EPA seeks input on safety of strontium

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David Minton/DRC
William Hirschi prepares a water sample in the lab at the city of Denton Water Treatment Plant on Thursday.

The U.S. Environmental Protection Agency is accepting public comment about its preliminary determination to regulate strontium, a naturally occurring element found in drinking water that can negatively impact bone strength.

The EPA’s commenting period opened Monday and lasts until Friday, Dec. 19.

This preliminary determination is part of the EPA’s requirement to develop a list of currently unregulated contaminates that might be in drinking water. The goal is to determine what kinds of chemicals, heavy metals and other contaminates that ought to be regulated to protect the lake water and well water that is processed into drinking water.

The Safe Drinking Water Act requires consideration of three criteria: the potential adverse effects of the contaminant on human health, the frequency and level of contaminant occurrence in public drinking water systems and whether regulation of the contaminant presents a meaningful opportunity for reducing public health risks.

In response to questions asked by the Denton Record-Chronicle, the EPA said, “Strontium did not previously meet these criteria.”

To determine if the element meets the criteria now, the agency said it used the National Inorganics and Radionuclides Survey, or NIRS, as the primary data source to evaluate strontium in drinking water.

The NIRS took one sample between 1984 and 1986 at each of the 989 systems served by groundwater, according to the EPA, and strontium was detected in 99 percent of the samples.

At the time, the EPA recommended the health-safe level of strontium to be set at 4.2 milligrams per liter of water, but the agency developed a new health assessment on drinking water in 2014.

The EPA determined that the acceptable level of strontium should be lowered to 1.5 milligrams per liter of water because of a newer health study showing an increased risk in children whose bones are still developing.

The EPA used this new health assessment to reassess the NIRS data and discovered not only that strontium is found in 99 percent of public water systems but also that 7 percent of those systems have “levels of concern.”

Out of the 93.1 million people served by 40,106 groundwater community water systems in the nation, the national extrapolation indicates that 10 million may be exposed to concentrations greater than the new health reference level, and 15.4 million may be exposed to concentrations greater than half the health reference level, according to the EPA’s report.

In Denton County, many of the towns in the region receive their drinking water from groundwater sources, but since strontium is not currently regulated, public utility labs have not been monitoring the element in drinking water.

Tim Fisher, water production division manager for the city of Denton, said he doesn’t know how the EPA’s proposed regulations would impact the water system, but his current understanding is the proposed regulation may only impact 5 percent to 10 percent of all public systems, and they would more likely be groundwater-based systems.

The city of Denton receives its drinking water from surface water, the industry term for lake water.

Fritz Schwalm, manager of the municipal laboratory in Denton, speculated that the analysis of strontium would have minimal budgetary impact, but he doesn’t foresee finding high levels of strontium in the city’s drinking water.

The EPA, however, reported that available data, while limited, demonstrates potential for high occurrence of strontium in surface water.

The U.S. Geological Society sampled 65 surface waters across the nation and identified areas of northern and western Texas and southern New Mexico and Arizona as those with the highest concentrations of strontium. Other regions only contained strontium levels of less than 1.5 milligrams per liter of water.

Dr. Zacariah Hildenbrand of Inform Environmental is a researcher at the University of Texas at Arlington and is currently conducting a larger study on groundwater contaminants in the Barnett Shale, a geological formation that includes the ground under Denton County.

In his previous study of groundwater contaminants in the Barnett Shale, his research team found 18 of 100 samples collected had strontium concentrations above the EPA’s recommended 4.2 milligrams per liter of water threshold, and 17 of those came from “active extraction areas” located within a 5 kilometer radius of a natural gas well.

What is strontium?

Strontium is an element that occurs naturally in the environment and is a member of the alkaline earth metals. The element can form a variety of compounds, those that dissolve in water and those that do not.

Naturally occurring strontium isn’t radioactive but exists in four stable isotopes, strontium 84, 86, 87 and 88, but all four behave the same chemically, which means any combination has the same chemical effect on the body.

Strontium is released into fresh water from geologic weathering associated with sedimentary rocks such as rock salt, limestone, shales and sandstones, according to “The Potential Regulatory Implications of Strontium,” a report released by the American Water Works Association.

