
5.1
<0.1
52
Benzo[a]pyrene
7
34
<0.1
63
101
20
0.35
64
Benzo [ghijperylene
7
34
16
47
100
17
0.18
130
Suml5PAH
7
21
0.8
110
101
5.1
<0.1
49
Benzothiazole
7
29
0.28
72
101
8.9
0.19
78
Dibutyl phthalate
7
13
<0.1
71
101
11
<0.1
71
156
-------
Table 4-51 Continued
Chemical
Replicate
Replicate
Replicate
Replicate
Duplicate
Duplicate
Duplicate
Duplicate
Sample
Sample
Sample
Sample
Tire
Tire
Tire
Tire
Extract
Extract
Extract
Extract
Crumb
Crumb
Crumb
Crumb
Analysis
Analysis
Analysis
Analysis
Sample
Sample
Sample
Sample
%RSD -
%RSD -
%RSD -
%RSD -
Analysis
Analysis
Analysis
Analysis
n
Mean
Minimum
Maximu
%RSD -
%RSD -
%RSD -
%RSD -
m
n
Mean
Minimum
Maximum
Bis(2-ethylhexyl)
7
31
0.62
82
100
14
<0.1
130
phthalate
Aniline
7
11
<0.1
27
101
7.8
0.13
37
4-tert-octylphenol
7
63
37
110
101
8.3
<0.1
41
n-Hexadecane
7
12
<0.1
51
96
10
<0.1
130
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry
b Replicate Sample Extract Analysis = Replicate analyses of the same extract from a sample; %RSD is the percent relative
standard deviation between pairs of measurements.
0 Duplicate Tire Crumb Sample Analysis = Two different portions of tire crumb rubber samples from the same bottle
extracted and analyzed separately; %RSD is the percent relative standard deviation between pairs of measurements.
The analytical precision for SVOC emission chamber testing is shown in Table 4-52. This table shows
the results for replicate injections of the extracts from PUF samples used to collect chamber air samples
during the emissions experiments. Average %RSDs ranged from < 0.1% to 31%.
Table 4-52. Precision of Replicate Extracts Analyses for Chamber Emission SVOC Measurements
by GC/MS/MSa'b
Chemical'
n
Replicate Emission
Sample Extract
Analysis %RSD -
Mean
Replicate Emission
Sample Extract
Analysis %RSD -
Minimum
Replicate Emission
Sample Extract
Analysis %RSD -
Maximum
Phenanthrene
3
0.43
0.013
1.2
Fluoranthene
2
0.12
<0.1
0.14
Pyrene
3
31
<0.1
94
Benzo[a]pyrene
1
1.3
1.3
1.3
Benzo [ghijperylene
2
8.2
5.9
10
Suml5PAH
4
0.91
<0.1
3.4
Benzothiazole
4
14
<0.1
42
Dibutyl phthalate
2
23
0.30
46
Aniline
4
2.7
<0.1
11
4-tert-octylphenol
3
<0.1
<0.1
0.25
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry
b Replicate Emission Sample Extract Analysis = Replicate analyses of the same extract from an emission sample;
%RSD is the percent relative standard deviation between pairs of measurements.
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
157
-------
The variability in SVOC chamber emissions measurement results is shown in Table 4-53 for six
repeated tests performed at 25 °C and six repeated tests performed at 60 °C tests. At 25 °C, average
%RSDs ranged from 28% to 130%. The relatively high variability at 25 °C may be a result, in part, of
the very low levels measured for most of the analytes. At 60 °C, average %RSDs ranged from 8.4% to
37%). The lower variability at 60 °C is likely a result of the higher levels measured for many of the
analytes.
Table 4-53. Variability of 25°C and 60°C Chamber Emission SVOC Measurements by GC/MS/MSa'b
Chemical'
25 °C
25 °C
25 °C
25 °C
60 °C
60 °C
60 °C
60 °C
Repeated
Repeated
Repeated
Repeated
Repeated
Repeated
Repeated
Repeated
Chamber
Chamber
Chamber
Chamber
Chamber
Chamber
Chamber
Chamber
Emission
Emission
Emission
Emission
Emission
Emission
Emission
Emission
Experiment
Experiment
Experiment
Experiment
Experiment
Experiment
Experiment
Experiment
%RSD -
%RSD -
%RSD -
%RSD -
%RSD -
%RSD -
%RSD -
%RSD -
n
Mean
Minimum
Maximum
n
Mean
Minimum
Maximum
Phenanthrene
3
50
18
76
5
8.4
0.23
16
Fluoranthene
4
29
22
42
5
21
7.4
35
Pyrene
3
30
8.7
54
5
18
8.0
30
Suml5PAH
6
35
1.4
84
6
30
9.7
72
Benzothiazole
5
28
10
48
5
37
15
65
Dibutyl phthalate
2
130
130
130
0
NR
NR
NR
Aniline
5
30
6.4
56
5
35
17
59
4-tert-octylphenol
5
74
24
130
5
18
11
27
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry; NR = Not reported
b Two completely different chamber experiments using different portions of tire crumb rubber samples from the same bottle;
%RSD is the percent relative standard deviation between pairs of measurements.
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
It was possible to collect duplicate samples using the small chambers during the VOC emissions
experiments, but that was not possible for the micro-chambers used for the SVOC emissions tests. Table
4-54 shows measurement precision results for duplicate sample collection of VOC emission samples and
variability results for the six repeated experiments performed at 25 °C. Average %>RSD values ranged
from 17%) to 61% for duplicate samples. Most of these measurements were at low concentrations;
benzothiazole was found at the highest concentrations and it had the lowest %>RSD (17%>). Average
%>RSD values ranged from 6.6%> to 140% for repeated emission experiments at 25 °C. As noted
previously, most of the selected analytes had measurements at low concentrations near the method
detection limits.
158
-------
Table 4-54. Precision and Variability of 25°C Chamber Emission VOC Measurements by GC/TOFMSa b c
Chemical'1
Duplicate
Chamber
Sample
%RSD-
n
Duplicate
Chamber
Sample
%RSD -
Mean
Duplicate
Chamber
Sample
%RSD -
Minimum
Duplicate
Chamber
Sample
%RSD -
Maximum
Repeated
Chamber
Emission
Experiment
%RSD-
n
Repeated
Chamber
Emission
Experiment
%RSD-
Mean
Repeated
Chamber
Emission
Experiment
%RSD-
IYIinimum
Repeated
Chamber
Emission
Experiment
%RSD-
IMaximum
Formaldehyde
6
51
13
91
2
7.8
5.6
10
Methyl isobutyl
ketone
17
45
1.1
130
4
10
2.1
21
Benzothiazole
18
17
0.79
91
4
6.8
1.4
18
1,3-Butadiene
1
65
65
65
1
82
82
82
Styrene
6
56
3.8
110
2
46
16
77
Benzene
6
67
22
86
1
140
140
140
Toluene
7
45
0.26
110
2
6.6
2.7
10
Ethylbenzene
8
59
0.10
140
2
67
36
98
m/p-Xylene
12
40
0.12
130
3
63
1.2
110
o-Xylene
12
28
0.22
110
3
68
12
110
SumBTEX
10
59
2.4
140
3
57
12
100
a VOC = Volatile organic compound; GC/TOFMS = Gas chromatography/time-of-flight mass spectrometry
b Duplicate Chamber Sample = Two samples collected from the chamber air at the same time during the same chamber
experiment; %RSD is the percent relative standard deviation between pairs of measurements.
0 Repeated Chamber Emission Experiment = Two completely different chamber experiments using different portions of tire
crumb rubber samples from the same bottle; %RSD is the percent relative standard deviation between pairs of measurements.
d SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene results
Table 4-55 shows measurement precision results for duplicate sample collection of VOC emission
samples and variability results for the six repeated experiments performed at 60 °C. Average %RSD
values ranged from 8.8% to 100% for duplicate samples. The precision improved for most of the
analytes found to be most strongly associated with tire crumb rubber in the 60 °C emission testing,
including benzothiazole, methyl isobutyl ketone, formaldehyde, and styrene. Most of the other
measurements were at low concentrations. Average %RSD values ranged from 3.4% to 65% for
repeated emission experiments at 60 °C. As noted previously, most of the selected analytes had
measurements at low concentrations near the method detection limits except for benzothiazole, methyl
isobutyl ketone, formaldehyde, and styrene. It is difficult to discern from these results how much of the
variability is due to measurement imprecision and how much is due to variability in the chemicals
associated with tire crumb rubber.
159
-------
Table 4-55. Precision and Variability of 60°C Chamber Emission VOC Measurements by GC/TOFMSa'b'c
Chemical1'
Duplicate
Chamber
Sample
%RSD-
ii
Duplicate
Chamber
Sample
%RSD -
Mean
Duplicate
Chamber
Sample
%RSD -
Minimum
Duplicate
Chamber
Sample
%RSD -
Maximum
Repeated
Chamber
Emission
Experiment
%RSD-
n
Repeated
Chamber
Emission
Experiment
%RSD-
Mean
Repeated
Chamber
Emission
Experiment
%RSD-
Minimum
Repeated
Chamber
Emission
Experiment
%RSD-
Maximum
Formaldehyde
10
11
0.34
31
5
9.7
1.2
30
Methyl isobutyl
ketone
17
17
0.55
85
4
29
7.1
87
Benzothiazole
17
8.8
0.47
43
4
3.4
2.0
7.4
1,3-Butadiene
3
100
76
130
1
11
11
11
Styrene
14
14
1.7
43
4
46
11
130
Benzene
8
60
1.4
130
1
11
11
11
Toluene
11
40
4.1
120
2
50
45
55
Ethylbenzene
4
51
33
89
0
NR
NR
NR
m/p-Xylene
9
16
0.58
30
2
65
55
75
o-Xylene
3
45
6.9
69
0
NR
NR
NR
SumBTEX
6
36
9.4
83
1
29
29
29
a VOC = Volatile organic compound; GC/TOFMS = Gas chromatography/time-of-flight mass spectrometry; NR = Not reported
b Duplicate Chamber Samples = Two samples collected from the chamber air at the same time during the same chamber
experiment; %RSD is the percent relative standard deviation between pairs of measurements.
0 Repeated Chamber Emission Experiment = Two completely different chamber experiments using different portions of tire
crumb rubber samples from the same bottle; %RSD is the percent relative standard deviation between pairs of measurements.
d SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene results
4.9.2 Variability Within and Between Recycling Plants or Synthetic Turf Fields
Within-field, between-field, within-recycling plant, and between-recycling plant assessments were
performed to further examine variability in chemicals associated with tire crumb rubber at larger spatial
scales. Tire crumb rubber infill samples collected at a subset of five fields, at different locations on the
field, were analyzed separately. This was done to assess within-field variability of chemicals associated
with tire crumb rubber at the spatial scale of a single field. This was also accomplished for tire recycling
plants through analysis of samples collected from three different storage sacks at each plant. Variance
analyses were performed to further assess within- and between-field differences for the five fields that
had individual location sample analyses performed. The same type of analysis was also performed for
the recycling plants. It is important to recognize that these assessments were based on modest sample
sizes.
4.9.2.1 Metals by ICP/MS Analysis
Table 4-56 shows average and individual measurement results for cobalt, lead, and zinc for tire crumb
rubber samples collected from three storage bags at nine tire recycling plants. %RSD values ranged from
9.1% to 56% for cobalt, 6.2% to 94% for lead, and 1.2% to 22% for zinc. The greatest variability was
consistently observed for Plant ID H, where the particle size analysis showed that there were
substantially different particle size fractions across the storage sacks that were sampled. Also, different
types of tires were reported for Sample 1 versus Samples 2 and 3 for Plant ID H.
160
-------
Table 4-56. Select ICP/MS Measurement Results for Individual Tire Crumb Rubber Samples Collected
at Nine Recycling Plants for Assessing Within-Plant Variabilitya b c
Chemical
Plant
ID
Mean
(m«/k«)
Standard
Deviation
(m«/k«)
% Relative
Standard
Deviation
Individual
Sample 1
Results (m^/kjj)
Individual
Sample 2
Results (mjj/kjj)
Individual
Sample 3
Results (mg/kjj)
Cobalt
A
113
12
10
120
100
120
Cobalt
B
157
21
13
140
180
150
Cobalt
C
217
55
25
160
270
220
Cobalt
D
105
13
13
120
98
96
Cobalt
E
233
29
12
200
250
250
Cobalt
F
313
113
36
280
440
220
Cobalt
G
103
50
48
160
76
72
Cobalt
H
220
125
57
360
120
180
Cobalt
I
233
38
16
260
250
190
Lead
A
16
7.0
44
13
11
24
Lead
B
14
3.7
27
9.7
14
17
Lead
C
11
1.8
17
13
9.7
10
Lead
D
9.5
1.4
15
8.2
11
9.4
Lead
E
8.9
0.55
6.2
8.4
8.9
9.5
Lead
F
6.9
1.4
20
7.7
7.7
5.3
Lead
G
15
6.1
40
22
10
14
Lead
H
30
28
93
9.7
61
18
Lead
I
10
0.23
2.3
9.6
10
10
Zinc
A
14000
1000
7.1
15000
13000
14000
Zinc
B
16000
1000
6.3
15000
17000
16000
Zinc
C
18667
577
.3.1
18000
19000
19000
Zinc
D
12667
577
4.6
12000
13000
13000
Zinc
E
20667
577
2.8
20000
21000
21000
Zinc
F
22000
2646
12
20000
25000
21000
Zinc
G
15333
1528
10
17000
15000
14000
Zinc
H
18667
3786
20
23000
16000
17000
Zinc
I
14667
1528
10
15000
16000
13000
a ICP/MS = Inductively coupled plasma/mass spectrometry
b Each sample collected from a different storage bag at the recycling plants.
0 Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two
significant figures.
Table 4-57 shows average and individual measurement results for cobalt, lead, and zinc for tire crumb
rubber samples collected from up to seven locations at five synthetic turf fields. %RSD values ranged
from 12% to 41% for cobalt, 14% to 110%> for lead, and 7.2% to 11% for zinc. The average
concentrations from individual location samples for cobalt and zinc were similar to those from the
composite sample that was prepared from the seven individual location samples. For lead, the average
results from the seven individual locations were substantially different than the composite sample
measurement for two fields (Field ID #20 and #29). There was substantial variability at individual
locations for lead at Field ID #20, and as noted earlier, and there was substantial within-sample bottle
variability for lead. The variability in measurement results for individual samples collected at tire
recycling plants and synthetic turf fields is shown graphically in Figure 4-32.
161
-------
Table 4-57. Select ICP/MS Measurement Results for Individual Location Tire Crumb Rubber Infill Samples Collected at Five Synthetic Turf Fields
for Assessing Within-Field Variabilitya'b'c
Chemical
Field
ID
Composite
Sample*1
(mg/kg)
Individual
Location
Mean
(mg/kg)
Individual
Location
% Relative
Standard
Deviation
Individual
Field
Sample
Location 1
Results
(mg/kg)
Individual
Field
Sample
Location 2
Results
(mg/kg)
Individual
Field
Sample
Location 3
Results
(mg/kg)
Individual
Field
Sample
Location 4
Results
(mg/kg)
Individual
Field
Sample
Location 5
Results
(mg/kg)
Individual
Field
Sample
Location 6
Results
(mg/kg)
Individual
Field
Sample
Location 7
Results
(mg/kg)
Cobalt
1
140
180
33
250
230
160
160
99
N/A
N/A
Cobalt
16
180
220
12
200
210
230
270
190
240
200
Cobalt
20
68
99
41
100
170
100
120
63
60
71
Cobalt
26
250
250
16
220
260
260
170
270
280
260
Cobalt
29
290
250
14
270
220
260
230
240
330
230
Lead
1
9.3
8.6
28
7.6
12
9.7
8.4
5.4
N/A
N/A
Lead
16
11
14
33
11
18
10
16
8.2
12
21
Lead
20
11
81
68
28
150
94
150
12
56
76
Lead
26
15
15
110
10
54
6.5
8.5
7.7
11
7.9
Lead
29
22
11
14
12
11
9.3
13
9.3
12
13
Zinc
1
19000
20000
11
21000
22000
21000
19000
17000
N/A
N/A
Zinc
16
18000
20000
8.6
17000
18000
18000
21000
21000
21000
20000
Zinc
20
13000
15000
8.6
14000
14000
13000
16000
15000
15000
16000
Zinc
26
21000
20000
7.2
22000
22000
22000
21000
19000
20000
18000
Zinc
29
19000
20000
9.3
21000
21000
24000
19000
18000
21000
19000
a ICP/MS = Inductively coupled plasma/mass spectrometry; N/A = The individual samples were depleted, no analysis performed.
b Refer to Figure 3-5 for a schematic representation of positions for samples collected from locations 1-7.
0 Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two significant figures.
d This is the measurement result for the analysis of the composite sample that was prepared from portions of tire crumb rubber infill from the seven locations on the
synthetic turf field.
162
-------
Cobalt
Cobalt
300'
en
1
200-
100'
R
rr
:
A & C D E F G H t
Recycling Plant ID
Lead
150-
100'
M'
JL
A6CDE FGH I
Rocyeftng Plant ID
Zinc
25000
*
¦?
¦
-i-
f
•
m
,
J
1
E
? jjHH
J
ABCOEFGHI
Recycling Plant IO
25«0
13KM
16 20 »
Field ID
Lead
Field ID
2mc
ra 20 26
Field id
Figure 4-32. Within-tire recycling plant variability (left side) and within-synthetic turf
field variability (right side) for ICP/MS metal analysis results (mg/kg) in tire crumb
rubber for cobalt, lead, and zinc. [ICP/MS = Inductively coupled plasma/mass spectrometry]
163
-------
The percent of total variance explained by within-recycling plant and between-recycling variances is
shown in Table 4-58 for select metals. For chromium and zinc, there is greater between-plant variability
than within-plant variability. For cobalt, the within- and between-plant variability is similar, and for
arsenic, cadmium, and lead, there is greater within-plant variance. The percent of total variance
explained by within-field and between-field variances is also shown in Table 4-58 for select metals. For
cobalt and zinc, there is greater between-field variability than within-field variability. For lead, the
within- and between-field variability is similar, and for arsenic, cadmium, and chromium, there is
greater within-field variance.
Table 4-58. Within- and Between-recycling Plant or Field Variability for Select Metal ICP/MS Analysis
for Tire Crumb Rubber Collected from Tire Recycling Plants and Tire Crumb Rubber Infill Collected
from Synthetic Turf Fieldsa
Tire Crumb Rubber
Analvtc
Number of
Number of
Bctwccn-
Within-
Sampling Location
Plants or
Samples per
Plant or Field
Plant or Field
Fields
Plant or Field
% Variance
% Variance
Recycling Plants
Arsenic
9
3
38
62
Recycling Plants
Cadmium
9
3
27
73
Recycling Plants
Chromium
9
3
61
39
Recycling Plants
Cobalt
9
3
46
54
Recycling Plants
Lead
9
3
8
92
Recycling Plants
Zinc
9
3
71
29
Synthetic Turf Fields
Arsenic
5
5
5
95
Synthetic Turf Fields
Cadmium
5
5
6
94
Synthetic Turf Fields
Chromium
5
5
13
87
Synthetic Turf Fields
Cobalt
5
5
65
35
Synthetic Turf Fields
Lead
5
5
48
52
Synthetic Turf Fields
Zinc
5
5
60
40
a ICP/MS = Inductively coupled plasma/mass spectrometry
4.9.2.2 SVOC Extracts by GC/MS/MS Analysis
Table 4-59 shows average and individual measurement results for pyrene, benzothiazole, and 4-tert-
octylphenol for tire crumb rubber samples collected from three storage bags at nine tire recycling plants.
%RSD values ranged from 1.5% to 12% for pyrene, 3.3% to 31% for benzothiazole, and 1.3% to 18%
for 4-tert-octylphenol, reflecting generally similar concentrations within recycling plants. The greatest
variability was consistently observed for Plant ID H, where the particle size analysis showed that there
were substantially different particle size fractions across the storage sacks that were sampled. Also,
different types of tires were reported for Sample 1 versus Samples 2 and 3 for Plant ID H.
164
-------
Table 4-59. Select SVOC Extraction GC/MS/MS Measurement Results for Individual Tire Crumb Rubber
Samples Collected at Nine Recycling Plants for Assessing Within-Plant Variabilitya b c
Chemical
Plant
ID
Mean
(m«/k«)
Standard
Deviation
(nig/kg)
% Relative
Standard
Deviation
Individual
Sample 1
Results
(m^/ks)
Individual
Sample 2
Results
(m«/k«)
Individual
Sample 3
Results
(m«/k«)
Pyrene
A
16
0.23
1.5
16
16
16
Pyrene
B
19
1.7
9.1
20
18
17
Pyrene
C
17
1.0
5.9
19
17
17
Pyrene
D
22
0.86
3.9
21
22
23
Pyrene
E
16
1.1
6.5
15
17
17
Pyrene
F
17
1.6
9.0
19
18
16
Pyrene
G
21
2.5
12
23
18
22
Pyrene
H
17
1.7
10
15
17
19
Pyrene
I
19
1.4
7.2
20
19
17
Benzothia/.olc
A
63
5.1
8.1
58
65
67
Benzothia/.olc
B
51
3.8
7.4
52
47
54
Benzothia/.olc
C
80
2.6
3.3
83
79
78
Bcn/.olhia/.olc
D
66
5.7
8.6
61
72
65
Bcn/.olhia/.olc
E
100
4.4
4.2
100
110
100
Bcnzolliia/olc
F
100
5.6
3.5
100
100
94
Benzothia/.olc
G
82
5.3
6.5
88
81
78
Benzothia/.olc
H
74
23
31
100
61
60
Benzothia/.olc
I
92
5.3
5.7
86
96
93
4-tert-octylphenol
A
30
0.38
1.3
30
29
30
4-tert-octylphenol
B
30
1.5
4.9
30
29
32
4-tert-octylphenol
C
26
1.2
4.5
27
27
25
4-tert-octylphenol
D
36
4.1
11
40
33
34
4-tert-octylphenol
E
24
0.45
1.9
23
24
24
4-tert-octylphenol
F
23
0.95
4.1
24
23
22
4-tert-octylphenol
G
29
2.0
6.9
27
30
30
4-tert-octylphenol
H
33
5.8
18
27
35
38
4-tert-octylphenol
I
42
3.0
7.0
46
40
41
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry
b Each sample collected from a different storage bag at the recycling plants.
0 Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two
significant figures.
Table 4-60 shows average and individual measurement results for pyrene, benzo[a]pyrene,
benzothiazole, and 4-tert-octylphenol for tire crumb rubber samples collected from seven locations at
five synthetic turf fields. %RSD values ranged from 2.3% to 11% for pyrene, 16% to 31% for
benzo[a]pyrene, 12 to 57% for benzothiazole, and 13% to 39% for 4-tert-octylphenol. The average
concentrations from individual location samples for most analytes and most fields were similar to those
from the composite sample that was prepared from the seven individual location samples. The
variability in measurement results for individual samples collected at tire recycling plants and synthetic
turf fields is shown graphically for select chemicals in Figures 4-33 and 4-34.
165
-------
Table 4-60. Select SVOC Extraction GC/MS/MS Measurement Results for Individual Location Tire Crumb Rubber Infill Samples Collected at Five
Synthetic Turf Fields for Assessing Within-Field Variabilitya'b'c
Chemical
Field
ID
Composite
Sample'1
(mg/kg)
Individual
Location
Mean
(mg/kg)
Individual
Location
% Relative
Standard
Deviation
Individual
Field
Sample
Location 1
Results
(mg/kg)
Individual
Field
Sample
Location 2
Results
(mg/kg)
Individual
Field
Sample
Location 3
Results
(mg/kg)
Individual
Field
Sample
Location 4
Results
(mg/kg)
Individual
Field
Sample
Location 5
Results
(mg/kg)
Individual
Field
Sample
Location 6
Results
(mg/kg)
Individual
Field
Sample
Location 7
Results
(mg/kg)
Pyrene
1
7.3
7.3
5.3
8.0
7.0
7.2
7.7
7.4
6.9
7.2
Pyrene
16
14
12
11
14
14
13
12
10
13
11
Pyrene
20
22
22
3.5
22
21
21
23
21
21
22
Pyrene
26
8.9
8.3
3.0
8.3
8.2
8.5
8.7
8.1
8.0
8.2
Pyrene
29
16
17
2.3
17
17
16
17
17
17
16
Benzo[a]pyrcnc
1
0.37
0.34
31
0.44
0.22
0.41
0.49
0.27
0.27
0.28
Ben/o |a]pv re ne
16
0.41
0.49
18
0.46
0.55
0.51
0.46
0.32
0.58
0.57
Bcn/.o|a]pyrcnc
20
0.83
1.0
17
0.97
0.75
0.93
0.90
1.3
1.1
1.1
Benzo|a]pvrcnc
26
0.42
0.48
16
0.52
0.42
0.50
0.59
0.53
0.36
0.44
Benzo[a]pyrcnc
29
0.51
0.68
21
0.89
0.60
0.84
0.55
0.74
0.61
0.52
Benzothiazole
1
1.8
1.5
12
1.6
1.6
1.7
1.3
1.4
1.2
1.5
Benzothiazole
16
23
14
57
26
20
20
9.6
6.0
8.4
7.1
Benzothiazole
20
7.3
6.5
16
8.1
7.1
7.1
5.0
6.1
5.5
6.7
Benzothiazole
26
3.0
2.3
30
3.2
2.0
1.4
2.9
2.9
1.8
1.9
Benzothiazole
29
40
37
14
31
40
33
41
46
36
34
4-tert-octylphcnol
1
1.8
2.3
24
1.9
1.5
2.3
3.1
2.5
2.4
2.3
4-tert-octylphcnol
16
4.5
6.3
39
6.6
5.5
3.6
9.7
4.2
9.3
4.9
4-tert-octylphcnol
20
30
27
15
34
30
29
24
24
24
25
4-lcrl-oclylphcnol
26
3.9
4.3
13
5.3
4.1
4.6
4.0
4.4
3.9
3.6
4-lerl-oclylphcnol
29
21
15
27
14
14
13
8.4
16
19
21
11 SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry
b Refer to Figure 3-5 for a schematic representation of positions for samples collected from locations 1-7.
0 Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two significant figures.
d This is the measurement result for the analysis of the composite sample that was prepared from portions of tire crumb rubber infill from the seven locations on the
synthetic turf field.
166
-------
Pft&narrtfvrene
Phenamfirene
R*cyc*ng Plant to
Pyrene
F«d in
Rfrcyc««^g Piant ID
F lew 10
BcnzGKaJpyre-rkG
Beriroi;aipyref«
FWfcJIO
t i f
Recyc*ng Pi®nt 10
Sum15PAH
$um15PAH
I
Recycle Plant 10
FieWlD
Figure 4-33. Within-tire recycling plant variability (left side) and within-synthetic turf field variability (right
side) for GC'/MS/MS extract SVOC analysis results (nig/kg) in tire crumb rubber for phenanthrene, pyrene,
benzo[a]pyrene, and the sum of 15 PAHs. |GC'/MS/MS = Gas chromatography/ tandem mass spectrometry; SVOC =
Semivolatile organic compound; Suml5PAH = Sum of 15 of the 16 EPA 'priority" PAHs, including Acenaphthvlene, Anthracene.
Benz|a]anthracene. Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi|peiylene, Benzo(k)fluoranthene, Chrvsene,
Dibenz|a.h|ant 11raccue. Fluoranthene, Fluorene, Indeno(l,2,3-cd)pvrene, Naphthalene, Phenanthrene, Pyrene]
167
-------
BenzolhiazoSe
Beruottuazole
t
f
Recyctoig Plant ID
~¦lert-Qctylptwnd
Field HO
-Mert-Qctyl phenol
A » C 0 £ f i
Recycinp Plarl ID
Bis<2-e(hylhexy1) phlhalale
Field ID
Bis(2~ettiyttie*y!) phthafate
BCD
RoOKrtJ PUT* ID
RM
r^H6*a<3eCane
Recycang P«art C
F«M ID
Figure 4-34. Within-tire recycling plant variability (left side) and within-synthetic turf field
variability (right side) for GC/MS/MS extract SVOC analysis results (mg/kg) in tire crumb
rubber for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl) phthalate, and n-hexadecane.
[GC/MS/MS = Gas chromatography /tandem mass spectrometry; SVOC = Semivolatile organic compound]
168
-------
The percent of total variance explained by within-recycling plant and between-recycling plant variances
is shown in Table 4-61 for select SVOCs. Most of the chemicals had greater between-plant variability
than within-plant variability except for phenanthrene, benzo[a]pyrene, and bis(2-ethylhexyl) phthalate.
The percent of total variance explained by within-field and between-field variances is also shown in
Table 4-61 for select SVOCs. The amount of variability explained by between-field differences was
much greater than the amount explained by within-field differences for all SVOC chemicals.
Table 4-61. Within- and Between-recycling Plant or Field Variability for Select SVOC Extraction GC/MS/MS
Analysis Results for Tire Crumb Rubber Collected from Tire Recycling Plants and Tire Crumb Rubber Infill
Collected from Synthetic Turf Fields3
Tire Crumb Rubber
Sampling Location
Analvtcb
Number
of Plants
or Fields
Number of
Samples per
Plant or Field
Between
Plant or Field
% Variance
Within
Plant or Field
% Variance
Recycling Plants
Phenanthrene
9
3
37
63
Recycling Plants
Fluoranthene
9
3
64
36
Recycling Plants
Pyrene
9
3
60
40
Recycling Plants
Benzo[a]pyrene
9
3
39
61
Recycling Plants
Benzo [ghijperylene
9
3
59
41
Recycling Plants
Suml5PAH
9
3
54
46
Recycling Plants
Benzothiazole
9
3
76
24
Recycling Plants
Dibutyl phthalate
9
3
91
9
Recycling Plants
Bis(2-ethylhexyl) phthalate
9
3
17
83
Recycling Plants
Aniline
9
3
84
16
Recycling Plants
4-tert-octylphenol
9
3
80
20
Recycling Plants
n-Hexadecane
9
3
77
23
Synthetic Turf Fields
Phenanthrene
5
7
98
2
Synthetic Turf Fields
Fluoranthene
5
7
95
5
Synthetic Turf Fields
Pyrene
5
7
98
2
Synthetic Turf Fields
Bcn/.o|a|pyrcnc
5
7
77
23
Synthetic Turf Fields
Bcn/.o| ghi|pcrvlcnc
5
7
83
17
Synthetic Turf Fields
Suml5PAH
5
7
99
1
Synthetic Turf Fields
Bcn/.othia/.olc
5
7
90
10
Synthetic Turf Fields
Dibutyl phthalate
5
7
88
12
Synthetic Turf Fields
Bis(2-cthvlhc.\yl) phthalate
5
7
100
0
Synthetic Turf Fields
Aniline
5
7
82
18
Synthetic Turf Fields
4-tcrt-oclylphcnol
5
7
91
9
Synthetic Turf Fields
n-Hcxadccanc
5
7
98
2
a GC/MS/MS = Gas chromatography/ tandem mass spectrometry; SVOC = Semivolatile organic compound
b Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo [a] pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
169
-------
4.9.2.3 VOC Emission Factors Analysis
Table 4-62 shows average and individual VOC 25 °C emission measurement results for methyl isobutyl
ketone, benzothiazole, and styrene for tire crumb rubber samples collected from three storage bags at
nine tire recycling plants. %RSD values ranged from 2.8% to 87% for benzothiazole. Methyl isobutyl
ketone and styrene emission factors were low at this temperature, and there was considerable variability,
as evidenced by the high %RSD. The results for the second individual sample at Plant ID D were very
low compared to other measurements. It is not clear whether this represents a true difference, or a
measurement error for that sample.
Table 4-62. Select VOC 25 °C Emission Factor Measurement Results for Individual Tire Crumb Rubber
Samples Collected at Nine Recycling Plants for Assessing Within-Plant Variabilitya b
Chemical
Plant
ID
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
Individual
Sample 1
Results
(ng/g/h)
Individual
Sample 2
Results
(ng/g/h)
Individual
Sample 3
Results
(ng/g/h)
Methyl isobutyl ketone
A
21
11
51
17
13
33
Methyl isobutyl ketone
B
25
5.0
20
31
24
21
Methyl isobutyl ketone
C
13
7.4
58
20
12
5.7
Methyl isobutyl ketone
D
15
13
88
26
0.28
19
Methyl isobutyl ketone
E
48
29
61
56
72
15
Methyl isobutyl ketone
F
33
18
54
36
13
48
Methyl isobutyl ketone
G
19
4.6
24
21
14
23
Methyl isobutyl ketone
H
16
9.4
60
24
5.6
18
Methyl isobutyl ketone
I
31
11
35
22
43
28
Benzothia/.olc
A
140
37
26
99
170
160
Benzothia/.olc
B
140
3.9
2.8
140
140
140
Bcn/.olhia/.olc
C
150
54
36
180
180
87
Benzothia/.olc
D
92
80
87
130
0.045
150
Bcn/.olhia/.olc
E
170
17
9.9
180
180
150
Bcn/.olhia/.olc
F
170
5.1
3.0
170
170
160
Benzothia/.olc
G
130
9.3
7.0
130
120
140
Benzothia/.olc
H
140
46
32
180
150
93
Benzothia/.olc
I
180
2.1
1.2
180
180
180
Styrene
A
0.26
0.14
55
0.41
0.12
0.26
Styrene
B
0.12
0.081
70
0.21
0.068
0.071
Styrene
C
0.33
0.26
79
0.16
0.20
0.63
Styrene
D
0.32
0.33
100
0.70
0.067
0.20
Styrene
E
0.29
0.17
59
0.23
0.16
0.49
Styrene
F
0.31
0.14
44
0.17
0.31
0.44
Styrene
G
0.65
0.27
41
0.87
0.72
0.35
Styrene
H
0.17
0.032
19
0.13
0.19
0.19
Styrene
I
0.33
0.036
11
0.35
0.29
0.36
a VOC = Volatile organic compound
b Each sample collected from a different storage bag at the recycling plants.
170
-------
Table 4-63 shows average and individual VOC 25 °C emission measurement results for benzothiazole
for tire crumb rubber infill samples collected from three locations at five synthetic turf fields. %RSD
values ranged from 3% to 51%. No other chemicals are reported in this table because most other
chemicals had one or more results that were not greater than the chamber background.
Table 4-63. Select VOC 25 °C Emission Factor Measurement Results for Individual Location Tire Crumb
Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing Within-Field Variabilitya b
Chemical
Field
ID
Composite
Sample'
(ng/g/h)
Mean
(ng/g/h)
% Relative
Standard
Deviation
Individual
Field Sample
Location 1
Results
(ng/g/h)
Individual
Field Sample
Location 2
Results
(ng/g/h)
Individual
Field Sample
Location 3
Results
(ng/g/h)
Benzothiazole
1
1.9
1.5
51
1.5
2.2
0.7
Benzothiazole
16
33
22
21
17
26
24
Benzothiazole
20
25
19
37
11
22
24
Benzothiazole
26
1.2
3.5
40
4.5
1.9
4.1
Benzothiazole
29
110
86
3.0
85
84
89
11 VOC = Volatile organic compound
b Refer to Figure 3 -5 for a schematic representation of positions for samples collected from locations 1 - 3.
0 This is the measurement result for the analysis of the composite sample that was prepared from portions of tire crumb rubber
infill from seven locations on the synthetic turf field.
Table 4-64 shows average and individual VOC 60 °C emission measurement results for formaldehyde,
methyl isobutyl ketone, and benzothiazole for tire crumb rubber samples collected from three storage
bags at nine tire recycling plants. %RSD values ranged from 5.2 to 30% for formaldehyde, 1.5% to 18%
for methyl isobutyl ketone, and 1.2% to 6.2% for benzothiazole.
Table 4-64. Select VOC 60 °C Emission Factor Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-plant Variabilitya'b
Chemical
Plant
ID
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
Individual
Sample 1
Results
(ng/g/h)
Individual
Sample 2
Results
(ng/g/h)
Individual
Sample 3
Results
(ng/g/h)
Formaldehyde
A
44
7.3
16
49
36
48
Formaldehyde
B
42
6.1
14
49
40
37
Formaldehyde
C
21
1.1
5.2
23
20
21
Formaldehyde
D
43
2.4
5.6
46
44
41
Formaldehyde
E
20
4.0
19
16
24
20
Formaldehyde
F
26
5.1
20
31
21
24
Formaldehyde
G
45
8.4
19
44
54
37
Formaldehyde
H
51
15
30
62
33
56
Formaldehyde
I
66
8.9
13
56
69
73
Methyl isobutyl ketone
A
130
13
11
140
110
130
Methyl isobutyl ketone
B
140
8.4
6.0
150
130
150
Methyl isobutyl ketone
C
130
7.3
5.7
140
120
130
171
-------
Table 4-64 Continued
Chemical
Plant
ID
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
Individual
Sample 1
Results
(ng/g/h)
Individual
Sample 2
Results
(ng/g/h)
Individual
Sample 3
Results
(ng/g/h)
Methyl isobutyl ketone
D
120
11
8.9
130
110
120
Melhvl isobutyl ketone
E
160
3.0
1.9
150
160
160
Melhvl isobutyl ketone
F
150
11
7.2
160
140
150
Methyl isobutyl ketone
G
130
2.0
1.5
130
130
130
Melhvl isobutyl ketone
H
120
22
18
150
100
120
Melhvl isobutyl ketone
I
140
6.4
4.6
130
150
140
Benzothiazole
A
230
14
6.2
240
220
240
Benzothiazole
B
220
7.0
3.2
220
220
230
Benzothiazole
C
220
5.2
2.4
230
220
220
Benzothiazole
D
220
5.3
2.4
220
220
210
Benzothiazole
E
220
11
4.7
210
220
230
Benzothiazole
F
230
2.7
1.2
230
220
230
Benzothiazole
G
230
5.6
2.5
230
230
220
Benzothiazole
H
220
10
4.8
230
210
210
Benzothiazole
I
220
4.1
1.8
230
220
230
a VOC = Volatile organic compound
b Each sample collected from a different storage bag at the recycling plants.
