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Chapter 17 Environmental Hazards and Human HealthCore Case Study (Slide 2)AIDS caused by HIVLeaves the body vulnerable to infections such as TB and rare cancers (Slide 3)Transmitted by:Unsafe sexSharing needlesInfected mothers passing to offspring before or during birthExposure to infected bloodIdentified in 1981 and has spread expIn 2007, 33 million people worldwide infected (1.1 million in US, 2/3 in sub-Saharan Africa, SSA)6800 new cases/dayIncubation period of 7-10 yearsCurrently, there is no cure for HIV and no cure for AIDS. If you get AIDS, you will almost certainly die from it.AIDS has reduced life expectancy for 750 million in SSA from 62 to 47—40 in 7 countries most severely affected.Drastically alters age structure (Slides 4 and 5)Chapter looks at connections between environmental hazards and human health and at what we can do to reduce these threats17-1 What Major Health Hazards Do We Face? (Slide 6)Concept 17-1 People face health hazards from biological, chemical, physical, andcultural factors, and from the lifestyle choices they make.Risks Are Usually Expressed as Probabilities (Slide 7)Risk – the probability of suffering harm from hazards that can cause injury, disease, death, economic loss, or damage.Expressed as a probability – a mathematical statement about the likely hood of an event.Difference between possibility and probability?Risk assessment – scientific process of using statistical methods to estimate how much harm a particular hazard can cause to human health or to the environment.Used to compare risks and establish priorities for avoiding or managing risk.Risk Management – involves deciding whether or how to reduce risk to a certain level and at what cost. (Slides 8 and 9)Most people are not good at understanding and comparing risk (Example avian flu and common fluWe Face Many Types of Hazards (Slide 10)All take risks every dayThe key questions are, how serious are the risks we face, and do benefits of such activities outweigh the risks?Five types of hazardsBiological: pathogensChemicalPhysicalCultural – unsafe working conditions, unsafe highways, criminal assault, poverty.Lifestyle choicesWhat Types of Biological Hazards Do We Face?Concept 17-2 In terms of death rates, the most serious infectious diseases are flu, AIDS,diarrheal diseases, malaria, and tuberculosis; most of these deaths occur in developingcountries. (Slide 11)Some Diseases Can Spread from One Person to Another (1) (Slide 12)Nontransmissible disease – caused by something other than a living organism and does not spread from one person to another.tend to develop slowly and have multiple causescardiovascular diseases, cancers, asthmas, diabetes, and malnutritionIncidences of such diseases increase with increases in life expectancyInfectious disease – caused when a pathogen such as a bacterium, virus, or parasites invades the body and multiplies in its cells and tissues.Examples: flu, HIV, malaria, TB and measlesTransmissible disease (contagious or communicable disease) – infectious disease that can be transmitted from person to another.Leading cause of death (Slide 13)In 1900, infectious diseases, world and in the USIn 1950, incidences and death rates from infectious diseases reducedBecause of better healthcare, antibiotics, and vaccinesAssessing the state of health of a populationTraditionally described by leading causes of deathDoes not give an accurate picture of the nonfatal effects of diseases and injuryDisability-adjusted life years (DALYs) – measure total disease burden on a population.Designed to measure the amount of ill health, including premature death and disability from diseases and injuriesCritics: shortage of reliable data, how to evaluate seriousness of various disabilities among cohorts.Major Causes of Death in the World and in the United States in 2005 (Slides 14 to 16)Infectious Diseases Are Still Major Health Threats (Slide 17)Especially in developing countriesMajor pathways for infectious diseases (Slides 18 and 19)Define epidemic and pandemicThe seven deadliest infectious diseases (Slides 20 to 22)Growing problem: genetic resistance to antibiotics (and vaccines) and genetic resistance by insect vectors to pesticides.Science Focus: Genetic Resistance to Antibiotics Is Increasing (Slide 23)Bacteria reproduce at an astounding rate, some up to 16 million in 24 hoursCan rapidly evolve drug resistanceSome drug-resistant bacteria can transfer their resistance to nonresistant bacteriaOther factors that play role in promoting resistanceTravel and international trade can spread harmful bacteria.Overuse of antibioticsA 2000 study, half of antibiotics prescribed unnecessarilyIn some countries, available without prescriptionIndustrial farmingAntimicrobial soapsEvery