A Systematic Review of Toxic Metals Occurrences through Drinking Water in Ghana

Toxic metals (TMs) are metallic contaminants that cause adverse health effects even at low exposure levels. Arsenic (As), Manganese (Mn), Lead (Pb), and Cadmium (Cd) are among these contaminants of concern, causing irreversible developmental damage to children (Pb), as well as cardiovascular disease (Pb) and cancers (As) in adults. Arsenic and Manganese are primarily geogenic groundwater contaminants that can also be introduced to drinking water systems by localized anthropogenic contamination sources. Corrosion of lead-containing plumbing components contributes to much of the Lead in drinking water, while localized anthropogenic pollution can leach into some otherwise clean water sources as well. Cadmium is often used in fertilizers and can be an indicator of anthropogenic contamination. We reviewed published studies reporting on concentrations of As, Mn, Pb, and Cd in Ghanaian drinking water quality to assess the occurrence and potential health implications of these TMs. As part of a larger systematic review, we searched for peer-reviewed literature from PubMed, EBSCO Global Health, and the Web of Science, between November 2019 and March 17, 2025, to retrieve studies published in English after 1968 that assessed toxic metals levels or contamination in drinking water in Low- and Middle-Income Countries. This generated 20,552 studies from the initial search, which were screened down to 3,993 studies for extraction. We selected the 93 studies that measured a TM in Ghanaian drinking water for full-text review and data extraction. We focused on Arsenic, Manganese, Lead, and Cadmium, for which we had the most data on metals with WHO limits. 79 studies reported concentrations of Arsenic, Manganese, Lead, and/or Cadmium. A quality evaluation was carried out for these studies by assessing the suitability of reported sample collection, analysis, and quality assurance/quality control practices, and by extracting information on the source of drinking water, GPS coordinates, and observed concentrations for each TM. This resulted in the inclusion of 93 studies comprising 82,111 samples, with 8,124, 11,882, 6,079, and 6,679 observations for Arsenic, Manganese, Lead, and Manganese, respectively. We found that 18%, 34%, 17%, and 15% of included Ghanaian drinking water samples exceeded the WHO Guideline Values for Arsenic, Manganese, Lead, and Cadmium, respectively. Data were widespread across Ghana, though we found few studies in the regions north of Kumasi. These findings comprise sufficient evidence to recommend preventative action to eliminate such contamination in new drinking water systems in Ghana, as well as to explore potential interventions to progressively prioritize and remediate the most serious existing exposures to TMs in existing drinking water systems.