Download - Chapter 14, Risk and Toxicology
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Chapter 14, Risk and ToxicologyKnow the different types of hazardsUnderstand the role of diseaseKnow what toxicology is
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Types of HazardsEnvironmental health = assesses
environmental factors that influence human health and quality of life◦ Including natural and human-caused factors
Physical hazards = occur naturally in our environment◦Earthquakes, volcanoes, fires, floods, droughts◦We can’t prevent them, but we can prepare for
them◦We increase our vulnerability by deforesting
slopes (landslides), channelizing rivers (flooding), etc.
◦We can reduce risk with better environmental choices
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Types of HazardsChemical hazards = synthetic
chemicals such as pharmaceuticals, disinfectants, pesticides◦Harmful natural chemicals (e.g., venom)
also existBiological hazards = result from
ecological interactions◦Viruses, bacteria, and other pathogens◦Infectious disease = species parasitize
humans, fulfilling their ecological roles◦Vector = an organism that transfers a
pathogen to a host◦We can’t avoid risk, but we can reduce
infection
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Types of HazardsCultural = result from where we live,
our socioeconomic status, our occupation, our behavioral choices◦We can minimize some, but not all, of
these hazards◦Smoking, drug use, diet and nutrition,
crime, mode of transportation◦Health factors (e.g., living near toxic
waste) are often correlated with poverty
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Radon = a highly toxic, radioactive gas that is colorless and undetectable ◦It can build up in basements
Asbestos = a mineral that insulates, muffles sounds, and resists fire
Indoor environmental health hazards
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Indoor environmental health hazards
Lead poisoning = caused by leadDamages the brain, liver, kidney, and stomach
Causes learning problems, behavior abnormalities, and death
Exposure is from drinking water that flows through lead pipes or from lead paint
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A recently recognized hazardPolybrominated diphenyl ethers
(PBDEs) = has fire-retardant properties◦Used in computers, televisions, plastics,
and furniture◦Persist and accumulate in living tissue◦Mimic hormones and affect thyroid
hormones◦Also affect brain and nervous system
development and may cause cancerConcentrations are rising in breast milk
◦Now banned in Europe, concentrations have decreased
◦The U.S. has not addressed the issue
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Disease is a major focus of environmental health
Despite our technology, disease kills most of us
Disease has a genetic and environmental basis◦Cancer, heart disease,
respiratory disorders◦Poverty and poor
hygiene foster illnesses
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Infectious diseases kill millions
Infectious diseases kill 15 million people/year◦Half of all deaths in developing
countriesMoney lets developed countries
have access to hygiene and medicine
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Infectious and noninfectious diseases
Lifestyles in developed nations affect diseases◦U.S. smoking dropped 38%◦But obesity has doubled
Public health decreases some infectious diseases◦Some (AIDS) are
spreading ◦Some develop
resistance to antibiotics
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Diseases, the environment, and society
• Our mobility spreads diseases - West Nile Virus spread
from Africa to all lower 48 U.S. states in 5 years
• New diseases are emerging- H5N1 avian flu, H1N1
swine flu• Climate change will expand the range
of diseases• To predict and prevent diseases, experts deal
with complicated interrelationships - In technology, land use, and ecology
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The best way to reduce disease? Improve the basic living conditions of the
poor◦Food security, sanitation, clean drinking water
Expanded access to health care◦Health clinics, immunizations, pre- and postnatal
careEducation campaigns work in rich and poor
nations◦Public service and governments give advice◦Packaging and ads advise us on smoking, etc.◦Sex and reproductive health education slows
population growth and spread of HIV/AIDS
Disease
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Toxicology studies poisonous substances
Toxicology = the study of the effects of poisonous substances on humans and other organisms
Toxicity = the degree of harm a toxicant can inflict
Toxicant = any toxic substance (poison)◦ “The dose makes the poison” = toxicity depends
on the combined effect of the chemical and its quantity
Environmental toxicology = deals with toxic substances that come from or are discharged into the environment◦Studies health effects on humans, other animals,
and ecosystems
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Balancing risks and rewards
There is a tradeoff between the risk and reward of most hazards◦We must judge how these compare◦We use Bisphenol A despite its health risks◦Are safer and affordable alternatives available?
Don’t forget, chemicals have given us our high standard of living◦Food, medicine, conveniences
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Toxic substances in the environment
The environment contains natural chemicals that may pose health risks
Toxins = toxic chemicals made in tissues of living organisms
But synthetic chemicals are also in our environment◦Every human carries traces of
industrial chemicals
The U.S. makes or imports 250 lb of chemicals for every person in the country
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Chemicals are in the air, water, and soil
80% of U.S. streams contain 82 contaminants◦Antibiotics, detergents, drugs, steroids,
solvents, etc.92% of all aquifers contain 42 volatile
organic compounds (from gasoline, paints, plastics, etc.)◦Less than 2% violate federal health standards
for drinking water
Pesticides are present in streams and groundwater in levels high enough to affect aquatic life
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Synthetic chemicals are in all of us
Every one of us carries traces of hundreds of industrial chemicals in our bodies◦Including toxic persistent organic
pollutants restricted by international treaties
Babies are born “pre-polluted” – 232 chemicals were in umbilical cords of babies tested
Not all synthetic chemicals pose health risks◦But very few of the 100,000 chemicals
on the market have been tested
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Silent Spring began the debate over chemicals
Rachel Carson’s Silent Spring (1962) showed DDT’s risks to people, wildlife, and ecosystems
Chemical companies challenged the book◦Discrediting Carson’s personal reputation
DDT was banned in the U.S. in 1973◦But is still made in the U.S. and exported
In the 1960s, untested pesticides were sprayed over public areas, with assumption they would do no harm
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Toxicants come in different types
Neurotoxins = assault the nervous systemAllergens = over stimulate the immune system
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Toxins may concentrate in water
Runoff carries toxins from land to surface water
Chemicals in the soil can leach into groundwater◦Contaminating drinking water
Chemicals enter organisms through drinking or absorption◦Aquatic organisms (fish, frogs, etc.) are good
pollution indicatorsContaminants in streams and rivers enter
drinking water and the air
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Routes of chemical transport
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Airborne substances can travel widely
Chemicals can travel by air◦Their effects can occur far from the site of use
Pesticide drift = airborne transport of pesticides
Synthetic chemicals are found globally◦In arctic polar bears, Antarctic penguins, and
people in Greenland
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Some toxicants persist
Toxins can degrade quickly and become harmless◦Or they may remain unaltered and persist for
decades◦Rates of degradation depend on the substance,
temperature, moisture, and sun exposureBreakdown products = simpler products
that toxicants degrade into◦May be more or less harmful than the original
substance◦DDT degrades into DDE, which is also highly
persistent and toxic
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Toxicants can accumulate and biomagnify
Toxicants in the body can be excreted, degraded, or stored◦Fat-soluble toxicants are stored in fatty
tissuesBioaccumulation = toxicants build up
in animal tissuesBiomagnification = concentrations of
toxicants become magnified◦Near extinction of peregrine falcons and
bald eagles
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Not all toxicants are synthetic
Toxic chemicals also exist naturally and in our food◦Don’t assume natural chemicals are all
healthy and synthetic ones are all harmfulSome scientists feel that natural
toxicants dwarf our intake of synthetic chemicals◦Natural defenses are effective against
syntheticsEnvironmentalists say synthetic
toxins:◦Are harder to metabolize and excrete◦Persist and accumulate◦Enter people in ways other than in food