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Chapter 15: Environmental Health, Pollution and Toxicology

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Title: Chapter 15: Environmental Health, Pollution and Toxicology


1
Chapter 15 Environmental Health, Pollution and
Toxicology
2
Diseases
  • Disease is often due to an imbalance between
    individuals and their environment.
  • Continuum from state of health to disease
  • Gray in-between zone between health and disease
  • As a result of exposure to chemicals in the
    environment we may be in the midst of an epidemic
    of chronic disease.

3
Diseases
  • Seldom have a one-cause- one-effect relationship
    w/ the environment
  • Depends on several factors
  • Physical environment
  • Biological environment
  • Lifestyle

4
Diseases
  • Chances of experiencing serious environmental
    health problems and disease depends on
  • The water we drink
  • The air we breathe
  • The soil we grow crops in
  • The rocks we build our homes on

5
Diseases
  • Natural processes can release harmful materials
    into the soil, water or air.
  • Lake Nyos in Cameroon, Africa
  • Experienced sudden release of carbon dioxide
  • Killed 1,800 people in near by town.

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Terminology
  • Pollution refers to the occurrence of unwanted
    change in the environment
  • introduction of harmful or toxic materials into
    the surroundings
  • Contamination
  • similar to that of pollution
  • implies making something unfit for a particular
    use through the introduction of toxic materials

9
Terminology
  • Toxic refers to materials (pollutants) that are
    poisonous to people and other living things.
  • Toxicology is the science that studies chemicals
    that are known to be or may be toxic based upon
    animal studies.
  • Carcinogen - a kind of toxin that increases the
    risk of cancer.
  • Most feared and regulated toxins in our society.

10
Terminology
  • Pollutants introduced into the environment two
    ways
  • Point sources - smokestacks, pipes discharging
    into waterways, stream entering the ocean, or
    accidental spills.
  • Area sources, (non point sources) more
    diffused over the land and include urban and
    agricultural runoff and mobile sources such as
    automobile exhaust. The sources are either
    moving or spread over a large area

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Measuring the Amount of Pollution
  • How the amount or concentration of a particular
    pollutant or toxin present in the environment is
    reported varies widely.
  • E.g. waste water reported in millions of gallons
  • Emissions of nitrogen oxides reported in tons per
    year
  • Others given by a volume, mass of weight
  • ppm, ppb, mg/kg or

13
Infectious Agents
  • Infectious disease
  • Spread by interactions between individuals and
    through food, water, air or soil.
  • Can travel globally via airplanes
  • New diseases emerging and previous ones
    reemerging
  • Some infectious diseases can be controlled by
    manipulating the environment

14
Environmentally Transmitted Infectious Diseases
  • Legionellosis
  • Occurs where air-conditioning systems have been
    contaminated by disease-causing organisms.
  • Giardiasis
  • a protozoan infection of the small intestine
    spread via food, water, or person-to-person
    contact. Spread by fecal material
  • Salmonella
  • a food-poisoning bacterial infection spread via
    water or food. Also found in enteric (
    intestinal) systems

15
Environmentally Transmitted Infectious Diseases
  • Malaria
  • a protozoan infection transmitted by mosquitoes.
    (Usually tropical areas)
  • Lyme disease
  • Transmitted by ticks.
  • Cryptosporidosis
  • a protozoan infection transmitted via water or
    person-to-person contact.
  • Anthrax
  • Bacterial infection spread by terrorist activity,
    though it is naturally occurring in agricultural
    areas where it is generally non-pathogenic

16
Toxic Heavy Metals
  • The major heavy metals that pose health hazards
    to people and ecosystems include
  • mercury, lead, cadmium, nickel, gold, platinum,
    silver, bismuth, arsenic, selenium, vanadium,
    chromium, and thallium.
  • Each may be found in soil and water not
    contaminated by humans, though they are also
    found in extreme environments such as deep sea
    vents and hot springs

17
Toxic Heavy Metals
  • Often have direct physiological effects.
  • Stored and incorporated in living tissue
  • Fatty body tissue
  • Content in our bodies referred to as body burden.
  • Central nervous system is often affected (Mercury
    and Lead))
  • Associated with birth defects as well

18
Toxic Pathways
  • Chemical elements can become concentrated
  • Biomagnification-
  • the accumulation or increase in concentration of
    a substance in living tissue as it moves through
    the food chain.
  • E.g. Cadmium, mercury are biomagnified

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Organic Compounds
  • Organic compounds
  • compounds of carbon produced naturally by living
    organisms or synthetically by human industrial
    practices.
  • Synthetic organic compounds
  • Used in industrial processes, pest control,
    pharmaceuticals, and food additives.
  • Over 20 million known compound though most are
    poorly characterized for their pathogenicity

22
Persistent Organic Pollutants
  • POPs may produce a hazard for decades or hundreds
    of years.
  • First produced when their harm was not known
  • Now banned or restricted
  • Commonly composed of plastics that are partially
    decomposed

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Persistent Organic Pollutants
  • POPs have several properties that define them
  • They have a carbon-based molecular structure,
    often containing highly reactive chlorine.
  • Most are synthetic chemicals.
  • They do not easily break down in the environment.

