Diazinon review history and regulatory outcomes

Nomination for review

In December 1996 the APVMA (formerly the NRA) began a review of diazinon because of concerns over the potential for diazinon to form highly toxic breakdown products, particularly if the chemical is exposed to a small amount of water. Other concerns related to diazinon’s potential to pose a risk to public health, occupational health and safety, the environment, animals, and the impact of diazinon residues on Australia’s trade.

In February 2000 the NRA Expert Panel on Organophosphate Sheep Dips (the Panel) reviewed the findings of the UK Institute of Occupational Medicine (IOM) report, Epidemiological study of the relationship between exposure to organophosphate pesticides and indices of chronic peripheral neuropathy, and neuropsychological abnormalities in sheep farmers and dippers (July 1999). The Panel found that work practices and exposure risks differed between Australia and the UK. However, the panel could not completely rule out a link between OP exposure and long-term effects. The panel recommended reducing worker exposure to OPs and that the APVMA (formerly the NRA) review the uses of OPs on sheep. Those recommendations of the Panel which have direct implications for the review of diazinon will be incorporated in the review outcomes.

This review is separate from, but related to, the review of selected sheep ectoparasiticides. While the review of diazinon will be conducted separately, the outcomes of this review maybe taken into consideration in finalising related reviews.

Draft reports

In August 2000 the APVMA released the Diazinon Draft Report* which identified concerns over the potential risks to workers from some use patterns and a lack of sufficient data to support some use patterns and agricultural practices. Because of these data gaps the APVMA asked registrants and key user groups to provide more data to support the use of this chemical.

In August 2002 the APVMA released the Revised Diazinon Draft Report in response to receiving additional information and comments after the publication of the initial draft report. The APVMA found that emulsifiable concentrates (EC) products without stabiliser posed an undue hazard to the safety of people and animals as these products could break down to produce highly toxic impurities. The APVMA also found that stabilised EC products used on companion animals posed an undue hazard to the environment.

2003 Review Findings: Part 1 Product Cancellations

Reflecting the findings of the Revised Diazinon Draft Report, in April 2003 the APVMA released the Diazinon Review Findings Report Part 1. The report focused on the cancellation of products that were hydrocarbon (water) based formulations and that contained insufficient stabiliser. The report also dealt with the cancellation of a small number of companion animal products containing diazinon.

The APVMA’s key findings for Part 1 were:

EC and water-based products pose a potential risk to public health and animal safety
stabilised EC products containing diazinon that are companion animal (dog and kennel flea) treatments pose a risk to the environment following the disposal of these products in urban sewers and stormwater drains.

In the report the APVMA recommended:

cancelling hydrocarbon-based products containing diazinon without adequate stabiliser, including emulsifiable concentrates
cancelling stabilised EC products used on companion animals.

Preliminary review: Part 2

In June 2006 the APVMA released the Diazinon Preliminary Findings Review Report Part 2. Part 2 of the diazinon review considers products approved for use on sheep, cattle, pigs, goats and horses. The findings of Part 2 are supplementary to those findings published in the 2002 Revised Diazinon Draft Report.

The APVMA’s key preliminary findings for Part 2 were:

ECs containing diazinon may form toxic breakdown products following prolonged storage or if diluted in oil or kerosene
uses of diazinon in enclosed spaces, for domestic pest control, and on turf may pose an unacceptable risk of inhalation toxicity from volatilisation during and after application
all methods of application on sheep (portable and fixed plunge dipping, shower dipping and hand and auto race jetting) pose an unacceptable hazard for workers even when they are wearing personal protective equipment (PPE)
the use of diazinon in flea shampoos for dogs may pose a risk to the environment
the use of diazinon on citrus, pastures, rice, sugar cane and stagnant water/ponds may pose a risk to the environment
Maximum Residue Limits (MRLs) and appropriate withholding periods can be established for agricultural use only on mushrooms, onions, pineapples and bananas
diazinon residues in processed dairy commodities containing high fat levels (e.g. cheese) may pose a risk to Australia’s export trade.

In the preliminary report the APVMA proposed:

that ECs containing diazinon should have a shelf life of not longer than 12 months
deleting the label instructions for diluting ECs in oil or kerosene
deleting all uses of diazinon in enclosed spaces (except mushroom housing) or for use in domestic pest control and turf treatments
deleting the uses of products containing diazinon as dog shampoos, and deleting use on citrus, pastures, rice, sugar cane and stagnant water/ponds
establishing MRLs for mushrooms, onions, pineapples and bananas and deleting all other agricultural uses from product labels, on the basis of inadequate residue data
strengthening the safety directions on cattle ear tags to prevent the use of these products on dairy cows producing milk for human consumption.

The APVMA will issue a final report once the assessment of all available data is completed.

For more information please contact the Chemical Review Program on (02) 6210 4749 or by email to chemrev@apvma.gov.au

* Contact the APVMA for copies of this document.