Download Environmental Hazards & Human Health

Chapter 14
Environmental Hazards
& Human Health
What major health hazards do we face?
RISK - is the probability of suffering harm
from a hazard that can cause injury,
disease, death, economic loss, or damage.
(normally expressed in terms of probability)
Lung cancer kills 1
in 250 who smoke a
pack per day.
RISK ASSESSMENT is the process of using
statistical methods to
estimate how much
harm a particular
hazard can cause to
human health or to the
environment.
RISK MANAGEMENT involves deciding whether or
how to reduce a particular
risk to a certain level and at
what cost.
Different Hazards Include :
BIOLOGICAL HAZARDS - bacteria / viruses / parasites /
protozoa / fungi...
CHEMICAL HAZARDS - harmful chemicals found in air /
water / soil / food / human made products...
PHYSICAL HAZARDS - include fires / earthquakes /
volcanic eruptions / floods / storms...
CULTURAL HAZARDS - include unsafe working
conditions / unsafe highways / criminal assaults /
poverty...
LIFESTYLE CHOICES - such as smoking / poor food
choices / drinking too much alcohol / having unsafe
sex...
What types of biological hazards do we face?
NONTRANSMISSIBLE DISEASE - is caused by something
other than a living organism and does not spread from
one person to another; they tend to develop slowly.
INFECTIOUS DISEASE - is caused
when a pathogen such as a bacterium,
virus or parasite invades the body and
multiplies it's cells and tissues.
Danga
TRANSMISSIBLE DISEASE - (also
called a contagious disease) is an
infectious disease that can be
transmitted from one person to another.
INFECTIOUS DISEASES ARE STILL MAJOR
HEALTH THREATS
Diseases, especially in developing
countries are spread through air, water,
food, and body fluids like feces, urine,
blood and droplets sprayed by sneezing
and coughing.
A growing problem is
that many diseasecarrying bacteria
have developed
genetic immunity
to widely used
antibiotics.
DEATHS PER YEAR
PNEUMONIA
AND FLU
HIV/AIDS
TUBERCULOSIS
DIARRHEAL
DISEASES
MALARIA
HEPATITIS
B
MEASLES
3.2
2.0
1.8
1.6
1
1
800,000
MILLION
MILLION
MILLION
MILLION
MILLION
MILLION
influenza pandemic of 1918 --->
viruses :
-evolve quickly
-are not effected by antibiotics
-can kill large numbers of people
Biggest killer = influenza or the flu virus; transmitted by
body fluids or airborne emissions of an infected person.
MALARIA : Spread by certain mosquito species
It infects red blood
cells, causing :
-fever
-chills
-drenching sweats
-anemia
-severe abdominal
pain
-vomiting
-extreme weakness
-greater
susceptibility to
other diseases.
Malaria killer at least 2,700 people per day. 90% who die are
under the age of 5, and those who survive suffer brain
damage or impaired learning ability.
Good News :
"According to WHO, the
global death rate from
infectious diseases
decreased by more than 2/3
between 1970 and 2006 and
is projected to continue
dropping."
You can greatly reduce your chances of getting infectious disease by
practicing good hygiene:
-washing hands thoroughly and frequently
-avoid touching your face
-stay away from people who have the flu or other viral diseases
What types of chemical hazards
do we face?
Toxic Chemicals
A chemical that can cause temporary or
permanent harm or death to humans and
animals
Top 5 toxic substances according to the
EPA:
arsenic
lead
mercury
vinyl chloride (PVC plastics)
polychlorinated biphenyls (PBCs)
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Carcinogens
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Chemicals,
types of
radiation, or
certain viruses
that can cause
or promote
cancer
(arsenic,
choloroform,
formaldehyde,
gamma radiation, xrays, etc.)
In 2007 there were at least
12 million new cancer cases
and 7.6 mission cancer
deaths.
time gap (10-40 years)
Mutagens
Chemicals or
forms of radiation
that cause
mutations in DNA
or that increase the
frequency of such
changes
(nitrous acid - food
preservative)
Tetragens
Chemicals that cause harm or birth defects
to a fetus or embryo
(benzene, lead,
mercury, PCBs
phthalates,
formaldehyde,
cadmium, vinyl cholride)
How Are We Affected?
