Occupational Exposure to Carbon Nanotubes and Nanofibers

6 RecommendationsIn light of current scientific evidence on the hazardpotential of CNT and CNF, appropriate stepsshould be taken to minimize worker exposurethrough the development of a risk managementprogram and implementation of an exposure controlstrategy. Elements of that program should includethe following:1. Control worker exposure to CNT and CNFbelow 1 µg/m 3 8-hr TWA, respirable fraction(elemental carbon) during a 40-hr work week.2. Conduct comprehensive exposure assessments(including exposures to other potential hazards)as part of an overall hazard surveillanceprogram.3. Develop guidelines for selecting, installing, andevaluating engineering controls (e.g., local exhaustventilation, dust collection systems).4. Educate and train workers on the recognition ofpotential exposures and in the use of good workpractices in the handling of bulk CNT and CNF,as well as CNT- and CNF-containing materials.5. Develop procedures for the selection and useof personal protective equipment (i.e., clothing,gloves, respirators).6. Implement a medical surveillance program forworkers potentially exposed to CNT or CNFwith conduct of specific medical screening testswhen warranted (Section 6.7).7. Conduct routine (e.g., annual) and systematicevaluation of worker exposure to CNT or CNFwhen there is a process change in how CNT orCNF are manufactured or handled.8. Encourage workers to wash hands before eating,smoking, or leaving the worksite.9. Establish facilities for showering and changingclothes, with separate facilities for storage ofnon-work clothing, to prevent the inadvertentcross contamination of other areas (includingtake-home).6.1 Exposure AssessmentNIOSH is recommending that a respirable massbasedairborne concentration measurement beused to monitor worker exposure to all types ofCNT and CNF until additional data are availableto determine whether other measurement metricsor techniques would be more effective in protectingworkers’ health. NIOSH is currently evaluating theefficacy of various sampling techniques for measuringCNT and CNF and may make additionalrecommendations at a later date.Personal exposure concentrations to CNT and CNFcan be determined as elemental carbon (EC) byNIOSH Method 5040 [NIOSH 1994; Birch 2004a,b]. Whenever possible, a bulk sample of the CNT/CNF material should be analyzed to establish thethermal profile for the material(s) (Appendix C).Measurement results from NIOSH Method 5040should provide a reasonable estimate of a worker’srespirable exposure to CNT and CNF at the NIOSHREL of 1 µg/m 3 8-hr TWA when the predominantworkplace exposure to EC material is CNT or CNF.6.1.1 Exposure Monitoring ProgramAn exposure-monitoring program should be establishedto ensure that worker exposures to CNT andCNF are maintained below the REL. The programshould consist of a plan designed to do the following:(1) characterize exposures of all exposed workers;(2) identify sources of potential EC exposures(e.g., diesel soot, carbon black) that may interferewith the interpretation of worker CNT and CNFexposures; (3) identify specific work areas or jobNIOSH CIB 65 • Carbon Nanotubes and Nanofibers51