PRELIMINARY COMPARISONS BETWEEN MUTAGENICITY AND MAGNETIC-SUSCEPTIBILITY OF RESPIRABLE AIRBORNE PARTICULATE

The magnetic susceptibility of respirable urban airborne particulate and the mutagenic potency and organic content of extracts prepared from these particles are both related to mobile and stationary combustion processes. Analyses of the organic extracts prepared from these particulate samples showed the presence of certain polycyclic aromatic hydrocarbons (PAH), certain keto-PAH and thia-PAH. The enhanced magnetic signatures of air particulate material collected in an urban environment are directly related to the presence of magnetite-rich spherules which are likely to have been produced by the oxidation of pyrite to magnetite during the combustion process. A total of 62 filters collected between May 1990 and June 1991 at an air quality monitoring station in Hamilton, Ontario were examined. A plot of magnetic susceptibility of these filters and the mutagenic potencies of the organic extracts prepared from these filters in the Salmonella/microsome assay show a significant correlation. Neither magnetic susceptibility nor mutagenicity show a similar simple direct relationship to particulate loading. Plots of wind direction vs wind speed indicate that the highest mutagenicity and susceptibility levels are predominantly associated with (a) easterly derived winds, (b) low to moderate wind velocities, and (c) enhanced levels of SO2 and NO2. In contrast, low mutagenicity and susceptibility levels are intimately associated with (a) southwesterly derived winds, (b) moderate to high wind velocities, and (c) the presence of high ozone levels which accompany higher summer temperatures. These observations suggest that rapid magnetic susceptibility measurements could be used to pre-select filters for more extensive evaluations such as organic compound analyses or biological assays.