25
POPs
  • They are polluting and toxic.
  • Molecular forms are soluble in fat and likely to
    accumulate in living tissue.
  • They occur in forms that allow them to be
    transported by wind, water, and sediments for
    long distances.

26
Hormonally Active Agents (HAAs)
  • HAA are also POPs.
  • Have potential to cause developmental and
    reproductive abnormalities in animals, including
    humans.
  • Include a wide variety of chemicals, herbicides,
    pesticides, phthalates, and PCBs

27
Hormonally Active Agents
  • Evidence in support of hypothesis
  • Alligator populations in Florida exposed to DDT
    have genital abnormalities, low egg production
    and reduced penis size.
  • Major disorders studied in wildlife have centered
    on abnormalities including
  • thinning of eggshells of birds (DDT effect),
    decline in populations of various animals and
    birds, reduced viability of offspring, and
    changes in sexual behavior.

28
Hormonally Active Agents
  • In humans
  • HAAs may be linked to breast cancer
  • PCBs and neurological behavior
  • Phthalates and endocrine and hormone disruption

29
Endocrine System
  • One of two main systems that regulate and control
    growth, development, and reproduction in animal
    systems
  • Composed of a group of hormone secreting glands
  • Thyroid, pancreas, pituitary, ovaries and testes.
  • Hormones transported by blood stream, act as
    chemical messengers.

30
Radiation
  • Nuclear radiation is linked to serious health
    problems
  • Including cancer, as well as acute radiation
    poisoning. Exposure may be chronic as exposure
    over long periods of time, or acute as
    shorter/lethal exposure

31
Thermal Pollution
  • Occurs when heat released into water or air
    produces undesirable effects.
  • Also called heat pollution
  • Sudden acute event or long term, chronic
    release
  • Heated water released into rivers changes temp
    and dissolved oxygen content (Nuke reactor
    coolant)
  • Thereby changing rivers species composition

32
Thermal Pollution
  • Heating river water changes natural conditions
    and disturbs the ecosystem
  • Fish spawning cycles may be disrupted
  • Fish may have heightened susceptibility to
    disease.
  • Physical stress on fish
  • Easier prey
  • Change in type and availability of food

33
Thermal Pollution
  • Solutions to chronic thermal heating
  • Release of heat into air in cooling towers
  • Artificial lagoons
  • Used to heat buildings (this makes a lot of sense
    in the winter, but what about summers?)

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Particulates
  • Small particles of dust released into the
    atmosphere by many natural processes and human
    activities.
  • Modern farming
  • Burning oil and coal
  • Dust storms
  • Volcanic eruptions
  • Graineries

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Asbestos
  • A term for several minerals that take the form of
    small, elongated particle or fibers.
  • Fire prevention contributed to their use
  • Insulation
  • Inhalation leads to asbestosis and cancer
  • 95 of asbestos now in use in US is chrysolite
    (white asbestos).
  • Not particularly harmful
  • Another type crocidolite (blue asbestos)
  • Exposure can be very hazardous

39
Electromagnetic Fields
  • EMFs part of everyday urban life
  • electric motors, transmission lines and
    appliances
  • Controversy as to whether they pose a health risk
    (Is it really safe to stand next to Microwave
    ovens while theyre in use?)
  • Children may be at greater risk
  • Consensus is not possible yet on risk evaluation

40
Noise Pollution
  • Unwanted sound
  • Sound is a form of energy that travels as waves
  • We hear sounds when waves vibrate our eardrum
  • Loudness a measure of intensity of energy
  • Measured in units of decibels (logrithmic scale
    1?2 is a 10X difference)

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Noise Pollution
  • Environmental effects of noise depend on
  • Energy
  • Pitch
  • Frequency
  • Time pattern
  • Length of exposure
  • Very loud noise can cause pain
  • Any sound above 80dB can cause hearing loss
  • - How do we decide what is pleasant Vs pain?