Table 4-65 shows average and individual VOC 60 °C emission measurement results for formaldehyde,
methyl isobutyl ketone, and benzothiazole for tire crumb rubber infill samples collected from three
locations at five synthetic turf fields. %RSD values ranged from 2 to 67% for formaldehyde, 4.8% to
16% for methyl isobutyl ketone, and 5.7% to 21% for benzothiazole. These results suggest low to
modest variability for these chemicals in emissions at 60 °C for samples collected at multiple locations
on a synthetic turf field.
Table 4-65. Select VOC 60 °C Emission Factor Measurement Results for Individual Location Tire Crumb
Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing Within-field Variabilitya b
Chemical
Field
ID
Composite
Sample'
(ng/g/h)
Mean
(ng/g/h)
% Relative
Standard
Deviation
Individual
Field Sample
Location 1
Results
(ng/g/h)
Individual
Field Sample
Location 2
Results
(ng/g/h)
Individual
Field Sample
Location 3
Results
(ng/g/h)
Formaldehyde
1
11
12
12
13
10
13
Formaldehyde
16
9.4
11
17
13
9.0
12
Formaldehyde
20
23
21
2.0
22
21
21
Formaldehyde
26
17
8.7
10
7.9
9.7
8.6
Formaldehyde
29
20
15
67
3.4
22
20
Melhvl isobutyl ketone
1
34
32
14
32
27
36
Melhvl isobulvl ketone
16
56
64
16
75
61
55
Methyl isobulvl ketone
20
57
61
7.9
65
56
62
Methyl isobulvl ketone
26
35
33
4.8
34
31
34
Methyl isobulvl ketone
29
96
89
9.7
87
99
82
172
-------
Table 4-65 Continued
Chemical
Field
ID
Composite
Samp lee
(ng/g/h)
Mean
(ng/g/h)
% Relative
Standard
Deviation
Individual
Field Sample
Location 1
Results
(ng/g/h)
Individual
Field Sample
Location 2
Results
(ng/g/h)
Individual
Field Sample
Location 3
Results
(ng/g/h)
Benzothiazole
1
18
19
21
19
16
24
Benzothiazole
16
87
86
5.7
92
83
84
Benzothiazole
20
82
87
5.7
91
82
89
Benzothiazole
26
30
32
16
37
27
33
Benzothiazole
29
110
110
1.4
110
110
110
a VOC = Volatile organic compound
b Refer to Figure 3 -5 for a schematic representation of positions for samples collected from locations 1 - 3.
0 This is the measurement result for the analysis of the composite sample that was prepared from portions of tire crumb rubber
infill from the seven locations on the synthetic turf field.
The variability in 60 °C emission measurement results for individual samples collected at tire recycling
plants and synthetic turf fields is shown graphically for selected chemicals in Figure 4-35.
The percent of total variance explained by within-recycling plant and between-recycling plant variances
is shown in Table 4-66 for select VOC 25 °C emission factor measurements. All chemicals had greater
within-plant variability than between-plant variability. The percent of total variance explained by
within-field and between-field variances is also shown in Table 4-66 for select VOC 25 °C emission
factor measurements. The amount of variability explained by between-field differences was much
greater than the amount explained by within-field differences for benzothiazole. The reverse was
observed for o-xylene and the sum of BTEX compounds.
The percent of total variance explained by within-recycling plant and between-recycling plant variances
is shown in Table 4-67 for select VOC 60 °C emission factor measurements. Some chemicals had
greater within-plant variability than between-plant variability, while the reverse was observed for other
chemicals. The percent of total variance explained by within-field and between-field variances is also
shown in Table 4-67 for select VOC 60 °C emission factor measurements. The amount of variability
explained by between-field differences was much greater than the amount explained by within-field
differences for all chemicals except formaldehyde and toluene.
173
-------
Formaldehyde
Temperature=60°C
Formaldehyde
Temperature=60°C
ABCDEFGH I
Recycling Plant ID
Benzothiazole
Temperature-SOX
16 20 26
Field ID
Benzothiazole
Temperalure=60"C
250
200
150
c
100
SO
A9CDEFGH I
Recycling Plant ID
Methyl Isobutyl Ketone
Temperature=60°C
1 16 20 26
Field ID
Methyl Isobutyl Ketone
Temperalure=60°C
160-
120-
80-
40-
ABCDEFGH
Recycling Plan! ID
16 20 26
Field ID
200-
100-
150-
50-
29
29
Figure 4-35. Within-tire recycling plant variability (left side) and within-synthetic turf field
variability (right side) variability for VOC emission factor 60 °C analysis results (ng/g/h) in
tire crumb rubber for formaldehyde, benzothiazole, and methyl isobutyl ketone. [VOC =
Volatile organic compound]
174
-------
Table 4-66. Within- and Between-recycling Plant or Field Variability for Select VOC 25 °C Emission Factor
Analysis Results for Tire Crumb Rubber Collected from Tire Recycling Plants and Tire Crumb Rubber
Infill Collected from Synthetic Turf Fields
Tire Crumb Rubber
Analvtc"
Number of
Number of
Between
Within
Sampling Location
Plants or
Samples per
Plant or Field
Plant or Field
Fields
Plant or Field
% Variance
% Variance
Recycling Plants
Methyl isobutyl ketone
9
3
19
81
Recycling Plants
Benzothiazole
9
3
8
92
Recycling Plants
Styrene
9
3
16
84
Recycling Plants
Toluene
9
3
43
57
Recycling Plants
m/p-Xylene
9
3
29
71
Recycling Plants
o-Xylene
9
3
26
74
Recycling Plants
SumBTEX
9
3
36
64
Synthetic Turf Fields
Benzothiazole
5
3
98
2
Synthetic Turf Fields
o-Xylenc
5
3
24
76
Synthetic Turf Fields
SumBTEX
5
3
30
70
a SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
Table 4-67. Within- and Between-recycling Plant or Field Variability for Select VOC 60 °C Emission Factor
Analysis Results for Tire Crumb Rubber Collected from Tire Recycling Plants and Tire Crumb Rubber
Infill Collected from Synthetic Turf Fields
Tire Crumb Rubber
Analvtc"
Number of
Number of
Between
Within
Sampling Location
Plants or
Samples per
Plant or Field
Plant or Field
Fields
Plant or Field
% Variance
% Variance
Recycling Plants
Formaldehyde
9
3
76
24
Recycling Plants
Methyl isobutyl ketone
9
3
45
55
Recycling Plants
Benzothiazole
9
3
0
100
Recycling Plants
Styrene
9
3
88
12
Recycling Plants
Benzene
9
3
63
37
Recycling Plants
Toluene
9
3
62
38
Recycling Plants
Ethylbenzene
9
3
47
53
Recycling Plants
m/p-Xylene
9
3
16
84
Recycling Plants
o-Xylene
9
3
44
56
Recycling Plants
SumBTEX
9
3
60
40
Synthetic Turf Fields
Formaldehyde
5
3
34
66
Synthetic Turf Fields
Methyl isobutyl ketone
5
3
91
9
Synthetic Turf Fields
Benzothiazole
5
3
98
2
Synthetic Turf Fields
Styrene
5
3
95
5
Synthetic Turf Fields
Toluene
5
3
26
74
Synthetic Turf Fields
Ethylbenzene
5
3
82
18
Synthetic Turf Fields
m/p-Xvlcnc
5
3
85
15
Synthetic Turf Fields
o-Xylene
5
3
72
28
Synthetic Turf Fields
SumBTEX
5
3
86
14
a SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
175
-------
4.9.2.4 SVOC Emission Factors Analysis
Table 4-68 shows average and individual SVOC 25 °C emission measurement results for the sum of 15
PAHs, benzothiazole, and 4-tert-octylphenol for tire crumb rubber samples collected from three storage
bags at nine tire recycling plants. %RSD values ranged from 2% to 64% for Suml5PAH, 8.2% to 63%
for benzothiazole, and 3.5% to 51% for 4-tert-octylphenol.
Table 4-68. Select SVOC 25 °C Emission Factor Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-Plant Variabilityab
Chemical'
Plant
ID
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
Individual
Sample 1
Results
(ng/g/h)
Individual
Sample 2
Results
(ng/g/h)
Individual
Sample 3
Results
(ng/g/h)
Suml5PAH
A
3.4
0.31
9.3
3.7
3.2
3.2
Suml5PAH
B
3.0
0.31
10
2.9
2.8
3.4
Suml5PAH
C
0.87
0.31
36
0.66
0.72
1.2
Suml5PAH
D
3.3
0.84
25
3.9
2.4
3.7
Suml5PAH
E
1.3
0.20
16
1.5
1.1
1.3
Suml5PAH
F
1.6
1.0
64
0.84
1.2
2.8
Suml5PAH
G
2.2
0.044
2.0
2.2
2.2
2.3
Suml5PAH
H
2.0
0.8
41
1.1
2.6
2.2
Suml5PAH
I
3.4
1.1
31
4.2
2.2
3.7
Bcn/.othia/.ole
A
18
3.8
22
13
19
20
Ben/olhia/ole
B
17
2.6
15
16
15
20
Bcn/.othia/.ole
C
36
11
31
34
27
48
Bcn/.othia/.ole
D
45
18
41
65
40
29
Ben/.olhia/.ole
E
91
46
50
140
78
56
Ben/.olhia/.ole
F
41
9.3
23
34
52
38
Ben/.olhia/.ole
G
45
6.2
14
41
42
53
Ben/.olhia/.ole
H
34
21
63
58
27
16
Ben/.olhia/.ole
I
37
3.1
8.2
39
39
34
4-tert-octylphenol
A
0.22
0.017
7.6
0.22
0.21
0.24
4-tert-octylphenol
B
0.23
0.075
33
0.19
0.18
0.32
4-tert-octylphenol
C
0.32
0.099
31
0.22
0.31
0.42
4-tert-octylphenol
D
0.54
0.14
26
0.41
0.51
0.69
4-tert-octylphenol
E
0.41
0.049
12
0.46
0.39
0.37
4-tert-octylphenol
F
0.51
0.26
51
0.34
0.39
0.81
4-tert-octylphenol
G
0.45
0.016
3.5
0.44
0.46
0.44
4-tert-octylphenol
H
0.88
0.35
40
0.63
0.71
1.3
4-tert-octylphenol
I
0.71
0.12
17
0.57
0.75
0.80
aEach sample collected from a different storage bag at the recycling plants.
b Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two
significant figures.
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
176
-------
Table 4-69 shows average and individual SVOC 25 °C emission measurement results for the sum of 15
PAHs and benzothiazole for tire crumb rubber infill samples collected from three locations at five
synthetic turf fields. %RSD values ranged from 3.6% to 36% for the sum of 15 PAHs and 11% to 67%
for benzothiazole. No other chemicals are reported in this table because most other chemicals had one or
more results below chamber background levels.
Table 4-69. Select SVOC 25 °C Emission Factor Measurement Results for Individual Location Tire Crumb
Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing Within-Field Variabilitya b
Chemical'
Field
ID
Composite
Sample'1
(ng/g/h)
Mean
(ng/g/h)
% Relative
Standard
Deviation
Individual
Field Sample
Location 1
Results
(ng/g/h)
Individual
Field Sample
Location 2
Results
(ng/g/h)
Individual
Field Sample
Location 3
Results
(ng/g/h)
Suml5PAH
1
2.4
2.7
3.6
2.6
2.8
2.7
Suml5PAH
16
0.78
0.52
33
0.43
0.41
0.71
Suml5PAH
20
3.1
1.5
36
1.4
1.1
2.1
Suml5PAH
26
0.19
0.53
36
0.40
0.74
0.43
Suml5PAH
29
0.33
0.42
16
0.37
0.49
0.39
Benzothia/.olc
1
0.37
0.21
67
0.28
0.31
0.048
Bcn/.olhia/.olc
16
5.6
4.9
32
6.7
3.9
4.1
Bcn/.olhia/.olc
20
4.9
5.2
19
6.3
4.3
5.1
Benzothiazole
26
0.57
0.59
49
0.91
0.42
0.42
Benzothia/.olc
29
19
16
11
15
18
16
a Refer to Figure 3-5 for a schematic representation of positions for samples collected from locations 1 - 3 at synthetic turf
fields.
b Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two
significant figures.
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
d This is the measurement result from the analysis of the composite sample that was prepared from portions of tire crumb
rubber infill from the seven individual sample locations on the synthetic turf field.
Table 4-70 shows average and individual SVOC 60 °C emission measurement results for pyrene,
benzothiazole, and 4-tert-octylphenol for tire crumb rubber samples collected from three storage bags at
nine tire recycling plants. %RSD values ranged from 1.9% to 27% for pyrene, 8.4% to 53% for
benzothiazole, and 7.9% to 56% for 4-tert-octylphenol.
177
-------
Table 4-70. Select SVOC 60 °C Emission Factor Measurement Results for Individual Tire Crumb
Rubber Samples Collected at Nine Recycling Plants for Assessing Within-Plant Variabilityab
Chemical
Plant
ID
Mean
(ng/g/h)
Standard
Deviation
(ng/g/h)
% Relative
Standard
Deviation
Individual
Sample 1
Results
(ng/g/h)
Individual
Sample 2
Results
(ng/g/h)
Individual
Sample 3
Results
(ng/g/h)c
Pyrene
A
0.39
0.0091
2.3
0.40
0.39
0.39
Pyrene
B
0.37
0.044
12
0.34
0.35
0.42
Pyrene
C
0.31
0.039
12
0.28
0.30
0.36
Pyrene
D
0.42
0.035
8.2
0.40
0.45
N/A
Pyrene
E
0.33
0.030
9.3
0.33
0.30
0.36
Pyrene
F
0.28
0.0055
1.9
0.28
0.28
0.29
Pyrene
G
0.38
0.07
18
0.44
0.30
0.41
Pyrene
H
0.35
0.094
27
0.27
0.33
0.45
Pyrene
I
0.21
0.013
6.4
0.20
0.23
0.21
Benzothia/.olc
A
310
26
8.4
340
310
290
Bcn/.olhia/.olc
B
160
61
37
140
120
230
Bcn/.olhia/.olc
C
600
320
53
530
320
950
Benzothia/.olc
D
1100
530
48
720
1500
N/A
Bcn/.olhia/.olc
E
980
320
33
780
1300
820
Bcn/.olhia/.olc
F
570
180
32
360
650
690
Benzothiazole
G
500
54
11
530
430
520
Bcn/.olhia/.olc
H
30
58
22
240
220
330
Bcn/.olhia/.olc
I
360
74
21
400
400
270
4-tert-octylphenol
A
17
1.6
9.3
18
18
15
4-tert-octylphenol
B
13
7.5
56
4.6
17
18
4-tert-octylphenol
C
15
2.1
14
18
14
14
4-tert-octylphenol
D
35
17
50
23
47
N/A
4-tert-octylphenol
E
21
3.2
15
25
19
20
4-tert-octylphenol
F
13
1.1
7.9
12
14
14
4-tert-octylphenol
G
17
1.7
10
17
19
15
4-tert-octylphenol
H
24
9.0
37
20
18
35
4-tert-octylphenol
I
32
3.1
9.6
32
35
29
aEach sample collected from a different storage bag at the recycling plants.
b Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two
significant figures.
0 N/A - SVOC measurement results not usable for Plant ID 85.
Table 4-71 shows average and individual SVOC 60 °C emission measurement results for pyrene, the
sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol for tire crumb rubber infill samples collected
from three locations at five synthetic turf fields. %RSD values ranged from 1.8% to 9.0% for pyrene,
4.6% to 21% for Suml5PAH, 11% to 21% for benzothiazole, and 1.7% to 39% for 4-tert-octylphenol.
These results suggest low to modest variability in emissions at 60 °C for samples collected at multiple
locations on a synthetic turf field for these chemicals. The composite measurement results for Field ID
#26 were very low compared to other measurements, appearing as negative results due to chamber
background subtraction; it is not clear whether this represents a true difference, or a measurement error
for that sample. The variability in 60 °C emission measurement results for individual samples collected
at tire recycling plants and synthetic turf fields is shown graphically for selected SVOC chemicals in
Figure 4-36.
178
-------
Table 4-71. Select SVOC 60 °C Emission Factor Measurement Results for Individual Location Tire Crumb
Rubber Infill Samples Collected at Five Synthetic Turf Fields for Assessing Within-Field Variability3,15'0
Chemical'1
Field
ID
Composite
Sample'
(ng/g/h)
Mean
(ng/g/h)
% Relative
Standard
Deviation
Individual
Field Sample
Location 1
Results
(ng/g/h)
Individual
Field Sample
Location 2
Results
(ng/g/h)
Individual
Field Sample
Location 3
Results
(ng/g/h)
Pyrene
1
0.18
0.19
9.0
0.21
0.18
0.19
Pyrene
16
0.25
0.23
4.5
0.22
0.23
0.24
Pyrene
20
0.73
0.68
3.4
0.68
0.7
0.66
Pyrene
26
-0.025
0.15
8.0
0.14
0.15
0.17
Pyrene
29
0.37
0.31
1.8
0.31
0.31
0.32
Suml5PAH
1
1.4
1.8
8.5
1.9
1.7
1.6
Suml5PAH
16
1.1
1.2
21
1.1
1.5
0.97
Suml5PAH
20
3.6
3.8
4.6
3.9
3.9
3.6
Suml5PAH
26
0.21
0.7
9.9
0.75
0.62
0.72
Suml5PAH
29
2.7
2.4
7.8
2.6
2.3
2.3
Benzothiazole
1
4.0
4.7
11
4.2
5.3
4.7
Benzothiazole
16
18
17
27
22
17
13
Benzothiazole
20
35
38
15
43
39
32
Benzothiazole
26
-0.53
5.3
25
6.9
4.5
4.6
Benzothiazole
29
140
110
20
110
130
90
4-tert-octylphcnol
1
13
2.2
39
1.8
1.7
3.2
4-lcrl-oclylphcnol
16
4.9
4.2
24
5.3
3.8
3.4
4-tcrt-oclylphcnol
20
20
20
1.7
20
20
20
4-lcrl-oclylphcnol
26
-0.27
2.2
26
2.1
1.7
2.9
4-tert-octylphcnol
29
9.9
12
24
11
15
9.6
a Several results are reported as negative values. This is a result of the subtraction of chamber background values from the
sample measurement results. Although this does not represent a physical reality, the negative results are retained as part of
the distribution of corrected results.
b Statistics were calculated using original unrounded measurement results; all results in this table have been rounded to two
significant figures.
0 Refer to Figure 3-5 for a schematic representation of positions for samples collected from locations 1-3.
d Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
e This is the measurement result for the analysis of the composite sample that was prepared from portions of tire crumb rubber
infill from the seven locations on the synthetic turf field.
179
-------
Temperature=6C*C
Pyrene
Temperature=60'C
Pyrene
1 ce
0 75
0.75
0.25
ooo
0,00'
0 25
1 00-
A e C 0 £ F G K
Recycling Plant ID
Benzothiazoie
Temperature=60*C
1 16 20 26
Field ID
Benzothiazoie
Temperature=60C
Recycling Plant ID
4-tert-Octylphenol
Tempera!ure=60"C
Field ID
4-tert-Octylphenol
Temperatura=60°C
SO-
*0
30-
£
f
n
20
10
6
50'
40
30
20-
10-
a e
C 0 E F G H
Recycling Plant ID
16
20
Field ID
26
1500
1500
1000
1000
500
29
Figure 4-36. Within-tire recycling plant variability (left side) and within-synthetic turf
field variability (right side) variability for SVOC emission factor 60 °C analysis results
(ng/g/h) in tire crumb rubber for pyrene, benzothiazoie, 4-tert-octylphenol. [SVOC =
Semivolatile organic compound]
180
-------
The percent of total variance explained by within-recycling plant and between-recycling plant variances
is shown in Table 4-72 for select SVOC 25 °C emission factor measurements. Some chemicals had
greater within-plant variability than between-plant variability, while the reverse was observed for other
chemicals. The percent of total variance explained by within-field and between-field variances is also
shown in Table 4-72 for select SVOC 25 °C emission factor measurements. The amount of variability
explained by between-field differences was greater than the amount explained by within-field
differences for four chemicals. The reverse was observed for phenanthrene and dibutyl phthalate;
however, these results may have been affected by low measured emission factors.
Table 4-72. Within- and Between-Recycling Plant or Field Variability for Select SVOC 25 °C Emission Factor
Analysis Results for Tire Crumb Rubber Collected from Tire Recycling Plants and Tire Crumb Rubber Infill
Collected from Synthetic Turf Fields3
Tire Crumb Rubber
Analvtc
Number
Number of
Between
Within
Sampling Location
of Plants
Samples per
Plant or Field
Plant or Field
or Fields
Plant or Field
% Variance
% Variance
Recycling Plants
Phenanthrene
9
3
90
10
Recycling Plants
Suml5PAH
9
3
61
39
Recycling Plants
Benzothiazole
9
3
47
53
Recycling Plants
Dibutyl phthalate
9
3
14
86
Recycling Plants
Aniline
9
3
84
16
Recycling Plants
4-tert-octylphenol
9
3
54
46
Synthetic Turf Fields
Phenanthrene
5
3
10
90
Synthetic Turf Fields
Suml5PAH
5
3
91
9
Synthetic Turf Fields
Bcn/.olhia/.olc
5
3
96
4
Synthetic Turf Fields
Dibutyl phthalate
5
3
0
100
Synthetic Turf Fields
Aniline
5
3
94
6
Synthetic Turf Fields
4-tcrt-octvlphenol
5
3
70
30
11 SVOC = Semivolatile organic compound; Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including
Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene,
Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene,
Phenanthrene, Pyrene
The percent of total variance explained by within-recycling plant and between-recycling plant variances
is shown in Table 4-73 for select SVOC 60 °C emission factor measurements. Some chemicals had
greater within-plant variability than between-plant variability, while the reverse was observed for other
chemicals. The percent of total variance explained by within-field and between-field variances is also
shown in Table 4-73 for select SVOC 60 °C emission factor measurements. The amount of variability
explained by between-field differences was greater than the amount explained by within-field
differences for all chemicals. This matches the results observed for SVOCs that were solvent extracted
from tire crumb rubber infill collected at synthetic turf fields.
181
-------
Table 4-73. Within- and Between-Recycling Plant or Field Variability for Select SVOC 60 °C Emission Factor
Analysis Results for Tire Crumb Rubber Collectet
from Tire F
Recycling Plants
Tire Crumb Rubber
Sampling Location
Analvtc"
Number of
Plants or
Fields
Number of
Samples per
Plant or Field
Between
Plant or Field
% Variance
Within
Plant or Field
% Variance
Recycling Plants
Phenanthrene
9
2
15
85
Recycling Plants
Fluoranthene
9
2
54
46
Recycling Plants
Pyrene
9
2
56
44
Recycling Plants
Suml5PAH
9
2
47
53
Recycling Plants
Benzothiazole
9
2
60
40
Recycling Plants
Dibutyl phthalate
9
2
25
75
Recycling Plants
Aniline
9
2
55
45
Recycling Plants
4-tert-octylphenol
9
2
51
49
Synthetic Turf Fields
Phenanthrene
5
3
92
8
Synthetic Turf Fields
Fluoranthene
5
3
97
3
Synthetic Turf Fields
Pyrene
5
3
99
1
Synthetic Turf Fields
Suml5PAH
5
3
97
3
Synthetic Turf Fields
Bcn/.othia/.ole
5
3
94
6
Synthetic Turf Fields
Dibutyl phthalate
5
3
80
20
Synthetic Turf Fields
Aniline
5
3
99
1
Synthetic Turf Fields
4-tcrt-oclylphcnol
5
3
96
4
11 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
4.10 Assessment of Characteristics Potentially Associated with Differences Among
Synthetic Turf Fields
In addition to examining tire crumb rubber chemical substance differences between recycling plants and
synthetic turf fields, the research design allowed for exploration and analysis of potential differences in
the chemicals associated with tire crumb rubber infill among synthetic turf fields with different
characteristics including:
• Outdoor versus indoor field locations;
• The age of fields (installation year age groups 2004 - 2008, 2009 - 2012, 2013 - 2016); and
• Across the four U.S. census regions (Northeast, South, Midwest, West).
The numbers of fields with each of these characteristics was previously described. Comparison results
are reported here for a subset of chemical substances selected for highlighting observed differences, with
complete results for all target analytes shown in Appendices O through Q. Results for the following
analysis types are included in this reporting sub-section:
• Metals analyzed by ICP/MS
• Metals analyzed by XRF
• SVOCs analyzed in solvent extracts by GC/MS/MS
182
-------
• SVOCs non-quantitative analysis of solvent extracts by LC/TOFMS
• VOC emission factors from analysis by GC/TOFMS
• SVOC emission factors from analysis by GC/MS/MS.
4.10.1 Outdoor versus Indoor Synthetic Turf Fields
Tire crumb rubber infill mean chemical measurement results were compared for the group of outdoor
fields versus the group of indoor fields. For statistical analysis results, p-values are reported for
between-group differences in the cases where all measurement results were >0 (because the statistical
testing was performed on the log-transformed measurement results).
4.10.1.1 Metals by ICP/MS and XRF Analysis
Table 4-74 shows results for differences in mean concentrations of select metals analyzed in acid digests
by ICP/MS and in XRF analyses of tire crumb rubber infill collected at outdoor and indoor fields. No
statistically significant outdoor versus indoor differences were observed for metal concentrations in tire
crumb rubber infill. Average lead concentrations were approximately 50% higher in indoor fields
compared to outdoor fields, but the variability in lead concentrations, particularly for indoor fields, was
large; the variability was driven to a large extent by one higher lead measurement at an indoor field.
Figure 4-37 illustrates the distributions in ICP/MS measurement results for outdoor and indoor fields for
chromium, cobalt, lead, and zinc.
Table 4-74. Comparison of Select Metals Analyzed in Tire Crumb Rubber Infill Collected at Outdoor
and Indoor Synthetic Turf Fields3
Analysisb
Analvtc
Outdoor Fields
Mean (mg/kg)
Outdoor Fields
Standard
Deviation
(mg/kg)
Indoor Fields
Mean (mg/kg)
Indoor Fields
Standard
Deviation
(mg/kg)
F-test
p-value'
ICP/MS Analysis
Arsenic
0.39
0.18
0.37
0.23
0.488
ICP/MS Analysis
Cadmium
0.86
0.45
1.1
0.96
0.3997
ICP/MS Analysis
Chromium
1.7
0.88
1.5
0.80
NRd
ICP/MS Analysis
Cobalt
140
60
140
63
0.8128
ICP/MS Analysis
Lead
20
14
31
39
0.4709
ICP/MS Analysis
Zinc
15000
3300
15000
2600
0.6996
XRF Analysis
Chromium
14
3.0
14
2.9
0.9667
XRF Analysis
Cobalt
40
17
36
17
0.4099
XRF Analysis
Lead
31
13
45
31
0.1433
XRF Analysis
Zinc
33000
7900
34000
5800
0.458
a Outdoor Fields (n=25); Indoor Fields (n=15)
b ICP/MS = Inductively coupled plasma/mass spectrometry; XRF = X-ray fluorescence spectrometry
0 Statistical tests performed using ln-transformed measurement values.
dNR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
183
-------
Chromium
Cobalt
200
o>2-
O)
E
CT)
O)
E
100
Indoor Outdoor
Lead
Indoor
Outdoor
Zinc
CO 80
20000
O)
a> 16000
E
12000
Indoor Outdoor Indoor Outdoor
Figure 4-37. Comparison of ICP/MS metal analysis results (mg/kg) between tire
crumb rubber infill composite samples from indoor and outdoor synthetic turf
fields for chromium, cobalt, lead, and zinc. [ICP/MS = Inductively coupled plasma/mass
spectrometry]
4.10.1.2 SVOC Extracts by GC/MS/MS and LC/TOFMS Analysis
Table 4-75 shows results for differences in mean concentrations of select SVOCs in solvent extracts
analyzed by GC/MS/MS for tire crumb rubber infill collected at outdoor and indoor fields. Table 4-76
shows results for differences in mean chromatographic peak areas of select SVOCs in solvent extracts
analyzed by LC/TOFMS. Most of the SVOCs had statistically significant higher average measurements
in indoor versus outdoor field tire crumb rubber infill. Average indoor levels ranged from 1.5 to 10
times higher than outdoor levels for most SVOCs. The more volatile SVOCs had higher indoor/outdoor
ratios than less volatile SVOCs. A likely contribution to these differences is increased weathering at
outdoor locations, including heat, sunshine, ventilation rates, and rainfall. Figures 4-38 through 4-40
illustrate distributions in measurement results for outdoor and indoor fields for twelve SVOC analytes.
184
-------
Table 4-75. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber
Infill Collected at Outdoor and Indoor Synthetic Turf Fields3
Analvtcb
Outdoor Fields
Mean (mg/kg)
Outdoor Fields
Standard
Deviation
(mg/kg)
Indoor Fields
Mean (mg/kg)
Indoor Fields
Standard
Deviation
(mg/kg)
F-test
p-value'
Phenanthrene
0.76
0.71
4.8
2.6
<.0001
Fluoranthene
3.5
2.3
6.2
2.2
0.0004
Pyrene
8.8
3.9
19
3.7
<.0001
Benzo[a]pyrene
0.66
0.37
0.98
0.67
0.0375
Benzo [ghijperylene
1.1
0.54
1.6
0.68
0.0315
Suml5PAH
21
9.4
42
12
<.0001
Benzothiazole
5.6
9.2
19
14
<.0001
Dibutyl phthalate
0.63
0.70
2.9
1.4
<.0001
Bis(2-ethylhexyl) phthalate
29
27
65
53
0.0185
Aniline
0.38
0.24
1.2
0.54
<.0001
4-tert-octylphenol
3.5
2.2
20
7.9
<.0001
n-Hexadecane
0.20
0.20
2.2
1.3
<.0001
a Outdoor Fields (n=25); Indoor Fields (n=15)
b Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
0 Statistical tests performed using ln-transformed measurement values.
Table 4-76. Comparison of Select SVOC Extracts Non-quantitative Analysis Results by LC/TOFMS
for Tire Crumb Rubber Infill Collected at Outdoor and Indoor Synthetic Turf Fields3
Analyte
Outdoor Fields
Mean Area
Counts
Outdoor Fields
Area Counts
Standard
Deviation
Indoor Fields
Mean Area
Counts
Indoor Fields
Area Counts
Standard
Deviation
F-test
|)-valueb'c
2-mercaptobenzothiazole
5.5E+02
9.5E+02
4.0E+03
4.9E+03
NR
2-hydroxybenzothiazole
4.2E+04
7.7E+04
2.1E+05
1.2E+05
NR
cyclohexylamine
1.2E+05
2.1E+05
1.1E+06
1.0E+06
NR
di-cyclohexylamine
5.1E+06
6.4E+06
1.5E+07
7.8E+06
<.0001
N-cyclohexyl-N-
methylcyclohexanamine
1.4E+05
1.7E+05
3.9E+05
3.9E+05
0.0026
diisononylphthalate
2.8E+03
4.7E+04
7.1E+04
1.3E+05
NR
diisodecylphthalate
6.3E+03
8.8E+03
1.2E+05
4.4E+05
NR
a Outdoor Fields (n=25); Indoor Fields (n=15)
b Statistical tests performed using ln-transformed measurement values.
0 NR=Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
185
-------
Phenanthrene
Pyrene
g> 5.0
Indoor Outdoor
Benzo(a)pyrene
Indoor Outdoor
Sum 15 PAH
Indoor
Outdoor
Indoor
Outdoor
Figure 4-38. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg)
between tire crumb rubber infill composite samples from indoor and outdoor
synthetic turf fields for phenanthrene, pyrene, benzo[a] pyrene, and the sum of 15
PAHs. [GC/MS/MS = Gas chromatography/tandem mass spectrometry; SVOC = Semivolatile
organic compound; Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthvlene,
Anthracene. Benz[a]anthracene, Benzo [a]pyrene, Benzo(b)fluoranthene, Benzo[glii]perylene,
Benzo(k)lluoranthene, Chrysene, Dibenz[a,h] anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pvrene,
Naphthalene, Phenanthrene, Pyrene]
186
-------
Benzothiazole
4-tert-Octyl phenol
CO
a>
E
30
u>
en
40-
20-
Indoor Outdoor
Bis(2-ethylhexyl) phthalate
Indoor Outdoor
n-Hexadecane
150
o>100
O)
E
50
CD
d)
Indoor
Outdoor
Indoor
Outdoor
Figure 4-39. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg)
between tire crumb rubber infill composite samples from indoor and outdoor
synthetic turf fields for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl)
phthalate, and n-hexadecane. [GC/MS/MS = Gas chromatography/tandem mass
spectrometry; SVOC = Semivolatile organic compound]
187
-------
2-mercaptobenzothiazole
2-hy d roxyb e n zot h i azol e
15000
4e+05
3e+05
in 10000
2e+05
< 5000
1e+05
0e+00
Indoor Outdoor
cyclohexylamine
Indoor Outdoor
di-cyclohexy!amine
2e+06
c
3
o
O
(0
0)
1 e+06
0e+00-
3e+07
2e+07
1e+07
0e+00
Indoor
Outdoor
Indoor
Outdoor
Figure 4-40. Comparison of LC'/TOFMS extract SVOC' non-quantitative positive ionization
analysis results between tire crumb rubber infill composite samples from indoor and outdoor
synthetic turf fields for 2-mercatpobenzothiazole, 2-hydroxybenzothiazole, cyclohexylamine, di~
cyclohexylamine. [LC/TOFMS = Liquid cliromatography/time-of-flight mass spectrometry; SVOC =
Semivolatile organic compound]
4.10.1.3 VOC Emission Factors
Table 4-77 shows results for differences in mean 25 °C and 60 °C emission factors for select YOCs
analyzed by GC/TOFMS for tire crumb rubber infill collected at outdoor and indoor fields. Most of the
VOCs had higher emission factors for indoor versus outdoor fields, with the two chemicals with all
measurements > 0 showing statistically significant differences. Average indoor field emission factors
ranged from 2 to 34 times higher than outdoor field levels. A likely contribution to these differences is
increased weathering at outdoor locations, including heat, sunshine, ventilation rates, and rainfall. Figure
4-41 illustrates distributions in 60 °C emission factor measurement results for outdoor and indoor fields
for formaldehyde, benzothiazole, methyl isobutyl ketone, and styrene.
188
-------
Table 4-77. Comparison of Select VOC Emission Factors for Tire Crumb Rubber Infill Collected at Outdoor
and Indoor Synthetic Turf Fieldsa,b
Emission Test
Analvte'
Outdoor Fields
Mean (ng/g/h)
Outdoor Fields
Standard
Deviation
(ng/g/h)
Indoor Fields
Mean (ng/g/h)
Indoor Fields
Standard
Deviation
(ng/g/h)
F-test
p-value'1'
Emissions at 25 °C
Benzothiazole
9.4
16
51
26
NR
Emissions at 25 °C
o-Xylene
0.0024
0.068
0.081
0.10
NR
Emissions at 25 °C
SumBTEX
0.22
0.98
0.46
0.51
NR
Emissions at 60 °C
Formaldehyde
12
5.7
23
10
NR
Emissions at 60 °C
Melhvl isobuly 1 ketone
28
16
68
20
<.0001
Emissions at 60 °C
Bcn/.olhia/.olc
35
31
95
9.6
<.0001
Emissions at 60 °C
Slyrcnc
0.24
0.29
0.84
0.29
NR
Emissions at 60 °C
Toluene
0.11
0.33
0.24
0.24
NR
Emissions at 60 °C
Elhvlbcn/.cne
-0.12
0.20
-0.0059
0.26
NR
Emissions at 60 °C
m/p-Xvlcnc
0.043
0.97
0.61
0.97
NR
Emissions at 60 °C
o-Xylcnc
-0.39
0.7
-0.27
0.60
NR
Emissions at 60 °C
SumBTEX
-0.44
2.2
0.58
2.1
NR
a Several results are reported as negative values. This is a result of the subtraction of chamber background values from the
sample measurement results. Although this does not represent a physical reality, the negative results are retained as part of
the distribution of corrected results.
b Outdoor Fields (n=24 - 25); Indoor Fields (n=13 - 15)
0 SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
d Statistical tests performed using ln-transformed measurement values.
e Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
189
-------
Formaldehyde
Temperature=6CTC
Benzothiazole
Temperature=60X
120
40
60-
O)
90-
Iridoor
Outdoor
Methyl Isobutyl Ketone
Temperature=60"C
Indoor Outdoor
Styrene
Temperature=60°C
Indoor
Outdoor
Indoor
Outdoor
Figure 4-41. Comparison of VOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber infill composite samples from indoor and outdoor synthetic
turf fields for formaldehyde, benzothiazole, methyl isobutyl ketone, and styrene.
