Last month the US Centers for Disease Control and Prevention (CDC) reported they had found 15 brands of powdered infant formula were contaminated with perchlorate, a component of rocket fuel that has been found in drinking water in 28 states and territories, and thought mostly to be a legacy of the Cold War because of rocket and missile trials.
The findings were published in the March issue of the Journal of Exposure Science and Environmental Epidemiology but did not come to public attention until the Washington DC-based advocacy organization Environmental Working Group (EWG) alerted the press late last week.
First author of the CDC study was Dr Joshua G Shier of the Division of Environmental Hazards and Health Effects, National Center for Environmental Health, Centers for Disease Control and Prevention, in Atlanta, Georgia.
Shier and colleagues did not identify the 15 brands they tested, but said that 2 of them accounted for 87 per cent of the US powdered infant formula market in 2000.
They found that all the powdered infant formulas they tested were contaminated with perchlorate, and that the cow’s milk based formulas with lactose “had a significantly higher perchlorate concentration perchlorate than soy, lactose-free, and elemental PIFs [powdered infant formulas]”.
However, the conclusion that probably captured the most attention was:
“The perchlorate RfD may be exceeded when certain bovine [cow’s] milk-based PIFs are ingested and/or when PIFs are reconstituted with perchlorate-contaminated water.”
RfD is the Environmental Protection Agency “safety limit” for perchlorate (the reference dose, or RfD) which is currently 0.7 micrograms of perchlorate per kilogram of body weight per day. The EWG says many experts think this should be lower.
Thus the two sources of contamination (powdered formula and tap water) coming together is what appears to put the prepared baby milk above the EPA safety limit.
In a more recent article in the same journal, EPA researcher Matthew Lorber describes the use of a “simple pharmacokinetic model to characterize exposure to perchlorate” and says that the literature on perchlorate suggests it is the consumption of foods rather than drinking water that dominates day to day exposure to the chemical.
He concludes:
“Daily variation in urine concentration was studied with the model, and it was found that concentrations in the morning hours were lower than concentrations in the afternoon and evening hours, corresponding to the time when most exposure was assumed to occur.”
Perchlorate is (ClO4-) is a component of ammonium perchlorate (NH4ClO4), an oxidant used in missile and rocket propellants. According to studies by the EPA it has been found in drinking water, (particularly near defence and aerospace sites, according to a recent news report from the Associated Press), and recent surveys by the US Food and Drug Administration (FDA) and others have also suggested it is in the food supply. The compound also occurs naturally.
Lorber writes that the main public health concern is that perchlorate interferes with iodine uptake and reduces thyroid function. A study by the National Academy of Sciences in 2005 found that the fetuses of pregnant women with hypothyroidism or iodide deficiency are likely to be the most at risk of the effects of perchlorate exposure.
According to the EWG, perchlorate is a thyroid toxin that may interfere with early brain development in unborn and young babies. The chemical is a component of rocket fuel and although it also occurs naturally, most of it got into the drinking water because of the missile tests conducted during the Cold War, said the EWG in a press statement.
Last year, the EPA declared that perchlorate was not a threat to most Americans and there was no need to regulate it as a drinking water pollutant, reported the EWG, who said the decision was “widely regarded as a major victory for the Pentagon and defense and aerospace contractors reluctant to pay clean-up costs that could mount into the hundreds of millions of dollars”.
The EWG said that the CDC study:
“Represents perhaps the strongest evidence to date supporting the need for a legally enforceable safe drinking water level that protects pregnant women, infants and others who are most vulnerable to the effects of this harmful chemical.”
“The new Obama administration leadership at EPA can and should take steps to reduce infants’ exposures to perchlorate pollution in tap water,” they added.
“Perchlorate exposure from infant formula and comparisons with the perchlorate reference dose.”
Joshua G Schier, Amy F Wolkin, Lisa Valentin-Blasini, Martin G Belson, Stephanie M Kieszak, Carol S Rubin, Benjamin C Blount.
doi: 10.1038/jes.2009.18
Sources: Journal of Exposure Science and Environmental Epidemiology, EWG Press Release, AP.
Written by: Catharine Paddock, PhD