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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. - PowerPoint PPT Presentation
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Dimensions of the Dimensions of the Toxic Chemical ProblemToxic Chemical Problem
Chemical entitiesChemical entities 4-10 million4-10 million
Developed annuallyDeveloped annually ~~60006000
In commerceIn commerce ~~65,00065,000
In common use In common use ~~6,0006,000
RegulatedRegulated water water 129 129 air air 25 25
Toxicology – Historical PerspectiveToxicology – Historical Perspective
Human (Mammalian) Human (Mammalian) toxicology toxicology
White RatWhite Rat
RabbitRabbit
Dog/CatDog/Cat
Computer simulation?Computer simulation?
Toxicology – Historical PerspectiveToxicology – Historical Perspective
Environmental toxicologyEnvironmental toxicology Before 1950 Before 1950 chemical data superior to chemical data superior to
biological databiological data
Needed methods to indicate level of biological Needed methods to indicate level of biological effects of chemicalseffects of chemicals
History of Aquatic ToxicologyHistory of Aquatic Toxicology
Prior to 1962 – pollution laws Prior to 1962 – pollution laws focused on sewage and nutrientsfocused on sewage and nutrients
1962 – Silent Spring published 1962 – Silent Spring published (pollution by synthetic (pollution by synthetic organic chemicals)organic chemicals)
Environmental regulations Environmental regulations developeddeveloped Point-source pollutionPoint-source pollution Non-point source pollutionNon-point source pollution
Toxicity testToxicity test
The means by which the toxicity of a The means by which the toxicity of a chemical or other test material is chemical or other test material is determineddetermined
Toxicity testingToxicity testing
Simultaneous chemical Simultaneous chemical detection detection
and biological effectsand biological effects
Acute toxicity test Acute toxicity test Short time frame exposure Short time frame exposure
(96h)(96h) ““kill ‘em and count ‘em”kill ‘em and count ‘em”
Chronic toxicity test Chronic toxicity test Longer time frame exposure Longer time frame exposure
(1 week to 3 years)(1 week to 3 years) reproduction, physiology, reproduction, physiology,
behavior, biochemistrybehavior, biochemistry More ecologically relevant More ecologically relevant
Chronic toxicity testingChronic toxicity testing
ReproductionReproductionFish – life cycle at least 3 Fish – life cycle at least 3
to 6 months to 6 months
(fathead minnow)(fathead minnow)
Invertebrates – complete Invertebrates – complete life cycle in 3 dayslife cycle in 3 days
(water flea -(water flea -Ceriodaphnia dubiaCeriodaphnia dubia))
EndpointsEndpoints
SurvivalSurvival
GrowthGrowth
ReproductionReproduction
Behavior (avoidance) Behavior (avoidance)
AbundanceAbundance
DiversityDiversity
BiomassBiomass
Processing rateProcessing rate
Toxicology Ecology
Environmental ToxicologyEnvironmental Toxicology
Dose - response (effect) relationshipsDose - response (effect) relationships
Ecological Dose-Response relationshipsEcological Dose-Response relationships
Mechanism of ToxicityMechanism of ToxicityTargets and EffectsTargets and Effects
Cell membranesCell membranes
EnzymesEnzymes
LipidsLipids
Protein synthesisProtein synthesis
MicrosomesMicrosomes
Regulatory processes (hormones)Regulatory processes (hormones)
Carbohydrate metabolismCarbohydrate metabolism
What is the purpose of bioassays?What is the purpose of bioassays?
Rank hazardsRank hazardsSet discharge limits Set discharge limits regulate hazards regulate hazardsPredict environmental consequencesPredict environmental consequencesProtect important speciesProtect important species Reason why rainbow trout tested Reason why rainbow trout tested
(commercially and recreationally important)(commercially and recreationally important) Reason why Zn, Cl standards based on Reason why Zn, Cl standards based on
toxicity to rainbow trout even if stream has toxicity to rainbow trout even if stream has nonenone
Criteria for Selecting Criteria for Selecting Test OrganismsTest Organisms
Broad range of sensitivitiesBroad range of sensitivities
Widely available and abundantWidely available and abundant
Indigenous or representativeIndigenous or representative
Recreationally, commercially, or Recreationally, commercially, or ecologically importantecologically important
Laboratory tolerantLaboratory tolerant
Adequate background informationAdequate background information
Ecologically realistic testingEcologically realistic testing
Greater sensitivity?Greater sensitivity?
Improved extrapolation?Improved extrapolation?
Replicability and reproducibility?Replicability and reproducibility?
Variability and detectability”?Variability and detectability”?
Suitable endpoints?Suitable endpoints?
LOEC = lowest observable test LOEC = lowest observable test concentrationconcentration
The lowest test concentration that is The lowest test concentration that is significantly different from controlsignificantly different from control
NOEC = no observable effect NOEC = no observable effect concentrationconcentration
The highest test concentration that is The highest test concentration that is notnot significantly different from controlsignificantly different from control
MATC = geometric mean of NOEC MATC = geometric mean of NOEC and LOECand LOEC
Often referred to as the Often referred to as the chronic valuechronic value
________________________
MATC = MATC = √NOEC * LOEC√NOEC * LOEC
Hypothesis testingHypothesis testing
All types of testing need to hypothesis All types of testing need to hypothesis testing testing what concentration is what concentration is significant?significant?
All bioassays try to determine level of All bioassays try to determine level of toxicant which will or will not cause an toxicant which will or will not cause an effecteffect
Need to be careful!Need to be careful!
False negative False negative system insensitive? system insensitive?
False positive False positive unconfirmed predictions? unconfirmed predictions?
Who said it?Who said it?
““The significant problems we face The significant problems we face cannot be solved at the same level of cannot be solved at the same level of thinking we were at when we created thinking we were at when we created them”them”
- Albert Einstein- Albert Einstein