Risk Assessment:
A Review of Some Risk Assessment
Basics
Dr. Doug McLaughlin
November 20, 2013
Risk Assessment
• Paracelsus
– a 16th century Swiss physician
– published the first monograph on occupational diseases of
miners and smelters
– identified/distinguished between acute and chronic toxicity
– died at the age of 48 from wounds received during a tavern
brawl – an example of the need to keep types of “risk” in
perspective!
• Established a basic tenet of modern toxicology:
– “What is not a poison? All things are poison and nothing is
without poison. It is the dose only that makes a thing not a
poison.” (Ottoboni, 1997)
– In other words: “The dose makes the poison.”
Acute Dose-Mortality Response Curve
LD50 = the dose that is lethal to 50% of the test population
from Ottoboni (1997)
A More Complete Dose-Response
Curve for Many Chemicals
from Ottoboni (1997)
Examples of Lethal Doses
Chemical
Table salt
Caffeine
dioxin
(2378 TCDD)
LD50
(rat, oral dose, g/Kg)
3
0.192
0.00002
LD50 = the dose that is lethal to 50% of the test population
Role of USEPA
• USEPA is responsible for providing risk
assessments under environmental laws
governing:
– Clean air, clean water, toxic substances, drinking
water, endangered species, pesticides, numerous
others
– This lecture presents information obtained from
www.epa.gov/risk on EPA’s approach for risk
assessment
EPA Risk Assessment Basics
• Definition of “Risk”
– The chance of harmful effects occurring to human
or ecosystem health due to exposure to a stressor
in the environment.
• Definition of “Stressor”
– Any physical, chemical, or biological entity that
can induce an adverse response (i.e., cause a
harmful effect)
Risk Assessment Basics
• Definition of “Risk”
– The chance of harmful effects occurring to human
or ecosystem health due to exposure to a stressor
in the environment.
• Definition of “Stressor”
– Any physical, chemical, or biological entity that
can induce an adverse response (i.e., cause a
harmful effect)
Risk Assessment
• Definition
– Characterizes the nature (i.e., type) and
magnitude of health risks to human and ecological
receptors (i.e., organisms) from environmental
stressors.
• Two general types of environmental/chemical
risk assessments
– Human health
– Ecological
The Level of Risk Depends On:
• The amount of stressor present in the
environment
• The potency of the stressor
• The degree of exposure of a receptor to the
stressor
Risk Assessment Process
the potential to cause harm if exposure occurs
Hazard Identification
-What problems may be
caused by the pollutant?
Dose-Response
Assessment
-What effects arise at
different exposures?
Exposure Assessment
-How much of the pollutant
are organisms exposed too?
For how long?
how much exposure has occurred
Risk Characterization
-What is the resulting
risk to the exposed
population/organisms?
the probability of harm
given the chemical hazard
and the exposure that
has occurred
based on information at http://www.epa.gov/risk/hazardous-identification.htm
Types of Questions Addressed by
Human Health Risk Assessments
• What types of health problems may be caused
by environmental stressors such as chemicals
and radiation?
• What environmental stressors are people
exposed to and at what levels and for how
long?
• Are some people more susceptible to, or more
likely to be exposed to, particular stressors?
Types of Questions Addressed by
Ecological Risk Assessments
• How would the construction of a dam impact fish
populations in nearby water bodies?
• How likely is it that the residential or agricultural
application of an insecticide will harm an
endangered species?
• What is the risk of introducing a non-native
oyster to an estuary?
• How does fertilizer runoff reduce oxygen levels in
a water body and what harmful effects may
occur?
Steps of a Human Health RA
• Planning/scoping
– Outline of receptors and stressors of concern, possible
exposure pathways, information needs, etc.
• Hazard identification
– Describe the types of health problems/adverse
responses expected, and how the stressor causes the
responses (e.g. interactions at the cellular level)
• Dose-response/exposure-response assessment
– Describe (quantitatively) the degree of adverse
response associated with exposure to a given amount
of a stressor
Steps of a Human Health RA, cont’d
• Exposure assessment
– Measure or estimate the magnitude (how much),
frequency (how often), and duration (how long) of
exposure
• Risk characterization
– Integrate information from the previous steps to
summarize the chance of adverse effects
occurring in the population of interest due to the
presence of the stressor
Local Example: Kalamazoo River
• An example from the Kalamazoo River:
Final (Revised) Human Health Risk Assessment, Allied Paper,
Inc./Portage Creek/Kalamazoo River Superfund Site
•
http://www.michigan.gov/deq/0,1607,7-135-3311_4109_4217_28657-85245--,00.html
Kalamazoo River
from Kalamazoo River HHRA
ABSA = Aquatic biota study area
from Kalamazoo River HHRA
“Using both average and maximum fish concentrations, cancer risks for subsistence
anglers in all study areas were outside (greater than) the EPA target cancer risk range
of 1 in 1 million to 1 in 10,000 and above the MDEQ risk threshold of 1 in 100,000.
Hazard quotients for subsistence anglers in all study areas were greater than the
acceptable EPA and MDEQ hazard quotient threshold of 1.”
A key point: Assumptions in risk assessments matter, and should be evaluated carefully.