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

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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


Tox 715 environmental toxicology

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


Tox 715 environmental toxicology

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

100500

5010035

2510050

1280235

6100250

090243


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


What does the matc tell us about the chronic toxicity of a chemical

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


Tox 715 environmental toxicology

Chemical:AB

CV (mg/L)0.0051.0

Which chemical is more chronically toxic?


Tox 715 environmental toxicology

Chemical:AB

CV (mg/L)0.0051.0

Which chemical is more chronically toxic?

LC50 (mg/L)0.00910,000

Which chemical is more chronically toxic?


The acute chronic ratio

The Acute:Chronic Ratio

  • ACR = LC50/MATC

  • A measure of the chronic toxicity of a chemical


Tox 715 environmental toxicology

ToxicantACR

Metals50-200

Organochlorine insecticides50-100

PCBs~50

Organophosphate insecticides~10

Organic solvents~10


Chronic toxicity should be judged by

Chronic toxicity should be judged by...

  • the magnitude of the ACR


Chronic toxicity should be judged by1

Chronic toxicity should be judged by...

  • 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...

  • 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!

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


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