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Chapter 8 - O'Neill PPoint
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Chapter 8 - O'Neill PPoint


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  • 1. Environmental Health and Toxicology
  • 2. Outline
    • Environmental Health
      • Infectious and Emergent Diseases
      • Antibiotics and Pesticide Resistance
    • Toxicology
    • Movement, Distribution, and Fate of Toxins
    • Minimizing Toxic Effects
    • Measuring Toxicity
    • Risk Assessment
    • Establishing Public Policy
    • Health
      • A state of complete physical, mental, and social well-being.
    • Disease
      • A deleterious change in the body’s condition in response to an environmental factor.
      • Diet and nutrition, infectious agents, toxic chemicals, physical factors, and psychological stress all play roles in morbidity (illness) and mortality (death).
  • 4. Environmental Health Risks
  • 5. Global Disease Burden
    • Disability-adjusted life years
      • (DALYs) - combine premature deaths and loss of healthy life resulting from illness or disability
    • Life expectancy has risen worldwide; chronic conditions are becoming a leading cause of disability and premature death.
      • By 2020, heart disease may become leading source of disability and disease worldwide.
  • 6. Recent Outbreaks of Infectious Diseases
  • 7. Infectious Diseases
    • Greatest health threats:
      • pathogenic organisms, accidents or violence.
      • Communicable diseases
        • responsible for about 1/3 of all disease-related deaths.
        • Majority in countries with poor nutrition, sanitation, and vaccination programs.
          • Malaria is a major disease in tropical areas.
  • 8. Emergent Diseases
    • An emergent disease:
        • never known before
        • been absent for at least 20 years.
      • The spread of many diseases
        • is due to the speed and frequency of modern travel
          • Ex. SARS
          • Ex. West Nile Virus
  • 9. Funding Health Care
    • Heaviest burden of illness borne by poorest people who cannot afford a healthy environment or adequate health care.
      • WHO estimates 90% of all disease burden occurs in developing countries where less than 10% of all health care dollars are spent.
        • Worldwide, only 2% of people with AIDS have access to modern medicines.
  • 10. Ecological Diseases
    • Domestic animals and wildlife also experience sudden and widespread epidemics.
      • Distemper in seals in western Europe.
      • Chronic Wasting Disease in deer and elk in North America
      • Sudden Oak Death Syndrome in California.
  • 11. Antibiotic and Pesticide Resistance
    • The problem with antibiotics and pesticides:
    • Protozoan parasite that causes malaria is now resistant to most antibiotics, while the mosquitoes that transmit it have developed resistance to many insecticides.
      • Short life spans.
        • Speeds up natural selection and evolution.
      • Human tendency to overuse pesticides and antibiotics.
  • 12. Antibiotic Use
    • Why is antibiotic use a problem?
      • At least half of the 100 million antibiotic doses prescribed in the US every year are unnecessary or are the wrong drug.
      • Many people do not finish full-course.
      • More than half of all antibiotics manufactured in the US are routinely fed to farm animals to stimulate weight gain.
  • 13. Antibiotic Resistance – How is it developed?
  • 14. Toxicology
    • Dangerous chemicals are divided into two broad categories:
      • Toxic - Poisonous
        • Can be general or very specific. Often harmful even in dilute concentrations.
      • Hazardous - Dangerous
        • Flammable, explosive, irritant, acid, caustic.
  • 15. Toxic Chemicals
    • Allergens
      • Substances that activate the immune system.
      • Antigens
        • Allergens that are recognized as foreign by white blood cells and stimulate the production of specific antibodies.
          • Other allergens act indirectly by binding to other materials so they become antigenic.
            • Sick Building Syndrome
  • 16. Toxic Chemicals
    • Endocrine Disrupters
      • Disrupt normal hormone functions
        • Thyroxine
          • Regulates cell metabolism
        • Insulin
          • regulates blood sugar levels
        • Adrenalin
          • response to stress; stimulates autonomic nerve action
        • Endorphins
          • reduce the sensation of pain and affect emotions
  • 17. Steroid Hormone Action Normal: Hormone carriers deliver molecules to cell surface. Intraceullur carriers deliver hormones to the nucleus; bind to and regulate expression of DNA.
