Similar exposure groups

To avoid any inconsistencies in the final results, one should only deviate from the measurement plan after consultation with the responsible person. All activities of the workers should be recorded and documented in detail as much as possible otherwise the results may not be interpretable. The use of a form as a standardized work description for the documentation of all tasks during a measurement has been proved to be valuable in practice. It should include the person s name. In most cases not every member of a work force can be used for measurements. Therefore it is important to select representative test persons belonging to a similar exposure group. 

The reliability of a database is enhanced and the adminishative burden eased by grouping workers who have similar duties or who work in proximity to each other. Each of these Similar Exposure Groups (SEGs) will have a certain exposure profile. Health and safety analysts then can use pooled exposure data to determine the probability that a member of any given SEG has encountered a particular risk. Once an adequate database is available and a clear frequency distribution emerges, EC recommends the following ... 

Develop a clear picture of where the risks are in each of the project plants with respect to location in the plant, type of process in the plant, type of event or activity and within Similar Exposure Groups (SEGs). 

Plant 5 fractionates natural gas liquids (C2+, C3+) streams into products including ethane, propane, hutane, pentane and natural gasohne. Exposure monitoring efforts focused on turnaround operations on one of the fractionation trains. Similar exposure groups monitored included welding, confined space entry during inspections, and manual removal of scale from process vessel internal walls. All personal exposure and ambient air sample results were below the AL. Results from the analysis of process samples are presented in the following table ... 

Homogeneous exposure group A population or group of workers with similar exposure. 

Similar studies showed a positive association between HLA alleles and development of IgE antibody. Sensitized platinum workers were DR3+ and DR6- while non-sensitized workers were DR3- and DR6+ [37], The linkage between HLA phenotype and development of IgE antibody was greatest among the low exposure group. A second study showed a relationship between HLA DR3 and IgE to inhaled anhydrides [38], A study among detergent workers showed a positive association between HLA-DR4+ and IgE antibody to the serine protease derived from Bacillus licheniformis [39],... 

The number of investigations on the enantioselective dipolar cycloaddition of nitronates is still rather limited. In the case of simple alkyl nitronates, the facial selectivity is controlled solely by the steric environment about the two faces of the chiral unit. For example, the reaction of steroid dipolarophile 270 proceeds with the nitronate approaching the Re face of the alkene (Eq. 2.23) (234). The facial selectivity is controlled by the C(19) methyl group, which blocks the Si face of the dipolarophile. Similarly, exposure of 279 to ethyl acrylate at 40 °C for 24 h, provides a single nitroso acetal (Scheme 2.21) (242). The facial selectivity is presumed to arise from steric shielding by the menthol group, however the full stereostructure has not been established. 

Groups of 4 male albino ChR-CD rats were exposed to various concentrations of HDl for 4 or 8 hours. When rats were exposed to 370 ppm, they died after 2-3 hours of exposure. Prior to death, rats showed signs of irritation, gasping, and convulsions. Tracheitis, pleural effusion, and small areas of pulmonary hemorrhage were observed at necropsy but were not considered extensive enough to cause death. Rats survived exposiues to 5-72 ppm HDl (Haskell Laboratory 1961). In a similar study, groups of 4 male albino ChR-CD rats were exposed to 30 ppm HDl for 4 hours daily for 10 days over a 2-week period. 

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