Presentation on theme: "Environmental Hazards and Human Health"— Presentation transcript:
1Environmental Hazards and Human Health Chapter 18Environmental Hazards and Human Health
2Core Case Study: The Global HIV/AIDS Epidemic According to the World Health Organization (WHO), over 42 million people worldwide (1.1 million in the U.S.) are infected with HIV.There is no vaccine for HIV – if you get AIDS, you will eventually die from it.Drugs help some infected people live longer, but only a tiny fraction can afford them.
3Core Case Study: The Global HIV/AIDS Epidemic AIDS has reduced the life expectancy of sub-Saharan Africa from 62 to 47 years – 40 years in the seven countries most severely affected by AIDS.Projected age structure of Botswana's population in 2020.Figure 18-2
4Core Case Study: The Global HIV/AIDS Epidemic The virus itself is not deadly, but it cripples the immune system, leaving the body susceptible to infections such as Kaposi’s sarcoma (above).Figure 18-1
5RISKS AND HAZARDSRisk is a measure of the likelihood that you will suffer harm from a hazard.We can suffer from:Biological hazards: from more than 1,400 pathogens.Chemical hazards: in air, water, soil, and food.Physical hazards: such as fire, earthquake, volcanic eruption…Cultural hazards: such as smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty.
6BIOLOGICAL HAZARDS: DISEASE IN DEVELOPED AND DEVELOPING COUNTRIES Diseases not caused by living organisms cannot spread from one person to another (nontransmissible disease), while those caused by living organisms such as bacteria and viruses can spread from person to person (transmissible or infectious)
7Transmissible Disease Pathway for infectious disease in humans.Figure 18-4
8Transmissible Disease WHO estimates that each year the world’s seven deadliest infections kill 13.6 million people – most of them the poor in developing countries.Figure 18-5
9Case Study: Growing Germ Resistance to Antibiotics Rabidly producing infectious bacteria are becoming genetically resistant to widely used antibiotics due to:Genetic resistance: Spread of bacteria around the globe by humans, overuse of pesticides which produce pesticide resistant insects that carry bacteria.Overuse of antibiotics: A 2000 study found that half of the antibiotics used to treat humans were prescribed unnecessarily.
10Case Study: The Growing Global Threat from Tuberculosis The highly infectious tuberculosis (TB) kills 1.7 million people per year and could kill 25 million people 2020.Recent increases in TB are due to:Lack of TB screening and control programs especially in developing countries due to expenses.Genetic resistance to the most effective antibiotics.
11Viral DiseasesFlu, HIV, and hepatitis B viruses infect and kill many more people each year then highly publicized West Nile and SARS viruses.The influenza virus is the biggest killer virus worldwide.Pigs, chickens, ducks, and geese are the major reservoirs of flu. As they move from one species to another, they can mutate and exchange genetic material with other viruses.
12Viral DiseasesHIV is the second biggest killer virus worldwide. Five major priorities to slow the spread of the disease are:Quickly reduce the number of new infections to prevent further spread.Concentrate on groups in a society that are likely to spread the disease.Provide free HIV testing and pressure people to get tested.Implement educational programs.Provide free or low-cost drugs to slow disease progress.
13Case Study: Malaria – Death by Mosquito Malaria kills about 2 million people per year and has probably killed more than all of the wars ever fought.Figure 18-7
14Case Study: Malaria – Death by Mosquito Economists estimate that spending $2-3 billion on malaria treatment may save more than 1 million lives per year.Figure 18-6
15Case Study: Malaria – Death by Mosquito Spraying insides of homes with low concentrations of the pesticide DDT greatly reduces the number of malaria cases.Under international treaty enacted in 2002, DDT is being phased out in developing countries.
16Solutions Infectious Diseases Increase research on tropical diseases and vaccinesReduce povertyDecrease malnutritionImprove drinking water qualityReduce unnecessary use of antibioticsEducate people to take all of an antibiotic prescriptionReduce antibiotic use to promote livestock growthFigure 18.8Solutions: ways to prevent or reduce the incidence of infectious diseases, especially in developing countries. QUESTION: Which three of these approaches do you think are the most important?Careful hand washing by all medical personnelImmunize children against major viral diseasesOral rehydration for diarrhea victimsGlobal campaign to reduce HIV/AIDSFig. 18-8, p. 424
17Ecological Medicine and Infectious Diseases Mostly because of human activities, infectious diseases are moving at increasing rates from one animal species to another (including humans).Ecological (or conservation) medicine is devoted to tracking down these connections between wildlife and humans to determine ways to slow and prevent disease spread.
