Drinking Water Contaminants
Understand what's in your water. In-depth profiles on regulated and emerging contaminants — EPA limits, health effects, where they come from, and how to remove them.
All contaminant profiles
45 profilesCadmium in Drinking Water: Sources, Health Risks, and Removal
Cadmium in tap water comes from galvanized pipe corrosion and industrial runoff. Learn the EPA's 5 ppb limit, kidney risks, and how to remove it.
Chlorine in Drinking Water: Why It's There, the Taste, and How to Remove It
Chlorine is the most common US tap-water disinfectant. Learn the 4.0 mg/L EPA limit, the taste-and-byproduct tradeoff, and how to filter it out.
Cyanotoxins & Harmful Algal Blooms in Drinking Water: Risks and Removal
Cyanotoxins from algae blooms have no enforceable federal limit. EPA advises microcystins at 0.3 µg/L for infants. Why you must not boil this one.
Mercury in Drinking Water: EPA Limits, Kidney Risk & Removal
EPA caps mercury in tap water at 2 ppb to prevent kidney damage. Learn why drinking water mercury differs from fish mercury, and how to filter it.
Radon in Drinking Water: The Whole-House Risk Pitchers Can't Fix
Radon in water has no enforced EPA limit and its real danger is the gas it releases into your air. Learn the risk, testing, and removal.
Selenium in Drinking Water: The Essential Nutrient That Turns Toxic
Selenium is essential at low doses but toxic in excess. EPA caps it at 50 ppb — sources, selenosis symptoms, and how to remove it.
TDS in Water: What Total Dissolved Solids Mean and Good Levels
TDS is the total of dissolved minerals in water, not one contaminant. EPA's 500 mg/L standard is aesthetic. Good levels, and what a TDS meter misses.
Cyclospora in Water: The Produce Parasite Chlorine Can't Kill
Cyclospora causes relapsing, watery diarrhea and resists chlorine. Why tap water is low-risk, how it rides fresh produce, and how to remove it.
Giardia in Drinking Water: The Backcountry Parasite Behind 'Beaver Fever'
Giardia is the most common waterborne parasite in the US. Learn how it spreads through untreated water, its symptoms, the EPA rule, and how to remove it.
TCE (Trichloroethylene) in Drinking Water: Health Risks & Removal
TCE is an IARC Group 1 human carcinogen found at over 1,000 Superfund sites. Learn the EPA limit, the Camp Lejeune link, and how to filter it out.
Asbestos in Drinking Water: The Aging-Pipe Risk Few People Test For
Asbestos in water comes from decaying asbestos-cement pipes. EPA limit is 7 million fibers per liter, plus how to test and filter it out.
Coliform Bacteria and E. coli in Drinking Water: What a Positive Test Means
A positive coliform or E. coli test signals a water-system breach. Learn the indicator-vs-pathogen distinction, EPA RTCR limits, and how to treat it.
Hardness (Calcium & Magnesium) in Water: Complete Guide
Water hardness comes from dissolved calcium and magnesium. It is not federally regulated and largely benign. Levels, effects, and how to treat it.
Iron in Drinking Water: Causes and Solutions
Iron in water causes rusty staining, metallic taste, and clogged pipes. EPA's 0.3 mg/L limit is aesthetic — plus how to remove iron for good.
VOCs in Drinking Water: TCE and PCE Contamination Guide
VOCs like TCE and PCE contaminate water near industrial and dry-cleaning sites. EPA 5 ppb MCLs, cancer risk, vapor intrusion, and removal.
Glyphosate in Drinking Water: Health Concerns & Removal
Glyphosate (Roundup) in US drinking water: EPA 700 ppb MCL, IARC Group 2A classification, agricultural runoff patterns, and proven removal methods.
Atrazine in Drinking Water: Risks from America's Most Common Herbicide
Atrazine contaminates Midwest drinking water as a corn-belt endocrine disruptor. EPA 3 ppb MCL, seasonal spikes, and how to remove it.
6PPD-Quinone in Drinking Water: The Tire Chemical Killing Salmon
6PPD-quinone is a tire-derived contaminant found in stormwater and drinking sources. No EPA limit exists. Learn the risks and what removes it.
Cryptosporidium in Drinking Water: The Parasite That Chlorine Can't Kill
Cryptosporidium is chlorine-resistant and caused the largest US waterborne outbreak ever. Learn the health risks, EPA rules, and how to remove it.
Legionella in Drinking Water: Legionnaires' Disease Risk and How to Prevent It
Legionella bacteria cause Legionnaires' disease and kill ~10% of those infected. Learn where it grows, who's at risk, and how to protect your water.
Pharmaceuticals in Drinking Water: What EPA's CCL 6 Means for Your Tap
Antidepressants, antibiotics, hormones, and painkillers reach US tap water. EPA released benchmarks for 374 drugs. Learn the risks and how to remove them.
