Following an emergency suspension of all uses of the herbicide dimethyl tetrachloroterephthalate (DCPA), the U.S. Environmental Protection Agency is initiating a voluntary cancellation of registration of the weedkiller that has been in use for more than 60 years.
First registered in 1958 for control of broadleaf weeds in ornamental turf and row crops, DCPA is the active ingredient in the herbicide Dacthal. The EPA initiated the emergency order in early August in response to years of concerns affecting both end users and others exposed to the chemical.
Shortly after the EPA announced in early August that it was suspending use of Dacthal, AMVAC Chemical Corp. voluntarily halted sales of the product. The company announced in late August its intention to freely cancel all registration of the product in the U.S. and abroad.
The EPA contends DCPA poses a threat to applicators and those exposed to it for long periods and is a particular threat to pregnant women and unborn babies.
The EPA and AMVAC are working toward a return program for those who still possess existing stocks of Dacthal.
Safe use of DCPA had already been a subject of concern for many years when the EPA in 2022 issued a notice of intent to suspend production of technical grade DCPA citing "the registrant's long-standing failure to respond to EPA's request for necessary data" needed for EPA to fully evaluate the risks associated with DCPA.
"The data requested by EPA relate to the potential effects of DCPA on human thyroid development and function," the EPA said in a June 2022 news release. "If the active ingredient DCPA cannot be manufactured, the production of the formulated product, Dacthal, would stop by default."
That concern, according to AMVAC, stems from results of a test the company provided to the EPA.
The emergency suspension was the first time in almost 40 years EPA has taken such an action, following several years of efforts by the agency to require the submission of data that was due in January 2016 and then assess and address the risk this pesticide poses, the agency said. The EPA said it took this action because unborn babies whose pregnant mothers are exposed to DCPA, sometimes without even knowing the exposure has occurred, could experience changes to fetal thyroid hormone levels, and these changes are generally linked to low birth weight, impaired brain development, decreased IQ and impaired motor skills later in life, some of which may be irreversible.
The company contends that efforts to ban Dacthal are an overreach.
"It is important to note that EPA's findings are based upon the test results of a single, relatively new study that the Company had provided to the agency over two years ago which showed an effect on fetal rodents at certain dose levels," the company said in a recent news release. "As is typically the case with such studies, the observed effect was extrapolated to indicate a potential effect upon human beings. The suspension order, then, was issued by EPA on the premise of preventing potential harm, rather than in response to an actual, reported harm. The Company had been working with the EPA in good faith for over one year to identify risk mitigation measures that might alleviate concerns and allow continued use of high-benefit use patterns. However, these measures apparently did not give the EPA sufficient certainty at the time. The Company was also discussing with the EPA the potential for completion of additional toxicology and exposure studies that may have alleviated risk concerns, had they been afforded time to proceed. The Company nevertheless thanks EPA for expending time and resources to consider and evaluate the many proposed risk mitigation measures."
Safe use of DCPA had already been a subject of concern for many years when the EPA in 2022 issued a notice of intent to suspend production of technical grade DCPA citing "the registrant's long-standing failure to respond to EPA's request for necessary data" needed for EPA to fully evaluate the risks associated with DCPA.
The emergency suspension "prohibits anyone from distributing, selling, shipping or carrying out other similar activities for any pesticide product containing DCPA," according to the EPA. It also means that no person can continue using existing stocks of those products. The EPA and AMVAC are working toward a return program for those who still possess existing stocks of Dacthal.
"While the company continues to question EPA's conclusions in support of the suspension, we believe that the best course of action is to voluntarily cancel registrations of this product," the company said in the news release. "We are working apace with both state and federal authorities to effect product return and to remove Dacthal from channels of distribution. It is the Company's position that product stewardship be international in scope; thus, we will now proceed to voluntarily cancel all international registrations as well."