[VOC = Volatile organic compound]
4.10.1.4 SVOC Emission Factors
Table 4-78 shows results for differences in mean 25 °C and 60 °C emission factors for select SVOCs
analyzed by GC/MS/MS for tire crumb rubber infill collected at outdoor and indoor fields. Most of the
SVOCs had higher emission factors for indoor versus outdoor fields, particularly at the 60 °C test
temperature. At 25 °C, many of the emissions measurement results were below the method detection
limit and/or below chamber background measurements. At 60 °C, average indoor field emission factors
ranged from approximately 2 to 8 times higher than outdoor field emission factors. A likely contribution
to these differences is increased weathering at outdoor locations, including heat, sunshine, ventilation
rates, and rainfall. Figure 4-42 illustrates distributions in 60 °C emission factor measurement results for
outdoor and indoor fields for pyrene, the sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol,
190
-------
Table 4-78. Comparison of Select SVOC Emission Factors for Tire Crumb Rubber Infill Collected
at Outdoor and Indoor Synthetic Turf Fieldsa,b
Emission Test
Analvte'
Outdoor
Fields Mean
(ng/g/h)
Outdoor
Fields
Standard
Deviation
(ng/g/h)
Indoor Fields
Mean (ng/g/h)
Indoor Fields
Standard
Deviation
(ng/g/h)
F-test
p-value'1'
Emissions at 25 °C
Phenanthrene
0.017
0.050
0.038
0.045
NR
Emissions at 25 °C
Suml5PAH
0.56
0.56
0.72
0.74
0.323
Emissions at 25 °C
Benzothiazole
1.5
2.6
8.7
5.3
NR
Emissions at 25 °C
Dibutyl phthalate
0.088
0.36
-0.18
0.36
NR
Emissions at 25 °C
Aniline
0.088
0.20
0.77
0.42
NR
Emissions at 25 °C
4-tert-octylphenol
0.65
3.2
1.2
3.5
NR
Emissions at 60 °C
Phenanthrene
0.17
0.22
1.2
0.75
NRb
Emissions at 60 °C
Fluoranthene
0.11
0.085
0.23
0.11
NR
Emissions at 60 °C
Pyrene
0.20
0.14
0.44
0.24
NR
Emissions at 60 °C
Suml5PAH
1.0
0.65
3.6
2.1
<0.0001
Emissions at 60 °C
Ben/.olhia/.ole
9.7
11
74
64
NR
Emissions at 60 °C
Dibulvl phthalalc
0.11
0.43
0.20
0.39
NR
Emissions at 60 °C
Aniline
0.79
1.0
8.0
6.1
NR
Emissions at 60 °C
4-lerl-oclylphenol
2.9
3.1
11
5.0
NR
a One result is reported as a negative value. This is a result of the subtraction of chamber background values from the sample
measurement results. Although this does not represent a physical reality, the negative results are retained as part of the
distribution of corrected results.
b Outdoor Fields (n=25); Indoor Fields (n=15)
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
d Statistical tests performed using ln-transformed measurement values.
e NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
191
-------
Pyrerie Sum15PAH
T emperature=60°C Temperat ure=60°C
0.75
0.25
0.00
0.0
indoor Outdoor Indoor Outdoor
Benzothiazole 4-tert-Octylphenol
Temperat ure=60°C Temperature=60°C
200
150
Indoor Outdoor Indoor Outdoor
Figure 4-42. Comparison of SVOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber infill composite samples from indoor and outdoor synthetic turf
fields for pyrene, the sum of 15 PAHs, benzothiazole, 4-tert-octylphenol. [SVOC =
Semivolatile organic compound; Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including
Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene,
Indeno(l,2,3-cd)pyrene, Naphthalene, Phenantlirene, Pyrene]
4.10.2 Synthetic Field Installation Age
Tire crumb rubber infill mean chemical measurement results were compared for synthetic turf fields
organized into three groups, based on year of installation, as a measure of field age. For the statistical
analysis results, p-values are reported for between-group differences in the cases where all measurement
results were > 0 (because the statistical testing was performed on the log-transformed measurement
results). It is important to recognize that 50% of the field owners/managers reported the addition of new
tire crumb rubber material to the fields and two reported replacement of tire crumb rubber infill.
Because the timing and frequency of refreshment varied considerably across the fields, and some timing
information was not reported, no attempts at adjustment or further analyses by age were performed
based on this information. When viewing these results, it is also important to remember that substantial
differences were observed for outdoor versus indoor fields for the organic chemicals. In this section,
there is no differentiation between indoor and outdoor fields in each age category. In a later section, this
analysis is repeated but is restricted to outdoor fields only.
192
-------
4.10.2.1 Metals by ICP/MS arid XRF Analysis
Figure 4-43 illustrates the distributions in measurement results across the three field installation age
groups for chromium, cobalt, lead, and zinc. Differences in mean concentrations of select metals
analyzed in acid digests by ICP/MS and in XRF analyses are shown in Table 4-79 for tire crumb rubber
infill collected at fields in three different installation age groups. Average cobalt measurements had
statistically significant differences among the age group categories, but the differences were not
monotonic by field installation age. Results for zinc reached near-significance, but again, there was no
monotonic trend by field installation age. Lead ICP/MS average measurements showed a pattern of
increasing concentration with older installation age category; however, the increase was not statistically
significant. It is not clear whether this result for lead is an indicator of increasing external source
deposition over time, differences in lead concentrations in tires over time, or a chance result. The
average lead value for the oldest installation age group is highly influenced by one relati vely high
measurement result.
Chromium Cobalt
200
O)
ch
cn
100
2004-2008 2009-2012 2013-2016
Age Group
2004-2008 2009-2012 2013-2016
Age Group
Lead
Zinc
CD 80
20000
-SC
o) 16000
e
12000
2004-2008 2009-2012 2013-2016 2004-2008 2009-2012 2013-2016
Age Group Age Group
Figure 4-43. Comparison of ICP/MS metal analysis results (mg/kg) between tire
crumb rubber infill composite samples from synthetic turf fields in three
installation age groups for chromium, cobalt, lead, and zinc.
193
-------
Table 4-79. Comparison of Selected Metals in Tire Crumb Rubber Infill Collected from Synthetic Turf Fields in Three Field Installation Age Groups
Analvsisb
Analvtc
Fields Installed
2004 - 2008
Mean (mg/kg)
Fields Installed
2004 - 2008
Standard Deviation
(mg/kg)
Fields Installed
2009-2012
Mean (mg/kg)
Fields Installed
2009-2012
Standard Deviation
(mg/kg)
Fields
Installed
2013-2016
Mean (mg/kg)
Fields Installed
2013-2016
Standard Deviation
(mg/kg)
F-test
p-value1'1
ICP/MS Analysis
Arsenic
0.39
0.15
0.42
0.25
0.30
0.1
0.4723
ICP/MS Analysis
Cadmium
0.97
0.45
1.1
0.91
0.72
0.37
0.3463
ICP/MS Analysis
Chromium
1.8
1.0
1.7
0.79
1.3
0.68
NRb
ICP/MS Analysis
Cobalt
150
46
100
56
170
56
0.0006
ICP/MS Analysis
Lead
33
42
25
20
13
4.6
0.079
ICP/MS Analysis
Zinc
15000
2700
14000
2600
16000
3400
0.0501
XRF Analysis
Chromium
14
2.7
13
3.2
15
2.3
0.1121
XRF Analysis
Cobalt
39
16
32
16
49
17
0.0629
XRF Analysis
Lead
38
26
41
24
27
12
0.2297
XRF Analysis
Zinc
33000
7200
31000
6300
37000
7500
0.1074
a Fields installed 2004 - 2008 (n=ll); 2009 - 2012 (n=18); 2013 - 2016 (n=ll)
b ICP/MS = Inductively coupled plasma/mass spectrometry; XRF = X-ray fluorescence spectrometry
0 Statistical tests performed using ln-transformed measurement values.
dNR=Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set
194
-------
4.10.2.2 SVOC Extracts by GC/MS/MS and LC/TOFMS Analysis
Table 4-80 shows results for differences in mean concentrations of select SVOCs analyzed in
solvent extracts by GC/MS/MS for tire crumb rubber infill collected at fields in three different
installation age groups. Benzo[a]pyrene, benzo[ghi]perylene and bis(2-ethylhexyl) phthalate
showed statistically significant differences among the age group categories. Only bis(2-
ethylhexyl) phthalate showed a monotonic trend of increasing average concentration with older
field age category. It is not clear whether this result is an indicator of increasing external source
deposition over time, differences in concentrations in tires over time, or a chance result. Table 4-
81 shows results for differences in mean chromatographic peak areas of select SVOCs analyzed
in solvent extracts by LC/TOFMS for tire crumb rubber infill collected at fields in three different
installation age groups. None of the LC/TOFMS analytes showed any statistically significant
differences across age groups or any apparent trends with field installation age categories.
Figures 4-44 through 4-46 illustrates the distributions in measurement results across the three
field installation age groups for twelve SVOC analytes.
Table 4-80. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber Infill
Collected from Synthetic Turf Fields in Three Field Installation Age Groups3
Analvtcb
Fields
Installed
2004 - 2008
Mean
(mg/kg)
Fields
Installed
2004 - 2008
Standard
Deviation
(mg/kg)
Fields
Installed
2009-2012
Mean
(mg/kg)
Fields
Installed
2009-2012
Standard
Deviation
(mg/kg)
Fields
Installed
2013-2016
Mean
(mg/kg)
Fields
Installed
2013-2016
Standard
Deviation
(mg/kg)
F-test
p-value'
Phenanthrene
2.1
2.2
3.0
3.3
1.3
0.93
0.389
Fluoranthene
3.6
2.6
5.1
2.9
4.5
1.7
0.1098
Pyrene
11
7.8
14
6.6
12
2.9
0.2171
Benzo[a]pyrene
0.59
0.24
0.95
0.62
0.68
0.48
0.0531
Benzo [ghijperylene
1.4
0.70
1.5
0.59
0.88
0.47
0.0232
Suml5PAH
25
16
33
17
26
8.2
0.2033
Benzothiazole
7.5
7.2
12
16
12
12
0.4355
Dibutyl phthalate
1.9
2.1
1.5
1.4
1.1
0.84
0.8196
Bis(2-ethylhexyl)
phthalate
61
60
45
34
20
21
0.0215
Aniline
0.55
0.37
0.81
0.71
0.58
0.25
0.563
4-tert-octylphenol
11
11
12
11
5.0
2.4
0.4372
n-Hexadecane
0.95
0.85
1.3
1.7
0.43
0.41
0.5861
a Fields installed 2004 - 2008 (n=ll); 2009 - 2012 (n=18); 2013 - 2016 (n=ll)
b Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
0 Statistical tests performed using ln-transformed measurement values.
195
-------
Table 4-81. Comparison of Select SVOC Extracts with Non-quantitative LC/TOFMS Analysis for Tire Crumb Rubber Infill Collected from Synthetic
Turf Fields in Three Field Installation Age Groupsa,b
Analvtc
Fields Installed
2004 - 2008
Mean Area
Counts
Fields Installed
2004 - 2008
Area Counts
Standard Deviation
Fields Installed
2009-2012
Mean Area
Counts
Fields Installed
2009-2012
Area Counts
Standard Deviation
Fields Installed
2013-2016
Mean Area
Counts
Fields Installed
2013-2016
Area Counts
Standard Deviation
F-test
p-value1'1
2-mercaptobenzothiazole
1.4E+03
2.2E+03
2.7E+03
4.7E+03
8.7E+02
1.1E+03
NR
2-hydrozybenzothiazole
1.1E+05
1.4E+05
1.1E+05
1.3E+05
8.9E+04
1.1E+05
NR
cyclohexylamine
5.8E+05
8.9E+05
6.0E+05
9.2E+05
2.0E+05
2.8E+05
NR
di-cyclohexylamine
8.6E+06
9.7E+06
8.5E+06
8.6E+06
1.0E+07
7.7E+06
0.4479
N-cyclohexyl-N-
methylcyclohexanamine
1.8E+05
1.8E+05
2.6E+05
4.0E+05
2.4E+05
2.0E+05
0.2555
diisononylphthalate
1.5E+04
5.5E+04
4.5E+04
1.2E+05
1.5E+04
7.0E+04
NR
diisodecylphthalate
1.6E+05
5.1E+05
8.0E+03
1.0E+04
2.4E+03
2.0E+03
NR
aFields installed 2004 - 2008 (n=ll); 2009 - 2012 (n=18); 2013 - 2016 (n=ll)
b Statistical tests performed using ln-transformed measurement values.
0 NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
196
-------
Phenanthrene
Pyrene
10.0
7.5
o>
w 5.0
2.5
0.0
2004 - 2008 2009 - 2012 2013 - 2016
Age Group
25
20
5*15
O)
E
10
2004-2008 2009-2012 2013-2016
Age Group
CD
a>
E
Benzo{a)pyrene
60
J?40
CTJ
E
20
Sum15PAH
2004-2008 2009-2012 2013-2016 2004-2008 2009-2012 2013-2016
Age Group Age Group
Figure 4-44. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg) between
tire crumb rubber infill composite samples from synthetic turf fields in three installation
age groups for phenanthrene, pyrene, benzo[a]pyrene, and the sum of 15 PAHs.
[GC/MS/MS = Gas chromatography /tandem mass spectrometry; SVOC = Semivolatile organic compound;
Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene,
Benz[a]anthracene. Benzo [ajpyrene, Benzo(b)fluoranthene. Bcnz.o|ghi|pcrylcne. Benzo(k)fluoranthene,
Chrysene. Dibenz[a,h] anthracene, Fluoranthene. Fluorene, Indeno(l,2.3-cd)pyrene, Naphthalene,
Phenanthrene, Pyrene]
197
-------
Benzothiazole
4-tert-Octylphenol
2004-2008 2009-2012 2013-2016
Age Group
Bis(2-ethylhexyl) phthalate
2004-2008 2009-2012 2013-2016
Age Group
n-Hexadecane
150
Ui
cn
2004-2008 2009-2012 2013-2016
Age Group
2004-2008 2009-2012 2013-2016
Age Group
Figure 4-45. Comparison of G(7MS/MS extract SVOC analysis results (mg/kg) between
tire crumb rubber infill composite samples from synthetic turf fields in three installation
age groups for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl) phthalate, and
n-hexadecane. [GC/MS/MS = Gas cliromatography/tandem mass spectrometry; SVOC = Semivolatile
organic compound]
198
-------
2-mercaptobenzothiazole
2-hydroxybenzothiazote
4e+05
3e+05
Oe+OO
»10000-
15000'
2004 - 2008 2009 - 2012 2013 - 2016
Age Group
cyclohexylamine
2004 - 20082009 - 20122013 - 2016
Age Group
di-cy cloh exylami n e
2e+06
c 2e+07
1e+06
0e+00
Oe+OO¦
c
zs
o
o
tu
2?1e+06
<
2004 - 20082009 - 20122013 - 2016
Age Group
2004 - 2008 2009 - 20122013 - 2016
Age Group
Figure 4-46. Comparison of LC/TOFMS extract SVOC non-quantitative positive ionization
analysis results between tire crumb rubber infill composite samples from synthetic turf fields
in three installation age groups for 2-mercaptobenzothiazole, 2-hydroxybenzothiazole,
cyclohexylamine, and di-cyclohexylamine. [LC/TOFMS = Liquid cliromatography/time-of-flight
mass spectrometry; SVOC = Semivolatile organic compound]
4.10.2.3 VOC Emission Factors
Table 4-82 shows results for differences in mean 25 °C and 60 °C emission factors for select VOCs
analyzed by GC/TOFMS for tire crumb rubber infill collected at fields in three different installation age
groups. There were no statistically significant differences across the age groups, although most analytes
had some results that were < 0. Only toluene showed an apparent monotonic trend of increasing average
concentration with newer field age category. Figure 4-47 illustrates the distributions in 60 °C emission
factor measurement results across the three field installation age groups for formaldehyde,
benzothiazole, methyl isobutyl ketone, and styrene.
199
-------
Table 4-82. Comparison of Select VOC Emission Factors in Tire Crumb Rubber Infill Collected from Synthetic Turf Fields in Three Field Installation
Age Groupsa'b
Emissions Test
Analvtc'
Fields Installed
2004 - 2008
Mean (ng/g/h)
Fields Installed
2004 - 2008
Standard
Deviation
(ng/g/h)
Fields Installed
2009-2012
Mean (ng/g/h)
Fields Installed
2009-2012
Standard
Deviation
(ng/g/h)
Fields Installed
2013-2016
Mean (ng/g/h)
Fields Installed
2013-2016
Standard
Deviation
(ng/g/h)
F-test
p-value'1'
Emissions at 25 °C
Benzothiazole
25
26
26
34
22
22
NR
Emissions at 25 °C
o-Xylene
0.054
0.083
0.042
0.11
-0.012
0.053
NR
Emissions at 25 °C
SumBTEX
0.25
0.91
0.39
0.72
0.22
1.0
NR
Emissions at 60 °C
Formaldehyde
17
5.6
18
13
13
3.7
NR
Emissions at 60 °C
Melhvl isobulvl ketone
50
29
39
27
40
20
0.5356
Emissions at 60 °C
Bcn/.olhia/.olc
63
44
49
40
59
34
0.8176
Emissions at 60 °C
Slyrcnc
0.53
0.39
0.51
0.46
0.26
0.28
NR
Emissions at 60 °C
Toluene
0.092
0.16
0.14
0.31
0.25
0.42
NR
Emissions at 60 °C
Elhvlbcn/.cne
-0.11
0.22
-0.067
0.24
-0.071
0.23
NR
Emissions at 60 °C
m/p-Xylcnc
0.29
1.1
0.33
1.1
0.059
0.82
NR
Emissions at 60 °C
o-Xylenc
-0.3
0.75
-0.28
0.7
-0.52
0.51
NR
Emissions at 60 °C
SumBTEX
-0.26
2.0
0.055
2.5
-0.11
2.0
NR
a Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
bFields installed 2004 - 2008 (n=ll); 2009 - 2012 (n=16 - 18); 2013 - 2016 (n=10 - 11)
0 SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
d Statistical tests performed using ln-transformed measurement values.
e NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
200
-------
Formaldehyde
Temperature=60"C
Berizothiazole
T emperature=60°C
2004-2008 2009-2012 2013-2016
Age Group
Methyl Isobutyl Ketone
Temperature=60°C
2004 - 2008 2009 - 2012 2013 - 2016
Age Group
Styrene
Temperature=60°C
0.0
25-
2004-2008 2009-2012 2013 -2016
Age Group
2004 - 2008 2009 - 2012 2013 - 2016
Age Group
Figure 4-47. Comparison of VOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber infill composite samples from synthetic turf fields in three
installation age groups for formaldehyde, benzothiazole, methyl isobutyl ketone,
and styrene. [VOC = Volatile organic compound]
4.10.2.4 SVOC Emission Factors
Table 4-83 shows results for differences in mean 25 °C and 60 °C emission factors for select SVOCs
analyzed by GC/MS/MS for tire crumb rubber infill collected at fields in three different installation age
groups. There were no statistically significant differences across the age groups, although most analytes
had some results that were < 0 due to subtraction of chamber background levels. In emissions testing at
25 °C, 4-tert-octylphenol showed an apparent monotonic trend of increasing average concentration with
newer installation age group and aniline showed an apparent monotonic trend of decreasing average
concentration with newer installation age group. However, neither trend was apparent in 60 °C emission
test results. Figure 4-48 illustrates the distributions in 60 °C emission factor measurement results across
the three field installation age groups for pyrene, the sum of 15 PAHs, benzothiazole, and 4-tert-
octylphenol.
201
-------
Table 4-83. Comparison of Select SVOC Emission Factors in Tire Crumb Rubber Infill Collected from Synthetic Turf Fields in Three Field
Installation Age Groupsa'b
Emissions Test
Analvte'
Fields Installed
2004 - 2008
Mean (ng/g/h)
Fields Installed
2004 - 2008
Standard
Deviation
(ng/g/h)
Fields Installed
2009-2012
Mean (ng/g/h)
Fields Installed
2009-2012
Standard
Deviation
(ng/g/h)
Fields Installed
2013-2016
Mean (ng/g/h)
Fields Installed
2013-2016
Standard
Deviation
(ng/g/h)
F-test
p-value'1'
Emissions at 25 °C
Phenanthrene
0.027
0.035
0.032
0.045
0.012
0.066
NR
Emissions at 25 °C
Suml5PAH
0.73
0.83
0.58
0.55
0.58
0.56
0.7377
Emissions at 25 °C
Benzothiazole
3.7
4.5
5.2
6.3
3.2
3.5
NR
Emissions at 25 °C
Dibutyl phthalate
-0.031
0.25
0.029
0.42
-0.056
0.43
NR
Emissions at 25 °C
Aniline
0.46
0.53
0.34
0.48
0.24
0.26
NR
Emissions at 25 °C
4-tert-octylphenol
0.12
0.15
0.90
3.3
1.5
4.8
NR
Emissions at 60 °C
Phenanthrene
0.46
0.51
0.81
0.93
0.31
0.27
NR
Emissions at 60 °C
Fluoranthene
0.13
0.10
0.19
0.13
0.13
0.088
NR
Emissions at 60 °C
Pyrene
0.21
0.20
0.35
0.24
0.27
0.15
NR
Emissions at 60 °C
Suml5PAH
1.6
1.2
2.6
2.5
1.4
0.77
0.2777
Emissions at 60 °C
Ben/.olhia/.ole
21
25
51
69
18
14
NR
Emissions at 60 °C
Dibulvl phthalalc
0.048
0.21
0.19
0.52
0.17
0.39
NR
Emissions at 60 °C
Aniline
3.0
3.7
5.0
6.8
1.5
1.4
NR
Emissions at 60 °C
4-tert-octylphenol
5.7
6.2
6.9
6.3
4.2
2.9
NR
a Two results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
bFields installed 2004 - 2008 (n=ll); 2009 - 2012 (n=16 - 18); 2013 - 2016 (n=10 - 11)
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
d Statistical tests performed using ln-transformed measurement values.
e Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
202
-------
Pyrene
Temperature=60°C
Sum15PAH
Temperature=60°C
0.75
7.5
0.25
2.5
0.00
0.0
2004-2008 2009-2012 2013-2016
Age Group
Benzothiazole
Temperature=60°C
2004-2008 2009-2012 2013-2016
Age Group
4-tert-Octylphenol
Temperature=60"C
200
150
50
2004-2008 2009-2012 2013-2016
Age Group
2004-2008 2009-2012 2013-2016
Age Group
Figure 4-48. Comparison of SVOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber infill composite samples from synthetic turf fields in three
installation age groups for pyrene, the sum of 15 PAHs, benzothiazole, and 4-tert-
octylphenol. [SVOC = Semivolatile organic compound; Suml5PAH = Sum of 15 of the 16
EPA 'priority' PAHs, including Acenaphthylene, Anthracene. Benz[a]anthracene, Benzo[a]pyrene,
Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
4.10.3 Synthetic Field Installation Age Restricted to Outdoor Fields
In order to help distinguish whether differences in chemicals associated with tire crumb rubber infill
may be related to field age, the field installation age group analyses were re-am, this time restricted to
outdoor fields only. This was done to remove the contributions of the indoor versus outdoor differences
that were previously observed, particularly for the organic chemicals. The sample sizes were reduced
through the restriction to outdoor fields only. Analyses were not performed separately for indoor fields
because of the small group sample sizes, and because all but one indoor field were in the two older field
installation age categories.
4.10.3.1 Metals by ICP/MS and XRF Analysis
Figure 4-49 illustrates the distributions in measurement results for recycling plants and across both the
indoor/outdoor and installation age groups for select metals analyzed by ICP/MS. Differences in mean
203
-------
concentrations of select metals analyzed in acid digests by ICP/MS and in XRF analyses are shown in
Table 4-84 for tire crumb rubber infill collected at outdoor fields in three different installation age
groups. Average cobalt measurements had statistically significant differences among the age group
categories, but the differences were not monotonic by field installation age group. Results for zinc
reached significance, with the highest average concentrations found in the newest installation age
category. While the analysis measurement results, with statistical test results, reported in tables in this
sub-section are restricted to outdoor fields only, figures have been prepared to expand on comparisons,
with the recycling plant results shown alongside the results for both indoor and outdoor fields in
different age groups.
Chromium Cobalt
3
2
o>
-5£
e
1
o
300
*200
ra
E
100
2C16 2009 - 2012 20M - 2006 2013 - 2018 2009 - 2012 2004 - 200ft
Age Group
201B 2009 -2012 2001 - 20GB 2013-2016 2009-2012 2004 - 200*
Age Group
Lead
Zinc
160
Moor mm
iao-
a> SO'
E
r<+cyi!r"
-------
Table 4-84. Comparison of Select Metals in Tire Crumb Rubber Infill Collected from Outdoor Synthetic Turf Fields in Three Field Installation
Age Groups3
Analvsisb
Analvtc
Fields Installed
2004 - 2008
Mean (mg/kg)
Fields Installed
2004 - 2008
Standard Deviation
(mg/kg)
Fields Installed
2009-2012
Mean (mg/kg)
Fields Installed
2009-2012
Standard Deviation
(mg/kg)
Fields Installed
2013-2016
Mean (mg/kg)
Fields Installed
2013-2016
Standard Deviation
(mg/kg)
F-test
p-value'
ICP/MS Analysis
Arsenic
0.43
0.12
0.46
0.22
0.29
0.094
0.0618
ICP/MS Analysis
Cadmium
0.96
0.30
0.94
0.56
0.73
0.39
0.3877
ICP/MS Analysis
Chromium
2.1
0.83
1.9
0.98
1.3
0.71
NRd
ICP/MS Analysis
Cobalt
160
45
87
29
170
59
0.0002
ICP/MS Analysis
Lead
22
4.1
25
20
13
4.7
0.09
ICP/MS Analysis
Zinc
13000
1700
13000
2800
17000
3400
0.02
XRF Analysis
Chromium
14
1.7
13
3.9
14
2.4
0.2588
XRF Analysis
Cobalt
38
14
-> ->
16
49
18
0.1183
XRF Analysis
Lead
29
13
38
14
26
12
0.1714
XRF Analysis
Zinc
29000
7400
30000
6800
37000
7900
0.0534
aFields installed 2004 - 2008 (n=5); 2009 - 2012 (n=10); 2013 - 2016 (n=10)
b ICP/MS = Inductively coupled plasma/mass spectrometry; XRF = X-ray fluorescence spectrometry
0 Statistical tests performed using ln-transformed measurement values.
dNR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set
205
-------
4.10.3.2 SVOC Extracts by GC/MS/MS and LC/TOFMS
Table 4-85 shows results for differences in mean concentrations of selected SVOCs analyzed in solvent
extracts by GC/MS/MS for tire crumb rubber infill collected at outdoor fields in three different
installation age groups. Most of the analytes show statistically significant differences across the age
groups. In many, but not all cases, there is a monotonic trend of decreasing average concentrations with
older field installation age group. Table 4-86 shows results for differences in mean chromatographic
peak areas of selected SVOCs analyzed in solvent extracts by LC/TOFMS for tire crumb rubber infill
collected at outdoor fields in three different installation age groups. Monotonic trends of decreasing
average concentrations with older field installation age group were observed for the four chemicals
reported in that table, as well.
When analyses were restricted to outdoor fields only, many SVOCs had statistically significant different
concentrations among age groups, with decreasing average levels with older field installation age. These
results support the likely importance of weathering for changes in SVOC concentrations in tire crumb
rubber infill used on outdoor fields over time. However, because no longitudinal measurements were
performed at individual fields, it cannot be entirely ruled out that some results represent differences in
the chemical composition of the recycled tires of different ages. The differences in concentrations in
indoor field infill versus outdoor field infill for the same installation age groups supports a weathering
effect explanation for most chemicals.
Figures 4-50 through 4-52 illustrate the distributions in measurement results for recycling plants and
across both the indoor/outdoor and installation age groups to provide a more global illustration of
differences among characteristics categories for chemicals in tire crumb rubber and tire crumb rubber
infill. For most of the SVOC target analytes shown in these figures, recycling plant average
concentrations are similar to or higher than those for the indoor fields, which in turn are generally higher
than those the outdoor fields. The pattern was less clear for benzo[a]pyrene, which, as a five-ring PAH,
has a very low vapor pressure. Bis(2-ethylhexyl) phthalate did not follow this pattern; instead,
concentrations were generally higher in the synthetic turf field samples as compared to recycling plant
samples, and indoor levels were generally higher than outdoor levels.
206
-------
Table 4-85. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber Infill Collected from Outdoor Synthetic Turf
Fields in Three Field Installation Age Groupsa,b
Analvtc'
Fields Installed
Fields Installed
Fields Installed
Fields Installed
Fields Installed
Fields Installed
F-test
2004 - 2008
2004 - 2008
2009-2012
2009-2012
2013-2016
2013-2016
p-value1'
Mean (mg/kg)
Standard Deviation
(mg/kg)
Mean (mg/kg)
Standard Deviation
(mg/kg)
Mean (mg/kg)
Standard Deviation
(mg/kg)
Fluoranthene
1.4
0.71
3.5
2.5
4.6
1.8
0.0002
Pyrene
3.5
0.74
8.6
2.8
12
2.8
<.0001
Benzo[a]pyrene
0.46
0.12
0.73
0.26
0.70
0.51
0.2415
Benzo [ghijperylene
1.1
0.41
1.4
0.54
0.84
0.48
0.0700
Suml5PAH
11
3.8
22
8.7
25
8.5
0.0004
Benzothiazole
1.0
0.58
2.3
1.4
11
13
0.0002
Dibutyl phthalate
0.074
0.043
0.58
0.7
0.95
0.72
0.0034
Bis(2-ethylhexyl) phthalate
33
34
41
29
15
16
0.029
Aniline
0.18
0.10
0.31
0.18
0.54
0.23
0.0005
4-tert-octylphenol
1.1
1.2
3.6
1.9
4.6
2.0
0.0001
n-Hexadecane
0.13
0.027
0.11
0.067
0.33
0.27
0.0212
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry
b Fields installed 2004 - 2008 (n=5); 2009 - 2012 (n=10); 2013 - 2016 (n=10)
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
d Statistical tests performed using ln-transformed measurement values.
Table 4-86. Comparison of Select SVOC Extracts with Non-quantitative LC/TOFMS Analysis for Tire Crumb Rubber Infill Collected from Outdoor
Synthetic Turf Fields in Three Field Installation Age Groupsa,b
Analvte
Fields Installed
2004 - 2008
Mean Area
Counts
Fields Installed
2004 - 2008
Area Counts
Standard Deviation
Fields Installed
2009-2012
Mean Area
Counts
Fields Installed
2009-2012
Area Counts
Standard Deviation
Fields Installed
2013-2016
Mean Area
Counts
Fields Installed
2013-2016
Area Counts
Standard Deviation
F-test
p-valuc'd
2-mercaptobenzothiazole
9.5E+01
1.3E+02
4.2E+02
8.5E+02
9.2E+02
1.2E+03
NR
2-hydroxybenzothiazole
4.1E+03
4.7E+03
2.3E+04
2.6E+04
8.0E+04
1.1E+05
NR
cyclohexylamine
5.1E+04
7.3E+04
5.5E+04
9.7E+04
2.1E+05
3.0E+05
NR
di-cyclohexylamine
5.9E+05
2.4E+05
3.0E+06
3.0E+06
9.5E+06
7.9E+06
0.0009
11 SVOC = Semivolatile organic compound; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry
b Fields installed 2004 - 2008 (n=5); 2009 - 2012 (n=10); 2013 - 2016 (n=10)
0 Statistical tests performed using ln-transformed measurement values.
dNR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
207
-------
Racyek^ P
10.0-
7.5-
u>
|> 5.0
2.5'
0.0-
Phenanthrene
ln«>otK O.K
ltt«ydiTgp
25
20-
c»15-
o>
E
10-
Pyrene
201« 2009-2012 2004 - 2006 2013-2016 2CO»-2012 2COt-20C«
Age Group
Benzo(a)pyrene
2016 2009 - 20)2 20M-2CU8 201J-2016 20W-2012 2004-2006
Age Group
Sum15PAH
o>
2016
2013 ¦ 2016 2008 J012 2004 - 2008
Age Group Age Group
Figure 4-50. Comparison of GC'/MS/MS extract SVOC analysis results (nig/kg) between tire crumb
rubber from recycling plants and tire crumb rubber infill composite samples from synthetic turf fields
by age group for phenanthrene, pyrene, benzo(a)pyrene, and the sum of 15 PAHs. [GC/MS/MS = Gas
cliromatography/tandem mass spectrometry; SVOC = Semivolatile organic compound]
208
-------
Berizothiazole
ftccytAnfl foartt
too-
75-
en
50-
25-
Outdoor Fieils
Recydingi Plants
4-tert-Octylphenol
f=
40-
30'
Oi
jx.
g20-
10-
Outdoor Fields
WIS 2009-2012 2004 - 2008 2013 - 2016 2009-2012 2004-2008
Age Group
Bis(2-ethylhexyl) phthalate
Racycfcng «an» Indoor Fits* I j OutHost Firtft
ISO-
100-
o>
J£
B)
E
50-
rn 2009- 2012 2004-2we wis -201« 2000-201: 2«>4-2oce
Age Group
n-Hexadecane
R^cydiftfl Ptefw] [ Inaoor f
-------
nmn -n.j HaiJ
y> 30000 •
P20000-
<
2-mercaptobenzothiazole
Outdoor Fk
T
Outtkx* FieWs
o
nj2e+05-
2-hydroxybenzothiazote
Inflow ftHH ObMowFtekte
2016 2009-2012 2004-2008 2013-2016 2009 - 2012 2004 - 2008
Age Group
cydohexylamine
2016 2009 - 2012 2004 - 2008 2013-20t6 2009-2012 2004-2006
Age Group
4e+07-
3e+07-
O 2e+07-
di-cyclohexylamine
JL
OuMOOtFiekte
-2012 2004-2008 2013 - 2016 2009 - 2012 20C4 - 2008
Age Group
2009 *112 20W -200S 20T3-20t6 20«-2012 200fl-2008
Age Group
Figure 4-52. Comparison of LC/TOFMS extract SVOC non-quantitative positive ionization
analysis results between tire crumb rubber from recycling plants and tire crumb rubber infill
composite samples from synthetic turf fields by age group. Results for fields are shown separately
for indoor and outdoor fields in two or three installation age groups for 2-mercaptobenzothiazole,
2-hydroxybenzothiazole, cydohexylamine, di-cyclohexylamine. [LC/TOFMS = Liquid chromatography/
time-of-flight mass spectrometry; SVOC = Semivolatile organic compound]
4.10.3.3 VOC Emission Factors
Table 4-87 shows results for differences in mean 25 °C and 60 °C emission factors for select VOCs
analyzed by GC/TOFMS for tire cmmb rubber infill collected at outdoor fields in three different
installation age groups. There were no statistically significant differences across the age groups,
although most analytes had some results that were not > 0. Benzothiazole and methyl isobutyl ketone
results approached statistical significance for their 60 °C emission factors. There were no apparent
monotonic trends of decreasing average concentration with older field installation group. For
benzothiazole and methyl isobutyl ketone, the two target analytes with the greatest emission factors at
60 °C, the highest emission factors were measured from fields in the newest field installation age
category.
