Water Quality: Stockton, CA

Increases blood pressure and causes cardiovascular effects with long-term exposure.

Common source: Natural rock deposits, oil drilling operations, coal power plant waste

EPA limit: 2 mg/L

Eye and nose irritation at high levels; long-term exposure above the MCL may cause liver and kidney damage.

Common source: Water treatment disinfectant added to kill harmful microorganisms

EPA limit: 4.0 mg/L (MRDL — Maximum Residual Disinfectant Level)

Causes gastrointestinal illness; certain strains (e.g., O157:H7) can cause severe kidney failure and death.

Common source: Fecal contamination from humans or animals entering the water supply

EPA limit: Zero (no E. coli permitted in drinking water)

Indicates direct fecal contamination; associated with diarrhea, cramps, nausea, and potential severe illness.

Common source: Human and animal fecal waste

EPA limit: Zero tolerance (any positive triggers violations)

Alpha-emitting radioactive particles increase cancer risk, particularly from bone and other internal cancers.

Common source: Natural uranium and radium in geological formations

EPA limit: 15 pCi/L (excluding radon and uranium)

Causes methemoglobinemia in infants and may pose cancer risks with long-term exposure.

Common source: Fertilizer runoff, septic systems, animal feedlots, natural deposits

EPA limit: 10 mg/L (as nitrogen)

Hair loss, nail brittleness, and nervous system damage at elevated concentrations.

Common source: Natural geological deposits, mining discharges, oil refinery waste

EPA limit: 0.05 mg/L (50 ppb)

Trihalomethanes and haloacetic acids that increase cancer risk and may cause adverse reproductive outcomes.

Common source: Chlorine disinfection reacting with natural organic matter in source water

EPA limit: TTHM: 0.080 mg/L; HAA5: 0.060 mg/L

Total trihalomethanes are linked to increased risk of bladder cancer and adverse reproductive outcomes.

Common source: Reaction of chlorine disinfectants with naturally occurring organic matter in water

EPA limit: 0.080 mg/L (80 ppb)

Indicates possible presence of disease-causing organisms that can cause gastrointestinal illness.

Common source: Human and animal fecal waste, soil, vegetation

EPA limit: No more than 5% of monthly samples may be positive