PCDD/Fs Concentration in Air, Fly Ash and Soil around a Municipal Solid Waste Incinerator and its Risk Assessment

The concentrations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in the air and fly ash in a municipal solid waste incinerator (MSWI) in the Pearl River Delta and in the air and soil at the nearest environment-sensitive spot (an adjacent village) were investigated to evaluate PCDD/Fs health risk to on-site workers and adjacent villagers. Human health risk evaluation manual from US Environmental Protection Agency (USEPA) and Monte Carlo simulation were used to evaluate the PCDD/Fs health risk to on-site workers and adjacent villagers (adults, teens and children) under inhalation, dermal and ingestion exposure. The results are as follows. First, the toxic equivalent concentration (I-TEQ) values of PCDD/Fs were 8.99~240.00 ng TEQ/kg in the fly ash after solidification, 0.03~0.20 pg TEQ/m³ in the air, 0.81~2.04 ng TEQ/kg in the soil of the environment-sensitive spot. Second, PCDD/Fs congener profiles in the fly ash, the air in MSWI and the air at the environment-sensitive spot were similar, while PCDD/Fs congener profiles in the soil samples showed a little difference. Third, the 95th percentile carcinogenic risk (CR) values for on-site workers and villagers (adults, teens and children) were 4.55×10^-7~6.04×10^-6, suggesting that the CR values were on an acceptable level (< 1×10^-5); the 95th percentile non-carcinogenic risk values for the four groups of people were 4.61×10^-3~4.28×10^-2, much lower than the threshold values of 1, suggesting a quite low non-carcinogenic risk. Fourth, the 95th percentile CR for on-site workers and adult villagers were relatively high, accounting for 60% and 39% of the risk safety value respectively; inhalation of air (in the MSWI and at the environment-sensitive spot) and accidental ingestion of fly ash contributed most to CR to on-site workers, accounting for 55.12% and 38.43%, respectively; and inhalation of air was the largest contributor of CR to adult villagers, accounting for 97.79%. It is suggested to monitor PCDD/Fs concentrations in the air and controll risk of accidental ingestion of fly ash.