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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
Disclaimers
This document is designed to provide supporting information regarding the regulatory determination
for hexachlorobutadiene as part of the Contaminant Candidate List (CCL) evaluation process. This
document is not a regulation, and it does not substitute for the Safe Drinking Water Act (SDWA) or the
Environmental Protection Agency's (EPA's) regulations. Thus, it cannot impose legally-binding
requirements on EPA, States, or the regulated community, and may not apply to a particular situation
based upon the circumstances. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
Acknowledgments
This document was prepared in support of the EPA'S Office of Ground Water and Drinking Water
regulatory determination for hexachlorobutadiene as part of the Contaminant Candidate List (CCL)
evaluation process. Dan Olson and Karen Wirth served as EPA's team leaders for the CCL regulatory
determination process and James Taft as Standards and Risk Management Division Chief. Tara Cameron
and Karen Wirth served as Work Assignment Managers. The CCL Work Group provided technical
guidance throughout. In particular, Karen Wirth, Dan Olson, and Joyce Donohue provided scientific and
editorial guidance. External expert reviewers and many stakeholders provided valuable advice to improve
the CCL Program and this document The Cadmus Group, Inc., served as the primary contractor
providing support for this work. The major contributions of Matt Collins, Emily Brott, and Ashton Koo
are gratefully acknowledged. George Hallberg served as Cadmus'Project Manager.
111
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Preliminary Regulatory Determination Support Document for Hexachlorobiitadiene
November, 2001
USEPA, Office of Water Report EPA 815-R-01-009, November, 2001
CONTAMINANT CANDIDATE LIST
PRELIMINARY REGULATORY DETERMINATION
SUPPORT DOCUMENT FOR HEXACHLOROBUTADIENE
Executive Summary
Hexachlorobutadiene is a 1998 Contaminant Candidate List (CCL) preliminary regulatory
determination priority contaminant Hexachlorobutadiene is one of the contaminants considered by EPA
for a regulatory determination. The available data on occurrence, exposure, and other risk considerations
suggest that regulating hexachlorobutadiene may not present a meaningful opportunity to reduce health
risk. EPA presents preliminary CCL regulatory determinations and further analysis in the Federal
.Register Notice. .',.
To make this preliminary regulatory determination for hexachlorobutadiene, EPA used approaches
guided by the National Drinking Water Advisory Council's (NDWAC) Work Group on CCL and Six-
Year Review. The Safe Drinking Water Act (SDWA) requirements for National Primary Drinking Water
Regulation (NPDWR) promulgation guided protocol development The SDWA Section 1412(b)(l)(A)
specifies that the determination to regulate a contaminant must be based on a rinding that each of the
following criteria are met: (i) "the contaminant may have adverse effects on the health pf persons"; (ii)
"the contaminant is known to occur or there is substantial likelihood that the contaminant will occur in
public water systems with a frequency and at levels of public health concern"; and (Hi) "in the sole
judgement of the Administrator, regulation of such contaminant presents a meaningful opportunity for
health risk reduction for persons served by public water systems." Available data were evaluated to
address each of me three statutory criteria.
Hexachlorobutadiene is a volatile organic compound (VOC) not known to naturally occur. It is
commonly used as a solvent and in the production of rubber compounds (ATSDR, 1995; see Section 2.0).
Hexachlorobutadiene is not specifically manufactured as a commercial product in the United States, but
significant quantities of the chemical are generated here as a waste by-product from the chlorination of
hydrocarbons. It is also imported for use as a chemical intermediate hi some manufacturing processes and
as a component of a number of commercial products. Its use in these products, such as transformer and
hydraulic fluids, gyroscope fluids, heat transfer liquids, solvents, and laboratory reagents, is widespread.
Hexachlorobutadiene was monitored from 1987 to 1999 under the SDWA Unregulated Contaminant
Monitoring (UCM) program. Hexachlorobutadiene is also monitored or regulated by other federal
programs including the Clean Water Act Priority Pollutants list, the Clean Air Act Hazardous Air
Pollutant list, the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA),
the Resource Conservation and Recovery Act (RCRA), and the Toxic Release Inventory (TRT).
Because of concerns about human health risk, EPA issued a drinking water health advisory (HA) for
hexachlorobutadiene hi 1989 at 1 ug/L. Other federal agencies and organizations have issued
recommendations for occupational exposure.
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene November, 2001
The United States Geological Survey's (USGS) National Water Quality Assessment (NAWQA)
program studies to date have reported no detections of hexachlorobutadiene in ambient water. However,
releases of hexachlorobutadiene to the environment reported through the Toxic Release Inventory (TRI),'
and its occurrence in site samples recorded in the Agency for Toxic Substances and Disease Registry's '
(ATSDR) Hazardous Substance Release and Health Effects Database (HazDat) and at CERCLA National
Priorities List (NPL) hazardous waste sites, provides evidence for the widespread use and environmental
release of hexachlorobutadiene.
Hexachlorobutadiene has also been detected in PWS samples collected under SDWA. Occurrence
estimates are low for both rounds of UCM monitoring with less than 0.2% of all samples showing
detections. Significantly, the values for the 99th percentile and median concentrations of all samples are
less than the Minimum Reporting Level. Systems with detections only constitute 0.350% of Round 1
systems and 0.180% for Round 2. Detections greater than the Health Reference Level (HRL) of 0.9 ug/L
are less: 0.114% and 0.018% of Round 1 and Round 2 systems, respectively. National estimates for the
population served by PWSs with detections are also low, especially for detections greater man the HRL.
For both rounds, these estimates are less than 0.5% of the national PWS population.
The available toxicologies! data indicate that HCBD has the potential to cause adverse health effects
inanimals. In particular, me primary target organ for HCBD is the kidney. Data on human health effects,
however, are limited to a few studies of occupational exposure to HCBD. These data, collected from
inhalation exposure, are often confounded by simultaneous exposures to other chemicals in an
occupational setting. Such equivocal data has made it difficult to establish a relationship between HCBD
exposure and toxic/cytogenetic effects in human. Hexachlorobutadiene is classified as apossible human
carcinogen.
Monitoring data indicate that hexachlorobutadiene is infrequently detected in public water supplies.
In addition to the feet that these detections are low, it is important to note that when hexachlorobutadiene
is detected, it very rarely exceeds the HRL or a value of one-half the HRL. For example, under Round 2
monitoring, the 20-State cross-section analysis shows that only 4 out of 22,736 of the reporting PWSs had
detections above the HRL. Therefore regulation of hexachlorobutadiene is unlikely to represent a
meaningful opportunity for health risk reduction.
VI
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
Table of Contents
Disclaimers i
Acknowledgments , iii
Table of Contents — vii
List of Tables .. ix
List of Figures xi
1.0 INTRODUCTION f 1
1.1 Purpose and Scope 1
1.2 Statutory Framework/Background 1
1.3 Statutory History of Hexachlorobutadiene 2
1.4 Regulatory Determination Process 3
1.5 Determination Outcome , 4
2.0 CONTAMINANT DEFINITION 4
2.1 Physical and Chemical Properties 4
2.2 Environmental Fate/Behavior 5
3.0 OCCURRENCE AND EXPOSURE ; 6
3.1 Use and Environmental Release 6
3.1.1 Production and Use 6
3.1.2 Environmental Release 6
3.2 Ambient Occurrence 8
3.2.1 Data Sources and Methods 8
3.2.2 Results 9
3.3 Drinking Water Occurrence 9
3.3.1 Data Sources, Data Quality, and Analytical Approach 9
33.1.1 UCMRounds 1 and2 ...:.... 10
3.3.1.2 Developing a Nationally Representative Perspective 11
3.3.1.2.1 Cross-Section Development 11
3.3.1.2.2 Cross-Section Evaluation 12
3.3.1.3 Data Management and Analysis 14
3.3.1.4 Occurrence Analysis 14
3.3.2 Results 16
3.3.2.1 Occurrence Estimates 16
3.3.2.2 Regional Patterns 19
3.4 Conclusion 23
4.0 HEALTHEFFECTS 23
4.1 Hazard Characterization and Mode of Action Implications 23
4.2 Dose-Response Characterization and Implications in Risk Assessment 24-
vu
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene November, 2001
4.3 Relative Source Contribution 25
4.4 Sensitive Populations \\\\ 26
4.5 Exposure and Risk Information \'\ 26
4.6 Conclusion ' • • • • • ^
5.0 TECHNOLOGY ASSESSMENT 27
5.1 Analytical Methods 27
5.2 Treatment Technology '.'.'.'.'.'.'.'.'.I'.'. 27
6.0 SUMMARY AND CONCLUSIONS-DETERMINATION OUTCOME 28
References
31
Appendix A: Abbreviations and Acronyms 35
Vlll
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
List of Tables
Table 2-1: Physical and chemical properties 5
Table 3-1: Environmental releases (in pounds) for hexachlorobutadiene in the United States, 1988-1998
7
Table 3-2: Cross-section States for Round 1 (24 States) and Round 2 (20 States) 13
Table 3-3: Summary occurrence statistics for hexachlorobutadiene 18
IX
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
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List of Figures
Figure 3-1: Geographic distribution of cross-section States for Round 1 (left) and Round 2 (right) ... 13
Figure 3-2: States with PWSs with detections of hexachlorobutadiene for all States with data in URCIS
(Round 1) and SDWIS/FED (Round 2) 20
Figure 3-3: States with PWSs with detections of hexachlorobutadiene (any PWSs with results greater
than the Minimum Reporting Level [MRL]) for Round 1 (above) and Round 2 (below) cross-section
States 21
Figure 3-4: Cross-section States (Round 1 and Round 2 combined) with PWSs with detections of
hexachlorobutadiene (above) and concentrations greater than the Health Reference Level (below)
22
XI
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
1.0 INTRODUCTION
1.1 Purpose and Scope
This document presents scientific data and summaries of technical information prepared for and used
in the Environmental Protection Agency's (EPA) regulatory determination for hexacMorobutadiene.
Information regarding hexachlorobutadiene's physical and chemical properties, environmental fate,
occurrence and exposure, and health effects is included. Analytical methods and treatment-technologies
are also discussed. Furthermore, the regulatory determination process is described to provide the
rationale for the decision.
1.2 Statutory Framework/Background
The Safe Drinking Water Act (SDWA), as amended in 1996, requires the United States
Environmental Protection Agency (USEPA) to publish a list of contaminants {referred to as the
Contaminant Candidate List, or CCL) to assist in priority-setting efforts. The contaminants included on
the CCL were not subject to any current or proposed National Primary Drinking Water Regulations
(NPDWR), were known or anticipated to occur in public water systems, and were known or suspected to
adversely affect public health. These contaminants therefore may require regulation under SDWA. The
first Drinking Water CCL was published on March 2,1998 (USEPA, 1998a; 63 FR 10273), and a new
CCL must be published every five years thereafter.
