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Risk, Toxicology, & Human Health
Chapter 19
Winter Break Homework Assignment
Due 2.25.13
Define risk, risk assessment, and risk management. What is the different
between probability and possibility? Give an example that shows the difference
between the two.
Risk is the possibility being harmed by a hazard.
R. assessment is the process of estimating how much harm a hazard can
cause to health.
R. management is a process of determining how (or whether) to reduce a
risk to a lover level.
Possibility means something can happen, while probability estimates HOW
likely is to happen.
List four general types of hazards and give two examples of each.
Cultural hazards (work zones, smoking, bad habits, POVERTY)
Physical hazards (environmental conditions that affect all: UV rad., volcanoes
Chemical hazards (air, water, food pollutants)
Biological hazards (pathogens, allergens)
Define toxicity and describe what factors affect toxicity.
Toxicity measures how harmful a substance is in causing harm to a l.t. It’s affected by
dose size, frequency of exposure, who’s dosed, detox systems in body, solubility of
toxin, too.
Define and explain the differences between bioaccumulation and biomagnification.
Bioaccumulation is absorption and storage of molecules at concentrations higher than
normal levels. Biomagnification means some toxins are magnified in concentration as
they travel from low trophic levels to higher trophic levels.
What five major factors can affect the harm caused by a substance? Explain each.
Solubility: water or oil/fat-: water soluble travel through ecosystems, fat soluble
toxins tend to pass through cell membranes (phospholipid bilayer)
Persistance: tendency not to degrade over time (DDT
Chemicals react with each other!!!
Antagonistic reactions decrease harmful effects but
Synergistic reactions multiply/amplify harm
(acute vs. chronic)
Explain how synergism and antagonism are different.
Explain the relationship between dose and response. Distinguish between acute and chronic
exposures and acute and chronic effects.
Dose is the quantity of a toxin to which one is exposed. The dose makes the poison, but
differently for different individuals. Response is the type and extent of damage that
results from the dosage.
Acute exposure is a quantity over a single period of ingestion, chronic exposure is
longer term. Acute effect is rapid harm soon following exposure (e.g., dizziness after a
few drinks of alcohol), chronic effect is long term, permanent or long-lasting
consequesnce (sirrhosis of liver after a life of drinking heavily)
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Describe a dose-response curve. Evaluate the usefulness and limits of the following in
determining toxicity of substances:
a) case studies
b) laboratory experiments
c) epidemiology studies
A dose-response curve relates the dosage of a chemical to the percentage of a population
that is killed (affected however) by the chemical.
Case studies are useful because they give great details concerning individual cases, but
specific doses are often not well documented (not controlled esperiments)
Laboratory experiments are very useful because the conditions of assessment are very
controlled and huge amounts of data can be collcted. Also, the data are compared to
control groups. However, often those data are collected using non-human test subjects
and the effects of doses on non-humans may not correlate directly with human
Epidemiological Studies compare the health of people who have been exposed (in situ)
to chemical with the health of a control group who they know have not been exposed.
Used to determine (statistically) if exposure casues the problem. Limitations include:
small sample sizes; linking effect to exposure is DIFFICULt when exposure to other
chemiclas isn’t known
Explain the differences between a linear dose-response model and a threshold dose-response
model. Draw a picture of each and describe the difficulty in deciding which model applies
best when low doses are involved.
The difference between linear dose-response and threshold dose-response models is that
a threshold dose requires a minimum dose beyond which response will be measurable.
Non threshold doses mean that any dose will cause a response
Define epidemiology and explain its strengths and weaknesses in predicting the toxicity of
various chemicals, bacteria, and viruses.
Study of the patterns, causes and effects on health and disease in a given population.
(see #8)
Explain the differences between the following: mutagens, carcinogens, teratogens.
Three major classes of toxic agents:
1. Mutagens: substances or radiation cause or increase frequency of
mutations in DNA/RNA sequences
2. Teratogens: substances or radiation that cause harm or birth defects to
fetus, embryo or gametes
3. Carcinogens: substances or radiation that cause or promote cancer-the
uncontrolled growth of cells
Explain how chemical harm each of the following systems and list examples of each type of
a) Immune system: toxins can weaken immunity leaving body vulnerable to attacks by
virus, bacteria, allergens, etc.
b) Nervous system neurotoxins affect nervous system; many interfere with
neurotransmitters between synapses of neurons: cause behavioral changes, paralysis
c) Endocrine system: many synthetic chemiclas mimic and disrupt effects of hormones.
Some act as hormone disrupters
Explain how each of the following chemicals works:
a) hormone disrupter: prevent hormones from acting on cells appropriately: they deactivate
receptor sites and prevent-among other things-natural feedback mechanisms.
b) hormone mimic similar to disruptors. Leave it that
c) hormone blocker prevent natural hormones from attaching to receptors
Distinguish between transmissible and non-transmissible diseases. List the six deadliest
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infectious diseases. Summarize the state of the battle against bacterial infections. Describe
how transmission of viral diseases can result in pandemics.
N-T non-living vectors, not spread/contagious to others. Often have multiple
causes. Eg., cardiovascular diseases, diabetes, emphysema, etc.
Transmissible: caused by living organisms (virus (sic), bact., other infectious
agents (pathogens) spread by air water food body fluids. Some have insect vectors, too.
Battle against bacterial infections is tough: bacteria reproduce so rapidly, they evolve
resistance to antibiotic drugs rapidly. Overuse of pesticides and antibiotics in
agriculture contributes to this.
1. Pneumonia/Flu
3. Diarrheal diseases
4. TB
5. Malaria
6. HEP B
Viral disease transmission: can become pandemic because many people exposed to
viruses either show no symptoms, or the diseases caused have long incubation periods
Compare and contrast an epidemiologic transition to a demographic transition. Summarize
how developing countries and developed countries can best improve their health.
Epidemiological transition: as industrialization progresses, deaths from
infectious diseases decreases and deaths from chronic diseases of adulthood increase (cv diseases, stroke, cancers, respiratory, etc.)
What are the six possible common agents that might be used as biological weapons? How
would we prepare our population to protect ourselves from each?
Define risk analysis. Compare technology reliability to human reliability.
Risk analysis: identifying hazards and evaluating associated risks
List seven questions risk managers ask. List seven cases in which the public generally
perceives that a technology or product has a greater risk than the risk estimated by experts.
Make a list of the risks you take on a daily basis (you should have about 20-30). Classify
them into the following categories: chosen risks; risks over which you have no control.
In the news (NYT: “Mice fall short as test subjects…”) this week, there is an article that
suggests that the standard animals that are used in Dose Response-type assays occasionally
produce results that aren’t as useful as has long been believed. Please provide a brief
summary of this article.
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