Heavy metal contamination pathways and health risk assessment in raw buffalo milk from Egyptian dairy environments: Implications for safety and sustainability.

Abstract

Background: Buffalo is an essential component of Egypt's dairy industry. However, their environmental pollution threatens the production and sustainability of the sector. Heavy metal (HM) contamination in dairy systems is a growing environmental and public health concern, particularly in developing regions experiencing increased industrial and livestock intensification.

Aim: This study aimed to evaluate HM contamination in buffalo milk across three environmentally distinct dairy farms in Egypt, identify potential environmental exposure pathways, and assess associated public health risks.

Methods: ICP-MS/MS was employed to determine the concentrations of lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), nickel (Ni), arsenic (As), and cobalt (Co) in composite milk samples (48) obtained twice weekly from three selected Buffalo dairies located in Al Qalyubia and Giza provinces, over two months, alongside tracing the possible contamination pathways of the collected environmental samples. Estimated daily intake (EDI) and target hazard quotient (THQ) were calculated for each metal based on the corresponding oral reference dose (RfDo) to evaluate public health implications. In addition, the water quality and the bedding nitrogen profile were assessed.

Results: Significant differences (P < 0.05) were revealed among the farms in daily milk yield (DMY) and quality. Mercury, nickel, and cobalt were undetectable, whereas Pb, Cd, Cr, and As exceeded the maximum permissible limits of the Codex/WHO. Lead peaked in Farm 3 and arsenic in Farm 2, both of which were negatively correlated with DMY, with as far exceeding safety limits (>30 times the 0.01 mg/kg), indicating significant environmental exposure. The environmental matrices (water, feed, and bedding) showed notable metal enrichment with localized exceedances of turbidity, nitrite, and bromide, enhancing the water-feed-animal transfer pathway as a major contamination route. The calculated EDI and THQ values were below 1; however, the relatively high Pb and As concentrations underscore the need for continuous monitoring and mitigation strategies to ensure public safety.

Conclusion: Spatial variations in HM contamination, milk production, and associated health risk assessments reflected local environmental contamination from industrial, agricultural, and municipal sources. These findings highlight the need for continuous monitoring, source tracing, and planned farm management practices to protect the health of consumers and the sustainability of Egypt's buffalo dairy sector.