Changes in selenium, zinc, copper and cadmium contents in human milk during the time when selenium has been supplemented to fertilizers in Finland

Sodium selenate has been supplemented to all agricultural fertilizers used in Finland since 1984. We followed the changes in selenium, cadmium, zinc a nd copper content in Finnish human milk between the years 1987 and 1993-199 5. A total of 257 milk samples was collected, four weeks after delivery, in two areas: In Helsinki, an urban area, and in Kuopio, a rural area, where elevated copper concentrations have been found in the bedrock. Direct atomi c absorption spectro photometric methods without digestion were used for th e analyses. The dependence of trace element content on study time, living a rea, smoking habits, fish eating frequency, and parity of mothers was studi ed by analysis of covariance. Inter-element correlations and correlations w ith mothers' age and fat content in milk were studied by partial correlatio n. Significant increases were observed in mean selenium (16.4 mug/l and 18. 9 mug/l, p < 0.001) and in fat contents (3.4% and 4.0%, p < 0.001), whereas significant decreases were seen in mean zinc (3.00 mg/l and 1.47 mg/l, p < 0.001), copper (0.52 mg/l and 0.43 mg/l, p < 0.001) and cadmium contents ( 0.095 mug/l and 0.062 mug/l, p < 0.01). In 1987, zinc had a positive correl ation with copper and fat. Copper correlated inversely with the mothers' ag e. In 1993-1995, selenium correlated positively with copper, and zinc corre lated inversely with mothers' age. Mothers Living area had an effect on cop per content in milk. Our results confirm that selenium supplementation to f ertilizers in Finland has increased the selenium Level in human maternal mi lk and most Likely it also has an effect on the zinc and copper concentrati ons in maternal milk.