The 1998 CCL contains 60 contaminants, including 50 chemicals or chemical groups, and 10
microbiological contaminants or microbial groups. The SDWA also requires me Agency to select 5 or
more contaminants from the current CCL and determine whether or not to regulate these contaminants
with an NPDWR. Regulatory determinations for at least 5 contaminants must be completed 3V4 years
after each new CCL.
Language in SDWA Section 1412(b)(l)(A) specifies that the determination to regulate a contaminant
must be based on a finding that each of the following criteria are met:
Statutory Finding i: .. .the contaminant may have adverse effects on the health of persons;
Statutory Finding ii: the contaminant is known to occur or there is substantial likelihood that
the contaminant will occur in public water Systems with a frequency and at levels of public
health concern; and -
Statutory Finding Hi: in the sole judgement of the Administrator, regulation of such
contaminant presents a meaningful opportunity for health risk reduction for persons served
by public water systems.
The geographic distribution of the contaminant is another factor evaluated to determine whether it
occurs at the national, regional or local level. This consideration is important because the Agency is
charged with developing national regulations and it may not be appropriate to develop NPDWRs for
regional or local contamination problems.
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene November, 2001
EPA must determine if regulating this CCL contaminant will present a meaningful opportunity to
reduce health risk based on contaminant occurrence, exposure, and other risk considerations The Office
of Ground Water and Drinking Water (OGWDW) is charged with gathering and analyzing the
occurrence, exposure, and risk information necessary to support this regulatory decision. The OGWDW
must evaluate when and where this contaminant occurs, and what would be the exposure and risk to
public health. EPA must evaluate the impact of potential regulations as well as determine the appropriate
measure(s) for protecting public health.
For each of the regulatory determinaition contaminants, EPA must first publish in the Federal Register
the draft determinations for public comment. EPA will respond to the public comments received, and will
then finalize regulatory determinations. If the Agency finds that regulations are warranted, the
regulations must then be formally proposed within twenty-four months, and promulgated eighteen months
later. EPA has determined that there is sufficient information to support a regulatory determination for
hexachlorobutadiene.
13 Statutory History of Hexachlorobutadiene
Hexachlorobutadiene has been monitored under the SDWA Unregulated Contaminant Monitoring
(UCM) program since 1987. It was among 14 VOCs included for discretionary monitoring (USEPA,
1987; 52 FR 25690). Monitoring for hexachlorobutadiene under UCM continued throughout the 1990s
but ceased for small public water systems (PWSs) under a direct final rule published January 8 1999
(USEPA, 1999a; 64 FR 1494). Monitoring ended for large PWSs with promulgation of the new
Unregulated Contaminant Monitoring Regulation (UCMR) issued September 17,1999 (USEPA, 1999b-
64 FR 50556) and effective January 1,2001. At the time the UCMR lists were developed, the Agency '
concluded there were adequate monitoring data for a regulatory determination. This obviated the need for
continued monitoring under the new UCMR list
EPA previously recommended guidelines for exposure to hexachlorobutadiene in drinking water
through a health advisory (USEPA, 1989; ATSDR, 1995). As part of the CCL process, health effects data
have been reviewed. These are summarized in Section 4.0 of this document
Hexachlorobutadiene is regulated or monitored by other federal programs as well. It is included on
the Clean Water Act Priority Pollutants list for which EPA establishes ambient water quality criteria It is
also.listed as a Hazardous Air Pollutant under the Clean Air Act and subject to Best Available Control
Technology limits. Both the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA or "Superfund") and the Resource Conservation and Recovery Act (RCRA) include it as a
hazardous substance and a hazardous constituent, respectively. CERCLA's listing requires reporting of
releases over a certain "reportable quantity" which, for hexachlorobutadiene, is one pound (ATSDR,
1995). Also, hexachlorobutadiene is a Toxic Release Inventory (TRI) chemical. The TRI was established
by the Emergency Planning and Community Right-to-Know Act (EPCRA). EPCRA requires certain
industrial sectors to publically report the environmental release or transfer of chemicals included in this
inventory (USEPA, 2000d).
Finally, the National Institute for Occupational Safety and Health (NIOSH) recommends an
occupational exposure limit of 0.02 parts hexachlorobutadiene per million in air (0.02 ppm) for an 8-hour
workday over a 40-hour workweek. The American Conference of Governmental Industrial Hygienists
(ACGIH) makes the same workplace recommendations (ATSDR, 1995).
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
1.4 Regulatory Determination Process
In developing a process for the regulatory determinations, EPA sought input from experts and
stakeholders. EPA asked the National Research Council (NRC) for assistance in developing a
scientifically sound approach for deciding whether or not to regulate contaminants on the current and
future CCLs. The NRC's Committee on Drinking Water Contaminants recommended that EPA: (1)
gather and anaryze health effects, exposure, treatment, and analytical methods data for each contaminant;
(2) conduct a preliminary risk assessment for each contaminant based on the available data; and (3) issue
a decision document for each contaminant describing me outcome of the preliminary risk assessment.
The NRC noted that in using mis decision framework, EPA should keep in mind the importance of
involving all interested parties.
One of ^e formal means by which EPA works with its stakeholders is through the National Drinking
Water Advfcory Council (NDWAC). TheNDWAC comprises members of the general public, State and
local agencies, and private groups concerned with safe drinking water, and advises the EPA Administrator
on key aspect of me Agency's drinking water program. The NDWAC provided specific
recommendations to EPA on a protocol to assist the Agency in making regulatory determinations for
current and future CCL contaminants. Separate but similar protocols were developed for chemical and
microbial contaminants. These protocols are intended to provide a consistent approach to evaluating
contaminants for regulatory determination, and to be a tool that will organize information in a manner that
will communicate the rationale for each determination to stakeholders. The possible outcomes of the
regulatory determination process are: a decision to regulate, a decision not to regulate, or a decision that
some other action is needed (e.g., issuance of guidance).
The NDWAC protocol uses the three statutory requirements of SDWA Section 1412(b)(l)(A)(i)-(iii)
(specified in section 1:2) as the foundation for guiding EPA in making regulatory determination
decisions. For each statutory requirement, evaluation criteria were developed and are summarized below.
To address whether a contaminant may have adverse effects on the health of persons (statutory
requirement (i)), the NDWAC recommended that EPA characterize the health risk and estimate a health
reference level for evaluating the occurrence data for each contaminant
Regarding whether a contaminant is known to occur, or whether there is substantial likelihood that
the contaminant will occur, in public water systems with a frequency, and at levels, of public health
concern (statutory requirement (ii)), the NDWAC recommended that EPA consider: (1) the actual and
estimated national percent of public water systems (PWSs) reporting detections above half the health
reference level; (2) the actual and estimated national percent of PWSs with detections above the health
reference level; and (3) the geographic distribution of the contaminant.
To address whether regulation of a contaminant presents a meaningful opportunity for health risk
reduction for persons served by public water systems (statutory requirement (iii)) the NDWAC
recommended that EPA consider estimating the national population exposed above half the health
reference level and the national population exposed above the health reference level.
The approach EPA used to make preliminary regulatory determinations followed the general format
recommended by the NRC and the NDWAC to satisfy the three SDWA requirements under section
1412(b)(l)(A)(i)-(iii). The process was independent of many of the more detailed and comprehensive
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
risk management factors that will influence the ultimate regulatory decision making process. Thus, a
decision to regulate is the beginning of the Agency regulatory development process, not the end.
Specifically, EPA characterized the human health effects that may result from exposure to a
contaminant found in drinking water. Based on this characterization, the Agency estimated a health
reference level (HRL) for each contaminant
For each contaminant EPA estimated the number of PWSs with detections >I/iHRL and >HRL, the
population served at these benchmark values, and the geographic distribution, using a large number of
occurrence data (approximately seven million analytical points) that broadly reflect national coverage.
Round 1 and Round 2 UCM data, evaluated for quality, completeness, bias, and representativeness, were
the primary data used to develop national occurrence estimates. Use and environmental release
information, additional drinking water data sets (e.g., State drinking water data sets, EPA National
Pesticide Survey, and Environmental Working Group data reviews), and ambient water quality data (e.g.,
NAWQA, State and regional studies, and the EPA Pesticides in Ground Water Database) were also
consulted.
The findings from these evaluations were used to determine if there was adequate information to
evaluate the three SDWA statutory requirements and to make a preliminary determination of whether to
regulate a contaminant.
1.5 Determination Outcome
After reviewing the best available public health and occurrence information, EPA has made a
preliminarily determination not to regulate hexachlorobutadiene with an NPDWR. EPA's preliminary
determination is based on the finding .that hexachlorobutadiene is not known to occur at levels of public
health concern. All preluninary CCL regulatory determinations will be presented in the Federal Register
Notice. The following sections summarize the data used by the Agency to reach this preluninary
decision.
2.0 CONTAMINANT DEFINITION
Hexachlorobutadiene, a volatile organic compound (VOC) also known as perchlorobutadiene, is a
colorless liquid with a turpentine-like odor. It is not known to naturally occur, but instead forms in the
production of other chemicals (ATSDR, 1995). It is commonly used as a solvent and in the production of
rubber compounds. Hexachlorobutadiene is also used as hydraulic and transformer fluid, a heat transfer
liquid, a pesticide, in gyroscopes, and in the production of lubricants (ATSDR, 1995: USEPA 1989-
Howard, 1989). '
2.1 Physical and Chemical Properties
Table 2-1 lists summary information regarding hexachlorobutadiene's physical and chemical
properties. Also included are its CAS Registry Number and molecular formula.
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Preliminary Regulatory Determination Support Document for HexacklorobutaeKene
November, 2001
Table 2-1; Physical and chemical properties
CAS number
Molecular Formula
87-68-3
Boiling Point
Melting Point
Molecular Weight
Water Solubility
Vapor Pressure
Henry's Law
Constant*
215 °C
-21°C
260.76 g/mol
3.67
4.78
2-2.55mg/Lat20°C
0.15mmHgat25°C
0.04 - 1.1
afterATSDR, 1994
^ note: this quantity is expressed in a dimensionless form.
2.2 Environmental Fate/Behavior
When hexachlorobutadiene is released to the environment, it is expected to volatilize quickly. Its
vapor pressure indicates that it will probably evaporate from surfaces, with the lowest evaporation rate
from soils because of its relatively high log K^. value (indicating its strong sorption potential). Its half
life in surface water ranges from 3-300 days, with a longer atmospheric half life that can be greater than a
year (Howard, 1989).
With a relatively high log K,,,., it has a strong sorption potential and therefore will not rapidly migrate
through the soil, though there is evidence it will leach through sandy soils. In the unsaturated zone, it
may biodegrade. However, based on laboratory tests, hexachlorobutadiene under anaerobic conditions
will probably not biodegrade(Howard, 1989).
