Transcript Document

Risk, Toxicology, and Human Health
Ch 17
Dr. Richard Clements
Chattanooga State Technical Community College
Key Concepts
 Types of hazards people face
 Methods of toxicology
 Types and measurement of chemical hazards
 Types and effects of biological hazards
 Risk estimation, management, and reduction
Risk and Probability
 Risk - the possibility of suffering harm from
exposure to a hazard that can cause injury,
disease, economic loss, or environmental damage.
 probability: a mathematical statement about
how likely it is that some event or effect will occur.
Risk assessment involves using data, hypotheses, and
models to estimate:
a. What is the hazard?
b. Probability that harm will occur
c. How much damage is likely to occur
Risk and Probability
 Risk management - making decisions by
a. Comparing with other risks
b. Assessing how risk can be
reduced if needed
c. Calculating financial commitment
necessary
Hazards
Cultural hazards - such as unsafe working
conditions, diet, drugs, drinking, poverty
Chemical hazards - from harmful chemicals
(such as, in the air, water, soil).
Physical hazards - (ex: ionizing radiation,
fire, hurricanes).
Biological hazards - from pathogens (disease
causing organisms such as bacteria, viruses & parasites),
allergens (such as pollen, mold), and animals (such as bees,
poisonous snakes).
Toxicology
Toxicity - measure of how harmful
a substance is.
Dosage - The amount of a
potentially harmful substance that a
person has ingested, inhaled, or absorbed
through the skin
Number of individuals affected
© 2004 Brooks/Cole – Thomson Learning
Very
sensitive
0
Majority
of population
20
40
Dose (hypothetical units)
Very
insensitive
60
80
Response
The resulting type and amount of damage to
health
Depends on:
a. size of the dose over a period of time
b. how often exposure occurs
c. who is exposed (ex: child, adult)
d. How well liver, lungs and kidneys work to
detoxify the substance
e. Genetic makeup that determines an
individuals sensitivity
Toxicology
Persistence of substance – resistance to breakdown
determines how long it will persist in the environment or body.
Ex: CFC’s and chlorinated hydrocarbons have a long-lasting
affect on people and wildlife.
Bioaccumulation - an increase in the concentration
of a chemical in specific organs or tissues at a level higher than
would normally be expected.
Biomagnification - The levels of some toxins stored
in body fat can also be magnified as they pass through food
chains and webs. Ex: DDT – pesticide, PCB’s – oily chemicals
used in electrical transformers, some radioactive isotopes
DDT in fish-eating
birds (ospreys)
25 ppm
DDT in large
fish (needle fish)
2 ppm
DDT in small
fish (minnows)
0.5 ppm
DDT in
zooplankton
0.04 ppm
DDT in water
0.000003 ppm,
Or 3 ppt
Toxicology
Synergism -Chemical interactions can decrease or
multiply harmful effects:
Antagonistic interactions – reduce harmful response
Ex: vitamins A & E reduce response of some
carcinogens.
Synergistic interactions – increase harmful response
Ex: asbestos exposure and cigarette smoking together
increase chances of getting lung cancer above each
substance alone.
Acute effect - immediate harmful reaction
Chronic effect - permanent or long lasting
effect.
Poisons
Poison - chemical that has an LD50 of 50
milligrams or less per kilogram of body
weight.
LD50 - median lethal dose, or amount of a
chemical received in one dose that kills exactly
50% of the animals in a test population within a
14-day period.
© 2004 Brooks/Cole – Thomson Learning
Percentage of population killed by a given dose
100
75
50
25
LD
0
2
4
6
8
50
10
12
Dose (hypothetical units)
14
16
How much is too much?
Threshold level – below this amount, harmful effects are
insignificant. Why?
1. Human body has ways of breaking down (usually by
liver enzymes), diluting or excreting small amts. of most
toxins to keep them from reaching harmful levels.
2. Individual cells have enzymes that can repair damage
to DNA and proteins.
3.Cells in some parts of the body (ex: skin, intestines)
reproduce fast enough to replace damaged cells. But
exposure to carcinogens accelerates cell growth and
creates tumors.
4.Detection methods have become increasingly more
sensitive – in 1980 chemists could detect concentrations
in ppm (parts per million), in 1990 in ppb (ppbillion), and
today ppt (pptrillion) or sometimes ppq (ppquadrillion).
Dose-Response Curves
 Nonthreshold - any dose of a toxic chemical
or ionizing radiation has a certain risk of
causing harm.
 Threshold there is a threshold dose below
which no detectable harmful effects occur,
presumably because the body can repair the
damage caused by low doses of some
substances.
© 2004 Brooks/Cole – Thomson Learning
Nonlinear
dose-response
Linear
dose-response
Linear
dose-response
Effect
Effect
Nonlinear
dose-response
Threshold
level
Dose
No threshold
Dose
Threshold
Chemical Hazards
Types of Hazardous chemicals
Mutagens - are agents, such as chemicals
and radiation, that cause mutations, or changes
in the DNA molecules found in the cells.
