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Strontium is an alkaline earth metal that is found naturally in the minerals celestine and strontianite. Strontium shares many physical and chemical properties with calcium and barium and is highly susceptible to chemical changes.

Strontium has 16 known isotopes. Strontium that occurs naturally in the earth has four stable isotopes Sr-84, -86, -87, and -88. Twelve other strontium isotopes are unstable, meaning they are radioactive. Strontium-90 is the most prevalent radioactive isotope in the environment, although strontium-89 can be found around nuclear reactors. Strontium-85 is used in bone imaging processes by the medical field.
Strontium occurs naturally in the environment. Air, dust, soil, foods and drinking water all contain small amounts of strontium. Ingestion of small amounts of strontium is not harmful. However, high levels of strontium can occur in water drawn from bedrock aquifers that are rich in strontium minerals. Strontium occurrence is also linked to other sources such as air contamination from milling processes, coal burning and phosphate fertilizers. In some cases, low levels of strontium have been administered to osteoporosis patients as a treatment of their condition.
The risk posed by strontium depends on the concentration ingested and on the exposure conditions and the U.S. environmental Protection Agency’s current reference concentration indicates that ongoing exposure to strontium at levels of more than 4000 parts per billion per day may lead to negative health effects. There is no evidence that drinking water with trace amounts of naturally-occurring strontium is harmful.

However, exposure to high levels of naturally-occurring strontium during infancy and childhood can affect bone growth and cause dental changes, and there is some evidence that strontium increases bone density in adults. The isotope strontium-90 has been linked to bone cancers and leukemia.
As part of its Third Unregulated Contaminant Monitoring Rule testing, the EPA is examining how prevalent strontium is in U.S. drinking water supplies and at what level it occurs. Under the recent round of UCMR3 testing, many water systems nationwide tested for “total strontium.” In other words, they tested for strontium in all its forms, rather than breaking it out into its various isotopes.

Your water system publishes the results of total strontium tests in a consumer confidence report each year and makes that report publicly available. The report is often available on the internet, but you may need to contact your water provider to request a copy. Contact your public water system to learn more about strontium testing and results. You can usually find contact information for your public water system on your water bill.
There is not a federal drinking water standard for strontium at this time. The EPA has set a health reference level for strontium. As of October 2014 the health reference level for strontium was listed as 1.5 milligrams per liter (mg/L).
It is possible that EPA will decide to regulate strontium in the future. EPA will examine both potential health risks and the UCMR3 occurrence data when determining if strontium should be regulated. EPA’s decision to regulate is based in large part on whether the UCMR3 testing shows a significant number of U.S. drinking water systems have concentrations of strontium at levels EPA finds to be a concern.
If you get your drinking water from a private well, you should have your water tested for strontium in its various forms by a certified laboratory every few years. You can find information on how to sample for strontium and where to send samples for analysis by contacting your state water laboratory certification officer. Contact information for your state can be found on EPA's drinking water lab certification page. Additional information about well water testing from EPA is available on their private drinking water well FAQ page.
Cation Exchange Softeners have been shown to be effective at removing other alkaline earth metals from water supplies where they have been used and tested; however there is not a device currently that has been certified to specifically remove strontium.
Bottled water quality can vary. Bottled water in the United States is regulated by the U.S. Food and Drug Administration and is required to meet standards equal to the EPA’s tap water standards. There are also individual state standards. However, in most cases, you must contact the bottled water manufacturer for information about strontium levels.