Arsenic Concentrations in Water, Soil, Milk and Forage in Comarca Lagunera, Mexico

Arsenic levels were determined in seventy three samples of well water, and in fifty samples of soil, forage and cow’s milk collected at the most important dairy farms of the Comarca Lagunera located in Coahuila and Durango, Mexico, region naturally rich in As. The total inorganic arsenic concentration in well water ranged from 7 to 740 μg L−1 and about ninety percent of the total arsenic was found as As(V). The agricultural soil texture of the sampled area was sandy clay loam type with total arsenic levels up to 30 μg g−1, however, the extractable arsenic was not higher than 12% of the total and it was higher in the 0–30 cm depth horizon. In alfalfa, the most important crop, the total aresenic ranged from 0.24 to 3.16 μg g−1, with 40% of it accumulated at the root level. Significant correlations (p=0.05) were obtained between arsenic (III), (V) and total inorganic arsenic in groundwater with arsenic in soil (0–30 cm depth), and with arsenic in alfalfa (leaves and roots). It was also found a good correlation between extractable arsenic in soil with As concentrations in alfalfa (roots). Arsenic concentrations found in milk ranged from <0.9 to 27.4 ng g−1. The cow’s milk biotransfer factor for arsenic was up to 6 × 10−4, applying a pharmacokinetic approach. It was associated with the exposure not only to food but also to water arsenic.