An investigation of carbon nanotube exposure assessment methods
Project Period:
2012
Project Investigator(s):
P. O’Shaughnessy, R. Altmaier, A. Horne, Department of Occupation and Environmental Health, University of Iowa
Abstract:
Carbon nanotubes (CNTs) are engineered nanoparticles (<100 nm) that have been shown to cause adverse pulmonary outcomes in test animals. As such, the National Institute for Occupational Safety and Health (NIOSH) is considering a recommended exposure level (REL) for CNTs of 7 µg/m3, which is the limit of quantification (LOQ) of a method used to measure elemental carbon (EC) in diesel particles. Such a limit presents either an under- or over-exposure scenario with no information to determine actual conditions when below the LOQ. This pilot project will seek to establish a relationship between CNT particle count concentrations given known size distributions and EC mass concentrations to guide the interpretation of environments that may become contaminated with CNTs below the LOQ. A secondary objective will be to compare EC concentrations measured using the NIOSH method with those obtained from a hand-held device suitable for personal exposure assessments.
Project Results:
Many workplaces in Iowa produce indoor air hazards that may be harmful to workers. This study addresses those that produce carbon-containing particles in general, such as diesel exhaust, and those that produce engineered carbon nanotubes in particular.
The study compared several methods for detecting airborne concentrations of carbon nanotubes (CNTs). The motivation for this work is related to recent recommendation by the U.S. National Institute for Occupational Safety and Health (NIOSH) to utilize their Method 5040 to detect carbon nanotube aerosol concentrations in workplaces. A novel device was developed to deposit a desired mass of CNTs on a filter for analysis by Method 5040. We determined that Method 5040 has a limit of detection that is not low enough to consistently measure concentrations below the recommended exposure level of 1 microgram per cubic meter established by NIOSH.