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Microbial contamination indicating potential pathogens. Below are US cities ranked by their measured Bacteria levels compared to EPA limits. Higher percentages indicate greater concern.
Vulnerable Populations: Elderly, infants, immunocompromised individuals at highest risk for severe illness or death from waterborne pathogens.
Ranked by percentage of the EPA limit, using one real EPA measurement per water system. Click any city for its full report.
Historical data. Figure shown is the average of the system's 2012–2019 finished-water compliance samples (EPA Six-Year Review 4), non-detects counted as zero. Treat as history, not today's tap water.
EPA's public datasets do not carry per-system results for Bacteria in a form we can rank, so no city table is shown.
| Rank | City | State | Level | Period | EPA Limit | % of Limit | Status | Population |
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Ultraviolet light kills bacteria, viruses, and parasites without chemicals.
Physical barrier removes bacteria and other microorganisms.
Effective barrier against bacteria when properly maintained.
Total coliform indicates potential contamination. E. coli specifically indicates fecal contamination and serious health risk. Both require immediate action.
Yes. Boiling water for 1 minute (3 minutes above 6,500 ft) kills bacteria. This is the immediate response while investigating contamination.
Private wells should be tested annually for coliform bacteria, and more frequently if any changes in taste, odor, or color occur.