Risk, Human Health, and Toxicology

1
Risk, Human Health, and Toxicology

• Chapter 14
• PPT by Paddy Marshall, Kiyon Naser, and Jacob
  Brown

2
Key Concepts

• Types of risks and hazards people face
• Diseases in developed and developing countries
• Types of chemical hazards and how they are
  scientifically measured
• Estimating and perceiving risks, so as to protect
  the general public

3
The Big Killer

• Tobacco
• Health threats
• Nicotine
• Passive smoking
• Costs of smoking
• Anti-smoking programs

Fig. 14-1, p. 327
4
Risk and Hazards

• Risk-a measure of the likelihood that you will
  suffer harm from a hazard
• Probabilities-a mathematical statement about how
  likely it is to suffer harm from a hazard
• Possibilities-Do not convey any likelihood
• Ie. It is possible for a smoker to get lung
  cancer. Probability determines how likely this
  is
• Risk assessment-the scientific process of
  estimating how much harm a particular hazard can
  cause to human health
• Risk management-involves deciding whether or how
  to reduce a particular risk to a certain level
  and at what cost

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Risk Assessment and Risk Management
Risk Assessment
Risk Management
Hazard identification What is the
hazard? Probability of risk How likely is the
event? Consequences of risk What is the
likely damage?
Comparative risk analysis How does it
compare with other risks? Risk reduction How
much should it be reduced? Risk reduction
strategy How will the risk be reduced? Financial
commitment How much money should be spent?
Fig. 14-2, p. 328
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Major Types of Hazards

• Cultural-smoking, unsafe working conditions, poor
  diet, drugs, drinking, driving, criminal assault,
  unsafe sex, and poverty
• Biological-pathogens (bacteria, viruses, and
  parasites) that cause infectious disease
• Chemical-from harmful chemicals in the air,
  water, soil, and food
• Physical- fire, earthquake, volcanic eruption,
  flood, tornado, and hurricane

7
Biological Hazards

• Nontransmissible diseases-is not caused or
  transferred by living organisms
• Transmissible (infectious) diseases-a disease
  that is caused by living organisms, such as
  bacteria, viruses, and parasitic worms, and can
  spread from one person to another by air, water,
  food, or body fluids
• Pathogens-organism that produces disease (ex/
  bactera, viruses, parasites)
• Germ resistance to antibiotics-rapidly producing
  infectious bacteria can undergo natural selection
  and become genetically resistant to widely used
  antibiotics

8
Global Threats from Disease

• Tuberculosis-multiple strains have become
  genetically resistant to antibiotics
• Viral diseases-any disease caused by viruses
• HIV and AIDS-Human immune-deficiency virus. AIDS
  syndrome develops when lymphocyte count drops
  below 200 cells/micro liter
• Malaria-parasitic protozoan caused attacks red
  blood cells transferable by mosquitoes
• Bioterrorism-the use biological agents for
  terrorist purposes pathogenic organisms or
  agricultural pests

