EPA/OPPT/CEB
INTERNAL CEB INTERIM DRAFT - Do not quote or cite
Revised May 2012
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APPROACHES FOR ASSESSING AND CONTROLLING WORKPLACE
RELEASES AND EXPOSURES TO NEW AND EXISTING NANOMATERIALS
Chemical Engineering Branch (CEB)
Economics, Exposure and Technology Division
Office of Pollution Prevention and Toxics
Environmental Protection Agency
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PURPOSE
This draft document revises and updates the previous approaches recommended by the Chemical
Engineering Branch (CEB) of EPA's Office of Pollution Prevention and Toxics (OPPT) in its
draft document dated June 2006, for assessing, monitoring, and controlling releases and
exposures to new and existing nanomaterials1 in the workplace. (See Appendix A for
information on the definitions and descriptions of nanomaterials.)
The document focuses primarily on CEB's methodology for evaluating Pre-Manufacture Notice
(PMN) nanomaterials within OPPT's New Chemicals Program (NCP). Because of the swiftly
changing and challenging nature of nanotechnology, this document represents interim
approaches that are based on the best available information to date in the specific areas that it
addresses.
The document addresses:
I. Release and Exposure Assessment.
II. Inhalation Monitoring.
III. Engineering Controls
IV. Personal Protective Equipment (PPE).
The Appendices at the end of this document provide more details for specific topic areas and
summarize some issues related to workplace release and exposure assessments for nanomaterials.
Some special considerations for nanomaterials, including toxicity, routes of exposure, exposure
metrics, and factors affecting exposure are provided in Appendix B.
INTRODUCTION
In the U.S., interim approaches and recommendations for release and exposure assessment as
well as control approaches for minimizing workplace exposures to nanomaterials have been
developed primarily by the National Institute for Occupational Safety and Health (NIOSH).
Several federal agencies with a range of research and regulatory roles and responsibilities are
also involved in comprehensive interagency nanotechnology research and development programs
like the National Nanotechnology Initiative (NNI). To develop its own internal policies and
approaches for nanomaterials, CEB relies, for the most part, on published guidance from NIOSH
on nanomaterial assessment and control issues. CEB also incorporates protective requirements
from relevant OSHA standards (e.g., respiratory protection in accordance with 29 CFR
1910.134) as well as testing information from standard setting organizations like the ASTM.
1 In accordance with the convention used by the National Institute for Occupational Safety and Health (NIOSH) in
some of its recent guidance, the term "nanomaterials" or "nanoparticles" is used in this document to identify
intentionally produced or engineered nanomaterials/nanoparticles and to distinguish between engineered
(nanoparticle) and incidental (ultrafine) nanoscale particles; the latter are typically byproducts of processes such as
combustion and vaporization. However, this does not imply differences in the properties of these particles as related
to hazard assessment, measurement, or control of exposures.
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I. Release and Exposure Assessment
CEB's methods, both qualitative and quantitative, for assessing potential workplace releases of
and exposure to nanomaterials are currently similar to those used for bulk materials. These
estimation approaches have been used for a number of reasons, including limited understanding
of the toxicity, worker exposure levels, and associated measurement techniques for
nanomaterials. Worker exposure evaluations of nanomaterials to date have been solely for Toxic
Substances Control Act (TSCA) section 5 purposes, in which EPA employs screening level
approaches for estimating worker exposures to new chemical substances for which data are
rarely available. CEB applies its standard methods for bulk-sized materials contained in
ChemSTEER, a screening tool, for estimating mass-based releases of and exposures to
nanomaterials. Information on EPA's approaches and the primary worker exposure estimation
tool (Chemical Screening Tool for Exposures and Environmental Releases, ChemSTEER) is
available on EPA's public website at http://www.epa.gov/oppt/exposure/ and
http://www.epa.gov/oppt/exposure/pubs/chemsteer.htm.
One limitation of the use of ChemSTEER models is that they generally produce conservative,
and in some instances bounding estimates of occupational exposure and environmental releases.
At this time, CEB only generates mass-based values for assessment of release (kg/site-day or
kg/yr) and exposure (mg/day) to nanomaterials. Current EPA risk evaluations by RAD use mass-
based concentrations for inhalation estimates, where the units used are micrograms or milligrams
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per cubic meter (|ig/m or mg/m ) as an 8-hour time-weighted average (TWA).
Workplace Releases
Although CEB currently applies its standard methods for estimating mass-based releases of bulk-
sized materials to nanomaterials, it may choose to deviate from them if submitters provide good
quality estimates for site-specific releases of nanomaterials. Sometimes CEB does not assess
releases for non-nano materials, either because the release is small (e.g., sampling waste, dust
emission from unloading bags, etc.) and is expected to make a relatively insignificant
contribution to total releases, and/ or because CEB has no estimation method for a release, and/or
because the release is expected to be below a NCP "trigger" amount (i.e.., < 5,000 kg/site-yr to
land) for which release assessment is not needed for risk assessment. The decision not to assess
some releases has been reconsidered for new chemical cases involving nanomaterials, and it is
CEB's intent to estimate all releases in nano cases (or alternately, to make note of a release that
cannot be quantified).
Workplace Exposures
Workers are likely to have earlier and higher exposures than the general population/consumers
during activities involving the manufacturing, processing, and use of nanomaterials. (See
Appendix C for processes and operations during which worker exposure to nanoparticles can
occur). While dermal absorption and ingestion are potential entry routes for engineered NM, the
inhalation route appears to be the most important route for workplace exposure and has also
received the most attention (Bergamaschi et al. 2006; Donaldson et al. 2006). (See Appendix B
for further information on routes of exposures for nanomaterials.)
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EPA prefers to use the following hierarchy to obtain/generate data on worker exposures to
chemical substances, which also applies to nanomaterials:
1. Personal monitoring data for exposure to the chemical of interest in the workplace of
interest;
2. Personal monitoring data for the chemical of interest in a workplace situation that is
similar to the workplace of interest (surrogate workplace situation) OR personal
monitoring data for a chemical that is similar to the chemical of interest in the workplace
of interest (surrogate chemical);
3. Modeled estimates or concentration assumptions based on regulatory limits.
Several hurdles exist currently to obtaining personal monitoring data which can be used for
exposure assessment to all nanomaterials (see discussion under Inhalation Monitoring Methods,
in Section II. Inhalation Monitoring below), including lack of appropriate sampling methods2.
Surrogate data has been used for single-walled carbon nanotube material (SWCNT) from a
laboratory based study by Maynard et al. (2004) that looked at mechanical agitation,
complemented with airborne and dermal exposure while handling unrefined material. Handling
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resulted in very low airborne concentrations (from 0.7-53 |ig/m ), consistent with the tendency
on the SWCNTs to aggregate into larger masses (Maynard et al. 2004). EPA has used the highest
"3
concentration determined (53 |ig/m ) in several new chemical cases as tier 2 surrogate data
where chemical substances and workplace activities have seemed to match well to those
documented in the study.
In most new chemicals cases, the limited amount of applicable literature data leads EPA to
employ standard screening methods for estimating particulate exposures. Several of the primary
screening methods for estimation dust exposures include the tier 2 "Small Volume Solids
Handling Inhalation Model" and tier 3 "OSHA Permissible Exposure Limit (PEL) for
Particulate, Not Otherwise Regulated (PNOR), total and respirable particulate" models. Also,
several primary screening methods for estimation aerosol exposures in "end-use" scenarios (e.g.,
liquid spraying or roll coating mist generation) include the tier 2 "UV Roll Coating Inhalation
Model (non-volatiles)" and tier 2 "Automobile Spray Coating Inhalation Exposure Model (non-
volatile non-polyisocyanates)" models. EPA also uses a suite of standard dermal exposure
models to estimate dermal exposures (in mg/day) to nanomaterials. These inhalation and dermal
models are documented in the ChemSTEER help system.
Key information and data needed to use these models includes including throughput volumes of
materials in kg/day, operating days in days/yr, physical states and concentrations of the
nanomaterial of interest at key stages of handling, worker activities with exposure potential, and
number of workers for each of these activities. This information is requested in the
Premanufacture Notice Form (Form 7710-25).
2
For carbon nanotubes (CNTs) and carbon nanofibers (CNFs), recent NIOSH guidance (NIOSH, 2010)
recommends use of NIOSH method 5040 with appropriate caveats.
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CEB does not typically assess the potential for ingestion. However, it should be noted that
although ingestion is likely to be less significant than the inhalation and dermal exposure routes,
it can occur in industrial settings. A primary route of ingestion is expected to be unintentional
hand to mouth transfer of materials. This occurs with materials other than nanomaterials and it is
therefore reasonable to assume it can occur during handling of materials that contain
nanoparticles (NIOSH 2009).
Some limited workplace monitoring data are available in the literature for carbon nanotubes, and
CEB may examine such 'surrogate' data if the chemicals and workplaces are comparable from an
exposure standpoint (e.g., nanomaterials have comparable physical-chemical properties, are
handled similarly, processes and throughputs are comparable, etc.).
Engineering Report Assessment Logic for Nanomaterials
The engineering report contains assessments of workplace releases and exposures. For each new
chemical case, an Initial Review Engineering Report (IRER) is normally completed prior to the
internal OPPT Focus meeting after completing the assessments outlined in the following logic
steps for release as well as inhalation and dermal exposure:
Basic Release Assessment Logic
Is a release assessment needed per SAT or NCP policy?
