Alice Hamilton Awards: Research Updates for 2011 - Engineering and Physical Sciences

Companion research articles from the 2010 study that report the time integrated aspects of sampling, including personal monitoring, chemical composition, particle morphology, and health relevant size-selective sampling, were published in 2011 (Birch et al. 2011, Birch 2011 below). In combination with the direct-reading aerosol monitoring reported in the 2010 article, these papers provided a greater understanding of workplace emissions and worker exposure. Not only were the contributions of emissions from the different processes differentiated, knowledge also was gained of how the exposures were occurring, their relative magnitudes, and the extent of contaminant migration through the facility. The complexity of the emissions in this workplace presented a considerable challenge. There were exposures to a complex mixture of carbon nanofibers (CNFs), polycyclic aromatic hydrocarbons (PAHs), fine and ultrafine iron, carbonaceous soot, and carbon monoxide. Different emission sources were also identified. Understanding how exposures were occurring was a crucial step to reducing exposure. The facility was able to take corrective steps toward reducing worker exposure by implementing better containment, local exhaust ventilation, and improved work practices.

Since the study on which the 2010 article reported was conducted from late 2007 to early 2008, multiple workplace monitoring and exposure assessment evaluations have been conducted by the authors in the Division of Applied Research and Technology (DART), more recently with colleagues in the Division of Surveillance, Hazard Evaluations, and Field Studies (DSHEFS). These pilot industry-wide evaluations have focused on carbon nanotubes (CNTs) and CNFs and have included primary manufacturers and downstream users of these novel materials. During the past few years, there has been significant growth in the production and use of these materials in electronics, high performance composites, and medical applications. The sampling methods, instruments evaluated, and lessons learned from the former (2007-2008) study have been directly applied to subsequent workplace evaluations. Results from the first six industry-wide exposure assessments have recently been published (Dahm et al. 2012). Worker exposures to CNFs and CNTs are occurring, the magnitude of which is often influenced by the quantities and form (i.e. liquid slurry or powder) of novel materials involved, the type of operation or process used, and whether exposure controls have been implemented and are adequately functioning.

Together with DSHEFS partners, the authors recently received a grant award from the US National Toxicology Program to conduct a number of industry-wide exposure assessments at CNT and CNF facilities. As a component of these workplace assessments, it is anticipated that biomonitoring of the workers will be conducted during the latter phase of the study, in parallel with the air monitoring.

Birch ME, Ku BK, Evans DE, Ruda-Eberenz T (2011). Exposure and emissions monitoring during carbon nanofiber production - Part I: Elemental carbon and iron-soot aerosols. Ann Occup Hyg 55(9):1016-36.

Birch ME [2011]. Exposure and emissions monitoring during carbon nanofiber production - Part II: Polycyclic aromatic hydrocarbons. Ann Occup Hyg 55(9):1037-47.

Dahm MM, Evans DE, Schubauer-Berigan MK, Birch ME, Fernback JE. Occupational exposure assessment in carbon nanotube and nanofiber primary and secondary manufacturers. Ann Occup Hyg (In Press).