[Thyroid hormone level in children in the area of a toxic waste incinerator in South Essen]

Abstract

As part of an environmental epidemiological study on potential exposure to a toxic waste incineration we investigated whether children in an area with a toxic waste incinerator (TWI) have different levels of thyroid hormones than children in two comparative regions. The TWI region is situated in the Rhine valley (about 30 km across) with low mountains on both sides. Other industries such as a chemical plant are nearby, and several municipalities are located in the environment of these. One comparative area 20 km north is also industrially and agriculturally used, but has no incinerator (Rhine Valley comparison group, RVC group). South-East of the incinerator region in an area of low mountains (about 400 m high) we investigated the second comparison group (Odenwald comparison group, OWC group). Altogether 671 children from 18 municipalities participated in 1994/95 (participation 61.5%). Blood samples were taken from 341 children, aged 7 to 10 years, living in non-smoking households or in households with only light smokers. Serum levels of thyrotropin stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) were analysed. In a self-administered questionnaire for the parents, which was checked during the medical examination, we gathered information on age, gender, passive smoking, consumption of fish, as well as use of wood preservatives and pesticides at home. By means of adjusted regression analysis the first step was to check whether the TWI group had means of TSH, FT4 and FT3 that differed from the OWC group and the RVC group. If differences were at least marginally significant, the second step was to analyse whether children from different municipalities had statistically different mean values and if the pattern of these municipalities fitted into the three regions. For the latter, children from a town in the Odenwald served as comparison group. The TWI group had statistically significantly (p < or = 0.05) reduced FT3 and FT4 values with a higher prevalence of FT3 values below clinical references (TWI group: 7.7%, RVC group: 3.2%, OWC group: 1.2%). Children from four out of nine TWI municipalities showed statistically significantly lower FT3 means than children from the reference town, and one of the seven municipalities from the comparative areas. The mean FT4 was significantly lower in four municipalities of the TWI area and in one of the two other areas. The mean TSH was only marginally different, mainly influenced by gender differences with boys having higher TSH levels. Comparison of the municipalities did not reveal a consistent pattern. Industrial pollution might influence the regulatory system of the pituitary thyroid axis. Reduced peripheral thyroid hormones associated with exposure to polychlorinated biphenyls (PCB) and dioxins/furans (PCDD/F) were found in previous studies. Our results suggest that children exposed to toxic waste incineration in their environment have lower thyroxine and triiodothyronine levels.