N.J. Themelis, and P. Deriziotis Earth Engineering Center, Columbia University, 500 West 120 t h Street, New York, NY 10027, USA

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1 11th North American Waste to Energy Conference 23 by ASME NAWTEC SUBSTANCE AND PERCEPTONS OF ENVRONMENTAL MPACTS OF DOXN EMSSONS: AN NTERM REPORT N.J. Themelis, and P. Deriziotis Earth Engineering Center, Columbia University, 5 West 12 t h Street, New York, NY 127, USA Abstract The emission of dioxins is perceived widely as a major environmental impact of combustion processes. This paper will report the results of an extensive study of published data on a) the rate of formation of dioxins from all U.S. sources; b) the pre-mact and post-mact performance of individual Waste-to-Energy (WTE) plants in the U.S. and how post-mact emissions compare with the 1998 EU standard (.1 ng/dscm); c) how the contribution ofwtes has changed with time; and d) the measured impacts ofwte dioxin emissions on soil/plant concentrations and on public health. The study has shown that since 1987 the U.S. dioxin emissions have decreased by a factor of four and by now WTEs are a miniscule source. Also, that even at the earlier high emission levels, the dioxin levels in soil samples close to WTE facilities did not exhibit an increase over regional background concentrations. Finally, the paper contrasts public perceptions of the dioxin threat with scientific studies of observed effects on the environment and on public health. Please note: This is not a complete paper but an interim report on some of the findings of this study. The results of the study will be presented at NA WTEC 11 and a full paper will be published at a later time. Background nformation Polychlorinated dibenzo-dioxins, dibenzofurans and related components are some of the most rigorously studied substances in the modem epidemiology and toxicology. Of the 21 compounds identified, only 17 are considered toxic. Chemical analysis of dioxin concentrations in stack gases measures all dioxin and furan compounds in the gas. As noted above, most of these compounds are not toxic. Therefore, World Health Organization has measured the toxicity of each known dioxin and furan (about 175 different compounds) and has established toxic equivalence factors (TEF) that relate the toxicity of each compound on a scale of to 1, where 1 is the most toxic dioxin known. On the basis of these factors, and the prevailing distribution of different types of dioxins and furans in the flue gas of WTE plants, EPA has established that the prevailing ratio of total to toxic dioxins is approximately 5. Accordingly, 5 grams of total D /F emissions correspond to about 1 gram of toxic equivalent (TEQ). The tmucity of dioxins has been proven by numerous animal studies. However, the lethal dose of the most toxic compound, 2,3,7,8- TCDD, has been found to vary by more than sooo-fold between the most sensitive, and the least sensitive species [Fiedler et al. 2]. These results have resulted in a great deal of uncertainty amongst the scientific and medical community about assessing health risks for the general public. The chemical, biological, and physical resistance of dioxins and thus their tendency to accumulate ill the environment and ill orgarusms have forced national and international authorities to ssue strict regulations. These are based on laboratory studies on animals the results of which are extrapolated to low doses for human use, applying different mathematical models. The diversity and ambiguity of the outcomes can be illustrated by the different Tolerable Daily ntake (TD!) levels imposed by various 225

2 agencies. The European Commission's Health and Consumer Protection Directorate (21) is suggesting a ill level of 2 picograms (1-12 gram) TEQ/kg of body weight/day, the Ministerial Council on Dioxin Policy of Japan (1999) 4 pg TEQ/kg,, Health Canada (1996) 1 pg TEQ/kg, the US Agency for Toxic Substances & Disease Registry (2) 1 pgteq/kg, and the World Health Organization (1998) a ill level between 1 and 4 pg TEQ/kg of body weight/day (Figure 1). 1 9 i;- 8 C) 7 1 f 6 5 ' 4 CJ O r-----' '----'-----T US Agen:y for World Health ELropean Ministerial Cooocil World Health Health Calada Toxic Slbsta>ces Orgcrization [M in) ColTTnission's on Dioxin Policy of Orgcrizatlon (1196) & DiseraseRegistry (1198) Health<n:1 Japan (1199) [Max) (1198) (2) COlSUl'lW Protection Directorate (21) Figure 1. Tolerable Daily ntake of Dioxins established by various health agencies Human Exposure Pathways ngestion of food accounts for about 9% of total human exposure to dioxins [WHO 199]. The World Health Organization has assessed that the average daily intake is approximately 2 pg TEQ/kg of body weight/day. [UNEP 1999]. Background exposure for industrialized countries such as The Netherlands and Germany is 1 pg TEQ/kg of body weight/day for adults [UNEP 1999]. Children in Netherlands were exposed to 2.4 pg TEQ/kg of body weight/ day according to Liem and also Van Cleuvenbergen [Liem et al., 1991 ; Van Cleuvenbergen et a., 1993]. On the other hand, U.S.E.P.A. has estimated the median background exposure in the U.S. to be in the range of.5 to 1. pg TEQ/kg of body weight/ day [US EPA 2]. Due to their lipophilic nature, dioxins are concentrated in foods that contain animal fat such as beef, pork, poultry, fish, dairy products and eggs. ngestion of such foods is the primary pathway of exposure for the general public. ngestion of contaminated matter results in the in the absorption of 3% to nearly 1% of the contained dioxins 226

