A modified fractionation scheme involving acid-base partitioning and silica gel column chromatography has been used as the first step in the bioassay-directed search for significant levels of mutagenic compounds in extracts of inhalable (IP10) ambient air particulates. The biologically "hot" fractions were separated and analyzed chemically or subfractionated to isolate and concentrate "hot" subfractions which were then chemically analyzed by GC/MS FTIR, and HPLC equipped with UV, Fluorescence and Photodiode Array UV detectors.

The Ames assay of mutagenicity has involved the unactivated TA98 strain of Salmonella and enzyme-activated (TA98+S9) assays. In addition, some assays have been performed in this present study using TA98NR (TA98-nitroreductase deficient) and TA98DNP (TA98-dinitropyrene reductase deficient). In essence, we are using mutagenicity as our chromatographic detector to pinpoint the most active fractions and compounds which are responsible for carcinogenicity in the air, and then monitor them as well as assess their reactivity.

The comparison of winter and summer samples indicate that the profiles are similar in these two periods. However, levels of polycyclic aromatic hydrocarbons (PAHs) are significantly greater in winter as compared to summer. In addition, nitro-PAHs are found at levels approximately an order of magnitude lower than the PAHs.