On Oct. 20, 2014, EPA made a preliminary determination to regulate strontium in drinking water. 79 Federal Register 62716. Every five years, under the Safe Drinking Water Act (SDWA), EPA is required to evaluate and make a regulatory determination on at least five unregulated contaminants.

The contaminants are chosen from the Contaminant Candidate List (CCL) which is a list required to be developed by EPA under the SDWA every five years. The third CCL was published in October 2009.

From the third CCL, EPA made determinations on five of the 116 contaminants. Of the five contaminants, 1,3-dinitrobenzene, dimethoate, terbufos, terbufos sulfone and strontium, EPA made a preliminary determination only to regulate strontium.

The EPA applies three criteria when evaluating the CCL: (1) the potential adverse effects of the contaminant on the health of humans; (2) the extent of contaminant occurrence (or potential occurrence) in public drinking water; and (3) whether regulation of the contaminant presents a meaningful opportunity for reducing health risks for persons served by public water systems.

In its Oct. 20 notice, EPA explained that, at elevated levels, strontium causes a substitution of calcium in the bones affecting skeletal development. Although strontium affects all stages of life, those whose bones are in the developmental stages are most at risk, including infants, children and adolescents. The studies cited in the preliminary determination indicated that strontium has been detected in 99 percent of public water systems and at levels of concern in 7 percent of public water systems in the country.

Strontium is a naturally occurring substance. The primary historic use for strontium was in faceplate glass of cathode-ray tube televisions. According to EPA, as recently as 2008, uses included fireworks and steel production.

EPA requested comment on these preliminary determinations. The comment period closed Dec. 19, 2014. EPA will evaluate the comments and will issue a final regulatory determination in 2015. If a final determination is made that a contaminant will be regulated, EPA will begin the process to propose a National Primary Drinking Water Regulation (NPDWR) within 24 months. A finalized NPDWR will be finalized within 18 months following the proposal.