The public health context for PM2.5 and ozone air quality trends

Tropospheric ozone (O-3) and particulate matter (PM2.5) are associated with adverse health effects, including premature mortality. Regulation of these pollutants by the US Environmental Protection Agency has resulted in significant improvements in air quality over the last decade, as demonstrated by a national network of air quality monitors. However, ambient trends provide limited information regarding either the change in population exposure to these pollutants or how fluctuations in the levels of these pollutants might affect public health. We leverage the spatially and temporally extensive monitoring network in the US to estimate the improvements to public health associated with monitored air quality changes over a 7-year period. We estimate the impacts of monitored changes in ozone and PM2.5 on premature mortality using health impact functions based on short-term relative risk estimates for O-3 and long-term relative risk estimates for PM2.5. We spatially interpolate the O-3 and PM2.5 data and utilize ozone air quality data that are adjusted for meteorological variability. We estimate that reductions in monitored PM2.5 and ozone from 2000 to 2007 are associated with 22,000-60,000 PM2.5 and 880-4,100 ozone net avoided premature mortalities. The change in estimated premature mortality can be highly variable from 1 year to the next, sometimes by thousands of deaths. The estimate of avoided ozone-related mortalities is sensitive to the use of meteorologically-adjusted air quality inputs. Certain locations, including Los Angeles and Houston see an opposing trend between mortality impacts attributable to ozone and PM2.5.We find that improving air quality over the past 7 years has reduced premature mortality significantly.