Toxicity Testing

Toxicity TestingToxicity Testingandand

Environmental Risk AssessmentEnvironmental Risk Assessment

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

Point source discharge into a fly ash collection pond

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))

Algae toxicity test, EPA laboratory, Cincinnati, Ohio

Photo by R. Grippo

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?

Ecotoxicological testingEcotoxicological testing

Single species Multi-species Mesocosm

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

Variability Detectability

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

Who will watch the watchers?Who will watch the watchers?