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TOX 715 ENVIRONMENTAL TOXICOLOGY

TOX 715 ENVIRONMENTAL TOXICOLOGY. Chronic Toxicity. Chronic Toxicity. Toxicity resulting from long-term exposure to a toxicant, generally at exposure levels below those that elicit acute toxicity. Chronic Toxicity.

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TOX 715 ENVIRONMENTAL TOXICOLOGY

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  1. TOX 715ENVIRONMENTAL TOXICOLOGY Chronic Toxicity

  2. Chronic Toxicity • Toxicity resulting from long-term exposure to a toxicant, generally at exposure levels below those that elicit acute toxicity

  3. Chronic Toxicity • Toxicity resulting from long-term exposure to a toxicant, generally at exposure levels below those that elicit acute toxicity • effects are generally sublethal

  4. Chronic toxicity may occur when... • a toxicant is environmentally persistent and bioaccumulates

  5. Chronic toxicity may occur when... • a toxicant is environmentally persistent and bioaccumulates • a toxicant is continuously introduced into the environment

  6. Chronic toxicity may occur when... • a toxicant is environmentally persistent and bioaccumulates • a toxicant is continuously introduced into the environment • a toxicant persists within an organism

  7. MATC • Maximum Acceptable Toxicant Concentration • The highest theoretical concentration of a chemical that will not elicit chronic toxicity, based upon a direct evaluation of the toxicity of the chemical. • >NOEC<LOEC

  8. Concentration (mg/L)Survival (%)# offspring/female 100 50 0 50 100 35 25 100 50 12 80 235 6 100 250 0 90 243

  9. Time requirements to assess chronic toxicity • Mammalian: 6 months -2 years

  10. Time requirements to assess chronic toxicity • Mammalian: 6 months -2 years • Birds: ~6 months

  11. Time requirements to assess chronic toxicity • Mammalian: 6 months -2 years • Birds: ~6 months • Fish: 6 months - 2 years

  12. Time requirements to assess chronic toxicity • Mammalian: 6 months -2 years • Birds: ~6 months • Fish: 6 months - 2 years • Invertebrates: 1- 6 weeks

  13. Endpoints • Those that can affect population sustainability

  14. Utility of the Application Factor • Reduces the need to perform expensive or difficult chronic toxicity tests

  15. Utility of the Application Factor • Reduces the need to perform expensive or difficult chronic toxicity tests • Assess the effects of different environmental variables on chronic toxicity

  16. Utility of the Application Factor • Reduces the need to perform expensive or difficult chronic toxicity tests • Assess the effects of different environmental variables on chronic toxicity • Estimate chronic toxicity to species that cannot be directly evaluated

  17. What does the MATC tell us about the chronic toxicity of a chemical?

  18. Chemical: A B CV (mg/L) 0.005 1.0 Which chemical is more chronically toxic?

  19. Chemical: A B CV (mg/L) 0.005 1.0 Which chemical is more chronically toxic? LC50 (mg/L) 0.009 10,000 Which chemical is more chronically toxic?

  20. The Acute:Chronic Ratio • ACR = LC50/MATC • A measure of the chronic toxicity of a chemical

  21. ToxicantACR Metals 50-200 Organochlorine insecticides 50-100 PCBs ~50 Organophosphate insecticides ~10 Organic solvents ~10

  22. Chronic toxicity should be judged by... • the magnitude of the ACR

  23. Chronic toxicity should be judged by... • the magnitude of the ACR • mechanistic information on the cause of acute and chronic toxicity

  24. Chronic toxicity should be judged by... • the magnitude of the ACR • mechanistic information on the cause of acute and chronic toxicity • the slopes of the acute and chronic concentration-response lines

  25. BEWARE! Estimates of chronic toxicity using abridged (short-term) assay methods

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