If Yes, is there potential for releases of nanomaterials?
If No, then indicate and give rationale in Engineering Report (IRER).
If Yes, make a full list of release sources (including disposal of PPE, samples, dusting to
air, etc.). Can releases from these sources be estimated in mass-based and other metrics*
(e.g., surface area and number of particles) to the media (e.g., air, water, incineration, and
land) requested by SAT or by Nano NCP Decision Logic? (Note: SAT or NCP decision
logic for metrics and media to assess for nano cases will be followed; if not otherwise
specified, CEB assesses mass-based metrics only and all media.)
If No (for a source or metric type), then indicate and explain in IRER (qualitative) either
in the introductory notes to the release summary for the operation or in the basis box of
the mass-based release estimate.
If Yes (for a source and metric type), include estimated releases in mass units and/ or
other metrics* in IRER (quantitative); for other metrics, include the estimate in the basis
box of the mass-based release estimate.
Basic Inhalation Exposure Assessment Logic
Is an inhalation assessment needed per SAT or NCP policy?
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If Yes, is there potential for inhalation of airborne nanomaterials?
If No, then indicate and give rationale in Engineering Report (IRER).
If Yes, can the potential dose rate (PDR) and other metrics (e.g., surface area and number
of particles) requested by SAT or by Nano NCP Decision Logic be estimated? (Note:
SAT or NCP decision logic for metrics to assess for nano cases will be followed; if not
otherwise specified, CEB assesses mass-based metrics only.)
If No (for a metric type), then indicate and explain in IRER (qualitative) either in the
introductory notes to the inhalation summary for the operation or in the basis box of the
mass-based inhalation exposure estimate.
If Yes (for a metric type), include estimated PDR and/ or other metrics* in IRER
(quantitative); for other metrics, include the estimate in the basis box of the mass-based
inhalation exposure estimate.
* Note: Methods for estimating other metrics (e.g., surface area and number of particles)
to include along with PDR do not currently exist. These methods would have to be
developed to have a quantitative option for these metrics.
Currently, RAD has requested the percent of the inhaled particulate in the respirable size range
and the inhalation concentration in mg/m3 of respirable particles be included, and these data
should be included in the Introductory Notes to the Inhalation Summary text box (or in the
estimate in the basis box of the mass-based inhalation exposure PDR estimate). Where particle
size distribution is not known or not well understood, rules of thumb for estimating percent of
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particulates in the respirable size range are to assume all particles up to 5 mg/m TWA (OSHA's
respirable PNOR PEL) may be respirable, and the remainder above 5 mg/m is not respirable.
Also, RAD has requested information on whether the nanomaterial being assessed may exist as
free particles or agglomerates, whether the nanomaterial is bound in a matrix (e.g., resin dust
containing PMN), or both. Such a description should be included in the Introductory Notes to
the Inhalation Summary text box.
Basic Inhalation Exposure Assessment Logic for CNTManufacturing
1. Do worker activities involve 'open-air' handling (e.g., loading/ unloading of containers/
bags)of CNTs at > 54 kg/site-day AND/ OR proximity to unenclosed processes that may
create a potentially significant amount of dust (e.g., cutting, grinding, milling)?
If Yes, use OSHA Total PNOR PEL-Limiting Model to estimate total particulate
exposure, and/ or use OSHA Respirable PNOR PEL-Limiting Model to estimate
respirable particulate exposure.
2. If answer to 1. was No, do worker activities involve 'open-air' manual transfers of
CNTs from one container to another at < 54 kg/site-day?
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If Yes, use EPA/OPPT Small Volume Solids Handling Inhalation Model to estimate
particulate exposure, where up to the entire exposure may be respirable.
3. If answers to 1. and 2. were No, do worker activities involve 'incidental' particulate
exposures from activities such as:
- opening glove box where CNTs were handled to move sealed containers of CNTs
- handling CNTs in a fume hood
- sonication of CNTs in a liquid suspension
- other activities not expected to create a significant amount of dust
If Yes, use highest value ("53 ug/m3") of Maynard et al 2004 estimates3 of CNTs to
estimate particulate exposure, where up to the entire exposure may be respirable.
It is recommended that the Maynard data (53 ug/m3) be used in limited number of "low dust"
activities where we think that some small particulate exposures may occur but have no better
method to estimate exposures during the activities. Caution is required in applying the limit of
53 ug/m3 as the upper limit of exposure in all cases that fit the logic above for application of the
Maynard et al 2004 estimate because the exposure potential would be process and production
volume dependant as well as activity specific.4 Also, it cannot be assumed that a laboratory-
based method of aerosol generation, as used in by Maynard et al. provides a definitive
characterization of workplace-related processes.
Some limited data from the most recent NIOSH draft publication on CNTs and CNFs5 seems to
indicate that higher levels of worker exposure are possible besides the ones estimated by
Maynard et al in 2004 during certain settings or activities. CEB in the process of compiling data
from these studies and associating estimated worker exposure concentrations with specific
production processes or activities. This exercise is aimed at obtaining information from more
recent studies than the 2004 Maynard et al. study to evaluate if CEB needs to adjust its decision
logic to better reflect current understanding of worker exposure levels during CNT/CNF
manufacturing, handling, and other associated activities.
3
Maynard et al studied exposure to carbon nanotube material during handling of SWCNTs during two SWCNT
production processes - laser ablation and HiPCO at 4 facilities. About 30 min/ sample (events recorded during
period). Fe and Ni were used as surrogates to estimate CNT concentrations, assuming same combined Fe and Ni
catalyst fraction (based on 30% Fe catalyst in a HiPCO run immediately prior to one of the monitored activities) and
expectation of essentially no variation in catalyst (actual expected variation of within +/- 5% for either production
runs or mfg techniques). CNT concentrations estimated are TWA over sample period. Article contains no info on
CNT throughputs or specific amounts of CNTs handled.
4 Although the metal content of CNTs in the Maynard study were believed to be quite consistent (within +/- 5% ~
see footnote above), it is not known whether the same range could potentially apply in other workplaces where a
similar extrapolation from metal level to CNT level is used for assessing exposure levels because the amount of Fe
and Ni, including other metal content like Co, associated with CNTs varies considerably. Per Maynard et al., "Both
the laser ablation material and the HiPCO raw products can contain up to 30% metal catalyst by mass." Also, the
2004 Maynard et al. study focused on harvesting of the product and reactor cleaning and down-stream use activities,
e.g. agitation were only monitored for research scale activities.
5 NIOSH, 2010. Occupational Exposure to Carbon Nanotubes and Nanofibers. Current Intelligence Bulletin
(Draft). November 2010.
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If particle size data for the operation is available, we may need to consider deviations from the
heuristics. For example, if representative samples of workplace air show a complete absence of
particles below 10 um, then respirable inhalation exposures are negligible. Also, it seems that
we could extrapolate SWCNT data to apply to all CNT manufacturing and possibly even CNF
(carbon nanofiber) manufacturing unless other indicators arise to suggest that such extrapolation
is invalid or not advisable.
[Placeholder - additional data/summary results to be added for CNT/CNF exposure assessment
using activity-specific surrogate exposure values]
Basic Dermal Exposure Assessment Logic
Is a dermal assessment needed per SAT or NCP policy?
If Yes, is there potential for dermal exposure to nanomaterials?
If No, then indicate and give rationale in Engineering Report (IRER).
If Yes, can the potential dose rate (PDR) and other metrics* (e.g., surface area and
number of particles) requested by SAT or by Nano NCP Decision Logic be estimated?
(Note: SAT or NCP decision logic for metrics to assess for nano cases will be followed;
if not otherwise specified, CEB assesses mass-based metrics only.)
If No (for a metric type), then indicate and explain in IRER (qualitative) either in the
introductory notes to the dermal summary for the operation or in the basis box of the
mass-based dermal exposure estimate.
If Yes (for a metric type), include estimated PDR and/ or other metrics* in IRER
(quantitative); for other metrics, include the estimate in the basis box of the mass-based
dermal exposure estimate.
* Note: Methods for estimating other metrics (e.g., surface area and number of particles)
to include along with PDR do not currently exist. These methods would have to be
developed to have a quantitative option for these metrics.
Additional Information EPA Could Request From Submitters
EPA can request some additional information, generally during the Standard Review process, to
supplement the information requested in the PMN form and instructions for New Chemicals
submissions. This is done when the additional information is necessary for estimations of
releases and exposures to nanomaterials and/or to understand and characterize controls affecting
releases and exposures. The evaluation of the information would be noted in the Standard
Review Engineering Report (SRER) in the Notes and Key Assumptions section of the report. If
new information is requested but not received or not relevant and no other factors impact the
original release and exposure assessments, the original IRER is amended to add the contact
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report in which the request was made and a notation is made in the Notes and Key Assumptions
section of the report indicating non-receipt or non-relevancy.
Once a case has entered the NCP Standard Review process, some additional information requests
could include some or all of the following information:
• Provide a rationale for selecting the protective equipment or engineering controls and
note any testing or data (and methods used to generate the data) that were used in making
the selection and may help to indicate the effectiveness of the protective equipment or
engineering controls.6
• Provide information regarding the disposal of used protective equipment (e.g., gloves,
respirator filter cartridges) that may have contacted the nanoscale material. Note any
procedures or other equipment intended to mitigate exposures to the nanoscale material.
