Gross Alpha Activity in Drinking Water

🩨 Health Effects

A measure of total radioactivity from alpha-emitting particles, primarily naturally occurring radionuclides like radium-226 and thorium. Long-term exposure above 15 pCi/L increases cancer risk.

📍 Sources in Water

Alpha radiation in groundwater comes from naturally occurring radioactive materials in rock and soil, mainly radium, uranium, and thorium. Found most often in areas with granite or uranium-bearing rock.

✅ What To Do

Reverse osmosis and distillation can reduce gross alpha activity. Ask your utility which specific radionuclides are elevated. Additional testing is usually required to identify the specific radioactive compounds.

📜 Regulation History

The EPA set the gross alpha particle activity MCL at 15 pCi/L (excluding radon and uranium) in 1976. The 2000 Radionuclides Rule reaffirmed this standard. Gross alpha is a screening test; if exceeded, further analysis for specific radionuclides (radium, uranium) is required. The WHO uses specific radionuclide guidelines rather than a gross alpha screening level.

🔬 How To Test Your Water

Certified lab tests for gross alpha cost $30-$60 and require 2-4 weeks for results due to radiological counting time. Home test kits for radioactivity are not available; professional lab analysis is required. Gross alpha testing is a screening step; if elevated, follow-up testing identifies the specific radionuclides present.

💧 Which Filters Remove Gross Alpha Activity?

Reverse osmosis (NSF/ANSI 58 certified) is effective against most alpha-emitting radionuclides. Ion exchange can remove radium and uranium (the most common alpha emitters in water). Distillation also works. The best filter depends on which specific radionuclide is causing the elevated gross alpha reading.

🔗 Related Contaminants