Personal monitors limitations

They may differ, however, from the actual irradiation conditions experienced in the workplace. The disparity of irradiation conditions results in differences in response that cannot be fully simulated and represent basic limitations in the accuracy of personal monitors. Some of these limiting conditions are ... 

Current federal regulations limit the deep dose equivalent based on that part of the body likely to receive the highest exposure. If personal monitor results are not available or the personal monitor was not located at the position of highest exposure, the regulations allow the substitution of surveys and other radiation measurements (NRC, 1991). These requirements strongly influence the current practices in the United States for the number and location of personal monitors on individuals. 

This Section is limited to a general discussion on the number and location of personal monitors eind other devices used to monitor deep dose equivalent. Other devices are commonly used to monitor dose equivalents in the extremities, skin and lens of the eye, for demonstrating compliance with the separate dose limits for deterministic effects in those tissues. These latter devices are not germane to this Report. 

Provision 1 is a continuation of current practice, but is used only when the reported deep dose equivalent does not exceed 25 percent of the specified limit. Provision 2 comes from application of a previous observation by NCRP (1978c) in conjunction with the proposal by Webster (1989) noted below. The observation was that exposure of the face and neck will exceed the exposure recorded under the apron by factors between 6 and 27. Using the smallest value in the range i.e., a factor of six) and the formula of Webster (1989), the result is the value of 0.3. Provision 3 comes from application of a proposal by Webster (1989) for the use of two monitoring devices, based on the experimental data of Faulkner and Harrison (1988). The proposal of Webster (1989) is discussed in Section 3.3.3. However, more recent information is available from which to derive conversions for both He and E from personal monitor values ofHp(lO). The current NCRP recommendations using this additional information are developed in Sections 3.3.2, 3.3.3 and 3.3.4. 

This Report is one of the series developed under the auspices of Scientific Committee 46, a scientific program area committee of the National Council on Radiation Protection and Measurements (NCRP) concerned with operational radiation safety. The Report provides practical recommendations on the use of personal monitors to estimate effective dose equivalent (Hg) and effective dose (E) for occupationally-exposed individuals. The Report is limited to external exposures to low-LET radiation. Recent additions to the radiation protection literature have made the recommendations possible. In order to avoid delay in utilizing the recommendations in the United States, the quantity as well as E, has been included until such time as the federal radiation protection guidance and associated implementing regulations are revised to express dose limits in E as recommended by the NCRP. 

Additional Sensors. At this writing, other personal monitoring sensors for noise, heat stress, radiation, etc., are under development for incorporation into the Chronotox System. As previously indicated, there is no limit to the application... 

Five of the criteria are normally considered when any air pollution monitor is designed however, the fifth criterion—portability—is essential in a personal monitor. Obviously, this requirement has an impact on the other criteria because it establishes a challenge for achieving specificity for a chemical or suite of chemicals, for low detection limits for adequate determination of the concentration and exposure, and for units that are not cost-prohibitive. Sensitivity of current personal monitors is less than that for stationary monitoring techniques. Thus, entirely new approaches appear to be necessary for detection of a contaminant in a personal monitor. 

OSHA requires employers of workers who are occupationally exposed to 2-butoxyethanol to institute engineering controls and work practices to reduce employee exposure and maintain it at or below pennissible exposure limits (PEL). The PEL for 2-butoxyethanol is 50 ppm (OSHA 1974). Workers exposed to 2-butoxyethanol should wear personal protective equipment such as gloves, coveralls, and goggles to protect exposure to tire skin (OSHA 1974). NIOSH recommends that industrial hygiene surveys be completed at work places where airborne exposure to 2-butoxyethanol or 2-butoxyethanol acetate may occur (NIOSH 1990). If exposure levels are at or above one-half the recommended exposure limit (REL = 5 ppm), NIOSH recommends that a program of personal monitoring be instituted so that tlie exposure of each worker can be estimated. If exposure levels are at or greater than the REL, or if there is a potential for skin contact, NIOSH recommends that 2-butoxyacetic acid be measured in the urine of the workers. 

In order to get instantaneous results, continuous filter tape instruments have been developed based on modification of the colorimetric Marcali method. The instruments have been used for continuous air monitoring of production sites and for personal monitoring of isocyanates. A limitation with the filter tape instruments is that no compound-specific information is given in means of retention times or detector specific structural information. Since the instruments have to be calibrated for the different isocyanates, quantitative estimation of mixed isocyanate exposures is troublesome. Problems associated with influence of interfering compounds, humidity, and collection of particles have been reported. " ... 

Available data based on limited exposure tests in chambers and comparisons with pumped sampling methods in the laboratory and field show the techniques can be used to determine mean concentrations of VCX3s over periods of a day to several weeks for fixed site and personal monitoring. Problems of poor recovery at the desorption stage and possible losses by back diffusion means the investigator needs to consider carefully the choice of sampler and, in the case of thermally desorbable tubes, the optimum sorbent for the investigation. 

Chlordane has been detected in outside urban and rural air, in indoor air, and in the breathing zone during personal monitoring (Table 5-2). In urban air, mean concentrations have ranged from below the detection limits (generally <0.1 ng/m to 58 ng/m, whereas rural and background concentrations are much lower (0.01-1 ng/m ... 

In mostresearch laboratory situations, it would be unusual to find an airborne radioactivity area on otherthan a short-term basis. If there is any possibility ofan approach to the limits while working on an open bench, the use of radioactive materials should be restricted to a hood, or in a glove box or hot cell. In a facility with a broad license, it is recommended that at least some ofthe more active individuals using radioisotopes should be included in a bioassay program for the same reason that others weara personal monitoring device, to ensure and document that no one is receiving an internal dose over the limits. 

Bhatt et al. (1994) describe the results of intercomparison of CaS04 Dy teflon discs as personal monitoring TLDs. The work was conducted independently in Japan and Australia. The irradiations were performed free in the air and on the surface of water and PMMA-equivalent composite phantoms. The performance of the analysis was according to the ANSI-Nl 3-1983 criteria. Results were also analyzed according to the trumpet curve analysis with the requirements of ICRP-35 and ICRP-60. The results showed satisfactory performance of the TLDs which fell within the limits of the requirements. 

To use personal monitoring (sampling) facilities to assure that adequate ventilation is present so employees are not exposed to concentrations of solvent above the 8-hr exposure limit (Table 1.14). 

Unless established monitoring practices are conducted by plant personnel or the OSHA compliance officer, the results are of limited value in determining compliance with a standard, and what is more important, protecting the worker s health. The conduct of air monitoring by untrained, or poorly trained, persons relegates the program to a "numbers game" which serves no useful purpose. 

While occupational hygiene measurements always measure only the concentrations of chemical compounds present in the occupational environment, i.e., the potential dose, the analysis of biological specimens predominantly reflects the body burden. Furthermore, biological monitoring is always limited to assessment of individual exposure. Personal occupational hygiene sampling takes into consideration only some of the individual factors, e.g., working... 

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