3 [pohl H., 1995; US EPA 1994]. Food from animals raised near dioxin sources is likely to have contamination levels orders of magnitude higher than background levels. The food ingested by farm animals includes up to 7% by weight of soil, thus transferring ground contamination to the food chain. Various studies have concluded that populations living in areas with high dioxin concentration are not affected if they do not consume locally produced foods [Nouwen et al. 21; USEP A 1994]. Dioxin-like compounds accumulate in human fat tissue and due to their high stability are inadequately metabolized and thus stored for prolonged periods of time. The dioxin half-life in the human body has been calculated to be 6 to 12 years [Wolfe WH, et al. 1995; Michalek JE, et al. 1992]. nhalation is considered to be a small exposure pathway, mainly because of the low concentration of dioxins in the air and the absence of an accumulating mechanism. Dioxin contamination is usually associated with carcinogenic, reproductive, developmental and immunologic effects although no sufficient evidence has been presented to establish a direct link. The nstitute of Medicine [1M 1996] in a study of the "agent orange" chemical concluded that there is adequate evidence that links dioxin with increased risk of chloracne, Hodgkin's disease, Non-Hodgkin's lymphoma, and soft tissue sarcoma. Chloracne is one of the first symptoms of dioxin exposure and was the only symptom reported after the Seveso, taly accident in 1976 where residents of the surrounding area were exposed to the highest levels of TCDD known to human. nterestingly chloracne did not appear to all persons exposed to similar levels of dioxin. Table 1. Sources of dioxin emissions in the U.S., (U.S. EPA) Recorded 1987 Emissions 1995 emissions 22 emissions Sources of dioxins reported by EPA reported by EPA estimated by EPA grams % of grams % of Grams % of U.S. TEQ U.S. TEQ U.S. TEQ Waste-to-Energy Plants (MSW) Backyard refuse barrel burning Medical waste incineration Secondary copper smelting Cement kilns (haz. Wastes) Sewage sludge (land applied) Residential wood burning Coal-fired utilities Diesel trucks Secondary aluminum smelting ron ore sintering ndustrial wood burning Bleach pulp &paper mills All other U.S. TOTAL U.S % % % % % % % % 7.63% % % 3.27% % % % % % % % % % % % % % % % % % % % 28.87% % % % % % % 1.36% % % 1 9.4% 13,998 1.% 3,225 1.% %

4 Contribution of WTEs to Dioxin Emissions Table 1 is based on EPA published data of TEQ emissions from all measured sources of dioxins. t should be noted that dispersed or unknown sources of emissions, such as forest fires, landfill emissions and flaring of methane emissions from landfills and oil/gas production and refining are not included. Table 1 shows that the U.S. waste-to-energy has moved from being the major source of dioxins in 1987 (8,877 TEQ grams or 63% of total dioxin sources measured), to being a minor source in 22 (12 grams or 1.8% of U.S. total).figures 1 and 2 illustrate this trend graphically. By 22, the predominant sources were backyard barrel burning and residential wood burning. Figure 3 shows the cumulative annual emissions of dioxins from the 35 largest WfEs. The calculation for each plant (shown by dots in Figure 3) were based on the EPA report of nanograms TEQ per cubic meter of flue gas multiplied by the average volume of gas emitted per ton of MSW processed and multiplied by the annual tonnage processed in a plant. The diagonal line represents the allowable dioxin emissions on the basis of the E.U standard of.1 nanograms per cubic meter. t can be seen that the cumulative emissions of u.s. plants are below the European standard. Figure 2 :Dioxin Sources 1% 9% o Residential wood burning 8% 7% 6% 5% 4% 3% 2% 1% Cement Kilns Cl Oher Pulp and Paper o Backyard Barrel Burning o Met al Smelting ncineration (M edical, Hazardous) O\fVTE %

5 Figure 3: U.S. Dioxin Sources 1% 9% 8% 7% 6% 5% 4% Cement Kilns o Other Pulp and Paper Backyard Barrel Buming or., eta! Smelting 3% 2% 1%.ncineration (M edical, Hazardous) owte % Figure 4: Cumulative dioxin emissions (in grams TEQ) ofd.s. WfE plants in 2 (U.S. EPA); each dot represents a WfE plant 14 POST -MACT PERFORMANCE OF US WTE PLANTS (EPA, 22) EU standard 1/1 c: "'iii 1/1 E.. W >< t!! 1/1 E f "SC E :::J u en ::::i )!,?' f, Cumulative Processing Rate, million metric tons/year 229

6 The bar chart of Figure 4 compares the pre MACT and Post- Mact emissions of thirty five largest WTE plants, reported here as nanograms of TEQ emissions per cubic meter of flue gas. t can be seen that most plants were below the European standard, established in 1998, of.1 ng/m3. Also, on the basis that on the average, U.S. WTEs emit about 5, cubic meters (dry, NTP conditions) per ton of MSW combusted, one can calculate readily that the dioxin emissions amount to less than.5 TEQ grams per million tons of MSW. Figure 4: WTE Dioxin Reductions UJ c:. 6 "' - -(1.n.5 g'oa is.3 PRE-MACT AND POST MACT PERFORMANCE.2 19 EW 51""'!;'; "" \4 L L, :, L 1 l1 * L ' [R., FACLTES 23