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Interim decisions and invitation for further comment on substances referred to the June 2019 ACMS/ACCS meetings

Scheduling of chemicals and poisons

12 September 2019

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2.1. Interim decision in relation to lambda-cyhalothrin

Interim decisions on proposed amendments referred to the Advisory Committee on Chemicals Scheduling (ACCS #25, June 2019)

Interim decision in relation to lambda-cyhalothrin

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 not to amend the current Poisons Standard in relation to lambda-cyhalothrin.

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

Applicant's scheduling proposal and reasons for the proposal

An application to amend the current Poisons Standard with respect to lambda-cyhalothrin was considered. The application proposed to amend the cut-off for lambda-cyhalothrin in Schedule 5 from 2.5 per cent to 4 per cent in aqueous preparations of microencapsulated lambda-cyhalothrin.

The Applicant's proposed amendments to the Poisons Standard were:

Schedule 5 - Amend Entry

LAMBDA-CYHALOTHRIN:

  1. in aqueous preparations containing 1 per cent or less of lambda-cyhalothrin; or
  2. in aqueous preparations containing 2.54 per cent or less of microencapsulated lambda-cyhalothrin.

The Applicant's main points provided in support of the proposed amendment were as follows:

  • The acute toxicity of the formulated product meets the criteria stipulated in the Scheduling Policy Framework, with the exception of the estimated acute oral toxicity, which was determined based on the up-and-down method.
  • The Australian Pesticides and Veterinary Medicines Authority (APVMA) recently evaluated acute toxicity data for a product containing approximately 3.5% lambda-cyhalothrin.
  • The formulated product had low toxicity via the oral, dermal and inhalation routes of exposure:
    • Oral LD50 in rats was estimated to be 1750 mg/kg bw using the up-and-down method;
    • Dermal LD50 in rats was >5000 mg/kg bw; and
    • Inhalation LC50 in rats was >2520 mg/m3 (nose-only; maximum attainable concentration).
  • The primary eye irritation study with the formulated product revealed slight irritation that resolved completely by 48 hours following administration of the test material.
  • The primary skin irritation study with the formulated product revealed slight irritation that resolved completely by 7 days following administration of the test material.
  • The product did not induce a sensitisation response when tested according to the Buehler method.

Current scheduling status

Lambda-cyhalothrin is currently listed in the Poisons Standard as follows:

Schedule 7

LAMBDA-CYHALOTHRIN except when included in Schedule 5 or 6.

Schedule 6

LAMBDA-CYHALOTHRIN:

  1. in aqueous preparations containing 25 per cent or less of microencapsulated lambda-cyhalothrin; or
  2. in emulsifiable granule formulations containing 25 per cent or less lambda-cyhalothrin; or
  3. in other preparations containing 1.6 per cent or less of lambda-cyhalothrin

except when included in Schedule 5.

Schedule 5

LAMBDA-CYHALOTHRIN:

  1. in aqueous preparations containing 1 per cent or less of lambda-cyhalothrin; or
  2. in aqueous preparations containing 2.5 per cent or less of microencapsulated lambda-cyhalothrin.

Index

LAMBDA-CYHALOTHRIN

Schedule 7
Schedule 6
Schedule 5

Scheduling history

In November 1987, the Drugs and Poisons Schedule Committee (DPSC) decided to include first aid and safety directions for lambda-cyhalothrin.

In August 1990, the DPSC decided to include preparations containing 1 per cent or less of lambda-cyhalothrin in Schedule 6 and all other preparations containing lambda-cyhalothrin in Schedule 7, based on the toxicity profile of lambda-cyhalothrin. Toxicity data discussed at this meeting included a one year oral dosing study in dogs, which revealed be short-lived and non-cumulative dose related neurotoxic effects. In addition, a study in human volunteers devoid of asthma revealed that aerosols of lambda-cyhalothrin elicited some mild reaction in more than 50 per cent of volunteers. A dose response relationship was established for the incidences of smarting and watering of the eyes, sneezing, blocked or runny noses and throat/lung irritation

In November 1991, the DPSC decided to include aqueous preparations containing 1 per cent or less of lambda-cyhalothrin in Schedule 5. The reason for this decision was that the water-based product containing 1 per cent or less of lambda-cyhalothrin provided it was confined to use by pest control operators through a registration mechanism. It is noted in the minutes that the oral LD50 for the product in rats was >2000 mg/kg.

