Transcript Environmental Health & Toxicology

Environmental Health &
Toxicology
Chapter 15
APES
2008
Some Vocab…
• WHO- World Health Organization
• Health- state of complete physical, mental, and social
well being (not just the absence of disease)
• Disease- change in the body’s condition in response to
an environmental factor
– Ex: nutritional, chemical, biological or psychological
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Morbidity- illness
Pathogen- disease-causing organism
Vector- organism that spreads disease
Emergent- new, not identified or absent for last 20 years
Zoonotic- transmitted from animal host to humans
PATHOGENIC VS.
NON-PATHOGENIC
• 43% of all diseaserelated deaths are
from pathogens
• 57% from
cardiovascular
disease, cancer, lung
disease, injuries, etc.
Pathogenic
NonPathogenic
DISEASE
ETC.
MILLIONS OF DEATHS PER
YEAR
Cardiovascular disease
9.7
Cancers
6.0
Chronic Lung Disease
Ex: tuberculosis
5.5
Acute Lung Disease
Ex: pneumonia, flu, pertussis (whooping cough)
4.1
Injuries
Mostly in 18-39 age group due to car accidents
4.0
Mostly from Infections
3.2
Diarrhea
From bacteria & pathogens; excessive can
cause mental/developmental retardation
3.0
HIV/AIDS
2/3 of all cases are in Africa; most cannot afford
the $10,000 drugs (like people in U.S.)
2.3
500 million new cases each year; making a
comeback
2.0
Polio, Measles, Hepatitis B, Tetanus; LDC have
no access/money for these vaccines
1.7
Perinatal conditions
Malaria
Vaccine-preventable
infections
Other known disease
3.9
Unknown causes
5.9
Total
51.0
Morbidity & Quality of Life
• Not everyone dies from disease, but still can cause
severe suffering and debilitation
• When sick…
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Crops not planted/harvested
Animals not tended
Work not done
Kids not fed
• Poorest people are most affected because they live in
unhealthiest environments & don’t have $ for health
care.
• Lack of adequate housing, sanitation, safe drinking water
causes most cases of diarrhea which is made worse by
malnutrition.
Part I: Infectious Diseases
• Onchocerciasis (river
blindness)
– Vector: Black fly
– Many roundworms get
into eyes & die
causing blindness
– Control with
insecticide sprays
– Merck & Co. are
providing free
ivermectin to help
eradicate.
Infectious Diseases
• Elephantiasis
– Vector: Mosquitoes
– Roundworm gets into
lymph system and
blocks lymph vessels
causing fluid build up
in the extremities.
– SmithKline Beecham
is supplying free
albendazole to
eradicate.
Infectious Diseases
• Drancunculiasis– Guinea worm
– Vector: Drinking
Water contaminated
with Cyclops
– 3 meter long worm
that lives under skin.
Forms blister & must
be wound out of skin
to remove
Infectious Diseases
• Hemorrhagic Fever
– Some Types…
• Ebola: Vector- unknown
• Lassa: Vector- Mastomys
rat species
• Hanta: Vector- Deer mice
– All cause tissue
deterioration, bleeding,
pulmonary edema.
– Ebola has 90% mortality
rate.
Infectious Diseases
• Dengue Fever
– Vector: Mosquitoes
– 20 million new cases;
2.5 billion current
cases
Infectious Diseases
• Malaria
– Vector: Mosquitoes
– 3 million die each year,
90% of them in Africa
– In 1950’s & 60’s, sprayed
DDT & knocked down from
millions cases each year to
thousands, now back to 2.5
million new cases
– Some Aedes aegypti
mosquitoes seen along
Gulf Coast of America- due
to climate change?
Infectious Diseases
• Cholera
– Cause: Bacteria in unclean
drinking water
– Severe stomach cramping,
severe diarrhea, vomiting
– Thought eradicated but has
made comeback due to
ships dumping bilges in
harbors of cities with
inadequate water treatment
Infectious Diseases
• Tuberculosis
– Cause: bacillus bacteria
Mycobacterium tuberculosis
– Eliminated but has
returned stronger than
ever
– Some strains drug
resistant
– Spreads rapidly
– EX: Russian prisons
What causes disease to spread so
rapidly?
• Population density , so contact 
• Moving into remote areas for
agriculture  exposure.
• Deforestation, pollution causing
local & global climate change ( in
temp =  in mosquito pop.)
• Eliminating predators so  in
rodent, roach, mosquito pop.
•  in speed & frequency of travel
(airplanes, ships) to other countries
•  in resistance (Malaria) =
“Superbugs”
• Taking medication improperly leads
to “superbugs”
• Antibiotics given to farm animals
increases their resistance.
Part II:Dangerous Chemicals
Hazardous (dangerous) Toxic (poisonous)
• Harmful even in small
• Some are harmless
amounts
when diluted
• Ricin- protein in castor
• Classifications:
beans is thought to be the
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Flammable
Explosive
Irritant
Acids
Caustic
most toxic organic
compound on Earth.
