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Chapter 10
Risk, Toxicology &
Human Health
I. Risk
A. The probability of hazard (injury, disease, economic or
environmental damage
B. Risk Assessment
1. What is the hazard?
2. How likely is the event?
3. How much damage is it likely to cause?
C. Risk Management
1. How does it compare to other risks?
2. How much should it be reduced?
3. How will it be reduced?
3. How much will reduction cost?
* Economic, health, and political implications
Annual Deaths in the United States
443,000
Smoking
Auto
Accidental
75,000
Alcohol
Pneumonia
& Influenza
Suicide
AIDS
Hard Drugs
Homicide
55,000
35,000
16,000
15,000
14,000
118,000
D. Types of Hazards
1. Chemical Hazards
2. Physical Hazards
3. Biological Hazards
4. Cultural Hazards
Tox21
II. Toxicology
A. Toxicity
1. The measure of how harmful a substance is
2. Depends on:
- Size of dose ***Threshold Level***
- Frequency of dose
- Size/age of organism exposed
- Body’s detox abilities (liver, lungs, kidneys)
- Genetics
- Toxin’s persistence in environment
- Toxin’s solubility (in water, oil, fat)
* Dose = amount of toxin ingested, inhaled, absorbed,
injected, etc.
Number of Individuals Responding
0
10
20
30
Dose (hypothetical units)
40
3. Important Bio/Chemical Interactions
a) Bioaccumulation
b) Biomagnification
c) Antagonistic Interactions:
Interaction with a certain chemical will reduce the harmful
effects of a toxin
d) Synergistic Interactions:
Interaction with a certain chemical will multiply the
harmful effects of a toxin
Exposure to Asbestos
Chance of
Lung Cancer
Non-Smoker
Smoker
20X 400X
4. Toxic Response
a) Acute
b) Chronic Effect
*Epidemiology: study of illness in human populations
5. Dose-Response Curves
Show effects of various dosages of toxin on a test group
Threshold
Effect
Effect
No Threshold
Threshold
Dose
Dose
a) LD50 (Median Lethal Dose)
The amount of a toxin that will kill 50% of a test population
*Usually within 2 weeks
Percent Population Killed
100
75
50
25
0
2
4
6
8
10
12
Dose (hypothetical units)
14
b) LC50 (Median Lethal Concentration)
The concentration of a toxin in water or air that will kill 50% of
a test population
*Usually within 2 weeks
- You don’t know how much an individual takes in (dose),
just the concentration in the environment
Why are
animal tests
controversial?
B. Chemical Hazards
1. Acute
a) Flammable/explosive
b) Caustic/Corrosive
c) Asphyxiants
d) Allergens
2. Chronic
a) Mutagens
2. Chronic
a) Mutagens
b) Teratogens
Mercury
Minamata Disease
Thalidomide
c) Carcinogens
1) Promote about 80% of all cancers
30-40%
20-30%
5-15%
1-10%
cigarette smoke
diet
environmental pollutants
occupational exposure
* The other 20% caused by genetic factors & viruses
d) Neurotoxins
e) Hormonally Active Agents (HAAs)
1) Hormone Disrupters
• Hormone Mimics
• Hormone Blockers
3. Scary Synthetic Chemical Facts
a) Approximately 1,000 new chemicals are introduced to
consumers each year
b) 99.5% of these chemicals are not government regulated
c) Only 10% of the near 100,000 commercial chemicals in
use have been screened for toxicity
But…. now we have Tox21!!!
Scheduled to screen
10,000 chemicals over the
next 2 years
C. Biological Hazards
1. Non-transmissible Diseases (Non-communicable)
Not caused by living organisms and not spread from
person to person
• cardiovascular diseases
• cancers
• diabetes
• asthma
• etc.
2. Transmissible Diseases (Communicable)
Caused by pathogens - bacteria, protozoa, fungi,
viruses, parasites
Bacteria and viruses can be highly contagious and
reproduce rapidly and in large numbers
*Leads to fast microevolution
a. Bacterial Infections & Resistance
The overuse/misuse of antibiotics has increased the
number of genetically resistant bacteria
*Very difficult to treat & kill
Examples:
MRSA (Methicillin-Resistant Staphylococcus aureus)
Tuberculosis (TB)
TUBERCULOSIS: “The Silent Global Epidemic”
TUBERCULOSIS: “The Silent Global Epidemic”
• Approximately 14 million cases
• Bacteria has become drug resistant
b. Viral Infections
• Viruses are non-cellular pathogens
• Need a host cell to replicate. How?
Antibiotics have no effect on them!!!
Examples:
Influenza
Ebola
Rabies
HIV (Human Immunodeficiency Virus)
HIV & AIDS (Acquired Immunodeficiency Syndrome)
*HIV is not deadly
It kills white cells, weakening the immune system
Leads to AIDS
*Transmitted via:
Sex, intravenous needles, exposure to blood, mother child
*Worldwide Spread:
7-10 years for symptoms to show
About 5.5 million newly infected each year
~ 15,000/day
c. Malaria: A protozoal disease
• 270-500 million new cases each year
c. Malaria: A protozoal disease
• 270-500 million new cases each year
• Kills over 1 million people per year
• Vector: Anopheles mosquito
• Pathogen: Plasmodium sporozoites (4 types)
• Control Problems:
Mosquitoes become resistant to insecticides
Plasmodium become resistant to medications
• Locals develop natural immunity
Ex. Sickle Cell Anemia
Vector
Anopheles mosquitoes
D. Risk Analysis
1. Cost-Benefit Analysis
When using a new chemical, technology, etc…
Do the risks/costs outweigh the benefits?
…Is it worth it?
2. Comparative Risk Analysis
Compares (sometimes ranks) the relative risk of major
environmental & health hazards
3. Perceived Risk
The majority of people are pretty bad at assessing the
relative risks of hazards around us…
*Better education and communication needed