The persistent perchlorate panic

The Greenies have been struggling for some time to produce evidence of harm from the ingestion of small quantities of perchlorate.  But various official enquiries have found nothing convincing.  Below however we have a new study which does indeed show a strong effect.  But it is not a study of normal people.  It is a study of people who already have serious thyroid dysfunction.  How that generalizes to normal people is thetrefore anyone's guess.  As the authors of the original journal article themselves conclude: "These results require replication in additional studies, including in the euthyroid population".  Where the "euthyroid population" is normal people

A chemical used in rocket fuel that is found in some regions' drinking water has been linked to significantly lower IQ's in the children of mothers exposed while they were pregnant, a new study has found.

Perchlorate, which is also found in fireworks, explosives and is a byproduct of using fertilizers, may cause this by disrupting the thyroid's normal hormone production.

'Our report highlights a pressing need for larger studies of perchlorate levels from the general pregnant population and those with undetected hypothyroidism,' the authors wrote.

The study, which was published in the Journal of Clinical Endocrinology & Metabolism, identified pregnant women in Cardiff, Wales and Turin, Italy who had iodine deficiency and thyroid dysfunction.

Researches then tested their perchlorate levels. Three years later they tested their children's IQ.  They found that women with the highest 10 percent of perchlorate levels were over three times more likely to have children with an IQ score in the lowest 10 percent.

Perchlorate is found in around 4 percent of the U.S. public drinking water, according to Scientific American. That affects 5 to 17 million people.  Perchlorate is most prevalent in the Western U.S., specifically near Las Vegas and Southern California.

A Canadian survey released in May reported that all samples of fresh fruits and vegetables, dairy products and infant formulae analyzed for perchlorate were safe for consumption.

The CFIA tested a total of 611 samples, including 433 fresh fruit and vegetable, 89 dairy product , and 89 infant formula samples, collected from Canadian retail stores.

The 2010-2011 study found that 65 percent of fresh fruit and vegetable, 87 percent of dairy product, and 63 percent of infant formula samples analyzed were found to contain very low levels of perchlorate, in the range of 2 to 540 parts per billion.

EPA officials have long gone back and forth as to whether to cap the amount of perchlorate allowable in drinking water.

In 2002, an EPA draft risk assessment found that 1 part per billion should be considered safe. Six years later, the Bush administration decided not to regulate the chemical, instead recommending that concentrations not exceed 15 parts per billion.

At the time, federal scientists estimated that 16.6 million Americans could be exposed to unsafe levels through their drinking water.

California and Massachusetts in the meantime have set state-level drinking water standards.

Currently, the EPA plans to unveil new standards for perchlorate in water in summer 2015.


Maternal perchlorate levels in women with borderline thyroid function during pregnancy and the cognitive development of their offspring; Data from the Controlled Antenatal Thyroid Study

Peter N Taylor et al.


Thyroid dysfunction is associated with impaired cognitive development. Perchlorate decreases thyroidal iodine uptake, potentially reducing thyroid hormone production. It is unclear whether perchlorate exposure in early life affects neurodevelopment.

Historical cohort analysis.
During 2002–2006, 21,846 women at gestational age <16 weeks recruited from antenatal clinics in Cardiff, UK and Turin, Italy were enrolled in the Controlled Antenatal Thyroid Screening Study (CATS). We undertook a retrospective analysis of 487 mother-child pairs in mothers who were hypothyroid/hypothyroxinemic during pregnancy and analyzed whether first trimester maternal perchlorate levels in the highest 10% of the study population were associated with increased odds of offspring IQ being in the lowest 10% at age 3 years.
Main Outcome Measures:
Maternal urinary perchlorate, offspring IQ.

Urine perchlorate was detectable in all women (median 2.58μg/liter); iodine levels were low (median 72μg/liter). Maternal perchlorate levels in the highest 10% of the population increased the odds of offspring IQ being in the lowest 10% OR=3.14 (95%CI 1.38, 7.13) p=0.006 with a greater negative impact observed on verbal OR=3.14 (95%CI 1.42, 6.90) p=0.005 than performance IQ. Maternal levothyroxine therapy did not reduce the negative impact of perchlorate on offspring IQ.

This is the first study using individual-level patient data to study maternal perchlorate exposure and offspring neurodevelopment and suggests that high-end maternal perchlorate levels in hypothyroid/hypothyroxinemic pregnant women have an adverse effect on offspring cognitive development, not affected by maternal levothyroxine therapy. These results require replication in additional studies, including in the euthyroid population.


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