210
-------
Table 4-87. Comparison of Select VOC Emission Factors in Tire Crumb Rubber Infill Collected from Outdoor Synthetic Turf Fields in Three Field
Installation Age Groupsa,b
Emissions Test
Analyte'
Fields Installed
2004 - 2008
Mean (ng/g/h)
Fields Installed
2004 - 2008
Standard
Deviation
(ng/g/h)
Fields Installed
2009-2012
Mean (ng/g/h)
Fields Installed
2009-2012
Standard
Deviation
(ng/g/h)
Fields Installed
2013-2016
Mean (ng/g/h)
Fields Installed
2013-2016
Standard
Deviation
(ng/g/h)
F-test
p-value'1'
Emissions at 25 °C
Benzothiazole
2.6
6.0
3.5
4.0
20
23
NR
Emissions at 25 °C
o-Xylene
0.073
0.1
-0.012
0.041
-0.021
0.047
NR
Emissions at 25 °C
SumBTEX
0.47
1.4
0.11
0.77
0.19
1.1
NR
Emissions at 60 °C
Formaldehyde
15
7.7
10
6.3
12
^5
J.J
NR
Emissions at 60 °C
Methyl isobulv 1 ketone
22
5.3
22
8.4
39
21
0.061
Emissions at 60 °C
Bcn/.olhia/.olc
27
41
20
14
55
33
0.0709
Emissions at 60 °C
Slyrcnc
0.27
0.32
0.26
0.36
0.20
0.21
NR
Emissions at 60 °C
Toluene
0.073
0.21
-0.013
0.24
0.27
0.44
NR
Emissions at 60 °C
Elhvlbcnzcnc
-0.14
0.19
-0.13
0.22
-0.11
0.21
NR
Emissions at 60 °C
m/p-Xylcnc
0.14
1.3
0.11
1.1
-0.089
0.71
NR
Emissions at 60 °C
o-Xvlcnc
-0.18
1.0
-0.30
0.74
-0.62
0.44
NR
Emissions at 60 °C
SumBTEX
-0.45
2.4
-0.51
2.5
-0.36
1.9
NR
a Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
b Fields installed 2004 - 2008 (n=5); 2009 - 2012 (n=10); 2013 - 2016 (n=9)
0 SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
d Statistical tests performed using ln-transformed measurement values.
e NR= Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
211
-------
Figure 4-53 illustrates the distributions in 60 °C emission factor measurement results for recycling
plants and across both the indoor/outdoor and installation age groups to provide a more global
illustration of differences among characteristic categories for chemicals in tire crumb rubber and tire
crumb rubber infill. Average recycling plant emission factors are generally higher than those for the
indoor fields, which in turn are generally higher than those the outdoor fields.
Formaldehyde Benzothiazole
Recytiog Plan*
Indoor f«U*
200
150
.c
C100
50
0
Outdoc
I
T
2010 2009 • 2012 200*-2008 2 013 - 2016 2009 - 2012 2004 - 2006
Age Group
2016 2009 - 2012 2004 - 20C8 2011 -2016 2009-20V2 2004 - 2006
Age Group
Temperalufe»60X
Methyl Isobutyl Ketone
Temperature'SCTC
Styrene
0.5
o.o
¦&80
160-
120-
40-
Age Group Age Group
Figure 4-53. Comparison of VOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber from recycling plants and tire crumb rubber infill composite
samples from synthetic turf fields by age group for formaldehyde, benzothiazole,
methyl isobutyl ketone, and styrene. [VOC = Volatile organic compound]
4.10.3.4 SVOC Emission Factors
Table 4-88 shows results for differences in mean 25 °C and 60 °C emission factors for select SVOCs
analyzed by GC/MS/MS for tire crumb rubber infill collected at outdoor fields in three different
installati on age groups. At 60 °C there was an apparent trend of decreasing emission factors with older
field installation age group.
212
-------
Table 4-88. Comparison of Select SVOC Emission Factors in Tire Crumb Rubber Infill Collected from Outdoor Synthetic Turf Fields in Three Field
Installation Age Groups3
Emissions Test
Analytc
Fields Installed
2004 - 2008
Mean (ng/g/h)
Fields Installed
2004 - 2008
Standard
Deviation
(ng/g/h)
Fields Installed
2009-2012
Mean (ng/g/h)
Fields Installed
2009-2012
Standard
Deviation
(ng/g/h)
Fields Installed
2013-2016
Mean (ng/g/h)
Fields Installed
2013-2016
Standard
Deviation
(ng/g/h)
F-test
p-valucbl
Emissions at 25 °C
Phenanthrene
0.0064
0.023
0.027
0.038
0.013
0.070
NR
Emissions at 25 °C
Suml5PAH
0.63
0.29
0.49
0.67
0.61
0.58
0.3117
Emissions at 25 °C
Benzothiazole
0.065
0.14
0.70
0.46
3.1
3.7
NR
Emissions at 25 °C
Dibutyl phthalate
0.076
0.34
0.16
0.38
0.021
0.37
NR
Emissions at 25 °C
Aniline
0.011
0.065
0.00092
0.084
0.21
0.26
NR
Emissions at 25 °C
4-tert-Octylphenol
0.010
0.044
0.0012
0.12
1.6
5.0
NR
Emissions at 60 °C
Plienanllircne
0.0023
0.095
0.15
0.17
0.28
0.27
NR
Emissions at 60 °C
Fluoranlhene
0.059
0.037
0.11
0.091
0.13
0.092
NR
Emissions at 60 °C
Pyrene
0.12
0.05
0.19
0.13
0.26
0.16
NR
Emissions at 60 °C
Suml5PAH
0.54
0.029
0.97
0.48
1.3
0.8
0.0774
Emissions at 60 °C
Ben/.othia/.ole
2.4
1.1
6.0
5.8
17
14
NR
Emissions at 60 °C
Dibutyl phlhalalc
-0.14
0.11
0.21
0.53
0.14
0.40
NR
Emissions at 60 °C
Aniline
0.17
0.096
0.48
0.43
1.4
1.4
NR
Emissions at 60 °C
4-tcrl-Oclylphenol
0.47
0.37
2.9
3.6
4.0
2.9
NR
a Fields installed 2004 - 2008 (n=5); 2009 - 2012 (n=10); 2013 - 2016 (n=10)
b Statistical tests performed using ln-transformed measurement values.
0 NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
213
-------
Figure 4-54 illustrates the distributions in 60 °C emission factor measurement results for recycling
plants and across both the indoor/outdoor and installation age groups to provide a more global
illustration of differences among characteristic categories for chemicals in tire crumb rubber and tire
crumb rubber infill. Average recycling plant emission factors are generally higher than those for the
indoor fields, which in turn are generally higher than those the outdoor fields.
Pyrene Sum15PAH
Temperaturea60'C Temperature=60"C
0.25
Roeyamo Fhnw Inflow
Q
J—,
201(1 2009 - 2012 20W-2008 2013 - 2016 2009 - 2012 2004 • 2008
Age Group
Temperature=60'C
Benzothiazole
OiMoot Fie&sj
2016 2009 - 2012 2004 - 2008 2013-2016 2009 - 2012 20Ot • 2006
Age Group
4-tert-Octylphenol
TemperaUife=60'C
Rocyciina Plants Ifxtoc* Fields J OuMOOfFwWa
2009-2012 2004-2008 2013-2016 2009 - 2012 2004 - 2006
2009 - 2012 2004 - 2008 2013 - 2016 2009 - 2012 200* • 2008
Age Group Age Group
Figure 4-54. Comparison of SVOC 60 °C emission factor results (ng/g/h) between tire
crumb rubber from recycling plants and tire crumb rubber infill composite samples
from synthetic turf fields by age group. Results for fields are shown separately for indoor and
outdoor fields in two or three installation age groups for pyrene, the sum of 15 PAHs,
benzothiazole, and 4-tert-octylphenol. [SVOC = Semivolatile organic compound; Suml5PAH = Sum of
15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene,
Benzo(b)fluoranthene, Benzolghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene]
4.10.4 Decay Rates of SVOCs Over Time at Outdoor Fields
Data collected in this study afforded further opportunity to explore relationships between field age and
the concentration of chemicals associated with tire crumb rubber infill at outdoor fields. Samples were
collected at 25 outdoor fields with installation dates ranging from 2004 through 2016, giving a 12-year
range of field ages to examine changes in extractable SVOC concentrations over time. Modeled
relationships between six extractable PAH concentrations, assumed to be exponentially distributed, and
214
-------
years since installation are shown graphically as curves in Figure 4-55. The PAH concentrations in
outdoor field composite samples and average concentration of the chemicals in recycling plant samples
are shown plotted against years in the figure. Concentrations and modeled relationships for three
phthalates and three other rubber-associated chemicals are similarly shown in Figure 4-56. For all
chemicals except bis(2-ethylhexyl) phthalate, there was an apparent trend of decreasing chemical
concentration with increasing years since field installation.
0.3-
CT>
I 0.2-
E
0.1 -
0.0
0 1 2 3 4 5 6 7 3 9 10 11 12 13
Years Since Field Installation
10-
8-
4 -
2-
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
6 -
4-
O)
|
E
2-
0 -
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
Ffuorene
| • Recycling Plant • Outdoor Synthetic Turf Field
Fluoranthen©
I • Recycling Plant ~ Oiffdoor Synthetic Turf FlelT
Chrysene
I • Recycling Fjant • Outdoor Synthetic Turf Field
Benzo(a)pyrene
I • Recycling Plant • Outdoor Synthetic Turf Field
Years Since Field Installation
I • Recycling Plant • Outdoor Synthetic Turf Field |
[• Recycling Plant • Outdoor Synthetic Turf Field
Phenanthrene
Pyrene
2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
Years Since Field Installation
Figure 4-55. Concentrations of select extractable PAHs in outdoor field composite tire crumb rubber
infill samples versus years since field installation. The average concentration for the recycling plant tire
crumb rubber is also shown on each graph as a zero point for time. The modeled relationships between
the concentrations and years are shown as curves. [PAH = Polycyclic aromatic hydrocarbons]
215
-------
Aniline
4
[• Recycling Plant • OutdoorSyntlietic Turf Field
3
2
1
0
0 1 2 3 4 5 6 7 8 9 ID 11 12 13
Years Since Field installation
80 -
Benzothiazole
• [• Recycling Plant • Outdoor Synthetic Turf Field 1
60
1
o
rt
6n/6iu
*
20 -
•
• -
! Pi , * . _ . L .
4—i—i—i—i—i—i i—i—i—i—i—i—p
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
4-tert-Octylphenol
30
I • Rtcyellna Plant • Outdoor Synthetic Turf Field
20-
10-
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
Dibutylphthalate
2.5
]'• Recycling Plant • Outdoor Synthetic Turf Field
2.0
cn
e
0.5
0.0 -
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
Benzyl butyl phthalate
1.50 -
• [ • Recycling Plant • Outdoor Synthetic Turf Field
1.25 -
1.00 -
\ •
\ •
o>
\
%, 0.75 -
*\ * *
•
&
• • N.
0,50-
• •
• "x
0.25 -
• t "
0.00
• • •
IIII I4IRIIIIVI
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
Bis(2-ethylhexyl)phthalate
100
• Recycling Plant • Outdoof Synthetic Turf Field |
80-
/
60-
• /
%
• . *
E
40 -
20 -
- * • *
0 -
•Si* *
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Years Since Field Installation
Figure 4-56. Concentrations of select extractable phthalates and other SVOCs in outdoor field composite
tire crumb rubber infill samples versus years since field installation. The average concentration for the
recycling plant tire crumb rubber is also shown on each graph as a zero point for time. The modeled
relationships between the concentrations and years are shown as curves. [SVOC = Semivolatile organic
compound]
216
-------
The shapes of the curves vary appreciably across the chemicals shown in Figures 4-55 and 4-56. Some
chemicals such as benzothiazole, aniline, 4-tert-octylphenol, and fluorene show an apparent very rapid
initial decrease in concentrations, compared to average concentrations measured in recycling plant
samples, with a more gradual decrease at longer time periods. Other chemicals such as fluoroanthene
and pyrene show a more gradual initial decline and an apparent exponential decay function that is often
observed for chemical emissions from materials. Benzo[a]pyrene, on the other hand, appears to have a
nearly linear decrease in concentration over time. Finally, the concentrations of bis(2-ethylhexyl)
phthalate have considerable variability but, in general, appear to increase in concentrations over time.
This could be a result of sources of bis(2-ethylhexyl) phthalate other than the tire crumb rubber infill
contributing chemical to the rubber over time.
Decay half-lives were estimated for these chemicals based on an assumed exponential decay function.
Estimated half-lives are shown in Table 4-89 with and without the average tire recycling plant
concentration included as a 'zero' time point. Estimated decay half-lives ranged from 2.3 years for
benzothiazole to 20 years for benzo[a]pyrene with the average recycling plant concentration included.
Information for several chemical properties are also included in Table 4-89 because factors such as
vapor pressure, water solubility, and octanol:water partition coefficients may help explain differences in
the changes in concentration over time. In general, the lighter and more volatile SVOCs had shorter
decay half-lives and more rapid initial decreases in concentrations when compared to average
concentrations for tire crumb rubber collected at recycling plants. There could also be a water solubility
relationship for chemicals like aniline, benzothiazole, and 4-tert-octylphenol having very rapid initial
decreases in concentrations at outdoor fields. There may be an initial extraction effect of rainwater
and/or irrigation water contributing to the rapid reduction of concentrations of the more water-soluble
chemicals at the rubber particle surfaces. Benzo[a]pyrene, with its very low vapor pressure and water
solubility and relatively high octanol:water partition coefficient, exhibited the longest decay half-life.
There are several limitations to these decay half-life estimates, including relatively small sample sizes.
There is considerable variability for some chemicals that may be related to factors such as differences in
initial concentrations, weather and climate effects for heat and rain or irrigation, field maintenance
practices (including possible degradation of organic analytes with oxidative disinfectants), activity levels
and types, and refreshment with new tire crumb rubber infill material. The data set is too small to
support further assessment of these factors. The decay half-life estimation also relies on an assumed
exponential decay function. While an exponential function fit most chemical patterns reasonably well,
the very rapid initial decrease for some chemicals suggests the possibility of different chemical/physical
processes at early and later times that may have different underlying time distributions. Finally, it is also
important to acknowledge that differences in concentrations in synthetic field infill samples could be a
result of differences in the original concentrations of chemicals in tires at different times. Longitudinal
studies at individual fields would be needed to confirm that weathering effects are primarily responsible
for these differences.
217
-------
Table 4-89. Estimated Time Decay Half-lives and Chemical Properties for Selected Extractable SVOCs in Tire
Crumb Rubber Infill Samples Collected at Outdoor Fields with a Range of Ages a b
Analvtc
Estimated
Half-Life
(years),
including
average
recycling plant
Estimated Half-
Life (years),
not including
average
recycling plant
Molecular
Weight
(g/mol)
Boiling
Point
(°C)
Vapor
Pressure
(mm Hg)
Solubility
in Water
(mol/L)
LogP:
Octanol-
Water
Fluorene
2.4
2.8
166
295
6.0E-04
1.1E-05
4.2
Phenanthrene
3.1
3.3
178
339
1.2E-04
6.4E-06
4.5
Fluoranthene
5.3
5.2
202
380
9.2E-06
1.1E-06
5.2
Pyrene
5.0
5.1
202
399
4.5E-06
6.7E-07
4.9
Chrysene
8.1
9.1
228
448
6.2E-09
8.8E-09
5.8
Benzo[a]pyrene
20
19
252
495
5.5E-09
6.4E-09
6.1
Aniline
3.9
5.7
93
184
4.9E-01
3.9E-01
0.9
Benzothiazole
2.3
2.7
135
230
4.7E-020
3.2E-02
2.0
4-tert-octylphenol
3.3
4.2
206
280
4.8E-04
3.1E-04
4.8
Dibutyl phthalate
3.5
3.3
278
340°
2.0E-05
4.0E-050
4.5
Benzyl butyl phthalate
3.0
2.9
312
370
8.2E-06
8.6E-06
4.7
Bis(2-ethylhexyl)
phthalate
-4.4d
-4.4d
391
308
1.4E-07
1.1E-07
7.6
aField ages ranged from 0.5 to 12 years based on reported year of field installation.
b Chemical properties from EPA Chemical Dashboard; average experimental values shown unless otherwise noted.
0 No experimental value reported; predicted average value used.
d Average concentrations were higher in field samples than recycling plant samples and appeared to increase at fields over
time.
These results, along with the chamber emission factor temperature differences (section 4.7.2) and
chamber time series tests (Appendix J), may provide some insight on the dynamic processes for releases
of organic chemicals from the tire crumb rubber. There appears to be a difference between chemicals at
the surface of the rubber material and chemicals found in deeper rubber particle layers. It may be
possible that the production of the tire crumb rubber at the recycling plant opens fresh new surfaces
where chemicals become available for relatively rapid emission into the air and extraction - whether by
rainwater at the fields or by solvent in laboratory experiments. Effective surface depletion rates may be
slowed at first by emitted chemicals being rapidly absorbed again on the surfaces of neighboring, tightly
bunched particles in the storage sacks (or in sample collection bottles). Once on the field, the exchange
between neighboring particle surfaces may continue for the layer of infill applied to the field, with some
emitted chemicals entering the air above the field being permanently lost. Shortly after deployment on
the field, rain events or irrigation may rapidly extract the more water-soluble chemicals at the particle
surface throughout the infill layer. A more rapid phase of initial emission dynamics may be governed
predominantly at first by the solid:air partition coefficient. Once the surface layer is sufficiently depleted
of the chemical, a slower emission rate may be observed as the surface needs to be replenished with
chemical from deeper layers in the rubber particle. At that time, the chemical solid mass diffusion
coefficient may become the more dominant dynamic rate limiting step, as more chemical has to diffuse
to the particle surface before it becomes available for emission or extraction. The dynamics for each
chemical will depend on its surface:air partition coefficient, mass diffusion coefficient, vapor pressure,
and water solubility, along with the conditions at the field and surface to volume particle ratios.
Additional laboratory work would be required to better understand these dynamics across chemicals, and
218
-------
how these dynamics may affect the amounts of chemicals available for exposure under different time
and condition scenarios.
The insight on dynamic processes for organic chemical in tire crumb rubber also helps inform
interpretation of results in this report. For example, based on the concentration derived from the solvent
extract and the emission factors measured for the more volatile organics such as benzothiazole, one
might estimate that the chemical would be fully depleted from the material in less than a year. However,
complete depletion is clearly not occurring over that time scale. First, it is likely that the solvent
extraction is only removing chemicals from near the surface of the rubber particles and not from deeper
layers. While this is probably a good measure for understanding the potential for exposures at a given
time point, it likely underestimates the total amount of chemical associated with the rubber on a mg/kg
basis and available for release over many years. Second, the emission factors measured at 24-hour time
points in the chamber tests likely reflect the more rapid period of release from the rubber particle surface
layer and not the slower dynamics that would likely take over at later times when the mass diffusion of
the chemical from deeper particle layers may become the dominant dynamic driver, especially for
material from the recycling plants and newer fields. It may also help explain why the BTEX chemicals
were not generally measured with higher emission factors in 60 °C tests as compared to the 25 °C tests.
If the source of the BTEX chemicals is from atmospheric absorption onto the rubber particle surface, it
is likely that these volatile chemicals will be rapidly emitted over short time periods at high
temperatures. If there are not BTEX compounds deeper in the rubber (or if they are at very low
concentrations in the rubber) then there may be no further emissions (or lower emissions) over time after
they are emitted from the surface. The chamber time series tests reported in Appendix J support this
dynamic scenario.
4.10.5 Geographic Region
Tire crumb rubber infill mean chemical measurement results were compared for synthetic turf fields
organized into four groups, based on U.S. census region. For the statistical test results, p-values are
reported for between-group differences in the cases where all measurement results were > 0 (because the
statistical testing was performed on the log-transformed measurement results). When viewing these
results, it is also important to remember that substantial differences were observed for outdoor versus
indoor fields, and for organic chemicals, modest differences were observed in average concentrations
across age groups. In this section, there is no differentiation between indoor and outdoor fields or field
installation age group, within each geographical region category. Results for linear multivariate
modeling of all three field characteristics are reported in the next sub-section (section 4.10.6).
4.10.5.1 Metals by ICP/MS and XRF
Table 4-90 shows results for differences in mean concentrations of select metals analyzed in acid digests
by ICP/MS and in XRF analyses of tire crumb rubber infill collected at fields in four different U.S.
census regions. There were no statistically significant differences among the groups for any analytes.
Figure 4-57 illustrates the distributions in measurement results across the four geographic region groups
for chromium, cobalt, lead, and zinc.
219
-------
Table 4-90. Comparison of Select Metals in Tire Crumb Rubber Infill Collected at Synthetic Turf Fields in Four U.S. Census Regions3
Analysis'*
Analytcs
Northeast
Mean
(mg/kg)
Northeast
Standard
Deviation
(mg/kg)
South
Mean
(mg/kg)
South
Standard
Deviation
(mg/kg)
Midwest
Mean
(mg/kg)
Midwest
Standard
Deviation
(mg/kg)
West
Mean
(mg/kg)
West
Standard
Deviation
(mg/kg)
F-test
p-value'
ICP/MS Analysis
Arsenic
0.36
0.13
0.33
0.23
0.43
0.29
0.42
0.11
0.2021
ICP/MS Analysis
Cadmium
1.1
0.49
0.75
0.41
1.3
1.2
0.78
0.38
0.1562
ICP/MS Analysis
Chromium
1.9
0.68
1.3
1.1
1.5
0.51
2.0
0.78
NRd
ICP/MS Analysis
Cobalt
110
43
140
55
150
84
150
59
0.3609
ICP/MS Analysis
Lead
20
16
18
13
25
22
34
44
0.5454
ICP/MS Analysis
Zinc
14000
2400
15000
3500
17000
3000
14000
2400
0.1387
XRF Analysis
Chromium
14
2.3
14
2.8
14
O
J.J
13
3.4
0.419
XRF Analysis
Cobalt
29
16
42
16
42
17
40
18
0.2355
XRF Analysis
Lead
38
28
35
20
36
11
37
28
0.94
XRF Analysis
Zinc
29000
6700
34000
7400
37000
6400
33000
6700
0.0767
aNortheast (n=9); South (n=13); Midwest (n=8); West (n=10)
b ICP/MS = Inductively coupled plasma/mass spectrometry; XRF = X-ray fluorescence spectrometry
0 Statistical tests performed using ln-transformed measurement values.
dNR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
220
-------
M
Chromium
N S
Region
w
M
Cobalt
N S
Region
200
O)
o>
en
100
w
Lead
Zinc
160-
120-
O)
Jxl
o) 80-
E
40-
20000
cn
M
16000
E
12000
MNSW MNSW
Region Region
Figure 4-57. Comparison of I CP/MS metal analysis results (mg/kg) between tire
crumb rubber infill composite samples from synthetic turf fields in four U.S.
census regions for chromium, cobalt, lead, and zinc. [ICP/MS = Inductively coupled
plasma/mass spectrometry; M = Midwest; N = Northeast; S = South; W = West]
4.10.5.2 SVOC Extracts by GC/MS/MS and LC/TOFMS
Table 4-91 shows results for differences in mean concentrations of select SVOCs analyzed in solvent
extracts by GC/MS/MS for tire crumb rubber infill collected at fields in four different U.S. census
regions. Fluoranthene and 4-tert-octylphenol showed statistically significant differences across region
groups. In both cases, the average concentration for the West region were lower than the other regions.
For 4-tert-octylphenol, the average concentration in the Midwest region was substantially higher than
those in the other regions. It is important to note that the Midwest region had the largest number of
indoor fields, and higher levels of SVOCs were consistently found for indoor fields versus outdoor
fields. Table 4-92 shows results for differences in mean chromatographic peak area counts of select
SVOCs analyzed in solvent extracts by LC/TOFMS. Figures 4-58 through 4-60 illustrate the
distributions in measurement results across the four geographic region groups for twelve SVOC
analytes.
221
-------
Table 4-91. Comparison of Select SVOC Extracts Analyzed by GC/MS/MS for Tire Crumb Rubber Infill
Collected at Synthetic Turf Fields in Four U.S. Census Regionsa b
Analytes'
Northeast
Mean
(mg/kg)
Northeast
Standard
Deviation
(mg/kg)
South
Mean
(mg/kg)
South
Standard
Deviation
(mg/kg)
Midwest
Mean
(mg/kg)
Midwest
Standard
Deviation
(mg/kg)
West
Mean
(mg/kg)
West
Standard
Deviation
(mg/kg)
F-test
p-value1'
Fluoranthene
5.1
3.4
5.2
2.6
4.9
1.9
2.8
1.3
0.0494
Pyrene
13
8.3
12
5.3
16
4.8
9.9
5.6
0.1743
Benzo[a]pyrene
1.1
0.80
0.80
0.49
0.69
0.27
0.57
0.25
0.1887
Benzo [ghijperylene
1.5
0.37
1.4
0.83
1.1
0.63
1.2
0.57
0.4213
Suml5PAH
33
21
29
12
34
12
22
11
0.1567
Benzothiazole
13
19
8.6
12
15
12
7.7
6.4
0.3539
Dibutyl phthalate
2.0
2.5
1.0
1.1
1.8
1.1
1.4
1.2
0.3835
Bis(2-ethylhexyl)
phthalate
33
26
47
51
45
55
43
36
0.9489
Aniline
0.75
0.75
0.57
0.33
0.98
0.68
0.50
0.31
0.2898
4-tert-octylphenol
8.0
6.7
8.2
11
19
11
6.5
6.6
0.0392
n-Hexadecane
1.3
1.8
0.52
0.90
1.6
1.4
0.68
0.80
0.0665
a SVOC = Semivolatile organic compound; GC/MS/MS = Gas chromatography/tandem mass spectrometry
bNortheast (n=9); South (n=13); Midwest (n=8); West (n=10)
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene,
Benzo[a]pyrene, Benzo(b)fluoranthene, Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene,
Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
d Statistical tests performed using ln-transformed measurement values.
222
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Table 4-92. Comparison of Select SVOC Extracts with Non-quantitative LC/TOFMS Analysis for Tire Crumb Rubber Infill Collected
at Synthetic Turf Fields in Four U.S. Census Regions3,15
Analytc
Northeast
Mean
Area
Counts
Northeast
Area Counts
Standard
Deviation
South
Mean
Area
Counts
South
Area Counts
Standard
Deviation
Midwest
Mean
Area
Counts
Midwest
Area Counts
Standard
Deviation
West
Mean
Area
Counts
West
Area Counts
Standard
Deviation
F-test
p-value1'1
2-mercaptobenzothiazole
3.5E+03
4.0E+03
4.4E+02
5.2E+02
3.7E+03
5.6E+03
7.3E+02
1.5E+03
NR
2-hydroxybenzothiazole
1.0E+05
1.2E+05
6.9E+04
1.1E+05
2.3E+05
1.5E+05
5.1E+04
6.1E+04
NR
cyclohexylamine
9.5E+05
1.1E+06
1.1E+05
1.3E+05
1.0E+06
1.0E+06
1.2E+05
2.0E+05
NR
di-cyclohexylamine
7.0E+06
7.3E+06
8.1E+06
7.9E+06
1.3E+07
1.1E+07
8.9E+06
8.5E+06
0.6126
N-cyclohexyl-N-
methylcyclohexanamine
4.1E+05
5.1E+05
2.0E+05
1.9E+05
2.0E+05
1.9E+05
1.6E+05
1.7E+05
0.591
diisononylphthalate
6.6E+04
1.2E+05
4.6E+04
1.3E+05
3.7E+03
1.6E+04
-8.1E+03
2.4E+03
NR
diisodecylphthalate
1.9E+05
5.7E+05
3.7E+03
2.8E+03
5.8E+03
6.7E+03
9.1E+03
1.3E+04
NR
a SVOC = Semivolatile organic compound; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry
bNortheast (n=9); South (n=13); Midwest (n=8); West (n=10)
0 Statistical tests performed using ln-transformed measurement values.
dNR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
-------
Phenanthrene
M N S W
Region
Pyrene
£ 50
M N S W
Region
Benzo(a)pyrene
Sum15PAH
MNSW MNSW
Region Region
Figure 4-58. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg)
between tire crumb rubber infill composite samples from synthetic turf fields
in four U.S. census regions for phenanthrene, pyrene, benzo[a]pyrene, and the
sum of 15 PAHs. [GC/MS/MS = Gas chromatography/tandem mass spectrometry; SVOC =
Semivolatile organic compound; Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs.
including Accnaphthylcne. Anthracene, Bcn/|a|anthraccne. Benzo[a]pyrene, Benzo(b)fluoranthene,
Bcnzo|ghi|petylcnc. Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene,
Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenantlirene, Pyrene; M = Midwest; N =
Northeast; S = South; W = West]
224
-------
40
c»
CTI
E
20
Benzothiazole
M N S W
Region
4-tert-Octylphenol
30
O)
M
N S
Region
w
150
oi100
01
£
50
Bis(2-ethylhexyl) phthalate
i
M
N S
Region
w
CD
O)
e
M
n-Hexadecane
=i
N S
Region
w
Figure 4-59. Comparison of GC/MS/MS extract SVOC analysis results (mg/kg)
between tire crumb rubber infill composite samples from synthetic turf fields in
four U.S. census regions for benzothiazole, 4-tert-octylphenol, bis(2-ethylhexyl)
phthalate, and n-hexadecane. [GC/MS/MS = Gas chromatography/tandem mass spectrometry;
SVOC = Semivolatile organic compound; M = Midwest; N = Northeast; S = South; W = West]
225
-------
2-mercaptobenzothiazo!e
2-hydroxybenzothiazole
15000
JS 10000
2e+05
5000
1e+05
0e+00
M N S
Region
w
M N S W
Region
cyclohexylamine
di-cyclohexylamine
(/)
'
C
3
o
O
CIS
0)
<
2e+06
0e+00
M N S W
Region
3e+07
cn
c 2e+07
D
O
O
03
0)
<1e+07
0e+00
M N S W
Region
Figure 4-60. Comparison of LC/TOFMS extract SVOC non-quantitative positive ionization
analysis results between tire crumb rubber infill composite samples from synthetic turf fields
in four U.S. census regions for 2-mercaptobenzothiazole, 2-hydroxybenzothiazole,
cyclohexylamine, di-cyclohexylamine. [LC/TOFMS = Liquid chromatography/time-of-flight mass
spectrometry; SVOC = Semi volatile organic compound; M = Midwest: N = Northeast; S = South: W = West]
Overall, it is difficult to distinguish regional patterns in the SVOC analysis results. This may be due in
part to uneven distributions of indoor fields across regions and distributions of outdoor field age. Ideally,
the outdoor fields might be placed into climatic zones for assessing the relevance of heat, sun and
rainfall. However, the number of outdoor fields is too small to support a regional analysis based on
multiple climatic zones. There might also be regional differences in the types of tires that are recycled to
produce infill material, but the number of recycling plants in each region was too small to support a
regional difference analysis. These results do suggest that regional differences are unlikely to be the
most important characteristic underlying differences in SVOC levels in tire crumb rubber infill at
synthetic turf fields.
226
-------
4.10.5.3 VOC Emission Factors
Figure 4-61 illustrates the distributions in 60 °C emission factor results across the four geographic
region groups for form aldehyde, benzothiazole, methyl isobutyl ketone, and styrene. Differences in
mean 25 °C and 60 °C emission factors for select VOCs analyzed by GC/TOFMS are shown in Table
4-93 for tire crumb rubber infill collected at fields in four different U.S. census regions. Methyl isobutyl
ketone and benzothiazole showed statistically significant differences in 60 °C emission factors by U.S.
census region. In both cases, the average concentration for the Midwest region were higher than other
groups. It should be noted that there was a higher proportion of indoor fields in the Midwest region and
that higher emission factors were observed for indoor fields than for outdoor fields. Many of the
emission factor measurement results, particularly for the 25 °C tests, were not above the method
detection limit or chamber background levels.
Formaldehyde
T emperature=6(rc
Region
120
Benzothiazole
T emperature=60 °C
60
M N S
Region
100
Methyl Isobutyl Ketone
T emperature=60 °C
Styrene
Temperature=60"C
MNSW MNSW
Region Region
Figure 4-61. Comparison of VOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber infill composite samples from synthetic turf fields in four U.S.
census regions for formaldehyde, benzothiazole, methyl isobutyl ketone, and styrene.
| VOC = Volatile organic compound; M = Midwest; N = Northeast; S = South; W = West]
227
-------
Table 4-93. Comparison of Select VOC Emission Factors for Tire Crumb Rubber Infill Collected at Synthetic Turf Fields in Four U.S. Census
Regions3,15
Emissions Test
Analvtes'
Northeast
Mean
(ng/g/h)
Northeast
Standard
Deviation
(ng/g/h)
South
Mean
(ng/g/h)
South
Standard
Deviation
(ng/g/h)
Midwest
Mean
(ng/g/h)
Midwest
Standard
Deviation
(ng/g/h)
West
Mean
(ng/g/h)
West
Standard
Deviation
(ng/g/h)
F-test
p-value'1'
Emissions at 25 °C
Benzothiazole
23
31
15
22
46
38
21
18
NR
Emissions at 25 °C
o-Xylene
0.068
0.12
0.005
0.081
0.040
0.097
0.030
0.068
NR
Emissions at 25 °C
SumBTEX
0.17
0.53
0.12
0.89
0.37
0.61
0.63
1.1
NR
Emissions at 60 °C
Formaldehyde
20
18
12
4.9
19
4.7
16
2.3
NR
Emissions at 60 °C
Melhvl isobulvl ketone
37
31
33
19
67
26
38
22
0.0267
Emissions at 60 °C
Bcn/.olhia/.olc
37
43
44
38
81
38
62
32
0.0393
Emissions at 60 °C
Slyrcnc
0.57
0.44
0.21
0.30
0.78
0.42
0.41
0.34
NR
Emissions at 60 °C
Toluene
0.032
0.18
0.074
0.35
0.29
0.30
0.22
0.29
NR
Emissions at 60 °C
Elhylben/.ene
-0.074
0.24
-0.20
0.17
0.038
0.20
-0.023
0.25
NR
Emissions at 60 °C
m/p-Xylene
0.20
0.83
-0.34
0.66
0.78
0.97
0.60
1.2
NR
Emissions at 60 °C
o-Xylene
-0.31
0.46
-0.72
0.47
-0.19
0.56
-0.024
0.87
NR
Emissions at 60 °C
SumBTEX
-0.31
1.8
-1.2
1.7
1.0
2.0
0.67
2.5
NR
a Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
bNortheast (n=6-9); South (n=13); Midwest (n=8); West (n=9-10)
0 SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
d Statistical tests performed using ln-transformed measurement values.
e NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
228
-------
4.10.5.4 SVOC Emission Factors
Figure 4-62 illustrates the distributions in 60 °C emission factor results across the four U.S. census
regions for pyrene, the sum of 15 PAFIs, benzothiazole, and 4-tert-octylphenol. Differences in mean 25
°C and 60 °C emission factors for select SVOCs analyzed by GC/MS/MS are shown in Table 4-94 for
tire crumb rubber infill collected at fields in four different U.S. census regions. The sum of 15 PAHs
showed statistically significant different 25 °C emission factors, with the highest average concentration
in the South and lowest average concentration in the West. However, this relationship was not observed
for the 60 °C sum of 15 PAH emission factors. Many of the emission factor measurement results,
particularly for the 25 °C tests, were not above the method detection limit or chamber background
levels.
Pyrene Sum15PAH
Temperature=60°C Temperature=6CTC
£ 0.50
N S
Region
N S
Region
Benzothiazole
Temperature=60<'C
4-tert-Octylphenol
Temperature=6Q°C
c 100
N S
Region
N S
Region
Figure 4-62. Comparison of SVOC 60 °C emission factor results (ng/g/h) between
tire crumb rubber infill composite samples from synthetic turf fields in four U.S.
census regions for pyrene, the sum of 15 PAHs, benzothiazole, and 4-tert-octylphenol.
[SVOC = Semivolatile organic compound; Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs,
including Acenaphthylene, Antliracene. Benz[a]anthracene, Benzo[a]pyrene. Benzo(b)fluoranthene,
Benzo[ghi|perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene. Fluoranthene, Fluorene,
Indeno(l,2,3-cd)pvrene, Naphthalene, Phenantlirene, Pyrene; M = Midwest; N = Northeast; S = South;
W = West]
229
-------
Table 4-94. Comparison of Select SVOC Emission Factors for Tire Crumb Rubber Infill Collected at Synthetic Turf Fields in Four U.S. Census
Regions3,15
Emissions Test
Analvtes'
Northeast
Mean
(ng/g/h)
Northeast
Standard
Deviation
(ng/g/h)
South
Mean
(ng/g/h)
South
Standard
Deviation
(ng/g/h)
Midwest
Mean
(ng/g/h)
Midwest
Standard
Deviation
(ng/g/h)
West
Mean
(ng/g/h)
West
Standard
Deviation
(ng/g/h)
F-test
p-value'1'
Emissions at 25 °C
Phenanthrene
0.021
0.074
0.040
0.055
0.028
0.025
0.0056
0.011
NR
Emissions at 25 °C
Suml5PAH
0.71
0.37
0.92
0.97
0.37
0.23
0.35
0.15
0.0403
Emissions at 25 °C
Benzothiazole
4.8
6.5
2.8
3.6
7.9
6.7
2.5
2.9
NR
Emissions at 25 °C
Dibutyl phthalate
0.095
0.41
0.15
0.37
-0.27
0.27
-0.11
0.33
NR
Emissions at 25 °C
Aniline
0.25
0.38
0.19
0.28
0.82
0.57
0.24
0.36
NR
Emissions at 25 °C
4-tert-octylphenol
1.7
4.6
1.3
4.4
0.23
0.16
0.061
0.082
NR
Emissions at 60 °C
Phenanthrene
1.0
1.2
0.35
0.44
0.71
0.57
0.35
0.36
NR
Emissions at 60 °C
Fluoranthene
0.23
0.15
0.16
0.1
0.13
0.081
0.11
0.093
NR
Emissions at 60 °C
Pyrene
0.42
0.29
0.29
0.19
0.26
0.18
0.20
0.14
NR
Emissions at 60 °C
Suml5PAH
3.2
3.2
1.5
1.0
2.4
1.6
1.2
0.7
0.4212
Emissions at 60 °C
Ben/.olhia/.ole
49
75
15
15
70
64
16
12
NR
Emissions at 60 °C
Dibulvl phlhalalc
0.14
0.34
0.27
0.31
-0.037
0.45
0.13
0.55
NR
Emissions at 60 °C
Aniline
6.2
8.1
1.0
1.2
6.5
5.3
1.9
2.2
NR
Emissions at 60 °C
4-lerl-oclylphenol
6.3
6.5
6.2
6.4
7.3
5.1
3.8
3.5
NR
a Several results are reported as negative values. This is a result of the subtraction of chamber background values from the sample measurement results. Although this does
not represent a physical reality, the negative results are retained as part of the distribution of corrected results.
bNortheast (n=9); South (n=13); Midwest (n=8); West (n=10)
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene
d Statistical tests performed using ln-transformed measurement values.
e NR = Not Reported; one or more measurement results were < 0, precluding ln-transformed testing for the complete data set.
