How much disinfection byproduct is in the water?

When chlorine meets the organic matter in river and reservoir water it forms trihalomethanes and haloacetic acids, the most common contaminants actually measured in Ohio tap water. EPA's Six-Year Review file holds every compliance sample from 2012 through 2019; the map shows the latest yearly mean of total trihalomethanes for the system serving each ZIP against the 80 µg/L annual-average limit, and the card adds haloacetic acids (limit 60), the highest nitrate, arsenic, radium, gross alpha and uranium results, and how many samples sit behind each number. Well systems usually run low; big surface-water systems sit closer to the line, especially in late summer.

671 of 1,233 ZIPs have data; median 35.4 µg/L.

Legend

Under 20 µg/L TTHM · 110 20 to 40 · 316 40 to 60 · 211 60 to 80 · 30 80 or more · 4 No data · 562

Map of Ohio by Disinfection byproducts

Highest and lowest

Source

EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019: total trihalomethanes and haloacetic acids (HAA5) sampled in the distribution system, nitrate, arsenic, combined radium, gross alpha and uranium at entry points; yearly means by system, non-detects as zero; benzene, carbon tetrachloride, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene and vinyl chloride from the same files; atrazine, alachlor, 2,4-D, chromium, cadmium, barium, mercury, selenium and thallium likewise; total coliform and E. coli distribution samples from the same review (presence or absence)

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Cracked Buckeye (Open Shower Co), "Disinfection byproducts", https://crackedbuckeye.com/topics/dbp/, built 2026-09-16, accessed [date].

Machine-readable: /api/topics/dbp.json (open JSON, CC BY 4.0 for the compilation; the underlying records keep their own terms) · How to cite · Report a correction · Built 2026-09-16