Exposure and emissions monitoring during carbon nanofiber production--Part II: polycyclic aromatic hydrocarbons

Abstract

Production of carbon nanofibers and nanotubes (CNFs/CNTs) and their composite products is increasing globally. High-volume production may increase the exposure risks for workers who handle these materials. Though health effects data for CNFs/CNTs are limited, some studies raise serious health concerns. Given the uncertainty about their potential hazards, there is an immediate need for toxicity data and field studies to assess exposure to CNFs/CNTs. An extensive study was conducted at a facility that manufactures and processes CNFs. Filter, sorbent, cascade impactor, bulk, and microscopy samples, combined with direct-reading instruments, provided complementary information on air contaminants. Samples were analyzed for organic and elemental carbon (OC and EC), metals, and polycyclic aromatic hydrocarbons (PAHs), with EC as a measure of CNFs. Transmission electron microscopy with energy-dispersive X-ray spectroscopy also was applied. Fine/ultrafine iron-rich soot, PAHs, and carbon monoxide were production byproducts. Direct-reading instrument results were reported previously [Evans DE et al. (Aerosol monitoring during carbon nanofiber production: mobile direct-reading sampling. Ann Occup Hyg 2010; 54:514-31)]. Results for time-integrated samples are reported as companion papers in this issue. OC and EC, metals, and microscopy results are reported in Part I [Birch ME et al. (Exposure and emissions monitoring during carbon nanofiber production-Part I: elemental carbon and iron-soot aerosols. Ann Occup Hyg 2011; 55: 1016-36.)] whereas results for PAHs are reported here. Naphthalene and acenaphthylene were the dominant PAHs with average concentrations ranging from 115 to 336 μg m(-3) and 35 to 84 μg m(-3), respectively. Concentrations of other PAHs ranged from ∼1 to 10 μg m(-3).

Fig. 1

a) Average concentrations of naphthanene and acenaphthylene in different areas over two survey days in December. (b) Average PAH concentrations in different areas over two survey days in December.

Fig. 2

a) Average concentrations of naphthalene and acenaphthylene in different areas over two survey days in February. (b) Average PAH concentrations in different areas over two survey days in February.

Fig. 3

a) Average concentrations of naphthalene and acenaphthylene in different areas over all survey days (four total). (b) Average PAH concentrations in different areas over all survey days (four total).

Fig. 4

PAH results for three bulk CNF samples of unprocessed products from Reactors A and B and a final product.