A Systematic Review of the Occurrence of Arsenic, Lead, Manganese, and Cadmium in Drinking Water Systems in Mexico

Toxic metals and metalloids (TMs) are inorganic chemical contaminants that cause adverse health outcomes. Drinking water is an important exposure route for TMs such as arsenic (As), cadmium (Cd), lead (Pb), and manganese (Mn). Arsenic and manganese are geogenic contaminants that can also arise from localized anthropogenic and industrial sources. Lead leaching from Pb-containing pipes and fittings is of particular concern. Occurrence of these and other TMs has been reported in drinking water in Mexico, but the evidence has not been synthesized. Following PRISMA Guidelines, we conducted a systematic review to understand the distribution of TM occurrence in Mexican drinking water. We searched PubMed, EBSCO Global Health, and Web of Science to identify studies published in English after 1968 that measured any TM in drinking water globally, identifying a set of 20,052 papers for screening, last searched in March 2025. A total of 134 papers were included that report quantitative data on TMs in Mexican drinking water. We found that 62%, 20%, 14%, and 18% of Mexican drinking water samples exceeded the World Health Organization’s Guideline Values for As, Pb, Mn, and Cd, respectively. Overall, there is sufficient evidence to recommend preventive measures to reduce TM exposures from drinking water in Mexico, but there is insufficient data to inform targeted remediation efforts. Across Pb, Mn, and Cd, we found that sample sites were overwhelmingly in urban settings, leaving rural populations underrepresented. While arsenic is well characterized across the country and should certainly be addressed, we found that Pb, Mn, and Cd are understudied outside of the region surrounding Mexico City. We have developed a GIS layer for researchers to identify areas where research has not been conducted. This study can inform the efforts of public health practitioners, policy-makers, and researchers to identify understudied regions for further monitoring, surveillance, and review.