Chapter 8 ENVIRONMENTAL HEALTH & TOXICOLOGY

1. Chapter 8 ENVIRONMENTAL HEALTH & 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 HEALTH POLICY

3. ENVIRONMENTAL HEALTH • HEALTH - a state of complete physical, mental, and social well-being • DISEASE - an abnormal change in the body’s condition that impairs physical or psychological function, disrupting HOMEOSTASIS • Diet and nutrition, infectious agents, toxic chemicals, genetics, trauma and psychological stress all play roles in MORBIDITY (illness) and MORTALITY (death).

4. ENVIRONMENTAL HEALTH RISKS

5. ENVIRONMENTAL HEALTH RISKS • PATHOGENS - INFECTIOUS AGENTS – bacteria, fungus, virus, parasite, protozoa, etc • TRAUMA – accidents • POLLUTION – air, water, noise, etc • RADIATION – UV, nuclear waste • TOXINS – smoking, metals like mercury & lead, chemical exposure from pesticides, herbicides, cleaning solution, etc.

6. Categories of Human Health Risk • The categories of health risk: • PHYSICAL – cause injury or loss of life (natural disaster, UV radiation, rock thrown at your head) • BIOLOGICAL – involved diseases (causes most deaths) • CHEMICAL – exposure to natural or synthetic chemicals (pesticides, pharmaceuticals, heavy metals)

7. Categories of Human Health Risk • Types of diseases • INFECTIOUS DISEASES are caused by pathogens, which include viruses, bacteria, fungi, protests, worms (transmitted by contact…COMMUNICABLE) • CHRONIC DISEASES slowly impair the functioning of a body (long lasting and recurrent) (heart disease, cancer) • ACUTE DISEASESrapidly impair bodily functions (flu, stroke) • Chronic much higher in developing countries due to poor sanitation, unsafe water, malnutrition, etc

8. GLOBAL DISEASE BURDEN • Life expectancy is increasing as infant mortality decreases. • Disability-adjusted life years (DALYs) – a tool that measures the effects of a disease on the population. DALY’s takes into account ALL effects of a disease. Not just the number of people who die from it. • Chronic conditions account for 60% of premature deaths and 50% of diseases and are becoming more prevalent. • By 2020, heart disease may become leading source of disability and disease worldwide. Global cancer rates will increase by 50%.

9. GLOBAL DISEASE BURDEN • DIABETES is on the increase. One-third of children born in North America today will develop diabetes in their lifetime due to poor diet and little exercise. • WHO projects that PSYCHOLOGICAL CONDITIONS could increase their share of the global disease burden from 10% currently to 15%. • DEPRESSION will be the second largest cause of all years lived with disability. • TOBACCO RELATED LUNG DISEASES are increasing. Biggest single cause of death worldwide.

10. CAUSES OF GLOBAL DISEASE BURDEN

11. COMMON VECTORS & DISEASES • VECTOR – the mode of transport for a pathogenic organism • INSECTS: • MOSQUITOES (malaria, dengue, yellow fever) • FLIES (sleeping sickness, typhoid, cholera) • TICKS (Lyme, Rocky Mt Spotted Fever) • WATER BORNE DISEASES: diarrheas, Hepatitis A, typhoid, cholera • VIRUSES: Hepatitis, HIV, measles, small pox • PROTOZOANS: malaria, giardia, trypanosomiasis • WORMS: tapeworm, flukes, schistosomiasis, elephantatiasis • RODENTS, BIRDS, etc. can also carry pathogens

12. INFECTIOUS DISEASES KILL PEOPLE • When a pathogen causes a rapid increase in disease, we call it an EPIDEMIC • When it occurs over a large geographic area, we call it a PANDEMIC • Transferred through spit/sneezing, contaminated foods/objects, vectors • Antibiotics are over prescribed and pathogens becoming resistant making “stronger” bacteria

13. INFECTIOUS DISEASES • Communicable diseases are still responsible for about 1/3 of all disease-related deaths. • Majority in countries with poor nutrition, sanitation, and vaccination • Malaria is a major disease in tropical areas. Two million people die each year. • Better nutrition, clean water, improved sanitation and inoculation of children could eliminate most of the deaths.

14. HISTORICAL DISEASES • PLAGUE caused by bacteria carried by fleas • MALARIA is caused by protists found in mosquitoes • TUBERCULOSIS is a highly contagious disease caused by bacteria that attacks the lungs • FLU - Greatest loss of life in a single year from a pathogen was in 1918 when the flu epidemic killed 50 to 100 million people worldwide. Today we are concerned that bird flu might cause an even larger outbreak.

