A deterministic risk assessment of the human exposure to Cadmium, Lead and Chromium through the consumption of well and bottled water in Lusaka District, Zambia

The United Nations Sustainable Development Goal Number Six is to ‘Ensure availability and sustainable management of water and sanitation for all’, which is an essential component for human survival. Access to safe drinking water is essential for health, a basic human right and a component of effective policy for health protection. Safe drinking water implies that the water does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that may occur between life stages. However, water is prone to contamination with heavy metals through natural and anthropogenic sources, making it unsuitable for human consumption due to the cumulative potential risks associated with the presence of heavy metals. This study was conducted to assess the non-carcinogenic and carcinogenic risk of human exposure to cadmium, lead and chromium through the consumption of well and bottled water in Lusaka district of Zambia. Secondary data was used to determine the mean concentrations of heavy metals in well and bottled water in Lusaka District and to calculate the hazard index (non-carcinogenic risk) and cancer risk for the metals under study. The results revealed that a hazard index for cadmium, lead and chromium in both well and bottled water was higher than 1, indicating adverse effects on human health over a lifetime of consumption. Similarly, the total cancer risk through exposure to cadmium and chromium in well and bottled water was 1.2 x 10-1 and 2.25 x 10-1, respectively, higher than the safe threshold limit set by the United States Environmental Protection Agency (USEPA) of 1 × 10−4. The study concludes that there is a possible non-carcinogenic risk of exposure to cadmium, lead and chromium through the consumption of well and bottled water in Lusaka District. Further, the study concludes that there is a possible carcinogenic risk of exposure to cadmium and chromium through the consumption of both well and bottled water. Owing to the proportion of both well and bottled water samples that exceeded the Zambia Bureau of Standards threshold limit, cadmium poses the greatest concern and requires intervention to reduce exposure. Therefore, it is recommended that heavy metal concentrations in drinking water should be periodically monitored to minimise health risks to consumers.