Due to the adverse health effects associated with exposure to dimethyltetrachloroterephthalate (DCPA), commonly known as Dacthal, the U.S. Environmental Protection Agency (EPA) has issued an emergency order immediately suspending all registrations of the pesticide. According to the agency, this is the first time in 40 years that the EPA has issued an emergency order to stop the use of a pesticide. The action “follows years of efforts to require the submission of long-overdue data” to support a risk assessment.
Dacthal is a herbicide that was previously approved for both agricultural and non-agricultural uses and was primarily used by the industry on crops such as broccoli, Brussels sprouts, cabbage and onions. Scientific literature has shown that exposure to Dacthal during pregnancy affects fetal thyroid hormone levels, which can lead to low birth weight, impaired brain development, reduced IQ and impaired fine motor skills.
“DCPA is so dangerous that it must be removed from the market immediately,” said an EPA spokesman. The emergency suspension was made under the Federal Law on Insecticides, Fungicides and Rodenticides (FIFRA).
At the time of the emergency order’s publication, Dacthal is undergoing registration review, a process for periodically re-evaluating registered agricultural chemicals to ensure they do not cause unreasonable adverse effects on human health or the environment. In 2013, the agency issued a data call-in (DCI) to AMVAC Chemical Corporation, the sole manufacturer of Dacthal, requiring it to submit more than 20 studies to support the herbicide’s existing registrations by January 2016. The required data included a comprehensive study of Dacthal’s effects on adult thyroid development and function, as well as on young development before and after birth. Several of the studies submitted by AMVAC between 2013 and 2021 were deemed insufficient to support the DCI, while studies on thyroid effects and other allegations were not submitted at all.
In April 2022, EPA issued a notice of intent to suspend the DCPA engineered product (used to manufacture end-use products) because AMVAC had not submitted the full set of required data, including thyroid studies, for nearly 10 years. Although AMVAC submitted the required thyroid study in August 2022, EPA suspended registration because AMVAC continued to fail to submit other pending data following an administrative hearing.
In November 2023, the suspension of data transfer was lifted after AMVAC had submitted sufficient data.
However, in May 2023, EPA released its assessment of the risks of occupational and residential exposure to products containing DCPA after analyzing the thyroid study submitted by AMVAC. The assessment found that there are health risks associated with the use and application of DCPA, even when personal protective equipment and engineering control measures are used. In a letter to AMVAC dated March 27, 2024, EPA reiterated the risks identified by the agency and noted that the agency would pursue regulatory options as soon as possible, including de-registration of the pesticide or requesting an emergency suspension.