• Provide a summary of any personal or area monitoring data (in mass concentrations,
surface area per mass, number of particles, etc.) or associated metrics such as average
particle weight and average particle size for the nanoscale material, including the
measurement method(s) used to generate the data; provide a copy of the full study
containing the data as an appendix. Briefly describe worker training and hazard
communication (MSDS, other) specific to the nanoscale material.
• Provide a rationale for selecting the controls, and include a summary of information such
as data and methods of waste treatment efficiency studies and associated metrics such as
average particle weight and average particle size for the nanoscale material; provide a
n
copy of the full study containing the data as an appendix.
CEB's Current Data Needs for Nanomaterials
Although CEB obtains information and data from PMN forms for a number of key aspects (e.g.,
particle characteristics, production volume, number of sites) that are essential for assessing
releases and exposures to nanomaterials, several outstanding data needs (See Appendix D)
related to releases, treatment, occupational exposures, engineering controls, personal protective
equipment (PPE), and occupational exposure limits (OELs) still need to be addressed for more
accurate estimation of releases and workplace exposure.
CEB is working with other EETD branches to develop a Strategic Plan to document the data
gaps and needs and to evaluate how existing tools and programs like PMNs, Test Rules, OECD
WPMN, ORD Research etc. can be used to address the data needs.
6 For protective equipment and engineering controls included in Part II, Section A.2., column 3 and in Part II,
Section B.2., column 6 of the PMN form.
7 For control technologies included in Part II, Section A.2., column 5a and in Part II, Section B.2., column 12 of the
PMN form.
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II. Inhalation Monitoring
When potential worker inhalation exposures are uncertain but are estimated to be above a
"3
threshold of concern (in mg/m ) specified by RAD or CCD, inhalation monitoring may help to
reduce uncertainty. In general, PMN submitters subject to a §5(e) Consent Order (or persons
subject to a section 5 Significant New Use Rule (SNUR)) have the option to conduct monitoring
after manufacture of the PMN substance has commenced and to make a case for
removal/adjustment of the PPE requirements based on how site monitoring results compare to
the New Chemical Exposure Limits (NCELs) derived by OPPT.
Inhalation Monitoring Methods
There are currently no national or international consensus standards on measurement techniques
for nanomaterials in the workplace. NIOSH researchers have developed and used a field
assessment strategy by using the Nanoparticle Emission Assessment Technique (NEAT) for
determining exposures to engineered nanoparticles that could be used for the evaluation of
occupational exposures (Methner, et. al. 2007; Methner, 2008) NEAT allows a semiquantitative
evaluation of processes and tasks in the workplace where releases of engineered nanoparticles
may occur. NIOSH researchers use several sampling approaches simultaneously with the goal of
obtaining key physicochemical particle metrics: number concentration, qualitative size, shape,
degree of agglomeration, and mass concentration of elemental constituents of interest. This
technique is available in an Appendix titled "Nanoparticle Emission Assessment Technique for
Identificationof Sources and Releases of Engineered Nanomaterials" in a recent NIOSH
guidance document (NIOSH, 2009; at: http://www.cdc.gov/niosh/docs/2009-125/pdfs/20Q9-
125.pdf).
Although the NEAT technique presents a framework for semi-quantitative estimation of worker
exposure to NPs, communication with a NIOSH industrial hygienist and team leader for NIOSH
site visits indicates that the state of instrumentation in terms of their limitations, lack of validated
sampling and analytical methods, inability to separate dust/water droplets (as in sonication) from
nanomaterials, problems in interpretation of data, as well as availability of consultants who know
how/what has to be measured, are all deterrents in asking for monitoring data for nanomaterials
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from submitters and developing guidelines for such monitoring. However, use of NIOSH
sampling method 5040, with some associated limitations and caveats, has been recommended by
NIOSH for estimating personal exposure of workers to CNTs and CNFs in the more recent draft
guidance in the form of a Current Intelligence Bulletin9 that NIOSH released in November 2010.
CEB is evaluating the 2009 NIOSH guidance and the 2010 NIOSH draft CIB (NIOSH, 2010)., to
determine whether monitoring protocols outlined by NIOSH can be used by the New Chemicals
Program to direct submitters to perform inhalation monitoring to demonstrate lower workplace
exposure levels than those estimated by CEB.
8 Phone conversation with Mark Methner, PhD, CIH, of NIOSH on March 3, 2010.
9 NIOSH, 2010. Occupational Exposure to Carbon Nanotubes and Nanofibers. Current Intelligence Bulletin
(Draft). November 2010.
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Inhalation Exposure Monitoring Request Logic
The current "standard" decision logic that includes mass-based criteria is shown in the
engineering report (IRER), and this logic is completed for each workplace inhalation exposure
assessed.
Currently, CEB has no other criteria for nano cases beyond those in the standard decision logic.
If it is determined in the future that other criteria are warranted for nano cases, they will be added
to the logic.
The initial review engineering report (IRER) containing the release and exposure assessments
completed as noted above for the Focus meeting contains the inhalation exposure monitoring
request logic results.
If the Logic yields a "Yes" for requesting inhalation monitoring AND NCP determines a need to
implement this request in a nano case, the NCP must provide CEB with the metrics (e.g., mass
basis, surface area basis, etc.) needed for the monitoring to be requested.
III. Engineering Controls
In the hierarchy of exposure reduction methods, engineering controls are preferred over personal
protective equipment (PPE). However, any CEB requirement that submitters use engineering
controls for new chemicals, including nanomaterials, has historically been infrequent compared
to the CEB requirement for PPE use to control workplace exposures. When assessing
Premanufacture Notifications (PMNs) for new chemical substances, PPE is often required to
provide an adequate margin of protection to the workers because CEB cannot make a remote
assessment of the presence or effectiveness of engineering controls on existing, or potentially
new work sites, especially for worksites that are not under the submitters control.
For most processes and job tasks, the control of airborne exposure to nanoaerosols can be
accomplished using a wide variety of engineering control techniques similar to those used in
reducing exposure to general aerosols. Engineering control techniques such as source enclosure
(i.e., isolating the generation source from the worker) and local exhaust ventilation systems
should be effective for capturing airborne nanoparticles. Current knowledge indicates that a well-
designed exhaust system with a high-efficiency particulate air (HEPA) filter should effectively
remove nanoparticles (NIOSH, 2009).
While enclosed environments employed for manufacturing and handling nanomaterials can
virtually eliminate potential for exposure during normal operations, one recent study (Tsai et al.,
2010) indicates that NP exposures can occur during some workers activities that involve use of
some dry powdered NMs in various fume hoods. Potential for exposure still exists during
maintenance on equipment used to produce or fabricate nanomaterials, during the cleaning of
dust collection systems used to capture nanoparticles in ventilation systems, and the clean-up of
spills or waste material.
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If worker exposure to nanoparticles remains a concern after instituting measures to control
exposure, the use of respirators and other PPE can further reduce worker exposures.
IV. Personal Protective Equipment (PPE)
Respirators and other PPE may be necessary when engineering and administrative controls do
not adequately prevent exposures. Typically, the use of respirators is required if the workplace
"3
exposure concentration (in mg/m ) generated by ChemSTEER exceeds the New Chemical
Exposure Limit (NCEL) that has been derived for the chemical substance by OPPT.
Currently, there are no specific regulatory occupational exposure limits (OELs) for airborne
exposures to engineered nanoparticles although OELs exist for larger particles of similar
chemical composition. However, there is a NIOSH recommend exposure limit (REL) of 1.5
3 3
mg/m for fine particles and a REL of 0.1 mg/m for ultrafine particles (NIOSH, 2007) for
titanium dioxide and NIOSH has also released a REL of 7 micrograms/m3 for respirable
CNT/CNF in a current intelligence bulletin on which it is seeking comments (NIOSH, 2010). It
should be recognized that exposure limits recommended for non-nanoscale particles may not be
health protective for nanoparticle exposures (e.g., the OSHA Permissible Exposure Limit (PEL) for
graphite may not be a safe exposure limit for carbon nanotubes) (NIOSH, 2009).
Respirators
Preliminary evidence shows that for respirator filtration media there is no deviation from the
classical single-fiber theory for particulates as small as 2.5 nm in diameter. The results obtained
for filter media have been recently confirmed for NIOSH-approved N95 and PI00, and European
certified CE-marked FFP2 and FFP3 filtering facepiece respirators which captured nanoparticles
as small as 4 nm diameter size more efficiently than larger size particles (Rengasamy et al.2008;
Rengasamy et al. 2009). No evidence for the thermal rebound for particles in the 4 nm diameter
was obtained. Nanoparticle leakage through respirator face seal is an important component of
respiratory protection. This issue was addressed by measuring the total inward leakage (TIL) for
nanoparticles and larger size particles at different breathing flow rates and artificial leak sizes
using a manikin (Rengasamy et al. 2011). The results showed that the TIL for 50 nm size
particles was ~2-fold higher than the values for larger size (400 nm) particles at smaller leak
sizes. This indicates that higher concentration of nanoparticles could occur inside the breathing
area of respirators in workplaces where nanoparticles in the most penetrating particle size range
are present when leakage is minimal compared to filter penetration. NIOSH certified respirators
are expected to protect workers from nanoparticle inhalation when properly selected andfit
tested as a part of a complete respiratory protection program (NIOSH, 2009).
