What the action level is
The federal lead action level is 15 micrograms per litre (µg/L). It is not a health-based limit; it is a treatment trigger. When a water system’s 90th-percentile tap sample exceeds it, the utility must take defined steps such as corrosion-control treatment and public notification. Reading the federal Lead & Copper Rule records against that trigger, PurityMap counted the water systems whose most recent monitored result came back above it.
Lead is different from most contaminants in one important way: public-health agencies state there is no known safe level of lead exposure. So an action level is a compliance threshold, not a line below which lead is harmless.
90th-percentile result: utilities sample a set of higher-risk homes; the value reported is the level that 90% of those samples fall below. It describes the system’s monitored performance, not any single household’s tap.
What the records find
Across the water systems that serve a city with a PurityMap report, 4,135 have a lead 90th-percentile result from the last ten years on record, and 18 of them reported a 90th-percentile result above the 15 µg/L action level. The highest are the systems serving Troy, New York (110 µg/L), Wabash, Indiana (38 µg/L) and Aliquippa, Pennsylvania (33.5 µg/L). The full ranking lists each system above the action level, with its result, its monitoring period and a link to the city report and its source.
Because several cities can share one serving water system, these counts are of systems, and the ranking lists each system once. You can see the complete list on the ranking of U.S. cities where lead exceeds the federal action level.
How strong the evidence is
These figures come from EPA SDWIS Lead & Copper Rule compliance records. They describe monitored public-system performance for the reporting period, using the 90th-percentile statistic the rule defines. Two caveats matter. A system below the action level is not necessarily lead-free: the trigger is a percentile, not a guarantee about every home. And a system’s result reflects its distribution network, while the lead that reaches a specific tap is also shaped by that building’s own plumbing and service line.
What it means at home
Lead at the tap often comes from premise plumbing (older pipes, brass fixtures, and lead service lines) rather than the water a utility delivers. That means two things. If your city is on this list, the system-level record is elevated and worth acting on. But even if it is not, a home with pre-1986 plumbing can still add lead at the tap, which a public-system record cannot detect. The only way to know your own tap is a certified home test.
What to do next
Confirm your serving system and open its lead finding to see the exact 90th-percentile result and its source. If lead is a concern for your home, a filter independently certified to NSF/ANSI 53 for lead reduction, or a reverse-osmosis system, is the common point-of-use step, and running the tap before drinking can reduce standing-water lead in older plumbing.
PurityMap’s filter guidance is evidence-based, not paid placement. Some links are affiliate links and PurityMap may earn from qualifying purchases at no extra cost to you; that never changes which products the records support.
This article is general information, not medical advice. Public-system monitoring records are not a measurement of the water at your specific tap. For decisions about your health or your household’s water, especially where infants or pregnancy are involved, consult a qualified professional and test your own water.