Manganese is a naturally occurring mineral found in food, drinking water and soil. Small amounts of manganese are necessary for health, but excessive manganese may 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 federal government 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 EPA also has set a nonbinding 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. Millions of Americans drink tap water with manganese levels above this level. The state also has a health guideline for young children and pregnant women of 300 ppb.
According to EWG data, over 9 million Americans drink water from public systems with manganese above Minnesota’s guideline for infants and pregnant women. In 2009 the U.S. Geological Survey reported that one-in-six drinking water samples in a large study of private wells exceeded 300 ppb of manganese.
What are the toxic effects of manganese?
The primary targets of manganese are the brain and nervous system. Manganese poisoning has been observed in workers who inhale it in industrial settings for long periods of time. These workers report lethargy and weakness, and 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.
Alison Sanders and her colleagues at the Icahn School of Medicine at Mount Sinai in New York City reviewed the existing studies of children, and reported that 12 of 14 studies 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.
While the existing studies in children collectively point to a need to curb manganese ingestion, there are unanswered questions. People consume far more manganese through food than water, but due to complexities of nutrient bioavailability, dietary manganese may not be absorbed as well as manganese in water.
Most studies of infant neurodevelopment use manganese measurements from hair, teeth, blood or umbilical cord blood as a measure of exposure from all sources. Few studies can assess the independent effects of water and food on neurological outcomes.
- A doctoral thesis by Frida Zipkin 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 headed one of the only epidemiological studies to assess the role of manganese in drinking water and diet. She examined diet and water for 375 Canadian children and found that levels of manganese in hair were more related to a child’s estimated intake of manganese from water than that from food, despite the fact that children got much more manganese from food.
- A second paper from this study, by Youssef Oulhote, 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 is safe?
EWG concurs with the Minnesota guideline for manganese in drinking water of 50 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 levels 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 IQs.
Manganese is commonly detected in food and drinking water. Manganese 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.
What should be done to address the risks of manganese exposure?
There are important unresolved issues about the safety of low doses of manganese ingestion for children. Studies suggest that manganese in drinking water may be more damaging than manganese in food. The EPA set an enforceable national standard that caps manganese 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 company to see if there’s a problem with manganese in your water. Reverse osmosis is the most reliable system for removing manganese. Click here to see 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.
No public health authorities currently give any warnings about limiting foods rich in manganese during pregnancy, childhood or adulthood.
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, Manganese: Tiered Health Based Guidance for Water. 2012. Available at www.health.state.mn.us/divs/eh/risk/guidance/gw/manganese.html
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.
U.S. Geological Survey, Quality of Water from Domestic Wells in the United States. 2009. Available at water.usgs.gov/nawqa/studies/domestic_wells
F. Zipkin, Assessment of Manganese Dietary Intake for a Rural Pediatric Population. Doctoral Dissertation, University of Cincinnati, 2014.