Common Water Contaminants
Learn about regulated contaminants found in U.S. drinking water — health effects, EPA limits, and how to remove them.
Arsenic in Drinking Water
Arsenic MCL is 10 ppb (0.010 mg/L). Long-term exposure increases cancer risk. Common in western U.S. groundwater. Reverse osmosis is the most effective home filter.
Chromium-6 (Hexavalent Chromium) in Drinking Water
No federal MCL exists for chromium-6 specifically. California PHG is 0.02 ppb. Linked to cancer risk. Reverse osmosis and anion exchange are most effective filters.
Copper in Drinking Water
Copper action level is 1.3 mg/L. High levels cause GI distress and liver damage. Caused by corrosion of copper plumbing. RO and NSF 53 carbon filters are effective.
Fluoride in Drinking Water
Fluoride in tap water — EPA limits, health effects at high levels, and state-by-state detection data.
Lead in Drinking Water
Lead in tap water causes developmental delays in children and kidney damage in adults. The EPA action level is 15 ppb. Learn how to test and filter.
Manganese in Drinking Water
Manganese in tap water — neurological effects, EPA advisory levels, and detection data across U.S. water systems.
Nitrates in Drinking Water
Nitrates exceed the EPA limit of 10 mg/L in many agricultural areas. High levels cause methemoglobinemia in infants. Reverse osmosis and ion exchange remove nitrates.
PFAS (Forever Chemicals) in Drinking Water
PFAS are synthetic chemicals linked to cancer, thyroid disease, and immune suppression. EPA set new MCLs at 4 ppt in April 2024.
Radium in Drinking Water
Radium in tap water — radioactive contamination, EPA limits, health risks, and detection data across U.S. water systems.
Radon in Homes — Risk by ZIP Code
Radon is the second leading cause of lung cancer in the U.S. EPA action level is 4 pCi/L for indoor air. Check your EPA Radon Zone and learn mitigation options.
Uranium in Drinking Water
Uranium in tap water — kidney toxicity, EPA limits, and detection data across U.S. water systems.