Risk Assessment: What's It All About?
Risk Assessment: What’s It All About?1
What is risk assessment?
Risk assessment is a process by which scientists evaluate the potential
for adverse health or environmental effects from exposure to naturally
occurring or synthetic agents. These agents include (1) chemicals
such as those that occur in food naturally, food additives, drugs,
and environmental contaminants, and (2) physical agents, such as
radiation or electromagnetic fields. Risk assessment typically includes
an estimate of the probability of harm, such as the probability
of liver toxicity after use of a particular drug or the effect that
a chemical in the environment may have on wildlife, and a clear
description of the various assumptions and uncertainties that go
into the risk assessment.
What is the goal of risk assessment?
The goal of risk assessment is to provide risk managers, who might
be, for example, government regulatory officials, industry health
and safety directors or public health officials, with a rational
basis for making decisions about managing the use of chemicals or
physical agents in order to protect health and the environment.
The decision-making process often involves factors in addition to
the risk assessment results, such as social values, technical feasibility
and economic factors. Risk assessment is used as part of the decision-making
process to ensure public protection against unacceptable risks and
to allow the use of products whose benefits outweigh the risks associated
with their use. Examples include medicines which may produce side
What is involved in risk assessment?
As described by the National Research Council of the National Academy
of Sciences2, risk assessment involves four components:
Hazard identification—an evaluation of the adverse health effects
the agent is capable of causing. Examples might include the capacity
of an agent to cause liver or nervous system damage or to cause
cancer. Dose—response assessment—a determination of how much
of an agent is required to cause a toxic effect, and prediction
of exposure levels at which risk is likely to be negligible or nonexistent.
Exposure assessment—a determination of how much of an agent people
might be exposed to under various conditions such as use of a drug
or a consumer product, environmental exposure at a hazardous waste
site. Risk characterization—an integration of the pertinent information
from the preceding steps to characterize the risks to the exposed
population—e.g., what is the likelihood that there will be an
increase in cancer in a population exposed to a particular contaminant
in drinking water? What is the likelihood of liver toxicity if an
individual uses a particular drug? The risk characterization also
includes an explicit description of the assumptions and uncertainties
that go into the risk assessment, and the overall confidence in
the results of the analysis. It is important to note that even for
very toxic chemicals, if the exposures are low enough, the risks
may be very low or nonexistent. The principle that "the dose makes
the poison" is a basic tenet of toxicology. It should also be recognized
that the longer and healthier life that most of us enjoy can, in
large part, be attributed to the proper use of chemicals (including
medicines) that benefit people. Toxicology has played a key role
by defining the conditions of use under which we may safely employ
chemicals for good causes as well as conditions under which the
use of a particular chemical should be avoided or eliminated.
Why is the Society of Toxicology
interested in risk assessment?
Toxicology provides essential information for the risk assessment
process. Basically, toxicologists provide much of the underlying
scientific data regarding how chemicals might affect humans and
the environment. The Society of Toxicology (SOT) believes that risk
assessment and its application in decision-making can be greatly
improved through the incorporation of sound science in the process
and by educating those who use risk assessment in decision-making
about the strengths and limitations of the science.The Society of
Toxicology views the enhancement of the scientific basis of risk
assessment as a high priority issue. Accordingly, its strategic
plan includes components aimed at stimulating research to improve
the risk assessment process, and educating scientists, regulators,
the media and the lay public about the importance of the use of
sound science in risk assessment. Furthermore, the Society is interested
in promoting the use of risk assessments based upon sound science
by regulatory agencies. Pursuant to these goals, the Society of
Toxicology has adopted a set of Principles for Research Priorities
in Toxicology; these are presented below.
Principles for Research Priorities
Support the advancement of basic and applied research in toxicology,
and incorporation of sound science into risk assessment, are the
first two items addressed in our Long-range Plan, adopted in June,
1997. Accordingly, Council has approved the following statement
concerning principles for research priorities in toxicology in order
to highlight the Society of Toxicology’s commitment to research
in the context of our concern for human health and the environment.
Classic toxicity testing, involving the use of animal models, has
served us well and will continue to do so in the future. However,
we affirm the need to continue to strive for improvement in accord
with the following principles.
- A focus on basic research aimed at discerning the mechanism/mode
of action of the agent of interest is of fundamental importance.
Toxicology is a basic biomedical science because the study of
mechanisms of toxicity leads to enhanced insight regarding our
understanding of essential aspects of biology.
- Knowledge of mechanisms underlying the toxicity of the agent
of interest is required in order to facilitate the incorporation
of sound science into risk assessment. This is a critical aspect
of our Society’s strategic plan. The overall goal is to enhance
our ability to make reasonable estimates as to whether or not
harm might occur to people, or the environment, under realistic
conditions of exposure. This entails hypothesis-driven research
and it is consistent with the notion that it is the dose which
makes the poison.
- The scientific basis of risk assessment can be enhanced by the
development of improved test systems (not simply adding to the
number of existing “tests”) and improved means for interpretation
of results. Key aspects of any risk assessment include an emphasis
on: (1) dose selection; (2) dose-response relationships, including
extrapolation from high to low doses; (3) species to species extrapolation;
and (4) exposure assessment.Research should be judged on the basis
of scientific merit, without regard for funding source or where
the studies are conducted (e.g., academia, government, or industry).
1. “Risk Assessment: What’s It All About?” is intended for SOT to
use on the numerous occasions that we are called upon to present
basic aspects of risk assessment to, for example, undergraduates,
members of the news media, congressional staff, and high school
science teachers. This is a result of a project initiated by the
Task Force to Improve the Scientific Basis of Risk Assessment and
the Task Force played the major role in its development. Input was
received from SOT Council, the Risk Assessment Specialty Section,
the Committee for Regulatory Affairs and Legislative Assistance,
and the Committee on Public Communication. The contributions that
each of these groups made is acknowledged gratefully. The document
underwent a number of revisions, based upon the comments received,
and was approved by Council on November 11, 1999.
2. Science and Judgement, National Research Council, National Academy
of Sciences, National Academy of Sciences Press, Washington, DC,
3. Approved by SOT Council, 1998; published in the Society's newsletter,
Communiqué, Special Issue, p. 9, 1998.