Manganese

Summary

Manganese is a naturally occurring mineral found in food, drinking water and soil. In small amounts, manganese is necessary for good health. But in excess, manganese can harm infants and children.

There is growing scientific evidence that manganese exposures during pregnancy and childhood can impair learning, memory and behavior in children.

The Environmental Protection Agency has not set a legal limit for manganese in drinking water. Instead, it has a non-enforceable guideline that encourages water companies to keep manganese levels below 50 parts per billion, or ppb. At levels higher than that, water can taste bad, form rust-like deposits in water lines or stain laundry.

The agency has also set a non-enforceable health reference level for no more than 300 ppb of manganese in drinking water.

Minnesota has set a non-enforceable guideline of 100 ppb of manganese in water for bottle-fed babies. The state also has a health guideline for everyone else in the household more than one year old of 300 ppb.

According to EWG’s analysis of state data and data collected as part of the fourth round of the EPA-mandated Unregulated Contaminant Monitoring Rule program, or UCMR 4, more than 5 million Americans drink water from public systems with manganese above this level.

In 2018, the U.S. Geological Survey reported that 7 percent of wells in large study of private wells exceeded 300 ppb of manganese.

Click here to see the nationwide test results for manganese.

How are people exposed to manganese, and how does it get into tap water?

People consume far more manganese through food than water. But due to complexities of nutrient uptake, dietary manganese from food may not be absorbed as well as manganese in water.

Manganese naturally occurs in the environment. It’s found in rocks and soil, and can leach from them into groundwater. 

It also enters water supplies through industrial discharges. It’s used in the manufacture of many substances, such as batteries, glass, fireworks, fertilizer, pesticides, cosmetics and livestock feed supplements.

Other sources of manganese in groundwater include mining processes and landfill leaching. Manganese is used as a gasoline additive and enters the environment via car exhaust.

What are the toxic effects of manganese in drinking water?

The primary targets of manganese are the brain and nervous system. Manganese poisoning has been observed in workers who inhale it in industrial settings over long periods of time. These workers report lethargy and weakness, and they can develop Parkinson’s-disease-like symptoms.

Manganese poses more serious concerns for children. A growing number of studies report associations between manganese exposure and hyperactivity, poorer IQ scores, and memory and attention problems in children.

Scientists at the Icahn School of Medicine at Mount Sinai, in New York, reviewed 14 studies of children and reported that 12 found manganese was associated with poorer intelligence and mental development. Seven studies found a significant relationship between manganese exposure and behavioral problems. Children also absorb and retain more manganese than adults.

Most studies of infant neurodevelopment use manganese measurements from hair, teeth, blood or umbilical cord blood to assess exposure from all sources. Few studies can assess the independent effects of water and food on neurological outcomes.

For example:

• A thesis by doctoral student Frida Zipkin at the University of Cincinnati found that manganese in North Carolina children’s blood or hair samples did not correlate with their dietary intake. The study did not measure or estimate the children’s ingestion of manganese from water.
• In 2011, Maryse Bouchard at the University of Montreal headed one of the only epidemiological studies to assess the role of manganese in drinking water and diet. She examined the diet and water consumption of 375 Canadian children and found that levels of manganese in hair were more closely related to a child’s estimated intake of manganese from water than from food, even though the children got much more manganese from food.
• A second paper from this study, by Youssef Oulhote at the University of Montreal, reported in 2014 that children with the highest one-fifth of manganese in their hair had IQ scores more than six points lower than children with the lowest fifth. Both levels in hair and estimated drinking water exposures were associated with poorer memory and attention and more hyperactivity.

How much manganese in drinking water is safe?

EWG concurs with the Minnesota guideline for manganese in drinking water of 100 ppb for bottle-fed infants. This is based on the most sensitive effects in animal studies, with an additional margin of safety to account for the added sensitivity of children’s brains. 

Minnesota and the EPA agree that manganese levels in drinking water below 300 ppb are safe for breastfed infants, pregnant women and young children not fed baby formula. But we caution that studies suggest that levels below 100 ppb could still lower children’s IQ.

What can be done to reduce manganese exposure?

Manganese is commonly detected in food and drinking water. Concentrations vary widely in foods, including leafy greens, nuts, grains and legumes. Manganese is also added to many multivitamins. However, no government agency has recommended that parents avoid feeding children any specific foods as a way of decreasing manganese ingestion. Nor do public health authorities warn about limiting foods rich in manganese.

There are important unresolved questions about the safety for children of low doses of manganese ingestion. Studies suggest that manganese in drinking water may be more harmful to them than manganese in food. 

The EPA should set an enforceable national standard that caps exposure at levels that are safe for formula-fed babies, the group at greatest risk from the chemical.

If you are concerned about manganese in your drinking water, check EWG’s Tap Water Database or contact your water utility to see whether tests have found it. Reverse osmosis is the most reliable system for removing manganese from tap water. Click here to read more about reverse osmosis filters.

Small water systems and private wells are not routinely tested, so EWG encourages you to find a lab that can test your water for manganese if you are pregnant, have a baby or notice the water is rust colored or has a metallic taste. Minnesota recommends people who drink well water test it every year.

References

M. Bouchard et al., Intellectual Impairment in School-Age Children Exposed to Manganese from Drinking Water. Environmental Health Perspectives, 2011, 119:138–143. Available at ehp.niehs.nih.gov/1002321/.

M. Bouchard, Manganese in Drinking Water: Bouchard Responds. Environmental Health Perspectives, 2011, 119:a241. Available at ehp.niehs.nih.gov/1103485r/.

Health Canada, Manganese in Drinking Water: Document for Public Consultation. 2016. Available at www.canada.ca/en/health-canada/programs/consultation-manganese-drinking-water/manganese-drinking-water.html.

D. Coetzee et al., Measuring the Impact of Manganese Exposure on Children’s Neurodevelopment: Advances and Research Gaps in Biomarker-Based Approaches. Environmental Health, 2015, 15:91.

EPA, Drinking Water Health Advisory for Manganese. EPA-822-R-04-0003. 2004. Available at www.epa.gov/safewater/ 

Minnesota Department of Health, Toxicological Summary for Manganese. 2023. Available at https://www.health.state.mn.us/communities/environment/risk/docs/guidance/gw/manganese.pdf.

Y. Oulhote et al., Neurobehavioral Function in School-Age Children Exposed to Manganese in Drinking Water. Environmental Health Perspectives, 2014, 122(12):1343–1350.

A. Sanders et al., Perinatal and Childhood Exposure to Cadmium, Manganese, and Metal Mixtures and Effects on Cognition and Behavior: A Review of Recent Literature. Current Environmental Health Reports, 2015, 2:284–294.

P. McMahon et al., Elevated Manganese Concentrations in United States Groundwater, Role of Land Surface–Soil–Aquifer Connections, Environmental Science and Technology, 2018, 53 (1):29-38. Available at https://pubs.acs.org/doi/10.1021/acs.est.8b04055.

U.S. Geological Survey, Scientists find many Americans may be drinking groundwater with elevated levels of manganese, 2018. Available at https://water.usgs.gov/nawqa/home_maps/manganese_gw.html 

F. Zipkin, Assessment of Manganese Dietary Intake for a Rural Pediatric Population. Doctoral Dissertation, University of Cincinnati, 2014.