Berwyn

What it means: The 1991 LCR uses action levels rather than MCLs: if the 90th percentile of high-risk tap samples exceeds 15 ppb lead or 1.3 mg/L copper, the system must take escalating corrective actions. Violations typically indicate failure to maintain adequate corrosion control — the treatment that keeps lead from leaching out of pipes, solder, and fixtures.

Health effects: Lead: no safe level for children. Causes irreversible neurological damage, impaired cognitive development, behavioral problems, and reduced IQ in children under 6. In adults: hypertension, cardiovascular disease, kidney damage. Copper: acute gastrointestinal distress at high levels; liver/kidney damage at very high chronic levels.

Limit: Action levels: lead 15 ppb, copper 1.3 mg/L — 90th percentile of tap samples at high-risk sites

What it means: TTHMs are four compounds — chloroform, bromodichloromethane, dibromochloromethane, bromoform — formed when chlorine reacts with organic matter in water. They are among the most common disinfection byproducts and form more readily in surface water systems with high organic loads.

Health effects: Long-term exposure is associated with increased bladder cancer risk. Some studies link high TTHM exposure to adverse reproductive outcomes. Bromodichloromethane is classified as a possible human carcinogen.

Limit: 0.080 mg/L (80 ppb) locational running annual average (LRAA)

What it means: HAA5 are five haloacetic acids formed when chlorine disinfectants react with naturally occurring organic matter in source water. Higher levels occur with more organic-rich source water or when water sits longer in distribution pipes. The violation indicates the locational running annual average exceeded the MCL.

Health effects: Dichloroacetic acid is a probable human carcinogen (Group B2). Long-term exposure to trichloroacetic acid may also increase cancer risk. Animal studies show liver, kidney, and reproductive effects at high doses.

Limit: 0.060 mg/L (60 ppb) locational running annual average (LRAA)