Abstract Background A previous study revealed an environmental contamination by heavy metals in the vicinity of two non-ferrous metal plants in Ath, Belgium. The purpose of the current cross-sectional study was to estimate exposure of the population to heavy metals in the vicinity of the plants, in comparison with population living further away. Methods We did a random sampling in the general population of Ath in two areas: a central area, including the plants, and a peripheral area, presumably less exposed. We quantified cadmium, lead, nickel, chromium and cobalt in blood and/or urine of children and adults in three age groups: (i) children aged 2.5 to 6 years (n = 98), (ii) children aged 7 to 11 years (n = 74), and (iii) adults aged 40 to 60 years (n = 106). We also studied subclinical health effects by quantifying retinol-binding protein and microalbuminuria, and by means of a Strengths and Difficulties Questionnaire. Results We obtained a participation rate of 24 %. Blood lead levels were significantly higher in young children living in the central area (18.2 μg/l ; 95 % CI: 15.9–20.9) compared to the peripheral area (14.8 μg/l ; 95 % CI: 12.6–17.4). We observed no other significant mean difference in metal concentrations between the two areas. In the whole population, blood lead levels were higher in men (31.7 μg/l ; 95 % CI: 27.9–36.1) than in women (21.4 μg/l ; 95 % CI: 18.1–25.3). Urine cadmium levels were 0.06 μg/g creatinine (95 % CI: 0.05–0.07), 0.21 μg/g creatinine (95 % CI: 0.17–0.27), and 0.25 μg/g creatinine (95 % CI: 0.20–0.30) for children, men, and women, respectively. Conclusions Despite higher blood lead levels in young children living close to the plants, observed metal concentrations remain in the range found in other similar biomonitoring studies in the general population and are below the levels of concern for public health.