Dacthal herbicide withdrawn in US over risks to foetal development

The US Environmental Protection Agency (EPA) is cancelling registrations of all products containing the herbicide dimethyl tetrachloroterephthalate (DCPA, Dacthal) at the request of their sole US supplier, American Vanguard, after prolonged negotiations between the company and the EPA over safety data.

American Vanguard says it had voluntarily ended sales of Dacthal herbicide products in April this year. But on 6 August, the EPA issued a rare emergency suspension to prevent any existing supplies being sold or used, over continuing concerns that exposure of pregnant women can cause irreversible harm to their unborn babies that may not show up for years. In light of the suspension, the company is now voluntarily cancelling all its US and remaining international product registrations.

DCPA has been classified by the EPA as a likely carcinogen since 1995, and has was banned for use on crops in the EU in 2009. In 2013, the EPA had requested additional data to support the product’s registrations. American Vanguard provided some of the requested data, but some remained either missing or deemed inadequate by the agency for almost 10 years.

Once the EPA had assessed the data it received from American Vanguard on thyroid toxicity, and following further negotiations with company over the product’s use, the agency decided to invoke its emergency powers to suspend (and potentially cancel) the registrations – a step the agency had not taken for over 40 years previously.

The EPA said its emergency decision on DCPA is based on a risk of thyroid hormone perturbations in the foetuses of female bystanders and workers who apply DCPA or who enter treated fields for several weeks after application. The evidence considered by the agency demonstrated thyroid toxicity generally linked to low birth weight, impaired brain development, decreased IQ and impaired motor skills later in life.

While American Vanguard has questioned the EPA’s conclusions relating to the suspension, it has nevertheless decided to voluntarily cancel its registrations. ‘We are working apace with both state and federal authorities to effect product return and to remove Dacthal from channels of distribution,’ the company stated.