Almost all public drinking water holds safe levels of propellant chemical, says agency

The US Environmental Protection Agency (EPA) has controversially decided not to set safety standards for perchlorate in public drinking water. The announcement on 3 October - a preliminary decision that will not be finalised until a month allowed for public comment - received a mixed response from toxicologists. 

Perchlorate - a propellant used in rocket fuel and fireworks - interferes with the thyroid gland’s iodine uptake and production of thyroid hormone, which can affect brain development and growth, especially in foetuses and babies. It has been detected in the drinking water of at least 26 US states. 

The EPA has said water with less than 24.5 parts per billion of perchlorate is safe to drink, but US lobby organisations such as the Environmental Working Group say research supports a stricter safety limit, down to 1 part per billion. 

The EPA has now concluded that perchlorate is ’not at levels of public health concern in more than 99 per cent of public drinking water systems.’ Therefore, the agency says there is no ’meaningful opportunity for health risk reduction’ through a national drinking water regulation. A draft of the decision was leaked in September. 

Toxicologist concern

Senior US toxicologists with government links told Chemistry World  they were concerned that the EPA’s decision allows water companies to forgo perchlorate testing, meaning hotbeds of exposure could be missed. They also claim the EPA hasn’t recognised the potential exposure of vulnerable newborns to perchlorate through contaminated breast milk and formula. 

’The EPA performed an extensive review of the scientific data and selected specific studies that supported [their] position,’ adds Thomas Zoeller, a University of Massachusetts researcher who has studied thyroid toxicology and brain development. 

Zoeller says the EPA ignored research by the US Centers for Disease Control and Prevention indicating that thyroid function is more sensitive to long-term low-dose perchlorate exposure than typically assumed.  

But other toxicologists say the chemical has been targeted unfairly, and that there is no evidence of perchlorate’s negative health effects at typical exposure levels. 

Jonathan Borak, a Yale University toxicologist, points out that perchlorate is only one of several agents that can affect the thyroid - others include nitrate and thiocyanate. ’The idea that we are dealing with perchlorate as the culprit strikes me as myopic,’ Borak says. ’We should be looking at the total load of these goitrogens.’ 

Meanwhile, Senator Barbara Boxer of the Senate Environment and Public Works Committee (which has jurisdiction over environmental regulation and policy issues like water quality) says she will push forward a bill she sponsored that would require the EPA to promptly set a standard for perchlorate in drinking water. The measure has stalled in the Senate but could be reintroduced in November or in the next Congress. 

Boxer also intends to support a lawsuit, planned by the nonprofit US environmental law firm Earthjustice, to legally challenge EPA’s final decision on perchlorate regulation. 

13 November update: The EPA has extended the time allowed for public comment on its preliminary decision to 28 November

Rebecca Trager, US correspondent for Research Day USA

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