The concentration of heavy metals (Cd, Cu, Cr, Fe, Hg, Pb, Zn) and arsenic was determined in water, soil and alfalfa samples in three sites (Congata, Uchumayo and Vitor) located along the Quilca - Vitor - Chili River, near the city of Arequipa, Peru. The content of these elements was also analysed in samples of alfalfa at different times of being planted (1 to 3 months) in Congata. Alfalfa planted in three other locations (Quiscos, Yarabamba and La Joya) upstream and downstream of the first three was also analysed. To determine the concentration of heavy metals in sheep, measurements were made on liver and kidney samples from animals farmed in the first three sites. The concentration of metals and arsenic in the water samples was lower than the Peruvian environmental quality standards, except for Hg in Vitor  (0.0001 mg L^-1). The Cd content in the soil at all three sites (62.01 - 381.94 mg kg^-1) was well above the EQS for agricultural, commercial or industrial soils. The Cd content in the alfalfa samples grown in the same soils was higher than that observed in the samples from Quiscos, Yarabamba and La Joya. The estimated daily intake values (EDI) for metals detected in sheep kidneys and liver (Fe, Cu, Zn) were below the provisional maximum tolerable daily intakes (PMTDI) for children and adults, while the target hazard quotient (THQ) and total THQ of these elements were less than 1, indicating that their consumption would not have an adverse health effect.