The International Agency for Research on Cancer (IARC) has classified ambient outdoor particulate matter (PM) as a Group 1 human carcinogen. It is unclear, however, if the lung cancer risks primarily linked to long-term exposure to fine PM (PM2.5, aerodynamic diameter <2.5µm) are driven by its constituent ultrafine particles (UFP, <100nm), which may be more toxic due to their unique physiochemical properties. This prospective cohort study among the NIH-AARP Diet and Health Study participants in the Los Angeles Basin is being conducted in collaboration with the University of Southern California and Utrecht University. The primary aim of the Los Angeles Ultrafines Study is to evaluate the association between long-term exposure to ambient outdoor UFP and lung cancer risk.
The Los Angeles Ultrafines Study population has several important features needed to assess this etiologic relationship, including substantial regional variation in PM concentrations, large numbers of lung cancer cases, and data on smoking and residential histories. A comprehensive retrospective exposure assessment draws upon one of the most complete repositories of historical UFP data available, supplemented by a mobile ambient monitoring campaign in Los Angeles and surrounding counties.