In November 1994, the National Drugs and Poisons Schedule Committee (NDPSC) considered toxicological data on a microencapsulated aqueous suspensions containing 10 per cent lambda-cyhalothrin. Members noted that technical lambda-cyhalothrin had been demonstrated to have slight skin and eye irritancy and may cause transitory facial numbness in humans. The Committee agreed that because of the potential for moderate skin irritation and temporary facial numbness, and the restriction of its use to professional pest operators that microencapsulated aqueous suspensions containing 2.5 per cent or less of lambda-cyhalothrin be included in Schedule 5.

In August 1999, the NDPSC decided to include microencapsulated preparations containing 25 per cent or less of lambda-cyhalothrin in Schedule 6.

In August 2014, the chemicals scheduling delegate decided to increase the allowed concentration in Schedule 6 from 1.5 to 1.6 per cent to ensure that the product formulation, when expressed in grams per 100 millilitre (as per Part I of the Poisons Standard), is covered by the amended entry.

In October 2017, ACCS recommended, and the chemicals scheduling delegate agreed to amend the Schedule 6 entry for lambda-cyhalothrin to include emulsifiable granule formulations containing 25 per cent or less of lambda-cyhalothrin.

Australian regulations

International regulations

United States (US)

Lambda-cyhalothrin was registered with the US Environmental Protection Agency (US EPA) in 1989 and is registered as a biochemical/conventional chemical. It is a restricted use, broad spectrum insecticide used to control most major aphid, caterpillar and beetle pests on a wide variety of crops and for public health pests such as mosquitoes and cockroaches in non-agricultural settings.

Canada

Lambda-cyhalothrin is a registered pesticide with Health Canada.

UK

Lambda-cyhalothrin was first approved for use in the UK in 1988 (Advisory Committee on Pesticides, 1988).

EU

Lambda-cyhalothrin is currently a registered product with the European Chemicals Agency (ECHA). The ECHA hazard classification for lambda-cyhalothrin is, 'Danger! According to the classification provided by companies to ECHA in CLP notifications this substance is fatal if inhaled, is very toxic to aquatic life with long lasting effects, is toxic if swallowed, is toxic in contact with skin and is very toxic to aquatic life'.

New Zealand

Lambda-cyhalothrin is currently a registered product.

Substance summary

Lambda-cyhalothrin is a synthetic pyrethroid insecticide which contains only two (1R cis Z-S and 1S cis Z-R) of cyhalothrin's four possible stereoisomers. Lambda-cyhalothrin insecticidal activity is believed to be through interference with sodium channels in the nervous system of insects, leading to paralysis and, eventually, death.

Table 1: Chemical information for lambda-cyhalothrin
Property Lambda-cyhalothrin
Chemical structure Chemical structure of lambda-cyhalothrin
Molecular formula C23H19ClF3NO3
Molecular weight 449.85 g/mol
CAS name (R)-cyano(3-phenoxyphenyl)methyl (1S,3S)-rel-3-[(1Z)-2-chloro-3,3,3-trifluoro-1-propen-1-yl]-2,2-dimethylcyclopropanecarboxylate
CAS number 91465-08-6
IUPAC and/or common and/or other names 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl-cyano(3-phenoxyphenyl)methyl cyclopropane carboxylate (IUPAC)

Summary of pre-meeting public submissions

No public submissions were received in response to the proposed amendment.