Hexachlorobutadiene's high Henry's Law constant suggests it will quickly volatilize from water. But
because of its high 1C,,,., volatilization may be decreased because of adsorption to bed sediments,
suspended sediments, and biota. Volatilization will be quicker from turbulent streams when compared
with lakes. Hexachlorobutadiene may biodegrade in natural waters (Howard, 1989).
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
3.0 OCCURRENCE AND EXPOSURE
This section examines the occurrence of hexachlorobutadiene in drinking water. While no complete
national database exists of unregulated or regulated contaminants in drinking water from public water
systems (PWSs) collected under SDWA, this report aggregates and analyzes existing State data that have
been screened for quality, completeness, and representativeness. Populations served by PWSs exposed to
hexachlorobutadiene are estimated, and the occurrence data are examined for regional or other special
trends. To augment the incomplete national drinking water data and aid in the evaluation of occurrence,
information on the use and environmental release, as well as ambient occurrence of hexachlorobutadiene
is also reviewed. '
3.1 Use and Environmental Release
3.1.1 Production and Use
Hexachlorobutadiene has never been specifically manufectured as a commercial product in the United
States. However, significant quantities of the chemical are generated in the U.S.,as waste by-product
from the chlorination of hydrocarbons, and lesser quantities are imported mostly from Germany as
commercial product Hexachlorobutadiene is used as an intermediate product in rubber manufacturing
and chlorofluorocarbon and lubricant production, as well as for transformer and hydraulic fluids, fluid for
gyroscopes, heat transfer liquid, solvents, laboratory reagents, and as a wash liquor for removing C4 and
higher hydrocarbons. The chemical is also used as a fumigant in Russia, France, Italy, Greece Snain.and
Argentina (ATSDR, 1995; Howard, 1989). P-ft-na
Eight million pounds of hexachlorobutadiene were generated as a waste by-product in the U.S. in
1975, with 0.1 million pounds released into the environment. By 1982, the annual U.S. by-product
generation of the chemical had jumped to 27 million pounds. In contrast, the annual import rate of
hexacbJorobntadiene dropped from 500,000 Ibs/yr imported annually in the late 70's to 145 000 Ibs/vr
imported in 1981 (ATSDR, 1994; Howard, 1989). ' '
3.1.2 Environmental Release
Hexachlorobutadiene is listed as a toxic release inventory (TRI) chemical. In 1986, the Emergency
Planning and Community Right-to-Know Act (EPCRA) established the Toxic Release Inventory (TRI) of
hazardous chemicals. Created under the Superfund Amendments and Reauthorization Act (SARA) of
1986, EPCRA is also sometimes known as SARA Title HI. The EPCRA mandates that larger facilities
publicly report when TRI chemicals are released into the environment This public reporting is required
for facilities with more than 10 full-time employees that annually manufacture or produce more than
25,000 pounds, or use more than 10,000 pounds, of TRI chemical (USEPA, 1996; USEPA, 2000d).
Under these conditions, focilities are required to report the pounds per year of hexachlorobutadiene
released into the environment both on- and off-site. The on-site quantity is subdivided into air emissions
surface water discharges, underground injections, and releases to land (see Table 3-1). For
hexachlorobutadiene, air emissions constitute most of the on-site releases. Also, over the period for
which data is available (1988-1998) surface water discharges generally increased, peaked in 1992-93 and
then decreased significantly through the late 1990s. These TRI data for hexachlorobutadiene were
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
reported from eight States (CA, EL, KS, LA, NJ, NY, TX, UT); however, hexachlorobutadiene
contamination has often been found in remote areas far from apparent physical discharge sources
(USEPA, 2000b; Howard, 1989).
.!>
Table 3-1: Environmental releases (in pounds) for hexachlorobutadiene in the United States, 1988-
1998
Year
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
Air
Emissions
2,421
1,415
2,381
3,310
. 1,410
1,747
4,134
3,410
4,906
4,628
2,508
On-Site Releases
Surface Water
Discharges
5
9
256
661
351
1,200
1,911
681
715
622
153
Underground
Injection
0
299
952
434
201
520
738
200
330
330
220
Releases
to Land
0
0
0
0
0
0
0
2
0
1
0
Off-Site
Releases
510
200
310
252
430
12
5
4,263
45
26,343
19,640
Total On- &
Off-site
Releases
2,936
1,923
3,899
4,657
2^92
3,479
6,788
8,556
5,996
31,924
22.521
after USEPA, 2000b
Although the TRI data can be useful in giving a general idea of release trends, it is far from
exhaustive and has significant limitations. For example, only industries which meet TRI criteria (at least
10 full-time employees and manufacture and processing of quantities exceeding 25,000 Ibs/yr, or use of
more man 10,000 Ibs/yr) are required to report releases. These reporting criteria do not account for
releases from smaller industries. Threshold manufacture and processing quantities also changed from
1988-1990 (dropping from 75,000 Ibs/yr in 1988 to 50,000 Ibs/yr in 1989 to its current 25,000 Ibs/yr in
1990) creating possibly misleading data trends. Finally, the TRI data is meant to reflect releases and
should not be used to estimate general exposure to a chemical (USEPA, 2000c; USEPA, 2000a).
While TRI releases were reported in only eight States, the use of hexachlorobutadiene is widespread.
It is included in the Agency for Toxic Substances and Disease Registry's (ATSDR) Hazardous Substance
Release and Health Effects Database (HazDat) and has been detected in site samples in fourteen States
(AL, AZ, CT, IA, LA, MI, MN, NJ, NY, OH, PA, RI, SC, WA; ATSDR, 2000). These States are
distributed nationwide and include 11 States, and two regions (New England and the Pacific Northwest),
not reporting TRI releases yet manifesting hexachlorobutadiene detections in the environment
The National Priorities List (NPL) of hazardous waste sites, created in 1980 by CERCLA, is a listing
of some of the most health-threatening waste sites in the United States. Hexachlorobutadiene was
detected in eleven of the Final NPL sites in 1999. These sites are located in eight States: AK, CO, IN,
LA, NJ, OH, PA, WA. Again, note there is little overlap between these States and the eight TRI reporting
States (USEPA, 1999c).
In summary, although hexachlorobutadiene is not manufactured in the United States, both its use in
industry and occurrence in the environment are widespread. Significant quantities of
hexachlorobutadiene are generated in the United States as a waste by-product, and smaller quantities are
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
imported for industrial needs. Hexachlorobutadiene is present in hazardous waste sites in at least 8 States
(atNPL sites), has been detected in site samples in at least 14 States (listed in ATSDR's HazDat), and has
been released into the environment directly hi at least 8 States (based on TRI data).
3.2 Ambient Occurrence
To understand the presence of a chemical in the environment, an examination of ambient occurrence
is useful. In a drinking water context, ambient water is source water existing hi surface waters and
aquifers before treatment The most comprehensive and nationally representative data describing ambient
water quality in the United States are being produced through the United States Geological Survey's
(USGS) National Water Quality Assessment (NAWQA) program. (NAWQA, however, is a relatively
young program and complete national data are not yet available from their entire array of sites across the
nation.)
3.2.1 Data Sources and Methods
To examine water quality status and trends hi the United States, the USGS instituted the NAWQA
program in 1991. NAWQA is designed and implemented hi such a manner as to allow consistency and
comparison between representative study basins located around the country, facilitating interpretation of
natural and anthropogenic factors affecting water quality (Leahy and Thompson, 1994).
The NAWQA program consists of 59 significant watersheds and aquifers referred to as "study units."
The study units represent approximately two thirds of the overall water usage hi the United States and a
similar proportion of the population served by public water systems. Approximately one half of the
nation's land area is represented (Leahy and Thompson, 1994).
To facilitate management and make the program cost-effective, approximately one third of the study
units at a time engage hi intensive assessment for a period of 3 to 5 years. This is followed by a period of
less intensive research and monitoring that lasts between 5 and 7 years. This way all 59 study units rotate
through intensive assessment over a ten-year period (Leahy and Thompson, 1994). The first round of
intensive monitoring (1991-96) targeted 20 watersheds. This first group was more heavily slanted toward
agricultural basins. A national synthesis of results from these study units and other research initiatives
focusing on pesticides and nutrients is being compiled and analyzed (Kolpin et al., 2000; Larson et al.,
1999).
For volatile organic chemicals (VOCs), the national synthesis will compile data from the first and
second rounds of intensive assessments. Study units assessed hi the second round represent conditions hi
more urbanized basins, but initial results are not yet available. However, VOCs were analyzed hi the first
round of intensive monitoring and data are available for these study units (Squillace et al., 1999). The
minimum reporting limit (MRL) for most VOCs, including hexachlorobutadiene, was 0.2 ug/L (Squillace
etal., 1999).
Furthermore, the NAWQA program has compiled, by study unit, data collected from local, State, and
other Federal agencies to augment its own data. The data set provides an assessment of VOCs hi
untreated ambient ground.water of the conterminous United States for the period 1985-1995 (Squillace et
al., 1999). Data were included hi the compilation if they met certain criteria for collection, analysis, well
network design, and well construction (Lapham et al., 1997). They represent both rural and urban areas,
8
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2m
:uence
3.2.2 Results
States rbr the years 1985-1995(sffia
et al, 1999).
«.^fetenntoorc United
3.3 Drinking Water Occurrence
nanto b a d ato 52? '^ ° in?)miation on
non-pm-chased community water systems (C\Snd non ±S T? n°tregulations were ^deA All
systems (NTOCWSs), with greateTthan 150 Scefo^Z? »***•»* non-communily water
unregulated contaminant mo^torins SmaHi ^t^ ' re reqmred to conduct ^s
federal regulations, but were7eS£ tolSe aSff Were.notre*uredtocon^ct monitoring under
necessary. Many Slates coSS fom Se™^ AHH'^ §f 6 decided s*<* ^niforing was
Unregulated ContaminanfiMonitoring S^oSS nTS9^ SSS? ^taminants were add«d to the
monitoring that began in 1993 (USEPA, 1992; ^BR3 1776) ^ ^ 3526) ^^^^
"* ^ thr°Ughout ^ 199
lished January 8, 1999
^ 19" (USEPA- 1999b'
^ develoPed> fee Agency
but ceased for small
(USEPA, 1999a; 64 FR
onamnanttom
64 FR 50556) and effective Janua^f, 200? TfS
concluded there were adequate monitoring ; dte for
continued hexachlorobuSiene n
.1 »ata Sources, Data Quality, and Analytical Approach
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene November, 2001
findings presented in this report are based on a national cross-section of aggregated state data (i.e., a
representative subset if there is available state data) derived from the SDWIS/FED database.
