Is manganese in drinking water dangerous?

Manganese is an essential trace mineral. At low levels, it's necessary for normal body function. But at elevated levels in drinking water, the research suggests a risk to neurological development, particularly in infants and young children. The EPA issued a health advisory for manganese of 0.3 mg/L for adults and 0.1 mg/L for infants. These are advisory levels, not enforceable MCLs, but they're based on health data, not just aesthetics.

What are the symptoms of too much manganese from water?

At very high occupational exposures, manganese causes a Parkinson's-like syndrome called manganism. The research on drinking water levels focuses on more subtle neurological effects: lower IQ scores, attention and memory problems, and motor skill differences in children with higher manganese intake. These are associations found in epidemiologic studies, not direct causation proven by clinical trials. But the pattern across multiple studies is consistent enough that the EPA issued a health advisory.

Is manganese staining in well water a health risk?

Staining on fixtures and laundry (brownish-black stains from manganese) indicates that manganese is present, but staining doesn't directly tell you the concentration. The EPA Secondary MCL for manganese is 0.05 mg/L, which is the aesthetic threshold. The health advisory threshold is 0.3 mg/L for adults. Staining can occur below the health advisory level. You need a lab test for the actual concentration.

Should infants drink water with manganese?

The EPA health advisory for infant exposure is 0.1 mg/L, about one-third of the adult advisory level. The lower threshold reflects concern about neurological development during early childhood. If your well water tests above 0.1 mg/L for manganese and you have an infant in the home, your child's care team should know. Filtered or bottled water for formula preparation is a reasonable precaution while you evaluate treatment options.

Does my municipality test for manganese?

Utilities test for manganese as part of EPA Secondary Standards compliance, but the testing frequency and reporting varies. Your Consumer Confidence Report may not specifically call out manganese unless levels are above the secondary standard. You can call your utility and ask for their manganese data for the past year. For well owners, testing is the only way to know.

Manganese Health Effects: What the Science Shows About Long-Term Exposure

This page covers a health topic. It is not medical advice. If you have concerns about manganese exposure, talk to your doctor or your child’s pediatrician. In emergencies, call 911.

Manganese isn’t just an aesthetic problem. Most coverage focuses on the staining it causes on fixtures and laundry. The bigger concern is what the research shows about neurological development in children exposed to high levels through drinking water.

This distinction matters. Manganese has an EPA health advisory based on health data, not just a secondary aesthetic standard. That’s a different category of concern than iron or hardness, which are primarily cosmetic issues.

Manganese as a Nutrient and as a Toxin

Your body needs small amounts of manganese. It plays a role in bone formation, blood clotting, and inflammation response. You get dietary manganese from grains, nuts, legumes, and leafy vegetables.

But dietary manganese and manganese dissolved in water follow different metabolic pathways. The gut regulates dietary manganese absorption fairly efficiently, absorbing more when stores are low and less when they’re adequate. Manganese dissolved in drinking water appears to be absorbed and distributed differently, with less efficient regulation.

This is why the concern about high manganese in water isn’t simply “too much of a nutrient.” The form and pathway change the health equation. The research on neurological effects from manganese in drinking water is based specifically on water-source exposure, not total dietary manganese intake.

What the Research Finds

Multiple independent studies have found associations between higher manganese concentrations in drinking water and neurological outcomes in children. The strongest research comes from Canadian cohort studies, particularly work from McGill University researchers examining children in Quebec.

A 2010 study published in Environmental Health Perspectives (Bouchard et al.) followed school-age children in Quebec and found that higher manganese in well water was associated with lower IQ scores. The association held after accounting for other factors like lead exposure, maternal education, and household income.

Later studies from the same research group and independent groups in Bangladesh and other regions found similar patterns: children with higher manganese exposure showed differences in memory, attention, and motor skills. A 2020 follow-up study found associations persisted into adolescence.

These are associations from observational research. They’re not controlled experiments proving causation. But the pattern across multiple independent studies, in different countries and populations, is consistent enough that the EPA established a health advisory specifically for manganese in drinking water. That advisory position didn’t exist for decades and was added because the cumulative evidence warranted it.

At very high exposure levels, such as those seen in occupational settings like mining and welding, manganese causes a well-characterized neurological condition called manganism. It produces symptoms resembling Parkinson’s disease. Manganism is a different and more severe outcome than the subtle developmental effects seen in drinking water research, but both point to the same biological sensitivity of the nervous system to excess manganese.

The Two Manganese Standards

This is where it gets confusing, because manganese has two separate EPA standards that mean different things.

EPA Secondary MCL: 0.05 mg/L. This is an aesthetic standard. It’s not enforceable. It was set to prevent the brownish-black staining that manganese causes on laundry, fixtures, and pipes at higher concentrations. Secondary MCLs exist to address taste, odor, and appearance, not health.

EPA Health Advisory: 0.3 mg/L (lifetime for adults) and 0.1 mg/L (for infants). These are health-based advisory levels. They were set based on neurological health data. They are not enforceable limits, but they reflect the EPA’s assessment of health risk, not aesthetics.

The counterintuitive part: the aesthetic standard (0.05 mg/L) is lower than the health advisory (0.3 mg/L for adults). That doesn’t mean the aesthetic concern is more serious. It means the aesthetic effects appear at lower concentrations than the health effects. So if your well produces black staining, you likely exceed the secondary MCL, but you may or may not exceed the health advisory. A lab test tells you which.

Don’t assume that meeting the secondary standard means meeting the health advisory. They’re separate numbers answering separate questions.

Who Faces the Greatest Risk

Infants carry the greatest risk from manganese in drinking water.

An infant drinking formula prepared with well water receives a higher dose per unit of body weight than an adult drinking the same water. The infant health advisory of 0.1 mg/L reflects this. It’s approximately one-third of the adult advisory.

The concern is highest during the first year of life, when neurological development is most rapid and when formula may represent a large fraction of total fluid intake. Breastfed infants whose mothers drink manganese-contaminated water have lower manganese exposure through breast milk than formula-fed infants using that same water, because manganese in breast milk is regulated independently of the mother’s intake.

Young children in general have higher fluid intake per body weight than adults, and their nervous systems are still developing. The research on school-age children in Quebec reflects this window of vulnerability.

Healthy adults without other neurological conditions are at lower risk at typical well water concentrations, but the lifetime advisory of 0.3 mg/L still reflects a real risk for long-term exposure.

Testing and What to Do

Get a lab test for dissolved manganese from a state-certified lab. Compare your result to both the secondary MCL (0.05 mg/L) and the health advisory (0.3 mg/L for adults, 0.1 mg/L for infants), not just one or the other.

If your result is above 0.1 mg/L and you have an infant in the home, talk to your pediatrician before relying on that water. Bottled water or a point-of-use filter for formula preparation is a reasonable immediate step while you evaluate longer-term treatment.

For treatment options, see how to remove manganese from well water. For lab testing resources, see best mail-in water tests.

Sources

U.S. Environmental Protection Agency. Health Advisory for Manganese. https://www.epa.gov/sdwa/drinking-water-health-advisories-has
Bouchard MF, et al. Intellectual Impairment in School-Age Children Exposed to Manganese from Drinking Water. Environmental Health Perspectives. 2011. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3059010/
World Health Organization. Manganese in Drinking Water: Background Document for Development of WHO Guidelines for Drinking Water Quality. https://www.who.int/docs/default-source/wash-documents/wash-chemicals/manganese-background-doc.pdf
U.S. Environmental Protection Agency. Secondary Drinking Water Standards: Guidance for Nuisance Chemicals. https://www.epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals