Occupational Exposure to Carbon Nanotubes and Nanofibers

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This document is in the public domain and may be freely copiedor reprinted.DisclaimerMention of any company or product does not constitute endorsement by the National Institutefor Occupational Safety and Health (NIOSH). In addition, citations to websites externalto NIOSH do not constitute NIOSH endorsement of the sponsoring organizationsor their programs or products. Furthermore, NIOSH is not responsible for the content ofthese websites. All Web addresses referenced in this document were accessible as of thepublication date.Ordering InformationTo receive documents or other information about occupational safety and health topics,contact NIOSH:Telephone: 1–800–CDC–INFO (1–800–232–4636)TTY: 1–888–232–6348CDC INFO: www.cdc.gov/infoor visit the NIOSH Web site at http://www.cdc.gov/nioshFor a monthly update on news at NIOSH, subscribe to NIOSH eNews by visiting www.cdc.gov/niosh/eNews.DHHS (NIOSH) Publication No. 2013–145April 2013Safer • Healthier • People TMiiNIOSH CIB 65 • Carbon Nanotubes and Nanofibers
ForewordThe Occupational Safety and Health Act of 1970 (Public Law 91-596) was passed to assuresafe and healthful working conditions for every working person and to preserve our humanresources. This Act charges the National Institute for Occupational Safety and Health(NIOSH) with recommending occupational safety and health standards and describingexposures that are safe for various periods of employment, including (but not limited to)the exposures at which no worker will suffer diminished health, functional capacity, or lifeexpectancy because of his or her work experience.NIOSH issues Current Intelligence Bulletins (CIBs) to disseminate new scientific informationabout occupational hazards. A CIB may draw attention to a formerly unrecognizedhazard, report new data on a known hazard, or disseminate information about hazard control.CIBs are distributed to representatives of academia, industry, organized labor, publichealth agencies, and public interest groups, as well as to federal agencies responsible forensuring the safety and health of workers.NIOSH is the leading federal agency conducting research and providing guidance on theoccupational safety and health implications and applications of nanotechnology. As nanotechnologycontinues to expand into every industrial sector, workers will be at an increasedrisk of exposure to new nanomaterials. Today, nanomaterials are found in hundreds ofproducts, ranging from cosmetics, to clothing, to industrial and biomedical applications.These nanoscale-based products are typically called “first generation” products of nanotechnology.Many of these nanoscale-based products are composed of engineered nanoparticles,such as metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes(buckyballs), among others. Early scientific studies have indicated that some of these nanoscaleparticles may pose a greater health risk than the larger bulk form of these materials.Results from recent animal studies indicate that carbon nanotubes (CNT) and carbon nanofibers(CNF) may pose a respiratory hazard. CNTs and CNFs are tiny, cylindrical, large aspectratio, manufactured forms of carbon. There is no single type of carbon nanotube or nanofiber;one type can differ from another in shape, size, chemical composition (from residualmetal catalysts or functionalization of the CNT and CNF) and other physical and chemicalcharacteristics. Such variations in composition and size have added to the complexity ofunderstanding their hazard potential. Occupational exposure to CNTs and CNFs can occurnot only in the process of manufacturing them, but also at the point of incorporating thesematerials into other products and applications. A number of research studies with rodentshave shown adverse lung effects at relatively low-mass doses of CNT and CNF, including pulmonaryinflammation and rapidly developing, persistent fibrosis. Although it is not knownwhether similar adverse health effects occur in humans after exposure to CNT and CNF, theresults from animal research studies indicate the need to minimize worker exposure.This NIOSH CIB, (1) reviews the animal and other toxicological data relevant to assessingthe potential non-malignant adverse respiratory effects of CNT and CNF, (2) provides aNIOSH CIB 65 • Carbon Nanotubes and Nanofibersiii
Page 1 and 2: CURRENT INTELLIGENCE BULLETIN 65Occ
Page 3: Current Intelligence Bulletin 65Occ
Page 7 and 8: Executive SummaryOverviewCarbon nan
Page 9 and 10: 2009; Pauluhn 2010a; Porter et al.