The National Contaminant Occurrence Database (NCOD) is an interface to the actual occurrence data
stored in the Safe Drinking Water Information System (Federal version; SDWIS/FED) and can be queried
to provide a summary of the data in SDWIS/FED for a particular contaminant The data used in this
report were derived from the data in SDWIS/FED and another database called the Unregulated
Contaminant Information System (URCIS). Note, however, mat the SDWIS/FED data in mis report have
been reviewed, edited, and filtered to meet various data quality objectives for the purposes of mis
analysis. Hence, not all data from a particular source were used, only data meeting the quality objectives
described below. The sources of these data, their quality and national aggregation, and me analytical
methods used to estimate a given contaminant's national occurrence (from these data) are discussed in
this section (for further details see USEPA, 2001a,200Ic).
33.1.1 UCM Rounds land 2
The 1987 UCM contaminants include 34 volatile organic compounds (VOCs), divided into two
groups: one with 20 VOCs for mandatory monitoring, and the other with 14 VOCs for discretionary
monitoring (USEPA, 1987; 52 FR 25690). Hexachlorobutadiene was among the 14 VOCs included for
discretionary monitoring. The UCM (1987) contaminants were first monitored coincident with the Phase
I regulated contaminants, during the 1988-1992 period. This period is often referred to as "Round 1"
monitoring. The monitoring data collected by the PWSs were reported to the States (as primacy agents)
but there was no protocol in place to report these data to EPA. These data from Round 1 were collected'
by EPA from many States over time.
The Round 1 data were put into a database called the Unregulated Contaminant Information System,
or URCIS. Most of the Phase 1 regulated contaminants were also VOCs. Both the unregulated and
regulated VOCs are analyzed using the same sample and the same laboratory methods. Hence, the
URCIS database includes data on all of these 62 contaminants: the 34 UCM (1987) VOCs; the'21
regulated Phase 1 VOCs; 2 regulated synthetic organic contaminants (SOCs); and 5 miscellaneous
contaminants that were voluntarily reported by some States (e.g., isomers of other organic contaminants).
The 1993 UCM contaminants include 13 SOCs and 1 inorganic contaminant (IOC) (USEPA 1992-
57 FR 31776). Monitoring for the UCM (1993) contaminants began coincident with the Phase IW
regulated contaminants in 1993 through 1998. This is often referred to as "Round 2" monitoring The
UCM (1987) contaminants were also included in the Round 2 monitoring. As with other monitoring data
PWSs reported these results to the States. EPA, during the past several years, requested that the States
submit these historic data to EPA.
The details of the actual individual monitoring periods are complex. The timing of required
monitoring was staggered-related to different size classes of PWSs, and the program was implemented
somewhat differently by different States. While Round 1 includes the period from 1988-1992, it also
includes results from samples analyzed prior to 1988 that were "grandfathered" into the database For
further details see EPA (2001a, 2001c).
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3.3.1.2 Developing a Nationally Representative Perspective
The Round 1 and Round 2 databases contain contaminant occurrence date from a total of 40 and 35
primacy entities (largely States), respectively. However, data from some States are incomplete and
biased. Furthermore, the national representativeness of the data is problematic because the data were not
collected in a systematic or random statistical framework. These State data could be heavily skewed to
low-occurrence or Mgh-occurrence settings. Hence, the State data were evaluated based on polhition-
potential indicators and the spatial/hydrologic diversity of the nation. This evaluation enabled the
construction of a cross-section from the available State data sets that provides a reasonable representation
of national occurrence.
A national cross-section comprised of the Round 2 state contaminant occurrence databases was
established using the approach developed for the EPA report^ Review of Contaminant Occurrence in
Public Water Systems (USEPA, 1999d). This approach was developedto support occurrence analyses for
EPA's Chemical Monitoring Reform (CMR) evaluation, and was supported by peer reviewers and
stakeholders. The approach cannot provide a "statistically representative" sample because the original
monitoring data were not collected or reported in an appropriate fashion. However, the resultant
"national cross-section" of states should provide a clear indication of the central tendency of the national
data. The remainder of this section provides a summary description of how the national cross-section
from the SDWIS/FED (Round 2) database was developed!. The details of the approach are presented in
other documents (USEPA, 2001a, 2001b); readers are referred to these for more specific information.
33.1.2.1 Cross-Section Development
As a first step in developing the cross-section, the State data contained in the URCIS database (that
contains the Round 1 monitoring results) and SDWIS/FED database (that contains the Round 2
monitoring results) were evaluated for completeness and quality. For both the URCIS (Round 1) and
SDWIS/FED (Round 2) databases, some State data were unusable for a variety of reasons. Some States
reported only detections, or the data was recorded with incorrect units. Data sets only including
detections are obviously biased, over-representing high-occurrence settings. Other problems included
substantially incomplete data sets without all PWSs reporting. Also, data from Washington, D.C. and the
Virgin Islands were excluded from this analysis because it was difficult to evaluate them for the current
purposes in relation to complete State data (USEPA, 2001a Sections II and IB).
The balance of the States remaining after the data quality screening were then examined to establish a
national cross-section. This step was based on evaluating the States' pollution potential and geographic
coverage in relation to all States. Pollution potential is considered to ensure a selection of States that
represent the range of likely contaminant occurrence and a balance with regard to likely high and low
occurrence. Geographic consideration is included so that the wide range of climatic and hydrogeologic
conditions across the United States are represented, again balancing the varied conditions mat affect
transport and fate of contaminants, as well as conditions that affect naturally occurring contaminants
(USEPA, 2001c Sections m.A. and m.B.).
The cross-section States were selected to represent a variety of pollution potential conditions. Two
primary pollution potential indicators were used. The first factor selected indicates pollution potential
from manufacturing/population density and serves as an indicator of the potential for VOC contamination
within a State. Agriculture was selected as the second pollution potential indicator because the majority
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
of SOCs of concern are pesticides (USEPA, 2001c Section m.A.). The 50 individual States were ranked
from highest to lowest based on the pollution potential indicator data. For example, the State with the
highest ranking for pollution potential from manufacturing received a ranking of 1 for this factor and the
State with the lowest value was ranked as number 50. States were ranked for their agricultural chemical
use status in a similar fashion.
The States' pollution potential rankings for each factor were subdivided into four quartiles (from
highest to lowest pollution potential). The cross-section States were chosen equally from all quartiles for
both pollution potential factors to ensure representation, for example, from: States with high agrochemical
pollution potential rankings and high manufacturing pollution potential rankings; States with high
agrochemical pollution potential rankings and low manufacturing pollution potential rankings; States with
low agrochemical pollution potential rankings and high manufacturing pollution potential rankings; and
States with low agrochemical pollution potential rankings and low manufacturing pollution potential
rankings (USEPA, 2001 c Section HUB.). In addition, some secondary pollution potential indicators were
considered to further ensure that the cross-section States included the spectrum of pollution potential
conditions (high to low). At the same time, states within the specific quartiles were considered
collectively across all quartiles to attempt to provide a geographic coverage across all regions of the
United States.
The data quality screening, pollution potential rankings, and geographic coverage analysis established
national cross-sections of 24 Round 1 (URCIS) States and 20 Round 2 (SDWIS/FED) States. In each
cross-section, the States provide good representation of the nation's varied climatic and hydrogeologic
regimes and the breadth of pollution potential for the contaminant groups (Table 3-2 and Figure 3-1).
33.1.2.2 Cross-Section Evaluation
To evaluate and validate the method for creating the national cross-sections, the method was used to
create smaller State subsets from the 24-State, Round 1 cross-section. Again, States were chosen to
achieve a balance from the quartiles describing pollution potential, and a balanced geographic
distribution, to incrementally build subset cross-sections of various sizes. For example, the Round 1
cross-section was tested with subsets of 4,8 (the first 4 State subset plus 4 more States), and 13 (8 State
subset plus 5) States. Two additional, cross-sections were included hi the analysis for comparison; a
cross-section composed of 16 States with biased data eliminated from the 24-State cross-section for data
quality reasons and a cross-section composed of all 40 Round 1 States (USEPA, 2001c Section DI.B.1).
These Round 1 incremental cross-sections were then used to evaluate occurrence for an array of both
high and low occurrence contaminants. The comparative results illustrate several points. The results are
quite stable and consistent for the 8-, 13- and 24-State cross-sections. They are much less so for the 4-
State, 16-State (biased), and 40-State (all Round 1 States) cross-sections. The 4-State cross-section is
apparently too small to provide balance both geographically and with pollution potential, a finding that
concurs with past work (USEPA, 1999d). The CMR analysis suggested that a minimum of 6-7 States was
needed to provide balance both geographically and with pollution potential, and the CMR report used 8-
States out of the available data for its nationally representative cross-section. The 16-State and 40-State
cross-sections, both including biased States, provided occurrence results that were unstable and
inconsistent for a variety of reasons associated with their data quality problems (USEPA, 2001c Section
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The 8-, 13-, and 24-State cross-sections provide very comparable results, are consistent; and are
usable as national cross-sections to provide estimates of contaminant occurrence. Including greater data
from more States improves the national representation and the confidence in the results— as long as the
States are balanced related to pollution potential and spatial coverage. The 24- and 20-State cross-
sections provide the best, nationally representative cross-sections for the Round 1 and Round 2 data.
Table 3-2: Cross-section States for Round 1 (24 States) and Round 2 (20 States)
Round 1 (URCIS)
Alabama
Alaska*
Arizona
California
Florida
Georgia
Hawaii
Illinois
Indiana
Iowa
Kentucky*
Maryland*
Minnesota*
Montana
New Jersey
NewMexico*
North Carolina*
Ohio*
South Dakota
Tennessee
Utah
Washington*
West Virginia
Wyoming
Round 2 (SDWIS/FED)
Alaska*
Arkansas
Colorado
Kentucky*
Maine
Maryland*
Massachusetts
Michigan
Minnesota*
Missouri
New Hampshire
New Mexico*
North Carolina*
North Dakota
Ohio*
Oklahoma
Oregon
Rhode Island
Texas
Washington*
* cross-section State in both Round 1 and Round 2
Figure 3-1: Geographic distribution of cross-section States for Round 1 (left) and Round 2 (right)
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33.13 Data Management and Analysis
The cross-section analyses focused on occurrence at the water system level; i.e., the summary data
presented discuss the percentage of public water systems with detections, not the percentage of samples
with detections By normalizing the analytical data to the system level, skewness inherent in me sample
data, particularly over the multi-year period covered in the URCIS data, is avoided. System level analysis
SSaTlf"* S ^ J1 kn°Wn contaminant Problem «sualty has to sample more frequently than a
PWS that has never detected the contaminant Obviousry, the results of a simple computation ofthe
percentage of samples with detections (or other statistics) can be skewed by the more frequent sampling
results reported by the contaminated site. This level of analysis is conservative. For example a system
need only have a single sample with an analytical result greater than me minimum reporting lunit (MRL)
i.e., a detection, to be counted as a system with a result "greater than the MRL."