230
-------
4.10.6 Linear Model Analysis for Field Characteristics
Linear models were fitted to further examine relationships and interactions for selected chemical
measurement results for three primary synthetic turf field characteristics examined in this study -
outdoor vs. indoor facility type; field installation age group, and U.S. census region field location. Table
4-95 gives p-values for all main effect and interaction terms included in the final model for each of the
chemical substances and the p-value for the corresponding Shapiro-Wilk test for normality. For
example, the final model for log-transformed lead found statistically significant associations for the
main effect of age group and the sole interaction term of indoor/outdoor and region, indicating a
differential effect of indoor/outdoor by region.
Interpretation of the relationships illustrated by the models given in Table 4-95 focuses only on the
fields included in this study, an important caveat. The study design for the 40 fields sampled is not a
probability-based sample, potentially resulting in selection bias and lack of representativeness for the
target population (Lohr, 2009). The 40 fields sampled also were not balanced across age group,
indoor/outdoor, and Census region categories; this lack of balance results in sparsity for some
combinations of the categorical data. These features limit generalizability of the model results.
For the 40 fields studied, over half of the chemical substance composite concentration relationships
examined in this analysis are characterized by statistically significant combinations (interactions) of the
categorical model terms:
• Seven (7) of the 15 models with interaction terms include an interaction with indoor/outdoor. A
total of 14 models includes the indoor/outdoor category in a model term.
• Six (6) of the 15 models with interaction terms include an interaction with age group. A total of
12 models includes the age group category in a model term.
• Ten (10) of the 15 final models include interaction terms, and all but 1 of these 10 models
includes an interaction with region. Of the remaining 6 models, 4 include the main effect of
region. A total of 13 models includes the region category in a model term.
Consequently, only six of the final models are limited to 1 or more main effect model terms. For a
majority of the chemical substances analyzed using linear models, their relationships with the categories
of age group, indoor/outdoor, and Census region are best characterized using combinations. The
generalizability of these relationships is highly uncertain, but for the fields sampled in this study, all
three primary field characteristics apparently contributed to the overall variability in chemicals
associated with the tire crumb rubber infill.
231
-------
Table 4-95. P-values for Final Linear Models of Select Measurement Results for Three Synthetic Turf Field Characteristics - Outdoor vs. Indoor Field,
Field Installation Age Category, and U.S. Census Region Field Location"
Analysis'*
Analytc'
•Main
Effect
Term -
Age
Group
Main
Effect
Term -
Indoor/
Outdoor
Main
Effect
Term -
Region
Interaction
Term -
Age Group
by Indoor/
Outdoor
Interaction
Term -
Age Group
by Region
Interaction
Term
Indoor
Outdoor by
Region
Interaction
Term -
Age Group by
Indoor/ Outdoor
by Region
Shapiro-
Wilk
p-valuc
ICP/MS Acid Digestion
Cobalt
0.0003
0.565
0.2303
N/A
N/A
0.0627
N/A
0.5093*
ICP/MS Acid Digestion
Lead
0.0375
0.9629
0.0757
N/A
N/A
0.0205
N/A
0.2312*
ICP/MS Acid Digestion
Zinc
0.0041
0.6605
0.0064
N/A
N/A
0.0252
N/A
0.4851
GC-MS Solvent Extraction
Pvrcnc
0.0077
<.0001
N/A
0.0135
N/A
N/A
N/A
0.7059
GC-MS Solvent Extraction
Suml5PAH
0.0119
<.0001
0.0341
N/A
N/A
N/A
N/A
0.9571
GC-MS Solvent Extraction
Bcn/.olhia/.olc
0.0001
<.0001
N/A
N/A
N/A
N/A
N/A
0.9774*
GC-MS Solvent Extraction
4-tcrl-oclylphcnol
0.0027
<.0001
0.0591
0.0018
0.1670
0.7340
0.0141
0.3479*
GC-MS Solvent Extraction
Bis(2-clhylhcxvl)
phlhalalc
0.0920
0.0131
0.0378
N/A
0.0520
N/A
N/A
0.3710
Chamber SVOC Emission
Factors at 60°C
Pyrene
<0001
<.0001
<.0001
0.2486
0.0018
0.0010
0.0020
0.1752
Chamber SVOC Emission
Factors at 60°C
Suml5PAH
0.0019
<.0001
0.0001
N/A
0.0024
N/A
N/A
0.3735*
Chamber SVOC Emission
Factors at 60°C
Benzothiazole
<0001
<.0001
0.7447
N/A
N/A
0.0188
N/A
0.4736*
Chamber SVOC Emission
Factors at 60°C
4-tert-octylphenol
N/A
<.0001
0.0486
N/A
N/A
N/A
N/A
0.2104
Chamber VOC Emission
Factors at 60°C
Benzothiazole
N/A
<.0001
N/A
N/A
N/A
N/A
N/A
0.1261*
Chamber VOC Emission
Factors at 60°C
Methyl isobutyl ketone
N/A
N/A
0.0111
N/A
N/A
N/A
N/A
0.1788
232
-------
Table 4-95 Continued
Analvsisb
Analvtc'
Main
Main
Main
Interaction
Interaction
Interaction
Interaction
Shapiro-
Effect
Effect
Effect
Term -
Term -
Term -
Term -
Wilk
Term -
Term
Term -
Age Group
Age Group
Indoor/
Age Group by
p-value
Age
Indoor
Region
bv Indoor/
by Region
Outdoor bv
Indoor/ Outdoor
Group
Outdoor
Outdoor
Region
by Region
Chamber VOC Emission
Styrene
0.3634
<.0001
0.0496
N/A
0.0037
N/A
N/A
0.1360
Factors at 60°C
Chamber VOC Emission
SumBTEX
N/A
N/A
0.0434
N/A
N/A
N/A
N/A
0.2097
Factors at 60°C
11 P-valucs for all main effect and interaction terms included in final model for each analyte and corresponding Shapiro-Wilk (S-W) test for normality; model fitting used
backward elimination starting with the full factorial model and selection based on p-values (a=0.05), Akaike information criterion (AIC) statistic, and model residuals.
b ICP/MS = Inductively coupled plasma/mass spectrometry; GC/MS = Gas chromatography/mass spectrometry; SVOC = Semivolatile organic compound; VOC =
Volatile organic compound; N/A = Not applicable; main effect or interaction term not included in final model
0 Suml5PAH = Sum of 15 of the 16 EPA 'priority' PAHs, including Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo(b)fluoranthene,
Benzo[ghi]perylene, Benzo(k)fluoranthene, Chrysene, Dibenz[a,h]anthracene, Fluoranthene, Fluorene, Indeno(l,2,3-cd)pyrene, Naphthalene, Phenanthrene, Pyrene;
SumBTEX = Sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene
*Model fitted for log-transformed concentration as indicated by Shapiro-Wilk test statistic; otherwise concentration not transformed.
233
-------
4.11 Suspect Screening Chemical Analysis
Suspect screening is a technique used to tentatively identify chemicals using mass spectrometry methods
when there is prior information about the potential for those chemicals to be present in a medium of
interest. Many SVOC chemicals (Table 3-5) were proposed for suspect screening by LC/TOFMS
analysis based on previous reports (compiled in the Literature Review and Data Gaps Analysis,
Appendix C) that they were observed in tire crumb rubber analysis studies or because they were
identified as potentially being used (or are transformation products or degradates of chemicals being
used) in tire manufacturing. Chemicals were selected where mass spectra were available to identify the
presence of the chemical.
The samples were analyzed in both positive and negative ionization modes and subjected to a molecular
feature extraction (MFE) algorithm to identify peaks for further exploration. Features identified were
compared to a personal compound database list (PCDL) created using spectra for the suspect screening
chemicals in the U.S. EPA's Distributed Structure-Searchable Toxicity (DSSTox) database. Chemicals
matching within 5 ppm of the suspect chemical according to accurate mass and scoring >80% in spectra
match comparisons were deemed as a provisional match.
In some cases, the same chemical identity was reported multiple times in the same sample. This was due
in part because chemical isomers have the same accurate mass and may generate the same or very
similar spectra that are matched to a single library reference spectrum. In many cases, it was observed
that the same chemical match was reported for spectra produced at different chromatographic retention
times, making the presence of isomers more likely. And, of course, some repeated chemical matches
may be the result of incorrect matching identifications. In order to be reported, average area counts
within at least one of the three sample types (recycling plant, indoor field, or outdoor field) had to be
more than three times greater than the average area counts in the method blanks for a tentatively-
identified chemical.
Suspect screening chemicals tentatively identified in tire crumb rubber solvent extract samples from
recycling plants and tire crumb rubber infill solvent extract samples from synthetic turf fields are shown
in Table 4-96 for positive ionization mode analysis and Table 4-97 for negative ionization mode.
Chemicals previously reported in targeted analyses were not included in these tables.
Fifteen unique chemicals were tentatively identified in the positive ionization analysis. Multiple
instances of 2,2,4-Trimethyl-l,2-dihydroquinoline (TMQ), a tire rubber antioxidant chemical, were
observed in recycling plant and field samples. Other potential tire rubber chemicals, such as N,N'-
Diphenyl-p-phenylenediamine (DPPD), N,N'-Ditolyl-p-phenylenediamine (DTPD), N-tert-Butyl-2-
benzothiazolesulfenamide (TBBS,) and n-Isopropyl-n'-phenylparaphenylenediamine (IPPD), with
reported uses as accelerators, antioxidants, or antiozonants, were observed widely in recycling plant
samples and occasionally to often in the synthetic turf field samples. The chemical 1,3-Dicyclohexylurea
may be used in anti-exposure cracking (antiozonant) formulations and was observed in all sample types.
Hexa(methoxymethyl)melamine has been reported as an adhesion promotor for rubber compounds and
was observed in all sample types.
Eight chemicals were tentatively identified in the negative ionization analysis. Six of these chemicals
were observed in many of the recycling plant samples and at lower frequencies in synthetic turf field
samples. The chemical 2,2'-Methylene-bis-(4-methyl-6-tert-butylphenol) may be used as an antioxidant,
while dehydroabietic acid and fatty acids are reported as used in tire manufacturing. The compound 3,5-
di-tert-butyl-4-hydroxybenzaldehyde was observed in many samples and may be present as a
transformation product of the antioxidant butylated hydroxytoluene (BHT).
234
-------
Table 4-96. Tentative Suspect Screening Chemical Identifications Through Positive Ionization LC/TOFMS Analysis of Tire Crumb Rubber Solvent
Extracts3,15
Tentative Chemical Name
CAS
Number'
Recycling Plants
Frequency'1
Recycling Plants
Mean Area
Indoor Fields
Frequency'1
Indoor Fields
Mean Area
Outdoor Fields
Frequency'1
Outdoor Fields
Mean Area
Blanks
Frequency'1
1,3 -Dicyclohexylurea
2387-23-7
13
3.23E+06
20
4.08E+06
5
5.17E+05
0
Dehydroabietic acid
1740-19-8
24
3.06E+05
19
5.31E+05
30
3.74E+05
0
2,2,4-Trimethyl-l,2-
dihydroquinoline (TMQ)
147-47-7
101
2.18E+07
112
1.60E+07
163
6.35E+06
0
2-Phenylbenzothiazole
883-93-2
5
1.14E+06
7
9.12E+05
1
7.85E+05
0
3,5 -Di-tert-Buty 1-4-
hydroxybenzaldehyde
1620-98-0
0
N/A
4
3.19E+05
0
N/A
0
Diphenylamine
122-39-4
11
6.34E+05
0
N/A
0
N/A
0
Hexa(methoxymethyl)melamine
3089-11-0
23
2.52E+07
21
1.73E+07
7
9.10E+05
0
N,N'-Diphenyl-p-
phenylenediamine (DPPD)
74-31-7
37
2.61E+06
13
1.64E+06
8
5.30E+05
0
N,N'-Diphenylguanidine (DPG)
102-06-7
0
N/A
0
N/A
4
5.88E+06
0
N,N'-Ditolyl-p-
phenylenediamine (DTPD)
27417-40-9
25
2.72E+06
11
1.19E+06
1
7.56E+05
0
N,N-Dicyclohexyl-2-benzo
thiazolesulfenamide (DCBS)
4979-32-2
7
4.48E+05
13
4.98E+05
4
5.65E+05
0
N-tert-Butyl-2-
benzothiazolesulfenamide
(TBBS)
95-31-8
11
1.10E+06
0
N/A
0
N/A
0
Pyrimidine, 2-(4-pentylphenyl)-
5-propyl-
94320-32-8
17
3.88E+07
20
8.44E+06
10
5.05E+06
0
n-Isopropyl-n'-
phenylparaphenyl
enediamine (IPPD)
101-72-4
11
3.00E+06
7
7.86E+05
0
N/A
0
n-Nitrosodiphenylamine
86-30-6
2
5.09E+05
0
N/A
0
N/A
0
a LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry; N/A = Not applicable
b Recycling Plants (N = 27 samples); Indoor Fields (N=29 samples); Outdoor Fields (N=46 samples); Blanks (N = 9)
0 Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
d Frequency of observation. Sometimes the frequency exceeds the number of samples analyzed; this may be a result of the presence of same formula isomers or incorrect
chemical identity matching.
235
-------
Table 4-97. Tentative Suspect Screening Chemical Identifications Through Negative Ionization LC/TOFMS Analysis of Tire Crumb Rubber Solvent
Extractsa'b
Tentative Chemical Name
CAS
Number'
Recycling Plants
Frequency'1
Recycling Plants
Mean Area
Indoor Fields
Frequency'1
Indoor Fields
Mean Area
Outdoor Fields
Frequency'1
Outdoor Fields
Mean Area
Blanks
Frequency'1
Dehydroabietic acid
1740-19-8
19
3.22E+06
8
3.66E+06
3
2.93E+06
0
lH-isoindole-1,3 (2H)-dione
85-41-6
2
7.43E+04
0
N/A
0
N/A
0
2,2'-Methylene-bis-(4-methyl-6-
tert-butylphenol)
119-47-1
26
1.45E+06
2
2.59E+05
0
N/A
0
3,5-Di-tert-Buty 1-4-
hydroxybenzaldehyde
1620-98-0
19
8.34E+05
9
6.81E+05
2
8.18E+04
0
Benzoic acid
65-85-0
0
N/A
1
7.00E+04
0
N/A
0
Docosanoic acid
112-85-6
7
2.96E+04
9
4.19E+04
3
1.02E+05
0
Dodecanoic acid
143-07-7
24
2.03E+05
10
1.67E+05
2
1.08E+05
0
Octadecanoic acid, methyl ester
112-61-8
10
1.46E+05
9
9.58E+04
3
7.47E+04
0
a LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry
b Recycling Plants (N = 27 samples); Indoor Fields (N=29 samples); Outdoor Fields (N=46 samples); Blanks (N = 9)
0 Unique numerical identifier assigned by the Chemical Abstracts Service (CAS)
d Frequency of observation. Sometimes the frequency exceeds the number of samples analyzed; this may be a result of the presence of same formula isomers or incorrect
chemical identity matching.
236
-------
Suspect screening analyses were also performed by LC/TOFMS for chamber emission samples collected
during experiments performed at 60°C. No suspect screening chemicals were observed that met the
requirement of having average area counts for a tentatively identified chemical within at least one of the
three sample types that was more than three times greater than the average area counts in the chamber
background samples.
These suspect screening analysis results show 23 chemicals tentatively identified in tire crumb rubber
samples from recycling plants or synthetic turf fields that had either been reported in earlier research
studies or were reported to be tire manufacturing chemicals or transformation products. Some chemicals
found in 'fresh' tire crumb rubber from recycling plants were not observed in samples from the fields.
And in some cases, the chemicals were observed in field samples, but at lower frequencies or lower
average intensities. This may reflect patterns seen for the target organic analytes in this study, where
many organic chemicals had lower levels in field infill as compared to recycling plant tire crumb rubber,
and higher levels in indoor fields as compared to outdoor fields.
There are several limitations to these suspect screening analysis results. First, the chemical identities
generated in this research must be considered tentative and would need further analysis of known
chemical standards for confirmation. Second, chemicals present in the tire crumb rubber or tire crumb
rubber infill may not have been present in the extract or emission samples because of the solvents or
conditions used; other methods may have resulted in additional or different sets of chemicals. It is also
important to note that different instruments and methods can produce somewhat different mass spectra
for the same chemicals, making translation across methods and platforms somewhat difficult.
4.12 Non-Targeted Chemical Analysis
In addition to the target chemical and suspect screening analyses, non-targeted analyses were performed
to begin to further elucidate a wider range of organic chemicals associated with tire crumb rubber.
Targeted analysis begins with a known chemical and/or standard and methods are directed toward
identification or quantification. In contrast, non-targeted analysis begins with a survey of a sample and
builds a body of evidence to support an identification for each chemical that can be detected, but not
necessarily assigned. Tire crumb samples were analyzed in non-targeted mode and vendor software was
used to identify chemical features, which are unidentified chemicals with masses, retention times, and
mass spectral data measured from the sample. It is important to emphasize that the non-targeted
chemical identification results included in this report should be considered highly tentative and only the
first step of what would be a multi-step process to confirm chemical identities and the amounts of
chemicals present. Many of the highly-tentative chemical identities included in this report are likely to
be incorrect. Given this uncertain outcome, it is important to explain why this work was done:
• Many chromatographic peaks and mass spectral features other than the target chemical analytes
were observed in tire crumb rubber solvent extracts and emission samples analyzed in this study.
• Assessment of exposures to a limited set of target chemical analytes may not provide a full
picture of the cumulative exposures encountered by synthetic turf field users.
• This initial step in non-targeted analysis provides insight about the scope and nature of the non-
targeted chemicals that may be associated with tire crumb rubber.
• The results from this set of non-targeted analyses provides researchers with information useful
for future investigations that could be undertaken for confirming chemical identities, measuring
the amounts of chemicals associated with the tire crumb rubber, and assessing the potential for
exposure to these chemicals. For example, this information has been shared with OEHHA (under
237
-------
CalEPA/USEPA MCRADA #996-17) to aid their efforts in prioritizing and performing
confirmatory analyses for some SVOCs.
The multi-chemical nature of tire crumb rubber material is illustrated in Figures 4-63 and 4-64, where
example chromatographs from GC/MS SVOC solvent extract analysis and GC/TOFMS VOC emission
analyses show many chromatographic features across a range of intensities. For the SVOCs in Figure 4-
63, there are a number of chromatographic peaks that have higher intensities than benzothiazole, which
was the most abundant target analyte in the analysis. For the VOCs in Figure 4-64, the target analytes
methyl isobutyl ketone and benzothiazole had higher intensities than the other chromatographic peaks.
The non-targeted analysis performed as part of this research is a first step in understanding the nature of
those unidentified chromatographic peaks in terms of identity and abundance, and the potential
relevance for human exposures.
The chromatographic peaks eluting earlier than £
minutes should be disregarded at this time with
respect to the SVOC analysis.
The black line is the total ion current
chromatogram.
The green line is the extracted ion
current chromatogram.
Note the peak at 21.89 minutes is benzothiazole.
Benzothiazole was the most abundant target
analyte measured.
.Acqusrian Time (mmj
Figure 4-63. Example GC/MS SVOC solvent extraction sample analysis showing total ion current
and extracted ion current chromatograms for a recycling plant sample. [GC/MS = Gas chromatography/
mass spectrometry; SVOC = Semivolatile organic compound]
Target analyte Methyl
Isobutyl Ketone
Target analyte
Benzothiazole
jXii mL Llli iiMlAlil! UiiLi I ilflUMJIII.IKftIJIMflilMfflAftMj
™ ' » 4 4 4 4 * *
Figure 4-64. Example GC/TOFMS VOC 60 °C chamber emission sample analysis total ion current
chromatogram for a synthetic turf field. [GC/TOFMS = Gas chromatography/time-of-flight mass spectrometry;
VOC = Volatile organic compound]
238
-------
In this study, we selected a subset of tire crumb rubber samples from recycling plants and a subset of tire
crumb rubber infill samples from indoor and outdoor synthetic turf fields for non-targeted analysis. This
strategy allowed for assessment of chemicals potentially associated with 'fresh' recycled tire material
and to see whether those chemicals were also observed in the infill collected at synthetic turf fields. The
strategy also allowed for the reverse assessment - chemicals found in synthetic turf field infill samples
that were not observed in the recycling plant samples - to better assess the extent that chemicals from
sources other than the tire crumb rubber material are appearing in the infill.
Six tire recycling plant samples, five outdoor field infill samples, and five indoor field infill samples
were selected for non-targeted analyses. Non-targeted analyses were performed for solvent extract
samples by both GC/MS and LC/TOFMS. Non-targeted analyses were also performed for chamber
emission test samples generated at 60° C using GC/MS and LC/TOFMS methods for SVOCs and by
GC/TOFMS for VOCs.
Each of the three analytical methods (GC/MS SVOC, LC/TOFMS SVOC, and GC/TOFMS VOC)
produced different types of data and applied different approaches for tentative chemical identification.
The methods were previously described in section 3.6. Briefly, the GC/MS SVOC method produced
characteristic mass spectra that were matched to the National Institute of Standards and Technology
(NIST) spectral library (U.S. Department of Commerce, Gaithersburg, MD, USA) using Unknowns
Analysis software (Agilent Technologies, Santa Clara, CA, USA) and the total ion current (TIC)
Analysis approach. The deconvolution approach was not used because an excessive number of both
false positives and negatives were observed. TIC analysis is more accurate for this data set, but is not as
sensitive, so only chemicals with relatively-high concentrations were tentatively identified. A 50%
matching score cut-off was applied. In addition, chemicals with retention times below that of nonane
were excluded due to the uncertainty associated with the elution of the extraction solvents. The
instrument and methods available for GC/MS in this study were not ideal for non-targeted analysis, and
results may reflect limitations.
The high-resolution LC/TOFMS SVOC method produced accurate chemical mass values that were used
to provide exact chemical formulas. The formulas were referenced against the DSSTox chemical
database with over 750,000 chemical references. A chemical formula for each compound was predicted
by matching against the EPA Chemistry Dashboard (https://comptox.epa.gov/dashboard), which returns
possible chemical formulas, along with a score indicating certainty of the assignment. Formulas below a
score of 80 were ignored and the chemicals were excluded from the report. Further analysis and/or
expansion of the database may, in the future, allow identification of these compounds. Formula
assignments with scores above 80 were assigned a single compound identity from the database, and the
number of possible alternates was noted. The assigned chemical was the most likely chemical based on
consumer/commercial prevalence (see McEachran et al., 2017), as measured by frequency of literature
data sources. Where multiple chemical features with the same formula exist, the features were flagged
indicating the chemical formula is accurate, but the chemical assignment is one of many that are
possible.
The GC/TOFMS VOC method produced characteristic mass spectra that were matched to the NIST
spectral library, applied to chromatographic peaks above a minimum area count, and combined with a
forward and reverse spectral match score. Forward and reverse matches determined for each compound
had to both meet a minimum score of 75% for the compound to be included in the listing.
Additional acceptance criteria were also applied following spectral matching and selection. A minimum
frequency of at least three occurrences was required in at least one of the sample types (recycling plant,
indoor field, outdoor field) before a tentative chemical was included in the compilation. Also, average
239
-------
area counts for a tentatively-identified chemical had to be more than three times greater within at least
one of the three sample types (recycling plant, indoor field, outdoor field) than the average area counts
in the blank or chamber background samples.
The full tables for the five sets of non-targeted highly tentative chemical identification results are
provided in Appendix R. Summaries of the frequencies of chemicals tentatively identified in recycling
plant, outdoor field, and indoor field samples are shown in Table 4-98. In some cases, the same chemical
identity was reported multiple time in the same sample. This was due in part because chemical isomers
may generate the same or very similar spectra that are matched to a single library reference spectrum.
For example, a C19 saturated alkane can have numerous branched isomers in addition to its unbranched
form. In many cases, it was observed that the same chemical match was reported for spectra produced at
different chromatographic retention times, making the presence of isomers more likely. In some types of
mass spectral analyses, some chemicals may produce very similar mass spectra that are incorrectly
matched to library spectra. The high-resolution LC/TOFMS avoids this problem by matching to exact
chemical formulas but is limited in further chemical elucidation because it lacks chemical fragmentation
spectra. And some repeated chemical matches may simply be the result of incorrect matching
identifications.
The results in Table 4-98 show that several hundred organic chemicals may be associated with tire
crumb rubber and tire crumb rubber infill. Many, but not all, target chemicals were observed in the non-
targeted analyses. Several of the chemicals tentatively identified were included on the suspect screening
analysis list but were not observed in the LC/TOFMS suspect screening analysis. An example of this is
N-1,3-(dimethyl-butyl)-N'-phenyl-p-phenylenediamine (6PPD), an antiozonant/antioxidant compound,
which was observed in non-targeted GC/MS analysis in recycling plant and synthetic turf field samples
with relatively high response area counts.
However, many of the chemicals that were tentatively identified were not target analytes or suspect
screening analytes in this study. Some of these chemicals may have been original tire chemical
ingredients, or they may be transformation products or degradates of those ingredients. Some of the
chemicals may have been absorbed by the tire material over the life course of the tire. Some chemicals
found in 'new' tire crumb rubber from recycling plants were not observed in samples from the fields.
And in some cases, the chemicals were observed in field samples, but at lower frequencies or lower
average intensities, which may reflect patterns seen for the target organic analytes in this study (where
many organic chemicals had lower levels in field infill as compared to recycling plant tire crumb rubber
and higher levels in indoor fields as compared to outdoor fields). The results also show that there were
chemicals present in tire crumb rubber infill from synthetic turf fields that were not observed in the
'new' tire crumb rubber from recycling plants. This suggests that some chemicals in synthetic turf field
infill have sources other than the recycled tire material.
It is important to note that many other chromatographic and mass spectral features observed in these
analyses did not match to library reference spectra and were not included in the compilation of highly-
tentative chemical IDs in this report. This was particularly true for the solvent extraction LC/TOFMS
analysis. Therefore, the numbers of potential tire crumb associated chemicals in this report may be
underestimated.
Emphasizing that these non-targeted analysis chemical identifications are highly tentative, it is not
recommended that these results be used for cumulative exposure assessment, toxicity information
collation, or risk assessment at this time. Additional work is needed to build upon these results to
ascertain chemical identity confirmations and determination or estimations of relative amounts.
240
-------
Table 4-98. Non-targeted Analysis Frequency Summaries for Highly Tentative Chemical Identificationsa'b'c
Facility
GC/MS
GC/MS
LC/TOFMS
LC/TOFMS
LC/TOFMS
GC/TOFMS
GC/TOFMS
GC/MS
GC/MS
LC/TOFMS
LC/TOFMS
LC/TOFMS
Type
SVOC
SVOC
SVOC
SVOC
SVOC
VOC
VOC
SVOC
SVOC
SVOC
SVOC
SVOC
Solvent
Solvent
Solvent
Solvent
Solvent
60 °C
60 °C
60 °C
60 °C
60 °C
60 °C
60 °C
Extract
Extract
Extract
Extract
Extract
Emission
Emission
Emission
Emission
Emission
Emission
Emission
Analysis -
Analysis -
Analysis-
Analysis -
Analysis -
Sample
Sample
Sample
Sample
Sample
Sample
Sample
n
Average
n
Positive
Negative
Analysis -
Analysis -
Analysis -
Analysis -
Analysis -
Analysis -
Analysis -
frequency
ionization
ionization
n
A verage
n
Average
n
Positive
Negative
of unique
mode
mode
frequency of
frequency
ionization
ionization
chemicals
frequency
frequency
unique
of unique
mode
mode
unique
unique
chemicals
chemicals
frequency
frequency
chemicals
chemicals
identified
unique
unique
chemicals
chemicals
Recycling
6
49
6
295
86
6
151
6
18
6
32
4
Plants
Indoor
5
54
5
293
91
4
136
5
13
5
32
4
Synthetic
Turf
Fields
Outdoor
4
53
5
228
101
5
115
5
20
5
26
4
Synthetic
Turf
Fields
11GC/MS = Gas chromatography/mass spectrometry; LC/TOFMS = Liquid chromatography/time-of-flight mass spectrometry; SVOC = Semivolatile organic compound; VOC =
Volatile organic compound
b The highly tentative chemical identities for each sample type can be found in Appendix R.
°Many chemicals were identified more than once in a sample; this may be because multiple isomers were present or as a result of incorrect mass spectral matching
241
-------
There are several limitations to these non-targeted analysis results. First, as previously noted, the
chemical identities generated in this research must be considered highly tentative and considerable
future research is needed to confirm identifications. Second, the methods did not attempt to identify
chromatographic peaks with very low intensities. While it was important to try to identify the major
components, some chemicals with potential toxicological significance at lower levels in tire rubber (e.g.,
dibenzopyrenes, see Sadiktsis et al., 2012) may have been missed. Third, tentative identities for mass
spectra that did not meet specified matching scores were not reported, but that does not mean that a
chemical was not present at that chromatographic retention time. It may mean that tire crumb rubber-
associated chemical or chemical degradate spectra were not available for matching. Finally, chemicals
present in the material may not have been present in the extract or emission sample because of the
solvents or conditions used; other methods may have resulted in additional or different sets of chemicals.
It is also important to note that different instruments and methods can produce somewhat different mass
spectra for the same chemicals, making translation across methods and platforms somewhat difficult.
4.13 Bioaccessibility Testing for Metals
Bioaccessibility testing was performed for tire crumb rubber samples collected from recycling plants
and tire crumb rubber infill collected from synthetic turf fields using three simulated biofluids. All
bioaccessibility testing's metal measurement concentrations (i.e., |ag of analyte/mL biofluid extract)
were blank-subtracted before any calculations and analyses. If the blank-corrected concentrations were
below zero, the results were set to zero. All biofluid extract analysis results were labeled with one of the
three detection categories - 1) above the analytical limit of quantitation (LOQ), 2) below the LOQ and
above the LOD, or 3) below the LOD. For metal results that were below the LOD, we used the reported
metal concentrations in biofluid extracts and did not conduct imputation (i.e., replace the concentration
below LOD with a value). Table 4-99 gives the percent detection rates (%) in the three artificial biofluid
extracts of the tire crumb sample, stratified by the detection categories. Overall, artificial gastric fluid
extracts contained the most detectable metals (13 metals with 50% or higher results over the LOD),
followed by artificial sweat plus sebum extracts (7 metals with 50% or higher results over the LOD),
while artificial saliva extracts contained the least detectable metals (3 metals with 50% or higher results
over the LOD). The detection rate (i.e., result > LOD) for lead was 100%, 22%, and 12% in artificial
gastric fluid, saliva, and sweat plus sebum, respectively.
Table 4-99. Detection Rates (%) of 19 Metals in Tire Crumb Sample Extracts (Stratified by Artificial
Biofluid)8
Artificial
Biofluid
Analvtc
Mcthodb
< LOD (%)
> LOD and < LOQ (%)
> LOQ (%)
Gastric fluid
Aluminum
tCP/AES
1
13
86
Gastric fluid
Antimony
tCP/MS
54
13
33
Gastric fluid
Arsenic
tCP/MS
61
35
4
Gastric fluid
Barium
tCP/MS
0
0
100
Gastric fluid
Beryllium
tCP/MS
67
28
5
Gastric fluid
Cadmium
tCP/MS
34
23
43
Gastric fluid
Chromium
tCP/MS
40
33
28
Gastric fluid
Cobalt
tCP/MS
0
0
100
Gastric fluid
Copper
tCP/MS
0
0
100
Gastric fluid
tron
tCP/AES
0
8
92
Gastric fluid
Lead
tCP/MS
0
0
100
242
-------
Table 4-99 Continued
Artificial
Biofluid
Analytc
Method1*
< LOD (%)
> LOD and < LOQ (%)
> LOQ (%)
Gastric fluid
Magnesium
ICP/AES
1
3
97
Gastric fluid
Manganese
ICP/MS
8
4
88
Gastric fluid
Mercury
CVAA
90
10
0
Gastric fluid
Molybdenum
ICP/MS
82
17
2
Gastric fluid
Nickel
ICP/MS
33
25
43
Gastric fluid
Selenium
ICP/MS
96
4
0
Gastric fluid
Strontium
ICP/MS
8
21
72
Gastric fluid
Tin
ICP/AES
98
2
0
Gastric fluid
Zinc
ICP/AES
0
0
100
S
iliva
Aluminum
ICP/AES
87
8
5
S
iliva
Antimony
ICP/MS
65
22
13
s
iliva
Arsenic
ICP/MS
94
6
0
s
iliva
Barium
ICP/MS
56
29
16
s
iliva
Beryllium
ICP/MS
93
7
0
s
iliva
Cadmium
ICP/MS
90
9
1
s
iliva
Chromium
ICP/MS
93
5
3
s
iliva
Cobalt
ICP/MS
11
24
65
s
iliva
Copper
ICP/MS
62
5
33
s
iliva
Iron
ICP/AES
88
10
2
s
iliva
Lead
ICP/MS
78
13
9
s
iliva
Magnesium
ICP/AES
20
28
52
s
iliva
Manganese
ICP/MS
63
23
14
s
iliva
Mercury
CVAA
99
0
1
s
iliva
Molybdenum
ICP/MS
97
2
1
s
iliva
Nickel
ICP/MS
92
6
3
s
iliva
Selenium
ICP/MS
94
6
0
s
iliva
Strontium
ICP/MS
74
22
4
s
iliva
Tin
ICP/AES
100
0
0
s
iliva
Zinc
ICP/AES
7
24
69
Sweat plus sebum
Aluminum
ICP/AES
70
13
17
Sweat plus sebum
Antimony
ICP/MS
78
14
8
Sweat plus sebum
Arsenic
ICP/MS
93
8
0
Sweat plus sebum
Barium
ICP/MS
20
5
75
Sweat plus sebum
Beryllium
ICP/MS
91
3
6
Sweat plus sebum
Cadmium
ICP/MS
78
14
8
Sweat plus sebum
Chromium
ICP/MS
68
23
9
Sweat plus sebum
Cobalt
ICP/MS
0
0
100
Sweat plus sebum
Copper
ICP/MS
26
16
58
Sweat plus sebum
Iron
ICP/AES
73
16
12
Sweat plus sebum
Lead
ICP/MS
88
4
8
Sweat plus sebum
Magnesium
ICP/AES
7
12
82
243
-------
Table 4-99 Continued
Artificial
Biofluid
Analytc
Method1*
< LOD (%)
> LOD and < LOQ (%)
> LOQ (%)
Sweat plus sebum
Manganese
ICP/MS
33
18
49
Sweat plus sebum
Mercury
CVAA
98
2
0
Sweat plus sebum
Molybdenum
ICP/MS
96
3
2
Sweat plus sebum
Nickel
ICP/MS
59
19
22
Sweat plus sebum
Selenium
ICP/MS
80
20
0
Sweat plus sebum
Strontium
ICP/MS
36
42
23
Sweat plus sebum
Tin
ICP/AES
100
0
0
Sweat plus sebum
Zinc
ICP/AES
1
3
97
a LOD = Limit of detection; LOQ = Limit of quantitation
b ICP/MS = Inductively coupled plasma/mass spectrometry; ICP/AES = inductively coupled plasma-atomic emission
spectrometry; CVAA = Cold vapor atomic absorption
Among the 82 tire crumb samples tested for bioaccessibility using each artificial biofluid, repeated
bioaccessibility tests were performed for a subset of samples for each artificial biofluid. Thirty-four (34)
samples had repeated bioaccessibility tests for artificial gastric fluid, 24 samples for saliva, and 34
samples for sweat plus sebum (see Appendix E for detailed information on repeated measurements). The
arithmetic means of the repeated test results were used in the final percent bioaccessibility calculation.
Table 4-100 presents the summary statistics of measured metal concentrations bioaccessible in the
biofluid extracts (in mg analyte/kg tire crumb rubber, or mg/kg TCR).
