Transcript ESC110-2ed
ESC110 Chapter Eight: Environmental Health and Toxicology Principles of Environmental Science - Inquiry and Applications, 2nd Edition by William and Mary Ann Cunningham 1 Chapter Eight Readings Required Readings Cunningham & Cunningham, Chapter Eight: Environmental Health and Toxicology 2 Chapter Eight Objectives At the end of this lesson, you should be able to • define health an disease in terms of some major environmental factors that affect humans • Understand some of the risks of bioterrorism and emergent diseases • distinguish between toxic and hazardous chemicals, and between chronic and acute exposures and responses • compare the relative toxicity of some natural and synthetic compounds, and report on how such ratings are determined and what they mean • evaluate the major environmental risks we face and how risk assessment and risk acceptability are determined. 3 Chapter Eight Key Terms McGraw-Hill Course Glossary acute effects allergens antigens bioaccumulations biomagnification cancer carcinogens chronic effects Disability-Adjusted Life Year (DALY) disease emergent disease endocrine hormone disrupters fetal alcohol syndrome hazardous health LD50 morbidity mutagens neurotoxins • prospective study • retrospective study • risk • synergism • toxins • teratogens 4 Chapter Eight Topics • • • • • • Types of Environmental Health Hazards Movement, Distribution, and Fate of Toxins Mechanisms for Minimizing Toxic Effects Measuring Toxicity Risk Assessment and Acceptance Establishing Public Policy 5 Part 1: Types of Environmental Health Hazards In some parts of Eastern Europe and the former USSR, up to 90 % of all children suffer from environmentally linked diseases. 6 What is Health? • The World Health Organization (WHO) defines health as a state of complete physical, mental, and social wellbeing. • Disease - a deleterious change in the body's condition in response to an environmental factor • Morbidity - illness • Mortality - death 7 8 9 At any given time, about 2 billion people suffer from worms, protozoans, and other internal parasites. 10 Recent outbreaks of lethal infectious diseases SARS 2003 11 Factors Contributing to the Spread of Contagious Diseases • • • • • High population densities Settlers pushing into remote areas Human-caused environmental change Speed and frequency of modern travel Contact with water or food contaminated with human waste 12 Antibiotic and Pesticide Resistance • Indiscriminate use of antibiotics and pesticides - perfect recipe for natural selection • Protozoan that causes malaria now resistant to most antibiotics, and mosquitoes have developed resistance to many insecticides • Drug resistance: TB, Staph A, flesheating bacteria 13 Fig. 8.6 14 Hazardous and Toxic Chemicals • Allergens formaldehyde • Immune system depressants - PCBs? • Neurotoxins - lead, DDT • Mutagens • Teratogens - alcohol • Carcinogens 15 16 Mortality rate for most major cancers has been stable or falling in recent years. One exception is lung cancer (rise blamed on increased smoking). 17 Importance of Diet • At least half of all Americans are considered overweight. • Strong correlation between cardiovascular disease and the amount of salt and animal fat in one's diet • Fruits, vegetables, whole grains, complex carbohydrates, and dietary fiber have beneficial health effects. • Eating too much food has negative effects on health. 18 Part 2: Movement, Distribution, and Fate of Toxins 19 Bioaccumulation and Biomagnification • Bioaccumulation dilute toxins in the environment can reach dangerous levels inside cells and tissue • Biomagnification the effects of toxins are magnified through food webs 20 "DDT - Powerful Insecticide, Harmless to Humans" 21 22 Part 3: Minimizing Toxic Effects • Every material can be poisonous under some conditions. • Taken in small doses, most toxins can be broken down or excreted before they do much harm. • Liver - primary site of detoxification • Tissues and organs - high cellular reproduction rates replace injured cells down side: tumors, cancers possible 23 Part 4: Measuring Toxicity Animal Testing • Most commonly used and widely accepted • Expensive - hundreds of thousands of dollars to test one toxin at low doses • Time consuming • Often very inhumane • Difficult to compare toxicity of unlike chemicals or different species of organisms 24 A Typical Dose/Response Curve 25 LD50 - the dose of a toxin that is lethal to half the test population 26 It is useful to group materials according to their relative toxicity. 27 Acute Versus Chronic Doses and Effects • Acute effect - immediate health effect caused by a single exposure to a toxin (can be reversible) • Chronic effect - long lasting or permanent health effect caused by (1) a single exposure to a very toxic substance or (2) continuous or repeated sub lethal exposure to a toxin 28 Part 5: Risk Assessment and Acceptance • Risk - the probability of harm times the probability of exposure • A number of factors influence how we perceive relative risks associated with different situations. • Accepting risks - we go to great lengths to avoid some dangers, while gladly accepting others 29 30 Part 6: Establishing Public Policy In setting standards for environmental toxins, we need to consider: • Combined effects of exposure to many different sources of damage • Different sensitivities of members of the population • Effects of chronic as well as acute exposures 31 Regulatory Decisions 32 33