Safe perchlorate levels released by EPA

An official "safe" dosage level for common chemical perchlorate has been set this week by the US Environmental Protection Agency (EPA) in a bid to protect the American public from its affects.

Perchlorate damaged the thyroid gland, decreasing the amount of thyroid hormones produced in the body, and can cause prenatal and postnatal problems, as well as have adverse affects on the metabolic system and normal mental functions.

The substance is used in items including missile and rocket propellants and munitions, as well as everyday items such as fireworks, flares, airbags, pharmaceuticals and fertilizer. It has also been detected in drinking water systems around the US, as well as in some foods.

EPA has established an official reference dose (RfD) of 0.0007 mg/kg/day of perchlorate, consistent with the recommended reference dose included in the National Academy of Science’s January 2005 report.

A reference dose is a scientific estimate of a daily exposure level that is not expected to cause adverse health effects in humans.

Assuming total perchlorate intake from both water and food sources, EPA claims that the RfD is appropriate and protective for all populations, even including the most sensitive subgroups, including the fetuses of pregnant women who might have hypothyroidism or iodide deficiency.

This uncertainty factor also covers variability among other human life stages, gender and individual sensitivities, protecting not only adults, but also other sensitive subpopulations such as premature neonates, infants and developing children.

Perchlorate exposure has the potential of blocking iodide uptake to the thyroid gland. NAS identified the non-adverse effect of the inhibition of iodine uptake as the key biochemical event that precedes the occurrence of all potential adverse effects of perchlorate exposure.

EPA’s Superfund cleanup programme plans to issue guidance based on the new RfD.

By Jane Kettle

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