Impacts of sunlight exposure on physicochemical parameters, potential toxic metals, and microbial characteristics of sachet drinking water sold in Calabar metropolis, Nigeria

Abstract Poor handling of potable water is a well-known route of contamination. Despite this, Nigeria’s most consumed packaged potable water called “sachet” or “pure water” is still poorly handled with long hours of exposure to sunlight which may affect its quality. This study examined the potential deterioration of the sachet water quality (potential toxic metals and bacteriological), and the health implication posed by long-time exposure to sunlight. Collected water samples were subjected to physiochemical analysis, metal analysis, risk assessment, and microbiological examination. Three sachet water brands (n = 4 bags per brand) exposed to sunlight daily for 14, 28, and 42 days were analysed for potentially toxic metals, and health risk assessments (Average daily dose-ADD, hazard quotient-HQ, hazard index-HI, and carcinogenic risk-CR). The physicochemical, and microbiological (total heterotrophic bacteria count-THBC, and total coliform count-TCC) parameters were equally analysed using the Kirby Bauer and pour plate technique. In all brands, the levels of physicochemical parameters (except pH), and potential toxic metals were comparatively higher than the control in an exposure time-dependent fashion. Furthermore, all the exposed samples failed to meet the safety limits of the WHO, and national standards (NAFDAC and NDSWQ) for drinking water. Among the metals, zinc was the most ingested metal in all the brands. The ADD, HQ, and HI evaluations revealed that consuming the exposed water could lead to higher accumulation of Cr, Cd, Pb, As, and Ni in the body following exposure. The CR of Cr, As, and Ni after exposure to sunlight were > than the safe value (10 –4 ), implying the likelihood of cancer after over 60 years. Microbial counts increased with the length of exposure, and all the isolates showed pathogenicity and multidrug resistance. The potential health risk inherent in sachet water after exposure to sunlight has significant health implications for consumers.