Transcript physical hazards

AP Environmental Science
Risk, Toxicology and
Human Health
© Brooks/Cole Publishing Company / ITP
Outline
1. Risks and Hazards
definitions, major types
2. Toxicology
bioaccumulation, toxicity, dose–response curves
3. Chemical Hazards
mutagens, teratogens, carcinogens, hormone disrupters
4. Physical Hazards
earthquakes, volcanoes, ionizing radiation, EM radiation
5. Biological Hazards
diseases, controlling disease
6. Risk Analysis
how to estimate risk, major risks, managing risks
© Brooks/Cole Publishing Company / ITP
1. Risks and Hazards
Risk is the possibility of suffering harm from a hazard
that can cause injury, disease, economic loss or
environmental damage.
•risk expressed as a probability;
•1 in 250
• risk assessment involves using data, hypotheses and
models to estimate the probability of harm to human
health, society, or the environment that may result from
exposure to specific hazards;
• risk management involves deciding how or whether to
reduce a possible risk to a certain level and at what cost.
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Major Hazards
There are four major types of hazards:
• cultural hazards, such as unsafe working conditions,
smoking, poor diet, drugs, drinking, driving, criminal
assault, unsafe sex and poverty;
• chemical hazards from harmful chemicals in air, water,
soil and food;
• physical hazards, such as noise, fire, tornadoes,
hurricanes, earthquakes, volcanic eruptions, floods and
ionizing radiation;
• biological hazards from pathogens, pollen and other
allergens and animals, such as bees and poisonous
snakes.
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Causes of Death
Tobacco use is the leading cause of preventable death
(data from 1993).
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2. Toxicology
Toxicology is the study of the adverse effects of
chemicals on health.
• toxicity is a measure of how harmful a substance is.
Toxicity depends on several factors;
• the amount of a potentially harmful substance that is
ingested, inhaled, or absorbed through the skin is called
the dose;
• frequency of exposure;
• who is exposed (adult or child);
• how well the body’s detoxification system (liver, lung,
kidneys, etc.) work
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Toxicology
The resulting type and amount of damage to
health are called the response
Two types of responses:
acute effect: immediate or rapid harmful reaction,
e.g., dizziness, rash, death;
chronic effect: permanent or long–lasting
consequence, e.g., asthma, kidney damage, heart
disease;
Toxicology
Five major factors can determine the harm
caused by a substance

Solubility
water-soluble toxins move through the
environment and get in the water supply
fat-soluble toxins can penetrate cell membranes
and accumulate in body tissue

Persistence
some chemicals are resistance to breakdown and
have long-lasting harmful effects on people and
wildlife

Bioaccumulation and biomagnification
see next slide
Bioaccumulation and
Biomagnification
The pesticide DDT becomes increasingly concentrated high in the
food chain because it is stored in fatty tissue and not easily broken
down or excreted.
• Bioaccumulation
results when the
concentration of a
chemical in specific
organs or tissues is
higher than would
normally be expected.
• Biomagnification
involves magnification
of concentrations as
they pass through the
food chains and webs.
© Brooks/Cole Publishing Company / ITP
Toxicology

Chemical Interactions
antagonistic interactions reduce harmful effects

Vitamin A and E apparently reduces some cancercausing chemicals
synergistic interactions multiplies harmful effects

asbestos workers have a 20-fold increased chance of
getting lung cancer, but if they smoke they have a 400fold increased in lung cancer rate
Determining Toxicity
Toxin or poison is a chemical that adversely affects
the health of a living human or animal by causing
injury, illness, or death
Three methods of determining toxicity:
• case reports (usually to physicians) about health effects
after exposure to a chemical;
• epidemiology, involving studies of populations exposed
to certain chemicals or diseases
• laboratory investigations (usually with test animals);
- LD50 is the median lethal dose, the amount of a chemical
received that kills 50% of animals (usually rats or mice) in a
test population (usually 60–200 animals) within a 14–day
period;
- a poison is legally defined as a chemical that has an LD50
of 50 milligrams or less per kilogram of body weight.
Toxicity
Lethal Dose
Toxicity
LD50
Super
< 0.01
less than 1 drop
dioxin, botulism
mushrooms
<5
less than 7 drops
heroin, nicotine
Very
5-50
7 drops to 1 tsp.
morphine, codeine
Toxic
50-500
1 tsp.
DDT, H2SO4, Caffeine
Moderate
500-5K
1 oz.-1 pt.
aspirin, wood alcohol
Slightly
5K-15K
1 pt.
Non-Toxic
>15K
>1qt.
water, table sugar
***Higher LD50, less toxic the substance is
Extreme
Examples
ethyl alcohol, soaps
(LD50 measured in mg/kg of body weight)
Dose–Response Curves
Dose–response curves show the adverse effects of
various doses of a toxic agent on a test population by
plotting harmful effect as a function of dose.
The left dose–
response curve shows
increasing harmful
effects with dose, and
no dose is considered
safe. The right
example has a
threshold, such that
low doses are
considered safe.
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Why so little is known of toxicity
Only 10% of at least 75,000 commercial
chemicals have been screened
 ~2% determined to be carcinogen, teratogen or
mutagen
 >1000 new synthetic chemicals added per year
 >99.5% of US commercial chemicals are NOT
regulated

