Agricultural pesticides contribute to agricultural productivity but also pose potential risks to human health and the environment. The risks vary greatly depending on pesticide's inherent toxicity (or hazard) and exposure. Exposure to a pesticide depends on the way it is applied and its mobility and persistence in the environment.
Pesticide use by farmers depends on a multitude of factors, such as climatic conditions, the composition and variety of crops, pest and disease pressures, farm incomes, pesticide cost/crop price ratios, pesticide policies and management practices. Pesticide indicators are potentially a useful tool to help policy makers monitor and evaluate policies and also provide information concerning human and environmental pesticide risks.
All OECD countries have a regulatory system that assesses pesticides prior to their release for sale, to ensure they do not pose unacceptable risks to the environment and public above nationally agreed thresholds. A number of countries have also set targets to reduce the total quantity of agricultural pesticides used over a given time period. In addition, policies to reduce risk, and other measures like pesticide taxes, are being used in some countries, to reduce the environmental and health impacts of pesticide use.
OECD is developing two kinds of indicators. One shows pesticide use trends over time based on sales and/or use data in terms of active ingredients. The other indicator tracks trends in pesticide risks by combining information on pesticide hazard and exposure with pesticide use data and information on the conditions that might affect risks. Pesticide use indicators are simpler, but because the policies of OECD member countries aim ultimately to reduce risks, it is important to develop the more complex but highly policy relevant indicators of risk trends.
Overall the trend in pesticide use over the last decade has remained constant or declined in most OECD countries, although for a few countries use has increased. The reduction can be explained partly by changing crop prices, greater efficiency of pesticide use as a result of improvements in pest management practices and technology, and government policies aimed at both improving pest management practices, and in some cases targeting a reduction in pesticide use.
There is evidence to suggest an increasing efficiency in the use of pesticides for some OECD countries, with the volume of crop production over the past 10-12 years increasing more rapidly than pesticide use. For a considerable number of countries, however, annual changes in pesticides use appear to be closely correlated with fluctuations in annual crop production trends.
The close correlation between trends in pesticide use and risks estimated by a few OECD countries, over a period of 10 or more years suggests that pesticide risks to human health and the environment can be reduced by reducing the use of particular chemicals. Caution is required, however, in linking trends in pesticide use with changes in risks. This is because a change in pesticide use is not always equivalent to a change in risks, especially with the development of more targeted pesticides, and because different pesticides pose different types and levels of risks.
Preliminary results of OECD work on pesticide risk indicators for the aquatic environment show that different indicator methods can produce different pesticide risk trends, even when using the same data on pesticide risks and use.