Reliable estimates of inhalation intake of air pollution and its distribution among a specified population are important for environmental epidemiology, health risk assessment, urban planning, and environmental policy. We computed distributional characteristics of the inhalation intake of five pollutants for a group of ∼25,000 people (∼29,000 person-days) living in California's South Coast Air Basin. Our approach incorporates four main inputs: temporally resolved information about people's location (latitude and longitude), microenvironment, and activity level; temporally and spatially explicit model determinations of ambient concentrations; stochastically determined microenvironmental adjustment factors relating the exposure concentration to the ambient concentration; and, age-, gender-, and activity-specific breathing rates. Our study is restricted to pollutants of outdoor origin, i.e. it does not incorporate intake in a microenvironment from direct emissions into that microenvironment. Median estimated inhalation intake rates (μg d-1) are 53 for benzene, 5.1 for 1,3-butadiene, 8.7×10-4 for hexavalent chromium in fine particulate matter (Cr-PM2.5), 30 for diesel fine particulate matter (DPM2.5), and 68 for ozone. For the four primary pollutants studied, estimated median intake rates are higher for non-whites and for individuals in low-income households than for the population as a whole. For ozone, a secondary pollutant, the reverse is true. Accounting for microenvironmental adjustment factors, population mobility and temporal correlations between pollutant concentrations and breathing rates affects the estimated inhalation intake by 40% on average. The approach presented here could be extended to quantify the impact on intakes and intake distributions of proposed changes in emissions, air quality, and urban infrastructure.
Bibliographical noteFunding Information:
Funding for this work was provided by the University of California Transportation Center, the University of California Toxic Substances Research & Teaching Fellowship, Cooperative Agreement Number U50/CCU922409-01 from the US Centers for Disease Control and Prevention, the US Environmental Protection Agency National Exposure Research Laboratory through Interagency Agreement No. DW-988-38190-01-0, and Lawrence Berkeley National Laboratory operated for the US Department of Energy under Contract Grant no. DE-AC02-05CH11231. The authors thank Paul Burke and Pablo Gutierrez at the Southern California Association of Governments (Los Angeles, California) for providing SCAG transportation survey data, and the air-pollution modeling group at Environ Corporation (Novato, California) for providing CAMx air dispersion model results.
- Diesel particulate matter
- Environmental justice
- Exposure analysis
- Geographic information system (GIS)