Chapter 8

Chapter 8: Environmental Health
and Toxicology
The Environment is Out to Kill You
8.1 Environmental Health
• The global disease burden is changing
• Infectious and emergent diseases still kill
millions of people
• Conservation medicine combines ecology and
health care
• Resistance to drugs, antibiotics, and pesticides
is increasing
• Who should pay for health care?
• Prions (Mad Cow, Kreuzfeld-Jacob)
• Viruses (Ebola, AIDS, smallpox, common
cold, influenza, herpes)
• Bacteria (cholera, typhoid, plague)
• Protista (malaria, sleeping sickness,
• Fungi (athlete’s foot, yeast infections,
• Multicellular Organisms (tapeworms,
trichinosis, schistosomes)
• Only known infectious agents without DNA
• Misconfigured protein molecules
• Bind to normal proteins and convert them to
misconfigured form
• All known prion diseases attack the brain
• No known cure; invariably fatal; very nasty
• Viruses are non-living but reproducing
• Viruses invade cells and use cell reproduction
mechanisms to reproduce
• Retroviruses permanently insert new DNA into
cell (AIDS)
• Viruses cannot be attacked in cells
• Being non-living, can’t be killed by antibiotics in
blood stream
• Only defenses are immunization or prevention
• Antibiotics do not work against viruses
Promiscuous Antibiotics
Used improperly against viral infections
Essentially given as placebos
Sugar pills would be more ethical
Legitimate users do not use properly
Used as prophylactic measure in factory
• Creation of resistant micro-organisms
• Waste antibiotics get into environment
8.2 Toxicology
• How do toxins affect us?
• What Can You Do? Tips for Staying Healthy
• How does diet influence health?
Chemical Hazards
• Allergens (trigger immune response)
• Neurotoxins (damage nervous system:
mercury, pesticides, lead)
• Mutagens (alter genes)
• Teratogens (cause birth defects: alcohol,
• Carcinogens (nickel, tobacco, radon)
• Hormone mimics (PCB’s)
8.3 Movement, Distribution, And Fate
Of Toxins
• Solubility and mobility determine where and
when chemicals move
• Exposure and susceptibility determine how we
• Bioaccumulation and biomagnification increase
concentrations of chemicals
• Persistence makes some materials a greater
• Chemical interactions can increase toxicity
8.4 Mechanisms For Minimizing Toxic
• Metabolic degradation and excretion
eliminate toxins
• Repair mechanisms mend damage
8.5 Measuring Toxicity
• We usually test toxins on lab animals
– “All that proves is rats shouldn’t smoke”
– Reality: Animal tests predict human toxicity well
• There is a wide range of toxicity
• Acute and chronic doses and effects differ
• Detectable levels aren’t always dangerous
– With enough equipment and money, we can
detect individual molecules
Response to Exposure
Response to Exposure
Chemicals in Concert
• Antagonistic (Vitamin A, E against carcinogens)
• Additive (Effects combine)
• Synergistic (Effects multiply: alcohol + drugs,
smoking + asbestos)
• Sensitization or Desensitization
Factors in Toxicity
Chemical composition
Acute versus Chronic Exposure
Solubility and Mobility
Nature of exposure
Ability to metabolize, sequester, or excrete
Tendency to bioaccumulate
General Health
8.6 Risk Assessment And Acceptance
• Risk perception isn’t always rational
• Risk acceptance depends on many factors
• Some 1:1,000,000 Risks
– Smoking 1.4 cigarettes (cancer, heart disease)
– Two days in large city (air pollution)
– 10 miles by bicycle (accident)
– 1000 miles by jet (accident)
– One chest X-ray (cancer)
– 5 years on boundary of nuclear plant (cancer)
– 100 charcoal broiled steaks (cancer)
Weapons of Mass Destruction
• Weapons capable of inflicting large
numbers of casualties or affecting a large
area in a single event
• Nuclear
• Chemical
• Biological
• Any time you pack a large amount of
energy into a small space, you have a
potential weapon
Chemical Weapons
Riot Control (Tear Gas)
Choking (Cl, phosgene CCl2O)
Blood (HCN)
Nerve (Sarin)
Blister (Mustard Gas)
Hallucinogens (researched, never used)
Incapacitating (researched, never used)
Defoliants (Agent Orange, Vietnam)
Chemical Weapons in War
• World War I
– Tear Gas
– Chlorine
– Mustard Gas
Japanese in China: 1930's - WWII
Not used by other parties in WWII
Yemen 1960's
"Yellow Rain:" SE Asia, 1970's (Discredited)
Iraq against Kurds, Iran, 1980's
US renounced first use but reserves right to
Use of Chemical Weapons
• Gases disperse too quickly
– Usually delivered as aerosols
– Dependent on weather conditions
– Wind, rain, heat are unfavorable
• Most historical uses against unprotected
– Trained soldiers have protection
– Reduces efficiency of both sides
– Psychological effect
Effects of Chemical Weapons
• Nerve Agents
– Long Term: Nerve Disorders, Brain Damage
• Blister Agents
– Short Term: Severe Burns
– Long Term: Skin Cancers and Lesions, Lung
• Most Chemical Agents Easily Decomposed
• Long Term Effects of Low-Level Exposure
– Gulf War Syndrome, Agent Orange
Biological Weapons
• No known modern historical military uses
• US has stated will not use
• Limitations
– Should be self-limiting
– Need fairly quick action
– Anthrax and Smallpox given most speculation
• Plant pathogens
– Wheat Rust, Hoof-and-Mouth
– Drug Interdiction?

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