Perchlorate found in produce from around the world
After filling his shopping bags with foods from around the world, Houssain El Aribi took them back to the lab and started to look for perchlorate.
Just one serving of some fruits can contain enough perchlorate to exceed the National Academy of Sciences (NAS) safe daily dose by more than 25%, and wines and beers pack a bigger perchlorate punch than waters, according to a new study that measures perchlorate concentrations in fruits, wines, and beers from around the world. The findings are further evidence that risk models for what is turning out to be a widespread contaminant need to be revised.
Perchlorate is well known as a major component in rocket fuel, but the chemical also forms naturally. In sufficient amounts, perchlorate disrupts the thyroid by inhibiting the uptake of iodide, an essential component of thyroid hormones.
In the study, cantaloupe from Guatemala “topped” the perchlorate charts at 463.5 parts per billions (ppb). An average serving, one-quarter of a medium melon, weighs 135 grams and would supply 62.5 micrograms (µg) of perchlorate. Fruit lovers who eat half a melon would get a 125-ppb dose. For a 70-kilogram adult, the NAS-recommended safe daily dose is 49 µg of perchlorate.
Some of the other high concentrations that chemist Houssain El Aribi and colleagues report in their paper include 145.6 ppb in Chilean apricots, 62.8 ppb in Mexican red tomatoes, 22 ppb in Chilean green grapes, and 39.9 ppb in raw Mexican asparagus.
Other studies have found low levels of perchlorate in rainwater and common foods produced in the U.S., such as milk and lettuce. The chemical has also been found in prenatal vitamins and seaweed. This is the first survey of foods from many parts of the world, says Purnendu “Sandy” Dasgupta at Texas Tech University. He adds that this study shows that perchlorate can be found all over the globe.
El Aribi and his colleagues from analytical instrument companies Applied Biosystems–MDS Sciex and Dionex conducted the survey to demonstrate the power of a new analytical method, which they developed in cooperation with the U.S. EPA.
El Aribi is quick to note that the survey is just a rough snapshot and not a representative picture, but other scientists say that it covers important ground. “This is a really interesting paper; at least it may explain where all the perchlorate is coming from,” says thyroid endocrinologist Thomas Zoeller at the University of Massachusetts, Amherst. Zoeller also notes that preliminary data from the Centers for Disease Control and Prevention show that the amount of perchlorate in urine is too high to be from drinking water alone.
Overall, fresh fruits and vegetables from California and Central and South America had the highest levels, whereas produce from Canada and China had the lowest. European levels also appeared to be low. “It is interesting to note that only certain agricultural areas are associated with a strong presence of perchlorate,” the authors write.
El Aribi purchased most of the food samples from Toronto-area stores between January 2005 and February 2006, but some were sent to him by colleagues overseas, he says.
The scientists analyzed 77 wines and 144 beers. In light of the relatively high perchlorate concentrations in grapes, it is not surprising that wines contain higher concentrations of perchlorate than beers. Wines from Chile generally had the highest concentrations, which ranged from 7.2 to 38.8 ppb. But some large variations occur in wines from the same country. For example, the levels of perchlorate in a selection of 8 Canadian wines were as high as 20.76 ppb and as low as 0.055 ppb.
Levels in beers also varied widely. Although most contained less than 1 ppb perchlorate, El Aribi found concentrations as high as 21 ppb in a French beer.
A surprising facet of the study, says El Aribi, is that perchlorate can remain in food even after it is cooked. Asparagus from Mexico had 39.9 ppb raw but retained 24.4 ppb after being boiled in water. This is a surprising result, because perchlorate is very soluble in water, he notes. Some good news is that home water filters effectively remove perchlorate from water, at least when they are new.
The study’s findings should have a significant impact on regulations that specify acceptable quantities of perchlorate in drinking water, says Gary Ginsberg, a toxicologist with the Connecticut Department of Public Health. Ginsberg has already coauthored a 2005 critique of the NAS reference dose. “Even though this is a screening study, the food contribution to daily perchlorate exposure looks to be quite substantial and so needs to be factored into drinking water criteria,” he says.
In March, the Massachusetts Department of Environmental Protection released proposed standards for drinking water and waste-site cleanup of 2 ppb; these assume that 80% of perchlorate exposure comes from food and 20% from water. “This is a standard default assumption when you know that food is a significant but difficult-to-quantify source,” says Ginsberg.
EPA was also recently criticized by its Children’s Health Protection Advisory Committee for setting a cleanup standard that assumes people are only exposed to perchlorate through drinking water.
