This experimental study aimed at acquiring detailed data about the human transmission behaviour as a basis for an improved estimation of the strain, induced by whole body vibration (wbv). Four male subjects were exposed to verti-cal sinusoidal wbv (2-12 Hz; 1.5 and 3.0 ms-2 RMS). The steady state force re-sponse was measured at the input interface, and accelerations were registered at the seat, head, shoulder, and upper trunk. Transmissibilities and apparent mass as quotients of RMS-values were determined. In addition, the corresponding quotients of peak values, as well as their accompanying phase angles were calculated separately for maximum acceleration or minimal acceleration, and for the extreme values of apparent mass in relation to the body mass. The resonance frequencies were lower at higher intensity levels. Near the resonance of the whole body, the quotients for maximum accelerations were significantly higher than those for minimal accelerations, and the shapes of time histories of the output deviated clearly from those of the sinusoidal input. The results speak in favour of a pronounced nonlinearity of human biodynamics even at low acceleration levels, the system properties depending on the input pa-rameters. These factssuggest a higher strain of biological structures than that predicted by RMS-values assuming linearity.
In one of two experiments which were previously carried out in male students, 24 female students performed four mental tasks (transcribing, cancelling, adding, and calculating) at maximum effort for 5 min each. On the basis of an objective mental worklord index, i. e., occipital midline beta-2 (Ozβ2) amplitude, it was shown that all tasks caused a higher mental workload in females than males, though there were no sex differences in Ozβ2 amplitude at rest. On a subjective mental workload index, i. e., subjective rating of task difficulty (SRTD), however, it was suggested that females had a tendency to perceive a lower mental workload in all tasks than males. In another experiment, where a paced calculating task was imposed on another 24 female students at five grades of task load for 5 min each, the critical values for excessive workload were estimated to be about 7.0 μV (the difference between the levels at work and at rest) for Ozβ2 amplitude and 3.5 for SRTD. Hence, it was evaluated that none of the above four tasks constituted an objectively exces-sive workload in females, whereas all of them were excessive in males. Subjec-tively, two tasks that were seen as an excessive workload in females were not in males.
Using a high-performance liquid chromatograph, erythrocyte pyrimidine 5'-nucleotidase (P5N) tests were performed in normal controls and lead workers. The erythrocyte P5N was very stable even if whole blood was stored at 4°C for one week. In 77 lead-exposed workers, the erythrocyte P5N activity was markedly inhibited by lead and the log of the P5N activity was closely correlated with the blood lead (r=-0.85). When the response of the P5N activity to blood lead was compared with that of various parameters (erythrocyte ALA-D, erythrocyte protoporphyrin, urinary δ-aminolevulinic acid, and urinary coproporphyrin) related to porphyrin metabolism, the P5N activity was found to have the highest response to lead among these parameters. These findings indicate that the P5N test represents one of the most reliable indicators for evaluating levels of occupational lead exposure.
Among the 7 types of natural solvent mixtures listed as third class solvents in the Ordinance on Prevention of Organic Solvent Poisoning, 5 types (134 samples) of petroleum distillate solvents (PDS) were collected from various parts of Japan in 1986 and 1987, and analyzed for n-hexane, benzene and 4 other aromatics by capillary gaschromatography. In addition, 3 samples of turpentine oil, 1 sample of reagent grade coal tar naphtha, 14 samples of JIS solvent gasoline of various sorts and 4 samples of drug store-bought spot remover were analyzed for reference. The mean concentrations of n-hexane and benzene in total PDS samples were 2.57% and 0.41%, respectively, but the concentrations of the 7 chemi-cals studied dispersed over very wide ranges and it was not possible to identify typical compositions even after the results were grouped according to use patterns. From chromatograms, it was possible to classify the PDS into two groups of "low" and "high" boiling point PDS, with higher risk for the former to contain n-hexane and benzene. All rubber surface softener samples examined belonged to the former, whereas all dry-cleaning solvents to the latter. Thinner-cleaner samples for print-ing and painting distributed in two groups evenly. Turpentine oil and coal tar naphtha samples analyzed contained no n-hexane nor benbene at all. Both n-hexane and benzene (up to 13.7 and 4.2%, respectively) were detected in spot re-movers.