Eg: Tuberculosis

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Eg Tuberculosis
Deforestation causes insect vectors to move to
cities
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Morbidity and Quality of Life

• Death rates do not tell everything about burden
  of disease.
• Total economic and social consequences of
  diseases are difficult to obtain.
• Disability-Adjusted Life Year (DALY) combines
  premature deaths and loss of healthy life
  resulting from illness or disability.

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Elephantiasis caused by parasitic worm
At any given time, about 2 billion people suffer
from worms, protozoans, and other internal
parasites.
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Emergent Diseases

• An emergent disease is one never known before, or
  has been absent for at least 20 years.
• An important factor in the spread of many
  diseases is speed and frequency of modern travel.
• Foot and Mouth Disease
• Ebola

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Emerging Ecological Diseases

• Domestic animals and wildlife also experience
  sudden and widespread epidemics.
• Distemper (Seals)
• Chronic Wasting Disease (Deer and Elk)
• Transmissible Spongiform Encephalopathies
• Black Band Disease (Coral)

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Recent outbreaks of lethal infectious diseases
At least 30 new infectious diseases have appeared
in the past two decades while many well-known
have reappeared in more virulent, drug-resistant
forms.
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Factors Contributing to the Spread of Contagious
Diseases

• High population densities
• Settlers pushing into remote areas
• Human-caused environmental change (use of
  fertilizers, pesticides etc)
• Speed and frequency of modern travel
• Contact with water or food contaminated with
  human waste

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Antibiotic and Pesticide Resistance

• Indiscriminate use of antibiotics and pesticides
  - perfect recipe for natural selection
• Protozoan that causes malaria now resistant to
  most antibiotics, and mosquitoes have developed
  resistance to many insecticides
• Drug resistance TB, Staph A, flesh-eating
  bacteria

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Toxins Movement, Distribution, Fate
Movement, fate of chemicals in the environment
(processes that modify, remove or sequester
compounds)
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Toxins Movement, Distribution, Fate
Movement via Solubility - water - oil
Routes by which chemicals enter body determine
toxicity
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Bioaccumulation and Biomagnification

• Bioaccumulation selective absorption storage
  of molecules dilute toxins in the environment
  can reach dangerous levels inside cells and
  tissue
• Biomagnification - the effects of toxins are
  magnified through food webs

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DDT - Powerful Insecticide, Harmless to Humans
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Peregrine falcons disappeared from the eastern US
in 1960s due to excess pesticide use
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Minimizing Toxic Effects

• Every material can be poisonous under some
  conditions
• Taken in small doses, most toxins can be broken
  down or excreted before they do much harm
  belief in 1800s, arsenic (Napolean)
• Liver - primary site of detoxification
• Tissues and organs - high cellular reproduction
  rates replace injured cells - down side tumors,
  cancers possible

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Measuring Toxicity
Animal Testing

• Most commonly used and widely accepted
• Expensive - hundreds of thousands of dollars to
  test one toxin at low doses
• Time consuming
• Often very inhumane
• Difficult to compare toxicity of unlike chemicals
  or different species of organisms

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A Typical Dose/Response Curve
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LD50 - the dose of a toxin that is lethal to
half the test population
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Acute Lethal Doses for Some Toxic Organic
Chemicals
mouse
rat
It is useful to group materials according to
their relative toxicity.
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Acute Versus Chronic Doses and Effects

• Acute effect - immediate health effect caused by
  a single exposure to a toxin (can be reversible)
• Chronic effect - long lasting or permanent health
  effect caused by (1) a single exposure to a very
  toxic substance or (2) continuous or repeated
  sublethal exposure to a toxin

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Risk Assessment and Acceptance

• Risk - the probability of harm times the
  probability of exposure
• A number of factors influence how we perceive
  relative risks associated with different
  situations.
• Accepting risks - we go to great lengths to avoid
  some dangers, while gladly accepting others

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Mckinney Schoch
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Establishing Public Policy
In setting standards for environmental toxins,
we need to consider

• Combined effects of exposure to many different
  sources of damage
• Different sensitivities of members of the
  population
• Effects of chronic as well as acute exposures

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Regulatory Decisions EPA framework
Other Factors Not Specific to the Problem
The Science Specific to the Problem
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• How do we determine what the risk is from
  different physical/ chemical changes in the
  environment?
• How much of the ranking is based on our values
  do they reflect the science?

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Summary

• Environmental Health Hazards
• Infectious Organisms
• Emergent Diseases
• Antibiotics and Pesticide Resistance
• Toxic Chemicals
• Distribution and Fate of Toxins
• Minimizing Toxic Effects
• Measuring Toxicity
• Risk Assessment
• Public Policy