Public fear of dioxins from modern municipal waste incinerators is not justified. (Correspondence).

In spite of the important increase of the three "r's" (reduction, reuse, and recycling) in the management of municipal solid waste (MSW), there are still many places in which incineration continues to be an important option for the disposal and treatment of MSW. Although incineration recovers energy and reduces the volume of waste that requires landfilling, because it also involves the emission of a number of pollutants where incinerators are used or proposed, people are often afraid that resulting pollutants will adversely affect their health. Concern has been especially notable with respect to dioxins and furans. These organic pollutants are toxic in extremely tiny amounts and bioaccumulate in humans (1-5). Moreover, in February 1997 using recent epidemiologic data on exposed human populations and experimental carcinogenicity bioassays in laboratory animals, the International Agency for Research on Cancer (IARC) classified 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD) as carcinogenic to humans (IARC group 1) (6). Recent episodes such as the Belgian PCB and dioxin incident of 1999 (7,8) have contributed to increase the concern with respect to dioxins.

As a direct consequence of a notable growth in the public opinion against the binomial MSW incineration and dioxins, numerous municipal, regional, and national governments have placed a moratorium on construction of new MSW incinerators (MSWIs) and more stringent controls on existing units. The argument against incineration of MSW is mainly based on the following premises: MSWIs emit dioxins, and dioxins are carcinogenic; therefore, MSWIs are carcinogenic facilities. However, in recent years, dioxin emissions from MSWIs have been reduced to levels < 0.1 ng I-TEQ/[Nm.sup.3]. As a consequence of this, the current national dioxin inventories show that in those countries with a stringent regulation of dioxin emissions from MSWIs (e.g., the member states of the European Union) that started legislation in the early 1990s, MSW incineration is currently a minor contributor to any national inventory (9,10).

Taking the above information into account, the main purpose of this letter is to try to abate the fear of dioxins in relation to MSWIs, especially for the population living near these facilities. To reduce total dioxin exposure, a simple change in the dietary habits can be as relevant as the decrease in direct exposure to environmental dioxins in the vicinity of a MSWI. The data shown in Tables 1 and 2 are based on studies from two MSWIs in Catalonia, Spain, in which technical improvements were recently carried out and dioxin emissions were reduced to concentrations < 0.1 ng I-TEQ/[Nm.sup.3] (11,12). To assess human health risks before and after these improvements, the following routes of dioxin exposure were evaluated: direct contact from inhalation of air and particles; ingestion and dermal contact with soil and dust; and indirect exposure (dietary intake). For risk estimations, I assumed the worst scenario (e.g., all dioxins in the neighborhood of the respective MSWI would be emitted by the facility).

For adults living at 500 m from MSWI-1 (Montcada), the direct' exposure m dioxins before technical improvements was 5.102 x [10.sup.-2] pg I-TEQ/kg/day, and the total dioxin exposure was 2.82 pg I-TEQ/kg/day. This resulted in a contribution to dioxins from the MSWI of 1.81%. Two years after technical improvements were carried out, direct exposure to dioxins decreased to 1.271 x [10.sup.-2] pg I-TEQ/kg/day, while the total dioxin exposure diminished to 0.92 pg I-TEQ/kg/day, which results in a contribution to dioxins from the MSWI of 1.36%. This indicates that the important percentage reduction (75.1%) in the direct exposure to dioxins is practically imperceptible when compared with the contribution of indirect exposure (dietary intake) to total dioxin exposure, which decreased from 2.82 (13) to 0.92 pg I-TEQ/kg/day (12) during the same period.

Although people are concerned about exposure through MSWI emissions, diet is the main route of dioxin exposure in humans. With respect in this, the absolute reduction of 0.038 pg I-TEQ/kg/day in the dioxin levels at 500 m from the MSWI-1 2 years after introducing the technical improvements is of the same order of magnitude as a simple change in dietary habits: daily consumption of 300 g of semi-skimmed milk instead of the same quantity of whole milk would result in a reduction in dioxin exposure of 0.021 pg I-TEQ/kg/day (dioxin concentrations in semi-skimmed and whole milk of 0.006 and 0.011 pg I-TEQ/g wet weight, respectively; Table 1). Similar results would be also obtained for those living at 1,000 m from the facility (total reduction from direct exposure of 0.031 pg I-TEQ/kg/day). For adult subjects living at 500 and 1,000 m from MSWI-2 (Tarragona), the decreases in direct exposure to dioxins were 0.016 and 0.013 pg I-TEQ/kg/day, respectively (Table 2), values that are also similar in magnitude to the reduction of 0.021 pg I-TEQ/kg/day derived from a hypothetical consumption of semi-skimmed milk instead of whole milk (Table 1).

