The goal of this interagency agreement is to provide support of National Toxicology Program (NTP) hazard identification (or hazard assessment) activities targeted toward the prevention of diseases or adverse effects caused by environmental exposure to chemical or physical agents. These studies capitalize on NIOSH's unique access to occupationally-exposed populations, and utilize NIOSH's expertise to complement NTP and NIEHS' capabilities. Under this agreement NIOSH will provide a real world context for NIEHS/NTP toxicology studies. To achieve this, NIOSH will characterize occupational exposure using a multidisciplinary approach to include toxicology, epidemiology, engineering, industrial science, and occupational medicine. Human health effects from workplace exposures to engineered nanomaterials are uncertain, as no epidemiological studies have been conducted. However, recent evidence suggests wide-ranging health effects from exposure to carbon nanotubes or nanofibers (CNTs or CNFs). Inhalation may cause injury at the site of initial exposure (e.g., pulmonary inflammation, fibrosis, or malignant transformation), but may also include effects at remote sites (e.g., immunological and cardiovascular effects). Several national and international organizations have emphasized the need for basic knowledge about the health effects of exposures to engineered nanomaterials, including CNTs and CNFs. This study will measure workplace exposures to CNTs and CNFs among a representative sample of US manufacturers and downstream users. nanotechnology