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Environmental Hazards and Human Health

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Title: Environmental Hazards and Human Health


1
Environmental Hazards and Human Health
  • Chapter 17

2
17-1 What Major Health Hazards Do We Face?
  • Concept 17-1 People face health hazards from
    biological, chemical, physical, and cultural
    factors, and from the lifestyle choices they
    make.

3
Risks Are Usually Expressed as Probabilities
  • Risk a measure of the likelihood that you will
    suffer harm from a hazard (something that has the
    potential to cause harm)
  • Possibility it COULD happen
  • Probability how likely it is to happen
  • We can suffer from
  • Biological hazards from more than 1,400
    pathogens
  • Chemical hazards in air, water, soil, and food
  • Physical hazards fire, earthquake, volcanic
    eruption
  • Cultural hazards smoking, poor diet, unsafe sex,
    drugs, unsafe working conditions, and poverty
  • Lifestyle choices smoking, overeating,
    alcohol/drug abuse

4
17-2 What 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 developing
    countries.

5
17-2 What Types of Biological Hazards Do We Face?
  • Sources of biological hazards include bacteria,
    viruses, insects, plants, birds, animals, and
    humans.
  • These sources can cause a variety of health
    effects ranging from skin irritation and
    allergies to infections (e.g., tuberculosis,
    AIDS), cancer and so on.
  • This symbol is generally used as a warning, so
    that those potentially exposed to the substances
    will know to take precautions.

6
Some Diseases Can Spread from One Person to
Another
  • Nontransmissible disease not caused by living
    organisms and cannot spread from one person to
    another
  • Heart disease, cancer, asthma, diabetes
  • Infectious disease caused by living organisms
    such as bacteria and viruses
  • Malaria, tuberculosis, measles
  • Transmissible (contagious or communicable
    disease) it can be spread from person to person
  • Influenza, HIV

7
The Worlds Seven Deadliest Infectious Diseases
Kill 12.5 Million People Each Year
  • WHO estimates that the worlds seven deadliest
    infections kill 12.5 million people a year
    (34,200/day)
  • Most deaths are poor people in developing
    countries
  • Most deaths are preventable

8
Infectious Diseases Are Still Major Health
Threats
  • Since 1950, death from infectious diseases have
    declined due to
  • Better health care
  • Antibiotics
  • Vaccines
  • Infectious diseases spread through air, water,
    food, body fluids
  • Epidemic large scale outbreak of an infectious
    disease in an area or a country
  • Pandemic a global epidemic

9
Science FocusGenetic Resistance to Antibiotics
Is Increasing
  • Infectious bacteria are becoming genetically
    resistant to widely used antibiotics due to
  • Genetic resistance the few bacteria that
    survives the antibiotics are stronger and more
    able to resist the antibiotics in the future
    population evolves.
  • Overuse of antibiotics A 2000 study found that
    half of the antibiotics used to treat humans were
    prescribed unnecessarily.
  • Other factors
  • Rapid spread of bacteria around the world by
    human travel
  • Overuse of pesticides (crops) and antibiotics
    (livestock)

10
Some Viral Diseases Kill Large Numbers of People
  • Viruses are not treatable with antibiotics.
  • Influenza, 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.

11
Some Viral Diseases Kill Large Numbers of People
  • Acquired immune deficiency syndrome (AIDS) caused
    by human immunodeficiency virus (HIV) is the
    second biggest killer virus worldwide.
  • Kills 2.1 million people a year (25 million so
    far)
  • 2.5 million newly infected people a year
  • Virus itself doesnt kill you
  • Weakened immune system
  • Killed by a secondary infection
  • No vaccine to prevent or cure AIDS
  • Expensive, anti-viral drugs
  • Live longer

12
Case Study Malaria Death by Parasite-Carrying
Mosquitoes
  • Malaria
  • Caused by Plasmodium sp. carried by Anopheles
    mosquitoes
  • It infects and destroys red blood cells, intense
    fever, abdominal pains, vomiting, headaches
  • Malaria on the rise since 1970
  • Drug resistant Plasmodium
  • Insecticide resistant mosquitoes
  • Effect of global warming
  • AIDS patients particularly vulnerable

13
Solutions Infectious Diseases, Ways to Prevent
or Reduce Their Occurrence
14
17-3 What Types of Chemical Hazards Do We Face?
  • 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.

