Environmental Health and Toxicology

1. Environmental Health and Toxicology Chapter 9 Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

2. Outline: • Environmental Health Hazards • Infectious Organisms • Antibiotics and Pesticide Resistance • Toxic Chemicals • Movement and Fate of Toxins • Minimizing Toxic Effects • Measuring Toxicity • Risk Assessment Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

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). Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

4. Infectious Organisms • For most of human history, the greatest health threats have been pathogenic organisms and accidents or violence. • Infectious diseases are still responsible for about 24% of all disease-related deaths. • Majority of these deaths in poorer countries with poor nutrition, sanitation, and vaccination programs. • AIDS now largest single cause of communicable death in the world. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

6. Disability-Adjusted Life Year • WHO reports communicable diseases are responsible for nearly half of all 1.4 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

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 the speed and frequency of modern travel. • Foot and Mouth Disease Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

8. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

9. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

10. Toxic Chemicals • Dangerous chemicals are divided into two broad categories: • Hazardous - Dangerous • Flammable, explosive, irritant, acid, caustic. • Toxic - Poisonous • Can be general or very specific. Often harmful even in dilute concentrations. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

11. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

12. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

13. 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 Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

14. US Age-Adjusted Cancer Death Rates Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

15. Natural and Synthetic Toxins • Many natural chemicals are very dangerous while many synthetic chemicals are relatively harmless. • Both plants and animals produce chemicals similar to neurotransmitters, hormones, and regulatory molecules. • Arsenic and cyanide are both natural. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

16. MOVEMENT, DISTRIBUTION, AND FATE OF TOXINS • 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. • Water soluble compounds move rapidly through the environment, and have ready access to most human cells. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

17. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

18. 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) Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

19. Bioaccumulation Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

20. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

21. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

22. Excretion • Effects of waste products and environmental toxins reduced by eliminating via excretion. • Breathing • Kidneys • Urine Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

23. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

24. Population Sensitivity Variations Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

25. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

26. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

27. 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

28. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

29. ESTABLISHING PUBLIC POLICY • 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. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

30. Summary: • Environmental Health Hazards • Infectious Organisms • Antibiotics and Pesticide Resistance • Toxic Chemicals • Movement and Fate of Toxins • Minimizing Toxic Effects • Measuring Toxicity • Risk Assessment Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

31. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.