18CHEMICAL HAZARDSA toxic chemical can cause temporary or permanent harm or death.Mutagens are chemicals or forms of radiation that cause or increase the frequency of mutations in DNA.Teratogens are chemicals that cause harm or birth defects to a fetus or embryo.Carcinogens are chemicals or types of radiation that can cause or promote cancer.
19CHEMICAL HAZARDSA hazardous chemical can harm humans or other animals because it:Is flammableIs explosiveAn irritantInterferes with oxygen uptakeInduce allergic reactions.
20Effects of Chemicals on the Immune, Nervous, and Endocrine Systems Long-term exposure to some chemicals at low doses may disrupt the body’s:Immune system: specialized cells and tissues that protect the body against disease and harmful substances.Nervous system: brain, spinal cord, and peripheral nerves.Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream.
21Effects of Chemicals on the Immune, Nervous, and Endocrine Systems Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system.Figure 18-9
22Case Study: A Black Day in Bhopal, India The world’s worst industrial accident occurred in 1984 at a pesticide plant in Bhopal, India.An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas.15,000-22,000 people diedIndian officials claim that simple upgrades could have prevented the tragedy.
23TOXICOLOGY: ASSESSING CHEMICAL HAZARDS Factors determining the harm caused by exposure to a chemical include:The amount of exposure (dose).The frequency of exposure.The person who is exposed.The effectiveness of the body’s detoxification systems.One’s genetic makeup.
24TOXICOLOGY: ASSESSING CHEMICAL HAZARDS Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation.Figure 18-10
25TOXICOLOGY: ASSESSING CHEMICAL HAZARDS Estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved.Figure 18-11
26TOXICOLOGY: ASSESSING CHEMICAL HAZARDS Children are more susceptible to the effects of toxic substances because:Children breathe more air, drink more water, and eat more food per unit of body weight than adults.They are exposed to toxins when they put their fingers or other objects in their mouths.Children usually have less well-developed immune systems and detoxification processes than adults.
27TOXICOLOGY: ASSESSING CHEMICAL HAZARDS Under existing laws, most chemicals are considered innocent until proven guilty, and estimating their toxicity is difficult, uncertain, and expensive.Federal and state governments do not regulate about 99.5% of the commercially used chemicals in the U.S.
28Protecting Children from Toxic Chemicals The U.S. Environmental Protection Agency proposed that regulators should assume children have 10 times the exposure risk of adults to cancer-causing chemicals.Some health scientists contend that regulators should assume a risk 100 times that of adults.
29TOXICOLOGY: ASSESSING CHEMICAL HAZARDS Some scientists and health officials say that preliminary but not conclusive evidence that a chemical causes significant harm should spur preventive action (precautionary principle).Manufacturers contend that wide-spread application of the precautionary principle would make it too expensive to introduce new chemicals and technologies.
30RISK ANALYSISScientists have developed ways to evaluate and compare risks, decide how much risk is acceptable, and find affordable ways to reduce it.Figure 18-12
31RISK ANALYSISEstimating risks from using many technologies is difficult due to unpredictability of human behavior, chance, and sabotage.Reliability of a system is multiplicative:If a nuclear power plant is 95% reliable and human reliability is 75%, then the overall reliability is (0.95 X 0.75 = 0.71) 71%.
32RISK ANALYSISAnnual deaths in the U.S. from tobacco use and other causes in 2003.Figure 18-A
33RISK ANALYSISNumber of deaths per year in the world from various causes. Parentheses show deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors.Figure 18-13
34Perceiving RiskMost individuals evaluate the relative risk they face based on:Degree of control.Fear of unknown.Whether we voluntarily take the risk.Whether risk is catastrophic.Unfair distribution of risk.Sometimes misleading information, denial, and irrational fears can cloud judgment.
35RISK ANALYSISComparisons of risks people face expressed in terms of shorter average life span.Figure 18-14
36Becoming Better at Risk Analysis We can carefully evaluate or tune out of the barrage of bad news covered in the media, compare risks, and concentrate on reducing personal risks over which we have some control.Figure 18-3