major disease causing bacteria has developed resistance to at least one of 160 antibiotics90 000 of 2 million die from mostly preventable infections while in US hospitalsOveruse of pesticides contributes to pesticide resistance among invertebrate vectors.Methicillin-resistant Staphylococcus aureus (MRSA) (Slide 24)Staph infection that has become resistant to most common antibioticsCause a vicious form of pneumonia, flesh-eating wounds, and quick death of it gets into the blood.Most antibiotics work by crippling key protein in bacteria, but bacteria develop immunityIn 2008, Univ. of Penn developed analog molecules similar to that in frog pounds “stab” bacteria to death.Ironically, many of our activities are threatening many of the world’s amphibians.Case Study: The Growing Global Threat from Tuberculosis (Slide 25)Since 1990, most underreported is the rapid spread of TBInfects 9.2 million, kills 1.7 million (84% in developing countries)Many do not know they are sick; half do not know they are infected.Each person with active TB typically infects 10-15 people.Factors that account for recent increasesFew TB screening and control programs, esp. in developing countries (95% of new cases occur).Most strains of TB have developed resistance to the majority of the effective antibiotics.Population growth, urbanization, and air travelSlowing the spread requiresEarly detection and treatmentTreatment with four inexpensive drugsTo be effective, must be taken every day for 6-8 moRecent years, multi-drug resistant TB has appearedNow found in 45 countries500 000 new cases each yearVictims must be permanently quarantined from the rest of societySome Viral Diseases Kill Large Numbers of People (Slide 26)Viruses evolve quicklyThree most widespread and dangerous viruses?Influenza, HIV, Hepatitis BFlu is the #1 killerTransmitted by body fluids and airborne emissionsPandemic possible, would kill millions (Spanish Flu of 1918 killed 20-50 million worldwide, 250 000 to 500 000 in US)HIVInfects 2.5 million annuallyKills 2.1 millionNot as easily spread as the common fluAntiviral drugs increase average life to 24 more years, but costly ($25 200 a year)WHO calls for a global strategy to slow spread of AIDS, six priorities (Slide 27):Reduce number of new infection below number of deathsConcentrate on groups that are most likely to spread the diseaseProvide HIV testing and pressure high risk groups to get testedMass advertising and education toward adults and schoolchildrenProvide low-cost drugsIncrease funding for research on the development of microbiocidesHepatitis B virus (HBV) (Slide 28)Damages liver and kills 1 million people each yearTransmission is similar to HIVZoonoses are an increasing problemWest Nile virusSevere acute respiratory syndrome (SARS) Emerging and reemerging infectious diseasesReduce chances of infection: Wash your hands!Science Focus: Tracking the Spread of Infectious Diseases to Humans from Other Animals (Slide 29)Ecological medicine – new interdisciplinary field devoted to tracking the connection of disease transmission between humans and wildlife.Human practices that encourage the spread of diseases from animals to humansClearing forests (ex. Tropical forests and malaria)Climate change (Spread tropical diseases)Fragmentation and encroachment (Lyme disease in eastern US)Sprawl reduces habitat for top predators increase in prey that are vectors for diseasesBush meat (Simian HIV, Herpes B from some monkeys)Legal and illegal international trade of wildlife and wildlife partsIndustrial meat production and food-borne diseases3372485218440General global trade, ecotourismCase Study: Malaria—Death by Parasite-Carrying Mosquitoes (Slide 30)Should be a concern to anyone traveling to tropical regions – no vaccineLife cycle of malaria (Plasmodium sp, a pathogenic protest) Female injects sporozoites into hostGo to liver and develop merozoitesEnter red blood cellsDevelop into gametocytes (makes person an infected reservoirBursting red blood cells release toxins that cause intense fever, chills, sweating, severe abdominal pain, headaches, vomiting, extreme weakness, susceptibility to other diseases.Kills 1-2 million per year90 % younger than 5 years oldMany of the children that survive have brain damageMalaria repeats cycle until immunity develops, treatment given, or the individual dies.Control efforts of the 1950s and 1960s have seen a reduction in efficacy. (Slide 31)Mosquitoes pesticide resistancePlasmodium develops resistance to anti-malarial drugsEffects of Global WarmingPrevention malaria infections (Slide 32 Geographic distribution, Slide 33)New anti-malarial drugs (ex: artemisinins from sweet wormwood plant)VaccinesBiological control of Anopheles mosquitoes.Engineering mosquitoes to be resistant to malariaExposing