Questions and Answers

Perchlorate and Health: Part 2


Q: Has perchlorate been shown to cause cancer in humans?

Numerous, credible studies have shown no evidence that perchlorate causes cancer in humans.

A: No. The National Academy of Sciences has confirmed it's unlikely perchlorate causes cancer, and numerous other credible studies have shown NO evidence that perchlorate causes cancer in humans, even when consumed at levels far higher than any found in drinking water. The state of California has also stated that perchlorate does not pose a known cancer risk to the public.


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Q: Are newborns and children more sensitive than adults to perchlorate?

A: The best scientific and medical research shows that newborns and children are not affected by perchlorate at the low levels found in drinking water. Most recently, a 2004 study by Tellez et al. 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. Another study (by Kelsh et al.) 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. Other studies show there are no measurable effects on human beings at doses up to 245 ppb.


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Q: Are there other studies that explore how perchlorate might affect newborns?

A: One study (Li et al.) looked at the thyroid function of newborns in Las Vegas, Nevada, where low levels of perchlorate exist in the water, and in Reno, Nevada, where there is no perchlorate in the water. In comparing the results of standard tests of newborns in the two areas, scientists found no difference between the newborns in terms of thyroid function. A separate study (Lamm and Doemland) comparing counties in California and Nevada, some with trace amounts of perchlorate in the water and some without, had similar results.


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Q: Should pregnant women or mothers of infants take any special precautions? Where can they find further information?

A: As with all questions of health relating to pregnancy, prospective mothers can obtain the best possible information for informed decision making by speaking directly with their doctor. Information may also be obtained from the American Thyroid Association.


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Q: Much of the research available on perchlorate appears to have been funded by industry. Is this information credible?

A: This is an important issue that must be well understood. On the one hand, some people believe that industry - rather than taxpayers - should fund this kind of research. At the same time, it's important that safeguards be in place to guarantee the validity and credibility of the research findings. With respect to the perchlorate research referred to here, several of these safeguards are in place:

  1. The scientific research has been conducted entirely independent of the funding organizations.
  2. The research findings have been peer-reviewed by independent, neutral and respected scientists to verify the research was done correctly and the results are valid.
  3. These studies have also been published in internationally respected scientific journals.

This critical review ensures the studies conducted can be replicated by other scientists, now and in the future. Taken together, all these factors can give the public confidence in the accuracy, validity and credibility of the research.


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Q: Are there other substances that we consume that have the same effects as perchlorate?

A: A variety of substances found in everyday foods and drinking water can affect the body in essentially the same way as perchlorate. Specifically, nitrates and thiocyanates, which occur naturally in several kinds of vegetables that are considered essential to a healthy diet, have the same thyroid effect as perchlorate.


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Q: How can perchlorate be removed from water?

A: There are currently two major technologies in use for treating large volumes of a resin to absorb perchlorate and remove it from water, affording the opportunity for safe and appropriate disposal of the perchlorate. Biological treatment is a process that uses microorganisms to break down perchlorate into other components. In this process, water can be treated in a tank or in the ground. The primary resulting component is chloride, which is part of common table salt. Other technologies are currently under development.


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