Evaluating Variation in Terrestrial Plant Toxicity Tests
The following report aims to determine the natural variability of the response endpoints (i.e. emergence, plant length, plant weight) for these studies. This project involved the development and design of two databases in MS Access, the selection of control data from existing studies, an analysis of the among and within laboratory variability in response measures, and a trend analysis for environmental conditions.
The findings supported the currently accepted coefficient of variation (CV) of 20% used by the U.S. EPA. All seedling emergence studies in all laboratories had average CV values of less than 40% and laboratories who were responsible for conducting a majority of the studies exhibited CV values less than 20%. Similar patterns were observed in the length data from the vegetative vigor studies. The weight data presented variation that was often greater than the expected 20% even for the most frequently tested species. The most data was available for corn and soybean plants and these species were also the least variable.
The historical value of a 20% coefficient of valuation seems to be, on average, an acceptable value for the terrestrial plant toxicity tests used for pesticide registration. The data of this report indicates particular species, specifically corn and soybean, tend to have CV values closer to 10%. The addition of more data and a more sophisticated analysis into the underlying causes of variation could reveal a lower CV across all species.
School Location:USA - North Carolina
Source Type:Master's Thesis
Keywords:terrestrial plants variation pesticides toxicity tests
Date of Publication:04/25/2008