Small Community Water Systems Have the Highest Prevalence of Mn in Drinking Water in California, USA

Miranda L Aiken; Samantha C Ying

doi:10.1021/acsestwater.3c00007

Small Community Water Systems Have the Highest Prevalence of Mn in Drinking Water in California, USA

ACS ES T Water. 2023 May 8;3(8):2168-2178. doi: 10.1021/acsestwater.3c00007. eCollection 2023 Aug 11.

Authors

Miranda L Aiken¹, Samantha C Ying^{2

3

4}

Affiliations

¹ School of Earth and Environmental Sciences, Schmid College of Science and Technology, Chapman University, Orange, California 92866, United States.
² Schmid College of Science and Technology, Chapman University, Orange, California 92866, United States.
³ Environmental Sciences Department, University of California, Riverside, California 92521, United States.
⁴ Planetary Health Center, University of California Global Health Institute, San Francisco, California, 94158, United States.

Abstract

Manganese (Mn) is currently regulated as a secondary contaminant in California, USA; however, recent revisions of the World Health Organization drinking water guidelines have increased regulatory attention of Mn in drinking water due to increasing reports of neurotoxic effects in infants and children. In this study, Mn concentrations reported to California's Safe Drinking Water Information System were used to estimate the potentially exposed population within California based on system size. We estimate that between 2011 and 2021, over 525,000 users in areas with reported Mn data are potentially exposed to Mn concentrations exceeding the WHO health-based guideline (80 μg L^-1), and over 34,000 users are potentially exposed to Mn concentrations exceeding the U.S. Environmental Protection Agency health-advisory limit (300 μg L^-1). Water treatment significantly decreased Mn concentrations compared to intake concentrations for all system sizes. However, smaller water systems have a wider range and a higher skew of Mn concentrations in finished water than larger systems. Additionally, higher Mn concentrations were found in systems above the maximum contaminant levels for chromium and arsenic. The treatment of these primary contaminants appears to also remove Mn. Lastly, data missingness remains a barrier to accurately assess public exposure to Mn in very small, small, and medium community water system-delivered water.