Water Contaminants Guide

EPA MCL: 4 ppt

Associated with increased risk of certain cancers, liver effects, immune system effects, thyroid disease, and developmen...

EPA MCL: 4 ppt

Associated with increased risk of certain cancers, immune system effects, thyroid disease, elevated cholesterol, and dev...

EPA MCL: 10 ppt

Associated with liver toxicity, kidney effects, developmental toxicity, and cancer in animal studies. Developed as a rep...

The PFAS class includes thousands of synthetic compounds linked to various health effects including cancer, immune suppr...

Short-chain PFAS with lower bioaccumulation than PFOA/PFOS but still persistent. Associated with thyroid effects, reprod...

Short-chain PFAS with the shortest half-life in humans among commonly detected PFAS (~3 days vs years for PFOA). Associa...

Iron is an aesthetic (nuisance) contaminant, not a health hazard at the levels typically found in drinking water. The EP...

Hydrogen sulfide in water is a nuisance issue, not a known health risk at the low concentrations typically found in well...

Sediment (suspended sand, silt, clay, or rust) and the cloudiness it causes — turbidity — are primarily an aesthetic and...

Manganese is unusual: it's an essential nutrient at low levels, a staining nuisance at moderate levels, and a potential ...

TDS (total dissolved solids) is the combined weight of all dissolved minerals, salts, and metals in water — an AGGREGATE...

EPA MCL: 0.015 mg/L

In children: delays in physical and mental development, learning difficulties, lower IQ, attention deficit problems. In ...

EPA MCL: 0.01 mg/L

Skin damage, circulatory system problems, increased risk of skin, bladder, lung, kidney, and liver cancer. Long-term exp...

EPA MCL: 0.002 mg/L

Kidney damage with long-term exposure. Short-term exposure at high levels can cause nausea, diarrhea, and other gastroin...

EPA MCL: 0.1 mg/L

Known human carcinogen when inhaled; associated with stomach and intestinal tumors in animal studies when ingested. Also...

EPA MCL: 0.005 mg/L

Kidney damage with long-term exposure. Also associated with bone fragility (osteoporosis), liver damage, and classified ...

EPA MCL: 4 mg/L

At levels above 4.0 mg/L: bone disease (skeletal fluorosis). At levels above 2.0 mg/L: dental fluorosis (mottled teeth) ...

EPA MCL: 10 mg/L

Methemoglobinemia ('blue baby syndrome') in infants under 6 months - nitrate reduces the blood's ability to carry oxygen...

EPA MCL: 1 mg/L

Same as nitrate - methemoglobinemia ('blue baby syndrome') in infants under 6 months. Nitrite is more acutely toxic than...

EPA MCL: 2 mg/L

Increased blood pressure with long-term exposure. Gastrointestinal disturbances with short-term exposure. Potentially ha...

EPA MCL: 1.3 mg/L

Short-term: gastrointestinal distress (nausea, vomiting, diarrhea). Long-term: liver damage, kidney damage. People with ...

Not a health hazard - calcium and magnesium are essential minerals. Hard water is primarily an aesthetic and household m...

EPA MCL: 0.08 mg/L

Liver, kidney, and central nervous system problems. Increased risk of bladder and colorectal cancer with long-term expos...

EPA MCL: 0.06 mg/L

Increased cancer risk with long-term exposure. Some haloacetic acids are classified as probable or possible human carcin...

Classified as a probable human carcinogen (Group B2) by EPA. Associated with liver and kidney damage, central nervous sy...

Classified as a probable human carcinogen (Group B2) by EPA with an MCLG of zero. Associated with liver and kidney damag...

Total coliforms are indicator organisms - their presence suggests the water system may be vulnerable to contamination by...

EPA MCL: 0 presence/absence

Indicates fecal contamination and potential presence of dangerous pathogens. Certain strains (e.g., O157:H7) can cause s...

Gastrointestinal illness including severe diarrhea, stomach cramps, nausea, and dehydration. Cryptosporidium can be life...

EPA MCL: 5 pCi/L

Increased risk of bone cancer with long-term exposure. Radium accumulates in bones and emits radiation that can damage s...

EPA MCL: 0.03 mg/L

Kidney toxicity (nephrotoxicity) with long-term exposure - uranium is a heavy metal that damages the kidneys. Also a rad...

EPA MCL: 4 mg/L

Eye and nose irritation, stomach discomfort at levels above the MRDL. Chlorine itself is not the primary concern - it is...

EPA MCL: 4 mg/L

Eye and nose irritation, stomach discomfort, and anemia at levels above the MRDL. Toxic to fish and aquatic life - aquar...

EPA MCL: 0.003 mg/L

Cardiovascular system and reproductive problems with long-term exposure. Associated with hormonal disruption (endocrine ...

Classified as a likely human carcinogen by EPA. Associated with liver and kidney damage in animal studies. EPA health ad...

Emerging area of research. Potential concerns include inflammation, oxidative stress, and toxicity from the plastic part...

Contaminants of emerging concern. Potential effects include endocrine disruption, antibiotic resistance development, and...