Lead in Drinking Water
There is no known safe level of lead exposure; EPA's health goal (MCLG) for lead is zero. Lead usually enters water from lead service lines, solder and brass fixtures in contact with water, not from the source water.
Under the Lead and Copper Rule, systems sample home taps and act if the 90th-percentile result is above the 0.015 mg/L (15 ppb) action level. EPA's Lead and Copper Rule Improvements (finalized October 2024) lower the action level to 0.010 mg/L and require replacing most lead service lines, with compliance starting in 2027.
Your home plumbing matters. Homes built before 1986 are more likely to have lead pipes, solder or fixtures. Flush the tap if water sat for hours, use cold water for drinking and cooking, and consider testing your own tap. Filters certified to NSF/ANSI 53 or 58 for lead reduction are an option.
Detection vs violation
- Detection: a lab found a substance. Many substances are detected at levels below the legal limit.
- MCL (legal limit): the highest level EPA allows. Going over it, usually as an average over time, is a violation.
- MCLG: a health goal with no enforcement. It can be zero (for lead it is zero).
- Action level (lead and copper): a trigger for extra steps such as corrosion control and public education. Exceeding it is not a violation by itself.
- Monitoring or reporting violation: a test or report was late or missing. It does not by itself mean a contaminant was too high.