The variation in exposure to toxic metals over time is still not well-characterized, especially in children, the most vulnerable group. The aim of this study was to evaluate whether a reduction in environmental pollution with cadmium (Cd) and mercury (Hg) caused a change in exposure over time in two Swedish cities. For this, 1,257 children between the ages of 4 and 9 from Landskrona and Trelleborg, in the south of Sweden, were sampled once during 1986-2013. Cd (n=1120) and Hg (n=560) concentrations were determined in blood (b-Cd, b-Hg). The median b-Cd was 0.10 (geometric mean 0.10; range 0.01-0.61) μg/L and b-Hg was 0.91 (geometric mean 0.83; range 0.02-8.2) μg/L.

No sex or age difference was seen in b-Cd or b-Hg. Regarding the cities, children living in Landskrona close to a smelter had higher b-Cd and b-Hg than those living in urban and rural areas. Over the studied time, b-Cd slightly decreased (0.7% per year, p<0.001) while b-Hg showed a marked decrease (3% per year, p<0.001).

In conclusion, exposure to Cd was low during the ages 4 to 9, but the risk of disease might increase later in life since b-Cd only showed a minor decrease over time. This indicates, that Cd pollution should be further restricted. Regarding Hg, b-Hg concentration in children was low and decreased over time. The decrease is probably due to the reduced use of dental amalgam and the lower Hg intake from fish.