Assessment of the effect of degradation by atmospheric gaseous oxidants on measured annual average benzo[a]pyrene mass concentrations

► A novel method for assessing the effect of on-filter degradation on benzo[a]pyrene (BaP) is presented. ► The method is based on using different sampling periods for ambient particulate matter. ► Assumed pseudo-first order reaction rate kinetics allow calculation of concentration in the absence of degradation. ► Effect on the measured annual average BaP concentration at two monitoring stations in the UK is estimated.