15
17-3 What Types of Chemical Hazards Do We Face?
  • A toxic chemical can cause temporary or permanent
    harm or death.
  • A hazardous chemical is a chemical that is
    flammable, explosive, or one that irritates the
    eyes, skin or lungs.
  • Chemical hazard labels indicate specific risks
  • Scale from 0 (no risk) to 4 (highest risk)

16
Some Chemicals Can Cause Cancers, Mutations, and
Birth Defects
  • Mutagens chemicals or forms of radiation that
    cause or increase the frequency of mutations
    (changes) in DNA.
  • UV radiation, radioactive decay, bromine
  • Teratogens chemicals that cause harm or birth
    defects to a developing fetus or embryo.
  • ethyl alcohol, lead, mercury, phthalates,
    thalidomide
  • Carcinogens chemicals or types of radiation
    that can cause or promote cancer.
  • benzene, PCBs, radon, MANY chem. in cigarette
    smoke

17
Some Chemicals May Affect Our Immune, Nervous,
and Endocrine Systems
  • Long-term exposure to some chemicals at low doses
    may disrupt the bodys
  • Immune system specialized cells and tissues that
    protect the body against disease and harmful
    substances
  • Nervous system brain, spinal cord, and
    peripheral nervous system
  • Endocrine system complex network of glands that
    release minute amounts of hormones into the
    bloodstream

18
Some Chemicals May Affect Our Immune, Nervous,
and Endocrine Systems
  • Hormonally active agents (HAAs) are a class of
    chemical that mimic the bodys natural hormones
  • Disrupt growth, metabolism, and reproduction
  • Hormone blockers
  • Gender benders
  • Thyroid disrupters

19
Science Focus Mercurys Toxic Effects
  • Mercury is a teratogen and potent neurotoxin
  • Interferes with nervous system and brain function
  • Once airborne, persistent and not degradable
  • 1/3 from natural sources
  • 2/3 from human activities
  • Enters the food chain biomagnification
  • How are humans exposed?
  • Inhalation vaporized Hg or particulates of
    inorganic salts
  • Eating fish with high levels of methylmercury

20
Cycling of Mercury in Aquatic Environments
21
Solutions Mercury Pollution
22
Case Study A Black Day in Bhopal, India
  • The worlds 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
  • Indian officials claim that simple upgrades could
    have prevented the tragedy.

23
17-4 How Can We Evaluate and Deal with Chemical
Hazards?
  • 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.

24
Many Factors Determine the Harmful Health Effects
of a Chemical
  • Toxicity how harmful a substance can beits
    ability to cause injury, illness, death.
  • Factors determining the harm caused by exposure
    to a chemical include
  • Dose the amount of a substance that has been
    inhaled, ingested, or absorbed
  • High dosage, low dosage
  • Frequency of exposure how often does it occur
  • Frequent, infrequent
  • Length of exposure how long the exposure lasts
  • Short-term, long-term

25
Many Factors Determine the Harmful Health Effects
of a Chemical
  • Age is an important factorvery young and/or very
    old are much more at risk.
  • Ones genetic makeup also influences ones
    sensitivity to a toxic chemical.
  • A related factor is how well the bodys
    detoxification system (liver, kidneys lungs)
    works.