Overall, artificial gastric fluid extracts contained the highest levels of metals, followed by artificial
sweat plus sebum extracts; artificial saliva contained the lowest levels of metals. The concentrations of
19 metals in each artificial biofluid were highly variable, spanning several orders of magnitude. Zinc
had the highest median (i.e., 50th percentile) concentrations in all three artificial biofluids. The three
most abundant metals (based on median concentrations) were zinc, iron and magnesium for artificial
gastric fluid extracts; zinc, magnesium and cobalt for artificial saliva; and zinc, magnesium and copper
for artificial sweat plus sebum (Table 4-100).
Table 4-100. Summary Statistics of Measured Metal Levels in Artificial Biofluid Extracts of Tire Crumb
Samples, Stratified by Artificial Biofluid3
Artificial
Biofluid
Analytc
Mean
(mg/kg
TCR)
Standard
Deviation
(mjj/kg
TCR)
Minimum
(mg/kg
TCR)
25th
Percentile
(mjj/kK
TCR)
50th
Percentile
(mg/kg
TCR)
75th
Percentile
(m«/k«
TCR)
Maximum
(mg/kg
TCR)
Gastric fluid
Aluminum
6.2
5.4
0
2.0
5.0
00
00
24
Gastric fluid
Antimony
0.060
0.39
0
0
0.0036
0.034
3.6
Gastric fluid
Arsenic
0.0039
0.0054
0
0
0
0.0078
0.019
Gastric fluid
Barium
0.45
0.35
0.073
0.24
0.37
0.52
1.8
Gastric fluid
Beryllium
0.00048
0.00090
0
0
0
0.00074
0.0052
Gastric fluid
Cadmium
0.0043
0.0080
0
0
0.0023
0.0050
0.064
Gastric fluid
Chromium
0.067
0.10
0
0.012
0.045
0.092
0.71
Gastric fluid
Cobalt
0.37
0.23
0.072
0.20
0.31
0.52
1.0
Gastric fluid
Copper
3.1
3.3
0.25
1.0
2.02
3.6
20
244
-------
Table 4-100 Continued
Artificial
Biofluid
Analytc
Mean
(m«/k«
TCR)
Standard
Deviation
(mg/kjj
TCR)
Minimum
(mg/kg
TCR)
25th
Percentile
(mg/kg
TCR)
50th
Percentile
(mjj/kjj
TCR)
75th
Percentile
(mg/kg
TCR)
Maximum
(mg/kg
TCR)
Gastric fluid
Iron
31
22
5.6
17
25.6
39
143
Gastric fluid
Lead
0.42
0.40
0.056
0.17
0.29
0.56
2.8
Gastric fluid
Magnesium
10
10
0.12
3.4
6.7
15
66
Gastric fluid
Manganese
0.82
0.62
0
0.40
0.67
1.1
3.2
Gastric fluid
Mercury
0.00024
0.00067
0
0
0
0
0.0026
Gastric fluid
Molybdenum
0.0041
0.0094
0
0
0
0.0027
0.048
Gastric fluid
Nickel
0.060
0.10
0
0.015
0.039
0.069
0.68
Gastric fluid
Selenium
0.00040
0.0016
0
0
0
0
0.011
Gastric fluid
Strontium
0.24
0.39
0
0.051
0.11
0.25
2.5
Gastric fluid
Tin
0.0032
0.023
0
0
0
0
0.19
Gastric fluid
Zinc
138
63
34
94
129
164
358
Saliva
Aluminum
0.059
0.32
0
0
0
0
2.9
Saliva
Antimony
0.0072
0.025
0
0
0
0.010
0.22
Saliva
Arsenic
0.00060
0.0021
0
0
0
0
0.012
Saliva
Barium
0.0081
0.017
0
0
0.0010
0.0088
0.12
Saliva
Beryllium
0.000091
0.00040
0
0
0
0
0.0032
Saliva
Cadmium
0.00023
0.00067
0
0
0
0
0.0031
Saliva
Chromium
0.0067
0.029
0
0
0
0
0.21
Saliva
Cobalt
0.048
0.055
0
0.0068
0.024
0.069
0.22
Saliva
Copper
0.057
0.11
0
0
0
0.084
0.55
Saliva
Iron
0.12
0.43
0
0
0
0
2.9
Saliva
Lead
0.0
0.0061
0
0
0
0.0017
0.048
Saliva
Magnesium
1.2
2.1
0
0.23
0.63
1.3
16
Saliva
Manganese
0.089
0.44
0
0
0
0.047
3.9
Saliva
Mercury
0.00011
0.0010
0
0
0
0
0.009
Saliva
Molybdenum
0.00052
0.0031
0
0
0
0
0.024
Saliva
Nickel
0.0047
0.016
0
0
0
0
0.084
Saliva
Selenium
0.00031
0.0012
0
0
0
0
0.0068
Saliva
Strontium
0.0098
0.028
0
0
0
0.0096
0.22
Saliva
Tin
0
0
0
0
0
0
0
Saliva
Zinc
1.1
1.4
0
0.44
0.72
1.3
10
Sweat plus sebum
Aluminum
0.20
0.84
0
0
0
0.20
7.4
Sweat plus sebum
Antimony
0.0028
0.0061
0
0
0
0.0042
0.037
Sweat plus sebum
Arsenic
0.0012
0.0026
0
0
0
0
0.0089
Sweat plus sebum
Barium
0.052
0.066
0
0.015
0.038
0.058
0.40
Sweat plus sebum
Beryllium
0.00044
0.0014
0
0
0
0
0.0084
Sweat plus sebum
Cadmium
0.00064
0.0013
0
0
0
0.00088
0.0068
Sweat plus sebum
Chromium
0.012
0.020
0
0
0
0.021
0.084
245
-------
Table 4-100 Continued
Artificial
Biofluid
Analvtc
Mean
(mg/kg
TCR)
Standard
Deviation
(mg/kg
TCR)
Minimum
(mg/kg
TCR)
25th
Percentile
(mg/kg
TCR)
50th
Percentile
(mg/kg
TCR)
75th
Percentile
(mg/kg
TCR)
Maximum
(mg/kg
TCR)
Sweat plus sebum
Cobalt
0.15
0.10
0.017
0.065
0.12
0.23
0.50
Sweat plus sebum
Copper
0.17
0.16
0
0.040
0.14
0.24
0.78
Sweat plus sebum
Iron
0.31
0.58
0
0
0
0.33
2.7
Sweat plus sebum
Lead
0.0036
0.021
0
0
0
0.00080
0.19
Sweat plus sebum
Magnesium
2.2
2.7
0
0.74
1.2
2.9
18
Sweat plus sebum
Manganese
0.12
0.13
0
0.015
0.092
0.16
0.67
Sweat plus sebum
Mercury
0.00003
0.00023
0
0
0
0
0.002
Sweat plus sebum
Molybdenum
0.0016
0.012
0
0
0
0
0.10
Sweat plus sebum
Nickel
0.014
0.030
0
0
0.0031
0.016
0.22
Sweat plus sebum
Selenium
0.0010
0.0016
0
0
0
0.0024
0.0051
Sweat plus sebum
Strontium
0.061
0.11
0
0.011
0.023
0.056
0.68
Sweat plus sebum
Tin
0
0
0
0
0
0
0
Sweat plus sebum
Zinc
13
9.5
0.39
4.8
11
18
40
11 Tire crumb samples (n=82); mg/kg TCR = milligrams analyte/kilogram tire crumb rubber
* Percentiles in italics are less than limit of detection
Among the 82 tire crumb samples tested for bioaccessibility, 27 were collected at recycling plants and
55 were collected from synthetic turf fields (including 40 composite samples and 15 individual location
samples). Table 4-101 presents the mean and standard deviation of measured metal concentrations in the
biofluid extracts, stratified by recycling plant vs. synthetic turf field samples. We sought to compare the
metal concentrations in biofluid extracts between the tire crumb samples collected at recycling plants
and synthetic turf fields for analytes/biofluid extracts with 50% or higher detection rate. Because the
assumptions of parametric tests were not met (such as normality), we chose to use the rank-based
nonparametric Kruskal Wallis test, in which the null hypothesis was that the distributions were identical,
and the alternative was that they differ (with one of the distributions yielding larger observations than
the other). The p-values from the Kruskal Wallis test are given in Table 4-101. Among the 13 metals
with 50% or higher detection rate in artificial gastric fluid extracts, aluminum (p < 0.001), cobalt (p =
0.02), lead (p < 0.001) and nickel (p = 0.02) were present at statistically significant higher levels in the
extracts of synthetic turf field samples than those of recycling plant samples, while copper (p < 0.001)
and iron (p < 0.001) were lower in field sample extracts than recycling plant sample extracts. The rest of
the detectable metals were all present at non-statistically significant higher levels in field sample extracts
than in recycling plant sample extracts (p = 0.06 - 0.98). In artificial saliva extracts, none of the three
metals with 50% or higher detection rate had statistically significant differences between the plant and
field samples (p = 0.15 - 0.48). In artificial sweat plus sebum extracts, magnesium (p < 0.001) and
strontium (p < 0.001) were present at statistically significant higher levels in the extracts of synthetic
turf field samples than those of the recycling plant samples.
246
-------
Table 4-101. Measured Metal Levels in Artificial Biofluid Extracts of Tire Crumb Samples, Stratified by
Recycling Plant vs. Synthetic Turf Field Samples3
Artificial Biofluid
Analytc
Recycling
Plant - Mean
(mg/kg TCR)
Recycling
Plant -
Standard
Deviation
(mg/kg TCR)
Synthetic
Turf Field -
Mean
(mg/kg
TCR)
Synthetic
Turf Field -
Standard
Deviation
(mg/kg
TCR)
Kruskal
Wallis
|)-valucbl
Gastric fluid
Aluminum
1.8
0.6
8.4
5.3
< 0.001
Gastric fluid
Antimony
0.031
0.025
0.074
0.48
N/A
Gastric fluid
Arsenic
0.0037
0.0048
0.0039
0.0056
N/A
Gastric fluid
Barium
0.35
0.12
0.5
0.41
0.38
Gastric fluid
Beryllium
0.00025
0.00076
0.00059
0.00095
N/A
Gastric fluid
Cadmium
0.0029
0.0016
0.0051
0.0096
0.38
Gastric fluid
Chromium
0.057
0.064
0.071
0.12
0.98
Gastric fluid
Cobalt
0.29
0.18
0.41
0.24
0.02
Gastric fluid
Copper
6.0
4.3
1.7
1.2
< 0.001
Gastric fluid
Iron
48
27
23
13
< 0.001
Gastric fluid
Lead
0.18
0.12
0.54
0.43
< 0.001
Gastric fluid
Magnesium
6.1
3.7
12
12
0.06
Gastric fluid
Manganese
0.79
0.50
0.83
0.67
0.75
Gastric fluid
Mercury
0.00056
0.00092
0.00008
0.00043
N/A
Gastric fluid
Molybdenum
0.0076
0.0096
0.0024
0.009
N/A
Gastric fluid
Nickel
0.032
0.028
0.074
0.12
0.02
Gastric fluid
Selenium
0.00041
0.0022
0.0004
0.0014
N/A
Gastric fluid
Strontium
0.098
0.059
0.31
0.46
0.08
Gastric fluid
Tin
0.0071
0.037
0.0013
0.0097
N/A
Gastric fluid
Zinc
120
41
150
70
0.07
Saliva
Aluminum
0.034
0.065
0.071
0.39
N/A
Saliva
Antimony
0.0044
0.0059
0.0086
0.03
N/A
Saliva
Arsenic
0
0
0.00089
0.0025
N/A
Saliva
Barium
0.0034
0.0077
0.01
0.02
N/A
Saliva
Beryllium
0.00004
0.00013
0.00012
0.00048
N/A
Saliva
Cadmium
0.00005
0.0001
0.00032
0.0008
N/A
Saliva
Chromium
0.003
0.0092
0.0085
0.034
N/A
Saliva
Cobalt
0.036
0.044
0.055
0.059
0.32
Saliva
Copper
0.02
0.091
0.075
0.11
N/A
Saliva
Iron
0.18
0.35
0.095
0.46
N/A
Saliva
Lead
0.002
0.0093
0.0017
0.0037
N/A
Saliva
Magnesium
0.59
0.49
1.5
2.5
0.15
Saliva
Manganese
0.036
0.04
0.12
0.54
N/A
Saliva
Mercury
0
0
0.00016
0.0012
N/A
Saliva
Molybdenum
0
0
0.00077
0.0037
N/A
247
-------
Table 4-101 Continued
Artificial Biofluid
Analvtc
Recycling
Plant - Mean
(mg/kg TCR)
Recycling
Plant -
Standard
Deviation
(mg/kg TCR)
Synthetic
Turf Field -
Mean
(mg/kg
TCR)
Synthetic
Turf Field -
Standard
Deviation
(mg/kg
TCR)
Kruskal
Wallis
|)-valucbl
Saliva
Nickel
0.0012
0.006
0.0064
0.019
N/A
Saliva
Selenium
0
0
0.00046
0.0015
N/A
Saliva
Strontium
0.0057
0.0085
0.012
0.033
N/A
Saliva
Tin
0
0
0
0
N/A
Saliva
Zinc
1.1
1.9
1.1
1
0.48
Sweat plus sebum
Aluminum
0.14
0.13
0.23
1
N/A
Sweat plus sebum
Antimony
0.0045
0.0054
0.002
0.0063
N/A
Sweat plus sebum
Arsenic
0.00019
0.00096
0.0018
0.003
N/A
Sweat plus sebum
Barium
0.046
0.033
0.055
0.077
0.46
Sweat plus sebum
Beryllium
0.0013
0.0022
0.00003
0.0002
N/A
Sweat plus sebum
Cadmium
0.0012
0.0019
0.00038
0.00076
N/A
Sweat plus sebum
Chromium
0.01
0.02
0.013
0.02
N/A
Sweat plus sebum
Cobalt
0.13
0.1
0.15
0.11
0.42
Sweat plus sebum
Copper
0.16
0.15
0.17
0.17
0.78
Sweat plus sebum
Iron
0.62
0.75
0.15
0.41
N/A
Sweat plus sebum
Lead
0.00062
0.0014
0.0051
0.026
N/A
Sweat plus sebum
Magnesium
1.1
0.55
2.7
3.1
< 0.001
Sweat plus sebum
Manganese
0.14
0.14
0.11
0.12
N/A
Sweat plus sebum
Mercury
0.00007
0.00038
0.00001
0.0001
N/A
Sweat plus sebum
Molybdenum
0.0039
0.02
0.00056
0.0022
N/A
Sweat plus sebum
Nickel
0.007
0.0098
0.018
0.036
N/A
Sweat plus sebum
Selenium
0
0
0.0015
0.0017
N/A
Sweat plus sebum
Strontium
0.016
0.014
0.082
0.12
< 0.001
Sweat plus sebum
Tin
0
0
0
0
N/A
Sweat plus sebum
Zinc
13
8.8
12
9.9
0.66
a Recycling Plant (n=27); Synthetic Turf Field (n=55); mg/kg TCR = milligrams analyte/kilogram tire crumb rubber
b p-values for Kruskal Wallis test between the recycling plant samples and synthetic turf field samples
0 N/A = not available for analytes/artificial fluids with less than 50% detection rate
Percent in vitro bioaccessibility was calculated by dividing the blank-subtracted metal concentration in
the biofluid extract with the corresponding metal's blank-subtracted concentration measured by ICP/MS
in that tire crumb sample. Mercury was not measured by ICP/MS in the tire crumb samples; therefore,
percent bioaccessibility could not be calculated for mercury. Percent in vitro bioaccessibility was
calculated only when the blank-subtracted concentration in tire crumb constituent (i.e., denominator of
the % bioaccessibility calculation) was above 3 times the corresponding reporting limit. Two calculated
% in vitro bioaccessibility values were above 100% (i.e., antimony in one synthetic turf field sample and
molybdenum in another). In both cases, the analyte concentrations in tire crumb constituent were very
248
-------
low - at 10th percentile and less than 5th percentile for these two samples/analytes, respectively.
Additionally, given the large heterogeneity of many metals in tire crumb samples even within the same
sample containers (see section 4.9.1 in this report; U.S. EPA, 2009; Pavilonis et al., 2014), the calculated
above-100% bioaccessibility values in these two samples/analytes were most likely due to the low
concentrations in tire crumb samples and the heterogeneity of the tire crumb samples, and therefore,
were excluded in subsequent data analyses.
Table 4-102 gives the summary descriptive statistics of the percent in vitro bioaccessibility results for
metals in the 82 tire crumb samples in three artificial biofluids (i.e., the portion of the analyte in tire
crumb samples that were extractable, or in other words, bioaccessible, in the artificial biofluids).
Overall, metals in the 82 tire crumb samples had the highest percent in vitro bioaccessibility in artificial
gastric fluid (median 0 - 12%) for the 19 metals, followed by artificial sweat plus sebum (median 0 -
1.5%); the metals in vitro bioaccessibility values in artificial saliva were predominantly near 0%. The
same pattern was also observed on mean percent bioaccessibility values that averaged 3.4% in gastric
fluid, 0.7%) in sweat plus sebum, and 0.3%> in saliva among all metals. In artificial gastric fluid, four
metals' median percent in vitro bioaccessibility values were above 5%>, including manganese (12%>),
copper (7.3%>), iron (6.4%>), and barium (6.0%>). In artificial sweat plus sebum, three metals' median
percent bioaccessibility values were above 0.5%>, including manganese (1.5%), strontium (0.9%>), and
barium (0.6%>). For lead, the median in vitro bioaccessibility was 1.9% (range: 0.2 - 13.5%), 0% (range:
0 - 0.5%>), and 0% (0 - 1.9%) in artificial gastric fluid, saliva, and sweat plus sebum, respectively.
Table 4-103 presents the in vitro percent bioaccessibility results (mean and standard deviation) in three
artificial biofluids, stratified by recycling plant vs. synthetic turf field samples. The nonparametric
Kruskal Wallis test was used to compare the percent in vitro bioaccessibility between the tire crumb
samples collected at recycling plants and synthetic turf fields for analytes/biofluid extracts with 50% or
more detection rate. The ^-values from the Kruskal Wallis test are given in Table 4-103. Among the 13
metals with 50% or higher detection rates in artificial gastric fluid extracts, 7 metals (aluminum,
cadmium, cobalt, lead, magnesium, nickel and zinc) had statistically significant higher percent
bioaccessibility in synthetic turf field samples than recycling plant samples, while copper and iron had
lower bioaccessibility in field samples than recycling plant samples (p < 0.001). For artificial sweat plus
sebum and saliva, the percent in vitro bioaccessibility did not have statistically significant differences
between the plant and field samples for all detectable metals, except for strontium in artificial sweat plus
sebum, which exhibited higher in vitro bioaccessibility for synthetic turf field samples than plant
samples (p = 0.001).
Several previous studies (Pronk et al., 2018; RIVM, 2017; U.S. EPA, 2009; Pavilonis et al., 2014; Zhang
et al., 2008) have investigated in vitro bioaccessibility of metals in tire crumb samples and reported
either metal concentrations in artificial biofluid extracts (Tables 4-104 and 4-105), or percent in vitro
bioaccessibility (Table 4-106) in artificial biofluids, or both. Most previous studies had a much smaller
sample size and fewer number of metal analytes, which makes this study the largest study that we know
of on in vitro bioaccessibility testing of metals in tire crumb samples.
It should be noted that the bioaccessibility testing (numerator for percent bioaccessibility calculation)
used the tire crumb samples as is without drying, while the constituent concentrations (denominator)
were based on moisture-free contents. As described in Section 4.5.1, the median (with range) moisture
levels in the field samples (n=40) and recycling facilities (n=9) are 0.81% (0.40%>-6.22%>) and 0.87%
(0.52%>-0.99%>), respectively. Therefore, the moisture contents lead to a slight overestimate (about a
factor of 0.01) of the calculated percent bioaccessibility results.
249
-------
Table 4-102. Summary Descriptive Statistics of Calculated In Vitro Percent Bioaccessibility Results for Metals in Tire Crumb Samples that
Bioaccessible in Three Artificial Biofluids
are
Artificial
Biofluid
Analytc
Na
In Vitro %
Bioaccessibility
Mean (%)
In Vitro %
Bioaccessibility
Standard
Deviation (%)
In Vitro %
Bioaccessibility
Minimum (%)
In Vitro %
Bioaccessibility
25th Percentile
(%)
In Vitro %
Bioaccessibility
Median, 50th
Percentile (%)
In Vitro %
Bioaccessibility
75th Percentile
(%)
In Vitro %
Bioaccessibility
Maximum (%)
Gastric fluid
Aluminum
82
0.6
0.5
0.0
0.2
0.6
0.8
2.6
Gastric fluid
Antimony
81
1.4
1.8
0.0
0.0
0.4
2.8
7.6
Gastric fluid
Arsenic
82
1.1
1.7
0.0
0.0
0.0
2.4
8.4
Gastric fluid
Barium
82
6.9
4.8
0.2
4.5
6.0
9.1
29.7
Gastric fluid
Beryllium
55
3.1
6.7
0.0
0.0
0.0
4.6
38.3
Gastric fluid
Cadmium
82
0.5
0.6
0.0
0.0
0.4
0.7
3.4
Gastric fluid
Chromium
76
4.1
7.3
0.0
0.8
2.6
5.0
55.1
Gastric fluid
Cobalt
82
0.3
0.2
0.0
0.1
0.2
0.3
1.2
Gastric fluid
Copper
82
8.5
4.9
1.6
4.4
7.3
11.4
20.5
Gastric fluid
Iron
82
6.9
4.0
0.1
3.4
6.4
9.5
17.0
Gastric fluid
Lead
82
2.8
2.3
0.2
1.3
1.9
3.3
13.5
Gastric fluid
Magnesium
82
3.5
3.2
0.1
1.3
2.2
4.6
20.4
Gastric fluid
Manganese
82
12.9
8.1
0.0
8.7
12.0
15.8
35.0
Gastric fluid
Molybdenum
81
1.7
3.9
0.0
0.0
0.0
1.0
24.1
Gastric fluid
Nickel
82
2.5
4.5
0.0
0.3
1.4
2.8
32.6
Gastric fluid
Selenium
9
0.6
1.8
0.0
0.0
0.0
0.0
5.4
Gastric fluid
Strontium
82
6.5
7.6
0.0
1.8
3.6
8.7
42.4
Gastric fluid
Tin
80
0.2
1.1
0.0
0.0
0.0
0.0
7.3
Gastric fluid
Zinc
82
0.9
0.5
0.2
0.6
0.8
1.1
2.5
Saliva
Aluminum
82
0.0
0.0
0.0
0.0
0.0
0.0
0.3
Saliva
Antimony
82
0.7
1.8
0.0
0.0
0.0
0.7
14.9
Saliva
Arsenic
82
0.2
0.7
0.0
0.0
0.0
0.0
4.5
Saliva
Barium
82
0.1
0.2
0.0
0.0
0.0
0.1
1.4
Saliva
Beryllium
55
0.5
2.3
0.0
0.0
0.0
0.0
15.9
Saliva
Cadmium
82
0.0
0.1
0.0
0.0
0.0
0.0
0.5
Saliva
Chromium
76
0.3
1.1
0.0
0.0
0.0
0.0
8.7
Saliva
Cobalt
82
0.0
0.1
0.0
0.0
0.0
0.0
0.2
Saliva
Copper
82
0.2
0.6
0.0
0.0
0.0
0.3
4.3
Saliva
Iron
82
0.0
0.1
0.0
0.0
0.0
0.0
0.6
250
-------
Table 4-102 Continued
Artificial
Biofluid
Analvtc
Na
In Vitro %
Bioaccessibility
Mean (%)
In Vitro %
Bioaccessibility
Standard
Deviation (%)
In Vitro %
Bioaccessibility
Minimum (%)
In Vitro %
Bioaccessibility
25th Percentile
(%)
In Vitro %
Bioaccessibility
Median, 50th
Percentile (%)
In Vitro %
Bioaccessibility
75th Percentile
(%)
In Vitro %
Bioaccessibility
Maximum (%)
Saliva
Lead
82
0.0
0.1
0.0
0.0
0.0
0.0
0.5
Saliva
Magnesium
82
0.4
0.7
0.0
0.1
0.2
0.5
5.0
Saliva
Manganese
82
1.1
4.1
0.0
0.0
0.0
0.8
32.2
Saliva
Molybdenum
82
0.8
6.4
0.0
0.0
0.0
0.0
57.6
Saliva
Nickel
82
0.2
0.8
0.0
0.0
0.0
0.0
5.0
Saliva
Selenium
9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Saliva
Strontium
82
0.3
0.5
0.0
0.0
0.0
0.3
3.1
Saliva
Tin
80
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Saliva
Zinc
82
0.0
0.0
0.0
0.0
0.0
0.0
0.1
Sweat plus sebum
Aluminum
82
0.0
0.1
0.0
0.0
0.0
0.0
0.3
Sweat plus sebum
Antimony
82
0.2
0.6
0.0
0.0
0.0
0.3
3.9
Sweat plus sebum
Arsenic
82
0.4
0.9
0.0
0.0
0.0
0.0
4.4
Sweat plus sebum
Barium
82
0.8
0.9
0.0
0.2
0.6
1.0
4.8
Sweat plus sebum
Beryllium
55
4.7
12.2
0.0
0.0
0.0
0.0
61.7
Sweat plus sebum
Cadmium
82
0.1
0.2
0.0
0.0
0.0
0.1
1.6
Sweat plus sebum
Chromium
76
0.8
1.4
0.0
0.0
0.0
1.2
6.8
Sweat plus sebum
Cobalt
82
0.1
0.1
0.0
0.0
0.1
0.1
0.5
Sweat plus sebum
Copper
82
0.6
0.6
0.0
0.1
0.4
0.9
3.2
Sweat plus sebum
Iron
82
0.1
0.1
0.0
0.0
0.0
0.1
0.9
Sweat plus sebum
Lead
82
0.0
0.2
0.0
0.0
0.0
0.0
1.9
Sweat plus sebum
Magnesium
82
0.8
1.0
0.0
0.2
0.4
1.0
5.5
Sweat plus sebum
Manganese
82
1.9
1.8
0.0
0.3
1.5
3.0
7.6
Sweat plus sebum
Molybdenum
82
1.1
6.5
0.0
0.0
0.0
0.0
53.9
Sweat plus sebum
Nickel
82
0.5
1.0
0.0
0.0
0.2
0.7
6.5
Sweat plus sebum
Selenium
9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Sweat plus sebum
Strontium
82
1.7
2.3
0.0
0.4
0.9
1.9
9.6
Sweat plus sebum
Tin
80
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Sweat plus sebum
Zinc
82
0.1
0.1
0.0
0.0
0.1
0.1
0.3
a In vitro percent bioaccessibility was not calculated when analyte concentration in ICP/MS tire crumb constituent analysis (i.e., denominator of the % bioaccessibility
calculation) was less than 3 times of the corresponding reporting limit.
251
-------
Table 4-103. In Vitro Percent Bioaccessibility Results in Three Artificial Biofluids, Stratified by Recycling P
Artificial
Biofluid
Analytc
Recycling Plants
In Vitro %
Bioaccessibility -
Na
Recycling Plants
In Vitro %
Bioaccessibility -
Mcan±Standard
Deviation (%)
Recycling Plants
In Vitro %
Bioaccessibility -
Median (Min-
Max) (%)
Synthetic Turf
Fields In Vitro %
Bioaccessibility -
N"
Synthetic Turf
Fields In Vitro %
Bioaccessibility -
Mcan±Standard
Deviation (%)
Synthetic Turf
Fields In Vitro %
Bioaccessibility -
Median (Min-
Max) (%)
p-valucb'
Gastric fluid
Aluminum
27
0.2±0.2
0.2 (0-0.8)
55
0.8±0.5
0.7 (0.1-2.6)
< 0.0001
Gastric fluid
Antimony
27
2.4±1.8
2.7 (0-6.1)
54
0.9±1.6
0 (0-7.6)
N/A
Gastric fluid
Arsenic
27
1.2±1.6
0 (0-5.3)
55
1.1±1.7
0 (0-8.4)
N/A
Gastric fluid
Barium
27
6.5±3.2
5.8 (0.9-13.1)
55
7.2±5.4
6.1 (0.2-29.8)
0.92
Gastric fluid
Beryllium
24
1.4±4
0 (0-16.3)
31
4.4±8
0 (0-38.3)
N/A
Gastric fluid
Cadmium
27
0.5±0.3
0.6 (0.1-1.6)
55
0.5±0.7
0.3 (0-3.5)
0.049
Gastric fluid
Chromium
27
3.1±2.5
2.5 (0-8.4)
49
4.6±9
3 (0-55.1)
0.99
Gastric fluid
Cobalt
27
0.2±0.1
0.2 (0.1-0.3)
55
0.3±0.3
0.3 (0-1.2)
0.001
Gastric fluid
Copper
27
13.7±4.1
13.2 (5.8-20.5)
55
5.9±2.8
5.6 (1.6-15.2)
< 0.0001
Gastric fluid
Iron
27
9.8±3
9.6 (4.9-17)
55
5.5±3.6
5.3 (0.1-14.3)
< 0.0001
Gastric fluid
Lead
27
1.8±2.4
1.3 (0.3-13.5)
55
3.2±2.1
2.9 (0.2-9.6)
< 0.0001
Gastric fluid
Magnesium
27
2.2±1.4
1.8 (1-7.5)
55
4.1±3.7
3.8 (0.1-20.5)
0.036
Gastric fluid
Manganese
27
13.6±5.4
12.1 (3.5-27.1)
55
12.5±9.1
11.3 (0-35)
0.32
Gastric fluid
Molybdenum
27
3.2±4.2
0 (0-16.7)
54
0.9±3.5
0(0-24.1)
N/A
Gastric fluid
Nickel
27
1.2±1.1
0.9 (0-3.5)
55
3.1±5.4
1.8 (0-32.6)
0.016
Gastric fluid
Selenium
6
0.9±2.2
0 (0-5.5)
3
0±0.1
0(0-0.1)
N/A
Gastric fluid
Strontium
27
3.3±1.9
3 (0-8.7)
55
8.1±8.7
6.3 (0-42.4)
0.055
Gastric fluid
Tin
27
0.3±1.4
0 (0-7.3)
53
0.1±0.9
0 (0-6.8)
N/A
Gastric fluid
Zinc
27
0.7±0.2
0.7 (0.3-1.1)
55
1±0.6
0.9 (0.2-2.5)
0.02
Saliva
Aluminum
27
o±o
0 (0-0)
55
0±0.1
0 (0-0.3)
N/A
Saliva
Antimony
27
0.3±0.5
0 (0-2)
55
0.8±2.2
0 (0-14.9)
N/A
Saliva
Arsenic
27
o±o
0 (0-0)
55
0.3±0.9
0 (0-4.5)
N/A
Saliva
Barium
27
0.1±0.2
0 (0-1)
55
0.2±0.3
0.1 (0-1.4)
N/A
Saliva
Beryllium
24
0.3±1.1
0 (0-5.1)
31
0.7±2.9
0 (0-15.9)
N/A
Saliva
Cadmium
27
o±o
0(0-0.1)
55
0±0.1
0 (0-0.5)
N/A
Saliva
Chromium
27
0.2±0.5
0 (0-2.2)
49
0.3±1.3
0 (0-8.7)
N/A
ant vs. Synthetic Turf Field Samples
252
-------
Table 4-103 Continued
Artificial
Biofluid
Analvtc
Recycling Plants
In Vitro %
Bioaccessihilitv -
N"
Recycling Plants
In Vitro %
Bioaccessihilitv -
Mcan±Standard
Deviation (%)
Recycling Plants
In Vitro %
Bioaccessihilitv -
Median (Min-
Max) (%)
Synthetic Turf
Fields In Vitro %
Bioaccessihilitv -
N"
Synthetic Turf
Fields In Vitro %
Bioaccessihilitv -
Mcan±Standard
Deviation (%)
Synthetic Turf
Fields In Vitro %
Bioaccessihilitv -
Median (Min-
Max) (%)
p-valucb'1
Saliva
Cobalt
27
o±o
0(0-0.1)
55
0±0.1
0 (0-0.2)
0.11
Saliva
Copper
27
0±0.1
0 (0-0.6)
55
0.4±0.7
0.1 (0-4.3)
N/A
Saliva
Iron
27
0.1±0.1
0 (0-0.6)
55
0±0.1
0 (0-0.6)
N/A
Saliva
Lead
27
0±0.1
0 (0-0.5)
55
o±o
0(0-0.1)
N/A
Saliva
Magnesium
27
0.2±0.2
0.2 (0-0.7)
55
0.5±0.8
0.3 (0-5)
0.18
Saliva
Manganese
27
0.6±0.5
0.7 (0-1.9)
55
1.4±5
0 (0-32.2)
N/A
Saliva
Molybdenum
27
o±o
0 (0-0)
55
1.2±7.8
0 (0-57.6)
N/A
Saliva
Nickel
27
0.1±0.3
0 (0-1.4)
55
0.3±0.9
0 (0-5)
N/A
Saliva
Selenium
6
o±o
0 (0-0)
3
o±o
0 (0-0)
N/A
Saliva
Strontium
27
0.2±0.3
0 (0-0.8)
55
0.3±0.6
0(0-3.1)
N/A
Saliva
Tin
27
o±o
0 (0-0)
53
o±o
0 (0-0)
N/A
Saliva
Zinc
27
o±o
0(0-0.1)
55
o±o
0 (0-0)
0.30
Sweat plus sebum
Aluminum
27
o±o
0(0-0.1)
55
0±0.1
0 (0-0.3)
N/A
Sweat plus sebum
Antimony
27
0.3±0.4
0.2 (0-1.4)
55
0.2±0.6
0 (0-3.9)
N/A
Sweat plus sebum
Arsenic
27
0.1±0.5
0 (0-2.4)
55
0.5±1
0 (0-4.4)
N/A
Sweat plus sebum
Barium
27
0.9±0.8
0.8 (0-4.4)
55
0.8±1
0.6 (0-4.8)
0.21
Sweat plus sebum
Beryllium
24
10.5±16.8
0 (0-61.7)
31
0.2±1.3
0(0-7.1)
N/A
Sweat plus sebum
Cadmium
27
0.2±0.4
0 (0-1.6)
55
0±0.1
0 (0-0.4)
N/A
Sweat plus sebum
Chromium
27
0.7±1.4
0 (0-6.8)
49
0.9±1.3
0 (0-4.7)
N/A
Sweat plus sebum
Cobalt
27
0.1±0
0.1 (0-0.2)
55
0.1±0.1
0.1 (0-0.5)
0.08
Sweat plus sebum
Copper
27
0.4±0.4
0.2 (0-1.7)
55
0.7±0.7
0.6 (0-3.2)
0.09
Sweat plus sebum
Iron
27
0.1±0.2
0.1 (0-0.9)
55
0±0.1
0 (0-0.6)
N/A
Sweat plus sebum
Lead
27
o±o
0(0-0.1)
55
0±0.3
0 (0-1.9)
N/A
Sweat plus sebum
Magnesium
27
0.4±0.2
0.4 (0.1-1)
55
lil.l
0.5 (0-5.6)
0.11
Sweat plus sebum
Manganese
27
2.2±1.6
2 (0.3-5.7)
55
1.7±1.8
1.4 (0-7.6)
0.08
Sweat plus sebum
Molybdenum
27
2±10.4
0 (0-53.9)
55
0.7±3.3
0(0-22.1)
N/A
253
-------
Table 4-103 Continued
Artificial
Biofluid
Analvtc
Recycling Plants
In Vitro %
Bioaccessibility -
Na
Recycling Plants
In Vitro %
Bioaccessibility -
Mcan±Standard
Deviation (%)
Recycling Plants
In Vitro %
Bioaccessibility -
Median (Min-
Max) (%)
Synthetic Turf
Fields In Vitro %
Bioaccessibility -
N"
Synthetic Turf
Fields In Vitro %
Bioaccessibility -
Mcan±Standard
Deviation (%)
Synthetic Turf
Fields In Vitro %
Bioaccessibility -
Median (Min-
Max) (%)
P-valucbl
Sweat plus sebum
Nickel
27
0.3±0.4
0(0-1.3)
55
0.7±1.2
0.2 (0-6.5)
N/A
Sweat plus sebum
Selenium
6
o±o
0 (0-0)
3
o±o
0 (0-0)
N/A
Sweat plus sebum
Strontium
27
0.6±0.5
0.5 (0-1.6)
55
2.3±2.7
1.1 (0-9.6)
0.001
Sweat plus sebum
Tin
27
o±o
0 (0-0)
53
o±o
0 (0-0)
N/A
Sweat plus sebum
Zinc
27
0.1±0.1
0.1 (0-0.3)
55
0.1±0.1
0.1 (0-0.3)
0.74
11 In vitro percent bioaccessibility was not calculated when analyte concentration in tire crumb constituent analysis (i.e., denominator of the % bioaccessibility calculation)
was less than 3 times the corresponding reporting limit.
b p-values for Kruskal Wallis test between the recycling plant samples and synthetic turf field samples
0 N/A = Not available for analytes/artificial fluids with less than 50% detection rate
Table 4-104. Reported In Vitro Bioaccessible Metal Concentrations in Artificial Biofluid Extracts for Tire Crumb Samples Collected on Synthetic
Turf Fields3
Artificial Biotluidsb-'
Analvtc
This study -
N
This study -
> Limit of
Detection
(%)
This study-
In Vitro
Bioaccessible
Concentration
Range
(mg/kg TCR)
Literatu re-
N
Literature-
> Limit of
Detection
(%)
Literatu re -
In Vitro
Bioaccessible
Concentration
Range
(mg/kg TCR)
Literatu re - Reference
Gastric fluid or
Digestive fluids
Antimony
55
38
0-3.6
2
0
Max: < LOD
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Arsenic
55
29
0-0.019
2
0
Max: < LOD
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Arsenic
55
29
0-0.019
7
0
<3.0
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Barium
55
100
0.073 - 1.8
2
N/A
Max: 6
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Beryllium
55
31
0-0.0052
7
0
<0.40
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Cadmium
55
55
0-0.064
2
0
Max: < LOD
Pronk et al., 2018
254
-------
Table 4-104 Continued
Artificial
Biofluidsbc
Analytc
This study -
N
This study -
> Limit of
Detection
(%)
This study -
In Vitro
Bioacccssiblc
Concentration
Range
(mg/kg TCR)
Literatu re -
N
Litcratu re -
> Limit of
Detection
(%)
Literatu re -
In Vitro
Bioacccssiblc
Concentration
Range
(mg/kg TCR)
Literatu re - Reference
Gastric fluid or
Digestive fluids
Cadmium
55
55
0-0.064
7
100
2.5-11
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Cadmium
55
55
0-0.064
5
N/A
Max: < LOD
RIVM, 2017
Gastric fluid or
Digestive fluids
Chromium
55
64
0-0.71
2
N/A
Max: 1
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Chromium
55
64
0-0.71
7
0
<6.0
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Cobalt
55
100
0.072 - 1
2
N/A
Max: 2
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Cobalt
55
100
0.072-1
5
N/A
Max: 2
RIVM 2017
Gastric fluid or
Digestive fluids
Copper
55
100
0.25-5.2
2
N/A
Max: 78
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Copper
55
100
0.25-5.2
7
0
<20
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Lead
55
100
0.16-2.8
2
N/A
Max: 9
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Lead
55
100
0.16-2.8
7
100
2.5-260
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Lead
55
100
0.16-2.8
5
N/A
Max: 9
RIVM, 2017
Gastric fluid or
Digestive fluids
Lead
55
100
0.16-2.8
26
100
10.7-61.2
U.S. EPA, 2009
Gastric fluid or
Digestive fluids
Magnesium
55
98
0.12-66
7
0
<900
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Molybdenum
55
7
0-0.048
2
0
Max:
-------
Table 4-104 Continued
Artificial
Biofluidsbc
Analytc
This study -
N
This study -
> Limit of
Detection
(%)
This study -
In Vitro
Bioacccssiblc
Concentration
Range
(mg/kg TCR)
Literatu re -
N
Litcratu re -
> Limit of
Detection
(%)
Literatu re -
In Vitro
Bioacccssiblc
Concentration
Range
(mg/kg TCR)
Literatu re - Reference
Gastric fluid or
Digestive fluids
Selenium
55
4
0-0.0084
2
N/A
Max: 1
Pronk et al., 2018
Gastric fluid or
Digestive fluids
Selenium
55
4
0-0.0084
7
0
<2.0
Pavilonis et al., 2014
Gastric fluid or
Digestive fluids
Tin
55
0
0 -
-------
Table 4-104 Continued
Artificial
Biofluidsbc
Analvtc
This study -
N
This study -
> Limit of
Detection
(%)
This study -
In Vitro
Bioaccessible
Concentration
Range
(mg/kg TCR)
Literatu re -
N
Litcratu re -
> Limit of
Detection
(%)
Literatu re -
In Vitro
Bioaccessible
Concentration
Range
(mg/kg TCR)
Literatu re - Reference
Sweat or Sweat
plus sebum
Lead
55
18
0-0.19
7
N/A
Max: 0.07
RIVM. 2017
Sweat or Sweat
plus sebum
Magnesium
55
95
0-18
7
0
< 10
Pavilonis et al.. 2014
Sweat or Sweat
plus sebum
Selenium
55
35
0-0.0051
7
0
<0.70
Pavilonis et al.. 2014
a mg/kg TCR = milligrams analyte/kilogram tire crumb rubber; LOD = Limit of detection; N/A= not available
b Pavilonis et al. 2014 tested bioaccessibility in artificial digestive fluids, which included a mixture of artificial saliva, gastric fluid, and intestinal fluid. Pronk et al. 2018
tested bioaccessibility in artificial gastric/intestinal juices.
