The mean PCDD/F concentrations in ambient air, banyan leave and soil nearby the Chiayi municipal solid waste incinerators (MSWIs) are 0.0425 pg I-TEQ/Nm3, 2.18 ng I-TEQ/kg and 0.728 ng I-TEQ/kg, respectively. Based on the PCDD/F concentrations of the three matrices determined at sites upwind and downwind, it was found that the environmental impact of the investigated MSWI was not obvious. PCDD/F concentration isopleths of the three environmental compartments coupled with wind rose of the region proved that the influence of the MSWI on the environment was also rather limited. Consequently, we can conclude that the PCDD/F emission from the MSWI do not have significant impact on the ambient atmosphere.
Comparing the PCDD/F I-TEQ concentrations in the ambient air of the selected MSWIs in this study with various areas in Taiwan, we found that the investigated PCDD/F level in ambient air has the loweest PCDD/F I-TEQ concentration. The above results for associated toxicity were significantly lower than 0.6 pg I-TEQ/Nm3, which was the dioxin emission standard in Japan. In addition, the dioxin levels of ambient air, vegetation and soil nearby Chiayi MSWI are lower than those reported in previous study by Taiwan EPA in 2002. The above results indicate government regulation on dioxin emission did inhibit the emission of PCDD/Fs from MSWIs.