15. EMERGENT DISEASES • An EMERGENT DISEASE is one never known before, or one which has been absent for at least 20 years. • Growing human populations push into remote areas where they encounter pathogens. • Air travel makes it possible to spread emergent diseases around the globe quickly. • West Nile virus (spread by mosquitoes) was introduced into North America in 1999, and is now found everywhere in the lower 48 states.

16. EMERGENT INFECTIOUS DISEASES • HIV - HUMAN IMMUNODEFICIENCY SYNDROME / Acquired Immune Deficiency Syndrome (AIDS) – came from chimps. Weakens immune system • EBOLA comes from primates. Fever, internal bleeding. No pandemic, but death within two weeks • MAD COW DISEASE – pathogen that damages cow’s nervous system. Can have same affect on humans (attack brain) • BIRD FLU – Small number infects now, but future worse • WEST NILE spread by mosquitoes • SARS (severe acute respiratory syndrome)

17. RECENT OUTBREAKS

18. CONSERVATION MEDICINE • ECOLOGICAL DISEASES - ANIMAL EPIDEMICS • A viral hemorrhagic disease is killing fish in the Great Lakes; introduced through ballast. • California sea lions have herpes 1 virus spread to them from human sewage. • Mad Cow and Deer wasting Disease are spread by prions from animal to animal • Sudden oak death syndrome is killing oak, redwoods, Douglas fir trees. Fungus imported on nursery stock.

19. CONSERVATION MEDICINE • CONSERVATION MEDICINE - attempts to understand how environmental changes threaten the health of humans and natural communities • ZOONOTIC ILLNESS – diseases normally found in animals that can be spread to humans (Anthrax, Rabies, Lyme, Plague, West Nile, Tuberculosis, Brucellosis)

20. ANTIBIOTIC AND PESTICIDE RESISTANCE • WHAT CAUSES RESISTANCE? • Natural selection and the ability of organisms to evolve rapidly • Human tendency to overuse pesticides and antibiotics • IE: Protozoan parasite that causes malaria is now resistant to most antibiotics, while the mosquitoes that transmit it have developed resistance to many insecticides. And, Global Warming is widening the range of these insects.

21. ANTIBIOTIC USE • At least half of the 100 million antibiotic doses prescribed in the U.S. every year are unnecessary or are the wrong drug. • Many people do not finish the full-course. Allowing resistant bacteria to multiply. • More than half of all antibiotics manufactured in the U.S. are routinely fed to farm animals to stimulate weight gain. Excreted in urine and feces, they find their way into surface water.

22. ANTIBIOTIC RESISTANCE

23. 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. • Raising our investment in health care would boost the world economy, reduce the spread of pathogens, and reduce population growth since parents whose children survive have fewer offspring.

25. TOXICOLOGY • TOXICOLOGY is the study of poisons and their effects on living systems. • 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 • ECOTOXICOLOGY deals with the interactions, transformation, fate, and effects of natural and synthetic chemicals in the biosphere.

26. TOXICOLOGY CHEMICALS OF CONCERN 7 CATEGORIES REMEMBER: The level of harmfulness depends on dose, frequency, genetic make up of those exposed, and health of those exposed • 1. IMMUNE SYSTEM DEPRESSANTS - pollutants that depress the immune system • 2. ENDOCRINE DISRUPTERS - disrupt normal hormone functions (DDT, plastics) • cause low sperm count, breast cancer • Environmental estrogens - environmental contaminants which cause reproductive problems in animals even at very low doses

27. 3. NEUROTOXINS - metabolic poisons that specifically attack nerve cells, cause organ failure (insecticides, lead, mercury). 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.