26
Many Factors Determine the Harmful Health Effects
of a Chemical
  • The properties of the chemical can also determine
    the harm caused
  • Solubility
  • Water-soluble can move throughout our
    environment, water supply, and bodies
  • Fat-soluble can penetrate our bodys membranes
    and can be stored in our tissues
  • Persistence its resistance to be broken down
  • How long does it stay in an active for in the
    environment

27
Many Factors Determine the Harmful Health Effects
of a Chemical
  • Certain chemical interactions can either increase
    or decrease the harmful effects of a toxin
  • Antagonistic interaction certain vitamins or
    minerals can reduce the harm done by some kinds
    of toxic chemicals
  • Synergistic interaction certain chemicals can
    increase the negative effects of other chemicals
  • The two chemicals together can be worse than
    either one of them separately

28
Many Factors Determine the Harmful Health Effects
of a Chemical
  • Other related terms
  • Bioaccumulation the tendency to be absorbed and
    stored within certain tissues or organs
  • Low concentrations over long periods of time can
    become high levels in particular tissues
  • Biomagnification the accumulation of chemicals
    as they pass through the food chain
  • Organisms at the top of the food chain have
    higher levels of toxins in their tissues

29
Estimating Human Exposure to Chemicals and
Measuring Their Effects
  • Estimating human exposure to chemicals and their
    effects is very difficult because of the many and
    often poorly understood variables involved.

30
Many Factors Determine the Harmful Health Effects
of a Chemical
  • Response the type and amount of health damage
    done by exposure to toxic chemicals
  • Acute exposure short duration or single event
    exposure
  • Chronic exposure repeated, or continuous
    exposure over extended periods of time (or a
    lifetime)
  • Acute effect an immediate, rapid, and
    reversible response to exposure that is usually
    brief and low dosage
  • dizziness, coughing, vomiting, irritated eyes
  • Chronic effect a permanent or long lasting
    consequence from an exposure that is either high
    dosage or long-term
  • kidney or liver damage, damage to central nervous
    system, cancer, or death

31
Case Study Protecting Children from Toxic
Chemicals
  • 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.
  • Childrens developing bodies (especially the
    nervous system) are more susceptible to damage
    done by chemicals.

32
Scientists Use Live Lab Animals and Non-animal
Tests to Estimate Toxicity
  • Dose-response curve plotting the toxicity of a
    test chemical on certain organisms (usually rats
    or mice)
  • Median lethal dose (LD50) the dose that can
    kill 50 of the animals tested
  • Median lethal concentration (LC50) the
    concentration that can kill 50 of the animals
    tested

33
Why Do We Know So Little about the Harmful
Effects of Chemicals?
  • Under existing laws, most chemicals are
    considered innocent until proven guilty, and
    estimating their toxicity is difficult,
    uncertain, and expensive.
  • Toxicologists know a great deal about a few
    chemicals, a little about many, and next to
    nothing about most.
  • 100,000 registered synthetic chemicals
  • 10 thoroughly screened for toxicity
  • 2 tested for carcinogen, teratogen, or mutagen
    determination
  • Federal and state governments do not regulate
    about 99.5 of the commercially used chemicals in
    the U.S.

34
Pollution Prevention and the Precautionary
Principle
  • Some scientists and health officials say that
    preliminary but not conclusive evidence that a
    chemical causes significant harm should spur
    preventive action (precautionary principle).
  • A new product is considered harmful until it can
    be proved to be safe
  • Manufacturers contend that wide-spread
    application of the precautionary principle would
    make it too expensive to introduce new chemicals
    and technologies.

35
17-5 How Do We Perceive Risks and How Can We
Avoid the Worst of Them?
  • Concept 17-5 We can reduce the major risks we
    face if we become informed, think critically
    about risks, and make careful choices.

36
Comparative Risk Analysis Most Serious
Ecological and Health Problems
37
The Greatest Health Risks Come from Poverty,
Gender, and Lifestyle Choices
  • 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.

38
Number of Deaths per Year in the World from
Various Causes
  • Number of deaths per year in the world from
    various causes. Red numbers show deaths in terms
    of the number of fully loaded 200-passenger jumbo
    jets crashing every day of the year with no
    survivors.

39
Comparison of Risks People Face in Terms of
Shorter Average Life Span
  • Comparisons of risks people face expressed in
    terms of shorter average life span.

40
Annual Deaths in the U.S. from Tobacco Use and
Other Causes in 2004
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