What was found in Johnston's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate | 1000 µg/L 10% of the EPA limit 10000 µg/L Highest in the city: CAMP DODGE WATER SUPPLY · 1,169 people · 2019 | 1/2 | SYR4 |
| Nitrite | 815 µg/L 82% of the EPA limit 1000 µg/L Highest in the city: CAMP DODGE WATER SUPPLY · 1,169 people · 2016 | 1/2 | SYR4 |
| Fluoride | 300 µg/L 7.5% of the EPA limit 4000 µg/L Highest in the city: CAMP DODGE WATER SUPPLY · 1,169 people · 2013 | 1/2 | SYR4 |
| Copper | 173.5999999999998 µg/L 13% of the EPA limit 1300 µg/L Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| TTHM | 74.3 µg/L 93% of the EPA limit 80 µg/L Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Barium | 49.5 µg/L 2.5% of the EPA limit 2000 µg/L Highest in the city: CAMP DODGE WATER SUPPLY · 1,169 people · 2013 | 1/2 | SYR4 |
| Chloroform | 49.2 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Lithium | 33 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2025 | 1/2 | UCMR-5 |
| Total Haloacetic Acids (HAA5) | 25.2 µg/L 42% of the EPA limit 60 µg/L Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Bromodichloromethane | 19.595 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Dichloroacetic Acid | 13.789999999999997 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Dibromochloromethane | 11.4 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Lead | 11.394999999999985 µg/L 76% of the EPA limit 15 µg/L Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Monochloroacetic Acid | 9.468999999999998 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019
Highest in the city: 9.715499999999997 µg/L — CAMP DODGE WATER SUPPLY · 1,169 people · 2019 | 2/2 | SYR4 |
| Trichloroacetic Acid | 5.725999999999999 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019
Highest in the city: 6.513 µg/L — CAMP DODGE WATER SUPPLY · 1,169 people · 2019 | 2/2 | SYR4 |
| Monobromoacetic Acid | 3.6575 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 1/2 | SYR4 |
| Bromoform | 3.1969999999999987 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Arsenic | 3.1949999999999994 µg/L 32% of the EPA limit 10 µg/L Highest in the city: CAMP DODGE WATER SUPPLY · 1,169 people · 2019 | 1/2 | SYR4 |
| Dibromoacetic Acid | 3.0300000000000002 µg/L No EPA limit set Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2019 | 2/2 | SYR4 |
| Chromium | 2.1 µg/L 2.1% of the EPA limit 100 µg/L Highest in the city: CAMP DODGE WATER SUPPLY · 1,169 people · 2013 | 1/2 | SYR4 |
| Asbestos | 1 MFL 14% of the EPA limit 7 MFL Highest in the city: CAMP DODGE WATER SUPPLY · 1,169 people · 2019 | 1/2 | SYR4 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: JOHNSTON MUNICIPAL WATER SUPPLY · 24,897 people · 2025
Highest in the city: 0.0020 mg/L — CAMP DODGE WATER SUPPLY · 1,169 people · 2025 | 2/2 | LCR |
Each bar shows the measured level as a share of the EPA limit: green is
well under, amber is close to it, red is over. For lead and copper the
limit applies to exactly the 90th-percentile figure shown, so red there
means a real exceedance. For everything else the limit applies to a
running annual average while the figure is the 95th percentile of the
system's samples — over 100% is worth reading, but is not by itself a
violation.
Formal violations are listed separately.
These are the utilities' own EPA-reported results, not a city-wide
average. A detection means the lab measured the
substance — it isn't the same as exceeding a legal limit. Hover a source
tag to see the EPA program and years behind each figure.
Water suppliers serving Johnston
| Supplier | Population served |
|---|---|
| JOHNSTON MUNICIPAL WATER SUPPLY | 24,897 |
| CAMP DODGE WATER SUPPLY | 1,169 |
Frequently asked questions about Johnston tap water
Is Johnston tap water safe to drink?
EPA testing detected 22 contaminants in the water serving Johnston. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve Johnston?
2 public water suppliers report drinking-water monitoring for Johnston, Iowa to the EPA. Each is listed above with its population served.
What contaminants are in Johnston's water?
The contaminants EPA monitoring detected in Johnston include Nitrate, Nitrite, Fluoride, Copper, TTHM. The full list, with the level at the main supplier and the data source, is in the table above.
Where does this data come from?
Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.