# Evaluation of heavy metal concentration in drinking water, feed, and milk of dairy cows in Kombolcha metropolitan town, Ethiopia

## TL;DR

This study found dangerous levels of heavy metals in water, feed, and milk in Ethiopia, highlighting the need for better wastewater treatment.

## Contribution

The study provides new data on heavy metal contamination in dairy systems in Kombolcha, Ethiopia.

## Key findings

- Water samples had Pb and Cd levels exceeding safe limits.
- Elephant grass showed high Pb and Cd concentrations.
- Some milk samples exceeded international safety standards for heavy metals.

## Abstract

Cadmium (Cd), chromium (Cr), and lead (Pb) are significant industrial pollutants that contaminate soil, water, plants, and food, posing severe health hazards. Chromium, in particular, is associated with respiratory, kidney, and reproductive issues. In Kombolcha, untreated industrial wastewater increasingly threatens agricultural productivity and water quality. This study examined heavy metal contamination in dairy cows' feed, drinking water, and milk. A cross-sectional survey and laboratory tests using a flame atomic absorption spectrophotometer analyzed 40 samples from water sources, feed, and milk. Water samples showed mean Pb levels of 0.0205 ± 0.004 mg/L and Cd at 0.0112 ± 0.0029 mg/L, with Cr below detection. In elephant grass, Cd was 1.47 ± 0.0016 mg/kg; Cr 1.87 ± 0.115 mg/kg; and Pb 11.4 ± 0.0031 mg/kg. While Cr and Pb in hay and brewery grain were within safe limits, levels in elephant grass and some milk samples exceeded international safety standards. The findings highlight the vital need to improve wastewater treatment and strengthen health protections.

•Brewery by-products and hay are the main feed for dairy cattle•40% of major industries dump untreated wastewater into the Borkena river•Borkena reservoirs had higher cadmium; Ras Anges had higher lead levels•Cd and Pb found in water, feed, milk; Cr below detection limits

Brewery by-products and hay are the main feed for dairy cattle

40% of major industries dump untreated wastewater into the Borkena river

Borkena reservoirs had higher cadmium; Ras Anges had higher lead levels

Cd and Pb found in water, feed, milk; Cr below detection limits

Environmental science; Environmental health; Applied sciences