Contaminant Guides

PFAS are a group of thousands of man-made chemicals that have been used in industrial and consumer products since the 1940s. They do not break down in the environment or the human body, earning the name 'forever chemicals.' In April 2024, the EPA set the first-ever federal limits for six PFAS compounds in drinking water.

EPA limit: 4 ppt

Lead enters drinking water primarily through corrosion of lead service lines and lead-containing plumbing fixtures — not typically from the water source itself. There is no safe level of lead exposure for children. The EPA is revising its Lead and Copper Rule to eliminate lead service lines nationwide by 2037.

EPA limit: 15 ppb (action level)

Arsenic is a naturally occurring metalloid found in geological deposits across the western United States, New England, and the Midwest. It can also enter water through industrial processes. Long-term exposure is strongly linked to bladder, lung, and skin cancer. The EPA reduced the arsenic MCL from 50 ppb to 10 ppb in 2001, though some researchers advocate for an even lower limit.

EPA limit: 10 ppb

Nitrates are colorless, odorless compounds that occur naturally in soil but reach dangerous levels in water primarily from agricultural fertilizer runoff and septic system leakage. They pose a serious risk to infants under 6 months, who can develop methemoglobinemia (blue baby syndrome). The EPA MCL is 10 mg/L as nitrogen.

EPA limit: 10 mg/L

Disinfection byproducts form when chlorine or other disinfectants react with naturally occurring organic matter in source water. The two main regulated groups are total trihalomethanes (TTHMs) and haloacetic acids (HAA5). They are an unavoidable tradeoff of water disinfection — the risk of not disinfecting far outweighs the risk of DBPs, but minimizing exposure is prudent.

EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)

Hard water contains elevated levels of dissolved calcium and magnesium. It is not a health risk and is associated with some cardiovascular benefits, but it causes scale buildup in pipes and appliances, soap scum, and reduces the effectiveness of detergents. Approximately 85% of U.S. homes have hard water. It is an aesthetic and infrastructure issue, not a regulatory one.

EPA limit: No federal limit