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Chapter 18. Environmental Hazards and Human Health. 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.

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chapter 18

Chapter 18

Environmental Hazards and Human Health

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.
types of diseases

nontransmissible disease- Diseases not caused by living organisms cannot spread from one person to another

    • Heart disease, emphysema, asthma,
  • transmissible or infectious-while those caused by living organisms such as bacteria and viruses can spread from person to person
    • Flu, HIV, Malaria, Lyme, Hepatitis B
Types of diseases:
transmissible disease1

WHO estimates that each year the world’s seven deadliest infections kill 13.6 million people – most of them the poor in developing countries.

Transmissible Disease

Figure 18-5

hiv aids epidemic

WHO reported in 2005- 42 million (1.1 mill US) had HIV

  • No vaccine
  • Drugs are limited among poor
  • How does HIV affect humans?
  • Where did AIDS come from?
core 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.

  • News on AIDS
Core Case Study: The Global HIV/AIDS Epidemic

How does this age structure affect the economics of this country?

Figure 18-2

how would you vote

Should developed and developing nations mount an urgent global campaign to reduce the spread of HIV and to help countries afflicted by the disease?

    • a. No. A global AIDS campaign could divert attention and resources from efforts to combat other serious threats.
    • b. Yes. The disease is decimating the populations and destroying the economies of many developing countries.
How Would You Vote?
case study the growing global threat from tuberculosis

Recent increases

in TB are due to:

    • Lack of TB screening and control programs
    • Genetic resistance to the most effective antibiotics.
    • Population growth, urbanization, air travel
    • More AIDS which weakens immune system
Case Study: The Growing Global Threat from Tuberculosis
most dangerous viral diseases

Flu, HIV, and hepatitis B viruses infect and kill many more people each year then highly publicized West Nile and SARS viruses.

  • 1918 Spanish Flu
  • Hepatitis B is a virus that attacks your liver which is your natural filter of toxins
Most Dangerous Viral Diseases
case 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.

Case Study: Malaria – Death by Mosquito

Figure 18-7

reducing chances of malaria

Spraying insides of homes with low concentrations of the pesticide DDT greatly reduces the number of malaria cases.

  • Draining swamps
  • Insecticides
  • Sleep nets/screen doors
  • Drugs to victims
Reducing Chances of Malaria
growing germ resistance

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.
Growing Germ Resistance


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

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

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.
      • Ex. Radiation exposure, sunlight
    • Teratogens are chemicals that cause harm or birth defects to a fetus or embryo.
      • Ex. Pregnant women drinking alcohol
    • Carcinogens are chemicals or types of radiation that can cause or promote cancer.
      • Ex. Cigarette smoke, Arsenic
effects 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.
Effects of Chemicals on the Immune, Nervous, and Endocrine Systems
effects of chemicals on the immune nervous and endocrine systems1

Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system.

Effects of Chemicals on the Immune, Nervous, and Endocrine Systems

Figure 18-9

bhopal india

The world’s worst industrial accident occurred in 1984 at a pesticide plant.

    • 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 and there are still people suffering today
Bhopal, India
toxicology 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.
helpful vocab related to harm on a individual caused by a substance

Solubility- fat soluble substances (nonpolar) accumulate in cells

  • Persistence- resist breaking down
  • Bioaccumulation- molecules absorb and store in specific organs/tissues
  • Biomagnification- as you move up the food chain/web there is more of the toxin
Helpful vocab. Related to harm on a individual caused by a substance
who toxins affect

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

Who toxins affect…

Figure 18-10

how do we reduce the harmful effects of toxins

Break down and excrete

  • Enzymes repair damaged DNA
  • Cells reproduce and replace damaged areas
How do we reduce the harmful effects of toxins?
what are children more susceptible to toxins

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.
What are children more susceptible to toxins?
toxicology assessing chemical hazards1

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.
prevention vs reaction

Some scientists and health officials say that preliminary but not conclusive evidence that a chemical causes significant harm should spur preventive action (precautionary principle).

Prevention vs. Reaction
risk analysis

Scientists have developed ways to evaluate and compare risks, decide how much risk is acceptable, and find affordable ways to reduce it.


Figure 18-12

risk analysis2

Number 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

becoming 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.

Becoming Better at Risk Analysis

Figure 18-3

environmental changes and diseases

Global Warming warmer temps for more mosquitos survivingMalaria

  • Deforestation bats Nipah virus and pigs humans
  • Deforestation less fox more mice  more ticks Lyme
Environmental Changes and Diseases