9
Seven Deadliest Infectious Diseases
Disease (type of agent)
Deaths per year
Pneumonia and flu (bacteria and viruses)
3.2 million
HIV/AIDS (virus)
3.0 million
Diarrheal diseases (bacteria and viruses)
Notice that the widely publicized Ebola, West
Nile, and SARS are not present on this list
1.9 million
Tuberculosis (bacteria)
1.7 million
Malaria (protozoa)
1 million
Hepatitis B (virus)
1 million
Measles (virus)
800,000
Fig. 14-3, p. 329
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Impact of AIDS on Age Structure of Botswana,
Africa
100 95-99 90-94 85-89 80-84 75-79 70-74 65-69 60-
64 55-59 50-54 45-49 40-44 35-39 30-34 25-29 20-24
15-19 10-14 5-9 0-4
With AIDS
Without AIDS
Male
Female
Age
120
40
20
0
60
80
10
20
100
120
80
60
40
Fig. 14-4, p. 331
Population (thousands)
11
Animation
HIV replication animation.
12
Distribution of Malaria
Fig. 14-5, p. 331
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Life Cycle of Malaria
Female mosquito bites infected human, ingesting
blood that contains Plasmodium gametocytes
Merozoites enter blood-stream and develop into
gametocytes causing malaria and making infected
person a new reservoir
Plasmodium develops in mosquito
Sporozoites penetrate liver and develop into
merozoites
Female mosquito injects Plasmodium sporozoites
into human host
Fig. 14-6, p. 332
14
Animation
Life cycle of plasmodium interaction
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Solutions for Infectious Diseases
Solutions
Infectious Diseases
Increase research on tropical diseases and
vaccines Reduce poverty Decrease
malnutrition Improve drinking water
quality Reduce unnecessary use of
antibiotics Educate people to take all of
an antibiotic prescription Reduce antibiotic use
to promote livestock growth Careful hand washing
by all medical personnel Immunize children
against major viral diseases Oral rehydration
for diarrhea victims Global campain to reduce
HIV/AIDS
Fig. 14-7, p. 333
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Characteristics of Agents that Could be Used as
Biological Weapons
Mortality (if untreated) 30 Varies 90100
60100 90100 3060
Existence of vaccine Yes No Yes Yes No
Yes (in testing)
Agent Smallpox (virus) Hemorrhagic fever
(viruses) Inhalation anthrax (bacterium) Botuli
sm (bacterium) Pneumonic plague (bacterium) Tu
laremia (bacterium)
Contagious Yes Yes No No Yes No
Symptoms Fever, aches, headache, red spots on
face and torso Vary but include fever, bleeding,
shock, and coma Fever, chest pain,
difficulty breathing, respiratory
failure Blurred vision, progressive paralysis,
death within 24 hours if not treated High fever,
chills, headache, coughing blood,
difficulty breathing, respiratory failure Fever,
sore throat, weak-ness, respiratory stress,
pneumonia
Treatment Vaccination within 4 days
after exposure, IV hydration Ebola has no cure,
antiviral riboflavin and some antibiotics may
help Early treatment with Cipro and other
antibiotics Equine antitoxin given
early. Intensive care, respirator Antibiotics
Antibiotics
Fig. 14-8, p. 334
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Chemical Hazards

• Toxic and hazardous chemicals-can harm or kill
  biological organisms
• Mutagens-chemicals or ionizing radiation that
  increase the frequency of mutations of DNA
  molecules
• Teratogens-chemicals that cause harm or birth
  defects to a fetus
• Carcinogens-chemicals or radiation that promote
  cancer
• Metastasis-spreading of cancer through the blood
  stream by the breaking off of one malignant
  eukaryotic cell from a tumor
• Effects on immune, nervous, and endocrine
  systems-
• Chemicals and radiation can weaken human immune
  system
• Neurotoxins can inhibit or damage nerve cells
• Chemicals can disrupt the regular release of
  hormones
• Neurotoxins-natural and synthetic chemicals that
  can harm the human nervous system
• Hormones-chemical messengers that turn on and off
  bodily systems

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Toxicology

• Toxicity- a measure of how harmful a substance is
  in causing injury or death
• Dose-the amount of substance ingested
• Relevance of genetic makeup-individuals
  sensitivity to a given toxin
• Multiple chemical sensitivity-a condition where a
  given individual is incredibly sensitive to a
  large number of toxins
• Solubility-water-soluble toxins can move
  throughout water and surround cells and their
  bodies
• Oil- or fat-soluble toxins-those dissolvable in
  fat or oil
• Persistence-resistance to be broken down
• Bioaccumulation-molecules stored at high levels
  in an orgnaism
• Biomagnification- the levels of some potential
  toxins in the environment as they pass through
  food webs and chains

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Toxicology

• Chemical interactions (antagonistic and
  synergistic)-an antagonistic interaction reduces
  harmful effects, while synergistic interactions
  multiply the harmful effects of a toxin.
• Acute toxic effects-an immediate or rapid harmful
  reaction to an exposure. Ex/ dizziness
• Chronic toxic effects- a permanent of
  long-lasting consequence to being exposed to a
  single or repeated dose of a harmful substance.
  Ex/ liver damage from alcohol.
• The dose is the poison-Any natural chemical can
  be harmful in large amounts. 100 cups of strong
  coffee would most likely kill someone from a
  caffeine overdose.
• Toxicity varies with individuals-based on genetic
  makeup
• How the human body disposes of chemical toxins-
• Enzymes break down toxins
• Cells can repair damage to DNA and protein
  molecules using enzymes
• Cells in some parts of your body can reproduce
  fast enough to replace damaged cells. Ex/
  intestine
• Effects of trace levels of toxic chemicals-it is
  based on chemical. We are detecting higher trace
  levels of toxins in our air, water and food.
  This could just be because we have better
  equipment.

