Environmental Health

1. Environmental Health And Toxicology

2. Case Study

3. The study and practice of environmental health assess environmental factors that influence human health and quality of life Environmental health

4. 3 Categories of human health risk • Physical • Biological • Chemical

5. Leading Causes of Death - Global

6. Leading Health Risks - Global Low Income Countries High Income Countries

7. Environmental Risks: Physical • Occur naturally in the environment • Earthquakes • Fires • Floods and droughts • UV from the sun

8. Environmental Risks : Cultural • Result from where we live, socioeconomic status, occupation or behavioral choice • Choosing to smoke, poor diet, living in proximity to toxic waste are all cultural hazards • Not necessarily a choice

9. Environmental Risks: Chemical • Include synthetic chemicals such as pesticides and disinfectants • Include chemicals produced naturally by organisms

10. Environmental Risks: Chemical • Neurotoxins- chemicals that disrupt the nervous system (Hg, Pb) • Carcinogens- chemicals that cause cancer • Teratogens- chemicals that interfere with the normal development of embryos or fetuses (thalidomide)

11. Environmental Risks: Chemical • Allergens- chemicals that cause allergic reactions • Endocrine disruptors- chemicals that interfere with the normal functioning of hormones in an animal’s body (herbicides, nitrates, BPA) • Mutagensare chemicals that cause mutations in the DNA of organisms

12. Environmental Risks: Biological • A disease is any impaired function of the body with characteristic symptoms • Caused by virus, bacterium, fungus or other pathogen • If illness can be spread to other humans, then it is an infectious disease (e.g., malaria, cholera, flu)

13. Environmental Risks: Biological • Chronic diseases slowly impair the functioning of the body • Heart disease • Acute diseases rapidly impair the functioning of the body • Ebola

14. Risk Factors for Disease • Many major killers (cancer, heart disease, etc.)have genetic bases but are also influenced by environmental factors • Malnutrition can foster a wide variety of illnesses, • Poverty, poor hygiene, lifestyle choices, and lack of exercise also contribute

15. Risk Factors for Disease • Infectious disease involves a pathogen or an infection may occur through a vector • In order to predict and prevent infectious disease, experts deal with the interrelationships among technology, land use, and ecology

16. Risk Factors for Disease • Increased human mobility has made diseases a potential global epidemic. • Diseases like tuberculosis and malaria are becoming more drug resistant • Through habitat alteration and climate change, tropical diseases are moving further from the equator

17. Risk Factors for Disease • An epidemic occurs when a pathogen causes a rapid increase in disease • A pandemic occurs when an epidemic covers a large geographic region (continent)

18. Historically Important Diseases • Plague (bubonic plague, black death) caused by a bacterium carried by fleas • Malaria caused by a protist carried by mosquito • Tuberculosis is caused by a bacterium spread by person-to-person airborne

19. Emergent Diseases • HIV/AIDS (virus) • Ebola Hemorrhagic Fever (virus) • Mad Cow Disease (prion) • Bird Flu (H1N1 virus) made the ‘jump’ from bird to human • West Nile Virus also sourced from birds

21. Genetic Resistance to Antibiotics Is Increasing • Methicillin-resistant Staphylococcus aureus (MRSA) • Tuberculosis • Influenza or flu virus - #1 Killer • HIV - #2 Killer • Hepatitis B virus (HBV) - #3 Killer

22. Environmental Health Hazards Exist Indoors • Indoor environmental health threats include radon, lead poisoning, and asbestos • A recently recognized hazard is a group of chemicals known as polybrominated diphenyl ethers (PBDEs). These chemicals appear to affect thyroid hormones in animals, (banned in Europe)

23. Toxicology • Studies the effects of poisonous substances on humans and other organisms • A toxicant, or toxic agent, must be compared to other substances to determine the toxicity, or the degree of harm that it can inflict

24. Toxicology • With toxins, “the dose makes the poison” means that the quantity received is an important factor in the damage done • Environmental toxicology deals specifically with toxic substances that come from or are discharged into the environment, and includes the study of health effects on humans, other animals, and ecosystems

