Environmental Issues from the Scientific Perspective

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Environmental Issues from the Scientific
Perspective
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The Scientific Perspective

• The DOSE makes the POISON.
• Hazardous vs. Toxic
• Factors affecting persistence in environment
• Hydrophobicity
• Stability
• Detoxification mechanisms of organism

3
The Scientific Perspective

• Acute vs. Chronic
• Acute
• Single exposure, immediate response
• Chronic
• Single exposure, delayed response
• Multiple/continuous exposure (sublethal conc.)
• Long-term effects, usually irreversible
• LD50 and LC50

4
The Scientific Perspective

• General Anaesthetics reversible inhibition 70
  of chemicals
• Nonpolar narcotics
• Tox is directly proportional to hydrophobicity
• Reversible when substance removed
• More hydrophobic (to a pt), more persistent
• Toxic mechanism is a membrane event
• Easy to predict

5
The Scientific Perspective

• Specific Toxics irreversible inhibition 30
  of chemicals
• Intracellular event
• Two-step process
• Cross membrane (hydrophobicity)
• Bind to specific component inside cell such as
  mitochondria, DNA, etc. (molecular interaction)
• Harder to predict because of numerous mechanisms
  for 2nd step

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The Scientific Perspective

• Testing Systems/Risk Assessment
• Moving toward predictability based on chemical
  structure of toxicant
• QSAR quantitative structure-activity
  relationship
• y mx b
• simplest case NPNs, xhydrophobicity value,
  ytoxic endpoint measured

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The Scientific Perspective

• Finding articles in addition to those listed by
  Dr. OGorman
• MCQuest Search for Journal Literature
• Annual Reviews
• Biomedical sciences, Physical sciences
• BioOne
• search All
• JSTOR
• Ecology, Botany, General science
• Science hardcopies in current periodicals