Risk, Toxicology, and Human Health. G. Tyler Miller’s Living in the Environment 13 th Edition Chapter 11. Dr. Richard Clements Chattanooga State Technical Community College. Key Concepts. Types of hazards people face. Methods of toxicology. Types and measurement of chemical hazards.
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Risk, Toxicology, and Human Health G. Tyler Miller’s Living in the Environment 13th Edition Chapter 11 Dr. Richard Clements Chattanooga State Technical Community College
Key Concepts • Types of hazards people face • Methods of toxicology • Types and measurement of chemical hazards • Types and effects of biological hazards • Risk estimation, management, and reduction
Risk and Probability Fig. 11-2 p. 229 • Risk= Probability of exposure X Probability of Harm • Probability how risk is measured • Riskassessment • Riskmanagement
Hazards • Cultural hazards Unsafe working conditions, poor diet, drugs, drinking, driving, criminal assault, unsafe sex, poverty • Chemical hazards Chemical in the air, water soil and food • Physical hazards Ionizing radiation, fire, earthquake, volcanic eruption, flood, tornadoes, and hurricanes • Biological hazards Pathogens, pollen, and other allergens, and animals (such as bees, and poisonous snakes) Fig. 11-1 p. 228
Toxicology • Toxicity: measures how harmful a substance is. • Dose: the amount of potentially harmful substance that a person has ingested, inhaled, or absorbed through the skin • Solubility: water soluble toxins and fat or oil soluble toxins • Persistence: resistance to breakdown • Chemical Interactions: synergistic interaction, and antagonistic interactions • Response: type and amount of health damage that results from exposure to a chemical or other agent • Acute Effect • Chronic Effect
Dose-affect Curve Fig. 11-3 p. 230 • Size of dose • How often exposed • Who is exposed • How well the body’s detoxification system responds • Genetic makeup in regards to sensitivity (graph below)
DDT and Bioaccumulation(absorbed or stored in organs) and Biomagnification (through a food chain) Fig. 11-4 p. 231
Poisons: “The dose makes the poison” Paracelsus, 1540 • Poison: LD50 of 50 mg or less/Kg of body weight Fig. 11-5 p. 231 • LD50: median lethal dose: the amount that in one dose kills exactly 505 of the animals in a test population in a 14 day period See Table 11-1 p. 232
How to Estimate Toxicity Case Reports: usually made by physicians; not very reliable; but do give clues to suggest further laboratory tests Epidemiological studies: health of people exposed to a toxin (experimental group) is compared to a statistically similar group of people not exposed to the toxin. Determine if there is any statistically significant association between exposure and health. Many problems with this technique.
How to Estimate Toxicity Laboratory experiments: most widely sued method: expose a population of live laboratory animals (usu. Rats and mice) to a measured dose of a specific substance under controlled conditions. Take 2-5 years and $200,000 – $2 million. More humane procedures increasing in use
Dose-Response Curves: acute toxicity • Dose-response • Nonthreshold • Threshold Fig. 11-6 p. 233
Chemical Hazards • Hazardous chemicals • Mutagens • Teratogens • Carcinogens • Neurotoxins • Hormonally active agents • Precautionary principle
Figure 11-7Page 234 Hormonally Active Agents (HAA’s) Hormone Estrogen-like chemical Antiandrogen chemical Receptor Cell Hormone Mimic Attach to estrogen receptor molecules Hormone Blocker Prevent natural hormones from attaching to their receptors Normal Hormone Process
Biological Hazards: Diseases • Nontransmissible disease: disease that are not caused by living organisms and not spread person to person. • Transmissible disease: caused by a living organism and spread person to person • Pathogens: infectious agents that cause disease include viruses, bacteria, fungi, and protozoans • Vectors: agents that transmit disease such as mosquito, fly, rat, etc. • Antibiotic resistance • Malaria • AIDS See Case Study p. 241
Figure 11-8Page 236 Viruses HIV (AIDS) Smallpox Hepatitis B Protozoa Ebola On this scale, a human hair would be 6 meters (20 feet) wide 1 micrometer Plasmodium (malaria) Bacteria Vibrio cholerae (cholera) Myobacterium tuberculosis (tuberculosis) 10 micrometers Treponema pallidum (syphilis) 6 micrometers Pathogens
Figure 11-9 (1)Page 237 Genetic material Virus Structure Surface proteins
Virus Reproduction The virus attaches to the host cell. The entire virus may enter or it may inject its genetic material, or genome. Virus Cell membrane Host cell The viral genetic material uses the host cell's DNA to replicate again and again. Each new copy of the virus directs the cell to make it a protein shell. The new viruses emerge from the host cell capable of infecting other cells. This process often destroys the first cell.
Antibiotic Resistance In-text figurePage 238 Bacterial colony Drug-resistant bacterium Drug-resistant bacterial colony Mutation Antibiotic Treating a colony of bacteria with an antibiotic kills most of the microbes. Sometimes, a bacterium has a genetic mutation that makes it resistant to the drug. When the colony grows back, all of its members will be descended from the drug-resistant survivor. Antibiotic Harmful microbe Conjunction Harmful drug-resistant microbe Drug-resistant bacterial colony Harmless, drug-resistant microbe Antibiotics attack harmless and harmful microbes. Drug resistance that develops in harmless bacteria may be transferred to harmful bacteria. One bacterium attaches itself to another, and a channel is opened between them in a process called conjugation. A copy of the genes that make the microbe resistant can then be passed from one microbe to the other. Antibiotic
World HIV Distribution in 2001 (number of deaths due to AIDS) Figure 11-10Page 240 Eastern Europe & Central Asia 1 million (23,000) North America 940,000 (20,000) Western Europe 560,000 (6,800) East Asia & Pacific 1 million (35,000) North Africa & Middle East 440,000 (30,000) Caribbean 420,000 (30,000) South & Southeast Asia 6.1 million (400,000) Latin America 1.4 million (80,000) Australia & New Zealand 15,000 (120) Sub-Saharan Africa 28.1 million (2-3 million)
Figure 11-11Page 240 Synergy between AIDS/TB/ Malnutrition HIV/AIDS • HIV immune • suppression • facilitates active • TB development • AIDS can lead to job • loss and poverty Malnutrition TB • Malnutrition weakens • body and may • facilitate HIV • transmission • and progress • Malnutrition may • facilitate development • of active TB • TB can lead • to job loss and • malnutrition • because of • lack of money • Active TB facilitates • HIV replication • and speeds up • HIV progression
Malaria Life Cycle and Infection Fig. 11-14 p. 243
In-text figurePage 241 <2.5 2.5-10 10-35 35-70 70-100 100+ Global TB Epidemic Deaths per 100,000 people
Figure 11-12Page 243 Worldwide Malaria Distribution Malaria-free areas Malaria largely eliminated Malaria transmission areas
Risk Analysis Fig. 11-17p. 247 • Risk analysis • Comparative riskanalysis • Cost-benefitanalysis • Risk management • Risk perception