1 / 31

Toxicity Testing

Toxicity Testing. and Environmental Risk Assessment. Dimensions of the Toxic Chemical Problem. Chemical entities 4-10 million Developed annually ~ 6000 In commerce ~ 65,000 In common use ~ 6,000 Regulated water 129 air 25 .

carys
Download Presentation

Toxicity Testing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Toxicity Testing and Environmental Risk Assessment

  2. Dimensions of the Toxic Chemical Problem • Chemical entities 4-10 million • Developed annually ~6000 • In commerce ~65,000 • In common use ~6,000 • Regulated water 129 air 25

  3. Toxicology – Historical Perspective • Human (Mammalian) toxicology • White Rat • Rabbit • Dog/Cat • Computer simulation?

  4. Toxicology – Historical Perspective • Environmental toxicology • Before 1950  chemical data superior to biological data • Needed methods to indicate level of biological effects of chemicals

  5. 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

  6. Point source discharge into a fly ash collection pond

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

  8. 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

  9. 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)

  10. Algae toxicity test, EPA laboratory, Cincinnati, Ohio Photo by R. Grippo

  11. Survival Growth Reproduction Behavior (avoidance) Abundance Diversity Biomass Processing rate Endpoints ToxicologyEcology

  12. Environmental Toxicology • Dose - response (effect) relationships • Ecological Dose-Response relationships

  13. Mechanism of ToxicityTargets and Effects • Cell membranes • Enzymes • Lipids • Protein synthesis • Microsomes • Regulatory processes (hormones) • Carbohydrate metabolism

  14. 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

  15. 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

  16. Ecologically realistic testing • Greater sensitivity? • Improved extrapolation? • Replicability and reproducibility? • Variability and detectability”? • Suitable endpoints?

  17. Ecotoxicological testing Single species Multi-species Mesocosm

  18. LOEC = lowest observable test concentration The lowest test concentration that is significantly different from control

  19. NOEC = no observable effect concentration The highest test concentration that is not significantly different from control

  20. MATC = geometric mean of NOEC and LOEC • Often referred to as the chronic value ____________ • MATC = √NOEC * LOEC

  21. 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

  22. Variability Detectability

  23. Need to be careful! • False negative  system insensitive? • False positive  unconfirmed predictions?

  24. 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

  25. Who will watch the watchers?

More Related