3. Chemical Hazards
What are toxic vs. hazardous chemicals?
• toxic chemicals are generally defined as substances
that are fatal to over 50% of test animals (LD50) at given
concentrations.
• hazardous chemicals cause harm by
- being flammable or explosive (e.g., gasoline);
- irritating or damaging the skin or lungs (e.g., strong acids or
alkalines such as oven cleaners);
- interfering with or preventing oxygen uptake and
distribution (e.g., carbon monoxide, CO);
- inducing allergic reactions of the immune system
(allergens).
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Hazardous chemicals
• mutagens are agents, chemicals and radiation that
cause random mutations, or changes in the DNA;
• teratogens are agents (chemicals, radiation, or viruses)
that cause birth defects;
e.g., PCBs, steroid hormones, heavy metals; rubella,
mercury in water, fetal alcohol syndrome and crack
babies
• carcinogens are agents (chemicals, radiation, or
viruses) that cause cancer;
- over 100 types of cancer (depending on cells involved);
- e.g., cigarette smoke.
- hormone disrupters
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Hormone Disrupters
Each type of hormone has a
unique molecular shape that
allows it to attach to special
receptors of cells (upper
left).
Hormone disrupters (mimics
and blockers), attach to
receptors and disrupt/alter
development (upper right).
© Brooks/Cole Publishing Company / ITP
Hormone Disrupters
Hormones are molecules that act as messengers
in the endocrine system to regulate reproduction,
growth and development. Hormone disrupters
interfere with hormone function.
• So far 51 chemicals, many widely used, have been
shown to act as hormone disrupters on wildlife,
laboratory animals and humans;
- e.g., dioxins, certain PCBs, various chemicals in
plastics, some pesticides, lead and mercury;
• 1997 study shows that sperm count of men in U.S.
and Europe has declined 50%.
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Taking Precautions
Precautionary Principle:


New chemicals and technologies would be
assumed to be harmful until shown otherwise
Existing chemicals and technologies should
be removed from the market until their safety
can be established
Strictly applied precautionary principle
would not have given us automobiles,
antibiotics, and plastics.
No easy answer for knowing when to
apply precautionary principle
4. Physical Hazards
Earthquakes are
among various
types of natural
physical hazards.
Other physical
hazards include
volcanoes and
ionizing radiation.
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Physical Hazards
Map of expected
damage from
earthquakes.
Preventing loss:
• understand where risk
is high;
• establish building
codes to regulate
placement and design
of buildings in high
risk areas;
• determine if prediction
is feasible.
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Physical Hazards
Ionizing radiation, a form of electromagnetic
radiation, has enough energy to damage body
tissues.
Examples include X rays and ultraviolet radiation, and
various types of radiation emitted by radioactive
isotopes
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Physical Hazards
Natural and human
sources of the average
annual dose of ionizing
radiation received by the
U.S. population. Most
studies indicate that
there is no safe dose of
ionizing radiation.
© Brooks/Cole Publishing Company / ITP
Physical Hazards
Each year people are exposed to some radiation
from natural or background sources, as well as from
human–caused exposure.
• background sources include about 82% of the
exposure
• human–caused exposure include medical X rays
(10%), nuclear medicine (4%), and consumer products
(3%)
• harmful effects include burns, miscarriages, eye
cataracts and certain cancers
• serious accidents, such as at the Chernobyl reactor,
can release large quantities of radiation, far above
background levels.
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Physical Hazards
Is non-ionizing electromagnetic radiation harmful?
• we don't know
• concern that electromagnetic fields (EMFs) from
electrical appliances (e.g., microwave ovens, hair
dryers, electric blankets, computer and TV monitors)
may increase risk of some cancers, miscarriages, birth
defects and Alzheimer's disease
• many respected scientists say that a statistical link has
between established, but the evidence is still not
conclusive.
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5. Biological Hazards
Biological hazards include both non-transmissible
and transmissible diseases.
• non-transmissible diseases are not passed from one
person to another, e.g., cardiovascular disorders, most
cancers, diabetes, emphysema and malnutrition;
• transmissible diseases are caused by bacteria, viruses,
protozoa, or parasites, and can be passed from one
person to another, e.g., colds, flus, hepatitis, sexuallytransmitted diseases, malaria;
• some transmissible diseases are spreading over broad
geographic areas as the result of human activity;
- e.g., Lyme disease carried by ticks and spread by
people is now widespread over North America.
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Biological Hazards
Worldwide distribution
of malaria today (red)
and its projected
distribution in 2046
(orange). If the world
becomes warmer, as
projected by current
climate models, by
2046 malaria could
affect 60% of the
world’s population.
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Biological Hazards
The complex life cycle of
Plasmodium, the organism
that causes malaria, involves
transmission between
infected individuals by
Anopheles mosquitoes .
Malaria Video
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7 Deadliest Infectious Diseases
Case Study: Growing Germ
Resistance to Antibiotics
1 bacteria can produce 16,777,216
offspring in 24 hours

