BEST AVAILABLE SCIENCE FINDS LOW LEVELS OF PERCHLORATE IN WATER HAVE NO MEASURABLE HEALTH EFFECT
Perchlorate as a medicine
PERCHLORATE DOES NOT CAUSE CANCER, HARM THE IMMUNE SYSTEM OR ACCUMULATE IN THE BODY.
Because of perchlorate's ability to suppress thyroid hormone activity if ingested at very high levels of 70,000 parts per billion (ppb) to 300,000 ppb, it has been used for more than 50 years as a medicine for people with hyperthyroidism (excessive thyroid activity) and other thyroid gland disorders. One of the major reasons it is no longer used in the U.S., however, is because it took enormously high doses to have any effect, and these doses had to be administered frequently because perchlorate is so rapidly eliminated from the body. Doses given to patients are literally tens of thousands of times higher than the amount of perchlorate being found in drinking water supplies. While it has been replaced in the U.S. with newer medications1, perchlorate continues to be prescribed in Europe and elsewhere for the treatment of certain thyroid conditions.
Perchlorate's direct effects are limited to the thyroid
Studies show that perchlorate's direct effects on human health are limited to the thyroid gland. Perchlorate is being detected at minute amounts in some drinking water supplies. Much higher levels, above 245 ppb, when consumed over a long period of time, (years, according to some research) may reduce the thyroid's ability to absorb iodide from the bloodstream. This in itself is harmless and actually occurs naturally everyday as a result of diet and other factors.
A PERSON WOULD HAVE TO DRINK AT LEAST 500 GALLONS OF WATER WITH 20 PPB OF PERCHLORATE EVERY DAY BEFORE THERE COULD BE ANY ADVERSE EFFECT.
Perchlorate exposure at very high levels (somewhere above 14,000 ppb) over a long enough period of time (years) can cause thyroid hormones to drop and over time can result in adverse health effects related to the thyroid. However, a person would have to drink at least 500 gallons of water with 20 ppb of perchlorate in each gallon every day before there could be any adverse effect. It takes such a high level of constant exposure because most Americans eat a diet with at least twice the 150-200 mg recommended daily allowance of iodide, and the thyroid gland keeps a substantial iodide reserve to make sure the body stays healthy.
A sequence of three events is required for perchlorate to have any adverse effect on health, each requiring higher doses of perchlorate. There is no measurable effect at all below 245 ppb, and according to credible medical experts and science (Lamm, et al.) it takes at least 100 times this amount to have any adverse health effect. The three events that must occur are:
- First: Perchlorate exposure must be high enough to prevent the thyroid from getting its usual amount of iodide. This may begin to happen at around 245 ppb of perchlorate in drinking water, AND.
- Second: Exposure must be high enough to overwhelm the body's normal adaptive process, thereby lowering the amount of thyroid hormones in the body (scientific research indicates this does not occur at levels below 14,000 ppb), AND.
- Third: Exposure must be high enough (above 20,000 ppb) and sustained long enough to reduce thyroid hormone levels for a long period of time. While this time period can vary based on a variety of factors, research by . and Gibbs et al. suggests it can take years of exposure at these extreme levels to cause any adverse health effects.
Although there are no measurable effects when perchlorate is in the body at low levels (below 245 ppb), any effects of perchlorate on the body's ability to produce hormones are fully reversible once exposure declines or stops. Perchlorate is not stored in any human tissues, including the thyroid gland.
LOW LEVELS OF PERCHLORATE DO NOT HARM NEWBORNS OR CHILDREN
The National Academy of Sciences (NAS) January 2005 report on the health implications of perchlorate recommended a reference dose of perchlorate at 0.0007 milligrams per kilogram per day. In February 2005, the U.S. Environmental Protection Agency established its official reference dose of perchlorate at 0.0007 milligrams per kilogram per day, and translated that number to a Drinking Water Equivalent Level of 24.5 ppb. Both the NAS and the EPA state that these numbers are appropriate and protective for all populations, including the most sensitive population - the fetuses of pregnant women who might have hypothyroidism or iodide deficiency. The NAS reviewed and analyzed research which found no measurable effect on human beings at levels below 245 ppb (Greer, et al.). These studies provide reason to believe that low levels of perchlorate (below 245 ppb) also have no effect on pregnant women or fetuses. In particular:
- Tellez et al. study. This study found no impacts from perchlorate on pregnant women during the critical period between the late first and early second trimesters, and no effect on fetal development or thyroid levels in newborns. The study examined pregnant women and babies from three cities in Chile, where perchlorate levels range from non-detect to 110 ppb, and daily intake of dietary iodide is equivalent with the U.S.
- Kelsh et al. This study evaluated whether newborns had higher rates of primary congenital hypothyroidism (PCH) or elevated concentrations of thyroid-stimulating hormone in a community where perchlorate was detected in groundwater wells. The findings, according to the Journal of Occupational and Environmental Medicine, suggest that residence in a community with potential perchlorate exposure has not impacted PCH rates or newborn thyroid function. View Abstract
- Li et al. Two scientific studies in Nevada compared the thyroid health of newborns in Las Vegas, where perchlorate is present in the water at levels below 24 ppb, and Reno, which does not have perchlorate in drinking water. There was no difference between newborns in the two cities in either their levels of thyroid hormones or their levels of thyroid stimulating hormones.
- An animal study that examined whether perchlorate causes birth defects in rats found that extremely high doses (1,050,000 ppb) caused no birth defects.
Additional research is currently under way, with results expected in the coming months.
What perchlorate is not
Research about perchlorate has determined that it:
- Does NOT cause cancer (is not a carcinogen)
- Does NOT cause an increase in the rate of change of genes (is not a mutagen)
- Does NOT harm the immune system (is not immunotoxic)
- Does NOT cause birth defects or other reproductive harm (is not a reproductive toxicant)
- Does NOT accumulate in the body
1 In the early 1960s there was a concern that perchlorate might have an association with aplastic anemia. Seven patients who were being treated with perchlorate developed the disease. There were several possible reasons why, ranging from misdiagnosis of hypothyroidism to environmental concerns (the cases were clustered in two specific areas). No evidence of a connection between perchlorate and aplastic anemia has been shown. What is known is that in the four decades since, perchlorate has continued to be used as a medication and no cases of aplastic anemia have arisen among any patients using perchlorate as a medication.