Environmental Health and Toxicology

1. Environmental Health and Toxicology Chapter 22

2. Outline: • Environmental Health Hazards • Infectious Organisms • Emergent Diseases • Antibiotics and Pesticide Resistance • Toxic Chemicals • Distribution and Fate of Toxins • Minimizing Toxic Effects • Measuring Toxicity • Risk Assessment • Public Policy

3. ENVIRONMENTAL HEALTH HAZARDS • 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. Infectious Organisms • For most of human history, the greatest health threats have been pathogenic organisms. • Infectious diseases are still responsible for about 33% of all disease-related deaths. • Majority of deaths in poorer countries with poor nutrition, sanitation, and vaccination programs.

5. Morbidity and Quality of Life • Death rates do not tell everything about burden of disease. • Total economic and social consequences of diseases are difficult to obtain. • Disability-Adjusted Life Year (DALY) combines premature deaths and loss of healthy life resulting from illness or disability.

6. Disability-Adjusted Life Year • WHO reports communicable diseases are responsible for nearly half of all 1.2 billion DALY’s lost each year. • About 90% of all DALY losses occur in developing world where one-tenth of all health care dollars are spent. • Malnutrition exacerbates many diseases.

7. Emergent Diseases • An emergent disease is one never known before, or has been absent for at least 20 years. • An important factor in the spread of many diseases is speed and frequency of modern travel. • Foot and Mouth Disease • Ebola

8. Emerging Ecological Diseases • Domestic animals and wildlife also experience sudden and widespread epidemics. • Distemper (Seals) • Chronic Wasting Disease (Deer and Elk) • Transmissible Spongiform Encephalopathies • Black Band Disease (Coral)

9. In the News…. • http://www.npr.org/templates/story/story.php?storyId=4586823&sourceCode=RSS

10. Infectious Disease Outbreaks

11. Antibiotic and Pesticide Resistance • 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 and Pesticide Resistance

13. Antibiotic Use • 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.

14. Vivian Vermillion • Vivian picked up a strain of antibiotic resistant E. coli at the Vet Hospital • This strain is resistant to six antibiotics!!!

15. Antibacterial Mustard Introduced by French’s • ROCHESTER, NY—In response to increasing American demand for tangier, more hygienic meals, condiment giant French's has introduced a new antibacterial mustard.

16. Toxic Chemicals • Dangerous chemicals are divided into two broad categories: • Hazardous - Dangerous • Flammable, explosive, irritant, sensitizer, acid, caustic. • Toxic - Poisonous • Can be general or very specific. Often harmful even in dilute concentrations.

17. 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.

18. Toxic Chemicals • Sick Building Syndrome • Headaches, allergies, and chronic fatigue caused by poorly ventilated indoor air contaminated by molds, carbon monoxide, nitrogen oxides, and other toxic chemicals. • Worker absenteeism and reduced productivity. • EPA estimates $60 billion annual loss.

19. Toxic Chemicals • Neurotoxins - Special class of metabolic poisons that specifically attack nerve cells. • Different types act in different ways. • Heavy Metals kill nerve cells. • Anestheticsand Chlorinated Hydrocarbons disrupt nerve cell membranes. • Organophosphates and Carbamates inhibit signal transmission between nerve cells.

20. Toxic Chemicals • Mutagens - Agents that damage or alter genetic material. • Radiation • Teratogens - Specifically cause abnormalities during embryonic growth and development. • Alcohol - Fetal Alcohol Syndrome • Carcinogens - Substances that cause cancer. • Cigarette smoke

21. US Age-Adjusted Cancer Death Rates

22. Endocrine Hormone Disrupters • Chemicals that disrupt normal endocrine hormone functions. • Hormones are chemicals released in blood by glands to regulate development and function of tissues and organs elsewhere in the body. • Environmental Estrogens and Androgens

23. Diet • Strong correlation between cardiovascular disease and the amount of salt and animal fat in an individual’s diet. • Highly-processed foods, fat, and smoke-cured, high nitrate meats appear to be associated with cancer. • Nearly 2/3 of all Americans are considered overweight.

24. DISTRIBUTION AND FATE OF TOXINS • Solubility - Chemicals are divided into two major groups: • Dissolve more readily in water. • Dissolve more readily in oil. • Water-soluble compounds move rapidly through the environment, and have ready access to most human cells. • Oil-soluble molecules generally need a carrier to move through the environment.

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. Sensitivity and Developmental Stage • Many factors help determine reaction of an individual to a given dose. • Age • Sex • Body Weight • Nutritional / Immunological Status • Repair Mechanisms

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. • (DDT)

28. Bioaccumulation

29. Chemical Interactions • Antagonistic Reaction - One material interferes with the effects, or stimulates the breakdown, of other chemicals. • Aluminum and phosphate ions form solid • Additive Reaction - Effects of each chemical are added to one another. • Xenoestrogens + estrogens • Synergistic Reaction - One substance multiplies the effect of the other. • Nitrate ion and phosphate ion

30. MECHANISMS FOR MINIMIZING TOXIC EFFECTS • 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 • Effects of waste products and environmental toxins reduced by eliminating via excretion. • Breathing • Kidneys • Urine

32. MEASURING TOXICITY • 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 (dies).

33. LD50

34. Population Sensitivity Variations

35. Acute vs. Chronic 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.

36. RISK ASSESSMENT • 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.

37. 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 in 1 million is acceptable risk for environmental hazards.

39. ESTABLISHING PUBLIC POLICY • Biggest problem in making regulatory decisions is that we are usually exposed to many sources of harm, often unwillingly. • May not be reasonable to demand protection from every potentially harmful contaminant in our environment, no matter how small the risk.

40. ESTABLISHING PUBLIC POLICY • In setting standards for environmental toxins, need to consider: • Combined effects of different exposures. • Individual sensitivities within population. • Effects of chronic and acute exposures.

41. Food for Thought

42. From the Star - Tribune

43. Summary: • Environmental Health Hazards • Infectious Organisms • Emergent Diseases • Antibiotics and Pesticide Resistance • Toxic Chemicals • Distribution and Fate of Toxins • Minimizing Toxic Effects • Measuring Toxicity • Risk Assessment • Public Policy