Reading a Certified Laboratory Test Report for Radon in Water
Reports show radon concentration in picocuries per liter (pCi/L)
A certified lab test for radon in water reports the concentration of radon-222, a naturally occurring radioactive gas. This measurement is expressed in picocuries per liter (pCi/L), indicating the amount of radioactive decay per minute in a liter of water.
Results include detected values and sometimes reporting limits
When radon is detected, the test lists a numerical value. If radon is below the reporting limit, it will be indicated as not detected or below detection. For Harris County's aquifer 121EVGL, all tested wells showed radon detected.
Test results apply only to the specific water source sampled
Lab reports pertain strictly to the tested sample and cannot be generalized to other wells or household taps without individual testing.
Why Aesthetic Secondary Standards Differ from Health-Based Limits for Radon
Aesthetic standards relate to taste, odor, or staining but radon uses health-based guidelines
Unlike some substances with secondary standards addressing appearance or taste, radon levels are governed by health-based federal guidelines due to its radioactive nature.
Detection does not imply a safety violation
Government sampling in Harris County showed radon detected in all examined wells but no sample exceeded federal health-based limits for radon in water.
Aesthetic concerns common with other constituents do not apply to radon
Radon in water typically does not affect taste or cause staining, unlike minerals such as iron or manganese.
Seasonal and Multi-Year Variation Documented in Harris County Radon Data
Sampling occurred over two years from mid-2013 to mid-2015
USGS monitored 23 samples from 12 wells between July 2013 and July 2015 to capture changes over time.
Radon levels ranged from 640 to 2510 pCi/L during this period
The range shows natural variability possibly influenced by factors like rainfall, groundwater flow, and aquifer depth.
Median radon concentration was 950 pCi/L
This median value provides a central tendency of radon presence in this part of Harris County aquifer 121EVGL.
Distinguishing Radon from Other Water Problems Often Confused with It
Radon is a radioactive gas, not a chemical contaminant
Unlike chemical pollutants, radon arises from the decay of uranium in soil and rock releasing gas into groundwater.
Radon does not cause discoloration or taste changes
Water issues often confused with radon include iron or sulfur, which cause visible or smell effects; radon does not.
Testing for radon requires specialized procedures different from common contaminants
Standard water tests may not detect radon. A certified laboratory radon-in-water test is necessary to confirm presence and levels.
What the Detected Range Means Relative to Federal Radon Standards
All detected radon concentrations are below federal maximum contaminant levels
In Harris County aquifer 121EVGL, none of the samples exceeded federal radon limits for drinking water, indicating compliance with health guidelines.
Detection shows radon gas presence, not health risk by itself
Detection simply means the gas was measured; risk depends on concentration and exposure pathways.
Homeowners need individual water tests to understand their specific radon levels
The government data cover area aquifer samples and cannot substitute for testing private well water.
Conclusion
Government groundwater sampling in Harris County's aquifer 121EVGL detected radon-222 in all sampled wells between 2013 and 2015, with concentrations ranging from 640 to 2510 pCi/L and a median of 950 pCi/L. None of these results exceed federal health-based standards. This dataset reflects multiple wells at depths from 1305 to 1641 feet and does not represent individual household water. For households concerned about radon, a certified lab test of their own water source is essential. The C-Series Radon in Water Filter ships ready to configure and can address radon in residential water following confirmation of radon presence. Data source: U.S. Geological Survey groundwater monitoring at https://waterdata.usgs.gov/monitoring-location/294820095342002/.
Where this information comes from
Source: USGS groundwater sampling. Sampled 2015-07-20. These figures describe groundwater sampled in this area. They are not a test of any individual private well - only a test of that well can establish its own water.
On record: U.S. Geological Survey sampling of Radon-222 in the 121EVGL aquifer (Harris County): 23 results from 12 wells, median 950.0 pCi/L, range 640.0-2510.0 pCi/L; none above any federal threshold