Acute toxic hazard evaluations of glyphosate herbicide on terrestrial vertebrates of the oregon coast range
Goal, Scope and Background. The degree to which dose responses of model organisms (lab rodents) can adequately predict dose responses of free-ranging wild mammals or amphibians is unknown, and the relative sensitivity of such species to body loading of a toxicant such as glyphosate is seldom reported. For relative effects of dosage, we compare sensitivity of nine wild vertebrate species to effects of high doses of glyphosate in Swiss-Webster laboratory mice both by gavage and by intraperitoneal injection. We also evaluate sublethal effects of herbicide exposure on behavior and reproductive success of one mammal and one amphibian species
Comparisons of acute toxicity of glyphosate were made with intraperitoneal dosings of technical glyphosate isopropylamine salt to nine species of terrestrial vertebrates (five amphibians, four mammals) and compared with responses in Swiss-Webster laboratory mice. Animals collected from sites that had no recent herbicide application were allowed 7–14 days to equilibrate in captivity before treatment.
Median lethal dose ranged from 800 to 1,340 mg kg-1 in mammals, and 1,170 to >2,000 mg kg−1 in amphibians, with Oregon vole being the most sensitive. White lab mice were in the middle of the mammalian range. Tailed frog, at >2,000 mg kg−1 was the least sensitive. Calibration of IP sensitivity to oral administration by gavage indicated that roughly four times as much glyphosate must be administered to obtain a comparable estimate of lethality. Administration by gavage in highly concentrated solutions tended to cause physical injury, hence may prove less useful as a relative indicator of toxicity. When sublethal dosages were given to roughskin newts or chipmunks, mobility and use of cover appeared largely unaffected.
Direct toxic effects of spraying glyphosate under normal forest management seem unlikely for the nine species examined. Nor could we detect significant indirect effects of exposure on behavior and use of cover features in two species. There may be effects on other aspects of the field biology of these animals, such as reproductive rates, which we did not investigate. Recent field data indicate that changes in habitat quality following herbicide application can result in high reproductive activity in species associated with the grasses and forbs that proliferate following field applications.
When compared to field data on body burdens of wild mammals exposed after aerial application of glyphosate at maximum rates in forests, there seems to be a large margin of safety between dosages encountered and those causing either death or limitation of movement, foraging or shelter.
Recommendations and Perspectives
Margins of safety for small mammals and amphibians appear to be large under any probable exposure scenarios, however our results indicate high variability in responses among species. Uncertainty introduced into field studies from unknown sources of mortality (e.g, likely predation) must be considered when interpreting our results.
KeywordsAerial spray forestry glyphosate herbicides operational exposures Oregon coast range sublethal effects terrestrial vertebrates toxicology wildlife
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- Adam A, Marzuki A, Rahman HA, Aziz MA (1997): The oral and intratracheal toxicities of Roundup and its components to rats. Vet Human Toxicol 39, 147–151Google Scholar
- Anthony RG, Morrison ML (1985): Influence of glyphosate herbicide on small mammal populations in western Oregon. Northwest Sci 59, 159–168Google Scholar
- Brown ER (1985): Management of wildlife and fish habitats in forests of Western Oregon and Washington. Part 1, U.S. Forest Service Pacific Northwest Region R6-FWL 192Google Scholar
- Dixon WJ, Massey FJ, Jr (1969): Introduction to statistical analysis. Third ed., McGraw-Hill, NYGoogle Scholar
- FAO-WHO (1986): Glyphosate, pages 63–76 in Pesticide residues in food — 1986. Evaluations, Part II-toxicology. Joint Meeting on Pesticide Residues, FAO-WHO Meeting, RomeGoogle Scholar
- Giesy JP, Dobson S, Solomon KR (2000): Ecotoxicological risk assessment for Roundup herbicide. Reviews of Environmental Contamination and Toxicology 167, 35–120Google Scholar
- Glaser J, Bogart J (1997): Longterm effects of aerial sprayed glyphosate on percent deformities and reproductive success of Rana sylvatica. Abstracts of 18th Annual meeting of Society of Environ Toxicol Chem, San Francisco, CAGoogle Scholar
- Hudson RH, Tucker RK, Haegle MA (1984): Handbook of toxicity of pesticides to wildlife, 2nd ed. U.S. Dep. Interior Resour Publ 153, 90 ppGoogle Scholar
- Martinez TT, Long WC, Hiller R (1990): Comparison of the toxicology of the herbicide Roundup by oral and pulmonary routes of exposure. Proc West Pharmacol Soc 33, 193–197Google Scholar
- Morrison ML, Meslow EC (1984): Effects of the herbicide glyphosate on bird community structure, western Oregon. For Sci 30, 95–106Google Scholar
- Newton M, Dost FN (1984): Biological and physical effects of forest vegetation management. Final Report, Washington Department Natural Resources, Olympia, 423 ppGoogle Scholar
- Sullivan TP (1988): Non-target impacts of the herbicide glyphosate: A compendium of references and abstracts. Canadian Forestry Service, FRDA Report 013, 46 ppGoogle Scholar
- Takacs P, Martin PA, Struger J (2002): Pesticides in Ontario: A critical assessment of potential toxicity of agricultural products to wildlife, with consideration for endocrine disruption. Volume 2: Triazine herbicides, Glyphosate and Metolachlor. Technical Report Series No. 369, Canadian Wildlife Service, Ontario Region, Burlington, Ontario, CanadaGoogle Scholar
- U.S. Forest Service (1984): Pesticide background statements. Vol. 1. Herbicides. U.S. Dep Agric Handbook, No 633Google Scholar
- U.S. Forest Service (1988): Final Environmental Impact Statement for vegetation management in the Coastal Range/Piedmont. U.S. Dep Agric For Serv Management Bull, R8-MB-23Google Scholar