Download Ch 14 PPT Pt. 2

ENVIRONMENTAL
HEALTH & TOXICOLOGY
Ch. 14
Part 2
This lecture will help you understand:
• Environmental health and hazards
• Toxic substances in the environment and factors that
affect their toxicity
• Defenses organisms posses against toxic substances
• Movement of toxic substances and their affect on
ecosystems
• Hazards and their effects
• Risk assessment and risk management
• Philosophical approaches to risk
• Regulatory policy in the United States and internationally
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 have some genetic basis
• Air pollution, poverty, and poor hygiene foster illnesses
• Noninfectious diseases cause over half of the world’s deaths
• Infectious diseases account for 1 in 4 deaths
Disease is a major focus of environmental
health
• Where you live determines your disease
• Infectious disease causes half of all deaths in developing countries
• Money lets developed countries have access to hygiene and
medicine to combat these diseases
• Lifestyles in developed nations affect diseases
• U.S. smoking dropped 42%, obesity has more than doubled
• Public health efforts decrease some infectious diseases
• But some (AIDS) are spreading
• Some develop resistance to antibiotics
Social and environmental factors can
influence the spread of infectious disease
• Our mobility spreads diseases worldwide
• Severe acute respiratory syndrome (SARS) in 2003
• H1N1 swine flu in 2009–2010
• Climate change will expand the range of diseases
• New disease threats may arise
• Some pathogens evolve rapidly
• Humans can alter existing diseases to make them more
deadly—bioterrorism is a growing concern
We are fighting disease with diverse
approaches
• One of the best way to reduce disease is to improve the
basic living conditions of the poor
• Food security, sanitation, clean drinking water
• Also, provide expanded access to health care
• Health clinics, immunizations, pre- and postnatal care
We are fighting disease with diverse
approaches
• Education campaigns work in rich and poor nations
• Agencies, organizations, and governments work together
• The United Nations, the World Health Organization, U.S. Agency
for International Development, etc.
• Private organizations donate millions of dollars
PLAY PANDEMIC TO LEARN MORE ABOUT HOW DISEASE SPREADS:
http://www.crazymonkeygames.com/Pandemic-2.html
Toxicology is the study of chemical
hazards
• 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
~.095g a cup
5-10g could kill you…
that’s more than 6
gallons of McDonald's
coffee
Toxicology is the study of chemical
hazards
• We have been adding increased amounts and numbers of
chemicals into the environment
around us
• Environmental toxicology = deals with toxic substances
that come from or are discharged into the environment
• Studies health effects on humans, other animals, and ecosystems
Many environmental health hazards exist
indoors
• Americans spend roughly 90% of their lives indoors
• Radon = a highly toxic, radioactive gas that is colorless
and undetectable
• Can build up in basements
• Found in areas with certain types of bedrock (decaying
uranium)
• Asbestos = a mineral that insulates, muffles sounds, and
resists fire
• Asbestosis = disorder that occurs when inhaled crystals of
asbestos cause scarred lungs that cease to function
• Can lead to lung cancer
Many environmental health hazards exist
indoors
• Lead poisoning = caused by lead, a heavy metal
• Damages the brain, liver, kidney, and stomach
• Causes learning problems, behavior abnormalities, and
death http://www.vox.com/a/lead-exposure-risk-map
• Exposure is from drinking water that flows through lead
pipes or from lead paint
• Efforts in the United States have led to declines in poisoning,
but China still used lead paint in toys until recently
• In 2012, the Centers for Disease Control (CDC) cut the
danger threshold for lead in children’s blood from 10 to 5
micrograms/deciliter
Many environmental health hazards exist
indoors
• Polybrominated diphenyl ethers (PBDEs) = a group of
chemicals with 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
cancer
• Concentrations are rising in breast milk
• Now that they’re banned in Europe, concentrations have decreased
• The United States has not addressed the issue
Toxic Substances and Their Effects on
Organisms
• The environment contains natural chemicals that may pose
health risks
• Toxins = toxic chemicals made in tissues of living organisms
• Chemicals plants use to defend themselves
Synthetic chemicals are all around
us—and in us
• A 2002 study found that 80% of U.S. streams contain 82
contaminants
• Antibiotics, detergents, drugs, steroids, solvents, etc.
