Grantee Research Project Results
1999 Progress Report: Improving Ecological Risk Assessment of Pesticides for Nontarget Terrestrial Vertebrates
EPA Grant Number: R825347Title: Improving Ecological Risk Assessment of Pesticides for Nontarget Terrestrial Vertebrates
Investigators: Wolff, Jerry O. , Edge, W. Daniel
Institution: Oregon State University
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1997 through December 31, 1999
Project Period Covered by this Report: January 1, 1998 through December 31, 1999
Project Amount: $358,354
RFA: Exploratory Research - Environmental Biology (1996) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Aquatic Ecosystems
Objective:
The objective of this research project is to field test assumptions of the quotient method. Specific objectives and hypotheses are:- Given an alternative, will animals move away from a spray zone into an unsprayed zone long enough to reduce exposure and risk? We hypothesize that mammals will not move from established home ranges to avoid contaminated vegetation.
- Will birds and mammals respond differently to equivalent concentrations of a pesticide applied as granular and flowable formulations? We hypothesize that a granular application will have a greater negative impact on birds and less of an impact on mammals than will a flowable application.
- What are the effects of environmental variables such as rainfall on exposure of a pesticide to mammals? We hypothesize that rainfall shortly after application will have a greater negative impact on voles than would dry conditions.
- What are the nonlethal effects of chronic exposure of a pesticide to small mammals? We have two contrasting hypotheses for this question. (1) We hypothesize that nonlethal physiological, behavioral, or genetic impairments may negatively affect reproduction, growth rates, and overall demography; or (2) chronic exposure may select against nonadaptive genotypes and eventually favor a resistant strain of animals.
Progress Summary:
Experiment 1. We have reported the results of this experiment in our previous report.Experiment 2. We used gray-tailed voles (Microtus canicaudus) and northern bobwhite quail (Colinus virginianus) as experimental model species to field test whether small mammals and birds respond differently to equivalent concentrations of a pesticide applied in granular and flowable formulations. In mid-May 1998, we placed voles into 15, 0.2-ha enclosures planted with a mixture of pasture grasses. In mid-July, we placed quail into the same enclosures with the voles. In late July, we applied the organophosphorus insecticide diazinon in five treatments: a control (all habitats sprayed with water), liquid formulation of diazinon at 0.55 kg/ha, liquid formulation of diazinon at 1.11 kg/ha, broadcast of granular diazinon at 1.11 kg/ha, and broadcast of granular diazinon at 2.22 kg/ha. The diazinon treatment in liquid and granular formulations did not depress population size or growth rate, or survival of voles. We found a significant difference in the survival rate of the quail between the controls and treatments; granular diazinon caused a measurable decline of quail survival, while the liquid application at an equivalent rate did not significantly affect quail survival. Our results suggest that ground-feeding birds are more susceptible to granular insecticides than to flowable applications, but voles were not susceptible to either formulation at the rate we used.
Experiment 3. The Quotient Method (QM), a pesticide risk assessment model used by the U.S. Environmental Protection Agency (EPA), assumes that the expected environment concentration of a contaminant is a function of application rate immediately after pesticide application. The QM does not take into account weather conditions (e.g., rainfall) at the time of spray. We used M. canicaudus as an experimental model species to field test this assumption of the QM by simulating a 0.25-cm rainfall. In June of 1999, we placed voles into 16, 0.2-ha enclosures planted with a mixture of pasture grasses. In early August, we applied 2.44 kg/ha of the insecticide Guthion? 2S (azinphos-methyl) in four treatments: a dry control, wet control ("rain"), dry treatment (sprayed with Guthion? 2S, no "rain"), and wet treatment (sprayed with Guthion? 2S and "rain" within 24 hours). We used four replicate populations for each treatment. Survival probabilities of male voles in dry treatment enclosures declined throughout the rest of the study following pesticide application, while survival probabilities displayed short-term increases in other treatments. Rainfall improved male survival and may have mitigated the adverse effects of Guthion? 2S. We also detected significant time by treatment interactions on population size and population growth rates of voles. Our results indicate that the Guthion? 2S treatment depressed population size and growth rate in the dry treatment; however, rainfall may have reduced the risk of Guthion? 2S to voles. Our study suggests that the QM is robust to the assumption that rainfall does not increase exposure of voles to Guthion? 2S in grasslands; however, the interaction between rainfall and Guthion? 2S application resulted in a deviation from the predicted risk.
Future Activities:
Experiment 4 will be conducted in the coming field season.Journal Articles on this Report : 7 Displayed | Download in RIS Format
Other project views: | All 17 publications | 10 publications in selected types | All 10 journal articles |
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Type | Citation | ||
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Caslin TM, Wolff JO. Individual and demographic responses of the gray-tailed vole to vinclozolin. Environmental Toxicology and Chemistry 1999;18(7):1529-1533. |
R825347 (1999) R825347 (Final) |
Exit Exit |
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Edge WD, Schauber EM. Factors affecting risk assessment of small mammals to pesticides. Environmental Toxicology and Chemistry 2000;19(11):2735-2741. |
R825347 (1999) R825347 (Final) |
Exit Exit |
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Schauber EM, Edge WD. Statistical power to detect main and interactive effects on the attributes of small-mammal populations. Canadian Journal of Zoology 1999;77(1):68-73. |
R825347 (1999) R825347 (Final) |
Exit Exit |
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Wang G, Wolff JO, Edge WD. Gray-tailed voles do not move to avoid exposure to the insecticide Guthion® 2S. Environmental Toxicology and Chemistry 1999;18(8):1824-1828. |
R825347 (1999) R825347 (Final) |
Exit Exit |
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Wang G, Edge W, Wolff JO. A field test of the quotient method for predicting risk to Microtus canicaudus in grasslands. Archives of Environmental Contamination and Toxicology 1999;36(2):207-212. |
R825347 (1999) R825347 (Final) |
Exit |
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Wang G, Edge WD, Wolff JO. Response of bobwhite quail and gray-tailed voles to granular and flowable diazinon applications. Environmental Toxicology and Chemistry 2001;20(2):406-11 |
R825347 (1999) |
Exit Exit |
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Wang G, Edge WD, Wolff JO. Demographic uncertainty in ecological risk assessments. Ecological Modelling 2001;136(1):95-102. |
R825347 (1999) R825347 (Final) |
Exit Exit Exit |
Supplemental Keywords:
agriculture, exposure, ecological effects, ecology, indicators, mammalian, modeling, Northwest, Oregon, toxics, zoology., RFA, Health, Scientific Discipline, Toxics, Ecosystem Protection/Environmental Exposure & Risk, Ecology, exploratory research environmental biology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, Chemistry, pesticides, Risk Assessments, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Biology, Ecological Indicators, risk assessment, ecological exposure, ecological risk assessment, pesticide exposure, terrestrial vertebrates, mutagenic properties, field experiments, quotient model, wildlife populations, chemical mixtures, ecological assessment, mitigating factors, toxic environmental contaminantsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.