In spite of the clarification of some significant physiological factors of visual fatigue caused by VDT work, pupillary reflexes have not been studied as to how they are affected after prolonged visual work. This study examined visual function changes objectively in terms of pupillary reflexes and lens accommodative responses after a 4-hr VDT operation task. The relationship between the two functions was also examined. Two measurements in this paper revealed the physiological function changes due to VDT operation. The subjects involved were five students with an average age of 22.6 years. First, near-reflex measurement ascertained decreases in amplitude and the velocity of accommodation function after the visual task. Second, light-reflex measurement revealed a delay of the reflex, an increase in the amplitude of the reflex, and a decrease in pupil size after the visual task. A weak correlation between the decrease in pupil size and accommodation function was found. The occurrence of visual fatigue due to 4-hr VDT operation was also confirmed by CFF measurements and reported subjective visual symptoms in this experiment.
Blood and urine samples from cloisonne ware workers were assayed for Pb, Cr, Cd, Mn, Sb, Co ad Cu for biological monitoring. Mean blood Pb levels were 47.8 ±27.3 μg/dl (111-13.3 μg/dl) for 49 cloisonne glaze workers, and 0.97 ± 0.47 pg/dl (2.4-0.6 μg/dl) for 62 normal subjects. There was a distinct difference between the 2 groups, and slight differences (p < 0.01) in mean Cr, Cd and Mn levels. There was a distinct difference in mean urinary Pb level between the 2 groups, and slight differences (p < 0.01) in mean Cr, Cd and Mn levels. The correlation coefficient, r, between blood Pb and Cd levels was 0.631 (p < 0.01) for 132 subjects consisting of cloisonne ware workers and normal subjects. r between blood Pb and blood Cr levels was 0.501 (p < 0.01), and that between blood and urinary Pb levels, 0.794 (p < 0.01). The above assays showed that glaze workers at cloisonne plants suffer severe exposure to lead and slight exposure to Cd and Cr.
Forty two male brick-field workers of two age groups, viz. 20-29 and 30-39 yrs were studied with a view to determine their aerobic capacity (VO2max). The average values of VO2max in l.min-1 showed only small change between the young and the aged groups, but the values of the V02max in ml.kg.-1min-1 showed significant difference between the groups due to body weight increase in the aged group. The aerobic capacity of the workers, engaged in heavy manual work such as puddlers and load carriers were found to be comparatively higher and a positive significant relationship has been established between the aerobic capacity and different occupations in the brick-field workers.
We developed a simple and reliable method for determining delta-aminolevulinic acid (ALA) in plasma (ALA-P) by fluorometric high-performance liquid chromatography. The method was applicable to 100 μl of plasma and the mean ± standard deviation for analytical recovery was 100.4 ± 2.6% when 50 pg/1 of ALA was added to 14 plasma samples. The detection limit for ALA-P was 2.0 μg/l (signal-to-noise ratio was 5) and the standard curve was linear in a wide range up to 400 μg/l. The ALA-P level for 26 unexposed male adults was 8.6 ± 1.3 μg/l. In 72 male lead workers, logarithm of ALA-P concentration was significantly correlated with blood lead concentrations (Pb-B) of 2.5-115.4 μg/dl (r = 0.924, p < 0.001). Even at the Pb-B level less than 15 pg/dl, significant linear relationships were found between Pb-B and log ALA-P (r = 0.632, p < 0.01), between Pb-B and delta-aminolevulinic acid dehydratase activity (ALA-D) (r =-0.573, p < 0.05), and between ALA-D and ALA-P (r =-0.765, p < 0.001). It is suggested that ALA-P determined by the present method is a useful indicator of biological effects of lead, es-pecially in the wide range of Pb-B level.
Chromosome aberration rates and sister chromatid exchange frequency were examined in the peripheral lymphocytes of 38 male workers who were engaged in organic glass production and exposed to methyl methacrylate (MMA) vapors at the con-centrations of 0.9 ppm to 71.9 ppm. The results were compared with the findings in the concurrent nonexposed male subjects. Comparison of the exposed group with the nonexposed controls showed that there were no exposure-related changes in chromosome aberration rate. SCE frequency was higher in the exposed group than in the controls, but this was considered to be due to higher ages of the former group than that of the latter. In fact, selection of nonsmokers and further classification of the exposed nonsmok-ers into two groups of those with exposure below and above a median MMA concentra-tion (ca. 4 ppm) failed to show any difference among the three nonsmoking groups in cytogenetic parameters, or any dose-dependency. The present results, although in a limited number of subjects, indicate that occupational methyl methacrylate exposure under the conditions studied is not associated with mutagenicity. This conclusion confirms the absence of mutagenicity of methyl methacrylate in humans, and is in general agreement with a majority of the results of studies on mutagenicity in vitro, animal carcinogenicity and occupational cancer epidemiology of methyl methacrylate.