• Ricin is 200x more lethal
than dioxin.
Toxic Chemicals
• Allergens
– overactivate immune
system
– Ex: formaldehyde
• Immune System
Depressants
– Suppress immune system
– Ex: PCB’s used as flame
retardants & electrical
insulators (seals & dolphins
died due to infections
brought on by suppressed
immune system)
Toxic Chemicals
• Mutagens
– Chemicals or radiation that
damages or alters DNA
– Can cause birth defects or
tumors
– Can be passed through
sperm/egg
– Ex: aflatoxin (from mold);
caffeine, LSD,
benzapyrene (in
cigarettes); nitrous oxide;
ozone
Toxic Chemicals
• Teratogens
– Chemicals that cause
abnormalities during embryonic
development
– Ex: Thalidomide
• Sold as OTC sleeping pill in
Europe
• Caused Phocomelia (had
hands & feet but no arms or
legs)
• Can have immediate affect
• Positive: can be used to treat
leprosy, AIDS, cancer, tissue
rejection
– Alcohol is most prevalent
teratogen- Fetal alcohol
syndrome results in low birth
weight, mental delays
Toxic Chemicals
• Carcinogens
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Cause cancer
Increasing in developed countries
2nd cause of death in US
Maybe result of toxic chemicals in
life
• Foods/preservatives
• Pesticides
• smoking
– Breast, Testicular, & Skin cancers
increasing
– Stomach, Uterine, Colon cancers
decreasing due to new technology
for treatment.
– Ex:
• Formaldehyde- particle board
• Paradichlorobenzene- toilet
cleaner
• Perchloroethylene- dry cleaning
• Pesticides- 2,4
dichlorophenoxyacetate
Some foods contain carcinogens
(broccoli) but the other benefits
outweigh the risk.
Toxic Chemicals
• Neurotoxins
– Kill nerve cells
– Disrupt cell membrane of nerve
cell
– Inhibit acetylcholinesteraseenzyme that transmits nerve
signals
– suppress nervous system
– EX:
• Heavy metals like lead & mercury
(Minamata Disease p.300)
• Anesthetics- ether, chloroform,
halothane
• Chlorinated Hydrocarbons- DDT,
Dieldrin, Aldrin (POPs)
• See page 300 table 15.1
• Organophosphates- parathion
• Carbamates- carbaryl (Bhopal,
India)
Toxic Chemicals
• Endocrine Disruptors or Hormonally
Active Agents (HAAs)- toxicants that
interfere with the endocrine system by
mimicing the hormone.
• Newly discovered
• Includes chemicals such as herbicides, pesticides,
PCBs, phthalates (found in chlorinated plastics)
• Problems: breast, prostate, ovarian cancer, abnormal
testicular development, thyroid related abnormalities
• Hermaphroditic frogs, alligators w/ genital abnormalities
Bhopal, India
Worst Industrial Accident in History
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December 1984
Union Carbide- American company located
in Bhopal manufactured carbaryl & methyl
isocyanate (MIC) used to make pesticide
Sevin (as in Sevindust)
Holding tanks at the plant malfunctioned
(due to human error & lack of routine
maintenance)
Toxic MIC gas cloud released late at night
People who were exposed began choking,
frothing at the mouth, vomiting blood, many
died within minutes. The streets were
littered with dead bodies.
15,000-33,000 have died from this accident
100,000 that survived are blind and/or are
having reproductive, neurological, &
respiratory problems.
Soil & water are contaminated
No one has been held responsible- DOW
and Union Carbide have “washed their
hands of the problem.”
Minamata Bay and Mercury
• 1950’s in Kyushu, Japan
• Japanese live on island so eat fish
and shellfish from Minamata Bay.
• 1st signs seen in animals,
especially cats- appeared to dance
but were really having seizures.
• People began experiencing
neurological problems, paralysis,
uncontrollable shaking, vision
problems
• Children born with brain atrophy,
malformed limbs, etc.
• Plastic factory was dumping
mercury into Minamata Bay.
• Mercury was accumulating through
the food chain- Biomagnification
OTHER ENVIRONMENTAL
HEALTH HAZARDS
• Radiation- power lines,
nuclear power plants
• Noise
• Trauma- accidents &
violence
• Stress- heart attack,
stroke, ulcers increase
chance for infectious
disease
• Diet- too much bad food
causes stress on body,
leads to cardiovascular
disease
What determines
how “dangerous”
a chemical is?
