Toxicity testing
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Toxicity Testing. and Environmental Risk Assessment. Dimensions of the Toxic Chemical Problem. Chemical entities4-10 million Developed annually ~ 6000 In commerce ~ 65,000 In common use ~ 6,000 Regulated water 129 air 25.

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Toxicity Testing

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Toxicity testing

Toxicity Testing

and

Environmental Risk Assessment


Dimensions of the toxic chemical problem

Dimensions of the Toxic Chemical Problem

  • Chemical entities4-10 million

  • Developed annually~6000

  • In commerce~65,000

  • In common use ~6,000

  • Regulated water 129 air 25


Toxicology historical perspective

Toxicology – Historical Perspective

  • Human (Mammalian) toxicology

  • White Rat

  • Rabbit

  • Dog/Cat

  • Computer simulation?


Toxicology historical perspective1

Toxicology – Historical Perspective

  • Environmental toxicology

    • Before 1950  chemical data superior to biological data

    • Needed methods to indicate level of biological effects of chemicals


Toxicity testing

History of Aquatic Toxicology

  • Prior to 1962 – pollution laws focused on sewage and nutrients

  • 1962 – Silent Spring published

    (pollution by synthetic

    organic chemicals)

  • Environmental regulations developed

    • Point-source pollution

    • Non-point source pollution


Toxicity testing

Point source discharge into a fly ash collection pond


Toxicity test

Toxicity test

The means by which the toxicity of a chemical or other test material is determined


Toxicity testing

Toxicity testing

Simultaneous chemical detection

and biological effects

Acute toxicity test

  • Short time frame exposure (96h)

  • “kill ‘em and count ‘em”

    Chronic toxicity test

  • Longer time frame exposure (1 week to 3 years)

  • reproduction, physiology, behavior, biochemistry

  • More ecologically relevant


Toxicity testing

Chronic toxicity testing

Reproduction

Fish – life cycle at least 3 to 6 months

(fathead minnow)

Invertebrates – complete life cycle in 3 days

(water flea -Ceriodaphnia dubia)


Toxicity testing

Algae toxicity test, EPA laboratory, Cincinnati, Ohio

Photo by R. Grippo


Endpoints

Survival

Growth

Reproduction

Behavior (avoidance)

Abundance

Diversity

Biomass

Processing rate

Endpoints

ToxicologyEcology


Environmental toxicology

Environmental Toxicology

  • Dose - response (effect) relationships

  • Ecological Dose-Response relationships


Mechanism of toxicity targets and effects

Mechanism of ToxicityTargets and Effects

  • Cell membranes

  • Enzymes

  • Lipids

  • Protein synthesis

  • Microsomes

  • Regulatory processes (hormones)

  • Carbohydrate metabolism


What is the purpose of bioassays

What is the purpose of bioassays?

  • Rank hazards

  • Set discharge limits  regulate hazards

  • Predict environmental consequences

  • Protect important species

    • Reason why rainbow trout tested (commercially and recreationally important)

    • Reason why Zn, Cl standards based on toxicity to rainbow trout even if stream has none


Criteria for selecting test organisms

Criteria for Selecting Test Organisms

  • Broad range of sensitivities

  • Widely available and abundant

  • Indigenous or representative

  • Recreationally, commercially, or ecologically important

  • Laboratory tolerant

  • Adequate background information


Ecologically realistic testing

Ecologically realistic testing

  • Greater sensitivity?

  • Improved extrapolation?

  • Replicability and reproducibility?

  • Variability and detectability”?

  • Suitable endpoints?


Ecotoxicological testing

Ecotoxicological testing

Single species Multi-species Mesocosm


Loec lowest observable test concentration

LOEC = lowest observable test concentration

The lowest test concentration that is significantly different from control


Noec no observable effect concentration

NOEC = no observable effect concentration

The highest test concentration that is not significantly different from control


Matc geometric mean of noec and loec

MATC = geometric mean of NOEC and LOEC

  • Often referred to as the chronic value

    ____________

  • MATC = √NOEC * LOEC


Hypothesis testing

Hypothesis testing

  • All types of testing need to hypothesis testing  what concentration is significant?

  • All bioassays try to determine level of toxicant which will or will not cause an effect


Toxicity testing

Variability Detectability


Need to be careful

Need to be careful!

  • False negative  system insensitive?

  • False positive  unconfirmed predictions?


Who said it

Who said it?

“The significant problems we face cannot be solved at the same level of thinking we were at when we created them”

- Albert Einstein


Toxicity testing

Who will watch the watchers?


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