The Salmonella/microsome assay is the most used assay for the evaluation of air
particulate matter (PM) mutagenicity and a positive correlation between strain
TA98 responses and benzo[a]pyrene (B[a]P) levels in PM has been found. However,
it seems that the major causes of PM mutagenicity in this assay are the nitro and
oxy-PAHs. Salmonella YG5161, a 30-times more responsive strain to B[a]P has been
developed. To verify if YG5161 strain was sufficiently sensitive to detect
mutagenicity associated with B[a]P mutagenicity, PM samples were collected in
Brazil and Sweden, extracted with toluene and tested in the Salmonella/microsome
microsuspension assay. PAHs and B[a]P were determined and the extracts were
tested with YG5161 and its parental strain TA1538. The extracts were also tested
with YG1041 and its parental strain TA98. For sensitivity comparisons, we tested
B[a]P and 1-nitropyrene (1-NP) using the same conditions. The minimal effective
dose of B[a]P was 155 ng/plate for TA1538 and 7 ng/plate for YG5161. Although the
maximum tested dose, 10 m(3) /plate containing 9 ng of B[a]P in the case of
Brazilian sample, was sufficient to elicit a response in YG5161, mutagenicity was
detected at a dose as low as 1 m(3) /plate (0.9 ng). This is probably caused by
nitro-compounds that have been shown to be even more potent than B[a]P for
YG5161. It seems that the mutagenicity of B[a]P present in PM is not detectable
even with the use of YG5161 unless more efficient separation to remove the
nitro-compounds from the PAH extract is performed.FormasAccepte