Summary of ACCS advice/recommendations to the Delegate

The Committee recommended that the scheduling of lambda-cyhalothrin remains appropriate.

Members agreed that the relevant matters under Section 52E(1) of the Therapeutic Goods Act 1989 included: (a) 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; (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.

The reasons for the advice included:

  1. risks and benefits of the use of a substance:
    • Risks:
      • Product may be supplied in the domestic market, acute toxicity primarily neurotoxicity but we do not have detailed data on the nature of the toxic outcomes.
    • Benefits:
      • Used as a broad band insecticide.
      • Effective insecticide with a long history of use.
  2. the purpose for which a substance is to be used and the extent of use:
    • Product to be used by professionals only as an insecticide but it is used in commercial, industrial, domestic and public spaces.
  3. the toxicity of a substance:
    • Formulated product: Acute oral toxicity LD50 1750 mg/kg bw.
    • 4 hr inhalational LC50 = 2520 mg/m3 max attainable concentration.
    • Main route of exposure is dermal and inhalational.
    • Oral toxicity may be within Schedule 6 parameters for aqueous preparations of up to 4% microencapsulated lambda-cyhalothrin.
    • Acute oral toxicity is imprecise and the Committee are not confident in a down-scheduling or a change to the cut-off.
  4. the dosage, formulation, labelling, packaging and presentation of a substance:
    • Supplied as a concentrate in 250mL and 5L containers. Aqueous preparation of microencapsulated lambda-cyhalothrin.
    • Applied by hand held equipment.
    • Potential for backpack application.
    • Potential use in domestic settings.
  5. the potential for abuse of a substance:
    • Potential use by non-professionals.
  6. any other matters that the Secretary considers necessary to protect public health:
    • Nil.

Delegate's considerations

In making this interim decision, I have considered the following material:

  • The application to amend the current Poisons Standard with respect to lambda-cyhalothrin;
  • Advisory Committee on Chemicals Scheduling's advice;
  • Section 52E of the Therapeutic Goods Act 1989, in particular: (a) 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; (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;
  • The Australian Health Ministers' Advisory Council's Scheduling Policy Framework (SPF 2018); and
  • The Australian Health Ministers' Advisory Council's Scheduling Handbook (V 1.0, January 2018).

Reasons for interim decision

I agree with the Committee's finding that the relevant matters of section 52E of the Therapeutic Goods Act 1989 are: (a) 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; (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.

In my view, the relevant parts of the Scheduling Policy Framework (SPF) 2018 are the scheduling factors for Schedule 5.

I have made the decision not to amend the Schedule 5 entry for lambda-cyhalothrin in the Poisons Standard and I have set out my reasons below.

I have taken into account the toxicological data provided by the Applicant and I am not persuaded that the acute oral LD50 toxicity data can be reliably interpreted to justify a Schedule 5 entry. I consider the results from acute oral toxicity study that used the OECD Test Guideline (425) 'up and down' method for deriving the acute oral LD50 with a surrogate formulation containing approximately 4% w/v lambda-cyhalothrin, to be imprecise. As there was a death of one of the laboratory animals at 1750 mg/kg bw, the data does not provide confidence that the acute oral LD50 value can be extrapolated to a value greater than 2000 mg/kg bw as suggested by the Applicant. I am of the opinion that the data in this instance cannot be extrapolated in order to support a change to the scheduling cut-off for lambda-cyhalothrin.

I have also taken into account the potential for products containing lambda-cyhalothrin to be used in the domestic setting. The product is intended for professional use. However, it is possible that it may be used in domestic settings by non-professionals as the smallest proposed pack size is 250 mL. I acknowledge that domestic users can still buy a product containing lambda-cyhalothrin if it is in Schedule 6, but the signal heading "POISON" rather than "CAUTION" is considered more appropriate in maintaining public health given the proposed product's toxicity profile that is consistent with criteria listed in the SPF (2018).


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