Under the Safe Drinking Water Act (SDWA), the EPA regulates more than 90 contaminants in drinking water. In addition, according to the amendments to SDWA in 1996, the EPA is required to:
Generate the contaminant candidate list (CCL) for unregulated drinking water contaminants every five years. CCL1, CCL2, and CCL3 were developed in 1998, 2005, and 2009, respectively. A new CCL4 has just been released this year.
Collect data on health effects and occurrence on selected contaminants through unregulated contaminant monitoring rule or regulation (UCMR).
Review and evaluate collected data every five years and decide whether to regulate at least five contaminants on the CCL.
Every five years or so, a maximum of 5 contaminants will be added to the new regulation list. Recently, EPA has evaluated the 30 contaminants on the EPA UCMR 3 list, from the 116 contaminants listed on CCL3.
Strontium (with an atomic number of 38) is a member of alkaline earth metals. It has 4 stable isotopes and 16 radioactive isotopes. Since radioactive strontium is under regulation as a radionuclide, I will only talk about stable strontium.
Among the four stable isotopes (84Sr, 86Sr, 87Sr, and 88Sr), 88Sr is the most common one, accounting for 83% of the total. In nature, stable forms of strontium are found mainly in the form of celestite (SrSO4) and strontianite (SrCO3). Since the US has stopped strontium mineral mining, strontium has been imported for making the products of pyrotechnic and signals (fireworks and flares), ferrite ceramic magnets, master alloys, pigments and fillers, electrolytic production of zinc, fluorescent light, tooth paste, and medicine.
Humans can accumulate strontium via a number of exposure pathways: inhalation from the air, ingestion from water and food, and absorption through the skin.
Preliminary Determination of a Regulatory Decision for Strontium
Three criteria are used by the EPA to preliminarily select strontium to be regulated:
Strontium has adverse health effects: Similar to calcium, strontium is easily taken from water and food, and is mainly (99%) deposited in bones. Excessive absorption of strontium negatively affects skeletal development and leads to thickened bones, which are prone to fracture. Infants, children, and adolescents are sensitive population for strontium.
Strontium occurs at levels and frequencies of public health concern: According to the data from National Inorganics and Radionuclides Survey (NIRS), 99% of randomly selected public water systems tested from 1984 to 1986 had detectable strontium, ranging from 1.53 to 43,550 ug/L. More than 7% detected strontium at the level of health concern (1,500 ug/L).
Strontium regulation provides a meaningful opportunity for the reduction of a future health risk: Strontium at the level of concern affects 26 states and more than 10 million people in the U.S. In addition, water is the major pathway for strontium intake. Finally, the sensitive population, such as children and adolescents, is a major concern. Since strontium is excreted primarily in the urine, strontium also adds a health burden to patients with kidney disease.
Analysis of strontium
Environmental strontium samples can be analyzed by multiple techniques, such as spectrophotometry, fluorescence spectrometry, inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS). However, the EPA UCMR3 approves the use of ICP-MS as outlined in Method 200.8 Rev. 5.4 for strontium analysis at a minimal reporting level (MRL) of 0.3g/L. Other methods that are also approved for use for strontium analysis include SM3125 and ASTM 5763-10.
You may want to know precise strontium analyses for different applications, such as:
If you have questions on strontium analysis, do enter them in the Comments box below. I look forward to hearing from you.
Wei Liu is a senior market development manager with a focus on trace elemental analysis applications in environmental and industrial markets in the Chromatography and Mass Spectrometry Division at Thermo Fisher Scientific Inc. As a former scientist who worked in the field of industrial enzymes and drug discovery, and following his MBA from the Haas School of Business, UC Berkeley, Wei has worked in a wide range of roles including marketing consultant, product manager, and market research manager. Wei completed his Ph.D. in Molecular Microbiology at the University of Illinois at Chicago, and post-doctoral training at Stanford University; he has 13 international scientific publications and 4 patents to his credit.