0 This study tested bioaccessibility in artificial sweat in tubes coated with artificial sebum, while all other studies assessed bioaccessibility in artificial sweat and did not
use artificial sebum.
Table 4-105. Reported//? Vitro Bioaccessible Metal Concentrations in Artificial Bio
luid Extracts for New/Unused Tire Crumb Samples
Artificial
Biofluid
Analvtc
This study -
N
This study -
> Limit of
Detection (%)
This study -
In Vitro Bioaccessible
Concentration Range
(mg/kg TCR)
Pavilonis et al. 2014 -
N
Pavilonis et al. 2014 -
> Limit of Detection
(%)
Pavilonis et al. 2014 -
In Vitro Bioaccessible
Concentration Range
(mg/kg TCR)
Gastric fluid or
Digestive fluid
Arsenic
27
37
0-0.012
6
50
<0.10-0.48
Gastric fluid or
Digestive fluid
Beryllium
27
15
0-0.0036
6
0
<0.40
Gastric fluid or
Digestive fluid
Cadmium
27
100
0.00059 - 0.007
6
0
<4.0
Gastric fluid or
Digestive fluid
Chromium
27
74
0-0.3
6
0
<7.0
Gastric fluid or
Digestive fluid
Copper
27
100
1.1-20
6
67
<20-32
Gastric fluid or
Digestive fluid
Lead
27
100
0.056-0.72
6
100
5.3-66
257
-------
Table 4-105 Continued
Artificial
Biofluid
Analytc
This study -
N
This study -
> Limit of
Detection (%)
This study -
In Vitro Bioacccssiblc
Concentration Range
(mg/kg TCR)
Pavilonis ct al. 2014 -
N
Pavilonis ct al. 2014 -
> Limit of Detection
(%)
Pavilonis ct al. 2014 -
In Vitro Bioacccssiblc
Concentration Range
(mg/kg TCR)
Gastric fluid or
Digestive fluid
Magnesium
27
100
2.2-18
6
17
< 1000 - 4600
Gastric fluid or
Digestive fluid
Selenium
27
4
0-0.011
6
17
<0.90-1.5
Sweat or Sweat
plus sebum
Arsenic
27
0
0-0.005
9
0
<0.50
Sweat or Sweat
plus sebum
Beryllium
27
37
0-0.0084
9
0
<0.20
Sweat or Sweat
plus sebum
Cadmium
27
41
0-0.0068
9
11
<0.090-0.11
Sweat or Sweat
plus sebum
Chromium
27
30
0-0.084
9
100
0.70-1.2
Sweat or Sweat
plus sebum
Copper
27
85
0-0.59
9
44
<0.080-0.54
Sweat or Sweat
plus sebum
Lead
27
0
0-0.0068
9
100
0.090- 1.6
Sweat or Sweat
plus sebum
Magnesium
27
100
0.32-3.1
9
78
< 7.0 - 980
Sweat or Sweat
plus sebum
Selenium
27
0
0-0
9
0
< 1.9
11 mg/kg TCR = milligrams analyte/kilogram tire crumb rubber
b This study tested bioaccessibility in artificial gastric fluid and artificial sweat in tubes coated with artificial sebum for unused recycling plant tire crumb rubber samples.
0 Pavilonis et al. 2014 tested bioaccessibility in artificial digestive fluids (which included a mixture of artificial saliva, gastric fluid, and intestinal fluid) and artificial sweat
for new tire crumb rubber infill samples. These samples were unused recycled tire crumb rubber from an architectural firm specializing in synthetic turf installation.
258
-------
Table 4-106. Reported In Vitro Percent Bioaccessibility of Metals in Artificial Biofluids, Stratified by Synthetic
Artificial
Biofluids
Analytc
This studv -
N
This study -
In Vitro %
Bioaccessibility
Range (%)
Litcraturc-
N
Litcratu rc -
In Vitro %
Bioaccessibility
Range (%)
Reference
Gastric fluid
Arsenic
55
00
1
o
2
< LOD
Zhang et al., 2008
Gastric fluid
Cadmium
55
0-3.4
2
< LOD
Zhang et al., 2008
Gastric fluid
Chromium
49
0-55.1
2
0-23.3
Zhang et al., 2008
Gastric fluid
Lead
55
0.2-9.6
2
24.7 - 44.2
Zhang et al., 2008
Gastric fluid
Lead
55
0.2-9.6
26
1.6-10.1
U.S. EPA, 2009
Saliva
Arsenic
55
0-4.5
1
< LOD
Zhang el al.. 2008
Saliva
Cadmium
55
0-0.5
1
< LOD
Zhang el al.. 2008
Saliva
Chromium
49
0-8.7
1
0
Zhang el al.. 2008
Saliva
Lead
55
0-0.13
1
0
Zhang el al.. 2008
a LOD = Limit of detection
Results from this study are generally consistent with a previous scoping study conducted by the U.S.
EPA (2009), as well as a recent report and publication by the Dutch National Institute for Public Health
and the Environment (Pronk et al., 2018; RIVM, 2017). Lead's percent in vitro bioaccessibility in
artificial gastric fluid was 0.2 - 9.6% (mean: 3.2±2.1%) among the 55 field samples in this study. In
comparison, the scoping study (U.S. EPA, 2009) found that the in vitro bioaccessibility for lead in
artificial gastric fluid ranged from 1.6 - 10.1% (mean: 4.7±2.3%) in 26 field samples. RIVM (2017)
tested five or seven field tire crumb samples and reported the maximum bioaccessible concentrations
(mg/kg TCR) for cadmium, cobalt and lead in artificial gastric fluid and sweat. Pronk et al. (2018)
reported maximum bioaccessible concentrations from 2 samples in artificial gastric/intestinal juices (16
metals) and 7 samples in artificial sweat (3 metals). Our findings on maximum bioaccessible
concentrations are consistent or lower than those reported by RIVM (Pronk et al., 2018; RIVM, 2017),
except for maximum lead concentration in artificial sweat (this study: 0.19 mg/kg TCR vs. RIVM: 0.07
mg/kg TCR).
Pavilonis et al. (2014) reported in vitro bioaccessible concentrations of eight metals in artificial digestive
biofluids (a mixture of artificial saliva, gastric and intestinal fluids), sweat, and lung biofluids in six or
nine new infills (from an architectural firm) and seven field tire crumb samples. The LODs in the
Pavilonis et al. (2014) study appear to be several orders of magnitude higher than this study. Further,
lead and cadmium results in the digestive biofluid extracts were higher than those from acid digestion of
tire crumb samples (i.e., percent in vitro bioaccessibility, if calculated, would be higher than 100%).
These factors made it difficult to compare the results between the Pavilonis et al. (2014) study and this
study.
Zhang et al. (2008) measured percent in vitro bioaccessibility of four metals in two field tire crumb
samples - one sample was extracted by artificial saliva and gastric fluid and another was extracted by
artificial gastric fluid and intestinal fluid. Arsenic and cadmium were not detected in any artificial fluid
extracts of samples, while chromium was detected in the gastric fluid extract of one sample. Lead was
detected in the artificial gastric fluid extract of both samples, with a calculated percent in vitro
bioaccessibility of 24.7 and 44.2%, respectively.
259
-------
It should be noted that in vitro bioaccessibility test results can be affected by many factors, including the
formulation of various artificial biofluids, methods for dissolution of materials in artificial biofluids,
analytical methods for measuring analytes in artificial biofluid extracts, analytical method for measuring
analytes in tire crumb samples, and the heterogeneity of the tire crumb material. As a result, caution
should be taken while interpreting and comparing bioaccessibility results across studies.
4.14 Microbiological Analysis
4.14.1 Targeted Microbial Analysis
Each of the 7 samples collected from the 40 synthetic turf fields were analyzed to determine
concentrations of the 16S ribosomal ribonucleic acid (rRNA) gene, S. aureus SA0140 protein gene and
the methicillin resistance gene (mecA). A complete list of the number of targeted molecules per gram of
tire crumb rubber in each sample are shown in Appendix S. An evaluation of the internal amplification
controls showed that 4 of the 280 samples indicated polymerase chain reaction (PCR) inhibition and
were removed from analysis. A summary of the targeted microbial gene concentrations from samples
collected at all fields is shown in Table 4-107. The mean concentration of 16S rRNA, S. aureus and
mecA gene molecules per gram of tire crumb rubber were 1.1 x 107, 19.9 and 109.5, respectively. The
variation in the number of targeted gene molecules measured from replicate samples of each field is
summarized in Table 4-108, with full results shown in Appendix S. Every sample from the 40 fields was
positive for 16S rRNA genes and the percent relative standard deviation ranged from 26.9 - 190.4%
across the fields. However, S. aureus SA0140 protein and mecA genes were detected less frequently. A
total of 17 (42.5%) fields had at least 1 sample with quantifiable S. aureus genes, while 28 {10%) fields
had a least 1 positive sample for the mecA gene.
The factors of facility (outdoor/indoor), geographical region and field age had statistically significant
impacts for the targeted gene quantities observed in the synthetic turf field samples. As shown in Table
4-109 and Figure 4-65, outdoor fields had statistically significant higher quantities of 16S rRNA genes
than indoor fields, while indoor fields had statistically significant higher quantities of S. aureus SA0140
and mecA genes than outdoor fields.
260
-------
Table 4-107. Summary of the Concentrations of the Targeted Microbial Genes Measured in Samples from Synthetic Turf Fieldsa'b
Gene Target
N
% > Limit
of Detection
Mean
(molecules/
g TCR
Standard
Deviation
(molecules/
g TCR)
% Relative
Standard
Deviation
10th
Percentile
(molecules/
g TCR)
25th
Percentile
(molecules/
g TCR)
50"'
Percentile
(molecules/
g TCR)
75th
Percentile
(molecules/
g TCR)
90th
Percentile
(molecules/
g TCR)
Maximum
(molecules/
g TCR)
16S rRNA gene
276
100
1.08E+07
1.45E+07
135
3.40E+05
9.19E+05
3.93E+06
1.51E+07
2.82E+07
8.70E+07
S. aureus SAO 140
protein
276
25.4
1.99E+01
8.06E+01
405
0
0
0
9.60E+00
4.79E+01
8.90E+02
mecA methicillin
resistance gene
276
51.1
1.10E+02
2.18E+02
200
0
0
4.70E+00
1.12E+02
3.86E+02
1.28E+03
1 molecules/g TCR = molecules/gram of tire crumb rubber; rRNA = Ribosomal ribonucleic acid
Table 4-108. Summary of the Variability in Targeted Microbial Gene Quantities Measured in Replicate Samples from Each Field
Gene Target"
Nu mber of
Fields
% Relative Standard Deviation
Mean
% Relative Standard Deviation
Standard Deviation
16S rRNA gene
40
63.9
34.1
S. aureus SAO 140 protein
17
154
79.2
mecA methicillin resistance gene
28
116
78.1
' rRNA = Ribosomal ribonucleic acid
Table 4-109. Mean Quantities of Targeted Microbial Genes in Outdoor and Indoor Synthetic Turf Fields3
Gene Target
Outdoor Fields
Mean
(logio molecules/
g TCR)
Outdoor Fields
Standard
Deviation
(login molecules/
g TCR)
Indoor Fields
Mean
(logio molecules/
g TCR)
Indoor Fields
Standard
Deviation
(login molecules/
g TCR)
IMann-
Whitncy
T-test
p-valuc
16S rRNA gene
6.9
0.6
5.9
0.6
<0.001
S. aureus SAO 140 protein
0
0.3
1.0
0.8
<0.001
mecA methicillin resistance gene
0.2
0.5
2.2
0.5
<0.001
a Outdoor fields (N=172); Indoorfields (N=104)
b logio molecules/g TCR = logio molecules/gram of tire crumb rubber; rRNA = Ribosomal ribonucleic acid
261
-------
P< 0.001
a.
_oj
3
u
_0)
O
E
s
3?
P< 0.001
P< 0.001
Outdoor (100%) Indoor (100%)
16S rRNA gene
Outdoor (2%) Indoor (63%)
S. aureus SA0140 protein gene
Outdoor (22%) Indoor (100%)
mecA methicillin-resistance gene
Figure 4-65. Mean loglO concentrations of 16S rRNA genes, S. aureus SA0140 protein gene and mecA
methicillin-resistance genes in samples collected from outdoor (n=172) and indoor (n=104) artificial turf
fields. Numbers in parentheses specify the percentage of positive samples. Error bars represent standard
deviation. P-values indicate results of Mann-Whitney Rank Sum Test. [rRNA = Ribosomal ribonucleic acid;
mecA = methicillin-resistance gene; TCR = Tire crumb rubber]
The fields in the oldest age category (2004-2008) tended to have higher quantities of the targeted
microbial genes than fields in the youngest age category (Table 4-110). An ANOVA on Ranks shows
that statistically significant different gene quantities exist across the three field age categories. The
geographical region in which the sampled synthetic turf fields is located also influences quantities of the
targeted microbial genes based on ANOVA on Ranks (Table 4-111). It is important to note, however,
that the influence of outdoor vs. indoor fields may be impacting results for field age (where there was
only one indoor field in the 2013-2016 age group) and census region (where there were higher
proportions of indoor fields in the Midwest and Northeast regions than in the south and west regions).
When considering samples from outdoor fields only, older fields had statistically significant increased
concentrations of 16S rRNA genes than younger fields, but field age did not impact concentrations of S.
aureus or mecA genes (Table 4-110), likely due to a large number of samples with non-detectable
values. Likewise, geographical region did not affect concentrations of S. aureus genes, but statistically
significant different concentrations were observed across the regions for 16S rRNA and mecA genes in
the outdoor field samples analyzed; highest concentrations were measured in the Midwest and lowest
concentrations were detected in the West (Table 4-111). An examination of samples from indoor fields
revealed that field age did have a statistically significant impact on indoor fields, as youngest fields
showed the highest concentrations and intermediate-aged fields had the lowest concentration of all
targeted microbial genes (Table 4-110). Similarly, geographical region had a statistically significant
impact for concentrations of the targeted microbial genes in indoor field samples, but the trends varied.
Highest concentrations of 16S rRNA genes were measured in the Midwest, while highest concentrations
of S. aureus and mecA were detected in the West (Table 4-111).
Some fields were disinfected with biocides. In total, biocides were applied to 11 fields (4 outdoor and 7
indoor fields), while 5 fields (2 outdoor and 3 indoor) had missing information about biocide usage. An
ANOVA of biocide usage on indoor and outdoor fields showed that biocides had a statistically
significant association with reduced quantities of 16S rRNA genes in outdoor fields (Table 4-112).
However, biocide usage had no impact on concentrations of 16S rRNA genes in indoor fields or the
other microbial gene markers in either indoor or outdoor fields.
262
-------
Table 4-110. Mean Quantities of Targeted Microbial Genes in Synthetic Turf Field Samples, by Installation Age Group3
Gene Target
Synthetic
Turf .Field
Data Set
Fields
Installed
2004 - 2008
N
Fields
Installed
2004 - 2008
Mean
(logio
molecules/
g TCR)
Fields
Installed
2004 - 2008
Standard
Deviation
(logio
molecules/
g TCR)
Fields
Installed
2009-2012
N
Fields
Installed
2009-2012
Mean
(logio
molecules/
g TCR)
Fields
Installed
2009-2012
Standard
Deviation
(logio
molecules/
g TCR)
Fields
Installed
2013-2016
N
Fields
Installed
2013-2016
Mean
(logio
molecules/
g TCR)
Fields
Installed
2013-2016
(logio
molecules/
g TCR)
ANOVA
On Ranks
p-valuc
16S rRNA gene
All
76
6.7
0.8
124
6.4
0.8
76
6.6
0.7
0.034
16S rRNA gene
Outdoor
34
7.3
0.3
69
7.0
0.5
69
6.7
0.7
<0.001
16S rRNA gene
Indoor
42
6.1
0.6
55
5.7
0.5
7
6.2
0.1
<0.001
S. aureus SAO 140
protein
All
76
0.6
0.8
124
0.4
0.8
76
0.2
0.5
< 0.001
S. aureus SAO 140
protein
Outdoor
34
0
0
69
0.1
0.5
69
0
0
0.047
S. aureus SAO 140
protein
Indoor
42
1.2
0.8
55
0.9
0.9
7
1.7
0.2
0.013
mecA methicillin
resistance gene
All
76
1.4
1.2
124
1.1
1.1
76
0.4
0.8
<0.001
mecA methicillin
resistance gene
Outdoor
34
0.2
0.5
69
0.3
0.6
69
0.2
0.4
0.953
mecA methicillin
resistance gene
Indoor
42
2.3
0.5
55
2.1
0.4
7
2.6
0.1
0.007
a logio molecules/g TCR = logio molecules/gram of tire crumb rubber; ANOVA = Analysis of variance; rRNA = Ribosomal ribonucleic acid
263
-------
Table 4-111. Mean Quantities of Targeted Microbial Genes in Synthetic Turf Field Samples, by U.S. Geographical Regions8
Gene
Svnthctic
Northeast
Northeast
Northeast
South
South
South
Midwest
Midwest
Midwest
West
West
West
ANOVA
Target
Turf
Region -
Region -
Region -
Region -
Region -
Region -
Region -
Region -
Region -
Region -
Region -
Region -
On
Field
N
Mean
Standard
N
Mean
Standard
N
Mean
Standard
N
Mean
Standard
Ranks
Data Set
(log™
Deviation
(logio
Deviation
(logio
Deviation
(logio
Deviation
p-valuc
molecules
(logio
molecules
(logio
molecules
(logio
molecules
(logio
/g TCR)
molecules
/g TCR)
/g TCR)
molecules
/g TCR)
/g TCR)
molecules
/g TCR)
/g TCR)
molecules
/g TCR)
16S rRNA
All
63
6.6
0.9
91
6.8
0.7
55
6.1
0.8
67
6.5
0.5
<0.001
gene
16S rRNA
Outdoor
35
7.2
0.4
77
6.9
0.7
14
7.3
0.2
46
6.6
0.4
<0.001
gene
16S rRNA
Indoor
28
5.8
0.8
14
6.1
0.3
41
6.8
0.5
21
6.2
0.5
0.002
gene
S. aureus
All
63
0.6
0.8
91
0.2
0.6
55
0.5
0.8
67
0.5
0.8
0.010
SAO 140
protein
S. aureus
Outdoor
35
0.03
0.2
77
0
0
14
0
0
46
0.1
0.5
0.131
SAO 140
protein
S. aureus
Indoor
28
1.2
0.9
14
1.3
0.8
41
0.7
0.8
21
1.4
0.6
0.006
SAO 140
protein
mecA
All
63
1.1
1.1
91
0.7
0.9
55
1.7
0.9
67
0.8
1.1
<0.001
methicillin
resistance
gene
mecA
Outdoor
35
0.26
0.6
77
0.1
0.5
14
0.5
0.6
46
0.07
0.3
0.005
methicillin
resistance
gene
mecA
Indoor
28
2.1
0.5
14
1.4
0.6
41
2.1
0.5
21
2.4
0.3
0.008
methicillin
resistance
gene
11 logio molecules/g TCR = logio molecules/gram of tire crumb rubber; ANOVA = Analysis of variance; rRNA = Ribosomal ribonucleic acid
264
-------
Table 4-112. Mean Quantities of Targeted Microbial Genes in Synthetic Turf Fields, with and without Biocide Applicationa b
Gene Target
Synthetic
Turf
Field
Data Set
With Biocide
Application -
N
With Biocide
Application -
Mean
(logio molecules/
g TCR)
With Biocide
Application -
Standard Deviation
(logio molecules/
g TCR)
Without
Biocide
Applicatio
n-N
Without Biocide
Application -
Mean
(logio molecules/
g TCR)
Without Biocide
Application
Standard Deviation
(logio molecules/
g TCR)
ANOVA
/>-valuc
16S rRNA gene
Outdoor
26
6.74
0.49
132
6.90
0.63
0.024
16S rRNA gene
Indoor
49
5.93
0.51
34
6.06
0.60
0.402
S. aureus SAO 140
protein
Outdoor
26
0.05
0.23
132
0.05
0.33
0.691
S. aureus SAO 140
protein
Indoor
49
1.03
0.79
34
1.00
0.91
0.993
mecA methicillin
resistance gene
Outdoor
26
0.19
0.57
132
0.22
0.45
0.329
mecA methicillin
resistance gene
Indoor
49
2.26
0.45
34
2.30
0.48
0.763
a logio molecules/g TCR = logio molecules/gram of tire crumb rubber; ANOVA = Analysis of variance; rRNA = Ribosomal ribonucleic acid
b Biocides were applied to 11 fields (4 outdoor and 7 indoor fields), while 5 fields (2 outdoor and 3 indoor) had missing information about biocide usage
-------
Few studies have investigated the microbiological composition of synthetic turf fields with tire crumb
rubber infill. McNitt et al. (2007) reported average total bacterial counts of 4.2 logio colony forming
units (CFU) per gram of tire crumb rubber from 20 infilled synthetic turf systems in Pennsylvania using
non-selective culture media. Outdoor fields tended to have more total bacteria than indoor fields,
although only three indoor fields were examined. Presence of S. aureus was investigated using selective
media but was not detected, and presence of the mecA methicillin resistance gene was not investigated.
Vidair (2010) sampled tire crumb rubber from five soccer fields in the San Francisco Bay Area. The
maximum concentration of total bacteria reported in these fields was 4.7 logio CFU per gram of tire
crumb rubber infill. While two species of Staphylococcus (S. warneri and S. hominis) were identified in
tire crumb rubber, S. aureus was not detected. Additionally, methicillin-resistant Staphylococcus aureus
was not detected. Finally, Bass & Hintze (2013) examined two synthetic turf fields in Utah. One field
was in use for a year, while the other field had been in use for 7 years. Total bacteria concentrations
averaged 8.0 logio CFU per gram of tire crumb rubber on the old field and 5.4 logio CFU per gram of
tire crumb rubber on the new field. Staphylococcus spp. concentrations of 2.4 logio CFU per gram of tire
crumb rubber were reported on the new turf and 3.8 log 10 CFU per gram of tire crumb rubber on older
turf, but presence of S. aureus was not confirmed, and presence of methicillin resistance was not
investigated.
Although the methodologies differ between previous work described above and the results described
here, some similar trends were observed. The mean concentration of rRNA genes observed across 40
indoor and outdoor fields was 7.0 logio molecules per gram of tire crumb rubber, which equates roughly
to 6.4 logio bacterial cells per gram of tire crumb rubber (bacterial cells have an average of 4.2 copies of
16S rRNA genes; Vetrovsky & Baldrian, 2013) and is within the range of concentrations (4.2-8.0 logio
CFU per gram of tire crumb rubber) reported previously. Similar to previous reports, we observed
higher concentrations of total bacteria in outdoor fields compared to indoor fields and in older outdoor
fields compared to newer outdoor fields. None of the previous studies detected S. aureus or methicillin-
resistant S. aureus using culture methods in tire crumb rubber samples. We observed the presence of
genes corresponding to S. aureus and methicillin resistance in bacterial populations isolated from 42%
and 70% of artificial turf field samples, respectively. This may be due to the increased sensitivity of the
PCR-based methods used here compared to the culture-based methods employed in the previous studies.
4.14.2 Non-targeted Microbial Analysis
A total of 280 samples collected from 40 synthetic turf fields were examined to characterize the
microbial community by analysis of the 16S rRNA gene. Of the 280 synthetic turf field samples, one
was excluded during quality filtering of 16S rRNA sequence reads, 28 were removed due to failures of
quality controls during processing, and 8 were omitted since they contained less than 1000 16S rRNA
sequence reads (i.e., the quality control threshold). A summary of the total number of 16S rRNA
sequence reads obtained per sample from all fields is listed in Table 4-113. Collectively, these samples
contained 1424 operational taxonomic units (OTUs) or unique bacterial taxa. Classification of these
unique taxa was performed using the Ribosomal Database Project Classifier (Michigan State University,
Lansing, MI, USA) to the lowest taxonomic level possible. The OTUs that contribute 90% of the total
16S rRNA gene sequence reads and their count for each synthetic turf field sample, along with their
taxonomic classification, is listed in a database that is available online at the study's website (see
https://www.epa.gov/tirecrumb).
266
-------
Table 4-113. Summary of Total 16S rRNA Sequence Read Counts Obtained from the Non-targeted Microbial
Community Analysis of Synthetic Turf Fields
Gene Target
Mean
Standard
Deviation
% Relative
Standard
Deviation
10th
Percentile
25th
Percentile
50"'
Percentile
75th
Percentile
90th
Percentile
Maximum
16S rRNA
sequence read
counts per
sample3
1.24E+04
6.79E+03
55
3.87E+03
6.70E+03
1.13E+04
1.80E+04
2.11E+04
2.89E+04
arRNA= ribosomal ribonucleic acid; N=243 samples; % > Limit of Detection = 100%
Vidair (2010) profiled the bacterial community in tire crumb rubber collected from five fields. This
census was conducted by selecting the three most prominent types of bacteria isolated on culture plates.
Identification was performed using the analytical profile index (API®) System of biochemical tests and
can provide species-level resolution. A total of 20 unique taxa were identified, of which 18 species were
identified to species and 2 taxa were identified to genus. Using a genetic-based technique, we identified
1424 unique taxa in the bacterial communities of tire crumb rubber collected from 36 artificial turf
fields. Although the genetic methods allow more thorough profile of community composition,
taxonomic classification is limited to genus-level. A comparison of community members at the genus-
level shows that the 20 genera identified in the Vidair (2010) study are present in tire crumb rubber
bacterial communities observed in this study.
4.15 Initial Testing of Silicone Wristbands
Collecting samples to measure personal exposures to chemicals is very challenging for people engaged
in sport activities on synthetic turf fields and for athletic and physical training activities in general.
Personal sampling devices must be relatively small, must not restrict research participant activities, and
must be safe to wear, even during vigorous activities. Due to the relatively short activity periods and
relatively low concentrations of chemicals, personal sampling devices must also overcome the challenge
of collecting sufficient chemical amounts for accurate measurements.
The use of silicone wristbands as a tool for personal and area chemical sample collection in exposure
assessment research has increased in popularity. Silicone wristbands can serve as passive samplers for
many types of organic chemicals and are especially effective for chemicals present in air. With no power
requirements, minimal participant burden and interaction requirements and their ease of use, these
silicone wristbands may be useful for personal sample collection during sport activities. There is interest
in how silicone wristbands might be used in future exposure measurement studies for synthetic field
users, where bulky air sampling equipment can't be worn safely during intense athletic activity. A
critical question regarding their suitability for synthetic turf field personal sampling is whether, and at
what rate, they collect chemicals of interest associated with tire crumb rubber or other field materials.
4.15.1 Dynamic Chamber Testing of Wristbands
As a first step towards determining feasibility, it is important to understand how to measure the relevant
chemicals in wristbands and to assess the sorption of chemicals when exposed to tire crumb rubber
materials. Exploratory tests were designed to provide an initial assessment and demonstration. The
results are intended to inform evaluation of the potential utility for personal monitoring and/or field air
monitoring in future synthetic turf field research studies. A small set of screening-level experiments
were performed in controlled dynamic emission chambers. The tests were designed to measure the
267
-------
amount of selected tire crumb rubber SVOCs absorbed to wristbands when covered with tire crumb
rubber, and the amount absorbed in wristbands suspended in the air above tire crumb rubber under
controlled conditions of temperature, humidity, and ventilation. The experimental approach and full
results for these initial silicone wristband tests are reported in Appendix T.
The wristbands that were covered with tire crumb rubber absorbed targeted SVOC chemicals associated
with tire crumb rubber over a 6-day experiment. The amounts of chemicals absorbed were somewhat
proportional to their concentrations in the tire crumb rubber but appeared to be highly related to
chemical vapor pressures. The wristbands that were suspended in the chamber air above the tire crumb
rubber also absorbed measurable levels of most of the target SVOCs that had been emitted into the
chamber air during the 6-day experiment. Again, the amounts of chemicals absorbed were somewhat
proportional to their concentrations in the tire crumb rubber but appeared to be highly related to
chemical vapor pressures. For example, the 5- and 6-ring PAHs were emitted at very low or non-
measurable amounts into the chamber air, and likewise, were often near or below measurable levels for
wristband extracts. The controlled chamber conditions allowed estimation of effective sampling rates for
each SVOC that could be measured in the wristbands. These effective sampling rates allow estimations
of how long silicone wristbands might have to be deployed at synthetic turf fields to be able to measure
tire crumb rubber associated chemicals.
While the initial tests show that the wristbands have some promise as field area samplers, more field
testing is needed to confirm that measurable amounts of chemicals of interest can be measured in
reasonable time frames at both outdoor and indoor fields. It is likely that use of silicone wristbands as
personal samplers will require that participants wear the wristbands during multiple practice and/or
game days, with storage in a clean airtight container between uses. This intermittent sampling will likely
be needed to collect sufficient amounts of target chemicals for analysis. Pilot testing with athletes,
coaches, and/or referees would help provide more information regarding the suitability of silicone
wristbands as a personal sampling device for synthetic turf field users.
268
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5.0 Toxicity Reference Information
5.1 Background
The objective of the effort to characterize tire crumb rubber material was to identify and collate toxicity
reference information on potential chemical constituents of tire crumb rubber from existing on-line
databases and literature sources. To achieve this goal, a list of potential chemical constituents was
developed as part of the Literature Review/Gaps Analysis (LRGA), based on chemicals identified in the
various studies reviewed. More than 350 distinct chemical compounds potentially associated with
recycled tire crumb rubber were reported in the appendix of the peer-reviewed white paper summarizing
the LRGA results, State-of-Science Literature Review/Gaps Analysis, White Paper Summary of Results.
The white paper and constituents list have been reproduced in Appendix C. The Summary Spreadsheet
of the Literature Review/Gaps Analysis includes the name of these chemicals, Chemical Abstracts
Service (CAS) numbers, synonyms, and concentrations reported in the literature. Some major classes of
constituents identified in the literature include inorganics and VOCs/SVOCs. Frequently studied
inorganics include lead, zinc, cadmium and chromium, and frequently studied VOCs/SVOCs include
benzothiazole and PAHs. Less frequently studied constituents include microbials and a variety of
complex organic compounds.
5.2 Approach
Extant toxicity reference information was compiled for the potential tire crumb rubber chemical
constituents identified in the LRGA. Data gaps were identified, including chemicals for which toxicity
reference data were unavailable. The information sources used to gather the toxicity reference
information are shown in Table 5-1.
Table 5-1. Information Sources Used to Compile Reference Toxicity Information
Information Source
URL
Description
EPA Integrated Risk
Information System (IRIS)
httos ://cfoub .era. eov/ncea/iris2/atoz
.cfm
Provides toxicity values for health effects
resulting from chronic exposure to chemicals,
including cancer and noncancer hazard
characterization and oral reference doses
(RfDs), inhalation reference concentrations
(RfCs), oral slope factors (OSFs), and
inhalation unit risks (IURs).a
EPA Provisional Peer-reviewed
Toxicity Value (PPRTV)
httos ://hliDDrtv. ornl. sov/auickview/
DDIlV.DllD
PPRTVs have been developed for EPA's
Superfund program and can also include
provisional RfDs and RfCs for non-cancer
effects and provisional OSFs and IURs for
cancer.
EPA Health Effects
Assessment Summary Table
(HEAST)
httos ://cfoub .era. eov/ncea/risk/reco
rdisolav.cfm?deid=2877
Provides oral and inhalation toxicity values
developed for EPA's Superfund program.
Agency for Toxic Substances
and Disease Registry (ATSDR)
Minimal Risk Levels (MRLs)
litto ://www. atsdr. ede. eov/mrls/odfs/
atsdr mrls.Ddf
Like RfDs, ATSDR oral and inhalation MRLs
represent estimates of the daily human
exposure to a hazardous substance that is likely
to be without appreciable adverse non-cancer
health effects over a specified duration of
exposure.
269
-------
Table 5-1 Continued
Information Source
URL
Description
World Health Organization
(WHO) International
Programme on Chemical Safety
(IPCS) Concise International
Chemical Assessment
Documents (CICAD)
litto ://www. who .int/rocs/rmblication
s/cicad/cicads alohabetical/en/
Provides summaries of potential health effects
of chemicals on human health and the
environment.
International Agency for
Research on Cancer (IARC)
Monographs
1 it t d ://mo no ara dlis. ia rc. fr/EN G/C1 a s
sification/latest classif.oho
Provides summary information on chemicals
that can increase the risk of human cancer.