Also, the data used ii&he analyses were limited to only those data with confirmed water source and
sampling type ^information. Only standard SDWA compliance samples were used; "special" samples or
investigation samples (investigating a contaminant problem that would biasresults) or samples of '
unknown type were not used in the analyses. Various quality control and review checks were made ofthe
results, including follow-up questions to the States providing the data. Many ofthe most intractable data
quality problems encountered occurred with older data. These problematic data were, in some cases
simply eliminated from the analysis. For example, when the number of problematic data were
33.1.4 Occurrence Analysis
To evaluate national contaminant occurrence, a two-stage analytical approach has been developed
The first stage of analysis provides a straightforward, conservative, non-parametric evaluation of
occurrence ofthe CCL regulatory determination priority contaminants as described above These Stage 1
descriptive statistics are summarized here. Based in part on the findings ofthe Stage 1 Analysis EPA
will determine whether more rigorous parametric statistical evaluations, the Stage 2 Analysis may be
warranted to generate national probability estimates of contaminant occurrence and exposure'for priority
contaminants (for details on this two stage analytical approach see Cadmus, 2000, 2001).
The summary descriptive statistics presented in Table 3-3 for hexachlorobutadiene are a result ofthe
e1Q^yS1Sand^CludedatafrombothRound l W&CIS, 1987-1992) and Round 2 (SDWIS/FED
2 997>,CT00s^sectlollS.ftes- ^«ded are me total number of samples, me percent samples with '
detections the 99* percentile concentration of all samples, the 99* percentile concentration of samples
with detections, and the median concentration of samples with detections. The percentages of PWSs and
population served indicate the proportion of PWSs whose analytical results showed a detections) ofthe
ZS* £T^1^tt0n'T> ^ 3t "* *•* dUling me monitoring P^°d; or a detection( ) greater
fcan half the Health Reference Level (HRL); or a detections) greater than the Health Reference Level
The Health Reference Level, 0.9 ug/L, is a preliminary estimated health effect level used for mis analysis
The^wasdmvedusmgmelO^cancerriskascalculatedbymelinearmethodandusingabody '
weight to the three quarter power (slope factor 4 x 10'2 (mg/kg-day)'1).
The 99th percentile concentration is used here as a summary statistic to indicate the upper bound of
occurrence values because maximum values can be extreme values (outliers) that sometimes result from
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November, 2001
sampling or reporting error. The 99th percentile concentration is presented for both the samples with only
detections and all of the samples because the value for the 99th percentile concentration of all samples is
below the Minimum Reporting Level (MRL) (denoted by "<" in Table 3-3). For the same reason,
summary statistics such as the 95* percentile concentration of all samples or the median (or mean)
concentration of all samples are omitted because these also are all "<" values. This is the case because
only 0.1% to 0.05% of all samples recorded detections of hexachlorobutadiene in Round 1 and Round 2.
As a simplifying assumption, a value of half the MRL is often used as an estimate of the
concentration of a contaminant in samples/systems whose results are less than the MRL. With a
contaminant with relatively low occurrence such as hexachlorobutadiene in drinking water occurrence
databases, the median or mean value of occurrence using this assumption would be half the MRL (0.5 *
MRL). However, for these occurrence data this is not straightforward. For Round 1 and Round 2, States
have reported a wide range of values for the MRLs. This is in part related to State date management
differences as well as real differences in analytical methods, laboratories, and other factors.
The situation can cause confusion when examining descriptive statistics for occurrence. For example,
the modal MRL value for the Round 1 samples is 0.50 ug/L-a value twice as large as the median
concentration of detections for Round 1 (0.25 ug/L) (This occurs because some States and/or systems
reporting detections were using a lower MRL and had positive results lower than the MRL used by other
States or systems). For Round 2, most States reported non-detections as zeros resulting in a modal MRL
value of zero. By definition the MRL cannot be zero. This is an artifact of State data management
systems. Because a simple meaningful summary statistic is not available to describe the various reported
MRLs, and to avoid confusion, MRLs are not reported in the summary table (Table 3-3).
. , - . .a ; . • •.. • :..-.--• .'. " •
In Table 3-3, national occurrence is estimated by extrapolating the summary statistics for the 24 and
20 State cross-sections to national numbers for systems, and population served by systems, from the
Water Industry Baseline Handbook, Second Edition (USEPA, 2000e). From the handbook, the total
number of community water systems (CWSs) plus non-transient, non-community water systems
(NTNCWSs) is 65,030, and the total population served by CWSs plus NTNCWSs is 213,008,182 persons
(see Table 3-3). To arrive at the national occurrence estimate for a particular cross-section, the national
estimate for PWSs (or population served by PWSs) is simply multiplied by the percentage for the given
summary statistic, [i.e. for Round 1, the national estimate for the total number of PWSs with detections
(228) is the product of the percentage of Round 1 PWSs with detections (0.35%) and the national estimate
for the total number of PWSs (65,030)].
Because the State data used for the cross-section are not a strict statistical sample, national
extrapolations of these Stage 1 analytical results can be problematic, especially for contaminants with
very low occurrence like hexachlorobutadiene and other CCL regulatory determination priority
contaminants. For this reason, the nationally extrapolated estimates of occurrence based on Stage 1
results are not presented in the Federal .Register Notice. The presentation in the Federal Register Notice
of only the actual results of the cross-section analysis maintains a straight-forward presentation, and the
integrity of the data, for stakeholder review. The nationally extrapolated Stage 1 occurrence values are
presented here, however, to provide additional perspective. A more rigorous statistical modeling effort,
the Stage 2 analysis, could be conducted on the cross-section data (Cadmus, 2001). The Stage 2 results
would be more statistically robust and more suitable to national extrapolation. This approach would
provide a probability estimate and would also allow for better quantification of estimation error.
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene November, 2001
Round 1(1987-1992) and Round 2 (1993-1997) data were not merged because they represent
different time periods, different States (only eight States are represented in both rounds), and each round
has different data management and data quality problems. The two rounds are only merged for the simple
spatial analysis overview presented in Section 3.3.2.2 and Figures 3-2 and 3-4.
33.2 Results
33.2.1 Occurrence Estimates
wJ?e StEteS ^ detections of hexachlorobutadiene are widespread (Figure 3-2), the percentages of
PWSs by State with detections are low (Table 3-3). In aggregate, the cross-sections show only 0.2% -
0.4% of PWSs in both rounds experienced detections (> MRL), affecting 0.9% - 2.4% of the population
served (approximately 2 - 5 million people). Percentages of PWSs with detections greater than half the
Health Reference Level (> '/2 HRL) are slightly lower: 0.1% - 0.2%. The percentage of PWSs exceeding
the Health Reference Level (> HRL) for both rounds is very small (see also Figure 3-4). Between 0 02%
and 0.1% of PWSs in Rounds 1 and 2 experienced detections > HRL, affecting a population of
approximately 10,000 - 750,000.
There are some qualifying notes for both rounds of data that warrant discussion. The Round 1
estimates of PWSs affected by hexachlorobutadiene are influenced by the State of Florida (Table 3-3-
Figures 3-3 and 3-4). This State reports that 5.4% of its PWSs experienced detections greater than the
HRL during Round 1, a value considerably greater than the next highest State (1.5%). This suggests that
Florida s data for hexachlorobutadiene is incomplete and may be biased. Out of 855 Florida PWSs
reporting contaminant data for Round 1 monitoring, only 112 provided data for hexachlorobutadiene
flUSEPA, 2001a). Also, the 5.4% of systems reporting detections all reported concentrations greater than
the Health Reference Level. These figures suggest that perhaps only systems experiencing problems
submitted data for hexachlorobutadiene, biasing Florida's results for occurrence measures examined in
this report.
The large values for the Round 2 national estimates of population served with detections greater than
the MRL and greater than half the HRL are influenced by the inclusion of one PWS serving a very large
population (1.5 million people). While the percentage of systems with detections of hexachlorobutadiene
are similar (both rounds show low values, 0.2% - 0.4% PWSs > MRL), the difference in population
served results in a larger difference in the population extrapolations.
bsrveu oy raose systems;. Because some public water systems are seasonally classified as either sur
or ground water, some systems may be counted in both categories. The population numbers for the
Round 1 cross-section are also incomplete. Not all of the PWSs for which occurrence data was submitted
reported the population they served. (However, the population numbers presented in Table 3-3 for the
Round 1 cross-section are reported from 94% of the systems.)
The national estimates extrapolated from Round 1 and Round 2 PWS numbers and populations are
not additive either. In addition to the Round 1 classification and reporting issues outlined above the
proportions of surface water and ground water PWSs, and populations served by them, are different
between the Round 1 and 2 cross-sections and the national estimates. For example, approximately 49%
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November, 2001
of the population served by PWSs in the&ound 1 cross-section States are served by surface water PWSs
(Table 3-3). Nationally, however, flbat proportion changes to 60%.
Both Round 1 and Round 2 national cross-sections show a proportionate balance in PWS source
. waters compared to the national inventory. Nationally, 91% of PWSs use ground water (and 9% surface
waters): Round 1 shows 89%, and Round 2 shows 90% of systems using ground water. The relative
populations served are not as closely comparable. Nationally, about 40% of the population is served by
PWSs using ground water (and 60% by surface water). Round 2 data is most representative with 37% of
the cross-section population served by ground water; Round 1 shows about 55%.
There are differences in the occurrence results between Round 1 and Round 2, as should be expected.
The differences are not great, however, particularly when comparing the proportions of systems affected.
The results range from 0.2% - 0.4% of PWSs with detections of hexachlorobutadiene and range from
0.02% to 0.1% of PWSs with detections greater than the Health Reference Level of 0.9 ng/L. These are
not substantively different, given Ihe data sources.
The differences in the population extrapolations appear greater, but still constitute relatively small
proportions of the population. The most pronounced difference is in the estimate of the population served
by PWSs with detections greater than the Health Reference Level, ranging from 10,000 to 750,000. In
both cases, this is less than 0.5% of the population. The difference in this category is largely driven by
the Florida data in Round 1, as discussed above.
The Round 2 cross-section provides a better proportional balance related to Ihe national population of
PWSs and may have fewer reporting problems than Round 1 (i.e., incomplete population numbers,
Florida). The larger estimate of the national population served by PWSs with detections greater than the
Health Reference Level using Round 1 data can also provide an upper bound estimate in considering the
data.
