2,4-D

Background

In 2003, the APVMA began its reconsideration of 2,4-D because of concerns over risks to human health (including occupational health and safety) and the environment (including impacts on waterways, non-target animals and plants).

To address concerns regarding spray drift the APVMA undertook regulatory actions in 2005, 2013, 2018 and 2019 to strengthen label instructions, label restraints and label warnings in order to reduce the risk of undesirable chemical spray drift. The adequacy of instructions and warnings on product labels was also considered.

In 2018 and 2019 the APVMA suspended the label approvals of agricultural and commercial products containing 2,4-D and issued new instructions through a permit to reduce spray drift occurrences and damage to off target crops for the summer spray seasons.

On 24 October 2019, the APVMA published its proposed decision in respect to the reconsideration of 2,4-D. The consultation ran from 24 October 2019 to 31 January 2020, and 15 submissions were received.

On 3 September 2020, the APVMA published the final regulatory decision in respect to the review. Holders have 12 months to update their labels, and a copy of the deemed permit must be supplied with containers sold from the date of the decision. At the same time as the final regulatory decisions, a proposed decision was made to cancel prior approved labels so that all labels in the market will comply with the final regulatory decisions. Pending the outcome of submissions from holders, the decision will be made by 30 September 2020, which is the date the current permits related to spray drift (PER87451 and PER87174) expire.

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 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.?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.

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.

There is currently no evidence that historical human parental exposure to 2,4-D has adverse effects on? children.

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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