California Environmental
Protection Agency (CalEPA)
Toxicity Criteria Database
htto ://oehha. ca. eov/t>rot>65/t>df/P65 s
afeharborlevels040116.odf
1 it t d : //www. o c 111 la. c a. ao v/a i r/a 11 re 1 s.
html
https://oehha.ca. eov/media/CPFs04
2909.t)df
Provides No Significant Risk Levels (NSRLs)
for carcinogens, Maximum Allowable Dose
Levels (MADLs) for chemicals causing
reproductive toxicity, and Reference Exposure
Levels (RELs) which represent air
concentrations at or below which no adverse
health effects are anticipated to occur in human
populations, including sensitive subgroups.
Occupational Safety and Health
Administration (OSHA)
Permissible Exposure Limits
(PELs) b
httos://www.osha.eov/dse/annotated
-Dels/
Provides regulatory limits on the amount or
concentration of a substance in the air to protect
workers against the health effects of exposure
to hazardous substances. They may also contain
a skin designation. PELs are enforceable.
OSHA PELs are based on an 8-hour time
weighted average (TWA) exposure.
California Division of
Occupational Safety and Health
(CalOSHA) Permissible
Exposure Limits (PELs) for
Chemical Contaminants b
htto ://www. dir. ca. sov/title8/ac 1 ,odf
Provides an extensive list of PELs that are
enforced in workplaces under the jurisdiction
of CalOSHA. Although not enforceable outside
of CalOSHA's jurisdiction, the PELs can
provide information on acceptable levels of
chemicals in the workplace. CalOSHA PELs
are based on an 8-hour TWA exposure.
National Institute for
Occupational Safety and Health
(NIOSH) Recommended
Exposure Limits (RELs)b
httos://www.osha.eov/dse/annotated
-Dels/
littDs://www.cdc. sov/niosh/nr)g/nr)s
svn-a.html
RELs are authoritative Federal agency
recommendations established to limit exposure
to hazardous substances in workplace air to
protect worker health. NIOSH RELs are based
on a 10-hour TWA exposure.
American Conference of
Governmental Industrial
Hygienists (ACGIH®)
Threshold Limit Values
(TLVs®) b
htft>s://www.osha.eov/dse/annotated
-Dels/
TLVs® are health-based values. TLVs®
represent airborne concentrations of chemicals
under which it is believed that nearly all
workers may be repeatedly exposed, day after
day, over a working lifetime, without adverse
effects.
a An RfD is an estimate (with uncertainty spanning an order of magnitude perhaps) of a daily oral exposure to the human
population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a
lifetime, while RfCs similarly represent an estimate of a daily inhalation exposure. An OSF is an upper-bound estimate,
approximating a 95% confidence limit, of the increased cancer risk from a lifetime oral exposure to an agent. This estimate,
usually expressed in terms of the proportion (of a population) affected per mg/kg-day, is generally reserved for use in the
low-dose region of the dose-response relationship (i.e., for exposures corresponding to risks less than 1 in 100). IURs are
similarly an estimate of the increased cancer risk from a lifetime inhalation exposure. OSFs and IURs can be multiplied by
estimated lifetime exposures to estimate the lifetime cancer risk.
b While not directly applicable to all populations that may be exposed to tire crumb rubber, occupational limits developed by
OSHA, CalOSHA, NIOSH, and ACGIH® were also reviewed for tire crumb rubber constituents. Typically, these values
represent recommended levels of chemicals in workplace air that should not be exceeded over an 8- or 10-hour workday.
270
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5.3 Results
A database (Excel spreadsheet) was developed that cross-references chemicals in the tire crumb list of
potential constituents with toxicity data from the sources described above. The database is available
online through the U.S. EPA's study website (see http://www.epa.gov/tirecrumb), and will be useful for
informing future screening-level health risk assessments and for identifying data gaps. This information
is also available in Appendix U. Table 5-2 provides a summary of the number and percent of LRGA
chemical constituents with toxicity data in the various information sources used to gather toxicity
reference information.
Table 5-2. Summary of LRGA Chemical Constituents" with Available Toxicity Data
Sou rccsb
Number of Chemicals with
Available Datac
Percent of Chemicals with
Available Data
IRIS
101
28%
PPRTV
51
14%
HEAST
75
21%
ATSDR
58
16%
CICAD
24
7%
IARC
95
27%
CalEPA
776
22%
OSHA
81
23%
CalOSHA
89
25%
NIOSH
84
24%
ACGIH®
83
23%
a Total number of chemicals evaluated was 355; data were available from at least one source for
167 chemicals (47%). LRGA = Literature Review/Gaps Analysis
b IRIS = EPA Integrated Risk Information System; PPRTV = EPA Provisional Peer-reviewed Toxicity Value;
HEAST = EPA Health Effects Assessment Summary Table; ATSDR = Agency for Toxic Substances and Disease Registry;
CICAD = WHO Concise International Chemical Assessment Documents; IARC = International Agency for Research on
Cancer; CalEPA = California Environmental Protection Agency; OSHA = Occupational Health and Safety Administration;
CalOSHA = California Division of Occupational Safety and Health; NIOSH = National Institute for Occupational Safety and
Health; ACGIH® = American Conference of Governmental Industrial Hygienists;
0 Some chemicals have data from more than one source.
The larger list of over 350 chemicals was narrowed down to its subset of chemicals that are also
included on the targeted analyte list (Tables 3-1 thru 3-4). Of the 95 identified,7 toxicity reference
information was available for 78 (82%) of these. It is important to recognize that some of these target
analytes were not found, or were not consistently found, in tire crumb rubber in this study. Table 5-3
provides a summary of the number and percent of these target analyte chemical constituents with
toxicity data in the various information sources used to gather toxicity reference information.
7From Table 3-1, mercury was included. Benzothiazole appears on both Table 3-2 and Table 3-3 but was only counted once.
DBA and ICDP from Table 3-3 were counted independently. The following VOCs from Table 3-2 were not included:
SumBTEX (sum of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene); trans-2-butene; cis-2-butene; 1,1-
dichloroethene; 1,1-dichloroethane; m-dichlorobenzene; and o-dichlorobenzene.
271
-------
Table 5-3. Summary ofr
arget Chemical Constituents with Available Toxicity Data3
Sou rccsb
Nu mber of Chemicals with
Available Data'
Percent of Chemicals with
Available Data
IRIS
59
62%
PPRTV
25
26%
HEAST
40
42%
ATSDR
41
43%
CICAD
12
13%
IARC
49
52%
CalEPA
40
42%
OSHA
44
46%
CalOSHA
48
51%
NIOSH
42
44%
ACGIH®
46
48%
a Total number of chemicals evaluated was 95; data were available from at least one source for
78 chemicals (82%).
b IRIS = EPA Integrated Risk Information System; PPRTV = EPA Provisional Peer-reviewed Toxicity Value;
HEAST = EPA Health Effects Assessment Summary Table; ATSDR = Agency for Toxic Substances and Disease Registry;
CICAD = WHO Concise International Chemical Assessment Documents; IARC = International Agency for Research on
Cancer; CalEPA = California Environmental Protection Agency; OSHA = Occupational Health and Safety Administration;
CalOSHA = California Division of Occupational Safety and Health; NIOSH = National Institute for Occupational Safety and
Health; ACGIH® = American Conference of Governmental Industrial Hygienists
0 Some chemicals have data from more than one source.
Table 5-4 provides toxicity data for a selection of metals and Table 5-5 provides toxicity data for a
selection of VOCs and SVOCs from the LRGA list of potential constituents. The chemicals included in
Tables 5-4 and 5-5 were selected from the larger list of over 350 chemicals for highlighting based on
their reported potential association with tire crumb rubber in this study or other studies and in part
because of their potential interest as well-known chemicals.
272
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Table 5-4. Chemical-specific Toxicity Data for Select Metals3
Note: Acronyms and units are defined in the footnote for each information source
Chemical
IRISb
PPRTV'
HEAST1'
ATSDR'
CICAD1
IARCR
CalEPA"
OS H A1
CalOSHA'
NIOSH"
ACGIHX1
Arsenic
RfD=3e-4
OSF=1.5
Class A
Dr. Water
UR=5e-5
Inhal.
UR=4.3e-3
N/A
Subchronic
RfD=3e-4
Oral Acute
MRL=0.005
Oral Interm.
MRL=3e-4
N/A
Group 1
NSRL= 0.06
(inhal.)
NSRL= 10 except
(inhal.)
Oral Chronic
REL=0.0035
Inhal. Acute
REL=0.2
Inhal. Chronic
REL=0.015
OSF=1.5
Inhal. SF=12
Inhal. UR=3.3e-3
PEL=0.5
8-hour TWA
PEL=0.2
Ceiling
=0.002
N/A
Cadmium
RfD=5e-4
(water)
RfD=le-3
(food)
Class B1
Inhal.
UR=1.8e-03
N/A
N/A
Oral Interm.
MRL=0.0005
Oral Chronic
MRL=0.0001
Inhal. Acute
MRL=0.00003
N/A
Group 1
NSRL= 0.05
(inhal.)
MADL= 4.1 (oral)
Oral Chronic
REL=0.5
Inhal. Chronic
REL=0.02
OSF=15
Inhal. UR=4.2e-3
8-hour TWA
PEL=0.1
(fume)
8-hour TWA
PEL=0.2
(dust)
Ceiling=0.3
(fume)
Ceiling=0.6
(dust)
8-hour TWA
PEL=0.005
N/A
8-hour TWA
TLV=0.01
(total)
8-hour TWA
TLV=0.002
(resp.)
273
-------
Table 5-4 Continued
Chemical
IRIS"
PPRTV'
HEAST'1
ATSDR'
CICAD1
IARCS
CalEPA"
OSHA'
CalOSHAi
NIOSH1'
ACGIH(k)1
Chromium
RfD=1.5
N/A
Subchronic
Oral Interm.
Tolerable
Group 3
NSRL=0.001
PEL=0.5(CrIII
8-hour TWA
10-hr TWA
8-hour TWA
(CrIII)
RfD=1.0
MRL=0.005
Intake= 9e-4
(CrVI inhal.)
cmpds)
PEL=0.5 (CrIII)
REL=0.5
TLV=0.5
RfD=3e-3
(CrIII)
(CrVI)
(CrVI non-
MADL= 8.2 (oral)
PEL=1 (metal,
8-hour TWA
(CrIII)
(CrVI)
RfC=8e-6
(CrVI
mists)
RfC=le-4
(CrVI
partic.)
Class D
(CrIII)
Class A
(CrVI-
inhal)
Class D
(CrVI-oral)
Inhal. UR=
1,2e-2
(CrVI)
Subchronic
RfD=2e-2
(CrVI)
Inhal. SF=
40 (CrVI)
Oral Chronic
MRL= 0.0009
(CrVI)
Inhal. Interm.
MRL=le-4
(CrIII sol.
partic.)
Inhal. Interm.
MRL=0.005
(CrIII insol.
partic.)
Inhal. Interm.
MRL=5E-6
(CrVI mists)
Inhal. Interm.
MRL=3e-4
canc.)
Oral Chronic
REL=20 (CrVI)
Inhal. Chronic
REL=0.2 (CrVI)
OSF=0.42 (CrVI)
Inhal. SF=510
(CrVI)
Inhal. UR=0.15
(CrVI)
insol salts)
PEL=0.005
(CrVI)
Ceiling= 0.1
(CrVI)
8-hour TWA
TLV=0.05
(CrVI sol.)
8-hour TWA
TLV= 0.01
(CrVI insol.)
(CrVI partic.)
Inhal. Chronic
MRL=5e-6
(CrVI mists)
Cobalt
N/A
Chronic
RfD=3.0e-4
Chronic
RfC=6.0e-6
Subchronic
RfD=3.0e-3
Subchronic
RfC=2.0e-5
Inhal.
UR=9.0
N/A
Oral Interm.
MRL=0.01
Inhal. Chronic
MRL= 0.0001
Tolerable
Conc=1.0e-1
Group 2B
N/A
PEL=0.1
8-hour TWA
PEL=0.02
10-hr TWA
REL=0.05
8-hour TWA
TLV=0.02
Lead
Class B2
N/A
N/A
N/A
N/A
Group 2B
NSRL= 15 (oral)
MADL= 0.5 (oral)
OSF=8.50e-3
Inhal. SF=4.20e-2
Inhal. UR=1.20e-5
N/A
8-hour TWA
PEL=0.05
10-hr TWA
REL=0.05
8-hour TWA
TLV=0.02
274
-------
Table 5-4 Continued
Chemical
IRIS"
PPRTV1
HEAST'1
ATSDR'
CICAD1
IARCS
CalEPA"
OSHA1
CalOSHA'
NIOSH1'
ACGIH(k)1
Zinc
RfD=3.0e-l
Class D
N/A
Subchronic
RfD=3.0e-l
Oral Interm.
MRL=0.3
Oral Chronic
MRL=0.3
N/A
N/A
N/A
N/A
N/A
N/A
N/A
11 See online spreadsheet (https://www.epa.gov/chemical-research/recvcled-tire-crumb-non-targeted-microbial-anaIvsis-results-and-constituent-list') or Appendix W for
additional chemicals. N/A = no information was provided.
b IRIS = EPA Integrated Risk Information System; RfD = Reference dose (mg/kg-d); OSF = Oral slope factor (mg/kg-d)"1; RfC = Reference concentration (mg/m3); Cancer
classes: Class A=human carcinogen, Class Bl=probable human carcinogen - based on limited evidence of carcinogenicity in humans, Class B2=probable human carcinogen -
based on sufficient evidence of carcinogenicity in animals, Class C=possible human carcinogen; Class D=not classifiable as to human carcinogenicity, Class E=evidence of
non-carcinogenicity in humans; Dr. Water UR=Drinking water unit risk (ng/1)"1; Inhal. UR=Inhalation unit risk (ng/m3)1.
0 PPRTV = EPA Provisional Peer-reviewed Toxicity Value; Chronic RfD = Chronic reference dose (mg/kg-d); Chronic RfC = Chronic reference concentration (mg/m3);
Subchronic RfD = Subchronic reference dose (mg/m3); Subchronic RfC = Subchronic reference concentration (mg/m3); Inhal. UR = Inhalation unit risk (mg/m31).
dHEAST = EPA Health Effects Assessment Summary Table; Chronic RfD = Chronic reference dose (mg/kg-d); Subchronic RfD = Subchronic reference dose (mg/m3);
Subchronic RfC = Subchronic reference concentration (mg/m3); Inhal. SF = Inhalation slope factor (mg/kg-day1.
e ATSDR = Agency for Toxic Substances and Disease Registry; MRL = Minimum Risk Level - Acute, Interm. = Intermediate, or Chronic; Oral in mg/kg-day, Inhalation in
mg/m3 unless otherwise stated).
f CICAD = WHO Concise International Chemical Assessment Documents; Tolerable Intake (mg/kg-d unless otherwise stated); Tolerable Cone. = Tolerable Concentration
(jrg/m3); Est. CP = Estimated carcinogenic potency (mg/m3), which is the concentration associated with a 1% increase in mortality due to leukemia); Berk Ov Cancer (mice) = Benchmark
value for ovarian cancer in mice.
g IARC = International Agency for Research on Cancer; IARC cancer classifications: Group l=carcinogenic to humans; Group 2A=probably carcinogenic to humans; Group
2B=possibly carcinogenic to humans; Group 3= not classifiable as to its carcinogenicity in humans; Group 4=probably not carcinogenic to humans.
h CalEPA = California Environmental Protection Agency; NSRL = No Significant Risk Level (|ig/day), Oral or Inhal. = Inhalation; MADL = Maximum Allowable Dose
Level (ng/day), Oral or Inhal. = Inhalation; Oral Chronic REL = Chronic Oral recommended exposure limit (|ig/kg-d): Inhal. Acute REL = inhalation acute recommended
exposure limit (|ig/m3); Inhal. 8-hr REL = inhalation 8-hr recommended exposure limit (|ig/m3): Inhal. Chronic REL = inhalation chronic recommended exposure limit
(Hg/m3); OSF=Oral slope factor (mg/kg-d)1; Inhal. SF=Inhalation slope factor (mg/kg-d)1; Inhal. UR=Inhalation unit risk (ng/m3)1.
1OSHA = Occupational Health and Safety Administration; PEL=permissible exposure limit (in mg/m3 unless otherwise stated); 8-hr TWA = 8-hour time weighted average
(in mg/m3 unless otherwise stated); Ceiling = permissible exposure limit ceiling (mg/m3 unless otherwise stated).
J CalOSHA = California Division of Occupational Safety and Health; 8-hr TWA PEL = 8-hour time weighted average permissible exposure limit (in mg/m3 unless otherwise
stated); STEL = Short term exposure limit (in mg/m3 unless otherwise stated); Ceiling = permissible exposure limit ceiling (mg/m3 unless otherwise stated).
k NIOSH = National Institute for Occupational Safety and Health; 10-hr TWA REL=10-hour time weighted average recommended exposure limit (in mg/m3 unless otherwise
stated); STEL=Short term exposure limit (in mg/m3 unless otherwise stated); Ceiling = recommended exposure limit ceiling (in mg/m3 unless otherwise stated).
1ACGIH® = American Conference of Governmental Industrial Hygienists; 8-hr TWA TLV = 8-hour time weighted average threshold limit value (in mg/m3 unless otherwise
stated); STEL TLV = Short term exposure limit threshold limit value (in ppm); Ceiling = threshold limit value ceiling (in ppm).
275
-------
Table 5-5. Chemical-specific Toxicity Data for Select VOCs and SVOCs3
Note: Acronyms and units are defined in the footnote for each information source
Chemical
IRISb
PPRTV'
HEAST1'
ATSDR'
CICAD1
IARCR
CalEPA"
OS H A1
CalOSHA'
NIOSH"
ACGIHX1
Aniline
RfC=1.0e-3
OSF=5.7e-3
Class B2
Dr. Water
UR=1.6e-7
Chronic
RfD=7.0e-3
Subchronic
RfC=1.0e-2
N/A
N/A
Group 3
NSRL=100
OSF=5.70E-3
Inhal. UR=1.60e-6
PEL=19
8-hour TWA
PEL=7.6
N/A
8-hr TWA
TLV=2
Benzene
RfD=4.0e-3
RfC=3.0e-2
Class A
OSF=1.5e-
02 to 5.5e-
02
Dr. Water
UR=4.4e-07
to 1.6e-06
Inhal. UR=
2.2e-06 to
7.8e-05
Subchronic
RfD=1.0e-2
Subchronic
RfC=8.0e-2
Inhal.
SF=2.9e-2
Oral Chronic
MRL=5e-3
Inhal. Acute
MRL=9e-3
Inhal. Interm.
MRL=6e-3
Inhal. Chronic
MRL=0.003
N/A
Group 1
NSRL=6.4 (oral)
NSRL=13
(inhalation)
MADL=24 (oral)
MADL=49
(inhalation)
Inhal. Acute
REL=27
Inhal. 8-hr REL=3
Inhal. Chronic
REL=3
OSF=1.00e-l
Inhal. UR=2.90e-5
8-hr TWA=10
Ceiling=25
PPm
8-hr TWA
PEL=1ppm
STEL=5 ppm
10-hr TWA
REL=0.1
STEL=1ppm
8-hr TWA
TLV=0.5
STELTLV=
2.5
Benzo(a)pyrene
Class B2
Oral OSF=
7.3
Dr. Water
UR=2.1e-4
N/A
N/A
N/A
N/A
Group 1
NSRL=0.06
OSF=12
Inhal. SF=3.6
Inhal. UR= 1.1 Oe-
3
PEL=0.2 (coal
tar pitch
volatiles)
8-hr TWA
PEL=0.2 (coal
tar pitch
volatiles)
10-hr TWA
REL=0.1
(cyclohexane
extrac table
fraction)
8-hr TWA
TLV=0.2
(coal tar
pitch
volatiles)
Benzo(ghi)
perylene
Class D
N/A
N/A
N/A
N/A
Group 3
N/A
N/A
N/A
N/A
N/A
Benzothiazole
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2-hydroxybenzo
thiazole
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Bis(2-ethylhexyl)
phthalate
RfD=2.0e-2
Class B2
OSF=1.4e-2
Dr. Water
UR=4.0e-7
N/A
N/A
Oral Interm.
MRL=0.1
Oral Chronic
MRL=0.06
N/A
Group 2B
NSRL=310
MADL=410
(adult oral)
OSF=8.40e-3
Inhal. UR= 2.40e-
6
PEL=5
N/A
10-hr TWA
REL=5
STEL=10
8-hr TWA
TLV=5
276
-------
Table 5-5 Continued
Chemical
IRISb
PPRTV
HEAST'1
ATSDR'
CICAD1
IARO
CalEPA1'
OS H A1
CalOSHAi
NIOSH1'
ACGIHX1
1,3-Butadiene
RfC=2.0e-3
Class A
Inhal. UR=
3.0e-5
N/A
N/A
N/A
Est. CP= 1.7
Berk. Ov.
Cancer
(mice)=0.57
Group 1
Inhal. acute
REL=660
Inhal. 8-hr REL=9
Inhal. Chronic
REL=2
OSF=6.00e-l
Inhal. SF=
6.00e-l
Inhal. UR=1.70e-
4
PEL=lppm
8-hr TWA
PEL=1ppm
8-hr TWA
PEL=2.2
STEL=5 ppm
STEL=11
N/A
8-hr TWA
TLV=2 ppm
Cyclohexylamine
RfD=2.0e-l
N/A
Subchronic
RfD=3.0e-l
N/A
N/A
N/A
N/A
N/A
8-hr TWA
PEL=10 ppm
8-hr TWA
PEL=40
10-hr TWA
REL=10 ppm
10-hr TWA
REL=40
N/A
Di-
cyclohexylamine
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Cyclohexanamine,
N-cyclohexyl-N-
methyl-
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Dibutyl phthalate
RfD=1.0e-l
Class D
N/A
Subchronic
RfD=l
Oral Acute
MRL=0.5
N/A
N/A
MADL=8.7
PEL=5
8-hr TWA
PEL=5
10-hr TWA
REL=5
8-hr TWA
TLV=5
Ethyl benzene
RfD=1.0e-l
RfC=l
Class D
Subchronic
RfD=
5.0e-2
Subchronic
RfC=9
Oral Interm.
MRL=0.4
Inhal. Acute
MRL=5ppm
Inhal. Interm.
MRL=2ppm
Inhal. Chronic
MRL=0.06
N/A
Group 2B
NSRL= 41 (oral)
NSRL=54
(inhalation)
Inhal. Chronic
REL=2000
OSF=l,10e-2
Inhal. SF=
8.70e-3
Inhal. UR=2.50e-
6
PEL=100 ppm
PEL=435
8-hr TWA
PEL=5ppm
8-hr TWA
PEL=22
STEL=30 ppm
STEL=130
10-hr TWA
REL=100
ppm
10-hr TWA
REL=435
STEL
REL=125
ppm
STEL
REL=545
8-hr TWA
TLV=20
ppm
Fluoranthene
RfD=4.0e-2
Class D
Subchronic
RfD=1.0e-l
Subchronic
RfD=4.0e-l
Oral Interm.
MRL=0.4
N/A
Group 3
N/A
N/A
N/A
N/A
N/A
111
-------
Table 5-5 Continued
Chemical
IRISb
PPRTV
HEAST'1
ATSDR'
CICAD1
IARO
CalEPA1'
OS H A1
CalOSHAi
NIOSH1'
ACGIHX1
Formaldehyde
RfD=2.0e-l
Class B1
N/A
Subchronic
RfD=2.0e-l
Oral Interm.
MRL=0.3
Oral Chronic
MRL=0.2
Inhal. Acute
MRL=0.04
Inhal. Interm.
MRL=0.03
Inhal. Chronic
MRL=0.008
Tolerable
Intake=2600
Hg/L
Group 1
NSRL=40
Inhal. Acute
REL=55
Inhal. 8-hr REL=9
Inhal. Chronic
REL=9
OSF=2.10e-2
Inhal. UR=6.00e-6
N/A
8-hr TWA
PEL=0.75
STEL=0.2
10-hr TWA
REL=0.016
Ceiling
=0.1 ppm
Ceiling=0.3
Hexadecane
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2-Mercaptobenzo
thiazole
N/A
N/A
N/A
N/A
N/A
Group 2A
N/A
N/A
N/A
N/A
N/A
Methyl isobutyl
ketone
RfC=3
N/A
Subchronic
RfD=8.0e-l
N/A
N/A
Group 2B
N/A
PEL=100 ppm
PEL=410
8-hr TWA
PEL=50ppm
8-hr TWA
PEL=205
STEL=75 ppm
STEL=300
10-hr TWA
REL=50 ppm
10-hr TWA
REL=205
STEL=75
ppm
STEL=300
8-hr TWA
TLV=20
STEL
TLV=75
4-tert-octylphenol
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Phenanthrene
Class D
N/A
N/A
N/A
N/A
Group 3
N/A
PEL=0.2 (coal
tar pitch
volatiles)
8-hr TWA
PEL=0.2 (coal
tar pitch
volatiles)
10-hr TWA
REL=0.1
(cyclohexane
extrac table
fraction)
8-hr TWA
TLV=0.2
(coal tar
pitch
volatiles)
Pyrene
RfD=3.0e-2
Class D
Subchronic
RfD=3.0e-l
Subchronic
RfD=3.0e-l
N/A
N/A
Group 3
N/A
PEL=0.2 (coal
tar pitch
volatiles)
8-hr TWA
PEL=0.2 (coal
tar pitch
volatiles)
10-hr TWA
REL=0.1
(cyclohexane
extrac table
fraction)
8-hr TWA
TLV=0.2
(coal tar
pitch
volatiles)
278
-------
Table 5-5 Continued
Chemical
IRISb
PPRTV
HEAST'1
ATSDR'
CICAD1
IARO
CalEPA1'
OS HA1
CalOSHA'
NIOSH1'
ACGIHX1
Styrene
RfD=2.0e-l
RfC=l
N/A
Subchronic
RfC=3
Inhal. Acute
MRL=5
Inhal. Chronic
MRL=0.2
N/A
Group 2B
Inhal. Acute
REL=21000
Inhal. Chronic
REL=900
8-hr
TWA=100
Ceiling=200
ppm
8-hr TWA
PEL=50ppm
8-hr TWA
PEL=215
STEL=100 ppm
STEL=425
Ceiling=500
ppm
10-hr TWA
REL=50 ppm
10-hr TWA
REL=215
STEL=100
ppm
STEL=425
8-hr TWA
TLV=20
STEL
TLV=40
Toluene
RfD=8.0e-2
Class D
Subchronic
RfD=
8.0e-l
Subchronic
RfC=5
Subchronic
RfC=2
Oral Interm.
MRL=0.2
Inhal. Acute
MRL= 0.2
Inhal Chronic
MRL=1
N/A
Group 3
MADL=7000
Inhal. Acute
REL=37000
Inhal. Chronic
REL=900
8-hr
TWA=200
Ceiling=300
ppm
8-hr TWA
PEL=10 ppm
8-hr TWA
PEL=37
STEL=150 ppm
STEL=560
Ceiling=500
ppm
10-hr TWA
REL=100
ppm
10-hr TWA
REL=375
STEL=150
ppm
STEL=560
8-hr TWA
TLV=20
o-Xylene
N/A
N/A
Chronic
RfD=2
N/A
N/A
Inhal. Acute
REL=22000
Inhal. Chronic
REL=700
PEL=100ppm
PEL=435
N/A
10-hr TWA
REL=100
ppm
10-hr TWA
REL=435
STEL=150
ppm
STEL=655
8-hr TWA
TLV=100
STEL
TLV=150
Xylenes (m-, p-, o-)
RfD=2.0e-l
RfC=1.0e-l
Subchronic
RfD=
4.0e-l
Subchronic
RfC=4.0e-l
N/A
Oral Interm.
MRL=0.4
Oral Chronic
MRL=0.2
Inhal. Acute
MRL=2
Inhal. Interm.
=0.6
Inhal. Chronic
MRL=0.05
N/A
Group 3
Inhal. Acute
REL=22000
Inhal. Chronic
REL=700
PEL=100ppm
PEL=435
8-hr TWA
PEL=100 ppm
8-hr TWA
PEL=435
STEL=150 ppm
STEL=655
Ceiling=300
ppm
N/A
8-hr TWA
TLV=100
STEL
TLV=150
11 See online spreadsheet (https://www.epa.gov/chemical-research/recvcled-tire-crumb-non-targeted-microbial-anaIvsis-results-and-constituent-list') or Appendix W for
additional chemicals. VOCs = volatile organic compounds; SVOCs = semivolatile organic compounds; N/A = no information was provided.
279
-------
b IRIS = EPA Integrated Risk Information System; RfD = Reference dose (mg/kg-d); OSF = Oral slope factor (mg/kg-d)"1; RfC = Reference concentration (mg/m3); Cancer
classes: Class A=human carcinogen, Class Bl=probable human carcinogen - based on limited evidence of carcinogenicity in humans, Class B2=probable human carcinogen -
based on sufficient evidence of carcinogenicity in animals, Class C=possible human carcinogen; Class D=not classifiable as to human carcinogenicity, Class E=evidence of
non-carcinogenicity in humans; Dr. Water UR=Drinking water unit risk (ng/1)"1; Inhal. UR=Inhalation unit risk (ng/m3)1.
0 PPRTV = EPA Provisional Peer-reviewed Toxicity Value; Chronic RfD = Chronic reference dose (mg/kg-d); Chronic RfC = Chronic reference concentration (mg/m3);
Subchronic RfD = Subchronic reference dose (mg/m3); Subchronic RfC = Subchronic reference concentration (mg/m3); Inhal. UR = Inhalation unit risk (mg/m31).
d HEAST = EPA Health Effects Assessment Summary Table; Chronic RfD = Chronic reference dose (mg/kg-d); Subchronic RfD = Subchronic reference dose (mg/m3);
Subchronic RfC = Subchronic reference concentration (mg/m3); Inhal. SF = Inhalation slope factor (mg/kg-day1.
e ATSDR = Agency for Toxic Substances and Disease Registry; MRL = Minimum Risk Level - Acute, Interm. = Intermediate, or Chronic; Oral in mg/kg-day, Inhalation in
mg/m3 unless otherwise stated).
fCICAD = WHO Concise International Chemical Assessment Documents; Tolerable Intake (mg/kg-d unless otherwise stated); Tolerable Cone. = Tolerable Concentration
(|ig/m3); Est. CP = Estimated carcinogenic potency (mg/m3), which is the concentration associated with a 1% increase in mortality due to leukemia); Berk Ov Cancer (mice) = Benchmark
value for ovarian cancer in mice.
g IARC = International Agency for Research on Cancer; IARC cancer classifications: Group l=carcinogenic to humans; Group 2A=probably carcinogenic to humans; Group
2B=possibly carcinogenic to humans; Group 3= not classifiable as to its carcinogenicity in humans; Group 4=probably not carcinogenic to humans.
h CalEPA = California Environmental Protection Agency; NSRL = No Significant Risk Level (|ig/day). Oral or Inhal.= Inhalation; MADL = Maximum Allowable Dose
Level (ng/day), Oral or Inhal. = Inhalation; Oral Chronic REL = Chronic Oral recommended exposure limit (|ig/kg-d): Inhal. Acute REL = inhalation acute recommended
exposure limit (|ig/m3): Inhal. 8-hr REL = inhalation 8-hr recommended exposure limit (|ig/m3); Inhal. Chronic REL = inhalation chronic recommended exposure limit
(|ig/m3): OSF=Oral slope factor (mg/kg-d)1; Inhal. SF=Inhalation slope factor (mg/kg-d)1; Inhal. UR=Inhalation unit risk (ng/m3)1.
1OSHA = Occupational Health and Safety Administration; PEL=permissible exposure limit (in mg/m3 unless otherwise stated); 8-hr TWA = 8-hour time weighted average
(in mg/m3 unless otherwise stated); Ceiling = permissible exposure limit ceiling (mg/m3 unless otherwise stated).
J CalOSHA = California Division of Occupational Safety and Health; 8-hr TWA PEL = 8-hour time weighted average permissible exposure limit (in mg/m3 unless otherwise
stated); STEL = Short term exposure limit (in mg/m3 unless otherwise stated); Ceiling = permissible exposure limit ceiling (mg/m3 unless otherwise stated).
k NIOSH = National Institute for Occupational Safety and Health; 10-hr TWA REL=10-hour time weighted average recommended exposure limit (in mg/m3 unless otherwise
stated); STEL=Short term exposure limit (in mg/m3 unless otherwise stated); Ceiling = recommended exposure limit ceiling (in mg/m3 unless otherwise stated).
1ACGIH® = American Conference of Governmental Industrial Hygienists; 8-hr TWA TLV = 8-hour time weighted average threshold limit value (in mg/m3 unless otherwise
stated); STEL TLV = Short term exposure limit threshold limit value (in ppm); Ceiling = threshold limit value ceiling (in ppm).
280
-------
5.4 Conclusions
Of the 355 constituents examined, extant toxicity reference information was limited, with information
available for only 167 (47%) of the chemicals. The greatest sources of information were IRIS values
(available for 28% of the constituents), IARC cancer classifications (27% of the constituents), CalOSHA
8-hr time-weighted average (TWA) PEL values (available for 25% of the constituents), and NIOSH 10-
hr TWA REL values (available for 24% of the constituents).
However, when narrowing to a subset of 95 constituents on the target analyte list, extant toxicity
information was available for 78 of them (82%). Similarly, for the 31 constituents of interest in Tables
5-4 and 5-5, extant toxicity information was available for 25 of them (81%). The greatest sources of
information for the chemicals of interest were IRIS values (available for 71% of Table 5-4 and 5-5
constituents), IARC cancer classifications (available for 68% of Table 5-4 and 5-5 constituents),
CalOSHA 8-hr TWA PEL values (available for 65% of Table 5-4 and 5-5 constituents), and ACGIH
values (61%) of Table 5-4 and 5-5 constituents). No toxicity reference information was found in the
information sources examined for six of the Table 5-5 constituents: benzothiazole, 2-
hydroxybenzothiazole, N-cyclohexyl-cyclohexanamine, N-cyclohexyl-N-methylcyclohexanamine,
hexadecane, or 4-tert-octylphenol. In addition to the target chemicals measured in this portion of the
study, the presence of many other organic chemicals was found through non-targeted assessment.
Further work would be needed to positively identify chemicals and their amounts, and to cross-reference
with the availability of toxicity information for these chemicals.
While toxicity reference information was available for a higher proportion of the target analyte
constituents and the constituents of interest than for the chemicals in the full list of potential constituents
identified from the LRGA, data gaps remain for both sets of constituents. Potential toxicity-related
information beyond the sources reviewed here may be available in the literature for some of these
chemicals, but additional, significant effort would be required to identify and review such information
for use in future human health risk assessments of tire crumb rubber.
The U.S. Department of Health and Human Services' National Toxicology Program has been exploring
the feasibility of in vitro studies to assess bioaccessibility and cytotoxicity of the crumb rubber material
(Gwinn et al., 2018), and in vivo studies to examine the short-term toxicity effects from various routes
of exposure (Richey et al., 2018; Roberts et al., 2018). These 'bulk toxicity' approaches may provide
avenues to develop more comprehensive data that would be needed for conducting human health risk
assessments that address the cumulative risk of multiple chemical exposures. Overall, the large number
of chemical constituents identified in recycled tire crumb rubber combined with the varying degree of
availability of toxicity reference information for many of these chemicals presents challenges for
understanding the potential human health risks from exposure to these chemicals.
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282
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7.0 Appendices
The following Appendices can be found in Volume 2 of this report:
A Industry Overview
B Stakeholder Outreach
C State-of-Science Literature Review/Gaps Analysis
D Standard Operating Procedure (SOP) Lists for Tire Crumb Rubber Characterization Research
E Quality Assurance and Quality Control
F Synthetic Turf Field Facility Owner/Manager Questionnaire
G Shapiro-Wilk Test Results for Selected Tire Crumb Rubber Characterization Measurement
Distributions
H Tire Crumb Rubber Particle Size Characterization Results and Sample Photos
I Tire Crumb Rubber Measurement Results - Summary Statistics
J Dynamic Chamber Emissions Measurements Time Series Test Results
K Tire Crumb Rubber Measurement Results - Differences Between Recycling Plants and Synthetic
Turf Fields
L Tire Crumb Rubber Measurement Results - Replicate and Duplicate Analysis Precision and
Homogeneity
M Tire Crumb Rubber Measurement Results - Within and Between Recycling Plant Variability
N Tire Crumb Rubber Measurement Results - Within and Between Synthetic Turf Field Variability
O Tire Crumb Rubber Measurement Results - Differences Between Outdoor and Indoor Synthetic Turf Fields
P Tire Crumb Rubber Measurement Results - Differences Among Synthetic Turf Fields with Different
Installation Ages
Q Tire Crumb Rubber Measurement Results - Differences Among Synthetic Turf Fields in Different
U.S. Census Regions
R Non-Targeted Screening Analysis Results for SVOCs and VOCs
S Targeted Microbiological Analysis Results for Tire Crumb Rubber Infill Samples Collected at
Synthetic Turf Fields
T Dynamic Chamber Silicone Wristband Experiments
U Toxicity Reference Information
V Summary of External Peer Review Comments
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