For new nanomaterial cases that have no NCEL or similar exposure reference value, when
respirator use is indicated after evaluation of the exposure data, OPPT typically will require in a
§5(e) Consent Order the use of a full facepiece air purifying respirator with PI00 (or
N100/R100) cartridges. For new nanomaterial cases that have a NCEL or similar exposure
reference value, when respirator use is indicated after evaluation of the exposure data, submitters
must use respirators that meet the APF requirements assessed to be suitable by the NCP to
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protect workers. These respirators are selected by CEB from the OPPT Respirator Selection
Logic which is based on the current OSHA APFs, per 29 CFR 1910.134.
Gloves
Gloves may be required to reduce dermal exposure when the engineering assessment indicates
potential for dermal exposure In general, dermal exposures to chemicals during glove use can
occur because of permeation, penetration, and activity-specific conditions. An example of the
activity-specific condition component would be dust from the air around the worker floating in
between the glove and hand. Another example would be solid or liquid material making its way
into gloves in the course of routine activities (e.g., handling material or surfaces contaminated
with material) by the worker.
Although specific guidelines exist for the testing and selection of glove materials for dermal
protection against bulk chemicals, no guidelines are currently available on the selection of
clothing or other apparel (e.g. gloves) for prevention of dermal exposure to nanoaerosols. This is
due in part to minimal data being available on the efficacy of existing protective clothing,
including gloves.
However, some clothing standards like the ASTM standard F1671-03 (ASTM 2003) and ISO
standard 16604 (ISO 2004b) incorporate testing with nanoscale particles and therefore provide
some indication of the effectiveness of protective clothing with regard to nanoparticles. NIOSH
is currently conducting laboratory research on test methods to determine particle penetration
through fabrics used into protective clothing and ensembles (NIOSH, 2009).
Permeation Testing for Gloves
Currently, NCP allows submitters to select gloves but sometimes requires up-front permeation
testing. The current CEB draft criteria require the following types of permeation testing for
nanomaterials:
For any handling steps where the nanomaterial is in particulate form (e.g., powders, crystals,
granules, etc.), or in a suspension with pure water and insoluble in water, gloves must be
comprised of material that successfully passes ASTM F-1671. (Note: EPA may consider ASTM
F-1671 testing to be adequate for some dilute aqueous suspensions on a case-by-case basis.)
For any handling steps where the nanomaterial is part of a carrier liquid/solvent other than the
aqueous suspension noted in the previous paragraph, gloves must be comprised of material that
successfully passes ASTM F-739 (continuous liquid contact method). Gloves must be changed
before the breakthrough time for the carrier liquid (as determined by the ASTM F-739 testing or
by the manufacturer).
Also applicable are general best practices for worker glove use (that would apply to all PMN
cases with glove restrictions):
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-Gloves must be discarded and replaced with such frequency as to ensure that they will reliably
provide an impervious barrier to the chemical substances under normal and expected conditions
of exposure within the work area.
-Damaged or defective gloves must not be used.
-The glove manufacturer's care and maintenance instructions for the gloves must be followed.
LoREx Criteria for PPE Use
Note that the above mentioned requirements for respiratory protection and up-front permeation
testing for gloves have been adapted for LoREx cases as follows:
When evaluating Lorex cases with potential nano-sized components, we consider worker
exposure criteria to be met if there is no potential for inhalation or dermal exposure to the
nanomaterial.
In cases where the potential for inhalation and/or demal exposure exists during specific activities
or handling of the nanomaterial, respiratory and/or dermal protection in accordance with the
following draft criteria is required for worker exposure criteria to be met:
1. For worker activities where there is potential for inhalation of particulate/aerosol of the
notified nanomaterial, the current draft criteria require use of a full facepiece particulate/aerosol
air-purifying respirator with PI00 (or N100/ R100) filter cartridges, at a minimum.
2. For worker activities where there is potential for dermal exposure to the notified nanomaterial,
gloves that meet the current draft criteria, as applicable, must be used:
- For any handling steps where the nanomaterial is in particulate form (e.g., powders, crystals,
granules, etc.), or in a suspension with pure water and insoluble in water, gloves comprised of a
material that successfully passes ASTM F-1671 testing must be used. (Note: EPA may consider
ASTM F-1671 testing to be adequate for some dilute aqueous suspensions on a case-by-case
basis.)
- For any handling steps where the nanomaterial is part of a carrier liquid/solvent other than the
aqueous suspension noted in the previous paragraph, gloves comprised of material that
successfully passes ASTM F-739 testing (continuous liquid contact method) must be used.
Gloves must be changed before the breakthrough time for the carrier liquid (as determined by the
ASTM F-739 testing or by the manufacturer).
Also applicable are general best practices for worker glove use (that would apply to all PMN
cases with glove restrictions):
-Gloves must be discarded and replaced with such frequency as to ensure that they will reliably
provide an impervious barrier to the chemical substances under normal and expected conditions
of exposure within the work area.
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-Damaged or defective gloves must not be used.
-The glove manufacturer's care and maintenance instructions for the gloves must be followed.
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REFERENCES
ASTM Subcommittee F23.40. Standard test method for resistance of materials used in protective
clothing to penetration by blood-borne pathogens using Phi-X174 bacteriophage penetration as a
test system. 2003. West Conshohocken, PA: American Society for Testing and Materials, ASTM
F1671-03.
Bergamaschi E, Bussolati O, Magrini A, Bottini M, Migliore L, Bellucci S, Iavicoli I,
Bergamaschi A. Nanomaterials and lung toxicity: Interactions with airways cells and relevance
for occupational health risk assessment. Int JImmunopathol Pharmacol 2006; 19(4)3-10
Donaldson K, Aitken R, Tran L, Stone V, Duffin R, Forrest G, Alexander A [2006], Carbon
nanotubes: A review of their properties in relation to pulmonary toxicology and workplace
safety. Toxicol Sci 2006; 92: 5-22
ISO [2004b], ISO 16604: 2004: Clothing for protection against contact with blood and body
fluids: determination of resistance of protective clothing materials to penetration by blood-borne
pathogens; test method using Phi-X 174 bacteriophage. Geneva, Switzerland: International
Organization for Standardization.
Maynard AD, Baron PA, Foley M, Shvedova AA, Kisin ER, Castranova V [2004], Exposure to
carbon nanotube material: aerosol release during the handling of unrefined single-walled carbon
nanotube material. J Toxicol Environ Health. 67: 87-107.
Methner MM, Birch ME, Evans DE, Ku BK, Crouch KG, Hoover MD [2007], Mazzulxeli LF,
ed: Case study: Identification and characterization of potential sources of worker exposure to
carbon nanofibers during polymer composite laboratory operations. J Occup Environ Hyg
¥(12):D125-D130.
Methner MM [2008], Engineering case reports: Old L, ed. Effectiveness of local exhaust
ventilation (LEV) in controlling engineered nanomaterial emissions during reactor cleanout
operations. J Occup Environ Hyg 5(6):D63-D69.
NIOSH [2005], Approaches to Safe Nanotechnology - An Information Exchange with NIOSH.
National Institute for Occupational Safety and Health, Centers for Disease Control and
Prevention. October 1, 2005. http://www.cdc.gov/niosh/topics/nanotech/nano exchange.html
NIOSH [2007], Progress Toward Safe Nanotechnology in the Workplace. No. 2007-123,
NIOSH, Cincinatti. http://www.cdc.gov/niosh/docs/2007-123/pdfs/2007-123.pdf.
NIOSH [2009], Approaches to Safe Nanotechnology: Managing the Health and Safety Concerns
Associated with Engineered Nanomaterials. NIOSH Publication No. 2009-125. March 2009.
At: http://www.cdc.gov/niosh/docs/2009-125/pdfs/20Q9-125.pdf
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NIOSH [2010], Occupational Exposure to Carbon Nanotubes and Nanofibers. Current
Intelligence Bulletin (Draft). November 2010
Rengasamy S. King W, EimerB, Shaffer R. [2008], Filtration performance of NIOSH-approved
N95 and PI00 filtering facepiece respirators against 4 to 30 nanometer-size nanoparticles. J
Occup Environ Hyg 5: 556-564, 2008.
Rengasamy S., EimerB, Shaffer R. [2009], Comparison of nanoparticle filtration performance of
NIOSH-approved and CE-marked particulate filtering facepiece respirators. Ann Occup Hyg 53:
117-128.
Rengasamy S. and Eimer B. [2011] Total inward leakage of nanoparticles through filtering
facepiece respirators. Ann Occup Hyg (in press).
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APPENDIX A
NANOMATERIAL DEFINITIONS AND DESCRIPTIONS
NIOSH Definitions and Descriptions (NIOSH, 2009)
Engineered Nanoparticles and Ultrafine Particles
Engineered nanoparticles are intentionally produced, whereas ultrafine particles (often referred
to as incidental nanoparticles) are typically byproducts of processes such as combustion and
vaporization. Engineered nanoparticles are designed with very specific properties or
compositions (e.g., shape, size, surface properties, and chemistry). Incidental nanoparticles are
generated in a relatively uncontrolled manner and are usually physically and chemically
heterogeneous compared with engineered nanoparticles.
