Download Chapter 8: Environmental Health and Toxicology

Chapter 8: Environmental Health and
Toxicology
By Anna Blum and Maggie Ellis
Environmental Health
• Environmental Health-focused on factors that
cause disease, including elements of the
natural, social, cultural, and technological world
in which we live
• Ever since Silent Spring, focus on discharge,
movement, fate, and effects of synthetic
chemical toxins
• Risks come from:
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Toxins
Radiation
Infectious Agents
Trauma
Pollution
The Global Disease Burden is Changing
• Disease burden calculated in terms of DALYs
• Chronic conditions now affect poor as well as
affluent because people live longer
• Causes: By 2020
– Heart disease to be leading cause of global disease
– Global cancer rates will increase by 50%
– Psychiatric and neurological conditions will increase
from 10% to 15% (Depression expected to be the
second largest cause of all years lived with disability
worldwide)
– Chronic obstructive lung diseases expected to
increase
Things That Kill You (part 1)
• Heart disease number
one killer, kills women
more than men
• Suicide is the fourth
largest cause of female
deaths
• Smoking predicted to be
single biggest cause of
death worldwide
Infectious Diseases Are Scary
• Communicable diseases
responsible for about 1/3 of
all disease-related mortality
• 11 million children under 5
die annually due to infectious
diseases
• Most of these deaths could
be eliminated through better
nutrition, clean water,
improved sanitation, and
inexpensive inoculations
More Infectious Diseases
• Malaria- 515 million cases each year, 1 million
people die
• Spreading as climate changes expands
mosquito habitats
• Emergent diseases-those not previously known
or have been absent for at least 20 years
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SARS
Avian Flu
H1N1
Ebola
West Nile Virus
AIDS/HIV
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Case Study: Chronic Wasting
Disease
Chronic Wasting Disease—deer and
elk populations in North America
– Caused by strange prion protein
– One of a family of irreversible,
degenerative neurological diseases
known as transmissible spongiform
encephalopathies (TSE) including mad
cow
– Canadian government spending $65
million to fight CWD
– Cattle imported from Canada found to
have TSE in 2004
– Worry about it spreading to humans, as
of yet no one in the US has died
Causes of Emergent Disease
• Environmental change stresses
biological systems
– Cut down forests
– Drain wetlands
– Invasive species introduced by
humans
– Increased human incursion into
wilderness
– Increased consumption of wild
species allows diseases to jump
barriers---3/4 of all emerging diseases
are zoonotic, or shared by animals
and humans
– Climate change allows animals to
expand their range
Increasing Resistance to Antibiotics
and
Pesticides
is
• Partially through natural selection and ability to evolve
rapidly
– Mutated bacteria that are resistant live and multiply via natural
selection
• Partially through human tendency to use control
measures aimlessly
– DDT spread everywhere, so that some were only minimally
exposed—encouraged natural selection and the survival of
resistant
Antibiotics, Farming, and Disease
• More than half of the antibiotics
used in the US each year are fed
to livestock
• These antibiotics and hormones
are excreted in urine and feces
• Spread on land or water where
they evolve into supervirulent
pathogens
• At least half of the 100 million
antibiotic doses prescribed to
humans each year are
unnecessary or wrong—improper
disposal or use can lead to illness
Toxicology
• Study of toxins (poisons) and
their effects on living
systems
• Damage or kill living
organisms because they
react with cellular
components to disrupt
metabolic functions
• Toxins harmful even in dilute
concentrations
Ecotoxicology
• All toxins hazardous, but not all
hazardous materials are toxic
– Some materials are hazardous
because they are flammable,
explosive, etc.
• Environmental
Toxicology=ecotoxicology, deals
with the interactions,
transformation, fate, and effects of
natural and synthetic chemicals in
the biosphere, including individual
organisms, populations, and whole
ecosystems
How Do Toxins Affect Us?
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Allergens & Antigens
Immune system depressants
Endocrine disrupters
Sick building syndrome
– poor indoor air quality may
cost USA $60 billion in sick
days and reduced productivity
Teratogens
• Chemicals or other factors that
specifically cause abnormalities during
embryonic growth and development
• Example: Fetal alcohol syndrome- a
cluster of symptoms including craniofacial
abnormalities, developmental delays,
behavioral problems, and mental defects
that last throughout a child’s life
• Even on drink during pregnancy puts a
child at risk
• By some estimates, between 300,000
and 600,000 children born every year in
the US are exposed in the womb to
unsafe levels of mercury
• Effects include reduced intelligence,
ADD, and behavioral problems, costing
$8.7 billion annually
Carcinogens
• Substances that cause cancer
• According to the American Cancer
Society, ½ males and 1/3 females will
have some sort of cancer in their
lifetime
• Debate over environment vs. lifestyle
• According to the EPA, 200 million US
residents live in combined lifetime
cancer risk form environmental
carcinogens exceeds 1 in 100,000 or
ten times the acceptable risk
Diet Affects Health
• Strong correlation between cardiovascular disease and the
amount of salt and animal fat in one’s diet
• Fruits, vegetables, whole grains, complex carbs, and dietary
fiber have a positive affect
• Vitamins A,C, and E, substances produced in cruciferous
vegetables, and selenium seem to have anticancer effects
• Every year in the US 300,000 deaths are linked to obesity
• 1/3 of US children may become diabetic unless people start
eating less and exercising more, increased risk (1/2) for
Black and Hispanic children
Case Study: Poisoning Bhopal
• December 3rd, 1984
• Bhopal, central India,
• Noxious gas methylisocyanate (MIC), a
component of pesticide Temik, made at
the Union Carbide plant in Bhopal.