this allows them to become genetically resistant to antibiotics
through natural selection
Other factors that play a role in the
increase in serious infectious bacterial
diseases;



bacteria is spread around the globe by human travel and trade
goods
overuse of pesticides
overuse of antibiotics
Case Study: Growing Germ
Resistance to Antibiotics
Overuse of antibiotics



½ of all antibiotics are prescribed unnecessarily
antibiotics are available is some countries
without a prescription
In the U.S., 75% of all antibiotics used are fed to
livestock as feed additives to boost production.
resistant strains of infectious disease can spread to
humans through contact with infected animals

Every major disease-causing bacterium now has
strains that resist at least one of the roughly 160
antibiotics used to treat bacterial infections.
Case Study: The Global
Tuberculosis Threat
TB kills about 1.7 million people a year
and could kill 28 million by 2020
The bacterium causing TB moves from
person to person in airborne droplets
by sneezing, singing, or talking.

it has infected 1 in 3 people in the world
it in the body, whether you are sick or not
over ½ the infected people do not know they
are infected and do not feel sick
silent global epidemic
Case Study: The Global
Tuberculosis Threat
Increase in TB caused by




lack of screening and control programs
resistance to almost all effective antibiotics
population growth and urbanization causes increased contact
between people, especially among the poor
AIDS weakens immune system and allows TB to multiply
Can be cured by a combination of 4
inexpensive drugs



must be taken daily for 6-8 months
symptoms disappear, people think they are cured and stop
taking their medicine
this cause the disease to recur in a drug-resistant form
TB Evolution Movie
HIV, Flu, and Hepatitis B
HIV (human immunodeficiency virus)
transmitted by

unsafe sex, sharing of needles by drug users, infected
mother to offspring before or after birth, and exposure to
infected blood.
Influenza (flu) is transmitted by


body fluids
airborne emissions of infected persons
1918 Swine Flu
 Killed 500 million worldwide
 20 - 30 million in the U.S.
Today flu kills
 1 million per year worldwide
 20,000 in the U.S.
HIV, Flu, and Hepatitis B
Hepatitis B virus (HBV) damages the liver
and is transmitted by

unsafe sex, sharing of needles by drug users, infected
mother to offspring before or after birth, and exposure to
infected blood,
Other viruses that have received
widespread coverage




Ebola virus transmitted by blood or other body fluids
West Nile virus transmitted by mosquitoes that have been
feeding on infected birds
Severe Acute Respiratory Syndrome virus (SARS)
emerged in China in 2002 and is easily transmitted.
Uganda: Out of the Wild
HIV, Flu, and Hepatitis B
Viral infections are harder to fight than
infections caused by bacteria and
protozoa.



drugs that kill viruses also harm the cells of
the host
antibiotics are useless and increase genetic
resistance in bacteria
vaccines that stimulate the immune system to
produce antibodies to ward off viral infections
and help reduce the spread of viral diseases
polio, influenza, measles, smallpox, rabies, and
hepatitis B.
many viral diseases do not have vaccines

HIV
Biological Hazards
Generalized
model of the
epidemiological
transition that
may take place
as countries
become more
industrialized.
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Biological Hazards
What are some ways we reduce infectious
diseases?
• reduce overcrowding, unsafe drinking water, poor
sanitation, inadequate health care systems,
malnutrition and poverty;
• increase funding for disease monitoring;
• sharply reduce antibiotic use to prevent evolution of
resistant organisms;
• protect biodiversity as a means of reducing disease
spread;
• increase research.
• careful hand washing
6. Risk Analysis
Risk analysis involves identifying hazards and
evaluating associate risks (risk assessment), ranking
risks (comparative risk analysis), determining
options (risk management), and informing decision
makers and the public (risk communication).
• risk assessment estimates probabilities associated
with different types of hazards;
• comparative risk analysis summarizes the greatest
ecological and health risks
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Risk Analysis