Tox 715 environmental toxicology
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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

TOX 715ENVIRONMENTAL TOXICOLOGY

Chronic Toxicity


Chronic toxicity
Chronic Toxicity

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


Chronic toxicity1
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


Chronic toxicity may occur when
Chronic toxicity may occur when...

  • a toxicant is environmentally persistent and bioaccumulates


Chronic toxicity may occur when1
Chronic toxicity may occur when...

  • a toxicant is environmentally persistent and bioaccumulates

  • a toxicant is continuously introduced into the environment


Chronic toxicity may occur when2
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


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


Concentration (mg/L)Survival (%)# offspring/female

100 50 0

50 100 35

25 100 50

12 80 235

6 100 250

0 90 243


Time requirements to assess chronic toxicity
Time requirements to assess chronic toxicity

  • Mammalian: 6 months -2 years


Time requirements to assess chronic toxicity1
Time requirements to assess chronic toxicity

  • Mammalian: 6 months -2 years

  • Birds: ~6 months


Time requirements to assess chronic toxicity2
Time requirements to assess chronic toxicity

  • Mammalian: 6 months -2 years

  • Birds: ~6 months

  • Fish: 6 months - 2 years


Time requirements to assess chronic toxicity3
Time requirements to assess chronic toxicity

  • Mammalian: 6 months -2 years

  • Birds: ~6 months

  • Fish: 6 months - 2 years

  • Invertebrates: 1- 6 weeks


Endpoints
Endpoints

  • Those that can affect population sustainability


Utility of the application factor
Utility of the Application Factor

  • Reduces the need to perform expensive or difficult chronic toxicity tests


Utility of the application factor1
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


Utility of the application factor2
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



Chemical: A B chemical?

CV (mg/L) 0.005 1.0

Which chemical is more chronically toxic?


Chemical: A B chemical?

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?


The acute chronic ratio
The Acute:Chronic Ratio chemical?

  • ACR = LC50/MATC

  • A measure of the chronic toxicity of a chemical


Toxicant chemical?ACR

Metals 50-200

Organochlorine insecticides 50-100

PCBs ~50

Organophosphate insecticides ~10

Organic solvents ~10


Chronic toxicity should be judged by
Chronic toxicity should be judged by... chemical?

  • the magnitude of the ACR


Chronic toxicity should be judged by1
Chronic toxicity should be judged by... chemical?

  • the magnitude of the ACR

  • mechanistic information on the cause of acute and chronic toxicity


Chronic toxicity should be judged by2
Chronic toxicity should be judged by... chemical?

  • 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


Beware

BEWARE! chemical?

Estimates of chronic toxicity using abridged (short-term) assay methods


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