Hazardous waste, risk assessment

Radioactive waste disposal—Risk assessment. 2. Hazardous wastes— Risk assessment. 3. Hazardous wastes—Classification. I. National Council on Radiation Protection and Measurements. II. Series. 

PRINCIPLES, DEFINITIONS, AND PERSPECTIVES OF HAZARDOUS WASTE RISK ASSESSMENTS... 

Table 2 Elements of sources, pathways, and receptors algorithm used in hazardous waste risk assessments.

Scientists and engineers involved in hazardous waste risk assessment often have an innate appreciation of the risks associated with hazardous wastes. However, the pubhc, especially those who live near a hazardous waste site or facility, require information regarding the risk assessment process, its uncertainties, and the value judgments that have been made. This information is conveyed through risk communication, an integral part of the risk assessment process. 

Monitoring to estimate exposure is essential to risk assessment near sources of exposure. Cost-effective hazardous waste site assessments include three phases (1) preliminary site assessment, utilizing aerial photography and site inspections ... 

Sandness, G. A. Dawson, G. W. Mathieu, T. J., and Rising, J. L. "The Application of Geophysical Survey Techniques to Mapping of Wastes in Abandoned Landfills, Proceedings of the 1979 Conference on Hazardous Materials Risk Assessment, Disposal and Management, April 25-27,... 

Where hazardous chemical(s) are used they should be assessed to determine the impact on the environment. Such an assessment should also consider the effect of intermediates and breakdown products that may be produced. The assessment should include consideration of the effect of the materials on the atmosphere, the sewage treatment system, controlled waters, land and groxmdwater, and waste disposal routes. The risk assessment should include an estimation of the risk from the hazardous materials, the magnitude of the effects, and the probability of an occurrence. Included should be an evaluation of the significance of the hazards and the consequences should the environment be affected. It is a structured approach to setting priorities for controlling the hazards. The risk assessment will provide iiiformation of where control measures will need to be applied to prevent an impact on the environment. 

Many companies use worker—management teams, suggestion boxes, consultant surveys, suppHer training sessions, and other methods to reduce risk of injuries (see Hazard analysis and risk assessment). The principal regulatory burden falls on wastes and discharges which leave the plant (3,53,54). 

The preliminary assessment of noncarcinogcnic risk associated with a hazardous waste site as recommended by the USEPA is typically calculated in four major steps (6). 

Mere destruction of the original hazardous material is not, however, an adequate measure of the performance of an incinerator. Products of incomplete combustion can be as toxic as, or even more toxic than, the materials from which they evolve. Indeed, highly mutagenic PAHs are readily generated along with soot in fuel-rich regions of most hydrocarbon flames. Formation of dioxins in the combustion of chlorinated hydrocarbons has also been reported. We need to understand the entire sequence of reactions involved in incineration in order to assess the effectiveness and risks of hazardous waste incineration. 

PBPK models improve the pharmacokinetic extrapolations used in risk assessments that identify the maximal (i.e., the safe) levels for human exposure to chemical substances (Andersen and Krishnan 1994). PBPK models provide a scientifically sound means to predict the target tissue dose of chemicals in humans who are exposed to environmental levels (for example, levels that might occur at hazardous waste sites) based on the results of studies where doses were higher or were administered in different species. Figure 3-4 shows a conceptualized representation of a PBPK model. 

Reliable monitoring data for the levels of endosulfan in contaminated media at hazardous waste sites are needed. This information could be used in combinahon with the known body burdens of endosulfan to assess the potential risk of adverse health effects in populations living in the vicinity of hazardous waste sites. 

ENVIRONMENTAL SAMPLING FOR HAZARDOUS WASTES Table I. The Process of Environmental Risk Assessment... 

Exposures of Children. Children will be exposed to americium in the same manner as adults in the general population (i. e., ingestion of food and water and inhalation of air). Americium is potentially found at hazardous waste sites at elevated levels. Since children may have oral exposure to soil through hand-to-mouth activity, bioavailability studies of americium in soil via the oral route may be useful to assess the risk of this type of exposure. 

To control the emission of organics, these units must comply with similar DRE requirements to the other hazardous waste combustion units. Owners or operators of MACT combustion units must select POHCs and demonstrate a DRE of 99.99% for each POHC in the hazardous wastestream. Sources that bum hazardous waste have a required DRE of 99.9999% for each POHC designated. Additionally, for dioxins and furans, U.S. EPA promulgated more stringent standards under MACT. For example, MACT incinerators and cement kilns that bum waste with dioxins and furans must not exceed an emission limitation of either 0.2 ng of toxicity equivalence per dry standard cubic meter (TEQ/m3) or 0.4 ng TEQ/m3 at the inlet to the dry particulate matter control device. This unit of measure is based on a method for assessing risks associated with exposures to dioxins and furans. 

U.S. EPA may list a waste as hazardous for any and all of the above reasons. The majority of listed wastes fall into the toxic waste category. To decide if a waste should be a toxic listed waste, U.S. EPA first determines whether it typically contains harmful chemical constituents. An appendix to RCRA contains a list of chemical compounds or elements that scientific studies have shown to have toxic, carcinogenic, mutagenic, or teratogenic effects on humans or other life forms. If a waste contains chemical constituents found on the appendix list, U.S. EPA then evaluates 11 other factors to determine if the wastestream is likely to pose a threat in the absence of special restrictions on its handling. These additional considerations include a risk assessment and study of past cases of damage caused by the waste. 

On July 18, 2000, the Agency released HWIR-waste exemption levels for 36 chemicals that were developed using a risk model known as the Multimedia, Multi-pathway and Multi-receptor Risk Assessment (3MRA) Model.17 The May 16, 2001, HWIR-waste rule revised and retained the hazardous waste mixture and derived-from rules as previously discussed in this module. In addition, the rule finalized provisions that conditionally exempt mixed waste (waste that is both radioactive and hazardous), if the mixed waste meets certain conditions in the rule.5... 

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