EPA legal limit
300 ppb
Maximum Contaminant Level
EWG health guideline
50 ppb
Science-based, stricter target
Health effects
Infants consuming formula made with high-manganese water face the highest risk — neurodevelopmental effects including IQ reduction and ADHD-like behaviours have been reported. Adults can tolerate much higher levels. The primary concern is neurological at chronic exposure levels well above dietary requirements.
Where it comes from
Naturally occurring from manganese-bearing rock and sediment, particularly in deep wells and in water with low dissolved oxygen. Also from industrial discharges.
How it's regulated
EPA secondary MCL: 50 ppb (non-enforceable aesthetic standard). EPA health advisory: 300 ppb. EWG health guideline: 50 ppb — focused on neurodevelopmental risk in infants, where the safety margin is much narrower than for adults.
The EPA vs EWG gap
The legal limit (300 ppb) is 6× higher than the EWG health guideline (50 ppb). Water can be legally compliant while still exceeding the science-based threshold.
How to filter manganese
Not all filters address manganese. Look for independently certified filters—NSF International certification means the removal claim has been independently verified.
Frequently asked questions
What is manganese?
Manganese is a naturally occurring metal that occurs at elevated levels in some groundwater and surface water, particularly where oxygen levels are low (anaerobic conditions). While an essential trace mineral in the diet, excess manganese in drinking water raises health concerns especially for infants and young children.
What are the health effects of manganese?
Infants consuming formula made with high-manganese water face the highest risk — neurodevelopmental effects including IQ reduction and ADHD-like behaviours have been reported. Adults can tolerate much higher levels. The primary concern is neurological at chronic exposure levels well above dietary requirements.
Is manganese regulated in drinking water?
EPA secondary MCL: 50 ppb (non-enforceable aesthetic standard). EPA health advisory: 300 ppb. EWG health guideline: 50 ppb — focused on neurodevelopmental risk in infants, where the safety margin is much narrower than for adults.
Where does manganese come from?
Naturally occurring from manganese-bearing rock and sediment, particularly in deep wells and in water with low dissolved oxygen. Also from industrial discharges.
How do I remove manganese from tap water?
The most effective methods for removing manganese are: Reverse osmosis (RO), NSF 58 certified RO system, Ion exchange resin. Look for NSF-certified systems—independent certification confirms removal claims have been verified.
Is manganese in your water?
Enter your ZIP code to see the measured level in your specific utility.