Transcript emergent disease

Environmental Health,
Toxicology, & Risks
In some parts of Eastern Europe and the former USSR, up
to 90% of all children suffer from environmentally linked
diseases.
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Terminology
Pollution – unwanted change in the environment caused by
introducing harmful material, or by
producing harmful conditions.
Contamination – introduction of undesirable material to one
or more of the “spheres” making it unfit.
Toxicology – science that studies chemicals that are toxic,
or could be toxic .
Pollutants – e.g.,
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infectious agents,
toxic heavy metals,
organic compounds & persistent organic pollutants (POPs),
hormonally active agents (HAA),
nuclear radiation,
thermal pollution,
particulates,
electromagnetic fields (EMF),
noise pollution,
etc.
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FACTBOX
World's 10 Most Polluted Places
February 2, 2009
Below are the world's 10 most polluted places listed,
according to Time/CNN
http://www.time.com/time/specials/2007/article/0,28804,1661031_1661028_1661016,00.html
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Linfen,China (6)
Tianying, China
Sukinda, India
Vapi, India
La Oroya, Peru (5)
Dzerzhinsk, Russia (2)
Norilsk, Russia (8)
Chernobyl, Ukraine (1)
Sumgayit, Azerbaijan
Kabwe, Zambia (4)
- auto/industrial coal/air particulates
- mining/processing lead/heavy metals
- chromium mining/processing heavy metals
- industrial chemicals & heavy metals
- mining/processing Pb, Cu, Zn, SO2
- chemical weapons toxic byproducts
- Ni/metal mining/processing air pollution
- nuclear meltdown radiation
- petrochem/indust organic/oil/heavy metals
- Pb mining/processing Pb & Cd
Previous in 2007:
Haina, Dominican Republic (3), Mailuu-Suu, Kyrgyzstan (7),
Ranipet, India (9), Rudnaya Pristan, Russia (10)
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What is Health?
• Health defined by the World Health Organization as:
the state of complete physical, mental, & social
well-being – not just absence of disease.
• Disease - a abnormal change in the body’s
condition that impairs important physical and
psychological functions in response to an
environmental factor
(nutrition, chemicals, biological agents, etc)
• Morbidity – illness or disease
• Mortality – death rate
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Infectious
diseases used
to be the
primary cause
of death in the
past and has
been replaced
by
cardiovascular
diseases and
cancers
smoking?
Deforestation
causes insect
vectors to
move to cities
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Morbidity and Quality of Life
• Death rates do not tell everything about
burden of disease.
• What is the total social burden of diseases?
– Total economic and social consequences of
diseases are difficult to obtain.
• Disability-Adjusted Life Year (DALY) combines
premature deaths and loss of healthy life resulting
from illness or disability. It attempts to evaluate the
total cost of disease, not just from premature
mortality.
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Morbidity and Quality of Life
in Poor Households
(DisabilityAdjusted Life
Years)
DALY burden
(Millions of yrs lost each yr)*
Disruption to
quality of life &
economic productivity
caused by
premature deaths &
loss of healthy life
caused by
illness/disability.
• Problems occurring when
people live in poverty - eg,
90% DALY losses in the world
occur in developing countries.
• Also when living in
crowded conditions –
New global mega-cities where
managing human-generated
wastes is poor.
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Elephantiasis –
caused by parasitic
worm (& sometimes
persistent volcanic ash
exposure)
At any given time, about 2 billion people suffer from
worms, protozoans, and other internal parasites.
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Emergent Diseases
• An emergent disease is one never known
before, OR has been absent for at least 20
years.
– An important factor in the spread of many
diseases is speed and frequency of
modern travel.
• Foot and Mouth Disease
• Ebola
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Recent outbreaks of lethal
infectious diseases
At least 30 new infectious diseases have appeared in the past two
decades while many well-known have reappeared in more virulent, drugresistant forms.
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Factors Contributing to the Spread
of Contagious Diseases
• High population densities
• Contact with water or food that has been
contaminated by human waste
• Settlers pushing into remote areas
• Human-caused environmental change
(elimination of predators increasing rodents,
use of fertilizers & pesticides,
deforestation, etc)
• Speed and frequency of modern travel
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Emerging Ecological Diseases
• Domestic animals and wildlife also
experience sudden and widespread
epidemics.