Several radioactive strontium isotopes are also found in the environment, and they’re formed by nuclear fission of uranium or plutonium, according to the EPA’s “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water Contaminant Candidate List.”

The most commonly found radioactive isotope in the environment, strontium-90, was a legacy left behind by above-ground testing of the atomic bomb, according to the EPA’s report.

Drinking water contamination by radioactive isotopes is covered under the EPA’s existing radionuclides rule, which was revised in 2000. The rule requires that all water flowing into a public water system be tested for high levels of the radioactive isotope.

The EPA’s current preliminary determination of regulations deals primarily with the stable isotope, which represents 83 percent of total environmental strontium found in groundwater currently not monitored by the federal agency.

Historically, strontium was used for a variety of sources, including the manufacturing of color tube televisions to block X-ray emissions, refining of zinc and making of magnets as well as fluorescent lights, toothpaste and medicines.

Dr. Ronald Hoffman, the founder and medical director of the Hoffman Center in New York City, wrote on his website, Intelligent Medicine, that strontium has been safely used as a medicinal substance for more than a hundred years.

The element first appeared in the Squire’s Companion to the British Pharmacopoeia in 1884, and as late as 1955, strontium compounds were listed in the Dispensatory of the United States of America.

The human body contains approximately 320 to 400 mg of strontium in bone and connective tissue, and the element has been thought to help with the treatment of osteoporosis.

Low doses of strontium along with calcium and vitamin D have been administered to people suffering from osteoporosis with no adverse side effects, according to medical literature.

But trace elements of strontium, Hoffman wrote, have pharmacological effects on bone when present at levels higher than those required for normal cell physiology.

In its 2014 health assessment, the EPA found that strontium has adverse health effects by replacing calcium in bone and affecting skeletal development at all life stages, especially in infants, children and adolescents because their bones are still developing.

But as early as 2004, the EPA warned people that “exposure to strontium and strontium-90 may harm you” and advised that if people are exposed, there are several factors that determine whether they’ll be harmed, according to a public health statement issued by the Agency for Toxic Substances and Disease Registry.

These factors include how much (the dose), how long (the duration) and how a person comes in contact with the element.

People come in contact with low levels of strontium by breathing air, eating food or drinking water. But food and drinking water are the largest sources of exposure, according to the Agency of Toxic Substances and Disease Registry.

Upon entering the bloodstream, strontium behaves like calcium, accumulating in bone. In adults, the element attaches to the bone surface and may affect bone density in people with low-calcium diets as well as people with kidney problems since this is the primary method of getting the isotope out of the body.

But in children, strontium may affect bone growth.

At the time, the EPA recommended that people do not drink more than 4 milligrams per liter of water.

An unknown future

The EPA said the agency is collecting new data under the Unregulated Contaminant Monitoring Rule, or UCMR, for strontium and other unregulated contaminants it suspects to be present in drinking water.

The monitoring rule is designed to represent ground and surface water systems nationally and supplements the nearly 30-year-old NIRS data, which was based on a sample too small to represent public water systems across the nation.

The agency began collecting data under the UCMR in 2013 and will continue until December 2015. It plans to use this data in the final regulatory determination of strontium.

The EPA also plans to conduct more extensive field testing of treatment technologies to assess the effectiveness of strontium removal from public water systems, the agency said.

The agency expects to publish final regulatory determinations in late 2015.

If the decision is made to regulate a particular contaminate, the rule-making process to establish primary drinking water regulation will begin, which could take the agency two years before final regulation is determined.

After 18 months has passed, the agency will propose the regulation. Then a public commenting period will begin again before a final regulation takes effect.

Once the agency establishes the regulation, it will take an additional three years for primary standards to go into effect after they’re finalized, but the EPA’s administrator or a state may extend the deadline for public water systems to come in compliance for another two years.

In the meantime, if people in Denton County are worried about high levels of strontium in their water wells, they can contact a company that tests water wells, or include calcium in their balanced diet, or drink spring-fed bottled water until the EPA determines what should be done about strontium in drinking water.

CHRISTIAN McPHATE can be reached at 940-566-6878 and on Twitter at @writerontheedge.

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