Understanding workplace exposures and potential health effects of carbon nanotubes and nanofibers in the United States

Abstract

Background: Toxicologic and cross-sectional epidemiological studies indicate that inhalation of carbon nanotubes and nanofibers (CNT/F) may cause adverse health effects, but large longitudinal studies are needed to better understand risks associated with handling CNT/F. Researchers at the United States National Institute for Occupational Safety and Health have undertaken a multifaceted approach to characterize and quantify CNT/F workplace exposures and health risks, culminating in the development of an exposure registry and prospective cohort study of CNT/F workers. Methods: Companies in the US that handle CNT/F and operate above the research and development phase are being recruited into the exposure registry. Participating companies are asked to provide complete worker rosters, including demographic information and job tasks for each worker. The exposure registry relies on prior exposure assessments, regression models, and expert opinion to estimate exposures from work history records. After recruitment is complete, records will be used as the basis for a prospective cohort study. Linkage to the National Death Index will be used to assess for mortality outcomes. Additional outcomes will be assessed by questionnaire. Disease rates will be assessed by occupational CNT/F exposure level and compared to disease rates in the US population. Results: The exposure registry is open and continues to recruit companies that handle CNT/F. To date, approximately 600 individual workers with potential exposure to CNT/F at 13 facilities have been included in the exposure registry. By the end of 2022, researchers plan to collect a total of 1,500 worker records. Exposure assessments have demonstrated that CNT/F exposures are occurring in the workplace, and workers who handle CNT/F can experience a wide range of occupational CNT/F exposure. Conclusions: Through the development of an exposure registry and subsequent prospective cohort study, researchers will be able to more quickly identify the development of adverse health conditions, if any exist.