On August 7, 2025, the New Zealand Environmental Protection Authority (EPA) proposed a comprehensive ban on chlorthal-dimethyl (DCPA) weedkiller during its reassessment process and is seeking public feedback. The public may submit comments until October 6, 2025.
Background
DCPA is a herbicide used to control wireweed before vegetable emergence. In 2024, due to its impact on fetal development, the NZ EPA imposed restrictions on this chemical. Previously, the U.S. Environmental Protection Agency had issued an emergency suspension order. Currently, the chemical is banned in Australia, Canada, the European Union, and the United States.
DCPA primarily poses risks to three groups: pregnant bystanders, pregnant workers involved in related operations, and individuals entering treated areas. The chemical has endocrine-disrupting effects, and exposure during pregnancy may impair fetal development and cause long-term effects on offspring, including low birth weight, impaired brain development, and motor function deficits. Even with the strictest protective measures, such as wearing respirators and gloves during spraying, the risks cannot be adequately mitigated. Additionally, DCPA poses a risk of groundwater contamination.
Studies have found that the use of DCPA in agriculture is already relatively low, with approximately two-thirds of New Zealand growers having switched to cheaper and more readily available alternatives.
Assessment Conclusion
Under the Hazardous Substances and New Organisms Act 1996 (HSNO Act), a comprehensive review and risk assessment are required before revoking approval for a substance. The EPA has completed a detailed assessment of the substance's usage, associated risks, and mitigation measures. It concluded that the health and environmental risks of continued use outweigh its benefits, citing the following reasons:
- Inability to effectively mitigate health risks for pregnant women;
- Inability to effectively address groundwater contamination;
- Limited use of the substance in New Zealand;
- Availability of more economical alternatives.
If the proposal is approved, all approvals for herbicides containing DCPA will be revoked under the HSNO Act, and the import, manufacture, and use of such products will be prohibited in New Zealand. However, a six-month period will be allowed for the disposal of existing stocks.
