OAKLAND, CA - A startling new study by the federal Centers for Disease Control (CDC) says minute traces of a toxic rocket fuel chemical found in milk, fruit vegetables and drinking water supplies nationwide lowers essential thyroid hormones in women. An Environmental Working Group (EWG) analysis finds that 44 million American women who are pregnant, thyroid deficient or have low iodine levels are at heightened risk from exposure to the chemical.
Regulators have known for years that perchlorate, the explosive component of solid rocket fuel, can lower levels of the thyroid hormones essential to proper development of fetuses and infants and good health in adults. But new scientific evidence clearly shows that perchlorate is a much greater public health threat than previously realized. Tests of almost 3,000 human urine and breast milk samples - along with tests of more than 1,000 fruit, vegetable, cow's milk, beer, and wine samples - reveal that perchlorate exposure in the population is pervasive.
The CDC's new study, released today, found that perchlorate exposure is affecting thyroid hormone levels in American women, particularly those with lower iodide intake. CDC researchers analyzed urine samples from more than 1,100 women for perchlorate, and then looked to see if perchlorate exposure could predict thyroid hormone levels. They found a statistically significant relationship between perchlorate levels as low as 3 parts per billion - about one teaspoon of water in an Olympic-sized swimming pool - and one type of thyroid hormone for all women, and an even more marked relationship between perchlorate levels and two types of thyroid hormones in women with lower iodine intake. Thirty-six percent of U.S. women have iodine intake that falls into this category.
"The Pentagon and defense contractors, who are responsible for much of the perchlorate in drinking water supplies, have lobbied hard against federal standards, arguing that perchlorate posed no threat to healthy adults," said Renee Sharp, an EWG analyst who has studied the chemical since 2000. "This new study shows that even very small levels of perchlorate in water or food can have a marked effect on thyroid levels in women. We can't ignore this serious public health issue any longer."
The median level of perchlorate in urine in CDC's study was just 2.9 micrograms per liter (a microgram per liter is equal to 1 ppb). Since average urine output is about 1.5 liters per day, this means that women in the study were ingesting somewhere around 5 micrograms of perchlorate per day. Even at this low level, researchers found effects on thyroid hormone levels. But the federal "safe dose" level corresponds to almost ten times this dose. This clearly indicates that the current EPA reference dose and cleanup guidance is several orders of magnitude too high.
EWG urges the federal government to act promptly to set a drinking water standard of no more than 0.1 parts per billion of perchlorate - almost 250 times more stringent than the current federal recommendation for cleanup of contaminated water, and 20 to 60 times stricter than drinking water standards set by Massachusetts and pending in California and New Jersey, the only states to take action so far. With new evidence showing widespread food contamination and effects on the thyroid at typical exposure levels, perchlorate exposure through drinking water cannot be tolerated. EWG also urges the Food and Drug Administration (FDA) to consider making the iodization of salt mandatory, because insufficient iodide in your diet can compound perchlorate's health effects, and iodide deficiency has increased sharply since the 1970s.
The vast majority of perchlorate manufactured in the United States is used by the Department of Defense to make solid rocket and missile fuel, while smaller amounts of perchlorate are also used to make firework and road flares. Perchlorate is also a contaminant of certain types of fertilizer that were widely used in the early part of the 20th century but are in limited use today.
In July, Massachusetts set the nation's first drinking water standard for perchlorate of 2 parts per billion, while California and New Jersey are currently considering standards of 6 ppb and 5 ppb, respectively. The EPA has yet to set a federal drinking water standard, but has issued a controversial cleanup "guidance" level of 24.5 ppb. In March, a federal advisory committee on children's health sharply criticized the agency, writing in a letter to EPA Administrator Stephen Johnson that the guidance was "not supported by the underlying science and can result in exposures that pose neurodevelopmental risks in early life."
In 2003, EWG and the Riverside Press Enterprise independently tested store-bought winter lettuce for perchlorate and found the contaminant in more than half of the samples tested - in some cases at high levels. A year later EWG tested California milk for perchlorate, finding the chemical in 31 out of 32 samples. Around the same time, the California Department of Food and Agriculture secretly conducted their own milk tests and found perchlorate in all 32 samples collected. These studies were some of the first indications that food might be an important route for perchlorate exposure in addition to contaminated drinking water.
More than 1,000 tests by government and independent scientists later, there can be no debate: The US population is being widely exposed to perchlorate, both in water and in the food supply. Perchlorate is polluting water supplies for millions of Americans. According to tests conducted under the EPA's Unregulated Contaminant Monitoring Rule, 160 public water systems in 22 states are contaminated with perchlorate.
Perchlorate has also been found in a wide variety of domestic and imported produce, with some of the highest levels being found in oranges, grapes, raspberries, apricots, melons, lettuce, tomatoes, basil, kale, spinach and asparagus. The chemical has also been found in 98 percent of 222 milk samples collected from 22 US states, and in hundreds of samples of beer and wine. Fruits and vegetables had the highest concentrations. Overall, 69 percent of the 1,090 food and beverage samples tested had detectable perchlorate.
Tests by the CDC and independent researchers confirmed that many Americans are carrying levels of perchlorate in their bodies well above the levels found to lower thyroid levels. CDC sampled the urine of almost 3,000 Americans - a valid statistical sample of the entire population - and found perchlorate in everyone at an average of 5.5 parts per billion. An academic study of breast milk from 36 women in 18 states also found perchlorate in everyone tested, with an average level of 10.4 ppb.