Refinement of aquatic exposure estimates in environmental run-off assessments for pesticides: dryland cropping regions

This consultation closed on 21 September 2015

Consultation period

21 July 2015 to 21 September 2015


The current methodology used for environmental risk assessments of pesticides utilises a deterministic approach which does not take into account temporal and spatial variables that occur in the real-world environment in which pesticides are used; this is outlined in Part 7 (Environment) of APVMA’s data guidelines.

Publicly-available Australian environmental datasets can be used to conduct regulatory environmental risk assessments which better reflect actual environmental conditions. Such an approach has now been developed for assessing pesticide runoff risk to waterways using real world-data sets for stream flow in dryland cropping regions of Australia.

Proposed new framework for environmental exposure assessment

The document Refinement of aquatic exposure estimates in Australian pesticide environmental assessments: use of real world data to characterise receiving waters in Australia's dryland cropping regions—run off risk assessment sets out a framework and methodology using rainfall, land slope and river flow data from dryland cropping regions of Australia. This is to help refine estimates of exposure of aquatic environments to pesticide run-off in these regions.

The approach is designed to move away from the current default-based deterministic assessment to a more evidence-based approach through use of long-term stream flow and rainfall data. The process still applies the Department of the Environment in-house run-off model accepted by the APVMA. However, this approach aims to increase its flexibility within the run-off risk assessment.

For assessing run-off risk, this new framework proposes several steps. The first step still relies on a standard default receiving water body, as is applied in current assessments. The second step considers the probability of rainfall events that may result in an unacceptable risk in the standard water body (as used in the current deterministic method), with a particular focus on chemical persistence. This allows identification of regions where a run-off risk assessment is best focused, and identification of those regions where based on the probability of rainfall, a run-off risk is unlikely. The third (and final) step involves the in-stream assessment through application of the long-term rainfall and stream flow data.

This final step applies several conservative assumptions to ensure adequate environmental protection is maintained.  These assumptions include:-

a) Application of the pesticide to 20% of the catchment area

b) The full treated area contributes to run-off

c) Daily rainfall is assumed to fall over a period of one hour.

Development of the framework and method

To develop the flow data for streams in dryland cropping regions of Australia, long-term daily data from between 570 and 580 stream monitoring stations in Queensland, New South Wales, Victoria and Western Australia were assessed.  Cumulative frequency distributions for receiving water concentrations resulting from run-off were developed from these data, allowing more quantitative assessments of exposure, and hence risk.

Several case studies are included in the paper to demonstrate the application of the data libraries and the run-off risk assessment framework.

The future

Depending on the outcomes of this pilot project which focuses on the development of the method for dryland cropping regions of Australia, the APVMA may investigate options for extending the method to other agricultural areas where tropical/sub-tropical, temperate horticultural and forestry plantations are grown.

Call for public comment

Comment is sought on the technical aspects of the proposed method and the data libraries. Once the methodology has been considered by interested stakeholders, the APVMA will review responses from the consultation and make appropriate method amendments.  The APVMA will then provide further advice on its formal introduction as a regulatory tool for assessing pesticide run-off to aquatic areas in dryland cropping regions of Australia.

Please send your written submission by email, post or fax to:

Australian Pesticides and Veterinary Medicines Authority
PO Box 6182
Kingston ACT 2604

Phone: +61 2 6210 4701
Fax: +61 2 6210 4721

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