• A 2006 study of groundwater found 18% of wells and 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
not high enough to affect human health
• But high enough to affect aquatic life
Synthetic chemicals are in all of our
bodies
• 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
• Nine out of 10 umbilical cords contained BPA
• Not all synthetic chemicals pose health risks
• But very few of the 100,000 chemicals on the market have been
thoroughly tested
Silent Spring began the public debate
over synthetic chemicals
• Rachel Carson’s Silent Spring (1962) showed DDT’s risks to
people, wildlife, and ecosystems
• Gathered and presented scientific studies, medical cases, and other data
• Chemical companies challenged the book
• Attacked Carson’s science and personal reputation
• DDT was banned in the United States in 1973
• But is still made in the United States and exported
• Used to control disease vectors in developing countries (reward is
greater than risk)
• New technologies may stop disease without DDT
Not all toxicants are synthetic, and not all
synthetic chemicals are toxic
• Toxic chemicals also exist naturally and in our food
• It would be a mistake to assume natural chemicals are all healthy
and synthetic ones are all harmful
• Plants produce toxic chemicals to defend themselves
• Most crop plants have had the level of toxic chemicals reduced by
artificial selection, but not eliminated
• Eating animals may expose us to the plant chemicals they ate
• Bioaccumulation
Toxic substances come in different types
• Carcinogens = substances that cause cancer
• Cells grow uncontrollably, damaging the body
• Prevalence of environmentally induced cancer has been underestimated
• Hard to identify because of the long time between exposure and onset of
cancer and because not everyone exposed gets cancer
• Mutagens = substances that cause DNA mutations
• Most mutations have no effect, but some can cause cancer
• If they occur in sperm or eggs, can impact offspring
Toxic substances come in different types
• Teratogens = chemicals that cause birth defects in
embryos
• Thalidomide caused birth defects in the 1960s
• Neurotoxins = toxicants that assault the nervous system
• Animal venoms, heavy metals, pesticides, and chemical weapons
Toxic substances come in different types
• Allergens = toxicants that overactivate the immune
system
• Cause an immune response when one is not needed
• Increase in asthma in recent years may be due to increased
prevalence of allergenic chemicals
• Not universally considered toxicants since they only affect some
people and not others
Toxic substances come in different types
• Pathway inhibitors = toxicants that interrupt vital
biochemical processes by blocking one or more steps in
pathway
• The herbicide atrazine blocks steps in photosynthesis
• Endocrine disruptors = toxicants that affect the
endocrine (hormone) system = chemical messenger
system
Toxic substances come in different types
• Hormones stimulate growth, development, sexual maturity
• Work with extremely small concentrations
• Synthetic chemicals interfere with normal signals
• Block hormones, preventing signals from working
• Mimic hormones, causing a change
• Many mimic female sex hormones
Organisms have natural defenses against
toxic substances
• Organisms were exposed to toxic substances before humans
starting producing them
• Heavy metals occur naturally; plants and animals produce toxic
chemicals
• Exposure has driven selection for organisms that can tolerate
these toxins
• Barriers (skin, scales, feathers) prevent uptake
• Biochemical pathways break down toxicants or are changed for
easier excretion
• Some toxicants can not be broken down and are instead
stored in fatty tissue (DDT)
• Defenses only work at low levels of toxicants
Individuals vary in their responses to
hazards
• Different people respond differently to hazards
• Affected by genetics, surroundings, etc.
• People in poor health are more sensitive
• Sensitivity also varies with sex, age, and weight
• Fetuses, infants, and young children are more sensitive
Individuals vary in their responses to
hazards
• The Environmental Protection Agency (EPA) sets
standards for responses based on adult responses
• Extrapolate adult responses to smaller size for children, infants
• Scientists argue that standards are not low enough to protect
babies
The type of exposure affects the response
• Acute exposure = high exposure to a hazard for short periods
of time
• Easy to recognize
• Stems from discrete events: ingestion, oil spills, nuclear accident, etc.
• Chronic exposure = low exposure for long periods of time
• More common but harder to detect and diagnose
• Affects organs gradually: lung cancer, liver damage
• Cause and effect may not be easily apparent due to time between onset
of exposure and symptoms