tox 715 environmental toxicology
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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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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
slide7
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
slide8

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 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
slide18

Chemical: A B

CV (mg/L) 0.005 1.0

Which chemical is more chronically toxic?

slide19

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?

the acute chronic ratio
The Acute:Chronic Ratio
  • ACR = LC50/MATC
  • A measure of the chronic toxicity of a chemical
slide23

ToxicantACR

Metals 50-200

Organochlorine insecticides 50-100

PCBs ~50

Organophosphate insecticides ~10

Organic solvents ~10

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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