The two terms nanoparticle and ultrafine are sometimes used to differentiate between
engineered {nanoparticle) and incidental {ultrafine) nanoscale particles, however, nanoparticle
and ultrafine particle are not rigid definitions.
It is currently unclear whether the use of source-based definitions of nanoparticles and ultrafine
particles is justified from a safety and health perspective. This is particularly the case where data
on non-engineered, nanometer-diameter particles are of direct relevance to the impact of
engineered particles. Also, the use of the term nanoparticle or ultrafine does not necessarily
imply specific differences in the properties of these particles as related to hazard assessment,
measurement, or control of exposures. For example, since the term ultrafine has been in ex-
istence longer, some intentionally produced particles with primary particle sizes in the nanosize
range (e.g., TiO:) are often called ultrafine in the literature.
Agglomerate
An agglomerate is a group of nanoparticles held together by relatively weak forces, including
van der Waals forces, electrostatic forces, and surface tension (ISO, 2006).
Aggregate
An aggregate is a heterogeneous particle in which the various components are held together by
relatively strong forces, and thus not easily broken apart (ISO, 2006). Aggregated nanoparticles
would be an example of a nanostructured material.
Nanoaerosol
A nanoaerosol is a collection of nanoparticles suspended in a gas. The particles may be present
as discrete nano-objects, or as aggregates or agglomerates of nano-objects. These agglomerates
may have diameters larger than 100 nm. In the case of an aerosol consisting of micrometer-
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diameter particles formed as agglomerates of nano-objects, the definition of nanoaerosol is open
to interpretation. It is generally accepted that if the nanostructure associated with the nano-object
is accessible (through physical, chemical, or biological interactions), then the aerosol may be
considered a nanoaerosol. However, if the nanostructure within individual m i crom eter-di am eter
particles does not directly influence particle behavior (for instance, if the nanoparticles were
inaccessibly embedded in a solid matrix), the aerosol would not be described as a nanoaerosol.
The National Nanotechnology Initiative Definition
The National Nanotechnology Initiative (NNI, 2010) in the United States defines nanomaterials
as follows:
Nanomaterials is a term that includes all nanosized materials, including engineered
nanoparticles, incidental nanoparticles and other nano-objects, like those that exist in nature.
When particles are purposefully manufactured with nanoscale dimensions, we call them
engineered nanoparticles. There are two other ways nanoparticles are formed. Nanoparticles can
occur as a byproduct of combustion, industrial manufacturing, and other human activities; these
are known as incidental nanoparticles. Natural processes, such as sea spray and erosion, can also
create nanoparticles.
Many important functions of living organisms take place at the nanoscale. The human body uses
natural nanoscale materials, such as proteins and other molecules, to control the body's many
systems and processes. A typical protein such as hemoglobin, which carries oxygen through the
bloodstream, is 5 nms in diameter.
American Chemistry Council Definition
The American Chemistry Council—Nanotechnology Panel (ACC, 2007) has proposed a separate
definition for Engineered Nanomaterials. "The ACC Nanotechnology Panel believes that
definitions used to describe Engineered Nanomaterials are important because they will be used to
guide the public when information requests are made by regulators and NGO's. It is desirable
that the definitions be as simple as possible yet not so broad that the collection of meaningless
information is encouraged." For this reason, the ACC has proposed the following definition for
Engineered Nanomaterials:
An Engineered Nanomaterial is any intentionally produced material that has a size in 1, 2, or 3-
dimensions of typically between 1-100 nanometers. It is noted that neither 1 nm nor 100 nm is a
"bright line" and data available for materials outside of this range may be valuable. Buckyballs
are also included even though they have a size <1 nm.
Exclusions:
1. Materials that do not have properties that are novel/unique/new compared to the non-
nanoscale form of a material of the same composition.
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2. Materials that are soluble in water or in biologically relevant solvents. Solubility occurs when
the material is surrounded by solvent at the molecular level. The rate of dissolution is sufficiently
fast that size is not a factor in determining a toxicological endpoint.
3. For those particles that have a particle distribution such that exceeds the 1-100 nm range (e.g.
50-500 nm) if less than 10% of the distribution falls between 1-100 nm it may be considered as
non an Engineered Nanomaterial. The 10% level may be on a mass or surface area basis,
whichever is more inclusive.
4. Micelles and single polymer molecules.
International Organization for Standards (ISO) Definitions
In 2008, the International Organization for Standards published the ISO/TS 27687:
2008 standard, "Nanotechnologies — Terminology and definitions for nano-objects —
Nanoparticle, nanofibre and nanoplate". The standard is intended to facilitate communications
between organizations and individuals in industry and those who interact with them.
The ISO/TS 27687:2008 lists the following unambiguous terms and definitions related to
particles in the field of nanotechnology (ISO, 2008):
A nano-object is defined as material with one, two, or three external dimensions in the size
range from approximately 1 -100 nm. Nano-objects may be suspended in a gas (as a
nanoaerosol), suspended in a liquid (as a colloid or nanohydrosol), or embedded in a matrix (as a
nanocomposite). Nano-objects are commonly incorporated in a larger matrix or substrate
referred to as a nanomaterial.
Subcategories of nano-object are:
(1) nanoplate: a nano-object with one external dimension at the nanoscale;
(2) nanofiber: a nano-object with two external dimensions at the nanoscale with a nanotube
defined as a hollow nanofiber and a nanorod as a solid nanofiber; and
(3) nanoparticle: a nano-object with all three external dimensions at the nanoscale.
Carbon fullerenes represent nano-objects with identical dimensions in all directions (i.e.,
spherical), whereas single-walled carbon nanotubes (SWCNTs) typically form convoluted, fiber-
like nano-objects. Many regular but nonspherical particle morphologies can be engineered at the
nanoscale, including flower- and belt-like structures.
Sources
ACC, 2007. ACC- Nanotechnology Panel. Consideration for a Definition for Engineered
Nanomaterials. March 13, 2007.
ISO, 2008. Workplace atmospheres; ultrafme, nanoparticle and na no-structured aerosols; exposure characterization
and assessment. Geneva, Switzerland: International Standards Organization. Document no. ISO/TC 146/SC 2/VVG1
N324, 32 pages. Cited in: NIOSH, op. cit.
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National Institute for Occupational Safety and Health (NIOSH), 2009. Approaches to Safe
Nanotechnology: Managing the Health and Safety Concerns Associated with Engineered
Nanomaterials. NIOSH Publication No. 2009-125. At: http://www.cdc.gov/niosh/docs/2009-
125/
National Nanotechnology Initiative (NNI), 2010. Frequently Asked Questions (FAQ).
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APPENDIX B
Special Considerations for Nanomaterials:
Toxicity, Exposure Metrics, Routes of Exposure, and
Factors Affecting Worker Exposure
Toxicity and Exposure Metrics
Results of existing studies in animals and humans on exposure and response to ultrafine or other
respirable particles provide a basis for preliminary estimates of the possible adverse health
effects from exposures to similar engineered materials on a nanoscale. Experimental studies in
rodents and cell cultures have shown that the toxicity of ultrafine or nanoparticles is greater than
that of the same mass of larger particles of similar chemical composition [Oberdorster et al.
1992, 1994a, b; Lison et al. 1997; Tran et al. 1999, 2000; Brown et al. 2001; Barlow et al. 2005;
Duffin et al. 2007],
Various physicochemical parameters of nanoparticles (e.g., composition, size, shape, dimension,
surface characteristics, charge, functional groups, crystal structure, solubility, and degree of
agglomeration) appear to affect toxicity. It is not known whether size is the overriding
parameter, though most studies show that size appears to be the major factor in enhancing the
toxicity of engineered nanoparticles compared with the toxicity of larger particles of the same
composition. What exposure metrics (e.g., mass, particle count, particle surface area) are most
relevant to the most important health concerns is still not known.
Existing toxicity information about a given material of larger particle size can provide a baseline
for anticipating the possible adverse health effects that may occur from exposure to a nanoscale
material that has some of the same physicochemical properties (e.g., chemistry, density).
However, predicting the toxicity of an engineered nanomaterial based on its physicochemical
properties may not provide an adequate level of protection. More research is needed on the
influence of particle properties on interactions with biological systems and the potential for
adverse effects.
Carbon Nanotubes
Carbon nanotubes (CNT) are specialized forms or structures of engineered nanomaterials
that have had increasing production and use [Donaldson et al. 2006], Consequently, a
number of toxicologic studies of CNT have been performed in recent years. These studies
have shown that the toxicity of CNT may differ from that of other nanomaterials of
similar chemical composition. For example, single-walled CNTs (SWCNT) have been
shown to produce adverse effects including granulomas in the lungs of mice and rats at
mass doses at which ultrafine carbon black did not produce these adverse effects [Shvedova
et al. 2005; Lam et al. 2004], While both SWCNTs and carbon black are carbon-based,
SWCNTs have a unique, convoluted, fibrous structure and specific surface chemistry that
offers excellent electrical conductive properties. How these characteristics may influence
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How these characteristics may influence toxicity is not known. Carbon nanotubes may
contain metal catalysts as byproducts of their production, which could contribute to their
toxicity, or the CNTs may provide a structure that promotes fibroblast cell growth [Wang
et al. 2008],
Although a number of studies have been conducted on CNT toxicity [Li et al. 2007; Sriram et al
2007; Baron et al. 2008; Shedova et al., 2008; Mercer et al. 2008; Tagaki et al 2008; Poland et al
2008] indicate the need for more], there is a need for additional data on exposures of workers to
CNTs.