25. Toxic agents in the environment

26. Synthetic Chemicals • Thousands of synthetic chemicals have been manufactured and many have found their way into soil, air, and water. • Every one of us carries traces of numerous industrial chemicals in our bodies • Very few of these chemicals have been tested for harmful effects

27. Silent Spring • Began the public debate over pesticide use • Rachel Carson was a naturalist, author, and government scientist • She showed that DDT and artificial pesticides in general were hazardous to people, wildlife, and the environment

28. Silent Spring • The book was a bestseller and generated significant social changes in views and actions toward the environment • The United States manufactures and exports DDT to countries that still use it, especially for mosquito control

29. Endocrine Disruptors • First presented in 1996 in the book Our Stolen Future • Endocrine effects have been most widely found in animals • World-wide drops in sperm count (humans) may be attributed to this phenomenon

30. Endocrine Disruptors • Endocrine response is sensitive to minute quantities • Debate generated – herbicide mfr’s stand to lose a LOT of $ • Bisphenol-A (a plastic) is an estrogen mimic • Atrazine has also been linked

31. Toxins and Water • Water runoff carries toxins from large land areas & concentrates them in small volumes of surface waters (remember watersheds?) • Many chemicals are soluble in water, thus accessible to organisms; therefore… • Fish, frogs, stream invertebrates are good indicators

32. Persistence • DDT and PCBs have long persistence times, Bt toxin is short-lived • Breakdown products may be just as toxic or more toxic than parent compound • Many toxins are designed to persist

34. Synergy • Synergistic interactions- when two risks come together and cause more harm that one would. • For example, the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco

35. Toxicants and the Food Chain • Fat-soluble toxicants (DDT 7 DDE) are absorbed and stored in fatty tissue • Build-up of toxicants in animal tissue is bioaccumulation • Toxicants that bioaccumulate can be transferred to other organisms in the food chain, a process called biomagnification

37. Not All Toxicants Are Synthetic • Toxicants also exist naturally in the environment • Products of microbes, fungi, etc. are examples • Debate over risk

38. Studying Effects of hazards

39. Wildlife v. Human Studies • Wildlife studies use observations in the field and lab • Human studies rely on case histories, epidemiology, and animal testing • Epidemiological studies involve large-scale comparisons among groups of people

40. Wildlife v. Human Studies • Advantages of epidemiological studies: realism and ability to enable accurate predictions • Drawbacks include length of time it takes to obtain results and inability to address possible effects of new products • Manipulative experiments are then needed (animals tested)

41. Dose-Response Analysis • Standard method of testing lab animals • Dose is the amount of toxicant received • Response is the type or magnitude of negative effects; generally quantified • Once a dose-response curve is plotted, scientist calculate the toxicity (LD50) • LD50 is the amount of toxicant it takes to kill half the population of study animals

42. Dose-Response Analysis • ED50 is the level of toxicant at which 50% of the population to display harmful effects • Sometimes responses occur only above a certain dose (threshold dose) • Sometimes responses decrease with increase in dose (endocrine disruptors)

44. Dose-Response Analysis • Knowing the shape of the dose-response curve is important for predicting effects • For some toxicants, (endocrine disruptors) the U-shaped curve indicates impact at low concentrations • Individuals vary considerably in response to hazards

45. Type of Exposure • Acute exposure – high exposure for short duration • Chronic exposure – low exposure over long duration • Acute exposure is easier to recognize • Chronic is more common but difficult to detect and diagnose

46. Type of Exposure • Interactive impacts may result when toxicants are mixed • Synergistic effects: effects are more than the sum of the parts • Traditionally, environmental health has tackled effects of single hazards

47. Risk Assessment & management

48. Risk • Expressed in terms of probability • Exposure causes some probability of harm; a statistical chance that damage will result • Probability depends on the toxin, strength, frequency and duration of exposure, sensitivity

49. Risk • Risk assessment analyzes risk quantitatively • It involves the scientific study of toxicity and likely extent of exposure • Often performed by scientists associated with the industries • Risk management combines science and social factors • Usually handled by federal agencies; considered in light of economic, social, political needs and values