Occupational Exposure to Carbon Nanotubes and Nanofibers

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information on air contaminants. Samples wereanalyzed for organic, elemental, and total carbon(OC + EC = TC), metals, and polycyclic aromatichydrocarbons (PAHs), with EC as a measure ofCNF. TEM with energy-dispersive X-ray spectroscopy(TEM-EDS) also was applied. Study results forthe time-integrated (filter/sorbent) samples werereported in companion papers, with OC-EC, metals,and microscopy results in part I [Birch et al.2011b] and PAH results in part II [Birch 2011a].Fine/ultrafine, iron-rich soot, PAHs, and carbonmonoxide were production byproducts. Area concentrationsof respirable EC inside the facility wereabout 6 to 68 times higher than outdoors, whilePBZ samples were up to 170 times higher.As part of the same study, multiple direct-readinginstruments (e.g., CPC, ELPI, photometer/withcyclone, diffusion charger, fast particulate sizespectrometer [FPSS]) and respirable particle massconcentrations were used to assess CNF exposureson site and to evaluate instrument performance. Atransient increase in respirable mass concentrationwas observed during manual bagging of the finalproduct and was attributed to aerosolized CNF.The tamping of the bag to settle contents and thesubsequent closing dispersed CNF through the bagopening into the workplace. High particle numberand active surface area concentrations were foundduring the opening of the dryer and during themanual redistribution of the CNF product. Thiswas attributed to the presence of ultrafine particlesemitted from the dryer and as by-products formedthrough the high-temperature thermal processingof CNF. No elevations in respirable mass concentrationswere observed during these operations,suggesting that significant quantities of CNF werenot released into the workplace. However, thetransfer or dumping of dried CNF from a dryer toa drum, and subsequent bag change-out of finalproduct, contributed the largest transient increasesin respirable mass concentrations, with concentrationsexceeding 1.1 mg/m 3 for transfer or dumpingand 0.5 mg/m 3 for bag change-out. The authorsconcluded that integrated particle number and activesurface area concentrations (i.e., using CPCand diffusion charger) were not useful in assessingthe contribution of emissions from CNF in theworkplace, because measurements were dominatedby ultrafine particle emissions [Evans et al. 2010].Respirable particle mass concentrations estimatedby the photometer appeared to be the most usefuland practical metric for measuring CNF when usingdirect-reading instruments. Results obtainedfor filter samples support the direct-reading instrumentfindings. The TEM analyses of size-selectivearea samples indicated that large fiber bundles werepresent [Birch et al. 2011b]. In addition, sizeclassifiedsamples (collected with impactors) analyzedfor EC (by NIOSH 5040) indicated CNF particlesin the micrometer range [Birch et al. 2011b].10 NIOSH CIB 65 • Carbon Nanotubes and Nanofibers
Figure 2–1. Workplaces and job tasks with potential for occupational exposure to carbon nanotubes andnanofibers. Adapted from Schulte et al. 2008.NIOSH CIB 65 • Carbon Nanotubes and Nanofibers11
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 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 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
Page 67 and 68: Table 5-4. Factors, assumptions, an
Page 69 and 70: and analytical methods. NIOSH is re
Page 71 and 72: Table 5-5. Recommended occupational
Page 73 and 74: deficits in animals or clinically s
Page 75: (3) Rat lung dose estimationIn the
Page 78 and 79: tasks where worker exposures exceed
Page 80 and 81: As part of the evaluation of worker
Page 82 and 83: Table 6-1. EC LODs and LOQs for 25-
Page 84 and 85: 6.2 Engineering ControlsOne of the
Page 86 and 87:
Table 6-6 (Continued). Examples of
Page 88 and 89:
Table 6-7 (Continued). Engineering
Page 90 and 91:
exposure estimates for SWCNT on ind
Page 92 and 93:
Table 6-8. Respiratory protection f
Page 94 and 95:
••Workers in areas or in jobs w
Page 97 and 98:
7 Research NeedsAdditional data and
Page 99 and 100:
ReferencesACGIH [1984]. Particle si
Page 101 and 102:
Bolton RE, Vincent HJ, Jones AD, Ad
Page 103 and 104:
eport issued on July 22, 2011. NEDO
Page 105 and 106:
Kobayashi N, Naya M, Mizuno K, Yama
Page 107 and 108:
Methner M, Hodson L, Geraci C [2010
Page 109 and 110:
Human Services, Centers for Disease
Page 111 and 112:
Piegorsch WW, Bailer AF [2005]. Qua
Page 113 and 114:
AD, Baron PA [2003]. Exposure to ca
Page 115:
Varga C, Szendi K [2010]. Carbon na
Page 119 and 120:
ContentsA.1 Introduction ..........
Page 121 and 122:
A.1 IntroductionThe increasing prod
Page 123 and 124:
provide an informal check on the es
Page 125 and 126:
these same dose groups; this effect
Page 127 and 128:
Table A-1. Rodent study information
Page 129 and 130:
the deposited (no clearance) and th
Page 131 and 132:
The other BMDS models failed to con
Page 133 and 134:
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
Page 143 and 144:
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
Page 151 and 152:
purified or unpurified (with differ
Page 153 and 154:
Table A-9. Comparison of rat or hum
Page 155 and 156:
A.6.1.3 Pulmonary Ventilation RateT
Page 157 and 158:
used as the effect levels in evalua
Page 159 and 160:
the DF estimate, although a larger
Page 161 and 162:
or overloading, of particle clearan
Page 163 and 164:
Table A-13. Human-equivalent retain
Page 165 and 166:
A.7.1 Particle CharacteristicsBoth
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and density. The following MMAD and
Page 169:
Table A-15. CNT lung dose normalize
Page 172 and 173:
B.1 Key Terms Related toMedical Sur
Page 175 and 176:
APPENDIX CNIOSH Method 5040
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filter. In the method evaluation, d
Page 179 and 180:
Most of the studies on sampling art
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e analyzed to determine the onset o
Page 184:
Delivering on the Nation’s promis
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