1、Environmental Hazards and Human HealthChapter 14WHAT MAJOR HEALTH HAZARDS DO WE FACE?Section 14-1Risks are usually expressed as probabilities A risk is the probability of suffering harm from a hazard that can cause injury,disease,death,economic loss,or damage.Probabilitya mathematical statement abou
2、t the likelihood that harm will be suffered from a hazard.“The lifetime probability of developing lung cancer from smoking one pack of cigarettes per day is 1 in 250.”This means that 1 of every 250 people who smoke a pack of cigarettes every day will likely develop lung cancer over a typical lifetim
3、e.Risks are usually expressed as probabilities Risk assessment is the process of using statistical methods to estimate how much harm a particular hazard can cause to human health or to the environment.It helps us to establish priorities for avoiding or managing risks.Risk management involves decidin
4、g whether or how to reduce a particular risk to a certain degree.Risk assessment and risk managementFig.14-2,p.349Risk AssessmentRisk ManagementWhat is the hazard?How does it compare with other risks?Risk reduction How much should it be reduced?Probability of risk How likely is the event?Risk reduct
5、ion strategy How will the risk be reduced?Consequences of risk What is the likely damage?Financial commitment How much money should be spent?Comparative risk analysisHazard identificationWe face many types of hazards Biological hazards from more than 1,400 pathogens that can infect humans.A pathogen
6、 is an organism that can cause disease in another organism.Bacteria.Viruses.Parasites.Protozoa.Fungi.We face many types of hazards Chemical hazards from harmful chemicals in air,water,soil,food,and human-made products.Natural hazards such as fire,earthquakes,volcanic eruptions,floods,and storms.Cult
7、ural hazards such as unsafe working conditions,unsafe highways,criminal assault,and poverty.Lifestyle choices such as smoking,making poor food choices,drinking too much alcohol,and having unsafe sex.WHAT TYPES OF BIOLOGICAL HAZARDS DO WE FACE?Section 14-2Some diseases can spread from one person to a
8、nother An infectious disease is caused when a pathogen such as a bacterium,virus,or parasite invades the body and multiplies in its cells and tissues.Tuberculosis,flu,malaria,and measles.Bacteria are singe-cell organisms that are found everywhere.Most are harmless or beneficial.A bacterial disease r
9、esults from an infection as the bacteria multiply and spread throughout the body.Some diseases can spread from one person to another Viruses are smaller than bacteria and work by invading a cell and taking over its genetic machinery to copy themselves.They then multiply and spread throughout ones bo
10、dy,causing a viral disease such as flu or AIDS A transmissible disease is an infectious bacterial or viral disease that can be transmitted from one person to another.Some diseases can spread from one person to another A nontransmissible disease is caused by something other than a living organism and
11、 does not spread from one person to another.Examples include cardiovascular(heart and blood vessel)diseases,most cancers,asthma,and diabetes.In 1900,infectious disease was the leading cause of death in the world.Greatly reduced by a combination of better health care,the use of antibiotics to treat i
12、nfectious diseases caused by bacteria,and the development of vaccines.Ways infectious disease organisms can enter the human bodyHumansFetus and babiesOther humansWaterAirInsectsWild animalsLivestockPetsFoodStepped ArtFig.14-3,p.351Infectious diseases are still major health threats Infectious disease
13、s remain as serious health threats,especially in less-developed countries.Spread through air,water,food,and body fluids.A large-scale outbreak of an infectious disease in an area is called an epidemic.A global epidemic such as tuberculosis or AIDS is called a pandemic.Many disease-carrying bacteria
14、have developed genetic immunity to widely used antibiotics and many disease-transmitting species of insects such as mosquitoes have become immune to widely used pesticides that once helped to control their populations.Deaths per year by the 7 deadliest infectious diseasesDisease(type of agent)Deaths
15、 per yearPneumonia and flu(bacteria and viruses)3.2 millionHIV/AIDS(virus)1.8 millionDiarrheal diseases(bacteria and viruses)1.6 millionTuberculosis(bacteria)1.3 millionMeasles(virus)800,000Malaria(protozoa)780,000Hepatitis B(virus)600,000Stepped ArtFig.14-4,p.351Ways to prevent or reduce the incide
16、nce of infectious diseasesWHAT TYPES OF CHEMICAL HAZARDS DO WE FACE?Section 14-3Some chemicals can cause cancers,mutations,and birth defects A toxic chemical is one that can cause temporary or permanent harm or death to humans and animals.In 2004,the EPA listed arsenic,lead,mercury,vinyl chloride(us
17、ed to make PVC plastics),and polychlorinated biphenyls(PCBs)as the top five toxic substances in terms of human and environmental health.There are three major types of potentially toxic agents.Carcinogens are chemicals,types of radiation,or certain viruses that can cause or promote cancer.Mutagens ar
