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Chap 18 Environmental Hazards & Human Heath

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1 Chap 18 Environmental Hazards & Human Heath

2 RISKS AND HAZARDS Risk 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.

3 RISKS AND HAZARDS Risk is a measure of the likelihood that you will suffer harm from a hazard. Distinguish between Possibility Probability Risk assessment Scientific process to estimate harm Risk management How to reduce risk levels

4 Hazard identification Comparative risk analysis
Risk Assessment Risk Management Hazard identification Comparative risk analysis What 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 reduction strategy How will the risk be reduced? Figure 18.3 Science: risk assessment and risk management. Consequences of risk Financial commitment What is the likely damage? How much money should be spent? Fig. 18-3, p. 419

5 DISEASE Transmissible or infectious diseases Nontransmissible disease
Caused by living organisms such as bacteria and viruses Can spread from person to person Flu, strep throat, mono Nontransmissible disease Not caused by living organisms Can not spread from one person to another Heart disease, asthma

6 Transmissible Disease
Pathway for infectious disease in humans. Figure 18-4

7 Transmissible 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

8 Vocabulary Endemic Mortality Morbidity Disease Vector Epidemic
Pandemic Acute Chronic Synergistic

9 Vocabulary Endemic – native to area Mortality – rate of death
Morbidity – rate of sickness or ill effect Disease Vector – transmits disease through bite Epidemic – large outbreak in one area or country Pandemic – global outbreak Acute – immediate, usually brief & severe Chronic – long duration, usually less severe Synergistic – combined effect is greater than sum of individual effects.

10 Genetic Resistance to Antibiotics
Bacteria reproduce quickly: up to 16 million offspring in 24 hours Can quickly become resistance through natural selection & exchanging genetic material International travel and global trade Over use of pesticides: increases resistance in disease carrying pests Over use of antibiotics in humans and livestock Over ½ prescribed unnecessarily

11 Case Study: The Growing Global Threat from Tuberculosis
Tuberculosis (TB) – highly infectious. Kills 1.7 million people per year and could kill 25 million people Recent increases in TB are due to: Lack of TB screening and control programs especially in developing countries due to cost. Genetic resistance to the most antibiotics. In US Health dept investigates new cases Requires compliance: 6 months drug therapy

12 Viral Diseases – Big 3 Flu, HIV / AIDS hepatitis B
infect and kill many more people each year then highly publicized West Nile and SARS viruses.

13 Flu 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.

14 Highly Potent Flu Strains
Some strain more virulent than others – can kill 80% of infected Spanish Flu – killed 50 million Asian Flu (1957) & Hong Kong Flu(1968) – killed 1 million each Bird and Swine Flu more recently New strain could kill 2 – 360 million people Only a matter of time

15 The Global HIV/AIDS Epidemic
According to World Health Organization (WHO), in 2005 about 42 million people worldwide (1.1 million in the U.S.) were infected with HIV. By 2005, 25 million deaths Each year: 3 million more deaths

16 HIV/AIDS Epidemic AIDS has reduced the life expectancy of sub-Saharan Africa from 62 to 47 – 40 years in the seven countries most severely affected by AIDS. Lose ½ adult pop in 10 yrs 15 million AIDS orphans Projected age structure of Botswana's population in 2020…dramatically altered population pyramid Figure 18-2

17 HIV/AIDS The virus itself is not deadly, but it cripples the immune system, leaving the body susceptible to infections such as Kaposi’s sarcoma (above). 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.