Routes of Exposure and Factors Affecting Exposure
Inhalation
The toxicology of the nanomaterial is likely to change with not only material type, but also with
exposure route. Inhalation is the most common route of exposure to airborne particles in the
workplace. Discrete nanoparticles are deposited in the lungs to a greater extent than larger respi-
rable particles [ICRP 1994],
The following factors have been observed to affect the deposition of discrete nano-objects in the
respiratory tract:
• The particle's aerodynamic or thermodynamic diameter (i.e., the particle shape and size)
determines the deposition of nano-objects in the respiratory tract.
• Agglomerates of nano-objects will deposit according to the diameter of the agglomerate,
not constituent nano-objects. Evidence indicates that the degree of agglomeration can
affect the toxicity of inhaled nano-objects [Shvedova et al. 2007],
• Deposition increases with exercise due to increase in breathing rate and change from
nasal to mouth breathing [Jaques and Kim 2000; Daigle et al. 2003] and among persons
with existing lung diseases or conditions (e.g., asthma, emphysema) [Brown et al. 2002],
• Discrete nanoparticles may enter the bloodstream from the lungs and translocate to other
organs [Takenaka et al. 2001; Nemmar et al. 2002; Oberdorster et al. 2002],
Dermal
Nanomaterials could potentially enter the body through the skin during occupational exposure, as
demonstrated by the following studies:
• Tinkle et al. [2003] have shown that particles smaller than 1 //m in diameter may pene-
trate into mechanically flexed skin samples.
• A more recent study reported that nanoparticles with varying physicochemical properties
were able to penetrate the intact skin of pigs [ Ry man - Ra sm u s sen et al. 2006], These
nanoparticles were quantum dots of different size, shape, and surface coatings. They were
reported to penetrate the stratum corenum barrier by passive diffusion and localize within
the epidermal and dermal layers within 8-24 hours. The dosing solutions were 2- to 4-
fold dilutions of quantum dots as commercially supplied and thus represent
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occupationally relevant doses. At this time, it is not fully known whether skin penetration
of nanoparticles would result in adverse effects in animal models.
• Topical application of raw SWCNT to nude mice has been shown to cause dermal irrita-
tion [Murray et al. 2007],
• Studies conducted in vitro using primary or cultured human skin cells have shown that
both SWCNT and multi-walled carbon nanotubes (MWCNT) can enter cells and cause
release of pro-inflammatory cytokines, oxidative stress, and decreased viability
[Monteiro-Riviere et al. 2005; Shvedova et al. 2003],
It remains unclear, however, how these findings may be extrapolated to a potential
occupational risk, given that additional data are not yet available for comparing the cell
model studies with actual conditions of occupational exposure.
Ingestion
Since traditionally ingestion has been found to occur from unintentional hand to mouth transfer
of materials, it is scientifically reasonable to assume that it also could happen during handling of
nanomaterials. Ingestion may also accompany inhalation exposure because particles that are
cleared from the respiratory tract via the mucociliary escalator may be swallowed [ICRP 1994],
Little is known about possible adverse effects from the ingestion of nanomaterials at this time.
References
Barlow PG, Clouter-Baker AC, Donaldson K, Mac- Callum J, Stone V [2005], Carbon black
nanoparticles induce type II epithelial cells to release chemotaxins for alveolar macrophages.
Part Fiber Toxicol 2(14).
Brown DM, Wilson MR, MacNee W, Stone V, Donaldson K [2001], Size-dependent
proinflammatory
effects of ultrafine polystyrene particles: a role for surface area and oxidative stress in the
enhanced activity of ultrafines. Toxicol App Pharmacol 77^(3): 191—199.
Duffin R, Tran L, Brown D, Stone V, Donaldson K [2007], Proinflammogenic effects of
low-toxicity and metal nanoparticles in vivo and in vitro: highlighting the role of particle
surface area and surface reactivity. Inhal Toxicol 7P(10):849-856.
ICRP [1994], Human respiratory tract model for radiological protection. Oxford, England:
Pergamon,Elsevier Science Ltd., International Commission on Radiological Protection,
Publication No. 66.
Jaques PA, Kim CS [2000], Measurement of total lung deposition of inhaled ultrafine
particles in healthy men and women. Inhal Toxicol 72(8):715-731.
Lison D, Lardot C, Huaux F, Zanetti G, Fubini B [1997], Influence of particle surface area on
the toxicity of insoluble manganese dioxide dusts. Arch Toxicol 7/(12):725-729.
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Monteiro-Riviere NA, Nemanich RJ, Inman AO, Wang YY, Riviere JE [2005], Multi-walled
carbon nanotube interactions with human epidermal keratinocytes. Toxicol Lett
755(3):37725384.
Murray AR, Kisin E, Kommineni C, Kagan VE, Castranova V, Shvedova AA [2007], Single-
walled carbon nanotubes induce oxidative stress and inflammation in skin. Toxicologist
96: A1406.
Oberdorster G, Ferin J, Gelein R, Soderholm SC, Finkelstein J [1992], Role of the alveolar
macrophage in lung injury—studies with ultrafine particles. Environ Health Perspect 97:193—
199.
Oberdorster G, Ferin J, Lehnert BE [1994a], Correlation between particle-size, in-vivo
particle persistence, and lung injury. Environ Health Perspect 702(S5): 173-179.
Oberdorster G, Ferin J, Soderholm S, Gelein R, Cox C, Baggs R, Morrow PE [1994b],
Increased pulmonary toxicity of inhaled ultrafine particles: due to lung overload alone? Ann
Occup Hyg 33(Suppl l):295-302.
Ryman-Rasmussen JP, JE Riviere JE, NA Monteiro- Riviere [2006], Penetration of intact
skin by quan- quantum dots with diverse physicochemical properties. Toxicol Sci 91(1): 159—
165.
Shvedova AA, Kisin ER, AR Murray, Gandelsman VZ, Maynard AD, Baron PA, Castranova
V [2003], Exposure to carbon nanotube material: assessment of the biological effects of
nanotube materials using human keratinocyte cells. J Toxicol Environ Health 66(20): 1909-
1926.
Shvedova AA, Sager T, Murray A, Kisin E, Porter DW, Leonard SS, Schwegler-Berry D,
Robinson VA, Castranova V [2007], Critical issues in the evaluation of possible effects
resulting from airborne nanoparticles. In: Monteiro-Riviere N and Tran L (eds).
Nanotechnology: characterization, dosing and health effects. Philadelphia, PA: Informa
Healthcare, pp. 221-232.
Takenaka S, D Karg, C Roth, H Schulz, A Ziesenis, U Heinzmann, P Chramel, Heyder J
[2001], Pulmonary and systemic distribution of inhaled ultrafine silver particles in rats.
Environ Health Persp 709(suppl. 4):547-551.
Tinkle SS, Antonini JM, Rich BA, Robert JR, Salmen R, DePree K, Adkins EJ [2003], Skin
as a route of exposure and sensitization in chronic beryllium disease. Environ Health
Perspect 777(9): 1202-1208.
Tran CL, Cullen RT, Buchanan D, Jones AD, Miller BG, Searl A, Davis JMG, Donaldson K
[1999], Investigation and prediction of pulmonary responses to dust, part II. In:
Investigations into the pulmonary effects of low toxicity dusts. Contract Research Report
216/1999. Suffolk, UK: Health and Safety Executive.
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Appendix C
Processes and Operations with Potential for Occupational Exposure to
Engineered Nanoparticles
Four major processes are employed in synthesizing new nanoparticles (Bergamaschi, 2009):
(i) Gaseous phase condensation processes, which include flame pyrolysis, high-
temperature evaporation and synthesis in a plasma, involving nucleation and
evaporation phenomena (bottom-up approach);
(ii) Synthesis by evaporation and vapour deposition (bottom-up approach);
(iii) Colloid formation by chemical reactions with liquid phase or colloidal solvents,
involving controlled precipitation phenomena (bottom-up approach); and
(iv) Mechanical attrition processes (top-down approach) (for a more complete description
of processes, see: Aitken et al. 2004; National Institute for Occupational Safety and
Health (NIOSH) 2007; Schneider et al. 2007). In recent years, the limits of each
approach, in terms of feature, size and quality that can be achieved, have started to
converge. Now the dimensions that can be controlled by either approach are of a
similar order, and this is leading to exploitation of new hybrid methods of
manufacture.
In all nanoparticle (NP) production processes there is a potential for exposure at both the
synthesis and recovery phase of the process (see Table I below). However, emission scenarios
(i.e., potential releases, which depends on particle properties), should be distinguished from
exposure scenarios (i.e., the potential exposure, which relies on working conditions, exposure
routes, environmental conditions).
