Effects of pesticide use
The offsite effects of pesticides are of increasing concern to growers, planners, resource managers, consumers, regulators and industry.
Some pesticides are mobile and can reach surface and groundwaters through spray drifts, runoff, soil erosion and leaching with unintended impacts on non-target organisms. The cumulative effect of pesticides and other contaminants on biodiversity and human health is a particularly important issue.
Assessment of the risks to environment is difficult, especially when dealing with complicated physical, chemical and biological interactions of pesticides at the catchment scale. However, risk indicators can play an important role is identifying pesticides as well as scenarios associated with their usage that may present relatively higher or lower risk.
In 1996 a CSIRO team, including Dr Rai Kookana, Dr Ray Correll and Ms Ros Miller, found a way of calculating a pesticide's mobility and likely effect on water quality taking into account its toxicity, chemical properties, application rate and frequency, and factoring in local site conditions along with seasonal and soil variables.
They created a software application - Pesticide Impact Rating Index (PIRI) - by cleverly integrating the various factors that determine the impact of pesticides in the environment:
- the value of the asset (for example an adjacent water resource that may be threatened)
- the sources of threat (for example a certain pesticide load) to the asset
- the transport pathways (for example spray drift) by which the threat is released.
Information about pesticide properties, soil and environmental conditions, and site- specific factors is built into the process.
PIRI combines information about properties and toxicity of pesticides to aquatic organisms with information about their environmental fate and behaviour under chosen soil and environmental conditions, to predict and minimise the potential off-site movement of pesticides to adjacent waterways.
The science of PIRI was published in the peer reviewed international journal Water, Air and Soil Pollution: Focus in 2005.
Widespread application of the software
Since its first release, PIRI has been used by regulators and natural resource managers in Western Australia, Tasmania and Victoria.
International interest from UN agencies FAO/IAEA resulted in PIRI being used in a Food and Environment program project which involved 12 countries across Asia, South America and Africa.
An independent evaluation of risk indicators by the University of Zurich in Switzerland included PIRI in a group of three rated favourably, out of seven, for use in less developed countries.
The now defunct Land & Water Australia commissioned an independent evaluation of PIRI in June 2005 which calculated its net benefit as A$13.6 million, with a 37:1 return on investment.
The evaluation concluded the benefits of PIRI included:
- savings in pesticide usage and monitoring costs
- greater understanding of pesticide toxicity
- better choice of pesticides for particular sites and better land management practices
- reduced impacts on aquatic health and biodiversity.