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Lethal Dose LD50

Lethal Dose LD50. APES – Chapter 8. T oxicology is the study of the adverse physico -chemical effects of chemical, physical or biological agents on living organisms and the ecosystem. Includes the prevention and treatment of disease.

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Lethal Dose LD50

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  1. Lethal Dose LD50 APES – Chapter 8

  2. Toxicologyis the study of the adverse physico-chemical effects of chemical, physical or biological agents on living organisms and the ecosystem. • Includes the prevention and treatment of disease. • Toxicology, ancient in practice, came to be known simplistically as the science of poisons. Toxicology

  3. “The dose makes the poison.”– almost everything is toxic at some level. (According to Swiss scientist Paracelsus 500 years ago.) • How do you determine if a drug or chemical is safe to use…lab testing! Laboratory Investigations to Measure Toxicity

  4. Animal Studies • Populations of lab animals usually rodents • Measured doses under controlled conditions • Takes two to five years • Costs $200,000 to $2,000,000 per substance • Newer methods Laboratory Investigations

  5. Newer methods • Bacteria (Transgenic experiments) • Cell and tissue culture • Appropriate tissue • Stem cells • Chicken egg membrane Laboratory Investigations

  6. Love Canal Part I • Love Canal Part 2 Biohazards / Superfund Site

  7. Epidemiologyis the study of distribution and determinants of health problems in specified populations. a) applying the learned information to control thehealth problems. It is the scientific method of problem solving disease—epidemiologists, laboratory scientists, statisticians, physicians and other health care providers, and public health. Epidemiology

  8. Determine severity of health concern…is it an epidemic or an outbreak? • Identify the cause. • Identify if it is a small cluster or larger population • Geographic location(s) Criteria used to measure concerns

  9. Epidemic--refers to a contagious, infectious or viral illness that spreads to many people in one geographic region that occurs in excess of the numbers of cases that would usually be expected. • Pandemicrefers to a contagious, infectious or viral illness that spreads, and may include millions of people in many areas across the globe, according to the World Health Organization's description.

  10. Laboratory testing on different drugs or chemicals are done by looking at a dose response curve. • To determine the toxicity of a chemical, look at dose to which 50% of the test population is sensitive. Which dose is right?

  11. 100 75 Percentage of population killed by a given dose 50 25 LD 50 0 8 10 6 14 12 2 4 16 Dose (hypothetical units) In case of lethal dose (LD), this is called LD50. Fig. 8.16, p. 171

  12. LD50 =individual dose required to kill 50% of test population (e.g., rats, fish, mice, cockroaches). • Standard to compare relative toxicities of chemicals. • The lower the LD50 dose, the more toxic the pesticide. • A pesticide with an LD50 value of 10 mg/kg is 10 times more toxic than a pesticide with an LD50 of 100 mg/kg LD-50 Dose Response

  13. Different sensitivities to toxin to specific populations. Number of individuals affected Very Sensitive Majority of Average Population low Sensitivity Low Sensitivity 0 20 40 60 80 Dose (hypothetical units) Fig. 8.15, p. 171

  14. Validity Challenged • Human physiology is different • Different species react different to same toxins • Mice die with aspirin • Species can be selected depending on physiological area • Pigs circulatory very similar to humans Laboratory Investigations

  15. ToxicityLD50Lethal DoseExamples Super < 0.01 less than 1 drop dioxin, botulism mushrooms Extreme <5 less than 7 drops heroin, nicotine Very 5-50 7 drops to 1 tsp. morphine, codeine Toxic 50-500 1 tsp. DDT, H2SO4, Caffeine Moderate 500-5K 1 oz.-1 pt. aspirin, wood alcohol Slightly 5K-15K 1 pt. ethyl alcohol, soaps Non-Toxic >15K >1qt. water, table sugar (LD50 measured in mg/kg of body weight) Toxicity

  16. Why so little is known of toxicity • Only 10% of at least 75,000 commercial chemicals have been screened • ~2% determined to be carcinogen, teratogen or mutagen • >1000 new synthetic chemicals added per year • >99.5% of US commercial chemicals are NOT regulated

  17. Nonlinear dose-response Linear dose-response Effect Effect Dose Dose No threshold Threshold Nonlinear dose-response Linear dose-response Dose-Response Curves Threshold level Fig. 16.6, p. 401

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