According to NIOSH (2007), many workplace factors and operations may increase the potential
for exposure to nano-aerosols:
(i) Working with nanomaterials (NM) in liquid media without adequate protection (e.g.,
gloves) will increase the risk of skin exposure;
(ii) Working with NM in liquid during pouring or mixing operations, or where a high
degree of agitation is involved, will lead to an increase likelihood of inhalable and
respirable droplets being formed;
(iii) Generating nanoparticles in the gas phase in non-enclosed systems will increase the
chances of aerosol release to the workplace;
(iv) Handling nanostructured powders will lead to the possibility of aerosolization;
(v) Maintaining equipment and processes used to produce or fabricate nanomaterials or
the clean-up of spills or waste material will pose a potential for exposure to workers
performing these tasks;
(vi) Cleaning of dust collection systems used to capture nanoparticles can pose a potential
for both skin and inhalation exposure; (vii) machining, sanding, drilling, or other
mechanical disruptions of materials containing nanoparticles can potentially lead to
aerosolization of nanomaterials.
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Table I. Poten
Synthesis process
tial risk of exposure in r
Potential risk of
inhalation
lanoparticle production processes.
Skin contamination
Gas phase flame
pyrolysis, high
temperature evaporation
and plasma synthesis
Direct leakage from
reactor Product recovery
Any further processing
or packaging
Touching surfaces contaminated by
airborne releases, handling of product
during recovery or processing/packing;
cleaning or maintenance of the plant
Vapour deposition
Product recovery,
mechanical removal,
processing, packing
Airborne dry powders; handling of product
during recovery or packaging; cleaning
workplace
Colloidal or liquid
phase
Recovery by spray
drying; Spillage of
suspension followed by
evaporation
Spillage of the product; dried material
handling; recovery, packing; cleaning,
maintenance
Mechanical attrition
grinding, milling and
alloying
Product drying;
suspension spillage
Spillage of the product; dried material
handling; recovery, packing; cleaning,
maintenance
Processes generating NM in the gas phase, or using or producing NM as powders, slurries,
suspensions and solutions pose the greatest risk for releasing NP. Maintenance on production
systems (including cleaning and disposal of materials from dust collection systems) is likely to
result in exposure to NP if it disturbs deposited NM (Aitken et al. 2004; NIOSH 2007). NM-
enabled products, such as nanocomposites and surface coatings, and materials comprised of
nanostructures such as integrated circuits are unlikely to pose a risk of exposure during their
handling and use. However, some of the processes (formulating and applying nanoscale
coatings) used in their production may lead to exposure to NP (Aitken et al. 2004; Schneider et
al. 2007). Workers could also be exposed to ground CNTs used in polymer composites and other
matrices or during cutting, grinding, or polishing of these materials. Given that exposure to
SWCNT and MWCNT causes interstitial fibrosis and pulmonary inflammation, respectively, in
rodent lungs at relatively low mass doses, NIOSH advises minimizing worker exposure to
airborne CNTs (NIOSH, 2009).
As a whole, field surveys have shown that workers from nanotechnology-related industries have
the potential to be exposed to nanoaerosols of engineered materials via inhalation as well as
through skin contamination.
Exposure to NPs in Workplaces - Air monitoring data
Experimental studies that can mimic the exposure processes reveal the formation of larger
agglomerates of NPs after their release. Studies conducted in workplaces confirmed this
assumption, however, the data are still very scarce and not easy to compare due to differences in
the format of reporting the data (Brouwer D. 2009). A further source of complexity derives from
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the observation that in most environments CNT tend to form larger aggregates or ropes that
would lead to the underestimation of their concentration. Moreover, although their toxicity may
be also ascribed to their fiber shape, their diameter is too small to be detected with the optical
methods used to assess the presence of fibers in the environment (Lam et al. 2006).
Since exposure assessment in new NP processes has begun under the uncertainty about
metrology and the lack of internationally recognized occupational standards, few studies have
directly investigated exposure. Very active in field measurements are some Institutions, such as
the German Federal Institute of Occupational Safety and Health (BAuA). For instance, airborne
concentration of Ti02 detected at the bin filling operation, prior to improve the local exhaust
system, revealed that during the normal operation the number concentration were in the order of
3 3
10 /cm and that particles were mostly airborne aggregates/agglomerates, with primary particles
of Ti in the order of 40-50nm, as confirmed by the subsequent TEM analysis on collected
"3
samples. The gravimetric analysis showed low concentrations of Ti02 (0.18mg/m ) in inhalable
dust fraction (0.232 mg/m3); the corresponding figures for the respirable fraction of collected
3 3
dusts were 0.019 mg/m and 0.10 mg/m , respectively. However, during leakage at the same
plant, concentrations up tol50,000p/cm3 may occur (Markus Berges: presentation made at 2nd
Nanotoxicology Conference, Venice 19-21 April 2007). As compared to the Threshold Limit
Values for dusts (10.0 and 3.0mg/m3, respectively) these data reveal very low exposure levels.
Most studies have focused on the production of nanomaterials, either on bench- or pilot scale or
on commercial scale. Many of the activities that were monitored in commercial scale production
were related to the end-phase, i.e. packaging of the product, e.g. Kuhlbusch et al. (2004),
Kuhlbusch and Fissan (2006), Fujitani et al. (2008), and Peters et al. (2009), whereas others were
focused on or included harvesting of the product and reactor cleaning, e.g. Maynard et al. (2004),
Han et al. (2008), Bello et al. (2008), Methner (2008), Demou et al. (2008), and Yeganeh et al.
(2008). Down-stream use activities, e.g. agitation (Maynard et al., 2004), various activities
(Methner et al., 2007), transfer, pouring (Tsai et al., 2008a), and compounding (Tsai et al.,
2008b) were only monitored for research scale activities.
Recently, results of some experimental studies focused on the release of nanoparticles due to
treatment of 'end-products' were published. Bello et al. (2009) focused in their study on the
release of nanoparticles during machining (cutting) of CNT composites. Vorbau et al. (2009)
quantified the release rate of particles smaller than 100 nm during an abrasion test of a surface
coated with a nanoparticles (ZnO) containing coating.
In general, in studies, nanomaterial-related activities could be distinguished from periods with no
activities or from background concentration for particle number concentration and mass
concentration (if considered). Size distributions and possible influences by nanomaterial-related
activities are less unambiguous to interpret. In most cases bimodal distributions were reported,
however the modes varied substantially. In some case a mode of the size distribution felt into the
nano-sizes (Fujitani et al., 2008; Tsai et al., 2008b), however the authors also reported possible
other sources, i.e. a vacuum cleaner and release of polymer fumes, respectively. An enhanced
concentration of particles <100nm is most often associated with other sources, e.g. combustion,
vacuum cleaning, oil mist or welding/grinding, whereas particle characterization confirmed that
larger nanomaterial agglomerates or aggregates were present in the air rather than distinct small
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particles. For carbon nanotubes (CNTs) Han et al., 2008 reported the release of respirable tubes
supported by identification of high aspect ratio fibers during off-line analysis (Brouwer D, 2009).
Activities with the end-product during production, e.g. harvesting/ bagging, reactor cleaning, and
down-steam use, bag dumping, pouring or transfer, might be mimicked by the dust generation
during dustiness testing of nanopowders, with modes of about 200-300nm and 2000-3000 nm.
Most field studies showed bimodal-size distributions, with often size modes around 200-400nm
and 1000-20,000 nm, whereas elevation of the particle concentration in the smaller size ranges
was often associated with other sources than the nanomaterial -related activities or emissions.
Off-line analysis confirmed the absence of the primary nanomaterial in the samples. Exceptions
are the observations for a CNT production facility reported by Han et al. (2008), who found
asbestos-like structures during sample analysis (Brouwer D., 2009).
Details from some of the individual studies mentioned above are summarized below:
Kuhlbusch et al. (2004) found that bag filling in a carbon black producing facility was not a
source of ultrafine particles. In the work areas of the reactor and pelletizer of three carbon black
production plants Kuhlbusch and Fissan (2006) found that elevated ultrafine particle number
concentrations with respect to ambient were related to nearby traffic emissions or to grease and
oil fumes from maintenance activities or, in one of the plants, to leaks in the production line,
which allowed particulate matter to escape to the surrounding areas. The authors concluded that
no carbon black is released in the reactor and pelletizing areas (as ultrafine particles or PMio)
from the closed production lines under normal operating conditions.
Maynard et al. (2004) carried out a laboratory based study to evaluate the physical nature of the
aerosol formed from single-walled carbon nanotube material (SWCNT) during mechanical
agitation, complemented with airborne and dermal exposure while handling unrefined material.
"3
Handling resulted in very low airborne concentrations (from 0.7-53 |ig/ m ), consistent with the
tendency to aggregate into larger masses (Maynard et al. 2004). Air measurements included large
airborne clumps of material larger then 1 |im or so in diameters that were not respirable. However
these particles, together with surface deposits, would pose a dermal exposure risk, as revealed by
the material on the individual gloves (from 217-6020 |ig), mostly on the parts of the gloves in
direct contact with surfaces (inner surfaces of fingers and palms).
