The relative contribution of BaP to the overall carcinogenic potency of
the PAH mixture is similar indoors to outdoors and similar to the smelter
environment previously linked to excess cancer incidence which wasused by EPAQS to derive the UK Air Quality Standard. The relative BaP
contribution is also independent of PAH sources such as traffic, ETS or the
use of a fireplace for space heating. These results suggest the suitability of
benzo(a)pyrene as a marker for the carcinogenic potential of the PAH
mixture independent of the environment.