Download Chapter 18 - Environmental Hazards and Human

Risk and Toxicology
Chapter 18
Smoking in the US
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Smoking is the number one killer in the US
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Worldwide, infectious disease is the number
one killer. (This includes TB, HIV, malaria,
flu, measles, cholera, and yellow fever.)
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One study shows that adolescents who smoke
more than 1 cigarette have an 85% chance of
becoming smokers.
Risk
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Risk is the possibility of suffering from a
hazard
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A hazard may cause economic loss,
environmental loss, injury, disease or death
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Risk = exposure X harm
Hazards
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Cultural – diet, drugs, drinking, driving, criminal
assault, unsafe sex, and poverty
Chemical – harmful chemicals in air, water, food and
soil. Most people carry around 500 synthetic
chemicals in their bodies, whose effects are currently
unknown. (buy organic)
Physical – ionizing radiation, fire, earthquakes,
floods, volcanoes, hurricanes, etc.
Biological – pathogens, pollens, allergens, animals
that bite or sting, parasites
Toxicology
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Toxicity – measure of how harmful a
substance is.
Dose – the amount substance introduced to the
body
Vector - agent of disease transmission
Not all people are affect the same by the same
dose
Number of individuals affected
Very
Sensitive
0
Majority
of population
20
40
Very
Sensitive
60
80
Dose (hypothetical units)
Fig. 16.3, p. 398
Bioaccumulation
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Some substances are fat or oil soluble (usually
organic compounds) and can be stored in body
tissues and cells.
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When a substance is ingested in very small
doses, but is stored in the body, it accumulates
to a higher dose over time (bioaccumulation)
Biomagnification
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When a substance that bioaccumulates is
passed up the food chain, each trophic level
receives a higher dose of the substance
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This is biomagnification
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Animals at the top of the food chain can be
exposed to very high doses and hence are
usually affected the most (birds and fish)
DDT in fish-eating
birds (ospreys)
25 ppm
DDT in large
fish (needle fish)
2 ppm
DDT in small
fish (minnows)
0.5 ppm
DDT in
zooplankton
0.04 ppm
DDT in water
0.000003 ppm,
Or 3 ppm
Fig. 16.4, p. 399
Major Bioaccumulants
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DDT
PCB’s (a class of oily chemicals used in
electrical transformers)
Radioactive isotopes (strontium-90)
Dioxin
Other organo-chlorides
Poison
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A poison is a substance that has an LD50 of 50
or less.
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LD50 stands for the lethal dose in milligrams of
a substance that kills 50 percent of the test
organisms (usually rats and mice) per kilogram
of body weight.
So 50 milligrams of “poison” will kill 50
percent of organisms weighing 1 kilogram
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Percentage of population killed by a given dose
100
75
50
25
LD
0
2
4
6
8
50
10
12
Dose (hypothetical units)
14
16
Fig. 16.5, p. 400
Dose-response curve
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Different substance act at different rates and at
different concentrations.
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The data of the response tells a lot about the
toxicity of a substance
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Substances without threshold levels cause
harm even at small doses
Nonlinear
dose-response
Linear
dose-response
Linear
dose-response
Effect
Effect
Nonlinear
dose-response
Threshold
level
Dose
No threshold
Dose
Threshold
Fig. 16.6, p. 401
Toxicity for humans
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Supertoxic – less than .01 – nerve gas, dioxin
Extremely toxic – less than 5 – nicotine,
heroin, atropine, potassium cyanide, parathion
Very toxic – 5-50 – morphine, codeine,
mercury salts
Toxic – 50 – 500 – Lead salts, DDT, carbon
tetrachloride, caffeine, sulfuric acid
Moderately toxic – 500 – 5,000
Slightly toxic – 5,000 – 15,000
Chemical Hazards
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Toxic chemicals are those that are fatal to 50%
of the test population at given concentrations
Hazardous chemicals cause harm by:
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Being flammable or explosive
Irritating or damaging skin or lungs - acidic/basic
Interfering with oxygen uptake - asphyxiants
Inducing allergic reactions
Neurotoxins
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Can effect behavioral changes, learning
disabilities, ADD, paralysis and death
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Examples
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PCBs - Polychlorinated biphenol
Methyl mercury
Arsenic
lead
Mutagens
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Agents (chemicals or other (ionizing
radiation)) that cause mutations in DNA
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Most mutations are harmless, but mutations in
sperm or egg cells can cause genetic defects
like Down’s syndrome, hemophilia, sickle cell
anemia, manic depression and thalasseamia
Mutations in other cells are not inherited, but
may still cause harm
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Teratogens
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Agents (chemicals, viruses, radiation) that
cause birth defects while the human embryo is
developing
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Especially during first trimester
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PCB’s, Thalidomide, Steroid hormones, and
metals (arsenic, cadmium, lead, and mercury)
Carcinogens
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Agents that promote growth of malignant
tumors
Cigarette smoke is a major agent in the US
