DICHLORVOS (DDVP) is a chemical to be respected due to the following attributes:
- Extremely volatile
- Toxic (S6) - Organic Phosphate - affects nervous system (one formulation is a S7)
- Readily absorbed by skin contact, inhalation and orally by contaminated goods
- Can activate Asthma reaction in susceptible people
- Can damage plastics
- Can cause staining
The Australian Pesticides & Veterinary Medicines Authority (APVMA) instigated a review of Dichlorvos (DDVP) and in June 2008 released its preliminary findings. These are important for anyone using Dichlorvos products as the findings indicated that:
- Safety directions on Dichlorvos labels did not conform to current safety standards and did not provide adequate environment protection information.
- There was insufficient data available from manufacturers or registrants for the APVMA to be satisfied there was adequate protection from exposure by workers, people in domestic situations and residues in food commodities e.g. where used for grain pest treatments.
- The labels for Dichlorvos were generally quite old and needed review.
Dichlorvos is an organophosphorus insecticide first synthesised in the late 1940s. Commercial production of Dichlorvos began in 1961. Insects are killed by interference with an enzyme (cholinesterase) in the nervous system, resulting in muscle paralysis.
THE APVMA RELEASED ITS FINAL REPORT and REGULATORY DECISIONS for DDVP in MARCH 2011
The existing poisons schedule for dichlorvos depends on the percentage of Dichlorvos in the product and the formulation and can be S5, S6 or S7. The majority are S6.
The review identified a number of additions and amendments required for the existing First Aid Instructions and Safety Directions (FAISDs) for Australian Dichlorvos products.
The Review found:
That operators applying Dichlorvos are likely to be exposed extensively by the dermal and inhalation routes. Pest Control operator exposure studies has shown that even with the highest level of personal protective equipment, it is not possible to assure adequate MOEs (Margins of Exposure) to protect persons applying dichlorvos indoors or outdoors by surface and space spray. Similarly, MOEs are inadequate in situations where the operator has to remain inside the structure under treatment (fumigant action) while using hand-held CO2 pressure guns and portable fogging and misting equipment, or applying dichlorvos by watering can or paintbrush.
The review found there is insufficient information to predict the extent of operator exposure during indoor crack and crevice treatments. Consequently, these uses of Dichlorvos are or will no longer be supported on revised product labels.
The situations in which operator exposure can be constrained within acceptable limits, by use of appropriate personal protective equipment, are fumigation treatments where Dichlorvos is discharged from pressure cylinders into buildings, sealed plant fumigation chambers or other enclosed spaces using fixed installations, fumigation of the airspace within sealable silos, bins or other storage containers, where Dichlorvos is discharged from manually released pressure cylinders by an operator remaining outside the space under treatment, fumigation of machinery and eradication of insect nests in outdoor settings.
However, although operator safety can be assured in these situations, there is a hazard to persons re-occupying treated buildings, even after ventilation. An experimental study has shown that workers re-entering treated industrial buildings will be exposed to toxicologically unacceptable airborne concentrations of dichlorvos for 3 days after application. A 4-day re-entry interval would be supportable, but compliance would be impractical in many situations. Therefore, Dichlorvos should NOT be applied within industrial or similar buildings which are to be reoccupied within four days of treatment. By contrast, Dichlorvos is significantly less persistent when applied in glass houses, and a re-entry interval of 4 hours after ventilation is suitable for these and similar structures.
The continued use of dichlorvos for treatment of empty grain silos is supported. No labelling restraints are necessary with respect to residues for this use. Refer to part extract from the review 5.2.4 below and the review itself for full information regarding future use changes for silos.
5.2.4 Interim use and additional data requirements
By applying risk mitigation measures to bring modelled OHS risk down to acceptable levels, the APVMA will allow for grain fumigation uses to continue during an interim use period. These measures will include additional label restraints, developed in consultation with the Australian stored grains industry and the OCSEH (Office of Chemical Safety & Environmental Health). The APVMA will allow interim use for a period sufficiently long enough to generate occupational exposure data to establish future safe use parameters.
The APVMA concluded that, by applying strict restraints and control measures to mitigate OHS risk, it could support uses essential to the grain industry for an interim period. Additional label restraints will be required to bring OHS risks down to acceptable levels. If the data supplied from manufacturers and researchers is found to be acceptable in terms of OHS risk, the APVMA will allow ongoing use of Dichlorvos in the grains industry. Refer to 5.2.5 for further important changes.
Dichlorvos is volatile from dry surfaces i.e. that it readily changes from a liquid state to a gas state. It is also readily soluble in water and hence only very slightly to moderately volatile from moist surfaces or water.
- It is not to be sprayed on surfaces where water runoff to water bodies, drains etc. can occur.
- It is highly toxic to birds
- It is toxic to fish and mammals
Registration of a number of Dichlorvos products has lapsed, not been renewed or withdrawn from the market. To see lists of these products and the remaining registered products go to APVMA website and select products under review (www.apvma.gov.au/products/review/a_z_reviews.php) and select Dichlorvos from the list.
Normally a two-year sales period is allowed after a product registration lapses, meaning old labelled products can be used up within the two years.
Changes affecting the Pest Control Industry
The APVMA Review has recommended significant changes to Dichlorvos labels, particularly for the directions of use and personal protective equipment which will affect its use in the pest control industry.
These changes are detailed in sections 5.2.3, 5.2.4 and 5.2.5 of the Review.
Beside the many agricultural use changes, it has recommended changes that include the deletion of many current uses due to the likelihood of toxicologically unacceptable levels of operator exposure.
The following activities (current uses) are recommended to be deleted:
- Uses involving surface spray, space spray, crack and crevice treatment
- Outdoor and indoor application by fogging or misting
- Mechanical application to grain
- Pressurised gas in enclosed spaces where the operator must enter the space under fumigation
- Portable fogging or misting equipment in enclosed spaces where the operator must enter the space under fumigation
- Application by watering can, the wooden board method or by paintbrush
- Broad-acre application to avocados
It is recommended that new statements will be included on the labels as follows:
- DO NOT use in food cupboards or food storage and food preparation areas
- DO NOT use this product in buildings (other than glasshouses and similar plant production facilities) that are likely to be re-occupied within four days of fumigation
- DO NOT contaminate streams, rivers or waterways with the chemical or used containers or rinsate (the rinse from cleaning your tank out)
Labels will also specify a re-entry period of 4 hours for glasshouses and similar plant production facilities and; amend safety directions to bring them in line with entries in the current First Aid Instructions and Safety Directions Handbook.
Label instructions will be amended for all products in regard to risks to birds, terrestrial and aquatic species from the use of Dichlorvos. Include warnings under 'Protection of Wildlife, Fish, Crustaceans and Environment' alerting users to the toxicity of Dichlorvos to aquatic organisms and stressing the need to avoid contamination of streams, rivers or other water bodies with dichlorvos by any means which might arise with the use of a particular product, including direct spray, spray drift, used containers, and spray mix residues or rinsate.
We hope the above will alert users of Dichlorvos to these important changes that will almost certainly occur, some products already have new labels with current APVMA approval numbers. Make sure the products you use are used legally. Check with the manufacturers of the product for the period deregistered products can be used up. Lists of products are given in Tables 19, 20, 21 & 22 of the Review.