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Estimating Toxicity

• Lethal dose (LD) Amount of toxin or poison
  which proves fatal to some organisms. Amount of
  LD depends on organisms size.
• LD50 The median Lethal dose at which 50 of the
  exposed organism will die. Units are in
  milligrams per Kilogram of body weight.
• Toxicity ratings of various compounds (Table
  14-1, p. 337)- Scientists use case studies and
  epidemiological studies to rate the toxicity of
  different chemicals.
• Using case reports Not so accurate because the
  dosage is not always known, but it can help
  provide clues about environmental hazards.
• Epidemiological studies (experimental and control
  groups) Compares the health of people exposed
  to a certain chemical with the health of a
  similar group not exposed to the chemical. Allows
  us to rate the exposure to a toxic chemical as
  strong, moderate, weak, or undetectable.
• Limits of epidemiological studies- 1. Too few
  people have been exposed to high enough levels of
  a certain chemical 2. Linking an observed effect
  with exposure to a certain chemical is hard
  because people are exposed to many different ones
  in their lives. 3. We cant use epidemiological
  studies to evaluate hazards from new technologies
  or chemicals that people have not yet been
  exposed.
• Laboratory studies Exposing a population of
  live laboratory animals (especially mice and
  rats) to known amounts of a chemical is the most
  widely used method for determining its toxicity.
• Controversies with testing with animals Animal
  tests take 2-5 years, cost 200,000 - 2,000,000
  per substance, and can harm or kill the test
  subjects. More humane tests include computer
  simulations based on tissue samples or egg
  membranes.
• Non-threshold and threshold dose-response models
  non-threshold models show the harmful effects
  with increasing dosages assuming that ANY dose is
  harmful, while threshold models assume that a
  level of dose must be reached before harmful
  effects will begin.

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Dose-Response Curve
100
75
50
Percentage of population killed by a given dose
25
LD50
0
4
8
12
16
14
10
6
2
Dose (hypothetical units)
Fig. 14-9, p. 337
22
Toxicity Ratings
Table 14-1, p. 337
23
Threshold and Nonthreshold Dose-Response Curves
Nonlinear dose-response
Linear dose-response
Effect
Effect
Threshold level
No threshold
Threshold
Fig. 14-10, p. 338
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Protection Against Harmful Chemicals

• Protecting children from toxic chemicals-
  Children are generally more vulnerable to toxic
  chemicals than adults. They breathe more air,
  drink more water and eat more food per unit of
  body weight. Also their immune systems are weaker
  than that of adults (it is less developed)
• Why do we know so little about the harmful
  effects of chemicals? Under our laws most
  chemicals are considered innocent until proven
  guilty. In addition to the difficulty of
  establishing guilt and the cost of doing so.
• Lack of regulations The federal and state
  governments only regulate 0.5 of all the
  commercially used chemicals in the U.S. There
  arent enough funds, personnel, and facilities.
• Pollution prevention-Chemicals should not be
  released into the environment that have a chance
  of considerable harm. Looking for substitutes and
  recycling the chemicals instead of releasing them
  are examples of pollution prevention.
• Precautionary principle-When there is plausible
  but incomplete scientific evidence of significant
  harm to humans or the environment from a proposed
  or existing chemical or technology, decision
  makers should act to prevent harm to humans and
  the environment.
• Innocent until proven guilty approach-Where the
  chemical is considered to not be harmful in any
  way until it has been tested and thoroughly
  diagnosed to make sure
• Persistent organic pollutants (POPs) (dirty
  dozen)- The 12 chemicals that include DDT and
  eight other persistent pesticides, PCBs, and
  dioxins and furans. PCB is known to cause skin
  diseases and cause birth defects.

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Risk Analysis

• Risk analysis (risk assessment)-identifying
  hazards and evaluating their risks, ranking those
  risks, determining options, and making the
  correct decision as to how to deal with it.
• Comparative risk analysis-compares high, medium,
  and low health and ecology risks.
• Risk management-reducing or eliminating risks.
• Risk communication-informing the decision-makers
  and the public about the risks and options
• Poverty the greatest risk- it results in
  malnutrition, increased susceptibility to
  normally nonfatal infectious diseases, and often
  fatal infectious diseases result from lack of
  access to safe water supplies.
• Risks from lifestyle-see next page