28. 4. MUTAGENS - Agents that damage or alter genetic material. Can lead to birth defects or tumors. (chloroform, ethylene oxide, benzene, lead, and vinyl chloride) 5. TERATOGENS - specifically cause abnormalities during embryonic growth and development (nicotine, alcohol, drugs) • Alcohol - Fetal Alcohol Syndrome 6. CARCINOGENS - chemicals that cause cancer. Cause cell damage and causes bad cells to grow. Damage genetic material (radon, arsenic, PCB’s, asbestos)

29. ABNORMAL CELL GROWTH aka Tumors • Many carcinogens, teratogens, and mutagens are dangerous at levels far below their direct toxic effect because abnormal cell growth exerts a form of biological amplification. One cell mutated by a toxin can form a tumor that can potentially kill an individual. Remember... cells grow exponentially! BENIGN – a tumor that grows slowly and doesn’t interfere with normal cell functions MALIGNANT - a growth that grows rapidly and interferes with normal cell functions

30. 7. ALLERGENS - substances that causes high response from immune system (mold, pollen, dander, peanuts) • ANTIGENS - substances 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 (SBS) is a phenomenon affecting building occupants who claim to experience acute health and comfort effects that appear to be linked to time spent in a building, but where no specific illness or cause can be identified.

31. MOVEMENT, DISTRIBUTION, AND FATE OF TOXINS

32. MOVEMENT, DISTRIBUTION, AND FATE OF TOXINS

33. MOVEMENT, DISTRIBUTION, AND FATE OF TOXINS • SOLUBILITY - one of most important characteristics in determining the movement and storage of a toxin • Chemicals are divided into two major groups: • WATER SOLUBLE (dissolve in water) compounds move rapidly through the environment and have access to cells. • FAT SOLUBLE (dissolve in oil) compounds need a carrier to move through the environment, but once inside the body they penetrate tissues easily. They are stored in body fat and persist for many years.

34. EXPOSURE AND SUSCEPTIBILITY • Airborne toxins generally cause more ill health than any other exposure. • Lining of lungs easily absorbs toxins. • Food, water and skin contact are other ways to be exposed to toxins. • Largest toxin exposure reported in industrial settings • Condition of organism and timing of exposure also have strong influences on toxicity. Children more vulnerable than adults. • BODY BURDEN - accumulated toxins in the body

35. BIOACCUMULATION selective absorption & storage of toxins • Dilute toxins in the environment can build to dangerous levels inside 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.

36. 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 toxins may be stored for a long period of time and spread to unintended victims • PERSISTENCE- how long a chemical remains in the environment

38. PERSISTENT ORGANIC POLLUTANTS - POP’s • FLAME RETARDANTS (PBDE) are now found in humans and other species everywhere in the world. Harm children’s reproductive and nervous systems. • NON-STICK PLASTIC COATINGS (PFOS and PFOA) are infinitely persistent in the environment and can be found in your blood. Cause liver damage and cancer. • PHTHALATES - found in plastics mimic estrogen and are linked to reproductive abnormalities and reduced fertility.

39. 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 • Example: Asbestos exposure increases risk of lung cancer 20X; smoking has same risk. But together, they increase risk 400X.

40. 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. • Sometimes compounds that are harmless can be broken down into products that are harmful.

41. EXCRETION AND REPAIR • Effects of waste products and environmental toxins reduced by eliminating via excretion. • Breathing • Urine • Tissues and organs often have mechanisms for damage repair by cellular reproduction. • Any irritating agent can be potentially carcinogenic because the more times that cells divide, the greater the chance that they will have a mistake (mutation) while copying their DNA. This can lead to cancer.

42. DOSE-RESPONSE STUDIES • EPIDEMIOLOGY - gathers data from large exposed populations over long periods and compares with a population group not exposed the threat • DOSE-RESPONSE ANALYSIS measures response of test animals to various doses of suspected toxicant • DOSE = the amount of toxicant the test animal receives • RESPONSE = the type or magnitude of negative effects of the animal • DOSE-RESPONSE CURVE = the plot of dose given against response

43. DOSE-RESPONSE STUDIES • LD50- “median Lethal Dose” that kills 50% of the individuals in 2 weeks • ED50- “median Effective Dose” that causes 50% of the animals to display the harmful but nonlethal effect • LC50 – “median Lethal Concentration” that kills 50% of aquatic species • Not very accurate as different animals & people respond differently. • Helps us determine at what levels of pollution, drugs, and other substances we should/should not be exposed.

47. Most members in this population are similar, however there are extremes at both ends

48. 0-10 very sensitive 10-30 relatively sensitive (20 is average) 30-40 very insensitive

49. 3 POSSIBLE DOSE-RESPONSE CURVES

50. DOSE-RESPONSE RELATIONSHIP Typical shape – small doses have minimal effect, then increases rapidly after threshold • Establishes casualty that the chemical has induced • Establishes the lowest dose where an induced effect occurs (the threshold effect) • Determines the rate at which an injury builds up