Risk Assessment and Characterization


Application of Regulations
Risk UK Focus
Risk US Focus

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 measured.

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 assessment

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.

Last Modified: June 12, 2001
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