Risk, Toxicology, and Human Health
G. Tyler Miller’s
Living in the Environment
14th Edition
Chapter 19
Key Concepts to Chapter 19
 Types of hazards people face
 Defining and measuring toxicology
 Types and measurement of chemical hazards
 Types and effects of biological hazards
 Risk estimation, management, and reduction
Annual death rates in the U.S. in 2003.
Sections 1 and 2 Key Concepts
• What is risk? What are the major types of
hazards?
• What determines if a chemical is hazardous?
• What are the basic principles of toxicology?
• Can a little bit of pollution actually be good for
you?
• How good are estimates of toxicity?
Risk, Probability and Hazards
Risk: is the possibility of
suffering a harm from a
hazard that can cause injury,
disease, death, economic loss,
or environmental damage.
Risk Assessment: the scientific
process of estimating harm a
particular hazard may cause.
Risk Management: deciding
whether or not to reduce a
risk and at what cost.
What is risk?
Risk is expressed in
probabilities.
Example: “The lifetime
risk of developing lung
cancer is 1 in 250 from
smoking a pack a day”
Plane crash: 1 in 10 million
Lightning: 1 in 1.4 million
House Fire: 1 in 200
Risk and Probability
Risk
Risk
assessment
Risk
management
Probability
Fig. 19-2 p. 410
Hazards: Types of Risk
 Cultural hazards: working conditions, diet, driving,
unsafe sex, poverty, etc..
 Physical hazards: fire, tornado, volcanic eruption,
earthquake, etc..
 Chemical hazards: harmful chemicals in the air,
water, soil and food. Example: DDT or PCBs
 Biological hazards: pathogens (bacteria, virus,
parasites), pollen, animals, plants.
Which type of hazard do these fit into?
Toxicology
Fig. 19-4 p. 411
Toxicity
Dosage
Bioaccumulation
Biomagnification
Synergism
Response
Acute effect
Chronic effect
Fig. 19-3 p. 411
TOXICOLOGY: Assessing
Chemical Hazards
Toxicity: measure of how
harmful a substance is
in causing injury,
illness, or death to
living organisms.
FACTORS
AFFECTING
TOXICITY:
1) Dose: the amount of
substance ingested,
inhaled or absorbed.
Factors Affecting Toxicity
2) Age of individual
3) Immune System
(detoxification)
4) Genetic Makeup
5) Length and
frequency of
exposure
Factors Affecting Harm Caused
By A Substance
1) Solubility (water
soluble move through
environment easily)
2) Fat Soluble (can
accumulate in body
tissue and cells)
3) Persistence (how long
before it breaks down)
• Bioaccumulation
• Biomagnifications
Factors Affecting Harm Caused
By A Substance
4) Chemical interactions
For instance: workers
exposed to asbestos
increase risk of long
cancer by 20 times, if
they smoke also 400
times.
Response: they type of
damage (acute vs.
chronic)
Principles of Toxicology
Any synthetic or natural
chemical can be
harmful if ingested in
large enough quantity.
THE DOSE MAKES
THE POISON
Critical questions: what is
the lowest level that will
cause harm?
Principles of Toxicology
Trace amounts of chemicals
in the environment may
or may not be harmful.
Some say they are not, look
at life expectancy over
last several centuries.
Some say they are, look at
cancer rates and say it is
hard to know long-term
impacts.
Poisons
 Median lethal
dose (LD50): at
what dosage does
the toxin kill 50% of
animals (usually
mice or rats)
Fig. 19-5 p. 413
Principles of Toxicology
How do scientists
determine toxicity:
1) Epidemiologic case
studies
2) Animal Testing
(usually with control
groups)
3) Computer modeling
Dose-Response Curves
 Dose-response  Nonthreshold  Threshold
Fig. 19-6 p. 414
Principles of Toxicology
How good are the
estimates of
toxicology?
There are serious
limitations to all these
types of studies.
Therefore, most allowable
limits are set well
below estimated
harmful levels.
Sections 1 and 2 Review
• What is risk? What are the major types of
hazards?
• What determines if a chemical is hazardous?
• What are the basic principles of toxicology?
• Can a little bit of pollution actually be good for
you?
• How good are estimates of toxicity?
Section 3: Chemical Hazards
• What are toxic and hazardous chemicals?
• What are some possible impacts from chemical
hazards?
• Are hormonally active agents a human health
threat?
• Why do scientists no so little about the impacts
of chemicals on human health?
