WSJ Weighs in on Perchlorate Issue

The December 29, 2005 issue of the Wall Street Journal featured the last of a series of front page articles on the theme of Toxic Traces: New Questions About Old Chemicals, and specifically revisited the issue of what level of perchlorate exposure poses risk to human health. Central to this issue is  "the burgeoning science of low-dose chemical exposure" and the uncertainty that governs what is known about perchlorate effects in the parts per billion realm -- essentially leading to a standoff between elements of the DOD and the EPA. The critical overview reflects the interests and concerns of various parties, including those who feel that public and private dollars would be better spent on more clear-cut health issues that are not burdened by  "what-if" scenarios driven by "precautionary principle" reasoning. Taken to its limit, the precautionary principle would dictate that if the evidence about a product or technology is in any way incomplete, it should be prohibited or at least stringently regulated. Unfortunately, the WSJ article did not represent or sufficiently develop several arguments that mitigate against the severe and costly regulation of perchlorate  (www.wsj.com)

The factors listed below play into the decision by the National Research Council in 2005 to recommend a maximum safe exposure level equivalent to about 24 ppb perchlorate. Toxicologists are on record as supporting a limit of 200 ppb. Elements within the EPA want a one ppb limit.  The state of Massachusetts recently declined to establish, at this time, a perchlorate-specific water quality standard that would have demanded compliance to a one ppb limit, several times more stringent than that adopted by the California EPA. Pertinent factors within the debate include (but are not limited to) the following:

• Perchlorate has been accepted for 50 years for the treatment of thyroid conditions, usually involving exposures 1000 times commonly found environmental levels.
• Occupational studies have found no anomalies in workers exposed to perchlorate at levels well above environmental exposure.
• Extrapolation of rat studies to the human condition is a problematic exercise at best.
• The rat data represent a precursor effect far removed from an actual adverse effect.
• Perchlorate is eliminated from the human body in a very efficient manner.
• The effects of nitrate ion on thyroid function, while less acute than perchlorate effects, can be represented as a greater problem because of the prevalance of nitrate exposure in humans.

Because of various uncertainty factors, it is very difficult to separate the science from the politics of the perchlorate debate. One wonders how that debate would develop if perchlorate were essential to the manufacture of chocolate rather than munitions and propellants.