SACRAMENTO, CA, Sept. 25, 2008 -- The U.S. Environmental Protection Agency (U.S. EPA) has yet to formally release its preliminary decision on setting a national standard for perchlorate in drinking water, but recent news coverage on EPA's draft document has made the agency's intentions well known. What has not been included in the recent coverage is that this preliminary decision on perchlorate is based on a review of the best available science, which spans more than five decades, as well as EPA's own guidelines. As such, the public should understand this draft determination represents a well-considered, scientifically-based and reasonable approach which takes into account perchlorate regulations that other states have already implemented.
Importantly, this is a preliminary determination only. Over the next several weeks, EPA will be taking public comment on this decision and has indicated it will make a final determination by the end of this year. We look forward to this ongoing public process to ensure the best available science is used to protect public health and scarce public resources.
Background
-- In 2005, a special panel of the National Academy of Sciences (NAS) took the unusual step of suggesting a reference dose (RfD) for perchlorate. An RfD is essentially the daily amount of exposure to a compound that can be considered safe for a lifetime. Standard EPA practice is to determine what level of exposure causes an adverse effect and then apply safety factors to that number to calculate the RfD.
-- As a precaution, NAS took the unprecedented step of starting with a non-adverse effect, iodide uptake inhibition (IUI), wherein perchlorate basically blocks iodide from the thyroid gland. In an abundance of caution, NAS applied a safety factor of ten to this non-adverse effect level to suggest a perchlorate RfD of 24.5 parts per billion (ppb). NAS considered this level of exposure to be safe for everyone, including the most sensitive populations.
-- It's important to understand that exposure to levels above 24.5 ppb, if it occurs, does not suggest a health risk. In fact, it only means that the individual is closer to the level at which perchlorate may begin blocking iodide from the thyroid gland (approximately 245 ppb). The NAS panel concluded that the evidence does not suggest that levels below 245 ppb cause IUI-and, to repeat for clarity, the NAS emphasized that IUI is not an adverse effect.
>> View the complete NAS report
While EPA's complete rationale for this decision should soon be a matter of public record, an objective review of the best available science suggests environmental levels of perchlorate do not pose a risk of adverse health effects, nor is perchlorate found at high enough levels to pose a public health concern (based on the NAS RfD).
>> More information on perchlorate
The Perchlorate Information Bureau is supported by Aerojet, American Pacific Corporation Lockheed Martin and Tronox. These companies have worked cooperatively with the U.S. Environmental Protection Agency to increase scientific and medical understanding of perchlorate's risk to human health.
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