43
Voluntary Exposure
  • Sometimes referred to as exposure to personal
    pollutants.
  • Tobacco
  • 30 of cancers tied to smoking
  • Alcohol and other drugs
  • ½ of all deaths in automobiles accidents tied to
    alcohol use by drivers
  • Violent crimes, overdoses, chronic alcoholism

44
General Effect s of Pollutants
  • Almost every part of the human body is affected
    by one pollutant or another.

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Concept of Dose and Response
  • Five centuries ago, the physician and alchemist
    Paracelsus wrote that everything is poisonous,
    yet nothing is poisonous.
  • For Example
  • Selenium required in small amounts by living
    things
  • May be toxic in high concentrations

49
Concept of Dose and Response
  • The effect of a chemical on an individual depends
    on the dose.
  • Dose response
  • Dose dependency can be represented by a
    generalized dose response curve.

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Concept of Dose and Response
  • Doses that are beneficial, harmful, or lethal may
    differ widely for different organisms and are
    difficult to characterize.
  • E.g. fluoride and dental health
  • Fluorine forms fluoride compounds that prevent
    tooth decay and promote healthy bone structure.
  • Toxic effects are noticed at concentrations of
    6-7 ppm

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Dose-Response Curve
  • How individuals will respond to a chemical is not
    known. Therefore..
  • Instead predictions are made about how a
    percentage of the population will respond to a
    specific dose.
  • Dose at which 50 of the population dies
  • Lethal dose 50, LD-50 is used as a generalized
    zone where we expect to see toxicity among a
    population

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Dose-Response Curve
  • The ED-50 (effective dose 50) is the dose that
    causes an effect in 50 of the population of
    observed subjects.
  • E.g. ED-50 of aspirin would be the dose that
    relieves headaches in 50 of the people.

56
Dose-Response Curve
  • The TD-50 (toxic dose 50) is defined as the dose
    that is toxic to 50 of the population.
  • Often used to indicate responses such as reduced
    enzyme activity, decreased reproductive success,
    or onset of specific symptoms.

57
Dose-Response Curve
  • For a particular chemical, there may be a whole
    family of doseresponse curves.
  • Which dose is of interest depends on what is
    being evaluated.
  • Killing insects vs. pesticide residue effect on
    birds
  • Overlap between the therapeutic dose (ED) and the
    toxic dose (TD)
  • Measure of the relative safety of a particular
    drug is the therapeutic index
  • Defined as the ratio of the LD-50 to the ED-50.
  • The greater the therapeutic index, the safer the
    drug.

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Threshold effects
  • Threshold is a level below which no effect occurs
    and above which effects begin to occur.
  • If a threshold exists, then a concentration below
    the threshold is safe.
  • If there is no threshold dose, then even the
    smallest amount has some negative toxic effect.
    (Dioxin?)
  • A problem in evaluating thresholds for toxic
    pollutants is that it is difficult to account for
    synergistic effects, especially at low
    concentrations

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Ecological Gradients
  • Changes in vegetation with distance from a toxic
    source define the ecological gradient.
  • Weedy species adapted to harsh conditions may be
    closer because they are annuals often and develop
    resistance sooner than other plant groups
  • Farther away, trees and shrubs may be able to
    grow

62
Tolerance
  • The ability to resist or withstand stress
    resulting from exposure to a pollutant or harmful
    condition.
  • Result from behavioral, physiological, or genetic
    adaptation.

63
Tolerance
  • Physiological tolerance- the body of an
    individual adjusts to tolerate a higher level of
    pollutant.
  • Many mechanisms including detoxification
  • the toxic chemical is converted to a nontoxic
    form (Ethanol consumption among humans)
  • Internal transport of the toxin to a part of the
    body where it is not harmful, such as fat cells.

64
Tolerance
  • Genetic tolerance- (adaptation) when some
    individuals in a population are naturally more
    resistant to a toxin than others.
  • Strains of mosquitoes resistance to DDT
  • Antibiotic resistance

65
Acute and Chronic Effects
  • Acute effects occur soon after exposure.
  • Usually to large amounts of a pollutant or
    pathogen
  • Chronic effects takes place over a long period
  • Often as a result of exposure to low levels of
    pollutant (asbestos, smoking, coal mining)

66
Risk Assessment
  • The process of determining potential adverse
    environmental health effects to people exposed to
    pollutants and potentially toxic materials.

67
Risk Assessment
  • Such an assessment generally includes four steps
  • Identification of the hazard.
  • Doseresponse assessment.
  • Exposure assessment.
  • Risk characterization.
  • Risk assessment is difficult, costly, and
    controversial.
  • Risk management integrates the assessment of risk
    with technical, legal, political, social, and
    economic issues so companies/businesses often
    weigh the economic gain against the potential
    loss due to risk of exposure to product or its
    manufacturing process.
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