Chapter 14, Risk and Toxicology Know the different types of hazards Understand the role of disease...
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Transcript of Chapter 14, Risk and Toxicology Know the different types of hazards Understand the role of disease...
Chapter 14, Risk and ToxicologyKnow the different types of hazardsUnderstand the role of diseaseKnow what toxicology is
Types of Hazards
Environmental 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
Types of Hazards
Chemical 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
Types of Hazards
Cultural = 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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Toxicants come in different types
Neurotoxins = assault the nervous systemAllergens = over stimulate the immune system
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
Routes of chemical transport
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
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
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
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