Risk assessment for microorganisms consists first of determining or predicting the likelihood that
the microorganism that presents a hazard will actually cause a disease, cause an allergic reaction,
or be toxic to some other life form or disturb the ecology. Risk assessment of most macroscopic
land plants and animals are largely questions of feasibility of containment. A sound scientific
base is required for a credible risk assessment. Hazard and exposure must be defined and
For example, there are many elements involved in estimating hazard. As described previously,
hazard is a reflection of the propeties of the agent itself (e.g., virulence, potency, host range).
Exposure is defined as the amount, frequency, and duration of contact with an environmental
agent. If the agent is innocuous, presenting no hazard, then no risk is associated with the
exposure. Further, exposure is a function of such characteristics of the agent as initial amount
used, growth in the case of biological agents, resistance to environmental factors, stability, and
mobility. The information that goes into a risk assessment is a combination of the degree and
nature of the hazard combined with the hazard.
Persistence - A major element of risk assessment for environmental release of biological agents
is estimation of the persistence of the organism in that environment. If the agent naturally
disappears there is only the transient risk from the living organism. However, if the hazard is due
to a product or component of the organism and the organism does not persist, the risk assessment
largely follows that of any chemical presenting a hazard.
Competition - Risk assessment of the release of an organism in an environment will include the
determination of the ability of the organism to compete and become the dominant species in that
environment. The goats in the Galapagos, the kudzu vine in the southern U.S. are example of
releases of organisms that competed successfully and became dominant. The most competitive
organisms clearly are humans. We have become dominant in most non-aqueous environments
and even have changed environments wherein we cannot live with any permanence. Raw sewage
contaminates many ocean areas near coastal cities. There are well over a hundred known
pathogens that can present serious risk in coastal waters. Some of these persist over long periods.
Containment - Hazards and the evaluation of the level of risk in any activity utilizing living
materials varies with the degree of containment used in the procedure. That is, hazard can be
minimized or eliminated by placing a barrier between the hazardous organism and those
potentially at risk. The boundaries among the categories of containment are blurred in the
continuum from laboratory, through pilot scale through large scale industrial use or release of an
organism into the environment. Containment may or may not refer to a physical container as
such. The isolated, irrigated plot in a dessert is a form of container. Thus, any mechanism that
effectively controls and minimized spread of an organism is containment for the purposes of risk
Scale - In general, laboratory and small or pilot scale growth of organisms tends to rely more on
physical containment than on biological containment. As the scale increases, biological
containment is increasingly utilized. Furthermore, large scale activities will tend to concentrate
on organisms presenting little risk. The assessment of risk usually will be based on extensive
knowledge from testing during the smaller scale activities.
Environmental - Environmental hazards are usually due to an organism which is exotic to a
given location having a selective advantage which results in an undesirable change in the
ecosystem. Examples are given above.
Animal releases are more difficult to summarize as the mobility of animals must be taken into
account. In effect, containment, either physical or biological, is utilized to terminate a release of
animals. Once an animal escapes the containment, it may be impossible to use mitigation.
"Flying the coop" has real meaning in this situation. Once the English sparrow escaped in the
U.S., there was little chance of practical mitigation. In island situations, there is a better chance
of succeeding. However, even the combination of the island as confinement and a decided
program of killing may not succeed.