HUMAN EXPOSURE TO POLYHALOGENATED HYDRO-CARBONS AND INCIDENCE OF SELECTED MALIGNANCIES

Abstract

ISEE-158 Introduction: A population based cross sectional study (PCB Risk 5th FP) confirmed higher exposure of the local population of the Michalovce District, Eastern Slovakia region, to PCBs, due to the previous production of PCBs in a local chemical plant (1959 – 1983, 21 500 metric tons) (Koěan et al. 2001; Trnovec et al. 2004).Aim: Due to inconclusive and sometimes even contradictory findings concerning carcinogenicity of polyhalogenated hydrocarbons (Bencko 2003; Pavúk et al. 2004) we decided to analyze the incidence of selected malignancies in the exposed population, using data available in the Slovak National Cancer Registry database (established in 1975) for Slovakia (∼ 5 M inhabitants), in comparison with the population of Michalovce District (∼ 55 000 inhabitants). The Michalovce District is recognized as one of the world areas most heavily polluted with PCBs. The analyzed period represents 10year interval of 1987-1996. Methods: Age adjusted (world standard ratio – WSR) incidences of the following tumours were compared for the Michalovce District WSR and Slovakia data: thyroid, pancreas, breast, ovarium, bladder, and brain tumors (in females) and thyroid, pancreas, breast, bladder, brain, prostate and testes tumours (in males). Study base for Slovakia for the follow up period of 1987-1996 represents 50 M person-years and for Michalovce District ∼ 0.55 M person-years. For calculation of statistical significance, paired two sample t-test for means were used (STATISTICA 6.0 software). Results: PCBs or PCDFs do not appear to be likely causal agents for the observed lower incidence of breast and possibly prostate cancer in the Michalovce district. This, in spite of the higher PCB levels in this district. However, based on the anti-estrogenic properties described for hydroxylated and methylsulfonyl PCB metabolites, such a mechanism of action may be a feasible pathway for the observed lower incidence of breast tumours in the Michalovce district. Conclusion: Further studies on the occurrence of these metabolites in the blood of exposed populations could clarify a possible role for PCB metabolites as anti-estrogenic agents in humans. This study was supported by the 5th FP Project Evaluating Human Health Risk from Low-dose and Long-term PCB Exposure (PCBRISK) QLK4-2000-00488 and CASCADE NoE 6FP EC.