The aim of the present project was to assess population exposure to pesticides in the vicinity of pesticide dump sites and make a preliminary evaluation of the potential health hazards to humans. Of the 286 pesticide dump sites registered in Poland, 40 were selected as the largest source of ecological hazard. The application of the Hazard Ranking System made it possible to identify 17 priority dump sites where pesticide wastes are deposited. For population exposure assessment, two dump sites located close to the residence area and drinking water intakes were selected as potentially most hazardous to health. They have a piezometric system installation that enables ground water sampling for analysis. In water samples collected from the water-bearing layer in areas adjacent to pesticide dump site, 31 different pesticides in total have been detected (15 organochlorine pesticides, 10 organophosphorous pesticides and 6 phenoxyacids), 12 of which - dichlorvos, mevinphos, endosulfan, dieldrin, heptachlor epoxide, p,p'-DDT, p,p'-DDD, p,p'-DDE, methoxychlor, 2,4-D, MCPA, MCPP--had concentration levels higher than the detection limit. The estimated size of the potentially exposed population approximates 900 inhabitants; 33% of this population are children (aged 0-14 years) and women at reproductive age (aged 15-45 years). Both these target populations are considered particularly susceptible to the adverse health effects of pesticides. Assessment of population exposure to pesticides (p,p'-DDT - 0.15 microg/l; p,p'-DDD - 0.13 microg/1; MCPP - 12.3 microg/l; MCPA - 0.64 microg/l; methoxychlor - 0.31 microg/l; 2,4'-D - 5.4 microg/l) with concentration levels higher than the drinking water standard (0.1 microg/1) was based on pesticide daily intake in drinking water. The results indicated a low cancer risk (R = 10(-8)) for people drinking water contaminated with p,p'-DDT and p,p'-DDD as well as low non-cancer risk related to MCPA, MCPP and methoxychlor exposure. At one of the dump sites examined, the level of population exposure to 2,4'-D implies possible hematopoietic, nephrotoxic and hepatotoxic effects as well as reproductive disorders.