• Is pollution prevention the answer?
What are toxic and hazardous
chemicals?
Toxic Chemical: a
chemical through that
can cause temporary or
permanent harm or
death.
Hazardous Chemical: can
harm humans because it
is flammable or
explosive.
Types of Toxic Agents
Mutagen: causes changes
to ones DNA.
Teratogens: chemicals
that cause birth defects
to fetus or embryo.
(alcohol)
Carcinogens: cause
cancer (growth of
cancerous tumors)
Impacts of Chemicals on Humans
Chemicals may also
impact:
• Immune system
(arsenic, dioxin)
• Nervous System
(neurotoxins, brain,
spinal cord, etc.)
• Endocrine System
(levels of hormones)
Hormonally Active Agents
Exposure to low level
certain synthetic
chemicals may disrupt a
bodies hormone levels
• Endocrine disrupters or
hormonally active
agents
So called, gender benders
Establishing Guilt Is Difficult
Under current laws, most
chemicals are
considered innocent
until proven guilty.
“Toxicologist know a
great deal about a
few chemicals, a
little about many, and
nothing about most.”
Establishing Guilt Is Difficult
U.S. National Academy of
Sciences estimates that only
10% of the 80,000
chemicals in commercial
use have been tested for
toxicity.
Why?
• Not required (considered innocent)
• Lack of funds, personnel, facilities
• Expensive
• Difficult to test interactions
Pollution Prevention Model
Where do we go from
here?
We do not know much
about all of the
chemicals inside us,
around us
Eliminating them mean
other problems
Some say Pollution
Prevention,
Pollution Prevention Model
Precautionary Principle:
where there is plausible,
but incomplete
scientific evidence of
significant harm we
need to take action to
reduce the risk.
“Better Safe Than Sorry”
Pollution Prevention Model
First: new chemical
technologies would be
considered harmful until
studies say otherwise.
Second: existing chemicals
that appear to be harmful
would be removed from
use.
EU close to adopting this
type of approach.
Review Chapter 19 Section 3
• What are toxic and hazardous chemicals?
• What are some possible impacts from chemical
hazards?
• Are hormonally active agents a human health
threat?
• Why do scientists no so little about the impacts
of chemicals on human health?
• Is pollution prevention the answer?
Chemical Hazards
Hazardous chemicals
Mutagens
Teratogens
Carcinogens
Neurotoxins
Hormonally active agents
Precautionary principle
Section 4: Biological Hazards
• What are nontransmissible and transmissible
diseases?
• Case studies: 1) Germ resistance to
antibiotics, 2) Global Tuberculosis
Epidemic, 3) HIV and AIDS Threat, 4)
Malaria Comeback, 5) Bioterrorism: A
Growing Threat, 6) Solutions: How can
we reduce the Incidence of Infectious
Diseases?
Transmittable and Nontransmittable
Diseases
Nontransmissible: caused
by something other than
a living organism and
does not spread from
person to person.
(cancer, diabetes, etc.)
Transmissible: caused by
living organisms and
can spread from person
to person. (bacteria,
virus, parasite)
Transmittable and Nontransmittable
Diseases
According to WHO: 30%
of deaths are
nontransmissible and
26% transmissible IDs
and 12%
nontransmissibe
cancers.
Transmittable and Nontransmittable
Diseases
Good News: Since 1950,
ID death rates fallen
dramatically.
Bad News: Bacteria
resistance growing and
insects becoming
immune to pesticides.
Biological Hazards: Diseases
Nontransmissible disease
Transmissible disease
Pathogens
Vectors
Tuberculosis
HIV/AIDS
Malaria
Fig. 19-13 p. 425
TB Kills 1.7 million people per year.
Reducing Infectious Diseases
Fig. 19-15 p. 426
Bioterrorism
 Possible targets: air, water, and food
 Inexpensive
Fairly easy to produce biological agents
Recombinant DNA techniques
Refer to Fig. 19-16 p. 427
Case Studies Jigsaw
1) Germ resistance to antibiotics, 2)
Global Tuberculosis Epidemic, 3)
HIV and AIDS Threat, 4) Malaria
Comeback, 5) Bioterrorism: A
Growing Threat, 6) Solutions: How
can we reduce the Incidence of
Infectious Diseases?
Section 19-5 Risk Analysis Goals
Risk Analysis
Risk analysis
Comparative risk analysis
System reliability
Risk management
Risk perception
Risk Analysis
Fig. 19-17 p. 428