18、e chemicals or forms of radiation that cause mutations,or changes,in the DNA molecules found in cells,or that increase the frequency of such changes.Teratogens are chemicals that cause harm or birth defects to a fetus or embryo.Some chemicals may affect our immune and nervous systems Our bodys immun
19、e system protects us against disease and harmful substances by forming antibodies that render invading agents harmless,but some chemicals interfere with this process.Arsenic.Methylmercury.Dioxins.Some chemicals may affect our immune and nervous systems Some natural and synthetic chemicals in the env
20、ironment,called neurotoxins,can harm the human nervous system,causing the following effects.Behavioral changes.Learning disabilities.Retardation.Attention deficit disorder.Paralysis.Death.Some chemicals may affect our immune and nervous systems Examples of neurotoxins.PCBs.Methylmercury.Arsenic.Lead
21、.Certain pesticides.Some chemicals may affect our immune and nervous systems The EPA estimates that about 1 in 12 women of childbearing age in the US has enough mercury in her blood to harm a developing fetus.The greatest risk from exposure to low levels of methylmercury is brain damage in fetuses a
22、nd young children.Methylmercury may also harm the heart,kidneys,and immune system of adults.EPA advised nursing mothers,pregnant women,and women who may become pregnant not to eat shark,swordfish,king mackerel,or tilefish and to limit their consumption of albacore tuna.In 2003,the UN Environment Pro
23、gramme recommended phasing out coal-burning power plants and waste incinerators throughout the world as rapidly as possible.Other recommendations are to reduce or eliminate mercury in the production of batteries,paints,and chlorine by no later than 2020.Ways to prevent or control inputs of mercury p
24、ollutionSome chemicals affect the human endocrine system The endocrine system is a complex network of glands that release tiny amounts of hormones that regulate human:Reproduction.Growth.Development.Learning ability.Behavior.Some chemicals affect the human endocrine system Hormonally active agents(H
25、AA)are synthetic chemicals that disrupt the endocrine system in humans and some other animals.Examples include aluminum,Atrazine and several other herbicides,DDT,PCBs,mercury,phthalates,and bisphenol A(BPA).Some disrupt the endocrine system by attaching to estrogen receptor molecules.Thyroid disrupt
26、ers cause growth,weight,brain,and behavioral disorders.Some chemicals affect the human endocrine system BPA is found in plastic water bottles,baby bottles and the plastic resins line food containers.Studies found that low levels of BPA cause numerous problems such as brain damage,early puberty,prost
27、ate cancer,breast cancer,and heart disease.Studies funded by the chemical industry found no evidence or only weak evidence,for adverse effects from low-level exposure to BPA in test animals.In 2008,the FDA concluded that BPA in food and drink containers does not pose a health hazard.In 2010,Canada c
28、lassified BPA as a toxic chemical and banned its use in baby bottles,and the EU voted to ban the sale of plastic baby bottles that contain BPA.Some chemicals affect the human endocrine system Phthalates are found in detergents,perfumes,cosmetics,deodorants,soaps,and shampoo,and in PVC products such
29、as toys,teething rings,and medical tubing used in hospitals.Phthalates cause cancer and other health problems in laboratory animals.HOW CAN WE EVALUATE CHEMICAL HAZARDS?Section 14-4Many factors determine the harmful health effects of chemicals Toxicology is the study of the harmful effects of chemic
30、als on humans and other organisms.Toxicity is a measure of the harmfulness of a substance.Any synthetic or natural chemical can be harmful if ingested in a large enough quantity.The dose is the amount of a harmful chemical that a person has ingested,inhaled,or absorbed through the skin.Many variable
31、s can affect the level of harm caused by a chemical.Toxic chemicals usually have a greater effect on fetuses,infants,and children than on adults.Scientists use live laboratory animals and non-animal tests to estimate toxicity The most widely used method for determining toxicity is to expose a popula
32、tion of live laboratory animals to measured doses of a specific substance under controlled conditions.Lab mice and rats are widely used because their systems function somewhat like human systems.Results plotted in a dose-response curve.Determine the lethal dose.Median lethal dose(LD50)is the dose th
33、at can kill 50%of the animals(usually rats and mice)in a test population within an 18-day period.Hypothetical dose-response curve for LD50Toxicity ratings and average lethal doses for humansPotentially harmful chemicals found in many homesFig.14-12,p.363Shampoo Perfluorochemicals to add shineTeddy b
