2-6 Environmental Monitoring of Heavy-Metals and Dioxins ear a Municipal Solid waste Incinerator in Taiwan

 Kuen-Yuh Wu
Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Koahsiung, Taiwan

Incineration is widely used in the treatment of municipal solid waste treatment in Taiwan because of its effectiveness in reducing the amount and the volume of waste and the possible recovery of exothermic energy. Incineration of municipal waste is known to emit various atmospheric pollutants including toxic elements and organic compounds. The primary concern on the risks of emissions from incinerators are heavy metals and polychlorinated dibenzo-p-dioxins and dibenzfurans (PCDD/Fs) (Valberg et al., 1996; Mukerjee, 1998; NRC, 2000). At present, municipal solid waste incinerators (MSWIs) are considered to be the major sources of PCDD/Fs emission in many countries (Bolt and Jong, 1993; Coleman et al., 1997; Ogura et al., 2001). Dioxins and furans, two of the 12 environmental hormones are classified as a human carcinogen by IARC and can cause numerous health effects.
In addition, heavy metals are one of the major classes of pollutants emitted from incinerators (NRC, 2000; Forestier and Libourel, 1998). Metals, such as Pb, Cd, V, Cr, Ni, and Mn could cause toxic health or environmental consequences when their exposure levels were highly elevated (Natusch et al., 1974; Hlavay et al., 1992). Epidemiological studies demonstrated that metal emissions from waste incineration were associated with significant elevated metal concentrations in blood and possibly contributed to a high death rate of gastric cancer (Hu and Shy, 2001). Metals were also known to contribute to the production and release of inflammatory mediators by the epithelium (Carter et al., 1997). Furthermore, metals associated with both the water-soluble and insoluble fractions of ambient particles have been reported to cause oxidative stress leading to cellular injuries (Prahalad et al., 2001).
In order to protect the public from adverse health effects caused by MSWIs, regulations on MSWI emissions require stack sampling once or twice per year. Although most released by Taiwan EPA showed compliance to current regulations, air disperse modeling always gave dramatically difference in numbers of dioxin concentrations when compared with data from field sampling. This study was designed to systematically collect ambient air samples near an incinerator at central Taiwan. Ten sampling locations were selected based on air disperse modeling (ISCST3). Every two samplers were located at upwind, downwind, and right and left-hand direction at 1 – 3 km from the incinerator, and additional two samplers were located at 6 and 10 km from the incinerator at downwind direction. Sampling was conducted in the January of 2002 according US EPA reference methods. Sample dates, volume, temperature, and relative humidity were recorded. Details of samplers used, sampling, metal and dioxin analysis are referred to our published papers ((Hu et al., 2003, Chao et al., 2003, and Chao,et al., 2004) 。
    After completion of sample analysis, comparison of our dioxin concentrations with ISCST3 modeling results showed dramatic differences if 0.1 ng/m3 was used as an input for model. Then, dioxin concentrations were adjusted for the background concentration of dioxins by using the lowest concentration at the upwind direction (at 3 km from the incinerator). There were greater than one order of differences in dioxin concentrations between our data and model outputs. Although one order of uncertainty of this model has been considered acceptable when this model was used model the spatial distribution of pollutants above simple terrain, our data still demonstrated dioxins might have significant impact on its surrounding environments.

The sizes of particle-bound dioxins shift from 1.1 km to 2.1 km were observed at the first time (Figure 1), and the increase in particle sizes was associated with chlorination of furans and dioxins (Figure 2). Figure 1 shows sizes of particle-bound dioxins increased from site C to site D. Figure 2 shows that there were the greatest increases in sizes of particle-bound Cl8DF and Cl8DD from closer sites to further site. These results might imply that the dioxin emitted from an incinerator did not reach equilibrium. Some unknown mechanisms might be responsible for the redistributions of dioxins when they were transported away from the incinerator. This observation was further proved by the shift of dioxin partition coefficients (solid-to-gas phase) from closer sites to further site (Figure 3). The 17 cogners of dioxins were frequently used as the fingerprint for identification of sources of emitted dioxins. The concentration profiles at the upwind (site A and B) and downwind (site C and D) directions within 3 km from the incinerator were similar to those emitted from the incinerator stack (Figure 4). The comparison of dioxin fingerprint indicated that the background concentration might have been overestimated when dioxin concentration at site A was used for adjustment for background concentration.

    For ambient metal pollutants, metal samples were collected at 8 sites within 3 km from the incinerator, and 16 species of them were analyzed and compared with those in stack emissions. Figure 5 shows that 7 0f 8 profiles of 16 metal concentrations were similar to those in the stack emissions. Actually, sizes of particle-bound metals also increased from site C to site D especially for As and Cd (data was not shown).

Figure 5. Comparison of concentrations of 16 metal species collected at 8 sites within 3 km and in the stack emissions of the incinerator.

In conclusions, our studies demonstrated that the emissions from a large-scale incinerator could have significant impact on its surrounding environments. Further systematically environmental monitoring may be required to evaluate the impact of the hazardous emissions from the incinerators in Taiwan.

Footnote: This paper was not subjected review by the Division of Environmental Health and Occupational Medicine (DEHOM) of National Health Research Institutes (NHRI), Taiwan. It only represents the opinions of the author, not the policy or advertisement of DEHOM of NHRI.



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