– Distemper (Seals)
– Chronic Wasting Disease (Deer and Elk)
• Transmissible Spongiform Encephalopathies
– Black Band Disease (Coral)
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Emerging Disease
Distemper in Seals
• Virus
• Causes Labored breathing,
neurological problems and
fever
• Seals suffer from immunity
defect - caused by toxic
waste
Chronic Wasting Disease in
Deer and Elk
• Virus - Neurological disease
• Produces lesions in the brain
• Similar to Mad Cow disease
• Transmitted through
contact
• Transmission through
contaminated water or soil
Antibiotic and Pesticide Resistance
• Indiscriminate use of
antibiotics and pesticides –
perfect recipe for natural selection
– Protozoan that causes malaria now resistant
to most antibiotics, and mosquitoes have
developed resistance to many insecticides
– Drug resistance: TB, Staph A (eg, flesheating bacteria)
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Toxic Chemicals
• Hazardous chemicals – dangerous (eg, flammables,
explosives, irritants, acids, etc)
• Toxins – poisonous, kills cells
• Allergens – activate the immune system
• Neurotoxins – metabolic poisons affecting nerve cells
• Mutagens – chemicals or radiation that damage/alter
genetic material (DNA)
• Teratogens - chemicals or other factors that cause
abnormalities during embryonic growth &
development
• Carcinogens – substances that cause cancer (out of
control cell growth)
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Toxins:
Movement,
Distribution,
Fate
Depends upon:
• molecular size,
• solubility,
• stability, &
• reactivity,
Organisms affected by:
• amount of dose,
• route of entry,
• timing of exposure, &
• sensitivity of organisms
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Many routes of synthetic chemicals traveling through the environment
(Brennan & Withgott 2005)
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DDT
(dichloro, diphenyl, trichloroethane
pesticide
Bioaccumulation
and
Biomagnification
• Bioaccumulation – selective
absorption & storage of
molecules; dilute toxins in the
environment can reach
dangerous levels inside cells and
tissue
• Biomagnification - large
number of organisms at a lower
trophic level accumulates toxin
and toxin is concentrated in a
predator at a higher trophic level
(concentrates as it moves up the
food chain)
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Rachel Carson - A Voice for Nature
• In 1962, Silent Spring alerted
the public to the dangers of
indiscriminate pesticide use.
• Carson called for selective,
ecologically sound use of
pesticides.
• All 12 of the most toxic
agents in her book were
banned or severely restricted.
Peregrine falcons disappeared from the eastern U.S. in
1960s due to excess pesticide use
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“DDT (dichlorodiphenyltrichloroethane)
Powerful Insecticide, Harmless to
Humans”
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Pesticides and Child Development in Mexico’s Yaqui Valley
• Elizabeth Guillette
(anthropologist) – (Less exposure to pesticides)
1994
• Valley farmers
used pesticides but
foothill farmers
continued
traditional farming
• Valley children
were far behind
foothill children
developmentally in:
 Coordination
 Physical
endurance
 Long-term
memory
 Fine-motor
skills
(More exposure to pesticides)
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(Brennan & Withgott 2005)
Minimizing Toxic Effects
• Every material can be poisonous under some
conditions
• Taken in small doses, most toxins can be
broken down or excreted before they do
much harm – belief in 1800s, arsenic
(Napoleon)
• Liver - primary site of detoxification
• Tissues and organs - high cellular
reproduction rates replace injured cells down side: tumors, cancers possible
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Measuring Toxicity
Animal Testing
• Most commonly used and widely accepted
• Expensive - hundreds of thousands of
dollars to test one toxin at low doses
• Time consuming
• Often very inhumane
• Difficult to compare toxicity of unlike
chemicals or different species of organisms
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A Typical Dose/Response Curve
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Acute Lethal Doses for Some Toxic Organic Chemicals
mouse
rat
It is useful to group materials according to their
relative toxicity. (~ 31 billion ng/oz)
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Acute Versus Chronic
Doses and Effects
• Acute effects - immediate health effect caused
by a single exposure to a toxin (effects are
reversible if survive)
• Chronic effects - long lasting (or permanent)
health effect caused by:
– a single exposure to a very toxic substance
(experiments generally done this way),
OR
– continuous or repeated sub-lethal exposures to a
toxin (experiments using this level are expensive and time
consuming)
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Risk Assessment and
Acceptance
• Risk = probability of harm X probability of exposure
• A number of factors influence how we
perceive relative risks associated with different
situations
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interests as industrialist vs environmentalist,
understanding probability,
personal experience,
our abilities to control our fate,
news media biases,
fear of technology
• Accepting risks - we go to great lengths to avoid
some dangers, while gladly accepting others
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Risks of Death
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McKinney & Schoch
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Establishing Public Policy
In setting standards for environmental
toxins, we need to consider:
• Combined effects of exposure to many different
sources of damage (synergistic effects of
different toxins, eg
the smoking & asbestos effects on lung cancer
rates)
• Different sensitivities of members of the
population
• Effects of chronic as well as acute exposures
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Regulatory Decisions – EPA framework
The Science Specific to the
Problem
Other Factors Not
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Specific to the Problem
Relative Risks to Human Welfare
How about RISKS to the environment regardless of effects on humans?
Relative Risks to Human Welfare
Cunningham & Cunningham 2002
• How do we determine what the risk is from different
physical/ chemical changes in the environment?
• How much of the ranking is based on our values –
• do they reflect the science?
• do they reflect concern for the environment?
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Summary:
• Environmental Health Hazards
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Infectious Organisms
Emergent Diseases
Antibiotics and Pesticide Resistance
Toxic Chemicals
Distribution and Fate of Toxins
Minimizing Toxic Effects
Measuring Toxicity
Risk Assessment
Public Policy
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