Radon in Baltimore County Water: Understanding 400BLMR Aquifer Variability

Opening: What Government Sampling Reveals About Radon in Baltimore County

The U.S. Geological Survey sampled three wells from the 400BLMR aquifer in Baltimore County between February 2019 and January 2020, detecting radon-222 in all samples. Median radon levels were 3,470 pCi/L, with values ranging from 227 to 4,900 pCi/L. Each well was 200 to 300 feet deep. This data reflects regional groundwater radon presence, not the concentration in any individual household water supply.

1. How Public-System Records Differ from Private-Well Testing

Government records like the USGS sampling provide a general profile of radon in area aquifers. These results summarize multiple wells and do not represent a single household’s water quality. In contrast, private well owners must conduct specific tests on their own water to determine radon levels accurately. Public data cannot confirm or rule out radon presence or concentration at a particular home.

2. Understanding the Measured Range Versus Federal Standards

The recorded radon values in this regional sampling fall below federal action thresholds established for drinking water. Detection of radon does not mean a legal violation or an unsafe condition. Instead, these figures describe the range of radon naturally occurring in the aquifer. The federal standards serve as guidelines for when treatment is recommended, not as direct safety limits at detection.

3. What the Number of Samples and Wells Indicates

The radon data derives from only three samples collected in separate wells over nearly a year. This small sample size provides an initial regional snapshot but cannot capture all variability in the aquifer. Larger studies would be needed to refine understanding of typical radon levels. For homeowners, this limitation means regional data is informative but not conclusive for private water supply decisions.

4. Differentiating Radon from Other Common Water Concerns

Radon in water is distinct from problems like iron staining or sulfur odor, which affect taste and appearance but result from different substances. Radon is a radioactive gas that can dissolve in groundwater, posing a different category of concern. Recognizing this difference helps clarify why specific water treatment approaches are necessary for radon versus other conditions.

5. Seasonal and Multi-Year Variation in Radon Occurrence

Samples spanning nearly one year indicate radon concentration in the 400BLMR aquifer can fluctuate. The range from 227 to 4,900 pCi/L shows variability, likely influenced by seasonal or geological factors. Such variation means a single test provides a snapshot, while multiple tests over time give a fuller picture of radon presence.

Closing: The Essential Test to Confirm Your Water’s Radon Level

To determine the radon concentration in your specific household water, a certified laboratory test on a sample from your well or supply line is essential. This test, measuring radon-222 in pCi/L, will provide data specific to your water. Should radon levels be a concern, the Pentair Radon in Water Filter ships ready to configure for household use and can effectively reduce radon in your water supply.

Where this information comes from

Source: USGS groundwater sampling. Sampled 2020-01-13. 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 400BLMR aquifer (Baltimore County): 3 results from 3 wells, median 3470.0 pCi/L, range 227.0-4900.0 pCi/L; none above any federal threshold