The Environmental Protection Authority has issued a “red alert” urging New Zealanders to cease using the herbicide chlorthal-dimethyl due to significant concerns about its impact on unborn children.

The chemical, also known by several other names, including DCPA and dacthal, is commonly used in the country on onion crops, in forest nurseries, and for ornamental plants.

Dr Shaun Presow, the EPA’s Hazardous Substances Reassessments Manager said “We are issuing this alert because we have serious concerns about the potential risks to people’s health from this substance. We urge anyone currently using a product containing chlorthal-dimethyl to stop and to consider alternatives.”

The EPA’s action follows an emergency order issued by the United States Environmental Protection Agency (US EPA) on 7 August 2024, which halted all use and sale of products containing chlorthal-dimethyl.

This marked the first time in 40 years that the US EPA had taken such a drastic step.

Their research highlighted alarming findings, showing that exposure to chlorthal-dimethyl could lead to thyroid hormone changes in the unborn children of pregnant bystanders and women who come into contact with treated fields.

These changes pose risks of low birth weight and long-term developmental issues, including impaired brain development and motor skills.

In response, the EPA has established a working group to assess the use of this herbicide in New Zealand.

Dr Presow said, “We take very seriously any significant new information about the potential effects of chemicals used in New Zealand. 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 the working group investigates, the red alert is intended to raise public awareness and encourage precautionary measures.

The EPA advises that if avoidance of these products is impossible, strict precautions should be taken to protect pregnant women or those who could become pregnant. These precautions include restricting access to sprayed areas and ensuring that no one else is present during the application of the herbicide.

“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,” Dr Presow said.