2,4-D

Issue

Incidents of spray drift damage attributed to 2,4-D have been reported for a number of years with significant incidents in the last two summer spray seasons, and the APVMA has been working closely with grower groups, state and territory authorities, and other stakeholders to develop new label instructions to reduce the likelihood of off-target damage due to spray drift. 

We consider that currently approved 2,4-D labels do not provide adequate instructions to effectively mitigate risk associated with spray drift.

As of 3 October 2018, the new 2,4-D label instructions came into effect and old labels have been suspended. Users of 2,4-D must comply with the new label instructions, even if they are using products with the old labels.

The APVMA has issued permit PER 87174 "The New Instructions" to allow persons to possess, have custody of, supply, and/or use 2,4-D products currently on farm and in retail outlets. Supply at the point of retail sale must occur with the new instructions being provided with each container supplied.

A copy of the permit can be found here

These changes affect about 220 products, and the new instructions for use include:

  • a requirement not to spray in inversion conditions and additional information on recognising inversion conditions
  • downwind mandatory no spray zones for both aquatic and terrestrial off target vegetation (including sensitive crops, gardens, landscaping vegetation, protected native vegetation or protected animal habitat)
  • a requirement to use nozzles producing droplets no smaller than the VERY COARSE spray quality category
  • mandatory record keeping requirements, and
  • advisory statements about spray application over summer.

The new requirements do not change or restrict other aspects of the currently approved use patterns and should not affect availability of the product.

Products containing 2,4-D continue to be under review (reconsideration) by the APVMA. The review is expected to be completed in early 2019.

2,4-D (2,4-Dichlorophenoxyacetic acid) is a common chlorophenoxy herbicide used for the post-emergent control of broadleaf weeds. It is also used as a plant growth regulator for some fruit crops. There are around 220 products containing 2,4-D registered for use in Australia. 2,4-D has been registered for use for over 50 years.

APVMA’s current review of 2,4-D

All 2,4-D products currently registered for use in Australia have been through a robust chemical risk assessment process. The APVMA began a review of 2,4-D in 2003 due to concerns about its potential human toxicity (including carcinogenicity), occupational risks to people, risks to the environment and dietary risks due to residues in food. The review has examined all new and previously assessed scientific information. We expect the 2,4-D review findings and proposed recommendations to be available for public comment in the third quarter, 2018. Information about the review can be found on APVMA’s website.

Part 1 of the 2,4-D review involving high volatile ester (HVE) forms of 2,4-D has already been completed. Priority was given to the assessment of HVEs due to numerous reports of off-site plant deaths caused by 2,4-D HVE vapour movement. Regulatory action was taken cancelling most products containing 2,4-D HVEs.

Assessment of the other forms of 2,4-D is currently underway as Part 2 of the review and will include toxicity, occupational health and safety, environmental and residues assessments. The assessment reports will be published on the APVMA’s website when each report is finalised.

Assessment of 2,4-D products will also consider risks associated with dioxins impurities. Low levels of dioxins may be produced during the manufacturing process of 2,4-D. The assessment of 2,4-D will consider risks to workers and the public from exposure to dioxin contaminants in the 2,4-D products.

Revised timeline

Chemical Reviews (reconsiderations) are dynamic and our work plans must be flexible to consider:

  • new scientific information
  • our response to emerging issues that may need regulatory action to address.

The 2,4-D work plan has been reviewed and updated in line with the legislation and associated regulations. We have received additional assessment data from approval and registration holders since the review started on 1 July 2015, so the modular assessment levels in this work plan have been adjusted.

The 2,4-D review scope and work plan has been adjusted to include a toxicology level 3.2 assessment (previously a level 3.3) and environment level 7.1 assessment (previously a level 7.3). The recalculated timeframe for the 2,4-D review is 43 months. We expect the review findings and proposed recommendations to be available for public comment in the third quarter 2018.

Using 2,4-D products

Based on current risk assessments the label instructions on all registered 2,4-D products—when followed—provides adequate protection for users.

People should follow the use and safety instructions on all chemical product labels as these are designed to reduce human exposure to the chemical product. If the label has been removed or damaged, you can search the APVMA’s chemical database to find the safety information about registered products and permits.

Technical note on standards for the classification of nozzles in Australia

The 2,4-D permit instructions contains the restraint “DO NOT apply with spray droplets smaller than VERY COARSE spray droplets according to the ASAE S572.1 definition for standard nozzles.” Nozzle manufacturers commonly rely on the standard which is used in the jurisdiction in which they are based. Different nozzle standards are used because no undisputed international standard currently exists.

The APVMA recognises the following international standards for the classification of nozzles:

  • American Society of Agricultural and Biological Engineers (ASABE)
    • ASAE S572 FEB04: Spray Nozzle Classification by Droplet Spectra
    • ANSI/ASAE S572.1 MAR2009: Spray Nozzle Classification by Droplet Spectra
    • ANSI/ASAE S572.2 JUL2018: Spray Nozzle Classification by Droplet Spectra
  • British Crop Production Council (BCPC) (Southcombe et al. 1997)
  • ISO 25358: Crop protection equipment — Droplet-size spectra from atomizers — Measurement and classification

All these standards are compliant with the new 2,4-D instructions as they define droplet spectrum categories for the classification of spray nozzles, relative to specified reference nozzles.

The main difference between ASAE S572 and S572.1 is that additional categories of ULTRA COARSE and EXTREMELY FINE were added in S572.1. There is no difference between S572 and S572.1 that would alter classification for a VERY COARSE spray. The only change in S572.2 to S572.1 is to correct a flow rate error for ULTRA COARSE. Since ULTRA COARSE nozzles are available and used for drift mitigation, the 2,4-D instruction refers to S572.1. This version is also the common standard currently adopted by industry. The release of the APVMA’s spray drift policy in 2019 will address the interpretation of these standards with respect to mitigating spray drift.

A common misconception is that S572 is based on spraying water only and S572.1 is based on spraying a water/surfactant mix, but this is incorrect. The three ASAE standards (S572, S572.1 and S572.2) are based on spraying water only through both the reference nozzles and nozzles to be classified. For nozzles that are claimed to reduce spray drift, or utilise pre-orifices or internal turbulence chambers, a surfactant-water mixture should be used. All three versions of the ASAE standard state that a surfactant-water mix should be used for nozzles that are claimed to reduce drift, not that they must be used.

The addition of a pesticide to water can change the droplet size (and subsequent classification) produced by a nozzle. For example, a nozzle that is classified as VERY COARSE when spraying water only may actually be COARSE when spraying a water-surfactant mix or a pesticide alone.

Wherever possible, it is best to use a droplet size classification based on the actual product to be sprayed; product registrants should prepare and submit appropriate data packages to APVMA in a timely manner for evaluation through existing registration processes.

Since the three ASAE standards (S572, S572.1 and S572.2) state that a surfactant-water mix should be used for nozzles that are claimed to reduce drift, data generated using water only meets the label requirement for spray droplets according to the ASAE S572.1 definition for standard nozzles.

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