Chlorate in Drinking Water: Thyroid Risk, EPA Levels & Removal
Chlorate is a disinfection byproduct found in many US water systems. Learn EPA limits, thyroid risks, and how to reduce chlorate at the tap.
Cobalt in Drinking Water: Health Effects, Sources & Removal
Cobalt is rarely detected in US tap water but can occur near mining or battery sites. Learn about health risks, sources, and how to remove it.
Lithium in Drinking Water: Health Effects, UCMR 5 Data & Removal
Lithium occurs in 28% of US water systems. Learn UCMR 5 data, thyroid and mood effects, state guidance values, and how to remove lithium.
Molybdenum in Drinking Water: Health Effects, EPA Levels & Removal
Molybdenum is found in groundwater across the western US. Learn EPA health advisories, gout-related effects, and how to remove molybdenum.
NDMA in Drinking Water: Cancer Risk, Sources & Removal
NDMA is a probable carcinogen formed during chloramine disinfection. Learn UCMR 2 data, California's 10 ng/L PHG, and how to remove NDMA at home.
Vanadium in Drinking Water: Health Effects, EPA Levels & Removal
Vanadium is found in many US water supplies, especially in the West. Learn about EPA health advisories, kidney effects, and how to remove vanadium.
Barium in Drinking Water: Sources and Health Effects
Barium in US drinking water comes mostly from natural groundwater dissolution. EPA sets a 2 mg/L MCL; main health concern is cardiovascular.
Uranium in Drinking Water: Health Risks & Treatment
Uranium in groundwater causes kidney damage at the EPA 30 ug/L MCL. Most common in Western US, New England granite, and Navajo Nation private wells.
Radium in Drinking Water: Risks & How to Remove It
Radium (Ra-226/Ra-228) causes bone cancer. EPA sets a 5 pCi/L MCL for combined radium. Midwest sandstone aquifers drive the highest US exposures.
Fluoride in Drinking Water: Benefits vs. Risks
Fluoride is added to 72% of US water supplies. Learn about the IQ debate, EPA limits, the 2024 court ruling, and how to remove it.
Perchlorate in Drinking Water: Health Risks & Removal
Perchlorate, a rocket fuel chemical, contaminates water in 26+ states. Learn EPA limits, thyroid risks, and proven removal methods.
Microplastics in Drinking Water: What We Know
Microplastics appear in 94% of US tap water and 240,000 particles per liter of bottled water. Learn the health risks and how to remove them.
1,4-Dioxane in Drinking Water: Health Risks, EPA Levels & Removal
1,4-Dioxane is a likely carcinogen found in drinking water near industrial sites. Learn about EPA health advisories and removal options.
Manganese in Drinking Water: Health Risks, EPA Levels & Removal
Manganese above 50 µg/L causes discolored water and health concerns. Learn about EPA limits, neurological effects, and removal methods.
Strontium in Drinking Water: Health Risks, EPA Levels & Removal
Strontium is found in most US water supplies. Learn about EPA health reference levels, bone effects, and how to remove strontium from tap water.
HAA5 (Haloacetic Acids) in Drinking Water
HAA5 are disinfection byproducts formed when chlorine reacts with organic matter. Learn about the 60 µg/L EPA limit, health risks, and how to filter them.
Arsenic in Drinking Water
Arsenic occurs naturally in groundwater across the US. Learn about EPA limits, cancer risks, and effective removal methods like reverse osmosis.
Chloramine and Chlorine in Drinking Water
Chloramine and chlorine are disinfectants added to tap water. Learn EPA limits, health concerns, and the best filters for removal.
Chromium-6 (Hexavalent Chromium) in Drinking Water
Chromium-6 is a known carcinogen found in over 75% of US water supplies. Learn about health risks, EPA gaps, and how to remove it.
Copper in Drinking Water
Copper leaches into tap water from plumbing. Learn about EPA action levels, health effects, the Lead and Copper Rule, and removal options.
Disinfection Byproducts (THMs & HAA5) in Drinking Water
Disinfection byproducts form when chlorine reacts with organic matter in water. Learn about THM and HAA5 limits, health risks, and removal.
Lead in Drinking Water: Risks and Removal
Lead enters tap water through old pipes and fixtures. Learn about EPA action levels, health effects, and the best filters to remove lead.
Nitrate in Drinking Water
Nitrate contamination comes from farming runoff and septic systems. Learn about EPA limits, blue baby syndrome, and removal methods.
What Is PFAS in Drinking Water?
PFAS are synthetic chemicals found in many US water systems. Learn what they are, health risks, EPA limits, and how to remove them.
Check your city's water
See which contaminants have been detected in your local water supply and how your city compares.