EPA legal limit
5 pCi/L
Maximum Contaminant Level
EWG health guideline
0.05 pCi/L
Science-based, stricter target
IARC classification
Group 1
Cancer research classification
Health effects
Radium is a bone-seeking element — it accumulates in bone and remains there. Long-term exposure above health guidelines is associated with increased bone cancer risk, leukemia, and other cancers. The EPA MCL of 5 pCi/L is 100× the EWG health guideline of 0.05 pCi/L, reflecting the gap between regulatory and science-based limits.
Where it comes from
Natural geological sources. Groundwater moving through radium-bearing rock formations dissolves radium. Most prevalent in the Midwest (particularly Illinois, Wisconsin, Iowa, and Michigan) and parts of the South.
How it's regulated
Regulated at 5 pCi/L combined radium-226+228 MCL. The EWG health guideline reflects a one-in-one-million cancer risk at 0.05 pCi/L.
The EPA vs EWG gap
The legal limit (5 pCi/L) is 100× higher than the EWG health guideline (0.05 pCi/L). Water can be legally compliant while still exceeding the science-based threshold.
How to filter radium 226+228
Not all filters address radium 226+228. Look for independently certified filters—NSF International certification means the removal claim has been independently verified.
Radium is not removed by water ionization. Reverse osmosis or ion exchange is required.
Frequently asked questions
What is radium 226+228?
Two radioactive isotopes of radium — radium-226 and radium-228 — that occur naturally in rock and soil and dissolve into groundwater. Combined radium is one of the most commonly detected radionuclides in U.S. drinking water.
What are the health effects of radium 226+228?
Radium is a bone-seeking element — it accumulates in bone and remains there. Long-term exposure above health guidelines is associated with increased bone cancer risk, leukemia, and other cancers. The EPA MCL of 5 pCi/L is 100× the EWG health guideline of 0.05 pCi/L, reflecting the gap between regulatory and science-based limits.
Is radium 226+228 regulated in drinking water?
Regulated at 5 pCi/L combined radium-226+228 MCL. The EWG health guideline reflects a one-in-one-million cancer risk at 0.05 pCi/L.
Where does radium 226+228 come from?
Natural geological sources. Groundwater moving through radium-bearing rock formations dissolves radium. Most prevalent in the Midwest (particularly Illinois, Wisconsin, Iowa, and Michigan) and parts of the South.
How do I remove radium 226+228 from tap water?
The most effective methods for removing radium 226+228 are: Reverse osmosis (RO), NSF 58 certified RO system, Ion exchange resin. Look for NSF-certified systems—independent certification confirms removal claims have been verified.
Is radium 226+228 in your water?
Enter your ZIP code to see the measured level in your specific utility.