Concentration of Heavy Metals in Teff Straw, Water and Milk in Some Selected Areas of Central Ethiopia

Abstract

The concentration of cadmium (Cd), lead (Pb), arsenic (As) and chromium (Cr) in teff straw, water and milk were studied in East and West Shoa, Ethiopia. The concentration of heavy metals in feed, water and milk were investigated using Graphite Furnace Atomic Absorption Spectrophotometer. Heavy metals in teff straw in West and East Shoa were 1543.54 ± 318.70 μg/kg and 1486.92 ± 279.73 μg/kg, respectively and were found in the order of Cr > As > Pb > Cd. The concentration of heavy metals in water in East Shoa (28.08 ± 7.02 μg/L) was significantly higher (p<0.05) than in West Shoa (1.96 ± 0.28 μg/L) and were in the order of Cr > As > Pb > Cd. Water samples obtained from Mojo Tannery had the highest level of heavy metals (86.89 μg/L) followed by Mojo Lake (67.89 μg/L) and a river near Mojo town (43.64 μg/L). Except for pH of water from Mojo Lake (10.4) and Gelan dye factory (8.9), the rest of water samples from East Shoa were found within the recommended pH limit of 6.5-8.5 for livestock drinking. Water samples from West Shoa had an average pH of 7.0 ranging 6.4–7.7 and were within the permitted limit. Water from Mojo had the highest concentration of Cr and the contamination level of heavy metals in water from East Shoa was in the order Mojo > Awash River > Gelan > Akaki > Bishoftu. The concentration of heavy metals in water from East Shoa was more than ten times higher than West Shoa. The concentration of heavy metals in livestock water in the study areas did not pass the standard limit. The overall concentrations of heavy metals in milk were in the order Cr > Cd > Pb > As. Compared to WHO/JECFA 1989 standards, the concentrations of Cd and As in milk were within the permitted limits, whereas the concentrations of Cr and Pb were found beyond the standard limit. It is concluded that the level of heavy metals near industrial areas were higher than those sites in non-industrial areas. It is recommended that further study is required on heavy metals content of soils, fodder feeds and livestock products in these study areas.