Selenium in Tap Water
Selenium is a trace element that is an essential nutrient in tiny amounts but is regulated in drinking water because higher levels from natural deposits or runoff can be harmful.
Natural erosion of selenium-bearing rock and soils; irrigation drainage and mining can concentrate it.
- 1Natural mineral deposits
- 2Irrigation drainage
- 3Mining discharge
A result is read with its context
This contaminant is tracked through federal and state compliance monitoring. Wells in seleniferous soils or near irrigated farmland should be tested. PurityMap does not yet publish a per-system measured value for Selenium; this page is a reference explainer. To learn what is in your own water, check your utility’s Consumer Confidence Report (CCR) or use a certified home test.
- Above reference
- Evidence exceeds a reference level.
- Detected
- This substance was found in the monitoring record. Being present is not the same as being above a reference level, and this signal does not say which.
- Not detected
- Somebody looked and the laboratory reported nothing above its reporting limit. This is a result, and it is not the same as nobody looking.
- Not monitored
- No sampling for this substance has been reported for this system. Nothing is known either way, and an empty row is not a clean one.
No city results or violations published yet
- MeasurementsPendingNo per-system values
PurityMap does not yet publish a measured value for selenium.
- ViolationsCheckedNone on the federal record
No city in PurityMap’s record has a selenium violation in EPA SDWIS since 2016.
- CitiesPendingNo detections on record
No city in PurityMap’s record shows selenium detected.
This fills in as monitoring data is published. Until then, your utility’s Consumer Confidence Report lists its results, or use a certified home test.
What can carry a selenium reduction claim
- Reverse osmosis
Semi-permeable membrane separation removing dissolved minerals, heavy metals, and persistent fluorinated chemicals down to 0.0001 microns.
- Anion exchange
Synthetic polyvalent resin beads that exchange unwanted dissolved ionic contaminants for harmless benchmark ions.
- Activated alumina
Boiling does not remove a dissolved chemical compound and can concentrate it. Many pitcher and refrigerator filters carry no verified claim for a compound like this at all.
A finding establishes the need, the need names the capability, the capability requires a verified certification. No product appears before that sequence completes. Filter Finder →
Frequently asked
Answers cite the same records as the page. How PurityMap analyzes water data
Selenium is a trace element that is an essential nutrient in tiny amounts but is regulated in drinking water because higher levels from natural deposits or runoff can be harmful.
The enforceable federal limit is 0.05 mg/L / 50 µg/L (MCL). The health-based goal (MCLG) is 0.05 mg/L. PurityMap reads every measurement against its stated benchmark and never sets its own.
Natural mineral deposits, Irrigation drainage, Mining discharge.
Selenium is needed in trace amounts, but sustained exposure above the limit is linked to hair and nail changes and to circulatory and nervous-system effects. The enforceable limit separates the nutritional range from the range of concern.
Treatment technologies commonly certified to reduce Selenium include Reverse osmosis, Anion exchange, Activated alumina. Match the exact certified claim to your water before buying. Holding a format is not the same as holding the claim.