A vibration level meter has recently been used for evaluation of environmental vibrations, which has a frequency weighting circuit corresponding to human vibration sensation and an indication part with two dynamic characteristics of "slow" and "fast". Values measured with this meter is shown as dBVL. There are still problems in evaluation of non-stationary or impulsive vibrations by this meter. Using this vibration level meter, difference between values observed by fast and slow characteristics was examined on 13 sample environmental vibrations with station-ary, non-stationary and impulsive wave forms. On the same vibrations, equal sensa-tion was observed on 10 subjects by comparing one of them with sinusoidal vibration at standard frequency individually. It was endorsed from these physical and subjective experiments that VL value at 50% on ogive determined by statistical analysis was reasonable for evaluation of the non-stationary vibration, and peak VL value was better for evaluation of the im-pulsive vibration. Besides, it was recognized that slow characteristic was suitable for vibration measurement from the standpoint of reliability of measured value.
Influence of sensation of noise on that of vibration was examined in order to search for perceptional interaction of sound and vibration. Under the condition that noise of diesel pile driver (P noise) was applied, perception of vibration of diesel pile driver (PV) was compared with that of the same PV or sinusoidal vibration to obtain equal sensation by a subject sitting on a vibration table. The level of compared PV judged as equal sensation was called equivalent level. It was found that difference between equivalent level and applied level of PV was not so large and it was within 2 dB even at the noise level of 100 dBA. This difference might come partly from masking effect of noise and partly from difficulty of subjective judgement due to application of noise.
In order to determine a criterion of VL value of a vibration level meter used for the measurement of environmental vibrations, experiments for long time exposure from 2 to 4 hr to vibrations was carried out on ten subjects. Vibrations of a diesel pile driver and a forklift were adopted as the sample vibrations. Response to these vibrations were studied on several psychological and physiological parameters. Changes in such parameters as sequent subjective judgement, equivalent level and threshold shift were found significant in relation to exposure time, though it was somewhat difficult to estimate the criterion of VL value from the interrelation between these parameters. The criterion of VL value was estimated from the subjective judgement alone as follows: 95 dBVL to 3 hr, 100 dBVL to 1.5 hr and 103 dBVL to 1 hr to be permitted for exposure. These levels showed perception lying between unpleasant and slightly unpleasant feeling in a five grade judgement and agreed with the criterion curves of fatigue decreased proficiency boundary (FDP) proposed in DIS-2631 of ISO/TC 108/SC 4.
A survey was made among the workers of 17 workshops and two factories of tile manufacturing plants for any probable lead intoxication due to the use of lead in the glaze. The comparison was made by the determination of lead and coproporphyrin in the urine and hemoglobine, basophylic stippled cells in the blood of both groups as well as in the control. Due to the use of prefabricated glazing material and automation of the process and absence of lead fumes and dusts, no cases of intoxication was observed among the workers of factories while several cases of higher values of lead in urine, presence of coproporphyrin, stippled cells and decrease of hemoglobine contents were noted in workers of workshops where metalic lead was molten and used in glaze under un-favourable conditions.
Intravenous infusion of CaEDTA was given to 45 Japanese adults without occupa-tional exposure to lead for 1 hr in a dosage of 20 mg/kg body weight in 250 ml of 5% glucose solution. The urinary excretion of lead was estimated for 24 hr before, and for 2 hr and 24 hr after the administration. The least variation of the lead content was recognized in the 24 hr urinary excretion after the injection of CaEDTA. No sexual difference was noted in the creatinine-corrected lead concentration. By multiple linear regression and correlation analyses, age was found to be sig-nificant in determining positively the lead level mobilized in 24 hr urine samples. Height was significant in determining positively the spontaneous 24 hr urinary lead excretion. Certain significant correlations existed among lead in blood, ALA-D in erythrocyte, δ-ALA in urine, coproporphyrin in urine, lead in urine and lead mobilized by CaEDTA. The existence of "active" body burden of lead was suggested in human subjects under usual urban condition where the total ambient lead averaged 1.7 μg/m3 of air. Based on a few assumptions, it was calculated that about 3 μg of lead was retained on average per day by a Japanese adult; daily retention of lead by Japanese adults was formularized, i.e., Pb (μg)=K×daily creatinine excretion (g), where K is 1.77 in men and 2.73, women.
X-ray diffraction is used as an analytical tool for crystalline substances which are hazards in an occupational and natural environments. This paper describes a method for qualitative and quantitative determination of asbestos in airborne dust in the occupational environment. Airborne asbestos collected on glass fiber filter by means of high volume air sampler can be analyzed without removal of the dust from the filter and also without addition of internal standard material. For determination of amounts of total dust, the filter is weighed before and after the collection of the sample. For estimation of mass per unit volume of air, the total volume of air that passed through the filter is recorded. In order to obtain asbestos content in airborne particulates, two types of X-ray generators are used in this study. One is equipped with conventional sealed anode X-ray tube. It is applicable to determine quantita-tively 1 to 5 mg of asbestos with this method. The other is equipped with rotating anode X-ray tube in order to generate high power X-ray. This procedure can be carried out routinely in a laboratory and in occupational environment when the total amount of sample is of the order of 0.01 mg of glass fiber filter of 3.8 cm2 in area. The results of field survey indicate very high concentration of both asbestos and total dust in working area of asbestos industry, especially of sprayed mineral fiber containing asbestos.