Usually a lag time of 10 – 40 years from initial
exposure to development of cancer
Usually due to chronic exposure
Synthetic Chemicals
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Many synthetics can harm the brain and spinal cord
and peripheral nerves
Neurotoxins attack the nerve cells
Chlorinated hydrocarbons (DDT, PCBs, dioxin)
Organophosphate pesticide
Formaldehyde
Compounds of arsenic, mercury, lead, cadmium
Solvents (trichloroethylene (TCE), toluene and
xylene
Chemicals released each year
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The US releases more than 1,000 new synthetic
chemicals into the marketplace each year
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99.5% of these chemicals are not regulated by the
federal government
Only 2% of 85,000 synthetic chemicals are adequetly
tested
Chemicals can interact within the body or
environment to create new chemicals
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The Bodies Defenses
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Immune system - antibodies and cellular
defense - fights against disease and
harmful substances
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Endocrine system - regulate
hormones/growth and development
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Hormone mimics disrupt the endocrine sys
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Dioxins, PCB’s, DDT, lead, other pesticides
(especially chloronated hydrocarbons)
Transmissible diseases
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Transmissible diseases are caused by living
organisms
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These infectious agents are spread by air, water, food,
bodily fluid, insects and other vectors
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80% of illness in developing countries is from
waterborne infectious diseases (diarrhea, hepatitis,
typhoid fever, cholera) mainly from unsafe drinking
water and inadequate sanitation
7 Deadly Diseases
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According to WHO the seven deadliest infectious
diseases are:
Acute respiratory infection (pneumonia, flu)
HIV/ AIDS
Diarrheal diseases
TB tuberculosis
Malaria
Measles
Hepatitis B
Virus vs. Bacteria
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Viral disease
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AIDS
Ebola
Influenza
Rabies
Avian or bird flu
West Nile virus
SARS
Hepatitus B
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Bacterial disease
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Tuberculosis (TB)
Lyme disease
Pneumonia
Tuberculosis
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A highly infectious bacterial disease
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It is estimated that between 2006 and 2020 25
million people will die of tuberculosis, most of
which live in developing countries
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Half of the people infected with TB do not
know they have it and can infect another 10-15
people on average
Tuberculosis
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Population growth, urbanization, and air travel have
increased contact with TB
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Luckily four inexpensive drugs in combination can
cure 90% of cases, but the drugs must be taken every
day for 6-8 months
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Because symptoms disappear after a few weeks,
many patients stop taking the medication
Tuberculosis
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The incidence of TB has increased due to
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Increased size in population
Increased number of elderly in the population
Poverty
World travel
TB bacterium have developed resistance to
antiobiotics
Weakened immune systems (from AIDS and other
diseases)
Malaria
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Symptoms come and go and include: fever,
anemia, enlarged spleen, severe abdominal
pain, headaches, extreme weakness to other
diseases
Kills about 1.5 million each year, most under 5
Caused by parasitic protozoa (Plasmodium)
passed on typically by Anopheles mosquitoes
Reduction in Malaria
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Incidences of malaria were temporarily
decreased during the mid 1900’s
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Draining wetlands/swamps
Spraying DDT to kill mosquitos
Use of drugs to kill parasite in patients
Increased awareness of symptoms for early
treatment
Unfortunately, since 1970 malaria has risen due to
genetic resistance and deforestation
West Nile Virus
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Transferred to humans by mosquitos
It arrived in the US in 1999 (estimated)
Since then has spread coast to coast and
infected more than 1.2 million people
SARS
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Severe acute respiratory syndrome
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First appeared in 2002 in China
Flu-like symptoms that can quickly turn to
pneumonia (and death)
Spread quickly in 2003, but was contained by
WHO and other local agencies
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Lyme Disease
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Spread by deer ticks
Bacteria that attacks the nervous system
The bite from the tick leaves a red bulls-eye
target on the skin
With immediate antiobiotics the effects are
minimal
Poverty
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This is the greatest risk humans face
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Other than poverty, most people face the greatest risk
from their lifestyle choices
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Avoid risk – no smoking, avoid excess sun, low to
zero alcohol consumption, reduce cholesterol and
saturated fats, eat a variety of fruits and vegetables,
exercise, lose excess weight, and use safety
equipment (seatbelts, helmets, life jackets, etc)
The End
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Stay healthy
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Live long
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Enjoy life!
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