Percentage of samples from the Massachusetts EEA database that exceed the secondary maximum contaminant level (SMCL) of 50 µg/L or the lifetime health advisory (LHA) of 300 µg/L. Darker shades represent a greater percentage of samples above guideline values. The number of monsters in each city is indicated in text within the city lines. a Percentage of samples collected between September 2018 and December 2019 above the SMCL. b Percentage of samples collected between September 2018-December 2019 above the LHA. c Percentage of samples collected between 1994 and 2022 above the SMCL. d Percentage of samples collected between 1994 and 2022 above the LHA. Credit: Journal of Exposure Science & Environmental Epidemiology (2023). DOI: 10.1038/s41370-023-00563-9
Manganese is an unregulated contaminant commonly found in drinking water, but safe levels of this metal are currently unknown, and previous research has shown that overexposure to manganese can be harmful to children.
Now, a study led by researchers at the Boston University School of Public Health (BUSPH) has found that manganese concentrations in the drinking water of a Massachusetts community often exceeded the maximum recommended levels of manganese listed in current guidelines.
Published in the Journal of Exposure Science & Environmental Epidemiologythe findings also suggest that the observed levels of manganese may be high enough to pose a risk to children and other vulnerable communities who are exposed.
Manganese is a naturally occurring component of soil and rock, and it is both an essential nutrient and a toxic substance, so too little or too much exposure can be harmful to health. Despite the fact that manganese is found in the drinking water of many communities in the US, it is not federally regulated. The US Environmental Protection Agency has developed guidelines that define a maximum level of daily exposure to manganese for “aesthetic” purposes (i.e., color and taste), as well as for the overall health and safety of the general population. But these guidelines are just recommendations; they cannot be enforced in the way established primary norms can.
“A certain amount of manganese is necessary for health, but there is growing evidence that excess manganese can harm children’s brains,” said study leader and corresponding author Alexa Friedman, a doctoral student at BUSPH at the time of the study. “Our findings suggest that manganese levels in public drinking water exceeded aesthetic guidelines on average 40% of the time and exceeded health guidelines 9% of the time. These data support the need for a legally enforceable primary drinking water standard for manganese to improve children’s health. better protection.”
The new study is one of the first to examine manganese concentrations in drinking water over time and location in the United States.
For the study, Friedman and colleagues examined residential tap water samples collected between September 2018 and December 2019 in the suburb of Holliston, Massachusetts, as part of a community-initiated pilot study called ACHIEVE (Assessing Children’s Environmental Exposures). Holliston residents had raised concerns about the quality of their drinking water and the safety of children in the community after noticing that their tap water occasionally turned black or brown. Communities that receive tap water from shallow aquifers are particularly vulnerable to exposure to high levels of manganese, and Holliston residents rely on this source for nearly all of their drinking water.
“While average water manganese concentrations in Holliston were relatively low, our work showed that levels nonetheless often exceed current aesthetic and health-based guidelines,” said senior author Birgit Claus Henn, associate professor of environmental health at BUSPH. “While the existing guidelines can be useful benchmarks, without an enforceable standard there is a limit to what will be done to ensure the water is safe to drink and/or meets these guidelines.”
The researchers also compared their community-level manganese samples to public data on manganese levels across the state. They found similar ranges, suggesting that manganese overexposure is not an isolated problem within the Holliston community.
To better understand the health risks of exposure to manganese in drinking water, Claus Henn and Friedman recommend that policymakers and other researchers increase monitoring of manganese in water, conduct health surveys of this exposure in communities, and consider an enforceable standard.
“If residents are concerned about manganese levels in their drinking water, they should refer to these resources online from the Massachusetts Department of Environmental Protection,” says Friedman. “It’s also important to know that manganese cannot be removed by boiling the water, and many household filters are not effective at removing manganese from water,” she adds use filters that can remove manganese, and the filtration units should clearly indicate this capability.”
More information:
Alexa Friedman et al, Manganese in residential drinking water from a community-initiated case study in Massachusetts, Journal of Exposure Science & Environmental Epidemiology (2023). DOI: 10.1038/s41370-023-00563-9
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