Nitrate in Johnston, IA Drinking Water
Nitrate data for Johnston, Iowa · 25,233 residents · 1 ZIP code
For residents of Johnston, Iowa, Nitrate has appeared in public water supply sampling data.
Data: EPA SDWIS, CCR Reports, ECHO Last verified: 2026-05-14
Nitrate in Johnston Tap Water
Nitrate has been detected in Johnston, Iowa drinking water at a maximum level of 7.15 ppb — below the EPA MCL of 10 mg/L (as nitrogen).
This analysis covers 25,233 residents across 1 ZIP code in Johnston.
Johnston's overall water quality grade is C (59/100).
Is Nitrate in Johnston Water Safe?
Nitrate was detected in Johnston water but currently falls within EPA limits. However, some health organizations argue the EPA MCL may not be protective enough.
If you are concerned, a reverse osmosis or ion exchange filter can reduce nitrate levels further.
Nitrate Levels by ZIP Code
| ZIP Code | Nitrate Level | EPA Limit | Status |
|---|---|---|---|
| 50131 | 7.15 ppm | 10 mg/L (as nitrogen) | OK |
Average nitrate level across Johnston: 7.15 ppb
Health Effects of Nitrate
- Methemoglobinemia ("blue baby syndrome") in infants under 6 months
- Increased risk of colorectal and bladder cancer (long-term)
- Thyroid disease from chronic exposure
- Possible reproductive effects
Health risk severity: High. Governed by the National Primary Drinking Water Regulations.
How Nitrate Gets Into Drinking Water
- Agricultural fertilizer runoff
- Animal feedlot operations and manure
- Septic system leachate
- Urban stormwater and wastewater discharge
What to Do About Nitrate in Johnston Water
- Reverse osmosis is the most effective method for nitrate removal
- Ion exchange systems designed for nitrate can also work
- Standard carbon filters do NOT remove nitrate
- Boiling water increases nitrate concentration — never boil for nitrate
Look for filters certified under NSF 53 / NSF 58 for nitrate removal.