The aim of this study was to determine whether the teratogenic effects of radiofrequency (RF) radiation are due to induced hyperthermia at 27.12 MHz. This was achieved by controlling the degree of temperature change and the duration of the elevation at this RF frequency. Pregnant Sprague-Dawley rats, at 9 days gestation were either sham-irradiated or irradiated with continuous shortwave radiation at 27.12 MHz. Rectal temperature, monitored by a thermistor probe was elevated by 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0°C for various durations. Sham-irradiation was associated with few resorptions, no malformations and a mean fetal weight of 3.7±0.60 g. Radiofrequency radiation induced fetal malformations (microphthalmia, encephalocele, facial clefting and maxillary hypoplasia) and embryolethality, the incidence increasing with the temperature elevation, while fetal weight decreased (+5.0°C = 2.5 ± 0.41 g). An elevation of 5.0°C for a few seconds was teratogenic, 4.5°C was teratogenic within 2 min ; 4.0°C-3 min, 3.5°C-15 min, 3.0°C-20 min and 2.5°C-60 min. These data are similar to those obtained by heating Sprague-Dawley rats on the same day of gestation in a water-bath1) indicating that the teratogenicity of RF radiation is primarily related to hyperthermia.
With self-completion questionnaires (with 67 questions in total), the prevalence of subjective symptoms was surveyed in 193 toluene-exposed and 65 non-exposed control women mostly at the ages of 20's. They were all nondrinkers-nonsmokers and therefore confounding effects of age, sex and the two social habits could be ruled out. The prevalence of total complaints per person correlated significantly with the time-weighted average intensity of exposure to toluene for each individual as monitored by diffusive sampling. Analyses with each symptom revealed that the prevalence of 43 symptoms (64%) out of the 67 in total was significantly higher in the exposed than in the controls. The dose dependent in-crease in prevalence was observed in 25 symptoms. In contrast, there was no difference in the prevalence of 3 hemodyscrasia-related symptoms between the exposed and the controls. The prevalence of several symptoms (e.g., body weight loss, dimmed vision, dizziness, drunken feeling, headache, sore throat, and tightness in chest) had a plateau in the exposure range below 100 ppm followed by an addi-tional increase at higher concentration, possibly justifying the current occupational exposure limit of 100 ppm, while some other symptoms gave different types of dose-prevalence relationship.
The interactions of trichloroethylene (TCEL) or tetrachloroethylene (perchloroethylene ; PCEL) with hypoxia and/or ethanol on the conduction system of the isolated perfused rat heart were investigated by recording the direct elec-trocardiogram (ECG). The coadministration of TCEL (0.05 mM), hypoxia (45% oxygen decrease), and ethanol (0.3%) produced the significant prolongation of atrioventricular conduction time (PQ interval) (p<0.01), whereas none of TCEL (0.05 mM) alone, hypoxia alone, ethanol alone, hypoxia with ethanol, TCEL with hypoxia, and TCEL with ethanol caused significant change in ECG findings. In TCEL of 0.1 mM, the coadministration with hypoxia and/or ethanol produced the significant prolongation of PQ interval (p<0.01). In PCEL of 0.1 mM, only when hypoxia and ethanol were coadministered simultaneously, PQ prolongation observed was significant (p<0.01). It is concluded that (1) TCEL and PCEL have the direct and local effect on the heart conduction system ; (2) the effect on the heart con-duction system is stronger in TCEL than in PCEL ; (3) hypoxia and ethanol synergistically enhance the effect of TCEL and PCEL on the atrioventricular conduction system at the observed concentrations.
Unsteady-state diffusion analysis was made to consider the response time of a diffusion sampler and the effect of exposure period on mass transfer. Response time of a diffusion sampler under unsteady-state is defined as the time at which the concentration profile in the diffusion zone becomes nearly equal to that under steady-state. And experiments on exposure to toluene vapor were executed by using three diffusion samplers that were on the market (Du Pont Pro-Tek G-AA, Drager ORSA 5 and 3 M MONITOR 3500). The agreement be-tween the theoretical and experimental results indicates that this model can be applied to these samplers and the concept of response time will be useful as the characteristic value when they are used under drastic conditions.
The blood pressure and electrocardiograms of 953 forestry workers using vibrating tools were investigated to study the chronic effect of noise and local vibration on the cardiovascular system. The mean systolic blood pressure of the workers was significantly higher than that of a comparable population. But there was no associations between blood pressure and the total operation time of chain saws. The bradycardia rate was 2-5 times higher in the subject popula-tion than in the general Japanese population. This was considered to be an adaptive response to an increase in oxygen demand while working in the forest. Though there were no results suggesting the relationship among noise, local vibra-tion and the cardiovascular system, operators with vibration-induced white fingers showed a significantly higher prevalence of atrial fibrillation than those without.
We have developed an instrument to measure blue-light radiation (BLR) that conforms to the recommendation of the American Conference of Governmental Industrial Hygienists (ACGIH). We used a luminance meter as a base. To remodel it into an instrument to measure BLR (BLR meter), we selected and combined suitable color glass filters and attached them to the aperture of the luminance meter. We describe the characteristics of the developed BLR meter and discuss its fitness for practical use. It was found that the BLR meter fully satisfies the conditions required for measurement of BLR and is sufficiently applicable for measurement in general in the workplace. Practically, with the BLR meter, we determined the BLR levels of the arc of shielded metal arc welding of mild steel and the sun nearly at noon on a fine day. They were 10.5 and 62.4 W/cm2-sr, respectively. Their permissible exposure dura-tions would be 9.5 and 1.6 seconds, according to the ACGIH.