PRESENCE OF HEAVY METALS IN RAW BOVINE MILK FROM MACHACHI, ECUADOR

The presence of heavy metals in milk is an indicator of local environmental contamination. The objective of this investigation was to test raw milk from Machachi, Pichincha Province, Ecuador for the presence of lead, mercury, and arsenic. Fifty eight samples were collected from twenty nine dairy farms with extensive grazing systems located up to one kilometer from the Municipality of Machachi. Machachi is a site of industrial activity and is located near the Panamericana Sur highway. The samples were analyzed using atomic absorption spectrophotometry with a hydride generator (mercury and arsenic) and a graphite furnace (lead). All analyzed samples indicated the presence of lead, with an average abundance of 0.208 mg kg-1 (range between 0.0016 to 0.719 mg kg-1. Of these samples, 98.28% (57/58) contained lead at levels higher than the maximum allowed by the NTE INEN 9, 0.02 mg kg-1. Mercury was detected in four samples with a mean abundance of 0.00009 mg kg-1 (range between 0.00 to 0.002 mg kg-1; and arsenic was detected in two samples with a mean abundance of 0.00003 mg kg-1 (0.00 to 0.001 mg kg-1. Although these levels are very low, they remain worrisome because these carcinogenic elements are capable of accumulating. Based on these results, it can be concluded that lead contamination has occurred in the studied area. Furthermore, the detection of arsenic and mercury, two highly toxic substances, warrants continuous monitoring of the regional milk supply and a search for possible sources of contamination.