The Environmental Protection Authority (EPA) is urging people to avoid using the herbicide chlorthal-dimethyl because of significant concerns about its effects on unborn children.

Chlorthal-dimethyl, also referred to as dimethyl tetrachloroterephthalate, DCPA, dacthal, or chlorthal-methyl, is used to control grasses and other weeds.

In New Zealand, it’s used particularly with onion crops, forest nurseries, and ornamental plants.

The EPA issued a red alert today to inform people of the health risks from chlorthal-dimethyl, and recommend people stop using products that contain this chemical.

"We are issuing this alert because we have serious concerns about the potential risks to people's health from this substance," says Dr Shaun Presow, Hazardous Substances Reassessments Manager.

"We urge anyone currently using a product containing chlorthal-dimethyl to stop and to consider alternatives."

If people can’t avoid using these products, the EPA advises they take all precautions to avoid exposure for people who are pregnant or could be pregnant. This includes restricting access to sprayed areas and making sure nobody else is around during spraying.

The EPA’s red alert comes after the United States Environmental Protection Agency (US EPA) issued an emergency order on 7 August 2024 to stop all use or sale of products containing chlorthal-dimethyl - the first time in 40 years it has taken this action.

The US EPA found a risk of thyroid hormone changes in the unborn children of pregnant bystanders, and women who apply chlorthal-dimethyl, or those who enter treated fields after the substance has been applied.

These changes can cause low birth weight and irreversible and life-long impacts, such as impaired brain development and motor skills.

"We take very seriously any significant new information about the potential effects of chemicals used in New Zealand," says Dr Presow.

"We’ve set up a working group to look at how this herbicide is being used here, and to take rapid action to ensure we continue protecting people’s health and safety.

"While this is happening, we have put out a red alert to ensure the public is aware of the potential risks.

"We’re currently consulting directly with those likely to be affected by any proposed additional rules for using products containing chlorthal-dimethyl and to help us better understand how widely it’s used in New Zealand."

The EPA will issue updates as this work progresses.

Notes:

• From 20-30 August 2024 we are consulting directly with anyone likely to be affected by restricting products containing chlorthal-dimethyl.
• This information will help us decide how best to manage the use of chlorthal-dimethyl, including considering whether grounds exist to reassess the substance as well as temporarily restricting or prohibiting its use under s64 or s64A of the Hazardous Substances and New Organisms Act (HSNO Act).

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