Strontium is a metal that rapidly turns yellow when exposed to open air. In nature is it not radioactive but can occur in the form for radioactive isotopes, such as strontium-90 (Sr-90), a byproduct of nuclear fission with a half-life of 29 years. As far as drinking water is concerned, strontium is an unregulated contaminant that is tracked but not regulated by the EPA at 1.5 milligrams per liter (mg/L).
Unlike Sr-99, ingesting small amounts of naturally occurring strontium has not been found to be harmful in humans.
- Chemical symbol: Sr
- Atomic number: 38
- CAS Number: 7440-24-6
- MRL: 0.3 µg/L (parts per billion)
- HRL: 1500 µg/L (parts per billion)
- MCL (Maximum Contaminant Level): 4 millirems per year
Strontium in Drinking Water
Strontium is widely present in nature because of nuclear weapon testing, which largely took place in the 1950s and 1960s but also entered the environment from nuclear accidents like fallout from the 1986 Chernobyl disaster and 2011’s Fukushima Daiichi Nuclear Power Plant (though neither had a significant impact on US levels). Given the half-life of the material it is decaying over time, but it can still be found in amounts well above the minimum reporting level (MRL) in the water of parts of the United States. Strontium also has assorted industrial, commercial (for example radio-luminescent markers), and medical uses so it’s more widely prevalent than one might suspect.
Strontium — in this case Sr-90 — is taken into the body through both food and water (not normally breathed in in significant amounts), where it acts like calcium. This is problematic because, like calcium, it enters the teeth and bones. It is a carcinogen for the bones, tissue around bones, and marrow. Strontium is not considered to be overly toxic, but can be particular concern for pregnant women and small children who are rapidly taking on calcium that will be with them for many years to come.
Treatment for Strontium
If you are concerned about radioactive strontium in your water, the EPA has recommended ion exchange and reverse osmosis filtering as the as Best Available Technologies for removal. (Source, EPA Radionuclides Notice of Data Availability: Technical Support Document, March 2000)