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Number of Deaths Per Year Globally
Cause of Death
Annual Deaths
Poverty/malnutrition/ disease cycle
11 million (75)
Tobacco
5 million (34)
Pneumonia/flu
3.2 million (22)
Air pollution
3 million (21)
HIV/AIDS
3 million (21)
Malaria
3 million (21)
Diarrhea
1.9 million (13)
1.7 million (12)
Tuberculosis
Auto accidents
1.2 million (8)
1.1 million (8)
Work related injury
Hepatitis B
1 million (7)
Measles
800,000 (5)
Fig. 14-12, p. 341
27
Comparative Risk Analysis
Comparative Risk Analysis
Most Serious Ecological And Health Problems

• High-Risk Health Problems
• Indoor air pollution
• Outdoor air pollution
• Worker exposure to industrial or farm chemicals
• Pollutants in drinking water
• Pesticide residues on food
• Toxic chemicals in consumer products
• High-Risk Ecological Problems
• Global climate change
• Stratospheric ozone depletion
• Wildlife habitat alteration and destruction
• Species extinction and loss of biodiversity

• Medium-Risk Ecological Problems
• Add deposition
• Pesticides
• Airborne toxic chemicals
• Toxic chemicals, nutrients, and sediment in
  surface waters

• Low-Risk Ecological Problems
• Oil spills
• Groundwater pollution
• Radioactive isotopes
• Acid runoff to surface waters
• Thermal pollution

Fig. 14-11, p. 340
28
Estimating Risks from Technologies

• System reliability () Technology reliability x
  Human reliability
• Difficulties in estimating reliability - Human
  reliability is difficult to measure due to the
  unpredictability of human behavior, chance, and
  sabotage.
• Possible to achieve high reliability Through
  careful design, quality control, maintenance, and
  monitoring, a highly complex system can be highly
  reliable technologically speaking, but is often
  brought down overall by human reliability.
• To err is human humans are more subject to
  accidents than some machines because of the way
  that machines do the same task in the same way,
  while humans do not follow exactly the same
  procedure each time, which can leave room for
  error.
• Automatic control systems Are often more
  reliable than humans but can never replace human
  judgment in case of a lightning bolt knocking out
  the systems or other natural occurrences. The
  more volatile elements are often moved in control
  of these systems to decrease the chance for
  error, but this does not make them infallible.

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Comparison of Risks
HAZARD
SHORTENS AVERAGE LIFE SPAN IN THE UNITED STATES BY
7-10 years
Poverty
Born male
7.5 years
Smoking
6-10 years
6 years
Overweight (35)
5 years
Unmarried
2 years
Overweight (15)
1 year
Spouse smoking
7 months
Driving
5 months
Air pollution
5 months
Alcohol
4 months
Drug abuse
4 months
Flu
3 months
AIDS
2 months
Air Pollution
1 month
Drowning
1 month
Pesticides
1 month
Fire
8 days
Natural radiation
5 days
Medical X rays
5 days
Oral contraceptives
4 days
Toxic waste
1 day
Flying
1 day
Hurricanes, tornadoes
10 hours
Living lifetime near nuclear plant
Fig. 14-13, p. 342
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Perceiving Risks

• Distorted perceptions of risks- People would
  think that a technology or product is either more
  or less risky than experts judge it to be.
• Degree of control- Most people are afraid things
  that they do not control.
• Fear of the unknown and distrust of the new-Most
  people have a greater fear of a new unknown
  product or technology than they do of an older,
  more familiar one.
• Whether we voluntarily take the risk-If you enjoy
  using a product or technology that might be risky
  you will likely continue to use it if you enjoy
  it.
• Whether the risk is catastrophic-People usually
  have a greater fear of a well publicized death
  from a single catastrophic accident than the same
  or an even larger death toll spread out over a
  longer time. (E.g. Severe nuclear power plant
  accidents, plane crashes, etc.)
• Unfair distribution of risks-People dont want to
  have pollutants left near their neighborhoods and
  in landfills around the area. They feel that they
  may get cancer from being near those facilities
  yet chances of cancer in a lifetime of being near
  a facility are 1 in 100,000
• Educating ourselves on risk-Make sure you
  carefully analyze news reports because the media
  can exaggerate the risks of a product. People
  should be asking, How risky is it compared to
  other risks? not the question Is it safe.
• Reducing risks in our own lives-Dont do things
  that will harm your body in the future (Smoking,
  alcohol, UV rays, safe sex, etc.) You have
  control over these and it is not difficult to
  manage these risks.