• Water had gotten into tank and it
exploded, sending MIC throughout the
city
• 15,000 died instantly; 800,000 suffered
medical problems
• More than 20 years after the
catastrophe, no one punished and most
of the $470 million paid by Union
Carbide has yet to be distributed
Solubility
• Solubility is important in determining how, when,
and where a toxic material will move to the site
of action
• Water soluble compounds move widely and
rapidly and have ready access to most cells
• Oil or fat soluble compounds generally need a
carrier to move but can easily penetrate cells
– more likely to accumulate and be stored in lipid
deposits for years
Exposure & Susceptibility
• Airborne toxins generally cause more ill
health
• Toxins also enter through food, water, skin
contact
• Largest exposure for toxins
are found in industrial settings
• Condition of being & timing
of exposure influence toxicidty
Bioaccumulation &
Biomagnification
• Cells have mechanisms for
bioaccumulation
– allows them to accumulate
nutrients and essential
materials but also leaves the
risk of absorbing bad toxins
• Bioaccumulation
• Biomagnification: When the
toxic burden of a large number
of organisms at a lower trophic
level is accumulated and
concentrated by a predator in a
higher tropic level
Persistence
• Some chemical compounds are unstable
and degrade rapidly so their
concentrations decline quickly after
release
• Others are more persistent and last for a
few centuries
– cause more problems and unexpected effects
Things That Kill You (part 2)
• PBDEs are in textiles, upholstery, and plastic. They
effect behavioral & nervous system development
• PFOs and PFOA/C8s are found in nonstick, water-proof,
stain-resistant products and everywhere. Literally.
– cause liver damage, cancer, reproductive and
developmental problems in rats; kill pet birds
• Phthalates are found in cosmetics, deodorants, and
many plastics
– cause kidney and liver damage,
cancer in rats; endocrine hormone
disrupters that cause reproductive
abnormalities and decreased
fertility/quality of sperm
Things That Kill You (part 3)
• Perchlorate is a waterborne containment left over
from propellants and rocket fuels; it pollutes water
used to water crops.
– Disrupts adult metabolism and childhood developments
• BPA is in polycarbonate plastic.
– Causes abnormal chromosome numbers, aneuploidy
(the leading cause of mental retardations and
miscarriages)
• Atrazine is a widely used herbicide
– Causes birth defects, abnormal development
Interactions!
• Antagonistic reactions
interfere with the effects or
stimulate the breakdown of
other chemicals
• Additive reactions occur
together in exposure
• Synergism: An interaction
in which one substance
exacerbates the effects of
another
Degradation & Excretion
• Enzymes process waster products and environmental
poisons to reduce their toxicity
– can make chemicals more dangerous by breakdown
ones that should not be broken down
– Factors that affect post reproduction stages usually
don't effect reproductive success or exert selective
pressure
• Excretion reduces the effects of
waste products and environmental toxins by
eliminating them from the body
Repair
• Our skin and organ linings have high
cellular reproduction rates to replace
injured cells
– Chance that cells will lose normal
growth controls and create a tumor and
irritants will be turned into carcinogens
Why Lab Animals Die
• Because we test toxins on them!
• Expensive, time-consuming, painful to animals
– takes hundreds of animals, years of work, thousands
of dollars for one text
– however, most accurate and reliable data
– more human toxicity tests are being developed
• Problems
– differences in sensitivity in members of a population
– unrelated species can react very differently to same
toxin
Acute versus Chronic
• Acute effects
• Chronic effects
• Usually difficult to detect
the specific health risks
because of other factors
• Different toxicity levels for everything
• Just because they are detectable doesn't
mean you'll die
Risky Business
• Risk: The possibility of
something undesirable will
happen as a result of
exposure to a hazard
• Risk assessment: The
scientific process of
estimating the threat
hazards pose to health
– Includes risk identification,
dose response
assessment, exposure
appraisal risk
characterization
Why We Do Stupid Things (part 1)
• People downplay certain risks and emphasize others
that suit their agenda
• Tolerate risks that we choose and
object those we don't
• Have difficulty understanding and
believing probabilities
• Personal experiences can be misleading
• Exaggerated view of our ability to control fate
• Media gives a biased perspective of things
• Irrational fear or mistrust of new technology
Why We Do Stupid Things (part 2)
• Most people will tolerate a
higher probability of an event
if the harm caused by it is low
• If we enjoy or find an activity
profitable, we will ignore the
risks
• Perception of risks based on
whether they are known or
unknown, we are in control of
the outcome or not, and how
bad the results can be
Things That Keep You Alive
• It is difficult to separate the effects of different hazards
and evaluate their risks accurately
• When setting standards for environmental toxins,
consider:
– combined effect of exposure to many different areas of
damage
– different sensitivities of members of the population
– effects of chronic and acute exposure
– how does it affect our overall environment?