For a number of different reasons, strong arguments in favor or against incineration as a way of disposal and treatment of MSW can be justified. However, it seems quite evident that the public concern over the health risks due to exposure to dioxins emitted by modern MSWIs or MSWIs equipped with modern technologies is not scientifically justified. Therefore, decisions regarding the construction or closing of modern MSWIs should not be primarily based on public opinion and fears of dioxin emissions from these plants. Because the diet is the main route of human exposure to dioxins, only efforts to reduce emissions from all sources can significantly contribute to decrease environmental dioxin concentrations, and consequently, their levels in food.

Table 1. Comparison of the reduction in direct exposure to dioxins
with a single change of dietary habits: consumption of 300 g/day
semi-skimmed milk instead of whole milk.

                                               Semi-skimmed
                                   Whole milk      milk      Reduction

Dioxin concentrations in milk        0.011        0.006        0.005
 (pg I-TEQ/g wet weight)
Dioxin intake through milk           0.047        0.026        0.021
 consumption (pg I-TEQ/kg bw/day)
Table 2. Dioxin exposure for adult populations living at 500 and
1,000 m from two municipal waste incinerators (MSWI-1 and MSWI-2)
before and after pronounced reductions in the emissions of dioxins
from the facilities.

                                             MSWI-1

                                      500 m          1,000 m

                                  Before  After  Before  After

Total direct exposure              5.102  1.271   4.087  0.995
 (pg I-TEQ/kg/day) x [10.sup.-2]
Reduction in total direct             0.038          0.031
 exposure (pg I-TEQ/kg/day)
Dietary intake (indirect           2.770  0.903   2.770  0.903
 exposure) (pg I-TEQ/kg/day)
Total exposure to dioxins          2.82   0.92    2.81   0.91
 (pg I-TEQ/kg/day)

                                             MSWI-2

                                      500 m          1,000 m

                                  Before  After  Before  After

Total direct exposure              2.085  0.466   1.721  0.439
 (pg I-TEQ/kg/day) x [10.sup.-2]
Reduction in total direct             0.016          0.013
 exposure (pg I-TEQ/kg/day)
Dietary intake (indirect           2.790  0.907   2.79   0.907
 exposure) (pg I-TEQ/kg/day)
Total exposure to dioxins          2.81   0.91    2.81   0.91
 (pg I-TEQ/kg/day)

REFERENCES AND NOTES

(1.) Bertazzi PA, Consonni D, Bachetti S, Rubagotti M, Baccarelli A, Zocchetti C, Pesatori AC. Health effects of dioxin exposure: a 20-year mortality study. Am J Epidemiol 153:1031-1044 (2001).

(2.) Birnbaum LS, Cummings AM. Dioxins and endometriosis: a plausible hypothesis. Environ Health Perspect 110:15-21 (2002).

(3.) Geusau A, Abraham K, Geissler K, Sator MO, Stingl G, Tschachler E. Severe 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) intoxication: clinical and laboratory effects. Environ Health Perspect 109:865-869 (2001).

(4.) Kimbrough RD, Krouskas CA. Polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans and birth weight and immune and thyroid function in children. Regul Toxicol Pharmacol 34:42-52 (2001).

(5.) Kogevinas M. Human health effects of dioxin: cancer, reproductive and endocrine system effects. Hum Reprod Update 7:331-339 (2001).

(6.) McGregor DB, Partensky C, Wilbourn J, Rice JM. An IARC evaluation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans as risk factors in human carcinogenesis. Environ Health Perspect 106(suppl 2):755-760 (1998).

(7.) Schepens PJ, Covaci A, Jorens PG, Hens L, Scharpe S, van Larebeke N. Surprising findings following a Belgian food contamination with polychlorobiphenyls and dioxins. Environ Health Perspect 109:101-103 (2001).

(8.) van Larebeke N, Hens L, Schepens P, Covaci A, Baeyens J, Everaert K, Bernheim JL, Vlietinck R, De Poorter G. The Belgian PCB and dioxin incident of January-June 1999: exposure data and potential impact on health. Environ Health Perspect 109:265-273 (2001).

(9.) Anderson DR, Fisher R. Sources of dioxins in the United Kingdom: the steel industry and other sources. Chemosphere 46:371-381 (2002).

(10.) UNEP Chemicals. Dioxin and Furan Inventories: National and Regional Emissions of PCDD/PCDF. Geneva:United Nations Environment Programme, 1999. Available: http://irptc.unep.ch/pops/pdf/dioxinfuran/difurpt.pdf [cited 10 April 2002].

(11.) Domingo JL, Schuhmacher M, Llobet JM, Muller L, Rivera J. PCDD/F concentrations in soil and vegetation in the vicinity of a municipal waste incinerator after a pronounced decrease in the emissions of PCDD/Fs from the facility. Chemosphere 43:217-226 (2001).

(12.) Domingo JL Unpublished data.

(13.) Domingo JL, Schuhmacher M, Granero S, Llobet JM. PCDDs and PCDFs in food samples from Catalonia, Spain: an assessment of dietary intake. Chemosphere 38:3517-3528 (1999).

Jose L. Domingo
School of Medicine
"Rovira i Virgili" University
Reus, Spain
E-mail: [e-mail]