Cadmium and lead in bovine milk in the mining area of the Caudal River (Spain)

The levels of cadmium and lead in 36 raw bovine milk samples were analysed. These samples come from seven farms with a semi-extensive grazing system and were collected between the autumn of 2007 and the winter of 2008. All the farms were located in Asturias (Spain), a zone of great industrial and mining activity in the proximities of the Caudal River. The samples were collected in sterile precleaned polypropylene tubes and frozen until the analysis. After a lyophilization process, the samples were treated with nitric acid and microwave treatment. Cadmium and lead determinations were carried out using inductively coupled plasma mass spectrometry with sensibility under 0.2 ppb for liquid matrix. The lead content was found to vary from 0.71 to 16.06 μg/kg wet weight (w.w.), and the cadmium was lower than 2 μg/kg w.w. The levels of lead in milk are higher in those farms near zones of storage of mining waste depots, thermal power and areas with high levels of traffic. All the values found are in concordance with research carried out at non-polluted areas, and those for the lead are well below the European Union limitations.