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Science & the Public

Perchlorate: A Saga Continues

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Perchlorate is not yet a household word in many parts of the country. But it may becomes one if Sen. Barbara Boxer has her way.

Perchlorate – an ingredient in solid rocket fuel, fireworks, flares and explosives – taints drinking-water supplies around the nation, not to mention plenty of foods. In animal tests, the pollutant perturbs thyroid-hormone signaling. If such hormonal messages are muted or garbled in the womb or shortly after birth, an animal may suffer developmental – even cognitive – retardation. So one might think that U.S. regulatory agencies would have set maximum allowable limits for perchlorate in drinking water and foods.

They haven’t.

Why they haven’t remains a mystery to some of the greater minds in toxicology – and to some of our more outspoken elected leaders. Yesterday, one of those lawmakers, Boxer (D-Calif.), grilled the Environmental Protection Agency’s top water official about why perchlorate limits for water still don’t exist.

And, it turns out, she didn’t like Benjamin H. Grumbles’ answers. Not one little bit.

Boxer chairs the Senate Committee on Environment and Public Works. In her opening statement she noted that of some nearly 400 sites around the country tainted with perchlorate, 106 are in her state.

Although EPA had at one point required water utilities to monitor perchlorate, it revoked the rule 17 months ago. Five months afterward, Boxer notes, EPA argued it lacked sufficient data to know whether regulations are warranted.

“Talk about speaking out of both sides of your mouth,” she said at the hearing. “This is a perfect case.”

Speaking on behalf of EPA, Grumbles said the agency had been studying the science of perchlorate’s potential toxicity for more than a decade. Based on that, it had issued a preliminary remediation goal – or PRG – for perchlorate. It recommended that tainted waters be cleaned up to where they no longer contained more than 24.5 parts per billion of the pollutant. It wasn’t, however, a legally binding rule.

Some states, fed up with waiting for the feds to set legal limits, issued their own. Massachusetts, for instance, implemented a 2 ppb limit for perchlorate in drinking water. Last October, California set a limit of 6 ppb. So if the states can make a determination that limits are warranted and at values well below EPA’s remediation goal, why can’t Grumbles’ agency do the same? That’s what Boxer wanted to know.

“We know that perchlorate can have an adverse effect – and we’re concerned about that,” Grumbles said. Moreover, he reported, data collected before EPA let the utility-monitoring program end, showed that 2 percent of some 34,000 surveyed drinking-water systems are tainted with perchlorate concentrations above 4 ppb. Where the pollution showed up, its concentrations averaged about 10 ppb, he said.

The Centers for Disease Control and Prevention has reported finding perchlorate residues in urine from a broad and representative cross-section of the U.S. population. So why won’t EPA accept that people are getting contaminated and that water is a source?, Boxer asked.

The problem, Grumbles responded, was that food can also be a major source. Indeed, he noted, Food and Drug Administration scientists have found traces of perchlorate lacing 74 percent of the 285 foods that they surveyed. Those data appear in a January 2008 paper (still in press at the Journal of Exposure Science and Environmental Epidemiology). The sampled foods had been chosen to reflect the U.S. diet.

Grumbles argued that EPA didn’t want to set water limits for perchlorate until it could figure out if water, rather than foods, contributed substantially to how much of the toxic chemical gets into people.

For what it’s worth, the Environmental Working Group is an activist group that identifies and works to reduce what it believes to be unnecessary public exposures to harmful substances, especially in food. EWG’s scientists, who reviewed the new FDA paper, concluded that the survey’s “findings are especially concerning because they show that children have high baseline exposures to perchlorate from commonly consumed foods and beverages. Additional exposures from other sources like contaminated tap water could easily result in cumulative daily exposures that exceed the EPA reference dose” – a guideline for presumably safe intake.

Grumbles vowed that EPA takes children's perchlorate exposures seriously and would decide by year end whether to set legally binding limits for perchlorate in water. He added in a conciliatory tone to Boxer, “I understand your frustration at how long the [deliberative] process is taking.”

Boxer wasn’t mollified. Instead, she asked the EPA official: “Is it possible that EPA could decide not to regulate perchlorate? Is that an option?”

“That is a distinct possibility,” he conceded.

To which Boxer pointed out, acknowledging more than a little “anger,” that EPA’s own Children’s Health Advisory Committee had told Grumbles’ boss two years ago that “the new PRG is not supported by the underlying science and can result in exposures that pose neurodevelopmental risks in early life.”

In fact, she argued, that panel “told you that what you were doing was dangerous.” How, she asked, can you now expect us to believe you don’t know if possible exposures are risky enough to warrant limiting them via regulations?

The committee chairman’s performance and impassioned rhetoric made for good drama. But Grumbles remained unruffled, despite Boxer’s admitted “hostile questioning.”

Anticipating this result, the California senator announced she was introducing a bill – the Perchlorate Monitoring and Right to Know Act – that would require that EPA reinstate not only mandatory monitoring for the pollutant in municipal water supplies but also a public reporting of those findings.

Of course, bills are a dime a dozen. Many are worth considerably less than that. Few ever pass into law, and when they do, they often bear only the slightest resemblance to what was initially proposed.

But bills do offer a measure of how seriously legislators consider particular issues. And perchlorate concerns have been building, not going away, as the development of new state regulations attest.

But for now, we must sit back and wait to see if EPA chooses to act on perchlorate or just contents itself with letting the states step in to create their own hodgepodge of potentially conflicting standards for the pollutant.

Citations

Murray, C.W. 2008. US Food and Drug Administration's Total Diet Study: Dietary Intake of Perchlorate and Iodine. Journal of Exposure Science and Environmental Epidemiology (in press). DOI: 10.1038/sj.jes.7500648

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