Lead in topsoil, hay, silage and blood of cows from farms near a former lead mine and current smelting plant before and after installation of filters.

This study covers 1975 to 2003 with measurements of lead in soil (n = 24), hay (n = 259), silage (n = 35) and blood of cows (n = 1279) from farms (n = 1 to 14) situated 1 to 10 km around a lead smelter. Until 1978, when protective filters were installed in the plant chimneys, the farms had been exposed to heavy industrial-metallurgic effluent. Early measurments (1968 to 1975) high lead (> 600.0 mg lead/kg) in the topsoil, and continuing measurements (1981 to 2003) showed no significantly decreased lead after the installation of filters; however, mean lead in hay samples gradually decreased. In 1975 lead concentrations in 4 samples of hay were 227.0 to 953.0 mg/kg DM. In 2002 (n = 12) mean lead concentrations were about 100-fold lower (5.6 +/- 3.3 mg lead/kg DM). A similar trend of decreasing lead concentrations occurred also in the blood of cows. In 1975 (n = 9) average lead concentration was 1.2 +/- 0.6 mg/kg whole blood, while in 2002 (n = 58) it was about 20-times lower (0.07 +/- 0.005 mg/kg). This significant decrease in lead concentration may be attributed to sanitation of the major source of industrial emission of lead gasses and dust by installation of bag filters to the plant chimneys in 1978. After 1982 mean cow lead blood concentrations were within normal reference values (< 0.250 mg of lead/kg). However, during the last 10y mean lead concentrations have still been 1- to 2-fold above the values measured in blood (n = 32) from 3 control areas in Slovenia. Cattle blood levels proved a good bioindicator of environmental contamination. Monitoring lead in the blood of animals on farms near the smelter should continue because the persistence of lead in topsoil is the main problem in this area.