Gazette APVMA 6, 6 June 2006 page 21

NOTICE

Azimsulfuron

[in the product: Dupont Gulliver Herbicide]

The Australian Pesticides and Veterinary Medicines Authority (APVMA) has before it an application from Du Pont (Australia) Limited, for registration of a new product containing the new active constituent azimsulfuron. The product DUPONT GULLIVER HERBICIDE is used for the control of certain aquatic weeds and the suppression of barnyard grass in rice, applied early post-emergence of crop and weeds.

In accordance with section 13 of the Agvet Code, the APVMA invites any person to submit a relevant written submission as to whether the application for registration should be granted. Submissions should state the grounds on which they are based. Such grounds should relate only to matters outlined below that the APVMA is required to take into account in deciding whether to grant the application. Comments must be received by the APVMA within 28 days of the date of this notice.

Particulars of Application

Proposed product name: DUPONT GULLIVER HERBICIDE.
Applicant company: Du Pont (Australia) Limited
Name of active constituent: Azimsulfuron
Formulation Type: Dry Flowable
Poisons Scheduling: Exempt
Statement of claims: For post-emergence contol of certain broadleaf aquatic weeds and
the suppression of barnyard grass, in rice
Pack sizes: 200 g, 400 g, 500 g, 800 g and 1kg
Withholding period:

Harvest (Rice): Not required when used as directed.
Grazing / Stockfeed: Do not graze or use as stockfeed for 2 weeks after application.

The following Maximum Residue Limits (MRLs) are recommended in relation to the proposed use of DUPONT GULLIVER HERBICIDE:

Table-1: Azimsulfuron Rice and various animal products *0.02 mg/kg
Table-4: Azimsulfuron Rice fodder (fresh/dry), straw *0.05 mg/kg

(* : Limit of quantitation [LOQ] for active in the relevant commodity)

Summary of the APVMA’s evaluation of DUPONT GULLIVER HERBICIDE in accordance with Section 14(3)(e) and (f) of the Agricultural and Veterinary Chemicals Code (the ‘Agvet Code’), scheduled to the Agricultural and Veterinary Chemicals Code Act 1994

The APVMA has evaluated the application and in its assessment in relation to human and environmental safety under section 14(3)(e) of the Agvet Code, it proposes to determine that:

(i) The Office of Chemical Safety (OCS) of the Australian Government Department of Health and Ageing has assessed the toxicology of the active and product.
Azimsulfuron is closely related to compounds such as bensulfuron methyl which have been registered for use in herbicidal preparations for some time.
Azimsulfuron was readily absorbed from the gastrointestinal tract of rats and was rapidly and almost completely eliminated, mainly in the urine and mostly as unchanged compound. It had low acute oral toxicity in mice and rats, low dermal and inhalational toxicity in rats, and low potential for irritation and sensitisation.

The product, DUPONT GULLIVER HERBICIDE had low acute oral and dermal toxicity in rats. It was a slight skin and eye irritant in rabbits but was not a skin sensitiser in guinea pigs.

In repeat dose studies, the main target organs for toxicity were the pancreas, liver, testes and epididymides. The effects in the pancreas were fully reversible in rats. Although azimsulfuron has some effects on the testes and epididymides in rats, these effects are also likely to be reversible and there was no functional effect on reproductive performance. Mild anaemia was also observed leading to secondary effects such as increased spleen weight and increased formation of new red blood cells.

Azimsulfuron was associated with minor variations in the development of rat foetuses, but only at doses also toxic to the mother and there was no effect on the development of rabbit foetuses.

A range of special studies demonstrated that azimsulfuron did not damage genetic material and long-term studies in mice and rats showed no increase in the incidence of cancer.

Based on an assessment of the toxicology, OCS considered that there should be no adverse effects on human health from the use of DUPONT GULLIVER HERBICIDE when used in accordance with the label directions.

The APVMA has considered the OCS report and accepts its findings and recommendations. Consequently the APVMA is satisfied that the proposed use of DUPONT GULLIVER HERBICIDE is not likely to be harmful to human beings if used according to the product label directions.

(ii) Residue data was assessed by the APVMA and Maximum Residue Limits (MRLs) and Withholding Periods (WHPs) were set for DUPONT GULLIVER HERBICIDE on the crops listed on the label.

Metabolism studies demonstrate that azimsulfuron is readily metabolised in plant and animal tissues following absorption or ingestion. In animals, there is rapid absorption and elimination of the chemical, with negligible residues being found in the tissues following exposure.

Residue data show that when azimsulfuron is applied to rice crops according to the proposed use, residues in harvested grain were less than 0.02 mg/kg. These data support a rice MRL of *0.02 mg/kg. In conjunction with this MRL, a harvesting WHP is not required when DUPONT GULLIVER HERBICIDE is used as directed.

Rice straw and forage from treated crops may be grazed or fed to animals. Based upon the metabolism studies conducted on azimsulfuron, animal exposure to azimsulfuron residues in feed is unlikely to result in detectable residues in meat, milk, and eggs. Appropriate analytical methodology is available for the determination of residues in animal commodities, with the limit of quantification [LOQ] being 0.02 mg/kg. Accordingly, animal commodity MRLs of *0.02 mg/kg will be established for meat, offal, eggs, and milk.