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Table 3-3: Summary occurrence statistics for hexachlorobutadiene
Freaoewcr Factors
Total Nnmberof Samples
Percent of Samples with Detections
99 Percentfle Concentration fall samples)
Health Reference Level
Minimum Reporting Level (MRL)
99U Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of QWPWSs
Number of SW PWSs
Total Population
Population of OW PWSs
Peculation of SW PWSs
Occurrence bv Svstem
% PWSs with detections (> MRL)
Range of Cross-Section States
GW PWSs with detections
SW PWSs with detections
% PWSs > 1/2 Health Reference Level (HRL)
Range of Cross-Section States
GW PWSs > 1/2 Health Reference Level
SW PWS»> 1/2 Health Reference Level
•/• PWSs > Health Reference Level
Range of Cross-Section States
GW PWSs > Health Reference Level
SW PWSs > Health Reference Level
>ccorrence bv Ponnl.tion Served
% PWS Population Served with detections '
Range of Cross-Section States
GW PWS Population with detections
SW PWS Population with detections
% PWS Population Served > 1/2 Health Reference Level
Range of Cross-Section States
GW PWS Population > l/2,Health Reference Level
SW PWS Population > 1/2 Health Reference Level
% PWS Population Served > Health Reference Level
' Range of Cross-Section States
GW PWS Population > Health Reference Level
SW PWS Peculation > Health Reference Level
24 State
Cross-Section1
monad 11
42^39
0.13%
< (Non-detect)
0.9pg/L
Variable*
lOujs/L
0.25|ig/L
12,284
10,980
1,385
71,582,571
40,399,177
34.418.834
0350%
0 - 5.36%
0.301%
0.722%
0.163%
0 - 536%
0.118%
0.505%
0.114%
» - 536%
0.064%
0.505%
0.896%
0 - 11.38%
1.458%
0.153%
0.569%
0 - 11.38%
0.978%
0.036%
0.367%
0 - 9.66%
0.619%
0.036%
20 State
Croat-Section2
ntnnnd 2t
93,585
0.05%
< (Non-detect)
0.9|ig/L
Variable*
1.5UR/L
0.30 ng/L
22,736
20380
2356
67,075,493
24,960,222
42.115.271
0.180%
0 - 336%
0.132%
0.594%
0.079%
0 - 0.51%
0.064%
0.212%
0.018%
0 - 0.24%
0.005%
0.127%
2.360%
0 - 29.93%
0.186%
3.649%
2.331%
0 - 29.92%
0.177%
3.607%
0.005%
0 - 0.02%
0.011%
0.001%
National System &
Population Nnmberu3
_
_
V1 _
_
L
w.
65,030
59,440
5,590
213,008,182
85,681,696
127326.486
National Extrapolation*
Round 1 Round 2
228 I 17
N/A N/A
m7O
/"
40 33
106 51
N/A N/A
70 38
28 12
74 11
WA N/A
rt/jn. IN//\
38 3
28 7
1,909,000 5,027,000
N/A N/A
1,249,000 159,000
194,000 4,646,000
1,213,000 4,965,000
N/A N/A
838,000 152,000
46,000 4,593,000
781,000 10,000
N/A N/A
,pl//\ IN/A
531,000 9,000
46.000 i.nnn
/. Summary Results based on data from 24-State Cross-Section, from URCIS, UCM (1987) Round 1.
2. Summary Results based on datafrom20-State Cross-Section, from SDWIS/FED, UCM (1993) Round 2
3. Total PWS andpopulationntmbers are from EPA March 2000 Water Industry Baseline Handbook
4. National extrapolations are from the 24-State data and20-State data using the Baseline Handbook system and population number
~£^"£* % Water^stems- GW= GrmmdWater; SW = Surface Water; MRL ^Minimum Reporting Level (for laboratory analyses);
' «T%~ , Rtference Level, an estimated health effect level used for preliminary assessment for this review; N/A = Not Applicable
-The Health Reference Level used for hexachlorobutadiene is 0.9 fig/L. This is a draft value for working review only.
- Total Number of Samples = the total number of analytical records for hexachlorobutadiene.
~ MedimConcentratton of Detections = the median analytical value of all the detections (analytical results greater than the MRL) Cm ugO.)
-TotalNumber ofPWSs = the totalnumber of'public water systems with recordsfor'hexachlorobutadiene.
- TotalPopulation Served'- the total population served by public water systems with records for hexachlorobutadiene.
-XPW»itod*ections.%PWS>HHealthReferenceLevel.%PWS>HealthReferenceLeve^
systems vnth at least one analytical result that exceeded the MRL, 'A Health Reference Level, Health Reference Level, respectively.
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
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3.3.2.2 Regional Patterns
Occurrence results are displayed graphically by State in Figures 3-2,3-3, and 3-4 to assess whether
any distinct regional patterns of occurrence are present Combining Round 1 and Round 2 data (Figure 3-
2), there are forty-seven States reporting. Six of those States have no data for hexachlorobutadiene, while
another 21 have no detections of the chemical. The remaining 20 States have detecteii
hexachlorobutadiene in drinking water and are well distributed throughout the United States.
The simple spatial analysis presented in Figures !3-2,3-3^and 3-4 suggests that special regional
analyses are not warranted. Florida'sjpossibfe bias is notable, however. While no clear geographical
patterns of occurrence are apparent, comparisons with environmental use and release information are
useful (see also Section 3,1). tFiye of theeight Toxic Release Mventory States that reported releases of
hexachlorobutadiene into theeriviroranent between 1988 and 199:8 have also detected the chemical in
PWS sampling. Of the remaining thi^ |Kansas,Louisiana, and 'California), Kansas hasn*t reported any
data for either Round I1 or 2. Also, of the eight States ^vrath detections of hexachlbrobutadiene at
CERCLA National Priorities List (NPL) hazardous waste sites, five have detected the chemical in
drinking water. Finally, six of the States detecting hexachlorobutadiene in PWS samples have also
detected it in site samples reported to the ATSBR's HazDat database. It is interesting to note that neither
Alabama nor Florida, the two States with the highest percentage of PWSs with detections greater than the
Health Reference level, are; Toxic Release Inventory Stetes for hexachlorobutadiene nor do they have
CERCLA NPL sites with detections of the chemical (Figure 3-4).
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
Figure 3-2: States with PWSs with detections of hexachlorobutadiene for all States with data fin
URCIS (Round 1) and SDWIS/FED (Round 2)
All States
Hcxcchlorobntadlene Detections
in Roond 1 and Round 2
~~1 States not in Round 1 or Round 2
gg] No data for Hexachlorobutadiene
States with No Detections (No PWSs > MRL)
|B States with Detections (Any PWSs > MRL)
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
Figure 3-3: States with PWSs with detections of hexachlorobutadiene (any PWSs with results
greater than the Minimum Reporting Level [MRLJ) for Round 1 (above) and Round 2 (below)
cross-section States
• San ofFIorida Is an under will S.3SK PWS > MRL
HeiftcUerebiitmdfeBe Occarreaee IB Rouad 1
f~~l States not in Cross-Section
r3a No data for Hexachloibutadienc
0.00% PWSs > MRL
PBj 0.01-1.00% PWSs > MRL
•• 1.00-330% PWSs > MRL*
HexacUorobntBdieBC Occarreace
fa Round 2
^^ Slates not in Cross-Section
*^£| No d>ta for Hexachloifoutadtene
0.0054 PWSs > MRL
tim 0.01 - LOOK PWSs > MRL
•I 1.00 - 3.50% PWSs > MRL
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
Figure 3-4: Cross-section States (Round 1 and Round 2 combined) with PWSs with detections of
hexachlorobutadiene (above) and concentrations greater than the Health Reference Level (below)
n coder witk! JB4PWS >MRL
HexKUorobMidieae Occummce
fa Rw«d 1 ind Round 2
S States not in Cross-Section
No dtta for Hexacblorbutadicne
0.00% PWSs >MRL
0.01 -1.00% PWSs > MRL
1.00 -3.50% PWSs > MRL*
•S»IoofFloriiib«noiitlirwiai5J6%PWS>HRL
HexBcUorobniadieae Ocearreace
b Roind 1 >nd Roaid 2
I Stats not in Cross-Section
SM No data for Hexachlorobutadfen:
IS 0.00% PWSs >HRL
Hi 0.01 -1.00% PWSs > HRL
•I 1.00-3 J0% PWSs > HRL*
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Preliminary Regulatory Determination Support Document far Hexachlorobutadiene
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3.4 Conclusion
While there have-not been detections of hexachlorobutadiene in ambient water reported in USGS
NAWQA studies to date, it has been detected at a very low percentage of ATSDR HazDat sites and
CERCLA NPL sites.; Furthermore, releases have been reported through the Toxic Release Inventory.
Hexachlorobutadiene has also been detected in PWS samples collected under SDWA. Occurrence
estimates are low for Round 1 and Round 2 UCM monitoring wife only 0.13% and 0.05% of afl samples
showing detections, respectively. Significantly, the values for the 99th percentile and median
concentrations of all samples are less than the Minimum Reporting Level. For Round 1 samples with
detections, the median concentration is 0.25 ug/L and the 99* percentile concentration is 10 ug/L.
Median and 99th percentile concentrations for Round 2detections are 0;30 ug/L and 1.5 ug/L,
respectively. Systems with detections only constitute 6.4% of Round 1 systems and 0.2% for Round 2.
National estimates for the population served by PWSs with detections are also low, especially for
detections greater than the Health Reference Level; For both rounds, these estimates are less than 0.5% of
the national PWS population (Round 1:754,537; Round 2:9,721).
4.0 HEALTH EFFECTS
A description of the health effects and available dose-response information associated with exposure
to hexachlorobutadiene (HCBD) is summarized below! A full description of the health effects and the
dose-response information for threshold and non-threshold effects associated with exposure to
naphthalene are presented in Chapters 7 and 8 of the Health Effects Support Document for
Hexachlorobutadiene (USEPA, 2001b).
4.1 Hazard Characterization and Mode of Action Implications
While available lexicological data indicate that HCBD has the potential to cause adverse health
effects in animals, data on human health effects are limited to a few studies of occupational exposure to
HCBD. These data, collected from inhalation exposure, are often confounded by simultaneous exposures
to other chemicals in an occupational setting. Such equivocal data has made it difficult to establish a
relationship between HCBD exposure and toxic/cytogenetic effects in human.
Animals studies demonstrate selective effects of HCBD on the proximal tubule of the kidney. For
example, renal toxicity has been observed in rodents following single acute exposures of 100-200 mg
HCBD/kg and short-term exposures to 3 mg/kg-day and above. Furthermore, subchronic and chronic
studies on rodents have indicated renal damage at a lowest observed adverse effect level (LOAEL) of 2
mg/kg-day. Progressive effects over time from HCBD exposure include kidney weight changes,
increased urinary excretion of coproporphyrin, and increased renal tubular epithelial hyperplasia.
Developmental effects and neurotoxicity have been observed in studies that used higher HCBD doses
than in the previous studies (Harleman and Seinen, 1979; Badaeva et al., 1985). In addition, pups with
lower birth weights and reduced growth have been reported after administering maternal dosages of 8.1-
15 mg/kg-day to rats (Harleman and Seinen, 1979).