  • 18. Toxic Chemicals
    • Neurotoxins
      • Metabolic poisons that specifically attack nerve cells.
      • Different types act in different ways.
        • Heavy Metals kill nerve cells.
        • Anesthetics and Chlorinated Hydrocarbons disrupt nerve cell membranes.
        • Organophosphates and Carbamates inhibit signal transmission between nerve cells.
  • 19. Toxic Chemicals
    • Mutagens
      • Agents that damage or alter genetic material.
        • Ex. Radiation
    • Teratogens
      • Specifically cause abnormalities during embryonic growth and development.
        • Alcohol - Fetal Alcohol Syndrome
    • Carcinogens
      • Substances that cause cancer.
        • Ex. Cigarette smoke
  • 20. Diet
    • Sixty-percent of all U.S. adults are now considered overweight.
      • Estimated 1 billion worldwide.
    • U.S. Centers for Disease Control warn one in three U.S. children are at risk of becoming diabetic.
    • Solubility
      • One of most important characteristics in determining the movement of a toxin.
    • Chemicals are divided into two major groups:
        • Those that dissolve more readily in water.
        • Those that dissolve more readily in oil.
      • What’s the difference in how they move?
        • Water soluble compounds move rapidly through the environment, and have ready access to most human cells.
  • 22. The movement and fate of chemicals in the environment.
  • 23. Exposure and Susceptibility
    • How and where do they affect us?
      • Airborne toxins generally cause more ill health than any other exposure.
        • Lining of lungs easily absorbs toxins.
      • Largest toxin exposure reported in industrial settings.
      • Condition of organism and timing of exposure also have strong influences on toxicity.
  • 24. Exposure Routes Exposure routes to toxic and hazardous environmental factors
  • 25. Bioaccumulation and Biomagnification
    • Cells have special mechanisms for: Bioaccumulation
      • Selective absorption and storage.
        • Dilute toxins in the environment can build to dangerous levels inside cells and tissues.
    • Biomagnification
      • Toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator at a higher trophic level.
  • 26. Bioaccumulation and Biomagnification
  • 27. Persistence
    • Some chemical compounds are very unstable and degrade rapidly under most conditions, thus their concentrations decline quickly after release.
    • Others are more persistent.
      • Stability can cause problems as toxic effects may be stored for long period of time and spread to unintended victims.
        • Example?
          • (DDT)
  • 28. Persistence
    • Persistent Organic Pollutants ( POP’s )
      • Polybrominated diphenyl ethers (PDBE)
      • Perfluorooctane sulfonate (PFOS) and Perfluorooctanic acid (PFOA).
      • Phthalates
      • Perchlorate
      • Bisphenol A (BPA)
      • Atrazine
  • 29. Chemical Interactions
    • Antagonistic Reaction :
      • One material interferes with the effects, or stimulates the breakdown, of other chemicals.
    • Additive Reaction
      • Effects of each chemical are added to one another.
    • Synergistic Reaction
      • One substance exacerbates the effect of the other.
    • Every material can be poisonous under certain conditions.
      • Most chemicals have a safe threshold under which their effects are insignificant.
    • Metabolic Degradation
      • In mammals, the liver is the primary site of detoxification of both natural and introduced poisons.
  • 31. Excretion and Repair
    • Effects of waste products and environmental toxins reduced by eliminating via excretion.
      • Breathing
      • Kidneys
        • Urine
    • Tissues and organs often have mechanisms for damage repair.
      • Any irritating agent can be potentially carcinogenic.
    • Animal Testing
      • Most commonly used and widely accepted toxicity test is to expose a population of laboratory animals to measured doses of specific toxins.
        • Sensitivity differences pose a problem.
          • Dose Response Curves
          • LD50 - Dose at which 50% of the test population is sensitive.