18 HIV / AIDS HIV 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.

19 Hepatitis B (HBV) Damages liver Kills 1 million/yr Transmitted
Jaundice: liver can’t remove bilirubin Kills 1 million/yr Transmitted Body fluids, Tattoes Drug needles Mother to child

20 Emerging Viral Diseases
SARS Outbreak in China 2002 Severe acute respiratory syndrome Spreads quickly Life threatening pneumonia West Nile Recent increase in TX Arial spraying for mosquitoes Most people never even know they had it 2004: flu killed 36,000 west nile killed 100

21 Malaria – Death by Mosquito
Malaria kills about 2 million people per year Majority that die are children Killed more than all of the wars ever fought. Figure 18-7

22 Malaria – Death by Mosquito
Cycles of Fever, chills, sweating Weakness Coma Can relapse Many survivors: permanently impaired

23 Malaria – Death by Mosquito
Cases had declined during 1950’s and 60’s Since 1970’s: come roaring back DDT banned Mosquitoes: Increased resistance to pesticides currently used Parasites (Plasmodium): Increased resistance to antimalarial drugs Climate change: increasing range

24 Malaria – Death by Mosquito
No vaccine Prevention key Window screens, bed nets, clear vegetation, standing water, larva eating fish 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. Take prophylactic medicine if traveling to endemic areas

25 Malaria – Death by Mosquito
40% of world’s pop live in area where malaria is prevalent

26 Infectious Diseases Majority of children in develop nations are vaccinated Tenanus Measles Diphtheria Typhoid fever Meningitis Polio Pertussis Cases have been increasing due to more parents not vaccinating Access to healthcare / cost Autism scare Studies have shown no correlation Fewer vaccinated = increased risk for all

27 Ecological Medicine and Infectious Diseases
infectious diseases are moving across species at increasing rates AIDS: tribesmen eating bush meat (chimps) Mad Cow: feeding sheep parts to cows Lyme disease, hantavirus, SARS, swine/bird flu Caused by crowding, resistance, global trade, poverty, malnutrition, habitat destruction Ecological (conservation) medicine tracks down these connections between wildlife and humans to determine ways to slow and prevent disease spread.

28 Solutions Infectious Diseases
Increase research on tropical diseases and vaccines Reduce poverty Decrease malnutrition Improve drinking water quality Reduce unnecessary use of antibiotics Educate people to take all of an antibiotic prescription Reduce antibiotic use to promote livestock growth Figure 18.8 Solutions: 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 personnel Immunize children against major viral diseases Oral rehydration for diarrhea victims Global campaign to reduce HIV/AIDS Fig. 18-8, p. 424

29 CHEMICAL HAZARDS Toxic chemical can cause temporary or permanent harm or death A hazardous chemical can harm humans or other animals because it: Is flammable Is explosive An irritant Interferes with oxygen uptake Induce allergic reactions.

30 CHEMICAL HAZARDS A 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.

31 Effects of Chemicals on the Immune, Nervous, and Endocrine Systems
Long-term exposure to some chemicals at low doses may disrupt the body’s systems: Immune system: Nervous system: Endocrine system:

32 Immune System specialized cells and tissues that protect the body against disease and harmful substances. (arsenic, dioxins) Disrupting would leave body vulnerable to infection Arsenic & dioxins

33 Nervous System brain, spinal cord, neurons, and peripheral nerves.
Damage can cause: behavior changes, learning disabilities, retardation, attention deficit disorder, paralysis, death Neurotoxins: PCBs, Mercury, arsenic, lead, some pesticides

34 Endocrine System Complex network of glands that release hormones into the bloodstream. These hormones control metabolism, growth, sexual production, learning ability, behavior Chemicals can mimic our natural hormones and impair correct function Problems include: gender bender, thyroid, brain, growth, behavior disorders, cancer, birth defects Bisphenol-A (BPA) & Phthalates: leach from plastics – found in 95% of Americans DDT, PCBs, atrazine, aluminum, mercury

35 Effects onEndocrine Systems
Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system. Figure 18-9

36 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 died 50,000 – 60,000 permanent serious injury: blindness, lung damage, neurological problems Indian officials claim that simple upgrades could have prevented the tragedy.

Toxicity is a measure of how harmful a substance is – depends on: The amount of exposure - dose The frequency of exposure - how often The person who is exposed - adult or child The effectiveness of the body’s detoxification systems - do your liver & kidneys work well One’s genetic makeup - some people have a higher sensitivity

Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation. Figure 18-10

39 Other Factors Solubility: Water or fat
Persistence: how long does it hang around in the environment Bioaccumulation – concentrated in tissue Biomagnification – concentration increases as you move up food chain (trophic levels) Chemical interactions: Antagonistic – reduces harm (antioxidents) Synergistic – increases harm (2+2=5)

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.

