1. The Fate and Effect of Glyphosate on Amphibians Evan Hallas Kate Johannesen Matt Berg An Ecological Risk Assessment

2. Approach Review studies on the transport of glyphosate into aquatic ecosystems and its effects on amphibians Review studies on the transport of glyphosate into aquatic ecosystems and its effects on amphibians Analyze based on location (lab vs. field), methods, and whether or not there was a surfactant in the glyphosate tested. Analyze based on location (lab vs. field), methods, and whether or not there was a surfactant in the glyphosate tested. Examine source and validity of data Examine source and validity of data

3. Why Study Glyphosate? Argument exists over the toxicity of the substance Argument exists over the toxicity of the substance Different environmental factors expected to effect toxicity Different environmental factors expected to effect toxicity Necessity for reevaluation of EPA toxicity classification Necessity for reevaluation of EPA toxicity classification

4. What Is Glyphosate? World’s top selling herbicide World’s top selling herbicide Released by the Monsanto Company in 1974 (in Roundup) Released by the Monsanto Company in 1974 (in Roundup) Use has tripled since 1997 Use has tripled since 1997

5. How it Works Inhibits the shikimate enzyme pathway Inhibits the shikimate enzyme pathway Distributed with a surfactant Distributed with a surfactant Imitates glycine Imitates glycine

6. EPA Toxicity Classification Glyphosate is currently classified as a Level III toxin, which means that it is only “slightly toxic” Glyphosate is currently classified as a Level III toxin, which means that it is only “slightly toxic” Registration eligibility decision completed 14 years ago Registration eligibility decision completed 14 years ago Patent law protects manufacturer from listing “inert” ingredients Patent law protects manufacturer from listing “inert” ingredients

7. The Fate of Glyphosate in Wetlands Unlikely for glyphosate to leach into groundwater due to surfactant Unlikely for glyphosate to leach into groundwater due to surfactant Contamination can occur by drift/overspray and direct application Contamination can occur by drift/overspray and direct application Actual concentrations observed are dependent on several factors including application rate, interception by target vegetation, water depth, amount of suspended solids, and type of water body. Actual concentrations observed are dependent on several factors including application rate, interception by target vegetation, water depth, amount of suspended solids, and type of water body.

8. Potential Concentrations (Giesy et. Al., 2000)

9. Studies on Glyphosate A limited amount of research has been done regarding the impacts of glyphosate on the environment and amphibians A limited amount of research has been done regarding the impacts of glyphosate on the environment and amphibians Most experiments have been completed in labs Most experiments have been completed in labs Experiments revealed that surfactant was the major toxin Experiments revealed that surfactant was the major toxin

10. Roundup® Lab Experiment Dr. Rick Relyea Tested Effects of Roundup® on six species of larval amphibians Dr. Rick Relyea Tested Effects of Roundup® on six species of larval amphibians Simulated ecosystems with caged predators Simulated ecosystems with caged predators Estimated LC50 values in mg of Active Ingredient (AI)/L for each species using regression analyses Estimated LC50 values in mg of Active Ingredient (AI)/L for each species using regression analyses (Relyea, 2005a)

12. Soil and Roundup® Effects Tested three different soil treatments: no soil, loam, and sand Tested three different soil treatments: no soil, loam, and sand Simulated a direct field overspray creating a concentration of 3.8mg AI/L Simulated a direct field overspray creating a concentration of 3.8mg AI/L Examined survival rates of tadpoles for three different species Examined survival rates of tadpoles for three different species (Reyea, 2005a)

13. Effects of Vision® on Forest Wetlands Vision® contains a POEA surfactant and was applied at concentrations of.29 – 14.3 mg A.I./L to separate enclosures Vision® contains a POEA surfactant and was applied at concentrations of.29 – 14.3 mg A.I./L to separate enclosures Results showed no statistically significant decrease in survival rates of larval amphibians at the levels that could be expected to be found in nature, 1.43 mg A.I./L Results showed no statistically significant decrease in survival rates of larval amphibians at the levels that could be expected to be found in nature, 1.43 mg A.I./L 96-hour LC50 ranged from 2.70 – 11.5 mg A.I./L depending on species and site 96-hour LC50 ranged from 2.70 – 11.5 mg A.I./L depending on species and site

14. Glyphosate vs. Surfactant Different formulations of glyphosate tested: glyphosate isopropylamine, Roundup® Herbicide, and Roundup® Bioactive Different formulations of glyphosate tested: glyphosate isopropylamine, Roundup® Herbicide, and Roundup® Bioactive Those with surfactants are most toxic Those with surfactants are most toxic Glyphosate isopropylamine toxin levels higher then expected to be found in natural settings Glyphosate isopropylamine toxin levels higher then expected to be found in natural settings

15. (Mann and Bidwell, 1999)

16. Other Factors University of Guelph study showed elevated toxicity with a higher pH University of Guelph study showed elevated toxicity with a higher pH Potential for ecosystems to decrease exposure to amphibians compared to lab testing Potential for ecosystems to decrease exposure to amphibians compared to lab testing Actual concentrations in natural ecosystems Actual concentrations in natural ecosystems Recommended use vs. actual use Recommended use vs. actual use

17. Conclusion More research is necessary More research is necessary Glyphosate is only toxic due to its use with a surfactant Glyphosate is only toxic due to its use with a surfactant Need for change in FIFRA regulations-inert ingredients must be included in risk analysis Need for change in FIFRA regulations-inert ingredients must be included in risk analysis