The EPA has made a preliminary determination to regulate strontium in the nation’s drinking water and will evaluate public feedback following a 60-day public comment period in order to determine whether to issue a final determination to regulate strontium.
If this determination will be made, the EPA will begin the process of developing a proposed rule, with hopes of publishing the final regulatory determinations in 2015, as mentioned in the October 20th, 2014 news release.
The press release also mentions 4 other contaminants (dimethoate, 1,3 dinitrobenzene, terbufos, and terbufos sulfone), which do not require regulation at this time, as they are either not found or are found at low levels of occurrence in public water systems.
What Is Strontium and How Does It Affect Our Health?
Strontium is a natural and commonly occurring element, usually found in nature in the form of minerals. Pure strontium is a hard, white-colored metal, but cannot be found in this form in the environment. There are 2 types of strontium compounds: those that dissolve in water and those that do not. Strontium can also exist as radioactive isotopes, with strontium-90 being the most hazardous of the radioactive isotopes of this chemical element. It forms in nuclear reactors or during the explosion of nuclear weapons.
Strontium-90 is used in medical and agricultural studies, thermoelectric devices, navigational beacons, remote weather stations and space vehicles, electron tubes, radioluminescent markers and for treatment of eye diseases. Appearing adjacent to calcium on the Periodic Table of Elements, strontium is not toxic. However, it has the ability to displace calcium in the bones of humans and animals, which can result in poor bone quality and/or bone development issues in infants.
Because strontium is so prevalent in the earth’s crust it appears in an estimated 99% of municipal water supplies and further estimated that 10% of all sources will have levels deemed excessive.
Strontium-90 behaves like calcium in the human body and tends to deposit in bone and bloodforming tissue (bone marrow). Thus, strontium-90 is referred to as a “bone seeker,” and exposure will increase the risk for several diseases including bone cancer, cancer of the soft tissue near the bone, and leukemia. Risks from exposure depend on the concentration of strontium-90 in air, water, and soil. At higher exposures, such as those associated with the Chernobyl accident, the cancer risks may be elevated. The magnitude of this health risk would depend on exposure conditions, such as the amount ingested.
Has the EPA Made Any Recommendations to Protect Human Health?
The EPA has established a Maximum Contaminant Level (MCL) of 4 millirems per year for beta particle and photon radioactivity from man-made radionuclides in drinking water. The average concentration for strontium-90 that is assumed to yield 4 millirems per year is 8 picoCuries per liter (pCi/L). Also, if other radionuclides that emit beta particles and photon radioactivity are present in addition to strontium-90, the sum of the annual dose from all the radionuclides cannot exceed 4 millirems/year.
Removing Radioactive or Natural Strontium from Water
Conventional treatment was not effective at removing strontium from the water but the following processes were found to be highly effective for the removal of radioactive or natural strontium:
- adsorptive media: up to 99% removal
- reverse osmosis: >99% removal
- ion exchange: greater than 99% removal
A number of adsorptive media were effective for studies with strontium-90, with a synthetic zeolite being most effective at 75-80% removal and bethonite clay at higher pH (7.4 to 8), removing 85-90% of the strontium-90 from water. Hydrated manganese oxide at higher pH (8 to 10) was most effective at removing natural strontium, with 90-92% removal.
Removal of strontium-90 by 2 cation exchange media was found to be highly effective, greater than 99% removal in one case, based on one study involving bench-scale isotherm tests using a ground water. Also, removal improved with contact time. Ion exchange has proven to be the Best Available Technology for control of beta particle emitters like strontium-90.
Natural strontium was effectively removed with membrane separation (97 to greater than 99%) and reverse osmosis is the Best Available Technology for the control of beta particle emitters like radioactive strontium. Call us at 760.734.5787 and get in touch with one of our water experts today to learn more about strontium and how to remove it from your water!