2.3. Aclonifen

2 Interim decisions on proposed amendments referred to the Advisory Committee on Chemicals Scheduling (ACCS #7, March 2020)

2.3. Interim decision in relation to aclonifen

Interim decision

Pursuant to regulation 42ZCZN of the Regulations, a Delegate of the Secretary has, in relation to the proposed amendment, made an interim decision to amend the current Poisons Standard in relation to aclonifen as follows:

Proposed date of effect of the proposed amendment

1 October 2020

Reasons for the interim decision (including findings on material questions of fact)

In making this interim decision, the Delegate considered the following material:

• The application to amend the current Poisons Standard with respect to aclonifen;
• Advisory Committee on Chemicals Scheduling's advice;
• Section 52E of the Therapeutic Goods Act 1989, in particular (a) the risks and benefits of the use of a substance; (b) the purposes for which a substance is to be used and the extent of use of a substance; (c) the toxicity of a substance; (d) the dosage, formulation, labelling, packaging and presentation of a substance; and (e) the potential for abuse of a substance;
• Scheduling handbook: Guidance for amending the Poisons Standard;
• Scheduling Policy Framework (SPF 2018).

Pre-meeting public submissions

In response to the notice published under regulation 42ZCZK advising of the proposed amendment no public submissions were received.

Summary of ACCS advice/recommendations to the Delegate

The Advisory Committee on Chemicals Scheduling recommended that a new Schedule 6 entry for aclonifen is created in the Poison Standard as follows:

The reasons for the advice included:

1. risks and benefits of the use of a substance
   • Benefits
     • Herbicide for wheat, barley, triticale crops with risks managed by suitable labelling for PPE.
     • Not for the domestic market.
2. the purpose for which a substance is to be used and the extent of use
   • Herbicide intended for use in broad acre crops, thus low risk of general public exposure.
3. the toxicity of a substance
   • Low acute toxicity, no skin or eye toxicity (slight irritant).
   • Sensitiser potential in GPMT (most animals).
   • Carcinogenicity without genotoxicity potential.
4. the dosage, formulation, labelling, packaging and presentation of a substance
   • NIL.
5. the potential for abuse of a substance
   • NIL.
6. any other matters that the Secretary considers necessary to protect public health
   • NIL.

Reasons for interim decision

I agree with the Committee's findings that the relevant provisions of section 52E of the Therapeutic Goods Act 1989 are (a) the risks and benefits of the use of a substance; (b) the purpose for which a substance is to be used and the and extent of use of a substance; and (c) the toxicity of a substance.

In my view, the relevant parts of the SPF 2018 are the Scheduling Factors for Schedule 5, Schedule 6 and Schedule 7.

I have made a decision to create a new Schedule 6 entry for aclonifen. In making my decision I have taken into account data demonstrating that aclonifen is a skin sensitiser and is a non-genotoxic carcinogen.

Aclonifen is a new nitro diphenylether herbicide. While there is currently no product application associated with the active constituent, the APVMA has confirmed that a submission for an end-use product for use in broad acre situations is anticipated.

Concordant with the Scheduling Factors for inclusion in Schedule 5, aclonifen is of low acute oral (LD₅₀ >5000 mg/kg bw), dermal (LD₅₀ >5000 mg/kg bw), and inhalation toxicity (LC₅₀ > 5069 mg/m³/4h), is not a skin irritant and is a slight eye irritant in rabbits, with symptoms exhibited in one test animal resolving within 48 hours. There is no evidence of developmental toxicity (up to up to 25 mg/kg/d in rabbits), reproductive toxicity, or genotoxic potential in an acceptable range of in vivo and in vitro assays. However, aclonifen caused overt skin sensitisation in the maximisation test in guinea pigs (GPMT), consistent with Schedule 6. There was also evidence of a potential for aclonifen to bind chromatin, and thus has a theoretical potential to induce changes in DNA expression.

While the toxicity of aclonifen is less than that of other chemicals in the same class, I considered whether, based on the carcinogenicity concerns and the uncertainty around the mode of action (MOA), aclonifen poses a moderate or high health hazard from repeated use and a moderate or high risk of producing irreversible toxicity. I find that aclonifen presents a moderate hazard from repeated use and a moderate risk of producing irreversible toxicity, consistent with a Schedule 6 entry. Importantly, there was only a single study showing an increased incidence of a rare tumour (astrocytoma) in rats. I have noted that the EU has classified aclonifen with the risk phrase R40, 'Limited evidence of a carcinogenic effect', on the basis of the unresolved origin of the malignant astrocytomas in female rats and the uncertainty regarding the comparability of rats and humans in this respect. I have also given weight to the fact that the acute toxicological data does not support that aclonifen presents high to extremely high toxicity and there was no evidence to support that it has a high potential for causing harm at low exposures.

While aclonifen poses a moderate hazard from repeated use and a moderate risk of producing irreversible toxicity, these risks are manageable. The APVMA has confirmed that the management of health risks associated with pesticide use is achieved primarily via label directions, established from a consideration of the acute hazards of the product in conjunction with possible adverse health effects from repeated exposure to both workers and the general-public. In assessing the risk to users of products containing aclonifen or people consuming crops that have been treated with aclonifen, the APVMA applies a margin of exposure (MOE) of 100 to the No Observed Adverse Effect Level (NOAEL). As products containing aclonifen are neither intended to be made available directly to members of the public, nor are they intended for use in areas with ready public access, I am satisfied that the pesticide regulator (APVMA) will be able to manage the risks from exposure to products containing aclonifen.

Having considered all available information, I am satisfied that on balance, the evidence supports that a Schedule 6 entry with no concentration cut-off is appropriate for aclonifen.

Implementation date

I have decided on an implementation date of 1 October 2020.