Toxicology & risk

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Transcript of Toxicology & risk

  • 1.
    • Environmental Health, Risk and Toxicology

2. Alligators and Endocrine Disruptors at Lake Apopka, Florida

  • Biologist Louis Guillette found alligators with reproductive abnormalities in a Florida lake.
  • The lake had been contaminated with pesticides.
  • Research revealed that chemicals in the lake were disrupting the animals reproductive hormones.

3. Environmental health

  • Environmental health:
  • Assesses environmental factors that influence human health and quality of life.
  • Seeks to prevent adverse effects on human health and ecological systems.
  • Contains environmental toxicology within its scope.

4. Environmental health hazards

  • Synthetic and natural toxicants are only one type of environmental health threat.Others are:
    • Physical hazards(floods, blizzards, landslides, radon, UV exposure)
    • Chemical hazards(disinfectants, pesticides)
    • Biological hazards(viruses, bacterial infections)
    • Cultural or lifestyle hazards(drinking, smoking, bad diet, crime in neighborhood)

5. 6. Infectious disease

  • Incommunicableortransmissabledisease, a pathogen attacks a host,
    • either directly or through avector (e.g., mosquito that transfers a malaria parasite to hosts)
    • and the pathogen can be transmitted from one host to another.
  • Infectious disease causes 25% of deaths in the world
  • and nearly half of deaths in developing nations.

7. Infectious disease 2nd-leading cause of death worldwide 6 diseases account for 80% of infectious disease deaths 8. Many health hazards exist indoors

  • Substances in plastics and consumer products
  • Lead in paint and pipes
  • Radon
  • Asbestos
  • PBDE fire retardants

9. Toxicology

  • The study of poisonous substances and their effects on humans and other organisms
  • Toxicologists assess and compare toxic agents, ortoxicants , for theirtoxicity , the degree of harm a substance can inflict.
  • Analagous to apathogenicityorvirulenceof the biological hazards that spread infectious disease.
  • Environmental toxicologyfocuses on effects of chemical poisons released into the environment.

10. Environmental toxicology

  • Studies toxicants that come from or are discharged into the environment, and:
    • Health effects on humans
    • Effects on animals
    • Effects on ecosystems
  • Animals are studied:
    • For their own welfare
    • As canaries in a coal mine to warn of effectson humans

11. Synthetic chemicals are everywhere in our environment

  • Many thousands have been produced and released.
  • Some persist for long time periods or travel great distances.
  • 2002 USGS study:80% of U.S. streams contain up to 82 wastewater contaminants, include antibiotics, perfumes, detergents, drugs, steroids, disinfectants, etc.

12. Synthetic chemicals

  • Of the 100,000 synthetic chemicals on the market today, very few have been thoroughly tested for harmful effects.

13. Synthetic chemicals are numerous 14. Rise of synthetic chemicals

  • Widespread synthetic chemical production after WWII
  • People are largely unaware of the health risks of many toxicants.

The potent insecticide DDT was sprayed widely in public areas, even on people. 15. Silent Springand Rachel Carson

  • Carsons 1962 book alerted the public that DDT and other pesticides could be toxic to animals and people.
  • Further research led the EPA to ban DDT in 1973.
  • These developments were central to the modern environmental movement.

16. Types of toxicants

  • Carcinogens : cause cancer
  • Mutagens:cause mutations in DNA
  • Teratogens:cause birth defects
  • Allergens:cause unnecessary immune response
  • Neurotoxins:damage nervous system
  • Endocrine disruptors:interfere with hormones

17. Types of toxicants: Teratogens

  • The drug thalidomide, used to relieve nausea during pregnancy, turned out to be a potent teratogen, and caused thousands of birth defects before being banned in the 1960s .
  • Thalidomide baby Butch Lumpkin learned to overcome his deformed arms and fingers to become a professional tennis instructor.

18. Endocrine disruption

  • Some chemicals, once inside the bloodstream, can mimic hormones.
  • If molecules of the chemical bind to the sites intended for hormone binding, they cause an inappropriate response.
  • Thus these chemicalsdisrupttheendocrine(hormone)system .

19. Endocrine disruption

  • The hormone system is geared to working with tiny concentrations of hormones
  • so, it can respond to tiny concentrations of environmental contaminants.
  • Have chemicals in the environment acted as endocrine disruptors in humans?

20. Frogs, people, and atrazine

  • Frogs show reproductive abnormalities in response to small doses of the herbicide atrazine, researcher Tyrone Hayes has found.
  • Others suggest that atrazine may have effects on humans as well.
  • The fierce criticism from atrazines manufacturer reflects the high stakes in environmental toxicology.

21. Declining sperm counts?

  • A 1992 study summarized results of sperm count studies worldwide since 1938.Data showed a significant decrease in mens sperm counts over 50 years.

22. Testicular cancer

  • Others hypothesize that endocrine disruptors are behind the rise in testicular cancer in many nations.

23. Toxicants take many routes through the environment 24. Toxicants concentrate in water

  • Surface water and groundwater can accumulate toxicants.
  • Runoff from large areas of land drains into water bodies, becoming concentrated.
  • Toxicants in groundwater or surface water reservoirs used for drinking water pose potential risks to human health.

25. Airborne toxicants

  • Volatile chemicals can travel long distances on atmospheric currents.
  • PCBs are carried thousands of miles from developed nations of the temperate zone up to the Arctic, where they are found in tissues of polar bears and seals.

26. Transport to the Arctic: Global distillation 27. Persistence

  • Some chemicals are more stable than others, persisting for longer in the environment.
    • DDT and PCBs are persistent.
    • Bt toxin in GM crops is not persistent.
  • Temperature, moisture, sun exposure, etc., affect rate of degradation.
  • Most toxicants degrade into simplerbreakdown products .Some of these are also toxic.
    • (DDT breaks down to DDE, also toxic.)

28. Poisons accumulate in tissues

  • The body may excrete, degrade, or store toxicants.
  • Fat-soluble ones are stored.
    • DDT is persistent and fat soluble,
      • so builds up in tissues:bioaccumulation .
  • Bioaccumulated chemicals may be passed on to animals that eat the organismup the food chain

29. Poisons move up the food chain

  • At each trophic level, chemical concentration increases:biomagnification .
  • DDT concentrations increase from plankton to fish to fish-eating birds.

30. All toxicants are not synthetic

  • Although toxicology tends to focus on man-made chemicals, its important to keep in mind that there are plenty of natural toxicants.
  • Many are toxins produced by animals or plants for protection against predators and pathogens.

31. Studying effects of hazards

  • Toxicologists study effects in several major ways:
    • Wildlife toxicology studies
    • Human epidemiological studies
    • Dose-response studies in the lab

32. Wildlife toxicology

  • Determine causes of mortality in die-off events (e.g.,toxoplasma)
  • or
  • Test animals in the lab for response to toxicants
  • or
  • Correlate chemical presence and animal presence in the field

33. Human epidemiology

  • Human studies rely on:
  • Case history= observation and analysis of individual patients
  • Epidemiological studies= long-term, large-scale comparisons of different groups of people
  • Animal testing

34. Human epidemiology

  • Advantages: Realistic
  • All real-life factors included
  • Disadvantages: Statistically correlational only;does not prove c