Impact of environmental contamination by toxic elements on cattle 30 years after lead mine and smelter closure in Upper Meža Valley in Slovenia

This study was carried out to determine the levels of lead, cadmium, arsenic and mercury in the feed, blood, and milk of dairy cows from the Upper Meža Valley in Slovenia. The samples were collected in spring and autumn 2017 from farms located within a 10 km radius of a former lead mine and smelter. A total of 50 feed samples and 108 blood and milk samples were analysed using inductively coupled mass spectrometry (ICP-MS). The lead and cadmium content in the feed did not exceed the maximum levels specified in European legislation, while the mercury concentrations were below the detection limit (0.007 mg kg^-1dry matter). However, one sample of grass silage had an arsenic concentration that exceeded the permitted limit (4.71 mg kg^-1), while all other feed samples remained within the permitted thresholds. Cadmium and arsenic were not detected in the blood samples; while mercury concentrations varied between < 0.002 and 0.020 mg kg^-1 wet weight. The mean blood lead level was 0.034 mg kg^-1 wet weight and was lower than the levels found in previous studies in this region. A significant correlation was found between lead concentration in blood and milk (<i>p</i> < 0.001). Lead was detected in 96.3% of the milk samples (<i>n</i> = 108). In three of these samples, the lead content exceeded the EU maximum level for milk of 0.020 mg kg^-1. Cadmium and arsenic were not detected in the milk samples, while mercury levels were low and ranged from < 0.002 to 0.006 mg kg^-1.