Occupational Exposure to Carbon Nanotubes and Nanofibers

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its member companies to assist them in controlling worker exposures to fine polyacrylatepolymer dust in the micrometer-size range through a combination of engineering controlsand work practices [IPA 2013]. The extent to which worker exposure to CNT and CNF canbe controlled below 1 µg/m 3 respirable mass concentration as an 8-hr TWA is unknown,but should be achievable in most manufacturing and end-use job tasks if engineering controlsare used and workers are instructed in the safe handling of CNT/CNF materials.Until results from research studies can fully explain the physical-chemical properties ofCNT and CNF that define their inhalation toxicity, all types of CNT and CNF should beconsidered a respiratory hazard, and exposures should be controlled as low as possiblebelow the REL. The REL is based on the respirable airborne mass concentration of CNTand CNF because the adverse lung effects in animals were observed in the alveolar (gasexchange)region. “Respirable” is defined as the aerodynamic size of particles that, wheninhaled, are capable of depositing in the alveolar region of the lungs [ICRP 1994]. Samplingmethods have been developed to estimate the airborne mass concentration of respirableparticles [ACGIH 1984; CEN 1993; ISO 1995; NIOSH 1998]. Reliance on a respirable ECmass-based REL will provide a means to identify job tasks with potential exposures to CNTand CNF so that appropriate measures can be taken to limit worker exposure.RecommendationsIn light of current scientific evidence from experimental animal studies concerning the hazardpotential of CNT and CNF, steps should be taken to implement an occupational healthsurveillance program that includes elements of hazard and medical surveillance. NIOSHrecommends that employers and workers take the following steps to minimize potentialhealth risks associated with exposure to CNT and CNF.1. Recommendations for Employers••Use available information to continually assess current hazard potential related to CNTand CNF exposures in the workplace and make appropriate changes (e.g., sampling andanalysis, exposure control) to protect worker health. At a minimum, follow requirementsof the OSHA Hazard Communication Standard [CFR 1910.1200(h)] and theHazardous Waste Operation and Emergency Response Standard [29 CFR 1910.120].••Identify and characterize processes and job tasks where workers encounter bulk(“free-form”) CNT or CNF and materials that contain CNT/CNF (e.g., composites).••Substitute, when possible, a nonhazardous or less hazardous material for CNT andCNF. When substitution is not possible, use engineering controls as the primarymethod for minimizing worker exposure to CNT and CNF.••Establish criteria and procedures for selecting, installing, and evaluating the performanceof engineering controls to ensure proper operating conditions. Make sure workers aretrained in how to check and use exposure controls (e.g., exhaust ventilation systems).• • Routinely evaluate airborne exposures to ensure that control measures are workingproperly and that worker exposures are being maintained below the NIOSH REL of1 µg/m 3 using NIOSH Method 5040 (Section 6 and Appendix C).xiiNIOSH CIB 65 • Carbon Nanotubes and Nanofibers
••Follow exposure and hazard assessment procedures for determining the need for andselection of proper personal protective equipment, such as clothing, gloves, and respirators(Section 6).••Educate workers on the sources and job tasks that may expose them to CNT and CNF,and train them about how to use appropriate controls, work practices, and personalprotective equipment to minimize exposure (Section 6.3).••Provide facilities for hand washing and encourage workers to make use of these facilitiesbefore eating, smoking, or leaving the worksite.••Provide facilities for showering and changing clothes, with separate facilities for storageof nonwork clothing, to prevent the inadvertent cross-contamination of nonworkareas (including take-home contamination).••Use light-colored gloves, lab coats, and workbench surfaces to make contaminationby dark CNT and CNF easier to see.••Develop and implement procedures to deal with cleanup of CNT and CNF spills anddecontamination of surfaces.••When respirators are provided for worker protection, the OSHA respiratory protectionstandard [29 CFR 1910.134] requires that a respiratory protection program beestablished that includes the following elements:ȣȣȣȣȣȣȣȣȣȣȣȣA medical evaluation of the worker’s ability to perform the work while wearinga respirator.Regular training of personnel.Periodic workplace exposure monitoring.Procedures for selecting respirators.Respirator fit testing.Respirator maintenance, inspection, cleaning, and storage.••The voluntary use of respirators are permitted, but must comply with the provisionsset forth in CFR 1910.134(c)(2)(i) and CFR 1910.134(c)(2)(ii).••Information on the potential health risks and recommended risk management practicescontained in this CIB should, at a minimum, be used when developing labels andSafety Data Sheets (SDS), as required [http://www.osha.gov/dsg/hazcom].1.1 Medical Screening and SurveillanceThe evidence summarized in this document leads to the conclusion that workers occupationallyexposed to CNT and CNF may be at risk of adverse respiratory effects. These workers maybenefit from inclusion in a medical screening program to help protect their health (Section 6.7).1.1.1 Worker ParticipationWorkers who could receive the greatest benefit from medical screening include the following:• • Workers exposed to concentrations of CNT or CNF in excess of the REL (i.e., allworkers exposed to airborne CNT or CNF at concentrations above 1 µg/m 3 EC as an8-hr TWA).NIOSH CIB 65 • Carbon Nanotubes and Nanofibersxiii
Page 1 and 2: CURRENT INTELLIGENCE BULLETIN 65Occ
Page 3 and 4: Current Intelligence Bulletin 65Occ
Page 5 and 6: ForewordThe Occupational Safety and
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: possible. Until the results from an
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
Page 55 and 56: Table 3-7 (Continued). Findings fro
Page 57: Table 3-8. Findings from published
Page 60 and 61: length, respectively) [Muller et al
Page 63 and 64: 5 CNT Risk Assessment and Recommend
Page 65 and 66:
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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