Mutations to gametes can cause diseases such
as bipolar disorder, cystic fibrosis, hemophilia,
sickle-cell anemia, susceptibility to some types
of cancers in offspring. Most mutations are
actually harmless and some play a vital role in
microevolution.
Chemical Hazards
Types of Hazardous chemicals
Teratogens - are chemicals, radiation, or viruses that
cause birth defects while the human embryo is growing
and developing during pregnancy, especially during the
first 3 months.
Carcinogens - are chemicals, radiation, or viruses that
cause or promote the growth of malignant tumor, in
which certain cells multiply uncontrollably.
Chemical Hazards
 Neurotoxins
Ex:
1. chlorinated hydrocarbons (DDT, PCBs, dioxins)
2. organophosphate pesticides
3. formaldehyde, compounds of arsenic, mercury,
lead, and cadmium
4. some widely used industrial solvents such as
trichloroethylene (TCE), toluene, and xylene.
Case Study: PCBs Are Everywhere—
• Class of chlorine-containing compounds
(Polychlorinated Biphenyl )
– can enter the air as vapor
– Were widely used as lubricants, hydraulic fluids,
electrical insulators in transformers, in paints,
pesticides, fire retardants in fabrics,
preservatives, adhesives.
– Carcinogen, also affects reproductive, nervous,
endocrine, immune system.
– Banned in 1979 in the U.S.
– Highly persistent, Fat soluble – Biomagnification
• Banned, but found everywhere
Science Focus: Mercury’s Toxic
Effects (2)
How are humans exposed?
– Inhalation: vaporized Hg or particulates of
inorganic salts
– Eating fish with high levels of methylmercury
Effects of Hg on humans – Neurotoxin that
causes brain damage, esp in developing
fetuses
Case Study – Minimata Bay, Japan
WINDS
Hg and SO2
Photochemical
oxidation
WINDS
Inorganic
mercury
and acids
(Hg2+)
PRECIPITATION
Hg2+ and acids
Inorganic mercury
and acids
(Hg2+)
Deposition
Runoff of Hg2+ and acids
Vaporization
Deposition
Incinerator
Coalburning
plant
Elemental
mercury
vapor
(Hg)
Deposition
Human sources
PRECIPITATION
Hg2+ and acids
Large fish
Small fish
BIOMAGNIFICATION
IN FOOD CHAIN
Zooplankton
Phytoplankton
Bacteria
Elemental Oxidation Inorganic and acids Organic
mercury
mercury
mercury
+
2+
Bacteria
(CH
liquid (Hg)
(Hg )
3Hg )
Settles
Settles
Settles
out
out
out
SEDIMENT
Fig. 17-A, p. 450
SOLUTIONS
Mercury Pollution
Prevention
Phase out waste incineration
Remove mercury from
coal before it is burned
Switch from coal to natural
gas and renewable energy
resources such as wind,
solar cells, and hydrogen
Convert coal to liquid or
gaseous fuel
Phase out use of mercury in
batteries, TVs, compact
fluorescent lightbulbs, and all
other products unless they are
recycled
Control
Sharply reduce mercury
emissions from coal-burning
plants and incinerators
Tax each unit of mercury
emitted by coal-burning
plants and incinerators
Require labels on all
products containing mercury
Collect and recycle mercurycontaining electric switches,
relays, and dry-cell batteries
Fig. 17-B, p. 451
Bisphenol A
• Used in plastic food containers (#7)
• Many studies find no effects
• Precautionary principle
Chemical Hazards
Hormonally active agents (HAA’s)
Low levels of synthetic chemical agents that can mimic and disrupt
effects of natural hormones. Ex: PCBs, DDT
Hormone mimics - are estrogen-like chemicals that disrupt the
endocrine system by being able to attach to estrogen
receptor molecules.
Hormone blockers - disrupt the endocrine system by preventing
hormones (such as androgens) from attaching to their receptors.
thyroid disruptors and cause growth,
weight gain, and behavioral disorders.
Figure 11-7
Page 234
Hormone
Estrogen-like chemical
Antiandrogen chemical
Receptor
Cell
Normal Hormone Process
Hormone Mimic
Hormone Blocker
What should we do?
Precautionary principle
1. Emphasizes pollution prevention!
2. When we are uncertain about potentially
serious harm from something, decision makers
should act to prevent harm to humans and the
environment. (“better safe than sorry”
3. New chemicals and technologies would be
assumed guilty until proven innocent those
proposing to introduce a new chemical or
technology would bear the burden of establishing
it’s safety
Biological Hazards: Diseases
Nontransmissible disease
Transmissible disease
Pathogens
Vectors
Antibiotic resistance
Malaria
AIDS
See Case Study p. 241
Figure 11-12
Page 243
Malaria-free areas
Malaria largely eliminated
Malaria transmission areas
Risk Analysis
Risk analysis
Comparative risk
analysis
Cost-benefit
analysis
Risk management
Risk perception
Fig. 11-17
p. 247