Exposure to fine particulate matter (PM2.5) among highway toll station workers in Taipei:: Direct and indirect exposure assessment

In this study, the authors assessed occupational exposure to PM2.5 among 47 highway toll station workers in Taipei, Taiwan. The subjects were monitored for 10 days to assess integrated 8-hr fine particulate matter (PM2.5) breathing zone concentration. Researchers constructed a microenvironment-time-concentration matrix and applied direct and indirect approaches to assess cumulative exposure. Mean PM2.5 concentration for workers in the truck and bus lanes was 308 mu g/m(3) (SD = 115.5 mu g/m(3)), substantially higher compared with cash-payment car lanes (mean 115, SD = 41.8, p < 0.001) and ticket-payment car lanes (mean 109, SD = 48.7, p < 0.001). Concentration per vehicle in the truck and bus lanes was 6.4 and 3.7 times higher, respectively, than that of ticket- or cash-payment car lanes. Mean cumulative exposure for the 10-day period was 4,900-13,407 mu g/m(3) center dot hr, with a mean of 8,019 mu g/m(3) center dot hr (SD = 2,375.3). Indirect and direct concentrations were strongly correlated (r(2) =.61, F(1, 125); p = 0.000). The results of this study show that personal exposure to PM2.5 can be reliably estimated using indirect approaches.