The concentration and health risk assessment of heavy metals and microorganisms in the groundwater of Lagos, Southwest Nigeria

Contaminated water is increasingly linked to diseases worldwide, necessitating the safety evaluation of the sources of domestic and drinking water in every locality. The present study aimed to assess water safety in terms of lead (Pb), nickel (Ni), cadmium (Cd), copper (Cu), chromium (Cr), zinc (Zn), and microorganisms in the borehole and well water in Iwaya, Makoko, and Ilaje in Lagos, Nigeria. Water samples were subjected to atomic absorption spectroscopy (AAS) and microbiological examinations using standard protocols and compared with the World Health Organization (WHO) permissible limits. The average daily ingestion (ADI) and hazard quotient (HQ) of the selected heavy metals were also calculated using standard formulas. The AAS indicated that the borehole and well water of the three locations contained non-permissible levels of Pb, Ni, and Cd (only the well water in Ilaje), while Zn, Cu, and Cr were normal. In addition, the microbiological examinations showed that the borehole and well water of the three locations contained abnormal bacteria and coliform counts (well water only). The ADI and HQ of the selected heavy metals were less than one, which is the threshold at which a substance is considered safe for consumption. Water could pose some health risks, and the consumers in high-risk areas should consider water treatment before consumption.