Transcript Chapter 17

Chapter 17
Human Health and Environmental
Risks
Warm-Up
1. What are the leading causes of death worldwide?
2. How is the economic development of a country
related to disease?
3. Rank the following in order of highest probability of
death to lowest probability:
A.
B.
C.
D.
E.
Airplane accident (1 in 5,051)
Drowning (1 in 1,008)
Motor vehicle accident (1 in 84)
Heart disease (1 in 5)
Firearm assault (1 in 314)
What is Risk?
• Risk: possibility of
suffering harm from a
hazard
Human Health Risks
• Physical – harm caused by environmental factors
– Natural disasters
– Sunburn
• Biological – harm caused by diseases
– Malaria
– Influenza
• Chemical – harm caused by chemicals
– Arsenic
– Pesticides
Leading Causes of Death Worldwide
Biological Risks
• Disease: any impaired
function of the body with a
characteristic set of symptoms
Biological Risks
• Infectious diseases: those
caused by infectious
agents, known as
pathogens
– Ex: pneumonia and
venereal diseases
Pathogens
• Bacteria:
– Cholera
– Tuberculosis
– Syphilis
• Virus:
– HIV/AIDS
– Hepatitis
– Ebola
• Protozoa:
– Malaria
What causes disease?
• Infectious agents (pathogens) that spread by:
– Air
– Water
– Food
– Body fluids
– Vectors (nonhuman carriers, like mosquitoes)
Biological Risks
• Chronic disease: slowly impairs the
functioning of a person’s body
– Ex: heart disease, cancer, diabetes
– 70% of all deaths in the U.S.
• Acute disease: rapidly impairs the functioning
of a person’s body
– Ex: Ebola hemorrhagic fever
Leading Health Risks in the World
Historical Diseases
• Plague
• Malaria
• Tuberculosis
Emergent Diseases
•
•
•
•
•
HIV/AIDS
Ebola
Mad Cow Disease
Bird Flu
West Nile Virus
Emergent Diseases
Pathways of Transmitting Pathogens
Chemical Risks
• Neurotoxins: chemicals that disrupt the
nervous system
• Carcinogens: chemicals that cause cancer
• Teratogens: chemicals that interfere with the
normal development of embryos and fetuses
• Allergens: chemicals that cause allergic
reactions
• Endocrine disruptors: chemicals that interfere
with the normal functioning of hormones
Toxicology Studies
• Retrospective studies
– “Looking back”
– Monitoring people who have already been
exposed to a chemical to determine the effects
• Prospective studies
– “Looking forward”
– Monitoring people who might become exposed to
a chemical to determine the effects
Toxicology Studies
• Epidemiology: field of
science that seeks to
understand the causes of
illness and disease
• Retrospective and
prospective studies allow
researchers to determine
the effects of chemicals
on individuals
Toxicology
• Dose: the amount of a substance that a
person has in their body
– Can be:
• Ingested
• Inhaled
• Injected
• Absorbed
• “The dose makes the poison”
Dose-Response Studies
• Exposing organisms to different doses of a
chemical and then observing their response
allows scientists to determine how chemicals
affect living things
• Response: the effect that a substance has on
an organism (ex: mortality, change in behavior,
etc.)
• LD50: the lethal dose that kills 50% of the
individuals within a test population
Dose-Response Studies
Dose (hypothetical units)
1
2
3
4
5
6
7
8
9
10
Percent Mortality
0%
0%
4%
10%
40%
60%
90%
96%
100%
100%
LD50
LD50 = 5.3
Do The Math
• If the LD50 of a pesticide is 20 mg/kg for a
mouse, what amount would be considered safe
to ingest for a human?
• (Calculate the “safe” amount by taking the LD50
and dividing it by 1,000)
20 mg/kg ÷ 1000 = 0.02 mg/kg
• Calculate the maximum amount that a 80 kg
man could ingest and still be considered “safe”
80 kg × 0.02 mg/kg = 1.6 mg
Poisons
• Poisons: materials that kill at a
very small dose (50 milligrams
or less per kilogram of weight)
Toxicity
Rating
super toxic
extremely
toxic
very toxic
toxic
moderately
toxic
slightly toxic
essentially
nontoxic
Average Lethal
Dose
Examples
LD50
< 0.01
less than 1 drop nerve gases, botulism,
mushroom toxins, dioxin
<5
less than 7 drops potassium cyanide, heroin,
atropine, parathion,
nicotine
5–50
7 drop to 1
mercury salts, morphine,
teaspoon
codeine
50–500
1 teaspoon to 1 lead salts, DDT, sodium
ounce
hydroxide, fluoride, sulfuric
acid, caffeine, carbon
tetrachloride
500–5,000
1 ounce to 1 pint methyl alcohol, ether,
pehobarbital,
amphetamines, kerosine,
aspirin
5,000–15,000 1 pint to 1 quart ethyl alcohol, lysol, soaps
> 15,000
more than 1 quart water, glycerin, table sugar
Threshold
Dose-Response Studies
• ED50: effective dose that causes 50% of the
individuals to display the harmful, but
nonlethal, effect
• These effects that change the behavior of the
individuals or cause harm are called sublethal
effects
• The LD50 and ED50 values for mice are often
divided by 1,000 to determine the safe value
for humans
Interactions
• Synergistic interactions: when two (or more)
risk factors have a greater effect together than
each by themselves
– Ex: being exposed to asbestos and smoking gives
you a 400 times greater chance of developing lung
cancer than if you experienced only one of those
risks
+
=
Routes of Exposure
Toxicology
• Solubility: what can the chemical dissolve in?
– Water-soluble toxins
– Oil/Fat-soluble toxins
• Which do you think is generally “better” for
the health of an organism?
– Water is “better” since it can be diluted
– Fats aren’t good since chemicals can gather
in body fat of animals
Do The Math
If the element Strogenium has an LD50 of
40 mg/kg, how big of a dose is necessary
to kill a 30 kg goat?
Toxicology
• Bioaccumulation: an increased
concentration of a chemical
within an individual organism
over time
– The chemical is usually stored in
body fat
• Biomagnification: the increase
in a chemical concentration in
animal tissues as the chemical
moves up the food chain
Persistence
• Persistence: how long a chemical remains in
the environment
Risk Analysis
Qualitative vs. Quantitative
• Qualitative risk assessment: judging
the relative risk of various decisions (ex:
low, medium, or high)
• Judgments based on perception, not
on actual data
• Quantitative risk assessment:
determining the probability of an event
occurring using data (ex: 83% chance)
Probabilities of Death in U.S.
Risk Analysis
Probability of being exposed to a hazard
Risk =
x
Probability of being harmed if exposed
Risk Analysis
• What is riskier: flying on a plane for 1,000
miles per year or eating 40 tablespoons of
peanut butter per year?
– The probability of a plane crash is low, but the
probability of dying if the plane crashes is high
– The probability of eating peanut butter is high, but
the probability of developing cancer from the
peanut butter is low
– Both behaviors produce a risk of 1 in 1 million
Chemical Regulation
Chemical Regulation
• Trade-off:
– Greater safety with slower introduction of
beneficial chemicals
vs.
– Greater potential risk with a greater rate of
discovery of beneficial chemicals
Concentration Practice Problems
1. How much is 6 ppm in ppb?
6
x
1,000,000
1,000
6,000
=
1,000
= 6,000 ppb
1,000,000,000
2. What concentration is 4,000 ppt in ppm?
4,000
1,000,000,000,000
÷
1,000,000
1,000,000
=
0.004
1,000,000
= 0.004 ppm