News Coverage
Broadcast transcript on perchlorate
Published January 12, 2005
LARRY MANTLE, host:
This is AIRTALK, Larry Mantle joining you. Delighted to have you in our company as we talk about perchlorate, a contaminant that has made its way into drinking-water wells in Southern California as well as into groundwater in other states across the US. It's part of solid rocket fuel, and so during the '50s and '60s when so much was going on with aerospace and the race to develop various kinds of propulsion, you had dumping practices which led perchlorate to make its way into groundwater.
And the question has been raised--with its effect on the thyroid, what kind of harms does perchlorate cause, and what level of exposure could be said to be safe, particularly for more sensitive populations such as children or pregnant women or those who already have thyroid problems? To talk with us about Monday's release of a National Academy of Sciences report on perchlorate and levels of perchlorate is Dr. Richard Corley. He's a member of the Health Implications of Perchlorate Ingestion Committee of the NAS and its National Research Council. He's a staff scientist at the Pacific Northwest Laboratory in Richland, Washington.
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MANTLE:
Joining us now is Bill Walker, vice president of the Environmental Working Group for the West Coast. Thank you very much, Bill Walker, for joining us this morning on AIRTALK.
Mr. BILL WALKER (Environmental Working Group):
Thank you, Larry.
MANTLE:
What is your critique of the National Academy of Sciences study which shows that there is a health risk associated with perchlorate, but not as low as what the US EPA had said?
Mr. WALKER:
Well, you know, that's not actually what the report said, or at least it's only technically what the report said. It was mostly reported that way, that the NAS study gave the lie to the idea that low levels of perchlorate were dangerous for children and, of course, their mothers. And my argument is not at all with the academy's report but with the way that most of the nation's news media reported it. I will very quickly say that I'm not including either the Los Angeles Times or the Riverside Press Enterprise, who reported the study accurately.
What the academy found was a difference between what is called a reference dose and a reference dose that was previously estimated by the EPA. But in translating that reference dose into a drinking-water standard, EPA and the state of California - the state of California has already done so, and if EPA does set a drinking-water standard they will have to do so - will have to apply some factors, the key ones in this case being the lower bodyweight of children, which means that they consume relatively more water, as much as six times more water for their bodyweight as an adult does, as well as the fact that we now know that perchlorate exposure comes to us not just through drinking water, but through milk, lettuce and other foods. When that is the case, regulators will set a drinking-water standard that is lower than it would be if the chemical was only found in water to try and keep the total level down.
MANTLE:
Let me just clarify then. So you're saying that though the reference point is different than the EPA's and the reference point is higher in the NAS study, once this is applied to an actual drinking-water standard, it's it's not necessarily going to be different than it would've been looking at the EPA's research?
Mr. WALKER:
We don't believe so, not significantly. I think most important for your listeners is the fact that if you take the NAS's endpoint and apply the factors that the California health scientists have already applied in setting our proposed drinking-water standard of six parts per billion, you actually come out with a number that's even lower than six parts per billion. We did the calculations and came out with 2.5 parts per billion.
A spokesman for the state, after looking at the report, said they don't believe there's anything in it that would cause them to raise their proposed drinking-water safety level of six parts per billion. In fact, it might provide evidence for lowering it. So I really had no disagreement at all with the academy's report; I think it's a fine piece of work. Unfortunately, the simplistic way that it was reported in much of the news media is going to leave people the impression that the academy has come out with a report saying that perchlorate is not dangerous.
MANTLE:
Bill Walker, what is the reference point? Can you describe what that number means?
Mr. WALKER:
Well, a reference dose- and Dr. Corley can correct me on this, because I am not a scientist, but a reference dose is a scientific assessment of the amount of the chemical that can be consumed from all sources without causing a measurable negative effect. "From all sources" is very important, because, as I said, we now know that the state of California, for example, estimates that people are actually getting more perchlorate exposure through milk and lettuce than they are through water.
The other thing is that a reference dose is expressed as a as a function of bodyweight. It's expressed as milligrams per kilogram of bodyweight. And in translating that to a drinking-water standard of parts per billion, you don't just convert the units of measure, but you also apply these other factors, and a big one is, are you going to calculate what the safe level is for the average adult, who-
MANTLE:
Or for the riskiest population.
Mr. WALKER:
- right- who weighs about 70 kilograms, or are you gonna calculate what the safe amount is for a fetus or child, who weighs much, much less?
And, as I said, if you take those formulas as used by California, which was looking to protect children, you come up with a level that's very, very close to what California came up with and only a little bit higher than what the state of Massachusetts came up with.
MANTLE:
Bill Walker, vice president of the Environmental Working Group for the West Coast. That reference dosage, by the way, that the National Academy of Sciences report recommended was .0007 milligrams per kilogram of bodyweight, compared with the EPA's .00003 milligrams per kilogram of bodyweight.
Dr. Richard Corley joining us from the National Academy of Sciences, a member of that Health Implications of Perchlorate Ingestion Committee, which Monday released this report looking at exposure to perchlorate and the health consequences associated with it.
Dr. Corley, in looking at the difference in that reference dose between the US Environmental Protection Agency and what the NAS panel has come out with, what do you see, when it's actually applied to drinking-water standards, as the result? Do you concur with Bill Walker's analysis?
Dr. RICHARD CORLEY (National Academy of Sciences):
Well, Bill Walker is absolutely correct. This is a oral reference dose on a milligram-per-kilogram bodyweight basis that a the most sensitive individual is expected to take on a daily basis, regardless of the source, orally. It could be water, it could be food, it could be milk, etc., wherever it is found. So it is a total oral dose; that's absolutely correct.
To translate this number to a drinking-water standard requires a number of policy decisions and assumptions of drinking-water consumption rates, and . . . there are differences from state to state and agency to agency on what those assumptions can be.
. . .
So it's all based on policy decisions, and I expect these policies may vary from from location to location. We expect [health agencies] to translate an oral reference dose that is believed to be safe for the most sensitive individual into a drinking-water standard 'cause they do have to take into [consideration] all sources of exposure orally.
MANTLE:
And in California, the public health goal, which is not, apparently, enforceable at this point, is six parts per billion. Now, we should mention, just to quantify what we're talking about in the way of contamination, that Los Angeles County has 138 wells with traces of perchlorate, according to a report by the Environment California Research and Policy Center. Also, you've got Orange, Riverside, San Bernardino and San Diego counties that also have wells that are contaminated with perchlorate.
Bill Walker, you have any sense of what we're talking about to clean-up these wells so that they would meet California's standard?
Mr. WALKER:
I don't know of a number. I believe the American Association of Waterworks has set the figure in hundreds of billions nationwide. I don't know about California specifically.
Those stakes, of course, are very important, the size of the stakes are very important to this debate. Because the debate occurred in the first place largely because the Pentagon and the defense contractors, who are the sources of most perchlorate pollution, didn't want to spend those hundreds of billions to clean it up. So they were appealing to the White House for a National Academy of Sciences opinion, which they hoped would justify their point of view that perchlorate was safe at doses hundreds of times higher than what the state of California says. But as Dr. Paul Gilman, the former chief scientist of the EPA, told the Riverside Press Enterprise after the NAS study came out, clearly they did not win their case.
. . .
MANTLE:
OK. We thank you, Bill Walker from the Environmental Working Group, Dr. Richard Corley from the NAS panel that looked at the health implications of ingesting the chemical perchlorate. This is AIRTALK on 89.3 KPCC Pasadena, Southern California public radio.