34、ear Some stuffed animals made overseas contain flame retardants and/or pesticidesClothing Can contain perfluorochemicalsNail polish Perfluorochemicals and phthalatesBaby bottle Can contain bisphenol AMattress Flame retardants in stuffingPerfume PhthalatesHairspray PhthalatesCarpet Padding and carpet
35、 fibers contain flame retardants,perfluorochemicals,and pesticidesFood Some food contains bisphenol ATV Wiring and plastic casing contain flame retardantsMilk Fat contains dioxins and flame retardantsSofa Foam padding contains flame retardants and perfluorochemicalsFrying pan Nonstick coating contai
36、ns perfluorochemicalsTile floor Contains perfluorochemicals,phthalates,and pesticidesFruit Imported fruit may contain pesticides banned in the U.S.Water bottle Can contain bisphenol AComputer Flame retardant coatings of plastic casing and wiringToys Vinyl toys contain phthalatesTennis shoes Can cont
37、ain phthalatesHOW DO WE PERCEIVE RISKS AND HOW CAN WE AVOID THE WORST OF THEM?Section 14-5Estimated deaths per year in the world from various causesThe greatest health risks come from poverty,gender,and lifestyle choices The best ways to reduce ones risk of premature death and serious health problem
38、s are to:avoid smoking and exposure to smoke lose excess weight reduce consumption of foods containing cholesterol and saturated fats eat a variety of fruits and vegetables exercise regularly drink little or no alcohol avoid excess sunlight practice safe sexHow key risks can shorten an average life
39、spanDifference between a healthy lung and one with emphysemaMost people do a poor job of evaluating risks Many people deny or shrug off the high-risk chances of death(or injury)from voluntary activities they enjoy,such as:Motorcycling(1 death in 50 participants).Smoking(1 in 250 by age 70 for a pack
40、-a-day smoker)Hang gliding(1 in 1,250).Driving(1 in 3,300 without a seatbelt and 1 in 6,070 with a seatbelt).Most people do a poor job of evaluating risks Some of these same people may be terrified about their chances of being killed by:A gun(1 in 28,000 in the United States).Flu(1 in 130,000).Nucle
41、ar power plant accident(1 in 200,000).West Nile virus(1 in 1 million).Lightning(1 in 3 million).Commercial airplane crash(1 in 9 million).Snakebite(1 in 36 million).Shark attack(1 in 281 million).Most people do a poor job of evaluating risks Five factors can cause people to be being more or less ris
42、ky than experts judge.Fear.Degree of control we have.Whether a risk is catastrophic instead of chronic.Some people suffer from optimism bias,the belief that risks that apply to other people do not apply to them.Many risky things are highly pleasurable and give instant gratification.Several principle
43、s can help us evaluate and reduce risk Compare risks.Determine how much risk you are willing to accept.Evaluate the actual risk involved.Concentrate on evaluating and carefully making important lifestyle choices.Three big ideas We face significant hazards from infectious diseases such as flu,AIDS,di
44、arrheal diseases,malaria,and tuberculosis,and from exposure to chemicals that can cause cancers and birth defects,and disrupt the human immune,nervous,and endocrine systems.Because of the difficulty in evaluating the harm caused by exposure to chemicals,many health scientists call for much greater e
45、mphasis on pollution prevention.Becoming informed,thinking critically about risks,and making careful choices can reduce the major risks we face.End of“Short Version”The slides that follow are those taken out of the“long version”of this same lecture.You should still read the following slides for bett
46、er understanding,but I will not go over them in class unless you have specific questions.Viral diseases and parasites kill large numbers of people Viruses evolve quickly,are not affected by antibiotics,and can kill large numbers of people.The biggest killer is the influenza,or flu,virus,which is tra
47、nsmitted by the body fluids or airborne emissions of an infected person.The second biggest viral killer is the human immunodeficiency virus(HIV).HIV infects about 1.8 million people each year,and the complications resulting from AIDS kill about 1.8 million people annually.Viral diseases and parasite
48、s kill large numbers of people The third largest viral killer is the hepatitis B virus(HBV),which damages the liver and kills about a million people each year.Transmitted by unsafe sex,sharing of needles by drug users,infected mothers who pass the virus to their offspring before or during birth,and
49、exposure to infected blood.Emergent diseases are illnesses that were previously unknown or were absent in human populations for at least 20 years.One is the West Nile virus,which is transmitted to humans by the bite of a common mosquito that is infected when it feeds on birds that carry the virus.Vi
50、ral diseases and parasites kill large numbers of people Greatly reduce your chances of getting infectious diseases by practicing good,old-fashioned hygiene.Wash your hands thoroughly and frequently.Avoid touching your face.Stay away from people who have flu or other viral diseases.We can reduce the
