Tuesday, January 11, 2005

Update: Arizonans are in no danger from drinking water- or are they?

Original post:
How can we be sure when Arizona allows the highest levels of perchlorate cited in this article? We allow 14 ppb compared to New Mexico (where two national labs and a missile range are located) which only allows for 1 ppb. Keep in mind that there is continuing debate on what a safe level is. The EPA has yet to set standards for Perchlorate, but the current working level from their 2002 draft is 1 ppb. Studies that are more recent suggest that that may be too high, but the EPA is not expected to make a final recommendation until 2006. Shouldn't we err on the side of caution? Environmental groups think so, EWG is calling for a standard of 0.1 ppb and they make a convincing case based on an FDA study.
Are Arizonans are in no danger from drinking water? The National Acadamy of Sciences has basically said- No!
WASHINGTON (Reuters) - Some levels of rocket fuel pollution are safe, but not as much as industry had argued, a National Academy of Sciences (news - web sites) committee said on Monday. At least two environmental groups accused the government of trying to influence the report's findings, but disagreed on whether the attempts had succeeded. The pollutant from rocket fuel, a chemical called perchlorate, can affect thyroid function. There are no federal limits on how much is safe but independent groups have said the chemical could, in theory, affect developing babies.
They put the new threshold at 2.5 PPB*, this is much lower than Arizona's 14 ppb and much closer to the New Mexico standard of 1 ppb. Keep in mind this is only one step on the way to setting a standard. In a more detailed article EWG says:
(1) The EPA will have to take into consideration additional exposure to this chemical through milk and other foods, where it has been found in nationwide tests. California officials have estimated that only 60 percent of perchlorate exposure is coming from drinking water, with the rest coming from food. (2) The EPA will also have to take into consideration the fact that children consume about 6 times more water, relative to body weight, as adults. Infants and children are known to be more susceptible to the effects of perchlorate and the EPA will have to base their drinking water standard on a child or infant body weight rather than that of an adult male. Correcting for these differences, EWG calculates that the findings in the NAS report support a national drinking water standard of no higher than 2.5 ppb. Our calculations are as follows: [NAS reference dose: 0.0007 mg/kg-day] x [infant body weight to drinking water consumption ratio: 5.99 kg-day/L] x [proportion of perchlorate exposure coming through food: 0.6] x [factor to covert mg/L into parts per billion: 1000] = [drinking water standard: 2.5 ppb] The EPA and Massachusetts had earlier recommended a level of 1 ppb, while California has recommended 6 ppb.
Back to the origional article...
Its report says people could drink up to up to 0.0007 milligrams per kilogram of body weight without harm - about 20 times more than the 'reference dose' proposed by the U.S. Environmental Protection Agency (news - web sites). The National Academy of Sciences report said perchlorate had been discovered in 35 states since 1997 and more than 11 million people have "perchlorate in their drinking water at concentrations of 4 parts per billion or higher." It also said that although there is clear evidence the chemical can dampen thyroid function, leading to a serious condition called hypothyroidism, there was not enough evidence to show it could lead to thyroid cancer, as the EPA has suggested. The committee said the EPA would have to seek more data on the effects of perchlorate on children before setting any standards.
(* updated from 2 to 2.5 PPB)

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