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Preliminary Regulatory Determination Support Document far Hexachlorobutadiene November, 2001
Results from mutagenicity studies with HCBD are ambiguous. Some studies have shown HCBD and
its degradates to be mutagenic in specific chemical environments (Vamvakas et al., 1988; Reichert et al.5
1984). HCBD metabolites have been shown to bind to mitochondria! DNA in vivo in mice, and induce '
DNA repair in cultured porcine kidney cell, suggesting genotoxic potential (Schrenk and Dekant, 1989*
Vamvakas et al., 1989). However, no human studies of HCBD carcinogeniciry have been reported and
only one animal study has been performed (Kociba et al., 1977). In mis study, neoplastic changes were
observed in the liver at the highest dose (which exceeded the maximum tolerated dose [MID]). The
dosage necessary to cause these significant adverse effects suggests that tumor formation may be
secondary to cytotoxicity.
In order to evaluate toe hazard posed by HCBD, the threat to humans must be extrapolated from data
on rodents, raising the issue of applicability. Nephrotoxicity caused by HCBD is dependent on a
multistep bioactivation mechanism involving both kidney and liver enzymes. In vitro studies with human
renal cytosol and cultured human proximal tubule cells suggest that humans have the potential to form
HCBD-glntathione conjugates and to metabolize HCBD cysteine conjugates to toxic metabolites
However, the rate of metabolism, particularly for the reaction catalyzed by p-lyase, appears to be much
lower for humans than for rodents (Lock, 1994; Lash et al., 1990).
4.2 Dose-Response Characterization and Implications in Risk Assessment
Noncancer effects
Renal effects in rodents, resulting from short-term exposure to HCBD, appear to have LOAELs of
5-20 mg/kg-day, depending on the following factors: rodent species/strain, length of exposure, and
method of administration. For female Sprague-Dawley rats administered HCBD for 3 weeks, no effect
was observed after 3 mg/kg-day oral dose, reduced body weight gain and food consumption after a 10
mg/kg-day dose, and renal tubular degeneration, necrosis and regeneration were observed at a 30 mg/kg-
day dose (Kociba et al., 19717; Schwetz et al., 1977). Male Sprague-Dawley rats exposed to HCBD via
ingestion for 3 weeks identified a LOAEL of 20 mg/kg-day and a no observed adverse effect level
(NOAEL) of 0.2 mg/kg-day for kidney damage and increased relative kidney weight (Stott et al 1981)
In a four-week oral study with Wistar rats, a LOAEL of 8 mg/kg-day and a NOAEL of 2.25 mg/kg-day'
were identified for decreased body weight gain and renal tubular effects (Jonker et al, 1993) A 2-week
feeding study in Wistar rats identified a LOAEL of 4.6 mg/kg.*iay (the lowest dose tested) for renal
tubular epithelial cell degeneration (Harleman and Seinen, 1979). Lastly, in a 2-week oral exposure study
on B6C3F, mice, a LOAEL of 3-5 mg/kg-day (the lowest dose tested) was reported for renal tubular
necrosis (NIP, 1991).
In a subchronic 13-week oral exposure study of HCBD inB6C3Fj mice, a NOAEL of 1.5 mg/kg-day
was identified for male mice based on renal tubular cell regeneration (NTP, 1991). In females 1 of 10
mice in the lowest dose group (0.2 mg kg-day) was affected with tubular regeneration. The authors of
this study concluded that insufficient data existed to identify a NOAEL for the female mice (NTP 1991)
Others (USEPA, 1998b; WHO, 1994) have also concluded that this observed effect is not statistically
significant As a result, 0.2 mg/kg-day may be considered close to the NOAEL for renal injury in female
mice. ,
In a lifetime oral exposure study on HCBD (Kociba et al., 1977), a NOAEL of 0.2 mg/kg-day and a
LOAEL of 2 mg/kg-day in rats was identified, based on an increase in renal tubular epithelial cell
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
hyperplasia/regeneration and an altered renal function (increased urinary coproporphyrin excretion). The
significance of this NOAEL value from a chronic study is that it is identical to the value identified from
the 13-week NTP study on female mice (NTP, 1991), suggesting mat female mice may be more sensitive
than rats to HCBD.
The EPA's Reference Dose (RfD) for HCBD is 2 x \tf mg/kg-day (1998b). The RfD is an estimate
of a daily exposure to the human population (including sensitive subgroups) that is likely to be without
appreciable risk of deleterious effects over a lifetime. The RfD is derived from a NOAEL of 0.2 mg/kg-
day for renal tubular epithelial cell hyperplasia/regeneration from the Kociba et al. (1977) and NTP
(1991) studies. A composite uncertainty factor of 1,000 was used in the derivation of the RfD to account
for extrapolation from animals to humans (factor of 10); protection of sensitive subpopulations (factor of
10); use of a NOAEL mat may be closer to a LOAEL (factor of 3); and database deficiency (factor of 3)
due to lack of a 2-generation reproductive study.
Cancer effects
The single lifetime exposure study in rats is also a valuable source of data on tumor formation
(Kociba et al., 1977). Only at the highest dose of 20 mg/kg-day (which exceeded the level at which
significant non-carcinogenic effects were seen, i.e. mortality, renal toxicity, and body, weight depression)
were tumors observed m both sexes. No tumors were observed in the group administered the second
highest dose of 2 mg/kg-day. Also, no definitive shape from the dose-response curve could be
determined from this data set.
Data from Kociba et al. (1977) indicate that the tumor dose response curves are strongly non-linear
. and that renal tumors are only observed at HCBD doses that cause toxicity. HCBD appears to be
carcinogenic only at cytotoxic dose. Under EPA's 1986 Guidelines for Carcinogen Risk Assessment,
HCBD is classified as a Group C, possible human carcinogen (USEPA, 1986). EPA's draft Ambient
Water Quality Criteria for HCBD recommends using a non-linear approach for dose-response
extrapolation, since the non-linear margin of exposure approach may be more appropriate for assessing
the dose-response of HCBD (USEPA, 1998b).
4.3 Relative Source Contribution
Relative source contribution analysis compares the magnitude of exposure expected via drinking
water to the magnitude of exposure from intake of HCBD in other media, such as food, air, and soil. To
perform this analysis, intake of HCBD from drinking water must be estimated. Occurrence data for
HCBD in water and other media are presented in Chapter 3 of this document
The 99th percentile concentration for all samples (i.e., those with detectable and nondetectable levels
of HCBD) from Round 1 and Round 2 PWS sampling is below the MRL. As a convention, a value of
half the MRL is often used as an estimate of the concentration of a contaminant in samples/systems whose
results are less than the MRL. However, for Round 1 and Round 2, States have reported a wide range of
values for the MRLs. Therefore, a single estimate of the MRL for HCBD is unavailable.
The median concentration (0.3 ug/L) for HCBD in samples with detectable levels is used to estimate
intake from drinking water. The exposure estimate for an average individual is determined by
multiplying the drinking water concentration by daily water intake (2 liters/day) and dividing by average
^
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
weight (70 kg Tie tatted exposure to HCBD from drinkin
November, 2001
4.4 Sensitive Populations
ff H^D iS ** ***** Exfeting aepfropatby or age-related kidney
^ to ""^ ** Hsk °f renal **»* m humans> T*«*^ sensitive
e^surenmymcludepeoplewilhpre-existingkidneyorliverclaniage orthe
elderfy. Furthennor^ dthough it is unlikely that human newborns would be acutely exposed to
significant doses of HCBD, acute exposures for young rats and mice have shown to caiL foxicity at
lower doses than for adults (Hook etal., 1983; Locket aL, 1984). uwrancnyw
Calculation of medium-specific exposure ratios indicates that HCBD intake from air is about 14 - 20
foldgreaterthanintakefromwater. As a result, regulation of HCBD in drinking water may not
significantly reduce the risk to adverse effects from HCBD for sensitive populatiW
4.5 Exposure and Risk Information
When average
drinking water are compared with intakes from air, drinking water accounts for a
re atively small proportion of total HCBD intake. Relative intake rates
mtakes from soil are unknown. On the basis of these observations, me impac
concentrations in drinking water on health risk reduction is likely to be small.
^ from *e Water Industry Baseline Handbook
le "" Served ^ Public water ^PP^ «at have
« tl0n' aPProxmately 1-2 million people could be exposed to over one-half
of the health reference level (HRL), based on data from Round 1 sampling, while about 5 millton peopfe
could be exposed at one-half the HRL, based on Round 2 sampling. Based on fee ^7^27
samphng, about 781,000 individuals were exposed to concentrations at or above the HRL BS1
Romd 2 2S51"?* Im ^t^10'000 Persons ««« be exposed at or above the HRL. He
Round 2 based estimate is probably a better estimate of possible exposure since the database is more
recent, and more representative of the cross-section population served by ground water.
4.6 Conclusion
wo^SS^^ **? !S,e!?dence matHCBD may have adverse health effects in animals at
modeiate-to-mgh doses, available data on human subjects are limited and ambiguous Nevertheless
using a conservative health reference level, national exposure data indicate that? Tj^l^l '
will occur at frequencies that are of public health concern. It is therefore unlikely that regulation
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
November, 2001
represents a meaningful opportunity for health risk reduction in persons served by public water systems.
All preliminary CCL regulatory determinatipns and further analysis will be presented in me Federal
Register Notice.
5.0 TECHNOLOGY ASSESSMENT
If a determination has been made to regulate a contaminant, SDWA requires development of
proposed regulations within 2 years of making the decision. It is critical to have suitable monitoring
methods and treatment technologies to support regulation development according to the schedules defined
in the SDWA.
5.1 Analytical Methods •
The availability of analytical methods does not influence EPA's determination of whether or not a
CCL contaminant should be regulated. However, before EPA actually regulates a contaminant and
establishes a Maximum Contaminant Level (MCL), there must be an analytical method suitable for
routine monitoring, therefore, EPA needs to have approved methods available for any CCL regulatory
determination contaminant before it is regulated with an NPDWR. These methods must be suitable for
compliance monitoring and should be cost effective, rapid, and easy to use.
Hexachlorobutadiene is an unregulated contaminant for which monitoring was required under the
Unregulated Contaminant Monitoring Program (USEPA, 1987; 52 FR 25690), It already has well-
documented analytical methods developed specifically for low-level drinking water analyses.
For hexachlorobutadiene, there are two analytical methods available. EPA Method 524.2 is a well
established, and sensitive, purge and trap gas chromatographic mass spectrometry (MS) method with a
detection limit of 0.11 jig/L. EPA Method 502.2, a purge and trap melhod using conventional gas
chromatography detectors (PID and ELCD in series), has a method detection limit (MDL) of 0.06 jig/L.
