STOCKTON, California Tap Water Quality

What this violation means

Nitrate contamination is most acute in agricultural regions where fertilizer and animal waste leach into groundwater. The immediate risk is to formula-fed infants under 6 months — high nitrate levels prevent their blood from carrying oxygen, causing 'blue baby syndrome.' Pregnant women should also avoid high-nitrate water.

Recommended precautions

• →Never give untreated high-nitrate water to infants — use bottled water for formula.
• →Boiling does NOT remove nitrate. Boiling concentrates it.
• →Reverse osmosis, ion exchange, or distillation are the only effective home treatments.
• →Private well owners in farming areas should test annually for nitrate.

What this violation means

Arsenic is a known human carcinogen that occurs naturally in groundwater across many parts of the United States, especially the Southwest and parts of New England. Long-term exposure even at low levels has been linked to bladder, lung, and skin cancer, as well as cardiovascular disease and developmental effects in children.

Recommended precautions

• →Reverse osmosis filtration removes arsenic effectively.
• →Distillation also removes arsenic — point-of-use distillers work for drinking and cooking water.
• →Boiling does NOT remove arsenic. It actually concentrates it as water evaporates.
• →If your well water has arsenic, test annually and treat at the point of entry.

What this violation means

Haloacetic Acids (HAA5) are the second major group of disinfection byproducts after TTHMs. They form by the same mechanism — chlorine reacting with organic matter — and pose similar long-term cancer risks. Utilities are required to test quarterly at distribution-system locations to track HAA5 levels.

Recommended precautions

• →Activated carbon filtration removes most HAA5.
• →Reverse osmosis is highly effective.
• →Unlike TTHMs, HAA5 do not significantly off-gas. Use treatment rather than aeration.
• →Long-term ingestion is the primary concern, not short-term skin contact.

What this violation means

Total coliform bacteria are themselves usually harmless, but their presence signals that the water distribution system has a vulnerability — typically a cracked pipe, loss of pressure, or back-siphonage — that could allow disease-causing pathogens to enter. Repeated coliform-positive samples trigger mandatory utility investigation.

Recommended precautions

• →If your utility issues a boil-water advisory, boil all drinking and cooking water for at least one minute.
• →Use bottled water until the advisory is lifted.
• →Ice from icemakers and beverages made before the advisory should be discarded.
• →UV light and chlorination both kill coliform bacteria — most home filters do not.

What this violation means

Lead is a potent neurotoxin with no safe exposure level. In drinking water it primarily enters via corroded lead service lines, lead-soldered copper pipes, and brass fixtures. Children under 6 and pregnant women face the highest risk because lead disrupts developing nervous and skeletal systems.

Recommended precautions

• →Run cold tap water 30–120 seconds before drinking or cooking, especially after the tap has been unused for hours.
• →Never cook with hot tap water — heat increases lead leaching from pipes.
• →Use an NSF/ANSI 53 certified filter for lead removal (carbon block or reverse osmosis).
• →If you have children, get blood lead levels tested by your pediatrician.

What this violation means

Total Trihalomethanes (TTHMs) form when chlorine reacts with naturally occurring organic matter — leaves, soil, algae — in source water. They are among the most commonly reported violations because utilities pulling from surface water (rivers, lakes, reservoirs) struggle to balance disinfection with byproduct formation. Long-term exposure has been linked to bladder cancer and adverse pregnancy outcomes.

Recommended precautions

• →Activated carbon filters (pitcher, faucet, or under-sink) effectively reduce TTHMs.
• →Letting water sit uncovered allows TTHMs to off-gas — leave a pitcher in the fridge for several hours.
• →Shower with the bathroom fan on; TTHMs can volatilize into the air during hot showers.
• →Boiling reduces TTHMs through volatilization, but only after extended boiling.