Although the actual amount reaching the deep lung seems be negligible for many CNT
manufacturing and use settings, other field studies revealed higher airborne concentrations
especially in R&D facilities. For instance, in manufacturing multiple-walled carbon nanotubes,
researchers from the University of Seoul, showed gravimetric concentrations of total dust before
any control measures ranged from 0.21-0.43 mg/m3, then decreased to a non detectable level
after implementing the control measures (Han et al. 2008).
Presently, there are only a few published workplace air monitoring studies for production and
down-stream use of manufactured nanomaterials. Since a wide range of exposure scenarios and
types of manufactured nanomaterials are covered, it is difficult to get a good overall picture of
the potential for exposure resulting from activities related to these materials. Moreover, a wide
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variety of the format of presenting the data interferes an overall analysis, however, some general
observations can be made (Brouwer D., 2009):
• The likelihood of the presence of primary manufactured nanoobjects in the workplace, both
during production and down-stream use, seems to be low.
• There are indications that the type of aerosols is dominated by agglomerates and aggregates,
either exclusively consenting of manufactured nano-objects, or in combination with other and
'background' particles, therefore, size fractions up to 400-500nm might be of similar
importance as the nano-size range.
• For exposure analysis it would be interesting to know what the contribution of agglomerates
for different size fractions would be.
• For risk assessment it would be relevant to know what type of agglomerates and aggregates are
present and to what extend these structures will de-agglomerate in body fluids after uptake.
References
Aitken, RJ, Creely, KS, Tran, CL. 2004. Nanoparticles: An occupational hygiene review.
Research report prepared by the Institute of Occupational Medicine of Edinburgh for the Health
and Safety Executive. HSE Books. At: www.hse.gov.uk/research/rrhtm/rr274.htm.
BAuA (Bundesanstalt fur Arbeitsschutz und Arbeitsmedizin). 2006. Questionnaire on aspects of
worker protection during the production and handling of engineered nanomaterials, At:
www.baua.de/nn 49456/en/Topics-from-A-to-Z/HazardousSubstances/Nanotechnology.
Bergamaschi E. Occupational exposure to nanomaterials: Present knowledge and future
development. Nanotoxicology. 2009, Vol. 3, No. 3, Pages 194-201.
Han JH, Lee EJ, Lee JH, So KP, Lee YH, Bae GN, Lee SB, Ji JH, Cho MH, Yu IJ. Monitoring
multiwalled carbon nanotube exposure in carbon nanotube research facility. Inhal Toxicol 2008;
20(8)741-749
Kuhlbusch TA, Neumann S, Fissan H. Number size distribution, mass concentration, and particle
composition of PMi, PM2.5 and PMi0 in bagging areas of carbon black production. J Occup
Environ Hyg 2004; 1: 660-671
Kuhlbusch TA, Fissan H. Particle characteristics in the reactor and pelletizing areas of carbon
black production. J Occup Environ Hyg 2006; 3: 558-567
Lam CW, James JT, McCluskey R, Arepalli S, Hunter RL. A review of carbon nanotube toxicity
and assessment of potential occupational and environmental health risks. Crit Rev Toxicol 2006;
36:189-217
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Revised May 2012
Maynard AD, Baron PA, Foley M, Shvedova AA, Kisin ER, Castranova V. Exposure to carbon
nanotube material: aerosol release during the handling of unrefined single-walled carbon
nanotube material. J Toxicol Environ Health A 2004; 67: 87-107
Maynard AD, Aitken RJ. Assessing exposure to airborne nanomaterials: Current abilities and
future requirements. Nanotoxicology 2007; 1(1)26-41
National Institute for Occupational Safety and Health (NIOSH). 2007. Progress Toward Safe
Nanotechnology in the Workplace. No. 2007-123, NIOSH, Cincinatti. At:
http://www.cdc.gov/niosh/docs/2007-123/pdfs/2007-123.pdf.
Schneider, T, Jansson, A, Alstrup Jensen, K, Kristjansson, V, Luotamo, M, Nygren, N,
Savolainen, K,, et al. 2007. Evaluation and control of occupational health risks from
nanoparticles. TemaNord 2007:581 - Nordic Council of Ministers, Copenhagen 2007.
Schulte PA, Salamanca-Buentello F. Ethical and scientific issues of nanotechnology in the
workplace. Environ Health Perspect 2007; 115(1)5-12.
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APPENDIX D
Outstanding Data Needs for Nanomaterial Assessments
(as of February 2011)
Summary of OPPT/CEB Data* Needs for Nanomaterials (NM)
*Data Related to Releases, Treatment, Occupational Exposures, Engineering Controls, Personal
Protective Equipment (PPE), and Occupational Exposure Limits (OELs)
Table 1. Key Release and Treatment Information and Parameters in New NM Cases
Type of Data or Information
Source of Information/ Data
Outstanding Data Needs
Models for predicting releases and
environmental exposure that are specific
to nanomaterials.
Models developed by
universities and national and
international research
organizations.
Not available
Production Volume
PMN
None
Vapor Pressure (note: negligible for most
nano cases)
Chemistry Report
None
Molec Weight (note: n/a for most nano
cases)
Chemistry Report
None
Solubility in H20
Chemistry Report
None
Density (bulk)
Chemistry Report (or PMN)
None
Lifecycle steps
PMN or Literature
None
PV to each Lifecycle Step
PMN or EPAB
None
Process Description
PMN (or past cases or GS) or
Literature
None
Physical states of NM
PMN (or past cases or GS) or
Chemistry Report
None
Shipping containers for raw material
PMN (or past cases or GS) or
None
and/ or product containing NM
Literature
List of Release sources forNM
PMN (or past cases or GS)
None
# sites
PMN (or past cases or GS) or
Literature
None
# days/yr (or # batches/yr
PMN (or past cases or GS)
Generally not available
for downstream
processing and use
Kg/site-day NM produced or used (or
kg/batch)
PMN (or past cases or GS)
Generally not available
for downstream
processing and use
NM cone (wt fraction) in raw material
PMN (or past cases or GS)
Generally not available
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Table l. Key Release and Treatment Information and Parameters in New NM Cases
Type of Data or Information
Source of Information/ Data
Outstanding Data Needs
and/ or
for downstream
processing and use
Kg/site-day NM Released [or,
alternately, Loss fraction (e.g., emission
factor per kg/site-day NM production or
use rate)]
PMN (or model or GS)
Generally not available
for downstream
processing and use
Days/yr release
PMN (or model or GS)
Generally not available
for downstream
processing and use
Media of release
PMN (or model or GS)
Generally not available
for downstream
processing and use
Particle size
PMN or Chemistry Report
Limited information
available
Agglomeration characteristics
PMN or Chemistry Report
Limited information
available
On-site treatment technologies and
effectivess (including treatment related
parameters)
A current project being started
to gather information treatment
technologies in WPMN SG8
Not available
Destruction and removal efficiency in
incineration or burning
PMN or OSWER research
Limited laboratory data
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"l ahlc 2. Key ()ccupational l-xposure. Control. Protection, and ()l !l.-related Information
and Parameters in New NM Cases
Type <»r Data or Information
Source of Information/ Data
Outstanding Data Needs
Models for predicting occupational
exposure that are specific to
nanomaterials.
Models developed by
universities and national and
international research
organizations
Not available
Exposure monitoring
PBZ monitoring
"3
(mass in mg/m /
particle numbers)
NIOSH/
Research Articles
Limited information
available
Area monitoring (mass in mg/m3/
particle numbers)
NIOSH/ Research Articles
Limited information
available
Availability of certified
consultants/IHs to conduct exposure
monitoring
NA
Important for credible
data
Monitoring Techniques
NIOSH
Limited information
available
Sampling and Analytical Methods
NIOSH/OSHA
Limited information
available
Process/Activity specific data for a
NM type(data in mg/m3/
particle numbers)
NIOSH/ Research Articles
Limited information
available
Data on dermal exposure
NIOSH/ Research Articles
Not available
Particle size and distribution in dry
state
NIOSH/ Research Articles
Limited information
available
Agglomeration characteristics in dry
state
NIOSH/ Research Articles
Limited information
available
Engineering Controls
NIOSH/ Research Articles
Limited information
available
Presence/Absence of controls (e.g.,
glove boxes, ventilation)
PMN
Some provided in PMNs
Determine effectiveness of controls
NIOSH/ Research Articles
Limited information
available
Confirm effectiveness of HEP A
filters in exhaust ventilation
NIOSH
Not available
Effectiveness of Work Practices
NIOSH
Not available
Personal Protective Equipment
Respiratory protection
NIOSH/OSHA
None
Respirators
NIOSH
None
Dermal protection
NIOSH/OSHA
Limited information
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"l ahlc 2. Key ()ccupational l-\posure. Control. Protection, and ()l !l.-related Information
and Parameters in New NM Cases
Type of or Inl<>rin:ilion
Source of Information/ Data
Outstanding Data Needs
available
Effectiveness of gloves and
other barrier clothing
NIOSH/ASTM
Limited information
available
Permeation testing for gloves
ASTM
Not available
Occupational Exposure Limits (OELs)
OSHA PEL/NIOSH REL
Not available/ Only non-
regulatory limits available
Carbon nanotubes (CNT)/ Carbon
nanofibers (CNF)
NIOSH REL
Only non-regulatory
limits available
Titanium Dioxide
NIOSH RELs
Only non-regulatory
limits available
Other NMs
None
Not available
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