• Persistence in
environment
• Route/method of
exposure
• Characteristics of
target organism
FACTORS RELATED TO TOXIC AGENT
1. Chemical composition & reactivity
2. Physical traits- solubility, state of matter
3. Presence of impurities
4. Stability and storage traits
5. Availability of vehicle to carry agent
6. Movement of agent thru environment & into cells
FACTORS RELATED TO EXPOSURE
1. Dose- concentration & volume of exposure
2. Route, Rate, and site of exposure
3. Duration and frequency of exposure
4. Time of exposure (time of day, season, year)
FACTORS RELATED TO ORGANISM
1. Resistance to uptake, storage, or cell permeability
2. Ability to metabolize or inactivate agent
3. Tendency to change non-toxic to toxic in body
4. Concurrent infections or physical stress
5. Species and genes of organism
6. Nutritional status of subject
7. Age, sex, body weight, immunological status &
maturity
Characteristics in determining how,
when, and where a toxic material
will move thru the environment:
• Solubility
– Dissolve in Water
• Move rapidly & widely
• Readily access cells in body
– Dissolve in Oil
• Need a carrier into & thru body
• Penetrate tissue readily, stored in fat cells of body
• Take many years to break down
– Bioaccumulation- accumulation of toxins within an
individual organism. May be dilute in environment but
reach dangerous levels in the body.
• Biomagnificationaccumulation of
toxins thru a food
web.
– Chemical intensifies at
each step
– DDT, mercury, are
examples
Characteristics in determining how,
when, and where a toxic material
will move thru the environment:
• Persistence- how long does it
last in environment?
– Some unstable & degrade
quickly
– Some resistant to degradation
(PVC plastic, DDT, CFC’s,
asbestos)
• This may be why they are
used- asbestos, PVC, DDT
• May be an unfortunate sideeffect
– DDT was valued because it
broke down slowly & did not
have to be reapplied.
– We did not know the affects
it would cause in fish, birds
of prey, and people
(biomagnification).
Characteristics in determining how,
when, and where a toxic material
will move thru the environment:
• Chemical Interactions
– Antagonistic interactions- interfere with effects or
stimulate the breakdown of other chemicals
• Ex: Vitamins A and E interfere with some carcinogens
– Synergistic interactions- one substance makes the
affects of another worse.
• Occupation asbestos exposure increase lung cancer rate 20
fold
• Smoking increases lung cancer rate 20 fold
• A smoker that works with asbestos increases his chance for
lung cancer 400 fold
Mechanisms for minimizing toxic
effects
• Every material can be poisonous/toxic at some
level.
• Most chemicals have safe levels or thresholds
below which their affects are undetectable.
• EX: 100 cups of coffee have enough caffeine to
kill if consumed all at once- but most people
don’t consume that much.
• Taken in small doses, chemicals can be broken
down by the body and released.
Measuring Toxicity
• How a material is delivered plays a vital
role in determining toxicity.
– At what rate? (a little over time or all at once)
– Through which route of entry? (skin, mouth,
nose)
– In what medium? (solid, liquid, gas)
• Different species respond differently and
different individuals in a species can react
differently.
• Most common & widely accepted
measure of toxicity
• Cons
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Expensive
Time consuming
Painful/debilitating
Takes thousands of animals & lots
of money
• Alternates
– Cell cultures
– Computer simulation
• Some animals of a species are
more sensitive than others so
some die off quicker. Some are
hardier than others so they live
longer. This produces a bell
shaped curve
• Should we set safety limits to
protect all including most sensitive
or just the average person?
• By protecting all, it might cost
more money…
Animal Testing
LD50
Lethal Dose 50
• LD50- dose at which 50% of the test
population dies.
• See Table 15.4 on page 309 of textbook
for lethal doses of some toxic organic
chemicals.
Acute vs. Chronic Exposure
• Acute effects- caused by single source
and are immediately effective causing
immediate health problems.
• Chronic- takes place over a long period
– Continuous or repeated sub-lethal exposure
– For ex. Exposure to low levels of radiation
over lifetime may cause mutations and lead to
disease.
FDA Regulations
• 1958 Delaney Clause to US FDA Act
forbids the addition of any amount of
known carcinogen to food and drugs.
• 1966 No Reasonable Harm addendum
says that carcinogens OK if less than one
cancer for every million people exposed
over a lifetime.
Assessing Risk
• What factors influence how we perceive risk?
– People will downplay risk to suit their own agendas
– Some don’t understand probability.
– Personal experiences can be misleading- (Love
Canal)
– We have an exaggerated view of our abilities.
– Media is mostly biased
– Fear or distrust of certain technologies (Nuclear
Power)
Accepting Risk
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How much risk is acceptable?
Individualized
If you enjoy doing an activity you will accept those risks.
If an activity benefits someone else, you may not take
those risks.
• EX:
– Chance of dying from lung cancer if you smoke 1 pack/ day is 1
in 1000.
– EPA limits for trichloroethylene is 2 in 1 billion. People will
demand water with 0 levels of trichloroethylene but still smoke
cigarettes.
• See Table 9.7 page 206 for list of activities and death
risks.
Relative Risks to Human Welfare
(from EPA)
• High Risk Problems
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Habitat alteration & destruction
Species extinction & loss of diversity
Stratospheric ozone depletion
Global climate change
• Medium Risk Problems
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Herbicides/pesticides
Toxics & pollutants in surface water
Acid deposition
Airborne toxics
• Low Risk Problems
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Oil spills
Groundwater pollution
Radionuclides (uranium, radon)
Thermal pollution