Human health risk assessment of exposure to cadmium, lead and chromium through consumption of well and bottled water in Lusaka district, Zambia.
Water is an essential product for human survival, which all age groups consume and access to safe drinking water is essential to health. 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. Water is prone to contamination with heavy metals through natural and anthropogenic pollution, making it unsuitable for human consumption because of the negative health outcomes associated with it. This study assessed the non-carcinogenic and carcinogenic risk of human exposure to cadmium, lead and chromium through consumption of well and bottled water in Lusaka district of Zambia. This study was a deterministic human health risk assessment that followed the Codex Alimentarius Commission's food safety risk assessment framework, comprising hazard identification, hazard characterisation, exposure assessment and risk characterisation. The objective was to assess the risk of exposure to cadmium, lead and chromium through water consumption. The study used results by Nambeye (2017) on well water quality analysis in George compound of Lusaka district and results by ZCSA (2021) on bottled water quality analysis in Lusaka district to estimate the non-carcinogenic and carcinogenic risk of exposure to cadmium, lead and chromium through consumption of well and bottled water. The high levels of cadmium, lead and chromium observed in these studies prompted the conduct of this exposure risk assessment study. The study adopted the World Health Organisation (WHO) and the United States Environmental Protection Agency (USEPA) default water consumption and exposure reference values to calculate the hazard quotient and cancer risk for the metals under study. This study found that the hazard index for cadmium, lead and chromium in both well and bottled water was higher than 1, indicating an adverse effect 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 and higher than the safe threshold limit set by USEPA of 1 × 10−4. This study has concluded that there is a possible non-carcinogenic risk of exposure to cadmium, lead and chromium through consumption of bottled water in Lusaka district. The study also concluded that there is a possible non-carcinogenic risk of exposure to cadmium, lead and chromium through consumption of well water in George compound of Lusaka district. This is attributed to the high concentration of heavy metals in both well and bottled water. Results also indicate that there is a possible carcinogenic risk of exposure to cadmium and chromium through consumption of both well and bottled water, with a chance of causing 1 case of cancer for every 10,000 people for those who consume well water and 2 cases of cancer for every 10,000 people for those who consume bottled water, over a lifetime of water consumption. Owing to the proportion of samples that exceeded the Zambia Bureau of Standards threshold limit in both well and bottled water, cadmium poses the greatest concern and requires intervention to reduce exposure. Therefore, there is a need for relevant institutions to continue monitoring the levels of heavy metals in drinking water to protect the public from exposure to unacceptable levels of heavy metals.
Genetic toxicology., Carcinogens., Carcinogenic risk to humans.
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