Evaluation of the Changes in Pesticide Risk – Executive Summary

The objective of this study was to analyse the changes in pesticide use and risk on agricultural crops in the Province in Ontario from 1983 to 2008. Pesticide risk was assessed using the Environmental Impact Quotient (EIQ) (Kovach et al. 1992) and a modified EIQ. The EIQ measures the potential risk of pesticides to humans and the environment, taking into account the following risk factors: chronic toxicity, dermal toxicity, plant surface half-life, soil half-life, mode of action and systemic absorption in plants, leaching potential, fish toxicity, run-off potential, bird toxicity, bee toxicity and beneficial arthropod toxicity. The modified EIQ uses a score for the plant surface half-life for post-emergent herbicides based on the half-life rather than assigning a standard value of "3". Risk scores were calculated for 234 pesticides using publicly available data sources, with preference to the most recent assessments from regulatory agencies such as the United States Environmental Protection Agency (US EPA), Pest Management Regulatory Agency (PMRA), California EPA and World Health Organization (WHO). Pesticide risk was calculated by multiplying the risk scores for individual pesticides by the amount of pesticide used on each crop in each survey year. The changes in pesticide use and risk were expressed as a percentage of increase or decrease compared to the 1983 values. The 1983 pesticide use survey data was used as a baseline or benchmark year to assess the reduction in pesticide use attributable to the Food Systems 2002 program; a program with an objective to reduce pesticide use on agricultural crops in the Province of Ontario by 50% by the year 2002. This goal was achieved by 2003. The 2008 pesticide use survey data was analysed to measure the success of maintaining the Food Systems 2002 program goal.

Pesticide use, excluding growth regulators and pesticides used in greenhouses, was 40% lower in 2008 than in 1983, but was substantially higher than in 2003 when pesticide use was 52% lower than in 1983 (McGee et al. 2004). In 2003 and 2008 respectively, average crop yield (tonnes per hectare (ha)) of crops planted was 18% and 34% higher than in 1983. Average pesticide use per tonne of crop production was 54% lower in 2003 and 2008 than in 1983. The pesticide risk was 39% lower in 2008 than in 1983 using the EIQ, and 55% lower using the modified EIQ. The risk per kg of pesticide did not change appreciably from 1983 to 2008 using the EIQ, but there was a progressive decrease in the average risk per kg of pesticide using the modified EIQ, and it was 25% lower in 2008 than in 1983. This difference between the EIQ and the modified EIQ is primarily because of the lower score for plant surface half-life of glyphosate in the modified EIQ. Glyphosate accounted for 43% of the pesticide used in 2008. There was also a reduction in the number and amount of "high risk" pesticides using both scores.

The reductions in pesticide use and risk in 2008 were greatest on corn and tobacco, the crops with the highest pesticide use in 1983. Most of the reduction in pesticide use and risk on tobacco was because of the marked reduction in the area of tobacco. The area of corn was 22% lower in 2008 than in 1983, but mean application rate (kg of pesticide per ha) was 47% lower, and yield was 66% higher. Pesticide use and risk per tonne of production were 68-75% lower than in 1983. The area of soybeans in 2008 was 2.3 times the area in 1983 and crop yield was 47% higher, but pesticide use on soybeans was only 13% higher in 2008. The mean application rate was 52% lower in 2008 than in 1983, and pesticide use per tonne of production was 67% lower. Using the EIQ, the risk per ha was 26% lower, and the risk per tonne of production was 50% lower. However, using the modified EIQ, the risk per ha was 63% lower and the risk per tonne of production was 75% lower. The difference in the two scores was because of the differences in the scores for glyphosate, the most commonly used pesticide on soybeans in 2008.

Pesticide use on fruits and vegetables was only 5% lower in 2008 than in 1983, but the risk was 23% lower on fruits and 10% lower on vegetables because of the shift to lower risk pesticides. Pesticide use and risk were much higher in 2008 than in 2003. Most of the increase in pesticide use from 2003 to 2008 was because of the increased use of fungicides. 2008 was a year of above average rainfall in southern Ontario and the increased fungicide use prevented major crop losses on sensitive crops. In contrast, 2003 was a year of below average rainfall.

The reduction in the amount of pesticide used on agricultural crops in the Province of Ontario from 1983 to 2003 met the goal of the Food Systems 2002 program. However, pesticide use increased in 2008 compared to 2003. Despite the increased pesticide use in 2008, overall pesticide use and risk per tonne of production and per dollar of crop value did not differ from 2003. The risk per tonne of production was 53% lower using the EIQ and 65% lower using the modified EIQ. The reduction in pesticide risk was greater than the reduction in pesticide use because of the continued shift to lower risk pesticides.


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Author: OMAFRA Staff
Creation Date: April 2010
Last Reviewed: April 2010