Determining Decontamination Effectiveness

The SSAHP developed by the Site G contractor did not indicate that the contractors routinely conducted job- or task-specific hazard analyses. In addition, the SSAHP did not specify that PPE selection for jobs and tasks must be based on the analysis of the health hazards associated with each job. Eurthermore, the SSAHP contained no procedures for objectively determining the effectiveness of decontamination of personnel or equipment. The decontamination program required incineration of all materials that could not be readily decontaminated such materials were placed in labeled disposal containers. The program, however, did... 

M256-Series Chemical Agent Detector Kit A kit used by military personnel to detect and identify field concentrations of nerve, blister or blood agent vapors. The kit consists of twelve samplers/detectors and a packet of M8 detector paper. It is used at the squad, crew or section level to detect and identify field concentrations of nerve, blister or blood agents vapors. It is usually used to determine when it is safe to unmask, to locate and identify chemical hazards, and to monitor decontamination effectiveness. 

Laboratory and field testing determined the effectiveness of a new decontamination process for soils containing 2,4-D/2,4,5-T and traces of dioxin. The process employs three primary operations - thermal desorption to volatilize the contaminants, condensation and absorption of the contaminants in a solvent, and photochemical decomposition of the contaminants. Bench-scale experiments established the relationship between desorption conditions (time and temperature) and treatment efficiency. Laboratory tests using a batch photochemical reactor defined the kinetics of 2,3,7,8-TCDD disappearance. A pilot-scale system was assembled to process up to 100 pounds per hour of soil. Tests were conducted at two sites to evaluate treatment performance and develop scale-up information. Soil was successfully decontaminated to less than 1 ng/g... 

Confirmatory sampling is used by the decontamination crews to determine the effectiveness of the cleaning technique being employed. If a cleaned surface tests clean, the surface should be isolated from further airborne deposition. 

In the Dilute Chemical Decontamination (DCD) process developed by Westing-house, a solution of citric acid, oxalic acid, EDTA and an inhibitor is applied, resulting in decontamination factors on the order of 10, as was determined in laboratory studies higher efficiencies were obtained when a pre-oxidation step was included (Murray et al., 1985). In order to improve the decontamination effectiveness, it was proposed that the spent solution be circulated over a porous DC electrode where dissolved ions are reduced. The Fe " ion generated in this manner is assumed to attack the contamination layer in a one-electron reaction, thus accelerating the dissolution of the oxides (Murray and Snyder, 1985). However, this process seems not yet to have been applied to operating light water reactor plants. 

Two studies determined the effects of oropharyngeal decontamination alone, and one determined the effect of oropharyngeal decontamination and systemic prophylaxis on the incidence of VAP (see Table 4) (74-76). Only one of these studies used a placebo-controlled, double-blind study design (74). Although significant reductions in the incidence of VAP were reported in all three stud-... 

What is the criterion that determines whether a decontamination procedure was effective It is not the absolute absence of any chemical contaminants in the equipment blank. Important for the project are only the contaminants of concern and their concentrations. For site investigations, when no information is available on existing pollutants, it may be important that no contaminants of concern are present in equipment blank samples above the laboratory PQLs. On the other hand, for site remediation projects, the presence of contaminants of concern in equipment blank samples may be acceptable, if these concentrations are only a fraction of the action levels. The decision to decontaminate equipment and the selection of the acceptability criteria for equipment blanks are made in the DQO process based on the intended use of the data. 

Instead of applying the DQO-blind protocol requirements, we should always determine the need and extent of decontamination based on the intended use of the data. Understanding the DQOs will allow the project team to develop decontamination procedures that are cost-effective and appropriate for the contaminant concentration range being measured and the action levels applied. The following questions need to be answered in the planning phase ... 

Benton et al. (2006b, 2007) experimentally determined the LCtso and LC50 in male and female adult SD rats exposed whole body to VX vapor for 10, 60, and 240 min in a dynamic exposure chamber (Table 6.3) study protocol was similar to that for agent GB in the studies conducted by Mioduszewski et al. (2001, 2002a). Experiments testing the role of decontamination less than 24 h post-exposure provided clear evidence for percutaneous toxicity induced by whole-body vapor exposure to the persistent nerve agent VX. For severe and lethal VX vapor exposure effects, females were not more susceptible than males for the exposure durations examined. 

Destruction of undesirabie poiiutants is a common practice in the environmentai fieid that has taken wide use of US for acceierating degradation processes. Thus, the mechanisms of US action on ceiiuiar materiai have been ciarified [105] and the effect on its destruction demonstrated as efficient. Unfortunateiy, the need for high US intensities makes the technique expensive to use for generai microbioiogicai decontamination. However, this degradation method can be anaiyticaiiy usefui with a view to identify and (or) determine key components after fast sampie preparation. 

The ideal chemical separation method should be relatively simple, have few separation stages and should be time / cost effective. Itoh et al (2002) used a combined anion and cation exchange column method for the isolation of Ca from other alkaline earth metals. This 3 column separation involved 6 chemical separation techniques following two HF/HCIO4 digests. The decontamination factors for Eu and Co are quoted as >10. The final limit of detection for " Ca for this method was 8 Bq/g, based on a measurement by X-ray spectrometric determination. 

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