mosquitoes to hormone that causes dehydrationInsecticide treated netsZn and vitamin A may boost resistance in childrenSpray homes with low concentrations of DDTWe Can Reduce the Incidence of Infectious DiseasesFigure 17-10, solutions to prevent or reduce incidence of infectious diseases (Slides 34-36)Oral rehydration therapy – simple solution of boiled water, salt, sugar or riceBad news: WHO report that only 10 % of global warming medical R&D goes toward preventing infectious diseases in developing countries.17-3 What Types of Chemical Hazards Do We Face? (Slide 45)Concept 17-3 There is growing concern about chemicals that can cause birth defects and cancers and disrupt the human immune, nervous, and endocrine systems.Some Chemicals Can Cause Cancers, Mutations, and Birth DefectsToxic chemicals – causes temp or permanent harm or death to human animals (Slide 46)EPA, in 2004, listed the 5 most toxic substancesAs, Pb, Hg, vinyl chloride, and PCBsThree Major TypesCarcinogens – chemicals, types of radiation, or viruses that can cause or promote cancer.Examples: As, benzene, chloroform, formaldehyde, gamma rays, Ni, PCBs, Rn, tobacco smoke, UV, x-rays, and vinyl chlorideTime lag between exposure and appearance of detectable cancer, 10-40 yrs.Mutagens – chemicals or forms of radiation that cause mutations in DNA or increase frequency of such changes.Example: HNO2 forms in the stomach from NO2- found in food preservatives.Mutations in reproductive cells can be passed on to future generations.Teratogens – Chemicals that cause harm or birth defects to fetuses or embryos.Examples: Angel dust, benzene, Cd, formaldehyde, Pb, Hg, mescaline, PCBs, phthalates, thalidomide and vinyl chloride.Case Study: PCBs Are Everywhere—A Legacy from the Past (Slide 47)PCBs – class of more than 200 chlorine containing organic compounds that are very stable and non-flammable.US congress banned domestic production in 1977, because they were linked to liver and other cancers.Because PCBs are breakdown very slowly, they can travel long distances in the environment.Fat soluble and can be biologically magnified in ecosystems.PCBs are now found everywhere.Polar bears and penguins, and mother’s milk70 % of PCBs made in the US are still in the environment (Slides 48 and 49) Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems (Slide 50)Some chemicals such as As, methyl-Hg, and dioxins can weaken the immune system.Some neurotoxins (toxic to nervous system) are natural and some are syntheticEffects include behavioral, learning disabilities, retardation, ADD, paralysis, death.Examples: PCBs, methyl-Hg, As, Pb, certain pesticides, poisonous and venomous animals.Some compounds can disrupt the endocrine system – a complex network of glands that release hormones into the body’s circulatory system. (Slide 51)Low levels of hormones control sexual reproduction, development, learning, and behavior.Receptor and hormone described as a chemical “lock-and-key” mechanism.Hormonally active agents (HAAs) can mimic hormones.Natural biological evolution has not equipped us to deal with these synthetic imposters.Can impair reproductive system and sexual development, and cause physical and behavioral disorders.Examples: Al, atrazine, several herbicides, DDT, Hg, PCBs, phthalates, and bisphenol A.Gender benders – effect sexual development and reproductionArticle: Pesticide Turns Male Frogs into Females, By Rachael Rettner, LiveScience Staff Writer posted: 01 March 2010 03:03 pm ET Hormone blockers – prevent hormones from attaching to their receptors.Thyroid disrupters – cause growth, weight, brain, and behavioral disorders.Phthalates – used to soften PVCFound in a variety of products: toys, teething rings, blood storage bags, medical tubing, solvents (perfumes, cosmetics, , body lotion, hair sprays, deodorants, nail polishes and shampoos)A 2008 study found that 81% of 162 infants, ages 2 to 28 mo had measurable amounts of phthalates in their urine.Laboratory animal studies show that high doses caused birth defects, liver cancer, kidney and liver damage, premature breast development, immune suppression, and abnormal sexual development.Science Focus: Mercury’s Toxic Effects (Slide 52)Mercury a teratogen and potent neurotoxin.Enters the atmosphere:1/3 from natural sources: rocks, soil, volcanoes and vaporization from oceans2/3 from human activities: coal burning, waste incinerators and chemical manufacturing plants.Elemental, thus persistent thus it accumulates in soil, water, and tissues of animals (humans are animals too)2007 Hotspots (Slide 53)New England, New York, Nova ScotiaThe ArtcticFound in every fish sampled from 626 Rivers in 12 statesBut, generally at concentrations considered safe to eat occasionallyUnusually high levels found in 178 wild song birds in New York