•
Immune system weakened against bacteria, viruses, and protozoa
•
Nervous system (brain, spinal cord, peripheral nerves) affected by
nuerotoxins such as nethyl mercury, arsenic, and some pesticides
o behavioral changes
o learning disabilities
o ADD
o paralysis
o death
•
Endocrine system (hormones) affected by chemicals shaped similarly
to hormones that fit in their relative receptors, which messes with
hormonal balance. these molecules are called hormonally active
agents or hormone blockers (gender benders)
o turn on and off bodily systems controling sexual reproduction,
growth, development, learning ability, and behavior
How can we evaluate chemical
hazards?
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Toxicology: The study of harmful effects of
chemicals on humans and other organisms
Toxicity: A measure of the harmfulness of a
substance (ability to cause illness)
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If you ingest a large amount of anything, it
becomes toxic.
Dose: the amount of harmful chemical that a
person has ingested
Factors leading to hazardous
chemical effects
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Genetic Makeup
Age
"Multiple Chemical Sensitivity"
How well the body's detoxification organs
function
Chemical solubility
Persistence
Biological Magnification (Toxins increase as
they pass through trophic levels)
Response to Chemicals
Damage to health resulting from exposure to
chemicals is called response.
Acute effects: Sudden
Chronic effects: Long-lasting
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Testing for Toxicity
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Lab animals and organisms
2-5 years, hundreds of animals and cost
millions.
Toxicity estimated on dose-response curve
Dose=x-axis
percentage killed=y-axis
Methods to replace animal testing
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Computer simulations
Using tissue cultures of cells instead of
actual animals
Controversy behind animal testing is huge
Problems estimating toxicity
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It is difficult to determine what single
substance is toxic in a compound of many
substances
Separating these harmful chemicals from
others takes time and money
Case reports provide info about people
suffering illness after exposure to a chemical
Can be inaccurate because all info is not
known (dose size, etc)
Trace Levels of chemicals
•
•
Trace levels of chemicals are in almost
anything
Not enough data to determine if harmful or
not
Knowledge About Harmful
Effects of Chemicals
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"Toxicologists know a great deal about a few
chemicals, a little about many, and next to
nothing about most"
Only 10% of 100,000 registered chemicals
have been tested for toxicity and only 2%
have been ID'd as carcinogens, mutagens,
or teratogens
Because of insufficient data and high costs,
the US government doesn't regulate 99.5%
of chemicals
Protection from Chemicals
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Many scientists are currently pushing for
pollution prevention, which means testing
everything before releasing it.
Precautionary Principle is when there is
not enough data or research and reasonable
doubt that the chemical is harmful, we
shouldn't release it.
Ethical responsibility
Too expensive to produce any new products
Controversy on how far we should take this
How do we perceive risks & how can we
avoid the worst of them?
Risk Analysis
- Identifying hazards
and evaluating their
associated risks
- Statistical probabilities
based on past experience,
animal testing, and other
tests are used to calculate
risks
Risks Today
- The biggest risk right now in the United States
is poverty.
- Smoking cigarettes is the world's most
preventable cause of suffering and premature
deaths today.
People do a poor job of risk evaluating
1. Fear effects the way people think of risks, and can make
them overestimate the risks.
2. We feel more impacted by a single catastrophic event than
less significant but more total death events like the death toll
from smoking every year.
3. The degree of control we have also effects how we
perceive risks.
Optimism Bias: the
belief that risks that apply
to other people do not
apply to them.
- We take some risks for
instant gratification. For
example, eating bad foods
and smoking.
Evaluate and Reduce Risks
- Compare risks: ask yourself "how risky is it
compared to other risks?"
- Determine how much risk you are willing to
accept: 1 in 100,000 chance of dying may be
too risky, but 1 in 1,000,000 may not be.
Determine the actual risk involved:
Most people believe the world is more risk filled than it
really is due to the media.
We face tons of infectious and hazardous
diseases such as the flu, AIDS, tuberculosis
and malaria. We are exposed to chemicals
that can cause cancers and birth defects and
disrupt the human immune, nervous, and
endocrine systems.
Since we can't fully evaluate the harm caused by
exposure to chemicals, many health scientists call
for greater emphasis on pollution prevention.
- Being informed, thinking critically about risks, and
making careful choices can reduce major risks.