Chemical Found in Drinking Water May Be Responsible for Thyroid Disruption

A discovery published in Nature Structural and Molecular Biology journal has determined that perchlorate, an environmental pollutant that is also found in many drinking water sources in the United States, inhibits thyroid functions.

Vanderbilt researchers have identified that perchlorate inhibits the uptake of iodide. Iodide is a vital part of thyroid hormones and is crucial for thyroid hormone synthesis. Perchlorate exposure can occur through the ingestion of food and water contaminated with natural or manmade perchlorate.

These results came out amidst the decision of the Environmental Protection Agency (EPA) not to regulate perchlorate levels in drinking water. Perchlorate is a toxic compound that is also used in rocket fuel and contaminates water. This chemical compound has been linked to brain damage in fetuses and infants.

EPA Administrator Andrew Wheeler's decision on the non-imposition of perchlorate limits is against a court order. The resolution mandates EPA by the end of June to create a safe drinking-water standard for perchlorate. The policy from the EPA acknowledges that high level-exposures to the chemical compound can cause IQ damage but does not regulate it.

Perchlorate is used in missile fuel and has been applied for other purposes such as fireworks and fertilizers. This chemical has been studied for more than a decade. Unfortunately, industrial contamination of drinking water supplies has been widespread, making the regulation policies difficult.

The primary toxic effect on humans of exposure to the chemical is thyroid disruption. Perchlorate decreases the production of thyroid hormone and stops the iodide absorption into the thyroid. The thyroid hormone is crucial in neurodevelopment, metabolism, and other physiologic function. Based on growing evidence, young children, fetuses, pregnant women may be more susceptible to perchlorate.

Thyroid hormones are critical to the development of humans. These hormones are needed for the promotion of healthy growth from uterine life onwards. The production of thyroid hormones depends on the sodium /iodide symporter (NIS), which is a crucial protein found in thyroid cells. This protein transports iodide from the bloodstream and into the thyroid gland.

This study establishes that exposure and perchlorate contamination essentially changes the way by which NIS protein transfers iodide into the thyroid glands, making it less effective than without or less exposure to the chemical compound.

Even with low exposure to concentrations of perchlorate, there is a significant impact on iodide transport and the resulting thyroid hormone production.

According to the lead author of the research, Dr. Nancy Carrasco, a decision on the perchlorate concern may endanger public health, affecting a lot of communities across the country.

In 2011, the Obama administration announced that it planned to reverse the George W. Bush administration's decision not to regulate the chemical. For the first time, they proposed to regulate the chemical. However, the Defense Department and military contractors led aggressive efforts against the regulation of perchlorate.

The new policy will revoke the EPA findings from 2011 that the chemical compound presents serious health hazards that may affect around 5 to 16 million people.