state which do not live in aquatic settings and do not eat fish.Exposure to mercuryInhalation of vaport (Hg) or particulate salts (such as HgS and HgCl2)Eat contaminated food, esp. fishEffects on humansNeurological problems including reduced IQ for individuals exposed to mercury in the wombIn adults, can harm the heart, kidneys, and immune systemWho’s at risk?In 2007, EPA estimated that 1 in 6 women of childbearing age have enough mercury to harm a developing fetus (= 630 000 of 4 million babies born in the US each year)In 2004, both FDA and EPA advised woman of child bearing age not eat shark, swordfish, king mackerel or tilefish and to limit albacore tuna to no more than 6 ounces per week.EPA also warned that ? of nations rivers, 1/3 of lake, and ? of the nations coastal waters are contaminated.Slides 54 and 55, movement of mercury in an aquatic environmentSlides 56 and 57, solutions to mercury pollutionSlides 58-60, Model of HAAs and hormone blockersScience Focus: Bisphenol A (Slide 61)Estrogen mimic used as a building block for certain plasticsFound in many common productsWater and baby bottles, microwave dishes, food storage containers, food and beverage can liners, and dental fillings.Laboratory findings (94 Studies)Studies show that this chemical can leach out, esp. when heated with acidic foods and beverages.Exposure to very low levels in lab animals: brain damage, prostate disease, breast cancer, early puberty, reduced sperm count, impaired immune function, type II diabetes, hyperactivity, increased aggressiveness, impaired learning, impaired learning, increased addiction to drugs such as amphetamines, decreased sex drive in males, and obesity in unborn test animals.12 Studies funded by chemical industryEffects on human healthTwo separate groups funded by NIH have reached different conclusions about exposure to trace amounts of BPA.Should it be banned?17-4 How Can We Evaluate and Deal with Chemical Hazards? (Slide 62)Concept 17-4A Scientists use live laboratory animals, non-animal tests, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations.Concept 17-4B Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful candidates.Many Factors Determine the Harmful Health Effects of a Chemical (Slide 63)Toxicology – is the study of the harmful effects of chemicals on humans and other organisms.Toxicity – measure of how harmful a substance is, i.e., its ability to cause injury, illness, or death to a living organism. Dependent on:Dose AgeGenetic makeup Multiple chemical sensitivity (MCS) Solubility and persistence of the chemicalBiomagnificationResponse – damage to health resulting from exposure to a chemical. (Slide 64)Acute effectChronic effectSlides 65 and 66, Difficulty in estimating the effects of exposure to chemicals is related to the many and often poorly associate variables.Case Study: Protecting Children from Toxic Chemicals (Slide 67)Analysis of umbilical cord blood: significance10 randomly selected individuals from US hospitals287 Chemicals detected180 cause cancer in humans and animals217 damage to the brain and nervous system208 cause birth defects or abnormal developmentInfants and children more susceptible to the toxic effects of chemicals than adultsEat, drink water, and breathe more per unit of body weight than adultsPut their fingers in their mouthsLess well-developed immune systems and body detoxification processesIn 2003, the US EPA proposed that in determining any risk, regulators should assume children face risk 10 time greater than adults; some health scientists suggests 100.Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity (Slide 68)Dose-response curve: median lethal dose (LD50) – amount needed to kill 50 % of the test population (usu. rats or mice) in a test population within an 18 day period.Nonthreshold dose-response model – applies even if the smallest dose produces a harmful effect that increases with the dosage.Threshold dose-response modelCan the data be extrapolated to humans?More humane methods using animals (Slide 69)Replace animals with other modelsComputer simulationsTissue culture and individual animal cellsChicken egg membranesWhat are the effects of mixtures of potentially toxic chemicals?Hypothetical Dose-Response Curve Showing Determination of the LD50 (Slides 70 and 71).Toxicity Ratings and Average Lethal Doses for Humans (Slide 72)Two Types of Dose-Response Curves (Slides 73-74)There Are Other Ways to Estimate the Harmful Effects of Chemicals (Slide 75)Case studiesInformation from accidental or deliberate poisonings, drug overdoses, homicides, or suicide attempts.Not reliable sources for estimation of toxicity, but can provide clues about environmental hazards for future study.Epidemiological Studies – compare the health of people exposed to a particular chemical (“experimental group”) with the health of a similar group not exposed to the agent (control group)Factors that limit epidemiological studies:Too few people testedLength of timeCan you link the result with the chemical?Can’t be used to evaluate new hazardsAre Trace Levels of Toxic Chemicals Harmful? (Slide 76)Almost everyone has now built up in trace levels of toxicants in the blood and other parts of the body.From exposure to trace amounts in the environmentBirth control pills, blood pressure medication, antidepressants, painkillers, plus many other chemicals have been released into waterways or seeped into groundwater.We do not know the effects of trace amountsAre the dangers increasing or are the tests just more sensitive?Some Potentially Harmful Chemicals Found in Most Homes (Slides 77-78)Why Do We Know So Little about the Harmful Effects of Chemicals? (Slide 79)Severe limitations estimating toxicity levels and risks (already discussed, e.g. extrapolating from test animals)Acceptable levels vary between 1/100 and 1/1000 of the estimated harmful levelsHere are interesting bits of data:Roughly 10 % of 100 000 registered synthetic chemicals in commercial use have been screened for toxicity.2 %, tested for determining if they are carcinogens, teratogens, or mutagens.99.5 % of the commercially used chemicals in the US are NOT regulated.Pollution Prevention and the Precautionary Principle (Slide 80)EU countries are pushing for greater prevention.Look for less harmful alternativesRecycle waste chemicals to keep them out of the environment as 3M and DuPont have been doing.Application of precautionary principle; better to prevent or reduce than waiting for more conclusive evidence.If precautionary principle were applied, those introducing a new chemical or new technology would have to follow new strategiesA new product is considered harmful until it can be proved to be safeExisting chemicals and technologies that appear to cause significant harm must be removed until safety is established.Indeed this is not without controversy.2000: global treaty to ban or phase out the dirty dozen (POPs)DDT and eight other pesticides, PCBs, dioxins, and furansHarmful effects include tumors and cancer, birth defects, compromised immune system, feminization in males, masculinization in females, abnormal thyroid function, and reproductive failure.Treaty went into effect in 2004, but not ratified and implemented in USIndividuals Matter: Ray Turner and His Refrigerator (Slide 81)1974: Ozone layer being depleted by chlorofluorocarbons (CFCs)1992: International agreement to phase out CFCs and other ozone-destroying chemicalsRay Turner: citrus-based solvents to clean circuit boards17-5 How Do We Perceive Risks and How Can We Avoid the Worst of Them? (Slide 82)Concept 17-5 We can reduce the major risks we face if we become informed, think criticallyabout risks, and make careful choices.The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices (Slide 83)Risk analysis involvesRisk assessment – identifying hazards and evaluating risksComparative analyses/Ranking risksRisk management – determining options and making decisions about reducing or eliminating risks.Risk communication – informing decision makers and the public about the riskGreatest health risksPoverty caused by malnutrition, increased susceptibility to normally non-fatal diseases, fatal diseases from unsafe drinking water.Gender Lifestyle choicesComparative Risk Analysis: Most Serious Ecological and Health Problems (Slides 84 and 85)Global Outlook: Number of Deaths per Year in the World from Various Causes (Slides 86 and 87)Comparison of Risks People Face in Terms of Shorter Average Life Span (Slide 88)Case Study: Death from Smoking (Slide 89)Most preventable major cause of suffering and premature deathFrom 25 associate illnesses including: heart diseases, lung cancer, other cancers, bronchitis, emphysema, and stroke.Worldwide 14800 people per dayIn US, 1210 people per dayNicotine: additiveEffects of passive smoking (secondhand smoke)How to reduce smoking (Slide 90)TaxesBanClassify and regulate nicotineEducationAnnual Deaths in the U.S. from Tobacco Use and Other Causes in 2004 (Slides 91 and 92)Estimating Risks from Technologies Is Not Easy (Slide 93)System reliability = Technological reliability x Human reliabilityTo err is humanMost People Do Not Know How to Evaluate Risks (Slide 94)FearDegree of controlWhether a risk is catastrophicOptimism biasUnfair distribution of risksSeveral Principles Can Help Us to Evaluate and Reduce Risk (Slide 95)Compare risksDetermine how much you are willing to accept Determine the actual risk involvedConcentrate on evaluating and carefully making important lifestyle choices ................
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