Using Factor Analysis to Attribute Health Impacts to Particulate Pollution Sources1

Pollution Sources Thomas Grahame U. S. Department of Energy Washington, DC George Hidy Envair/Aerochem Placitas, NM ABSTRACT Laden et al. (2000) recently reported results of applying factor analysis to data taken in six cities from1979 to1988, identifying airborne particle sources potentially affecting daily mortality. These authors sought relationships between source groups and risk measures using source tracer elements, Se (coal combustion), Pb (light duty motor vehicle sources), and Si (crustal--soil dispersion). Combined data analyses of this kind may overlook the complexity of source contributions, which have common tracer elements. In one of the cities, Boston for example, the authors found coal combustion was an important source of mortality risk. For the city of Boston, the authors attribute coal combustion largely to distant upwind regional sources. The emphasis on coal combustion is confounded by the presence of major local sources of residual oil combustion, which contribute V, Se and S (sulfur as sulfate) to the source apportionment. Evaluation of the source identification using single element tracer analysis indicates that the detailed chemical composition or profile of major local sources needs to be taken into account in these investigations to minimize misclassification of airborne particle sources with potential adverse health effects. Accepted by for publication, 7/14/03, in Special Issue of Inhalation Toxicology on Particulate Air Pollution and Health (Revised 7/2/03)