A retrospective analysis of the added value of 1-year dog studies in pesticide human health risk assessments

Abstract

The 1-year dog toxicity study is no longer required by certain pesticide regulatory jurisdictions, including the United States and the European Union. Health Canada’s Pest Management Regulatory Agency (PMRA) examined its current requirement for this study to determine if it could be refined or eliminated. A retrospective analysis was conducted to examine the impact of the 1-year dog study on human health risk assessment. The Acceptable Daily Intake (ADI), a measure of the amount of a pesticide in food that can be ingested on a daily basis over a lifetime without an appreciable health risk, was the metric for this analysis. For 143 pesticides evaluated by the PMRA between 2008 and 2015, the supporting toxicology databases were examined to determine if other toxicology studies were protective of the findings in the 1-year dog study. When this criterion was not met, further investigation was undertaken to determine the potential impact of not having the 1-year dog study. For most of the pesticides, effect levels in the 1-year dog study were not substantially different from those in other toxicology studies, when considering factors such as dose-spacing and known experimental variability. The results of this analysis suggest that absence of the 1-year dog study would have minimal impact on the assessment of human health risk. Therefore, Health Canada’s PMRA has removed the routine requirement for the 1-year dog study from its pesticide data requirements.

Keywords:

• Dog toxicity studies
• retrospective analysis
• pesticides
• human health risk assessment
• study duration
• data requirement

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Erratum

Acknowledgments

The authors gratefully acknowledge the extensive comments received from Dr. Elizabeth Mendez of the US EPA and Cheryl Chaffey and Dr. Alisa Vespa from Health Canada, as well as those from six independent reviewers selected by the Editor and who were anonymous to the authors. These comments were helpful in revising the manuscript.

Declaration of interest

All of the authors are employees of Health Canada’s PMRA. The authors carried out this work as a normal part of their official government duties. This work summarizes the analysis that was used in support of Health Canada’s decision to no longer routinely require testing for a 1-year duration in the dog, as published in the PMRA’s update to its data requirements guidance document (PMRA 2016). The authors also have sole responsibility for the writing and content of this paper.