Beta Particles and Photon Emitters
Beta particles and photon emitters are radioactive contaminants that EPA regulates as a DOSE: the limit is 4 millirems per year of whole-body or organ dose, not a concentration. Some water reports print the figure that way, in millirems per year, often labelled "man-made beta". That is a different measurement from gross beta activity, which a laboratory reports in picocuries per litre as the raw activity of a sample; the two are not interchangeable and cannot be compared with each other's limits.
EPA MCLG
0 mrem/year
EPA's health goal is zero — no known safe level of exposure. This is a goal, not an enforceable limit.
Health Effects
Increased risk of cancer
Source: EPA — National Primary Drinking Water Regulations (retrieved 2026-07-27)
Common Sources
- Decay of natural and man-made deposits of certain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation
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The EPA MCLG for Beta Particles and Photon Emitters is 0 mrem/year. Upload your water test (PDF or a photo) and we'll email a plain-English reading of where your result lands — and every other number — free. Educational only, no medical claims.
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Water filters certified under the following NSF standards are effective at removing Beta Particles and Photon Emitters:
Filter recommendations for this contaminant are being updated.
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About the EPA MCLG
The EPA MCLG is the level of a contaminant in drinking water below which there is no known or expected risk to health. It is a non-enforceable public health goal, and is often stricter than the legal limit (MCL) water systems must meet.
Contaminant Type
Beta Particles and Photon Emitters is classified as a Radionuclides contaminant.
Related Radionuclides Contaminants
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