Like the hazard identification process for chemicals, the microbe is classified according to its inherent properties. Thus risk scenarios include not only the effects resulting from the intended purpose of the environmental application, but also downstream and side effects that are not part of the desired purpose. Also, the risks may not be direct, such as a change induced by the release of organism into an environment where there are no natural predators. That said, most microbes are not considered to be pathogenic, but certain human subpopulations are susceptible to hazards that may not exist for a large proportion of the population. These classes indicate that even the safest microbes carry some risk and that with more uncertainty about an organism, one cannot assume it to be safe. No treatment or preventive measures are available. Serious adverse effects are to be expected with respect to the value to be protected, both locally and outside the area of application. Treatment and/or preventive measures are available. Serious adverse local effects are likely with respect to the value to be protected, but spread beyond the area of application is unlikely. Spread beyond the application area is highly unlikely. Local adverse effects are possible, which can either revert spontaneously (e.g., owing to environmental elasticity and resilience) or be controlled by available treatment or preventive measures. Adverse effects are possible but are unlikely to represent a serious hazard with respect to the value to be protected. Organisms in this class are considered to be safe. No adverse effect, or very unlikely to produce an adverse effect. The Safety in Biotechnology Working Party of the European Federation of Biotechnology has identified four risk classes for genetically modified microbes, which can be applied to most microbes in wastes: 1. Of course, biological agents range from beneficial to extremely hazardous. Notably biological and infectious wastes present hazards from biological agents that differ from those posed by chemical-laden wastes. Wastes often possess nonchemical hazards. For the most part, however, health effects research has focused on early indicators of outcome, making it possible to shorten the time between exposure and observation of an adverse effect. Risk assessors now can apply biomarkers of genetic damage (i.e., toxicogenomics) for more immediate assessments, as well as improved structure-activity relationships (SAR), which have incrementally been quantified in terms of stereochemistry and other chemical descriptions, that is, using quantitative structure-activity relationships (QSAR) and computational chemistry. A number of tools have emerged to assist in this characterization. Thus characterizing the inherent properties of an individual constituent of a waste is but the first step in waste risk assessment. A key question is how do the individual constituent's physical and chemical properties affect those of other waste constituents and vice versa? Are there additive, synergistic, or antagonistic effects when exposed to different substances simultaneously. From an exposure perspective, a mixture is actually a coexposure. A number of recent toxicological studies have begun to look at multicomponent mixtures. Until relatively recently, toxicologists studied mixtures in a step-wise manner, adding substances one at a time to ascertain the response of an organism with each interaction. People and ecosystems are exposed to an array of compounds simultaneously. For example, relatively nonreactive substances may become bioavailable in fatty or low pH substrates, leading to highly toxic leachates. These substrates and matrices may also make the wastes more dangerous. Some of the constituents are relatively nontoxic, but are the substrates and matrices within which the hazardous constituents reside. Within an environmental and public context, mixtures are combinations of constituents having unique hazards. The chemical definition distinguishes mixtures from compounds. Source: National Research Council, Risk Assessment in the Federal Government: Managing the Process, National Academy Press, Washington, DC, 1983.Īlmost all wastes are mixtures. The inner circle includes the steps recommended by the National Research Council. Risk assessment and management paradigm as employed by environmental agencies in the United States.
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