  • 33. Toxicity Ratings
    • Moderate toxin takes about (1) g/kg of body weight to produce a lethal dose.
      • Very toxic materials require about 10% of that amount.
        • Extremely toxic materials require 1% of that amount.
          • Supertoxic chemicals can be lethal in a dose of a few micrograms.
  • 34. Toxicity Ratings
    • Many carcinogens, mutagens, and teratogens are dangerous at levels far below their direct toxic effect because abnormal cell growth exerts a form of biological amplification.
  • 35. Acute versus Chronic Doses and Effects
    • Acute Effects
      • Caused by a single exposure and result in an immediate health problem.
    • Chronic Effects
      • Long-lasting. Can be result of single large dose or repeated smaller doses.
        • Very difficult to assess specific health effects due to other factors.
    • Risk
      • Possibility of suffering harm or loss.
    • Risk Assessment
      • Scientific process of estimating the threat that particular hazards pose to human health.
        • Risk Identification
        • Dose Response Assessment
        • Exposure Appraisal
        • Risk Characterization
  • 37.  
  • 38. Understanding Risks
    • Factors influencing risk perception:
      • Rating risks based on agendas.
      • Most people have trouble with statistics.
      • Personal experiences can be misleading.
      • We have an exaggerated view of our abilities to control our fate.
      • News media sensationalizes rare events.
      • Irrational fears lead to overestimation of certain dangers.
        • Fear of the unknown.
  • 39. Accepting Risks
    • Most people will tolerate a higher probability of occurrence of an event if the harm caused by that event is low.
      • Harm of greater severity is acceptable only at low levels of frequency.
        • EPA generally assumes 1 / 1 million is acceptable risk for environmental hazards.
    • It is difficult to separate the effects of multiple hazards and evaluate their risks accurately, especially when exposures are near the threshold of measurement and response.
      • May not be reasonable to mandate protection, no matter how small the risk, from every potentially harmful contaminant in our environment.
  • 41. CERCLA and RCRA
    • Remaining Slides are in reference to CERCLA and RCRA
  • 42. Hazardous Waste
    • Legally, hazardous waste is any discarded liquid or solid that contains substances known to be:
      • Fatal to humans or laboratory animals in low doses.
      • Toxic, carcinogenic, mutagenic, or teratogenic to humans or other life-forms.
      • Ignitable with a flash point less than 60 o C.
      • Explosive or highly reactive.
  • 43. Hazardous Waste Disposal
    • Federal Legislation
      • Resource Conservation and Recovery Act (RCRA) - 1976.
        • Comprehensive program requiring rigorous testing and management of toxic and hazardous substances.
          • Cradle to grave accounting.
  • 44. Federal Legislation
    • Comprehensive Environmental Response, Compensation and Liability Act (CERCLA).
      • Modified in 1984 by Superfund Amendments and Reauthorization Act.
        • Aimed at rapid containment, cleanup, or remediation of abandoned toxic waste sites.
          • Toxic Release Inventory - Requires 20,000 manufacturing facilities to report annually on releases of more than 300 toxic materials.
  • 45. Cradle to Grave
  • 46. CERCLA
    • Government does not have to prove anyone violated a law, or what role they played in a superfund site.
      • Liability under CERCLA is “strict, joint, and several”, meaning anyone associated with a site can be held responsible for the entire clean-up cost.
  • 47. Superfund Sites
    • EPA estimates 36,000 seriously contaminated sites in the U.S..
      • By 1997, 1,400 sites had been placed on the National Priority List for cleanup with with Superfund financing.
        • Superfund is a revolving pool designed to:
          • Provide immediate response to emergency situations posing imminent hazards.
          • Clean-up abandoned or inactive sites.
  • 48. Summary
    • Environmental Health
      • Infectious and Emergent Diseases
      • Antibiotics and Pesticide Resistance
    • Toxicology
    • Movement, Distribution, and Fate of Toxins
    • Minimizing Toxic Effects
    • Measuring Toxicity
    • Risk Assessment
    • Establishing Public Policy
  • 49.