41 Protecting 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.

42 Dose is the poison Any substance, natural or synthetic, can be harmful if ingested in large enough dose Water, salt Response: health damage from exposure Acute Chronic Should we be concerned with increasing number of chemicals all around us? Even at trace amounts We lack enough data to assess risk

43 Total health burden is difficult to quantify: Very complex model:
Water pollutant levels Air pollutant levels Soil/dust levels Food pesticide levels Total health burden is difficult to quantify: Very complex model: Many variables Nutritional health ? Mathematical measurements & modeling Overall health Lifestyle Figure 18.11 Science: estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved. QUESTION: Which three of these factors do you think make you more vulnerable to the harmful effects of chemicals? Predicted level of toxicant in people Personal habits Metabolism Genetic predisposition Accumulation Excretion Lung, intestine & skin absorption rates Fig , p. 431

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.

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.

46 Risk Analysis Risk assessment - identify
Comparative risk analysis - rank Risk management – plan to reduce risks Risk communication – inform public and policy makers

47 RISK ANALYSIS – World Cause of death Annual deaths 11 million (75)
Poverty/malnutrition/ disease cycle Tobacco 5 million (34) Pneumonia and flu 3.2 million (22) Air pollution 3 million (21) HIV/AIDS 3 million (21) Malaria 2 million (14) Diarrhea 1.9 million (13) Tuberculosis 1.7 million (12) Figure 18.13 Global outlook: number of deaths per year in the world from various causes. Numbers in parentheses give these deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors. Because of sensational media coverage, most people have a distorted view of the largest annual causes of death. QUESTION: Which three of these items are most likely to shorten your life span? (Data from World Health Organization) Car accidents 1.2 million (8) Work-related injury & disease 1.1 million (8) Hepatitis B 1 million (7) Measles 800,000 (5) Parentheses ( ) show deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors.

48 RISK ANALYSIS - US Annual deaths in the U.S. from tobacco use and other causes in 2003.

49 Perceiving Risk Most 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.

50 Assessing Risk People will do high risk things they enjoy:
Motorcycle: 1 death per 50 Driving: 1 death per 3,300 But will be terrified of low risk: Nuclear accident: 1 death in 200,000 Air plane crash: 1 death in 9 million

51 Hazard Shortens average life span in the U.S. by Poverty 7–10 years Born male 7.5 years Smoking 6–10 years Overweight (35%) 6 years Unmarried 5 years Overweight (15%) 2 years Spouse smoking 1 year Driving 7 months Air pollution 5 months Risk Analysis: Comparison of risks people face expressed in terms of shorter average life span. Alcohol 5 months Drug abuse 4 months Flu 4 months AIDS 3 months Drowning 1 month Pesticides 1 month Figure 18.14 Global outlook: comparison of risks people face, expressed in terms of shorter average life span. After poverty and gender, the greatest risks people face come mostly from the lifestyle choices they make. These are merely generalized relative estimates. Individual responses to these risks can differ because of factors such as genetic variation, family medical history, emotional makeup, stress, and social ties and support. QUESTION: Which three of these items are most likely to shorten your life span? (Data from Bernard L. Cohen) Fire 1 month Natural radiation 8 days Medical X rays 5 days Oral contraceptives 5 days Toxic waste 4 days Flying 1 day Hurricanes, tornadoes 1 day Lifetime near nuclear plant 10 hours Fig , p. 436

52 Risk Analysis & Management
1. Recognize everything is risky 2. Recognize media exaggerates risk 3. Compare risks rationally: nitrites can cause cancer, but an occasional hotdog will not be what kills you 4. Concentrate on most serious risks you can control Eat right, exercise, don’t smoke, drive safely, wear your seat belt, use sunscreen,

53 RISK ANALYSIS Comparisons of risks people face expressed in terms of shorter average life span. Figure 18-14

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