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Unit 8: Pollution: module 4.53 toxicity and LD50

FR4e reference: https://elab.hpa.edu/apes/texts/fr4e/unit%208%20water%20pollution.pdf

Bozeman Science: 

https://elab.local/apes/videos/bozeman_science/Health%20Impacts%20of%20Pollution.mp4

https://elab.hpa.edu/apes/videos/bozeman_science/Health%20Impacts%20of%20Pollution.mp4

Module 53: LD50: lethal dose to 50% of the population

  • Dose-response curve: can be bad (e.g. toxins) or good (e.g. antibiotics)
  • acute=sudden
  • chronic=long term
  • when using animals or organisms as study, mortality is the metric (% dead) sorry...

Screen Shot 2023-03-28 at 5.42.14 PM.png
Screen Shot 2023-03-28 at 5.42.14 PM.png

  • Look carefully: this is not linear (rarely are) and it shows that at a certain dose (x axis) 50% of the organisms are dead
  • This is known as LD50, or lethal dose for 50% of the population
  • There is another metric, the ED50, or effective dose for 50% of the population for non-lethal impacts (often used to describe effectiveness of drugs)
  • NOEL means no observed effect level-under lab conditions with present sensors we cannot determine any impact
  • NOEL is dangerous, as we don't have very sensitive gear for many toxins

TOSCA: 
  • Toxic Substances Control Act-regulates levels of chemicals (except food, cosmetics, pesticides)...also an opera
  • Rat studies: x/10 then x/10 again, but still assumes similar metabolism
  • See West Va. study on sleep aids in aged-made them psychotic: liver and kidneys less effective at clearing drugs
  • Also: not based on weight, but should be (they do it for horses and dogs...)

Environmental hazard: anything causing harm
Risk assessment is science, but psychology is important: smokers will not drive, drivers without seatbelts afraid to fly...
Screen Shot 2023-03-28 at 5.50.05 PM.png
Screen Shot 2023-03-28 at 5.50.05 PM.png

Risk assessment: 
Probability of exposure x Probability of harm
Think of sharks, lightning, driving without seatbelts, flying...

Two approaches to regulating drugs and chemicals:
  • Innocent until proven guilty: businesses like this
  • Tobacco industry used this tactic for decades: "sure smokers get cancer, but not from smoking
  • Precautionary: test before release, better for society

Stockholm convention of 2001: 
Dirty dozen: PCB, certain pesticides, DDT, PFAS
General overview for your review:

The dirty dozen: click on each and notice the structure
  1. aldrin: insecticide
  2. chlordane: insecticide
  3. DDT: silent spring!
  4. Dieldrin: termites
  5. Endrin: insecticide
  6. Heptachlor: ant killer, found in mother's milk on Oahu, 1980's, used "green chop" from pineapple to feed dairy cows (!)
  7. Hexachlorobenzene: fungicide
  8. Mirex: fire ants
  9. Toxaphene: mites on animals
  10. PCB: poly chlorinated biphenyls: insulators, electrical
  11. PCDD: burning medical waste
  12. PCDF: burning plastic waste




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