5.2 Treatment Technology
Treatment technologies also do not .influence the determination of whether or not a contaminant
should be regulated. But before a contaminant can be regulated with an NPDWR, treatment technologies
must be readily available. EPA's Office of Research and Development (ORD) has researched treatment
technologies for all of the organic compounds listed as regulatory determination priorities on the CCL,
including hexachlorobutadiene. The two appropriate technologies reviewed were granular activated
carbon (GAC) and air stripping.
Granular activated carbon treatment removes contaminants via the physical and chemical process of
sorption, by which the contaminants attach to the carbon surface as water passes through the carbon bed.
Activated carbon has a large sorption capacity for many water impurities including synthetic organic
contaminants, taste and odor causing compounds, and some species of mercury (USEPA, 1998a).
Adsorption capacity is typically represented by the Freundlich isotherm constants, with higher Freundlich
K values indicating greater sorption potential.
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
Air stripping involves the continuous contact of air with the water being treated, allowing volatile
dissolved contaminants to transfer from the source water to the air. After contact, the "contaminated air"
is swept from the system, taking the contaminant out of contact with the treated water The driving force
for the water-to-air transfer of the volatile contaminants is the contaminant's concentration gradient
between the water and air. The Henry's Law constant is a commonly used indicator of the tendency of a
contaminant to partition from water to ah-. A larger Henry's constant indicates a greater equilibrium of
the contaminant in the air. Thus, contaminants having larger Henry's constants are more easily removed
by an-stripping.
Predictive computer modeling and specific chemical characteristics were used to determine the
isotherm constants needed to evaluate the two treatment technologies. The rule of thumb used for SDWA
compounds, learned through the development of cost-and-technology documents to support other
drinking water regulations, is that GAC is considered to be cost-effective if the contaminant has a
Freundhch (K) value above 200 (Speth and Adams, 1993). For air snipping, a compound with a Henry's
constant above dibromochloropropane (0.005) or ethylene dibromide (0.037) is considered strippable at a
reasonable cost
Hexachlorobutadiene has a predicted Freundlich pC) value of 154,000 and a predicted Henry's Law
stant of 1.1. Therefore, both GAC and air stripping are applicable treatment technologies.
constant of 1
6.0 SUMMARY AND CONCLUSIONS - DETERMINATION OUTCOME
Three statutory criteria are used to guide me preliminary determination of whether regulation of a
CCL contaminant is warranted; 1) the contaminant may adversely affect the health of persons- 2) the
contaminant is known or is likely to occur hi public water systems with a frequency, and at levels of
pubhc health concern; and 3) regulation of the contaminant presents a meaningful opportunity for health
nsk reduction for persons served by public water systems. As required by SDWA, a decision to regulate
a contaminant commits the EPA to propose a Maximum Contaminant Level Goal (MCLG) and
promulgate a National Primary Drinking Water Regulation (NPDWR) for the contaminant. A decision
not to regulate a contaminant is considered a final Agency action and is subject to judicial review The
Agency can choose to publish a Health Advisory (a nonregulatory action) or other guidance for any
contaminant on the CCL that does not meet the criteria for regulation.
While available toxicological data indicate that HCBD has the potential to cause adverse health
effects in animals, data on human health effects are limited to a few studies of occupational exposure to
HCBD. Data collected from inhalation exposure are often confounded by simultaneous exposures to
other chemicals in an occupational setting. Such equivocal data has made it difficult establish a
relationship between HCBD exposure and toxic/cytogenetic effects in human.
Evidence indicates that renal damage may be caused by acute, subchronic, or chronic HCBD oral
exposures in rodents. A few animal studies have also reported liver effects and neurotoxicily Review of
animal dose-response data suggests that subchronic and chronic LOAEL values for HCBD toxicity are
generally at 2 mg/kg-day and above. The EPA has classified HCBD as a Group C, possible human
carcinogen (USEPA, 1986) and set the reference dose for HCBD at 2 x w4 mg/kg-day (1998a)
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
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HCBD in the United States is generated as a waste by-product from the chlorination of hydrocarbons.
Monitoring data indicate that HCBD is infrequently detected in public water supplies, however, when it is
detected, HCBD rarely exceeds the HRL or a value of one-half the HRL. The physiochemical properties
of the contaminant and the available data for environmental fate indicate that HCBD in surface water is
likely to be rapidly degraded by biotic and abiotic process, although it has the potential for
bioaccumulation. ,
USGS NAWQA studies to date have not reported detections of HCBD in ambient water, although
HCBD has been reported through the Toxic Release Inventory. The contaminant has also been detected
at a very low percentage of ATSDR HazDat and CERCLA MPL sites. Detection of HCBD in PWS
samples collected under SDWA indicate low occurrence estimates for Round 1 and Round 2 monitoring,
with only 0.13% and 0.05%, respectively, of all samples showing detections. Significantly, the values for
the 99th percentile and median concentrations of all samples are less than the Minimum Reporting Level.
For Round 1 samples with detections, the median concentration is 0.25 ug/L and the 99* percentile
concentration is 10 ug/L. Median and 99th percentile concentrations for Round 2 detections are 0.30 ug/L
and 1.5 ug/L, respectively. Systems with detections only constitute 0.4% of Round 1 systems and 0.2%
for Round 2. National estimates for the population served by PWSs with detections are also low,
especially for detections greater than the Health Reference Level of 0.9 ug/L. For both rounds, the
estimates are less than 0.5% of the national PWS population.
Approximately 2-5 million people are served by systems with detections of HCBD. When average
daily intakes from drinking water are compared with intakes from air, drinking water accounts for a
relatively small proportion of total HCBD intake. Relative intake rates from food may be higher, while
intakes from soil are unknown.
EPA considers exposure to both the general population and sensitive populations, including the fetus,
infant, and children, in making its regulatory determination. Existing nephropathy or age-related kidney
degeneration has been observed to increase the risk of renal injury hi humans. Therefore, sensitive
populations for HCBD exposure may include people with pre-existing kidney or liver damage, or the
elderly. An extra factor often is included in the health reference level to add protection for sensitive
subpopulations.
In conclusion, while there is evidence that HCBD is capable of causing adverse health effects hi
humans, it is unlikely to occur with a frequency, or at levels, of public health concern. Monitoring data
indicate that hexachlorobutadiene is infrequently detected hi public water supplies; when HCBD is
detected, it very rarely exceeds the HRL or a value of one-half the HRL. Therefore regulation of
hexachlorobutadiene is unlikely to represent a meaningful opportunity for health risk reduction. All
preliminary CCL regulatory determinations and further analysis will be presented in the Federal Register
Notice.
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References
Agency for Toxic Substances and Disease Registry (ATSDR). 1994. lexicological Profile for
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene November, 2001
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
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Appendix A: Abbreviations and Acronyms
ACGIH -American Conference of Governmental Industrial Hygienists
ATSDR -Agency for Toxic Substances and Disease Registry
CAS - Chemical Abstract Service
CCL - Contaminant Candidate List
CERCLA - "Comprehensive Environmental Response, Compensation & Liability Act
CMR - Chemical Monitoring Reform
CWS - community water system
DBCP - dibromochloropropane
ELCD - electrolytic conductivity detector
EPA - Environmental Protection Agency
EPCRA -Emergency Planning and Community Righfr-to-Know Act
FR - federal register
GAC - granular activated carbon (treatment technology for organic compounds)
GC - gas chromatography (a laboratory method)
g/mol -grams per mole
GW -ground water
HA - Health Advisory
HAL - Health Advisory level
HCBD - hexachlorobutadiene
HRL -Health Reference Level
IOC - inorganic compound
IRIS -Integrated Risk Information System'
LOAEL - lowest observed adverse effect level
MCL - maximum contaminant level
MCLG - maximum contaminant level goal
MDL - method detection limit
~~~MR"C' - minimum reporting level
MS - mass spectrometry (a laboratory method)
MTD - maximum tolerated dose
NAWQA - National Water Quality Assessment Program
NCOD - National Drinking Water Contaminant Occurrence Database
NDWAC - National Drinking Water Advisory Council
NIOSH - National Institute for Occupational Safety and Health
NIRS - National Inorganic and Radionuclide Survey
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Preliminary Regulatory Determination Support Document for Hexachlorobutadiene
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Appendix A: Abbreviations and Acronyms
ACGIH - American Conference of Governmental Industrial Hygienists
ATSDR - Agency for Toxic Substances and Disease Registry
CAS - Chemical Abstract Service
CCL - Contaminant Candidate List
CERCLA - Comprehensive Environmental Response, Compensation & Liability Act
CMR - Chemical Monitoring Reform
CWS - community water system
DBCP - dibromochloropropane
ELCD - electrolytic conductivity detector
EPA - Environmental Protection Agency
EPCRA - Emergency Planning and Community Right-to-Know Act
FR - federal register
GAC - granular activated carbon (treatment technology for organic compounds)
GC - gas chromatography (a laboratory method)
g/mol - grams per mole
GW - ground water
HA - Health Advisory
HAL -Health Advisory level
HCBD - hexachlorobutadiene
HRL - Health Reference Level
IOC - inorganic compound
IRIS - Integrated Risk Information System
LOAEL - lowest observed adverse effect level
MCL - maximum contaminant level
MCLG - maximum contaminant level goal
MDL - method detection limit
mg/L - milligrams per liter
MRL - minimum reporting level
MS - mass spectrometry (a laboratory method)
MTD - maximum tolerated dose
NAWQA -National Water Quality Assessment Program
NCOD - National Drinking Water Contaminant Occurrence Database
NDWAC -National Drinking Water Advisory Council
NIOSH - National Institute for Occupational Safety and Health
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NIRS
NOAEL
NPDWR
NPL
NPS
NTNCWS
OGWDW
ORD
PGWD
pro
ppm
PWS
RCRA
R£D
SARA Title HI
SDWA
SDWIS
SDWIS/FED
SOC
SW
TRI
UCM
UCMR
URCIS
USEPA
USGS
VOC
>MCL
>MRL
- National Inorganic and Radionuclide Survey
- no-observed adverse effect level
- National Primary Drinking Water Regulation
- National Priorities List
- National Pesticide Survey
- non-transient non-community water system
- Office of Ground Water and Drinking Water
- Office of Research and Development
- Pesticides in Ground Water Database
- photoionization detector
-part per million
- public water system
- Resource Conservation and Recovery Act
-Reference Dose
- Superfund Amendments and Reauthorization Act
- Safe Drinking Water. Act
- Safe Drinking Water Information System
- Federal Safe Drinking Water Information System
- synthetic organic compound
- surface water
- Toxic Release Inventory
- Unregulated Contaminant Monitoring
- Unregulated Contaminant Monitoring Regulation/Rule
- Unregulated Contaminant Monitoring Information System
- United States Environmental Protection Agency
- United States Geological Survey
- volatile organic compound
- micrograms per liter
- micrograms per kilogram
- percentage of systems with exceedances
- percentage of systems with detections
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