Chapter 14: Environmental Health and Toxicology

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Chapter 14 Environmental Health and Toxicology
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Environmental Health

• assesses environmental factors that influence
  human health and quality of life
• natural
• human-caused

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Physical Hazards

• natural disasters
• earthquakes
• volcanic eruption
• fires
• floods
• blizzards
• landslides
• hurricanes
• droughts
• UV radiation
• difficult to predict
• areas of high risk can be determined

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Chemical Hazards

• synthetic chemicals society produces
• disinfectants (Lysol products)
• pesticides (DDT)

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Biological Hazard

• ecological interaction between organisms
• infectious diseases
• examples
• swine flu virus
• tuberculosis bacteria Mycobacterium tuberculosis
• malaria parasite Plasmodium sp.
• cholera bacteria Vibrio cholerae

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Cultural Hazards

• behavioral choices
• smoking, sunbathing, drug use
• location we live in
• near an active volcano

Alaskan volcano 2006
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• socioeconomic status
• Cadillac Heights
• occupation
• hazardous work or
• lack of safety equipment

Dallas Flood June 2007
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Disease

• major factor of environmental health

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Indoor Health Hazards

• radon
• highly toxic gas
• seeps up from the ground in certain areas
• lead
• water from lead pipes and lead paint in homes and
  toys
• damages brain, liver, kidney and stomach
• learning disabilities
• behavioral abnormalities
• anemia
• hearing loss
• death

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Indoor Health Hazards

• asbestos
• form long thin microscopic fibers
• used in insulation (sound, heat)
• resists fire
• dangerous when inhaled asbestosis cancer
• PBDEs
• fire-retardant
• used in electronics, plastics and furniture
• evaporates at very low rates
• accumulates in tissues
• may affect nervous system and cause cancer
• banned in the EU

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Toxicology

• study of poisonous substances
• environmental toxicology deals with toxics
  discharged in the environment
• on humans
• other animals
• ecosystems

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Environmental Toxicology

• natural toxins
• radon, arsenic, mercury
• exuded substances from plants and animals
• human-made toxins
• wastewater contaminants
• pesticides herbicides
• Silent Spring by naturalist Rachel Carson
• effect of DDT on humans, animals and ecosystems
• DDT is still in use in tropical areas to control
  diseases

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Types of Toxicants

• carcinogens
• causes cancer
• mutagens
• causes mutations in fetus
• teratogens
• affects fetus during gestation causing birth
  defects
• Thalidomide

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Types of Toxicants

• allergens
• weakens immune system
• increase in asthma
• neurotoxins
• inorganic heavy metals (lead, mercury)
• Minamata case
• organic pesticides (DDT, mothballs, nerve gas)
• some are very stable and can last decades, others
  may only last hours

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Types of Toxicants

• endocrine disruptors
• interfere with hormones
• affects growth, reproduction, behavior, brain
  function
• similar to hormones so they "mimic" them
• certain pesticides? feminization of males
• possible cause of human sperm count drop
  worldwide
• possible cause of increase rates of
• testicular cancer
• undescended testicles
• genital birth defects in men
• female breast cancer

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• Effects of Endocrine Disruptors

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Other Effects of Endocrine Disruptors

• brain functioning
• PCB contamination of food (fish)
• lower birth weight of babies
• smaller heads
• weak and jerky reflexes
• tested poorly in intelligence tests

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Means of Toxins' Disperse

• water
• many are soluble in water
• runoff
• concentrates toxins in surface waterways
• enters tissue through drinking or contact
• air
• pesticide drift
• toxins appeared in tissues of arctic polar bears
  and antarctic penguins
• thought to be due to global atmospheric
  circulation

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• Distribution of Toxins

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Toxins in the Food Chain

• Bioaccumulation
• stored in tissues according to its solubility
• Biomagnification
• increase in toxin concentration up in the food
  chain
• Bald eagle case related to DDT
• population decrease of polar bears

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Epidemiology Studies

• application of experimentation due to conditions
  in the environment
• effect of a contaminant in the air to a
  population already established
• drawback
• takes too long
• many other factors may affect the health of the
  subjects
• statistical association between health hazard and
  effect but it does not confirm it as the cause of
  the problem

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Dose-responce Toxicity

• effect of toxins according to amount in the
  system/body
• LD50? lethal dose for 50
• low LD50 means high mortality
• high LD50 means low mortality
• ED50? effective dose for 50
• half of the population gets sick but doesn't die
• Threshold
• toxin level above which a responce is observed

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Exposure vs Responce

• acute responce
• responce to a high exposure during a short period
  of time
• Union Carbide accident in India
• chronic responce
• responce to a low concentration of a toxin but
  during a long period of time
• exposure to Teflon
• synergistic effect
• unpredicted consequences of mixing toxins
• sum
• cancel
• multiply or exacerbate

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Risk Assessment Risk Management

• Assessment collection and interpretation of
  scientific data identifying outlining problems
• expressed in probability
• risk of crashing if driving too fast
• Management formulation of policy to minimize
  risk
• influenced by political pressure
• considers economics and ethics
• EPA, CDC, FDA
• banning of Seldain D
• banning of DDT
• containing cholera

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Philosophical Approaches

• innocent-until-proven-guilty
• innovation goes ahead
• doesn't slow down technology
• can result in disasters
• recall
• Vioxx (short period of testing)
• vitamins herbs (unregulated)

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Philosophical Approaches

• harmful until proven otherwise
• precaution principle
• experimentation has to be done thoroughly
• long process
• regulated medications

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EPA

• Federal Insecticide, Fungicide and Rodenticide
  Act of 1947 assured the effectiveness of the
  product
• EPA was created to protect the public and
  environment from toxic chemicals using risk
  assessment and management
• examines the data from the manufacture
• assesses the possible risks to humans and
  environment
• approves, denies or sets limits to use

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Toxic Substances Control Act (1976)

• regulation of synthetic chemicals by the EPA
• criticized as too weak
• screening of industry is minimal
• EPA needs to show proof of toxicity and not the
  other way around
• only 10 have been tested for toxicity
• only 2 have been tested for carcinogens
• fewer than 1 are government regulated
• none have been tested for endocrine, nervous or
  immune system damage

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International Regulation

• Stockholm Convention on persistent Organic
  Pollutants of 2004
• "dirty dozen"
• guidelines to phase off these chemicals
• REACH pushes innovation of new chemicals to do
  the same job but be less toxic

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• Dirty Dozen