Workers who will clean up contaminated DOE sites or handle wastes generated by the cleanup will be exposed to risks to their health and safety. To calculate these risks, scientists must gather data to address several questions.
For example, what types of radiation or pollutants will a worker be exposed to? What are the likely routes of exposure--inhalation, ingestion, or direct radiation exposure through the skin? What is the estimated volume of each contaminant at the waste site? Will heavy equipment be used? In what types of activities is a worker involved--waste incineration, packaging of solid waste, solidification and stabilization of waste, use of heating processes to remove pollutants from soil (thermal desorption) or turn contaminated soil to glass (vitrification), excavation of contaminated soil, soil washing, site restoration, or transport of waste? How many workers engage in each activity and for how many hours?
For DOE's Programmatic Environmental Impact Statement, risks to remediation and waste management workers were estimated using a unit risk approach to automate the risk assessment process. The unit risk approach involves five basic steps for estimating worker risk: (1) identify alternative, (2) identify specific activities and types of workers for each alternative, (3) identify number of workers and hours required for each activity, (4) estimate unit doses for each activity, and (5) estimate unit risks.
Once the remediation method or waste management alternative is selected, the types of activities and workers required to complete site cleanup or waste handling are identified. Both the environmental restoration (ER) and waste management (WM) teams have developed automated user-friendly data bases for choosing typical activities required for a particular remediation or waste treatment method. These activities, occurring sequentially, form a "treatment or technology train"). The ER data base includes 58 of the most widely used ER technologies, and the WM data base contains 32 possible waste management modules--waste treatment, storage, or disposal activities.
The data bases also include various types of workers such as heavy equipment operators, laborers, supervisors, and waste handlers. It is important to estimate the types of workers involved in an activity because the type of workers affects a worker's exposure. For example, because a laborer is closer to a waste than a supervisor is, the laborer is more likely to be exposed to contamination through inhalation.
An important feature of the automated risk assessment system is its incorporation of levels of worker protection. The more equipment and safety gear a worker uses, the less likely he is to be exposed to contaminants. The ER data base includes various levels of protection that can be selected to ensure compliance with DOE and Occupational Safety and Health Administration protection standards.
Identifying the number of workers and the hours required to complete a WM or ER activity is the next step in estimating worker risks. This information is available from site managers or site or DOE data bases (such as costing data bases).
Once the types and number of workers are identified, potential exposures are estimated using a suite of computer models. Unit exposures (exposure per unit contaminant resulting from inhalation, ingestion, or direct radiation exposure) are calculated using standard Environmental Protection Agency exposure assessment methods.
The ER and WM systems each include 350 of the most common contaminants found within the DOE complex, ranging from cesium and plutonium to mercury and PCBs. Unit risk factors for each contaminant, ER technology, and WM module were developed and stored in a data base developed especially for this purpose. These unit risk factors are multiplied by the unit exposures or unit doses to yield a unit risk (worker risk per unit contaminant) for each contaminant and activity involved in the alternative being evaluated.
Finally, the unit risks are multiplied by the actual inventory of contaminants at a site or waste treatment facility. Risks for each exposure pathway, activity, and contaminant are summed to yield the actual estimated risk for a given alternative or remediation method.
This worker risk assessment will provide information that may be used by decision makers trying to determine how particular DOE waste sites will be remediated and how their wastes will be managed.
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