Page 11 and 12: neurogenic sig nals from sensory ir
Page 13 and 14: possible. Until the results from an
Page 15 and 16: ••Follow exposure and hazard as
Page 17 and 18: Periodic Evaluations••Evaluatio
Page 19 and 20: ContentsForeword ..................
Page 21 and 22: A.3.2 Comparison of Short-term and
Page 23 and 24: ESPFeFMPSFPSSgGMGSDHCLHECHEPAhrISOI
Page 25 and 26: AcknowledgementsThis Current Intell
Page 27 and 28: 1 IntroductionMany nanomaterial-bas
Page 29: 2 Potential for ExposureThe novel a
Page 32 and 33: CNMs, with MWCNT agglomerates obser
Page 34 and 35: composite materials with local exha
Page 36 and 37: information on air contaminants. Sa
Page 39 and 40: 3 Evidence for Potential Adverse He
Page 41 and 42: decreasing agglomerate size increas
Page 43 and 44: examined up to 60 days post-exposur
Page 45 and 46: 3.3 SWCNT and MWCNTIntraperitoneal
Page 47 and 48: The same potency sequence was obser
Page 49 and 50: Table 3-3. Findings from published
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Table 3-7 (Continued). Findings fro
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Table 3-8. Findings from published
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length, respectively) [Muller et al
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5 CNT Risk Assessment and Recommend
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A-6). Risk estimates derived from o
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Table 5-4. Factors, assumptions, an
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and analytical methods. NIOSH is re
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Table 5-5. Recommended occupational
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deficits in animals or clinically s
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(3) Rat lung dose estimationIn the
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tasks where worker exposures exceed
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As part of the evaluation of worker
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Table 6-1. EC LODs and LOQs for 25-
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6.2 Engineering ControlsOne of the
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Table 6-6 (Continued). Examples of
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Table 6-7 (Continued). Engineering
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exposure estimates for SWCNT on ind
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Table 6-8. Respiratory protection f
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••Workers in areas or in jobs w
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7 Research NeedsAdditional data and
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ReferencesACGIH [1984]. Particle si
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Bolton RE, Vincent HJ, Jones AD, Ad
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eport issued on July 22, 2011. NEDO
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Kobayashi N, Naya M, Mizuno K, Yama
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Methner M, Hodson L, Geraci C [2010
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Human Services, Centers for Disease
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Piegorsch WW, Bailer AF [2005]. Qua
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AD, Baron PA [2003]. Exposure to ca
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Varga C, Szendi K [2010]. Carbon na
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ContentsA.1 Introduction ..........
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A.1 IntroductionThe increasing prod
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provide an informal check on the es
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these same dose groups; this effect
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Table A-1. Rodent study information
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the deposited (no clearance) and th
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The other BMDS models failed to con
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Figure A-2. Benchmark dose model (m
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Figure A-3 (continued). Benchmark d
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Table A-3. Benchmark dose estimates
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Table A-5. Benchmark dose estimates
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histopathology grade 2 or higher lu
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Table A-8. Working lifetime percent
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developing early-stage adverse lung
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Figure A-4. Dose-response relations
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cell surface area). However, the wo
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purified or unpurified (with differ
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Table A-9. Comparison of rat or hum
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A.6.1.3 Pulmonary Ventilation RateT
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used as the effect levels in evalua
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the DF estimate, although a larger
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or overloading, of particle clearan
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Table A-13. Human-equivalent retain
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A.7.1 Particle CharacteristicsBoth
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and density. The following MMAD and
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Table A-15. CNT lung dose normalize
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B.1 Key Terms Related toMedical Sur
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APPENDIX CNIOSH Method 5040
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filter. In the method evaluation, d
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Most of the studies on sampling art
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e analyzed to determine the onset o
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Delivering on the Nation’s promis
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