Rice forage collected two weeks after treatment contained residue levels below the (forage) LOQ of 0.05 mg/kg. Similarly, rice straw collected at harvest contained residue levels below the LOQ of 0.05 mg/kg. These results support animal feed commodity MRLs of *0.05 mg/kg for rice forage and for rice straw and fodder. In conjunction with these MRLs, a grazing/stock-feed WHP of 2 weeks is recommended.

The registration of DUPONT GULLIVER HERBICIDE does not pose a risk to human health with respect to dietary intake. The estimated daily dietary intake (NEDI) is equivalent to less than 1% of the Acceptable Daily Intake (ADI) [for no chronic effect]. The dietary intake is also less than 1% of the Acceptable Reference Dose (ARfD) [for no acute effects].

Hence the APVMA is satisfied that the proposed use of DUPONT GULLIVER HERBICIDE will not be an undue hazard to the safety of people using anything containing its residues.

(iii) The Office of Chemical Safety has conducted an OH&S risk assessment on DUPONT GULLIVER HERBICIDE. Based on available information, DUPONT GULLIVER HERBICIDE could not be classified as hazardous according to NOHSC Approved Criteria for Classifying Hazardous Substances. The product will be formulated and packaged in Australia, using imported active constituent.

End users may be exposed to the product when opening containers, preparing spray, applying spray, maintaining equipment and cleaning up spills. In addition, workers re-entering treated crops to carry out crop management practices can be exposed to product residues.

Based on the toxicology profile of the product, the risk assessment indicates that suitable, personal protective equipment (PPE) should be worn when opening the container, preparing spray and when applying the diluted spray.

Hence the OCS concluded that DUPONT GULLIVER HERBICIDE can be safely used by workers when handled in accordance with the control measures indicated.

The APVMA has considered the OH&S evaluation, and accepts its findings and recommendations. Hence the APVMA is satisfied that the proposed use of DUPONT GULLIVER HERBICIDE would not be an undue hazard to the safety of people exposed to it during its handling and use.

(iv) The Department of the Environment and Heritage (DEH) has assessed data in support of of the proposed use of DUPONT GULLIVER HERBICIDE.

Azimsulfuron is only slowly hydrolysed and photolysed in distilled water, but photolysis is faster in natural water. It is readily to fairly rapidly degraded in aerobic soil. Aquatic metabolism in the dark is slow. Under anaerobic conditions degradation is also slow. In sterilised soils, the rate of chemical hydrolyses was slower than that of the microbial decomposition. Azimsulfuron is weakly to moderately adsorbed, with mobility ranging from low to very high. The major metabolites of azimsulfuron were shown to be less mobile than the parent.

Azimsulfuron is practically non-toxic to fish and aquatic invertebrates, but very highly toxic to algae and aquatic plants. The most sensitive organism was duckweed. It is non-toxic to birds by the acute oral and dietary routes.

Azimsulfuron is practically harmless to bees, parasitic wasps, green lacewings, predatory mites, ground-dwelling beetles and earthworms. There was no significant toxicity to soil micro-organisms or mammals.

As expected for a herbicide, azimsulfuron is very toxic to non-target vegetation, especially post-emergence. It is more herbicidal to dicotyledons than monocotyledons.

DEH has concluded that the risks to the environment from the proposed use of DUPONT GULLIVER HERBICIDE are acceptable when applied by aerial application equipment, provided a 200 m down-wind spray-drift buffer zone is used. For ground application, the APVMA has recommended a conservative down-wind buffer zone of 20 m.

The APVMA has considered the findings of the Department of the Environment and Heritage and accepts its recommendations on this criterion. The APVMA is satisfied that the proposed use of new product DUPONT GULLIVER HERBICIDE would not be likely to have an unintended effect that is harmful to animals, plants or the environment.

(v) The APVMA has assessed data and information on the proposed use of new product DUPONT GULLIVER HERBICIDE, with respect to any potential adverse affect on trade between Australia and places outside Australia.

With respect to trade, there are limited MRLs/tolerances established for azimsulfuron in rice.

However, quantifiable residues are unlikely to occur in harvested rice grain and processed commodities thereof, when DUPONT GULLIVER HERBICIDE is used in accordance with the label directions and Good Agricultural Practice. Accordingly, export of rice grain harvested from treated crops is not expected to unduly prejudice Australian trade.

A grazing/stock food interval of two weeks will apply to rice forage following DUPONT GULLIVER HERBICIDE treatment. Consequently, the likelihood of detectable residues occurring in meat and meat products as a result of animal exposure to rice forage, straw and grain from treated crop is considered small. Accordingly, the use of DUPONT GULLIVER HERBICIDE on rice is not expected to unduly prejudice Austrailan trade in meat and meat products.

Hence the APVMA is satisfied that the proposed use of DUPONT GULLIVER HERBICIDE on rice crops should not adversely affect trade between Australia and places outside Australia. In relation to its assessment of efficacy under section 14(3)(f), the APVMA proposes to determine that it is satisfied the data from trials supporting the efficacy of DUPONT GULLIVER HERBICIDE adequately demonstrates that under local conditions this product is effective for the proposed uses.

Public Release Summary

A Public Release Summary of the evaluation is available by contacting David Hutchison on telephone (02) 6271-6384. Written submissions on the APVMA’s proposal to grant the application for registration should be received at the APVMA by 4 July 2006, and addressed in writing to:

John MacDonald
Pesticides Division
Australian Pesticides and Veterinary Medicines Authority
PO Box E240
KINGSTON ACT 2604

Phone: (02) 6272-3688
Fax: (02) 6272-3218
Email: john.macdonald@apvma.gov.au