Chapter 14: Environmental Health
and Toxicology
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Environmental Health
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assesses environmental factors that
influence human health and quality of life
natural
human-caused
Physical Hazards
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natural disasters
earthquakes
volcanic eruption
fires
floods
blizzards
landslides
hurricanes
droughts
UV radiation
difficult to predict
areas of high risk can be determined
Chemical Hazards
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synthetic chemicals society produces
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disinfectants (Lysol products)
pesticides (DDT)
Biological Hazard
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ecological interaction between organisms
infectious diseases
swine flu: virus
tuberculosis: bacteria Mycobacterium
tuberculosis
malaria: parasite Plasmodium sp.
cholera: bacteria Vibrio cholerae
Cultural Hazards
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behavioral choices
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smoking, sunbathing, drug use
location we live in
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near an active volcano
Alaskan volcano 2006
apod.nasa.gov/apod/ap060607.html
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socioeconomic status
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Cadillac Heights
occupation
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hazardous work or
lack of safety equipment
www.dallasnews.com
Dallas Flood June 2007
Disease
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major factor of environmental health
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Indoor Health Hazards
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radon
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highly toxic gas
seeps up from the ground in certain areas
lead
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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
Indoor Health Hazards
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asbestos
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form long thin microscopic fibers
used in insulation (sound, heat)
resists fire
dangerous when inhaled: asbestosis & cancer
PBDEs
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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
Toxicology
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study of poisonous substances
environmental toxicology deals with toxics
discharged in the environment
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on humans
other animals
ecosystems
Environmental Toxicology
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natural toxins
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radon, arsenic, mercury
exuded substances from plants and animals
human-made toxins
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wastewater contaminants
pesticides & herbicides
Silent Spring by naturalist Rachel Carson
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effect of DDT on humans, animals and ecosystems
DDT is still in use in tropical areas to control diseases
Types of Toxicants
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carcinogens
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mutagens
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causes cancer
causes mutations in fetus
teratogens
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affects fetus during gestation causing birth
defects
Thalidomide
Types of Toxicants
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allergens
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weakens immune system
increase in asthma
neurotoxins
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inorganic: heavy metals (lead, mercury)
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Minamata case
organic: pesticides (DDT, mothballs, nerve gas)
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some are very stable and can last decades, others may
only last hours
Types of Toxicants
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endocrine disruptors
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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
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testicular cancer
undescended testicles
genital birth defects in men
female breast cancer
Effects of Endocrine Disruptors
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Other Effects of Endocrine Disruptors
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brain functioning
PCB contamination of food (fish)
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lower birth weight of babies
smaller heads
weak and jerky reflexes
tested poorly in intelligence tests
Means of Toxins' Disperse
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water
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many are soluble in water
runoff
concentrates toxins in surface waterways
enters tissue through drinking or contact
air
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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
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Bioaccumulation
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stored in tissues according to its solubility
Biomagnification
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increase in toxin concentration up in the food
chain
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Bald eagle case related to DDT
population decrease of polar bears
Epidemiology Studies
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application of experimentation due to conditions in
the environment
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effect of a contaminant in the air to a population already
established
drawback
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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
Dose-responce Toxicity
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effect of toxins according to amount in the
system/body
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LD50→ lethal dose for 50%
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ED50→ effective dose for 50%
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low LD50 means high mortality
high LD50 means low mortality
half of the population gets sick but doesn't die
Threshold
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toxin level above which a responce is observed
Exposure vs Responce
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acute responce
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responce to a high exposure during a short period of time
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chronic responce
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responce to a low concentration of a toxin but during a long
period of time
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Union Carbide accident in India
exposure to Teflon
synergistic effect
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unpredicted consequences of mixing toxins
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sum
cancel
multiply or exacerbate
Risk Assessment & Risk Management
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Assessment: collection and interpretation of scientific
data identifying outlining problems
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expressed in probability
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risk of crashing if driving too fast
Management: formulation of policy to minimize risk
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influenced by political pressure
considers economics and ethics
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EPA, CDC, FDA
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banning of Seldain D
– banning of DDT
– containing cholera
Philosophical Approaches
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innocent-until-proven-guilty
innovation goes ahead
doesn't slow down technology
can result in disasters
recall
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Vioxx (short period of testing)
vitamins & herbs (unregulated)
Philosophical Approaches
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harmful until proven otherwise
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precaution principle
experimentation has to be done thoroughly
long process]
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regulated medications
EPA
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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
EPA examines the data from the manufacture
assesses the possible risks to humans and
environment
approves, denies or sets limits to use
Toxic Substances Control Act (1976)
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regulation of synthetic chemicals by the EPA
criticized as too weak
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screening of industry is minimal
EPA needs to show proof of toxicity and not the
other way around
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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
International Regulation
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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
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The End