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Have algal toxins reached the water?

Since the August 2014 weekend when Toledo told half a million people not to drink the tap water, Ohio EPA has had every surface-water system test its raw and treated water for microcystin through the bloom season. The map shows the highest raw-water reading since 2016 at the intake of the system serving most of each ZIP, which is what the plant has had to remove; the card adds any detections in treated water against the 0.3 and 1.6 microgram-per-litre advisory levels, and the seasons in which the bloom reached the intake. Groundwater systems are not monitored and stay grey. Grand Lake St. Marys, the state's most bloom-prone lake, gives Celina the worst raw-water readings in Ohio, and the western Lake Erie intakes at Toledo, Oregon and Ottawa County see the summer bloom most years.

409 of 1,233 ZIPs have data; median 0.5 µg/L.

Monitored, no microcystin found · 59 Under 5 µg/L in raw water · 277 5 to 20 µg/L · 62 20 to 100 µg/L · 10 100 µg/L or more · 1 No data · 824

Highest and lowest

Highest

  1. 45822 · Celina193.9 µg/L
  2. 43438 · Kelleys Island30 µg/L
  3. 43619 · Northwood25 µg/L
  4. 43616 · Oregon25 µg/L
  5. 43447 · Lake Township and Millbury25 µg/L
  6. 43434 · Harbor View25 µg/L
  7. 43430 · Genoa25 µg/L
  8. 43452 · Port Clinton22.3 µg/L
  9. 43439 · Erie Township and Lacarne22.3 µg/L
  10. 43416 · Elmore22.3 µg/L
  11. 45872 · North Baltimore20 µg/L
  12. 45833 · Delphos19.2 µg/L
  13. 45663 · Washington Township and West Portsmouth17.4 µg/L
  14. 45662 · Portsmouth17.4 µg/L
  15. 45630 · Nile Township and Friendship17.4 µg/L

Lowest

  1. 43003 · Ashley0 µg/L
  2. 43011 · Hilliar Township and Centerburg0 µg/L
  3. 43021 · Genoa Township and Galena0 µg/L
  4. 43032 · Brown Township and Kilbourne0 µg/L
  5. 43035 · Orange Township and Lewis Center0 µg/L
  6. 43055 · Newark0 µg/L
  7. 43061 · Scioto Township and Ostrander0 µg/L
  8. 43065 · Powell0 µg/L
  9. 43066 · Radnor Township and Radnor0 µg/L
  10. 43074 · Sunbury0 µg/L
  11. 43082 · Genoa Township and Westerville0 µg/L
  12. 43314 · Claridon Township and Caledonia0 µg/L
  13. 43315 · Cardington0 µg/L
  14. 43317 · Chesterville0 µg/L
  15. 43320 · Canaan Township and Edison0 µg/L

Source

Ohio EPA public water system harmful algal bloom monitoring (geo.epa.ohio.gov DrinkingWater/HAB): microcystin results in raw and treated water since 2016 for surface-water systems, for the system serving most of each ZIP

Ohio EPA HAB information for public water systems

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More in Water

Where the water comes fromIntakes and plantsViolationsDisinfection byproductsPFASLeadFluoride and treatmentGroundwaterAquiferSewage plantsStream healthWatershed

Cite this page as:

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

Machine-readable: /api/topics/algae.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