Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August-1 September 2010: Air Pollution - Exposure Characterization and Health Effects
Epidemiological studies most often make use of air pollution measurements undertaken for other purposes, most often regulatory purposes. The number of pollutants measured is limited; in the United States, only 6 pollutants are measured widely and regularly, and even these are not measured daily. A smaller network of monitors measures several particulate matter components (ions, sulfates nitrates, elemental carbon [EC]/organic carbon), again not on a daily basis. These limitations limit the statistical power for times series analyses of acute health effects, but they do allow estimates of the longer-term exposure to specific pollutants in several communities. In addition to these monitored pollutants, there is a list of 188 hazardous substances for which a detailed emissions inventory is obtained. The US Environmental Protection Agency uses this inventory to model ambient concentrations of these substances.
This study attempted to relate the mortality experience of a cohort of about 70,000 male veterans to the levels of the various pollutants in their communities. In single pollutant models, several particulate matter components were related to mortality after adjustment for personal and community risk factors. These included EC, nitrate, vanadium, and nickel.
When these variables were included in a model with a measure of traffic density, their significance disappeared; only EC remained near significance. When the exposure estimates for the hazardous substances were related to mortality and remained significant in the presence of a traffic density variable. These included benzene, formaldehyde, nickel, polycyclic organic compounds, none of which are routinely measured.
These results suggest the importance of monitoring and studying these compounds further and raise the possibility that currently monitored pollutants could be serving as indicators or surrogates for some of the unmonitored compounds.