The present investigation was designed to quantify noise exposure of laborers at various sections of an aluminum can production plant. The acoustic environment in each area was described by sound pressure level (SPL). Decibel (dB) readings were taken for a range of individual frequencies and weighting scales (A and C). Speech interference level (SIL) values for laborers in different production sections were also determined. Moreover, by means of a personal noise dosimetry technique, the equivalent continuous noise exposure level (dB(A)) during an 8-h shift (Leq, 8) was computed. The results obtained were as follows. Spectral analysis of the noise indicated that high SPL associated with high frequency noise exceeded the permissible limit against hearing damage, and it generally amounted to levels higher than 90 dB(A), whereas those inside the control rooms were in the range of 54-60.5 dB(A). Assessment of the results obtained from personal noise dosimeters also revealed that the Leq, 8 values were higher than the prescribed limit (85 dB(A)). By preliminary audiometric examinations on the right ears of workers, hearing threshold shifts (HTS) were noticed in the range of 7-11 dB at 1 kHz and 12-16 dB at 4 kHz. With regards to the SIL values (93.2-96.5 dB(A)) which were more than the maximum vocal effort, communication between workers and/or with supervisor were appraised to be very difficult (shouting) or impossible. It was concluded that (a) the dB readings observed in this survey indicate a potentially serious possibility of hearing disability, even though high level of HTS could not be noticed in the preliminary audiometric test, and (b) the risk of accidents should also be taken into account regarding the nonauditory effects of such a high level of noise. We suggest that (1) minimizing the transmission of noise through acoustical countermeasures need to be considered, and (2) introducing a schedule comprising on-time and off-time could be beneficial in a workers' health conservation program.
To recommend a comfortable visual display terminal (VDT) workstation design in an aspect of visual ergonomics, physiological resting states of the eye in 3 visual systems, pupil, vergence, and accommodation, were objectively investigated in 3 experiments. Exper-iment 1 ascertained a positive display polarity (dark characters on a bright background) and an illumination level of 500 lx to be the most appropriate working conditions, by using pupil analysis and subjective visual comfort in 10 subjects. Dark vergence, in experiment 2, was evaluated to be at a distance of about 50 cm from the eye, as an average in 14 subjects. Dark vergence was found to shift farther with an upward gaze while a nearer shift occurred with a downward gaze. In experiment 3, the average dark focus for 11 subjects was found to be 1.4 diopters (D) or a distance of about 74 cm from the eye. The positive correlation between refractive status of the eye and dark focus was statistically significant (r= 0.602). The ergonomic recommendations for a VDT workstation obtained in this study are a positive display polarity with an appropriate lighting condition, a downward gaze, and a viewing distance between 50 and 70 cm. These recommendations are considered to reduce visual fatigue due to prolonged VDT work and to facilitate visual comfort at work.
Polyaminocarboxylic acids have widely been used as antidotes in heavy metal intoxication, however their hydrophilic nature renders them to be mostly distributed extra-cellularly. To facilitate the intracellular delivery of such chelating agent, triethlene-tetraamine-hexaacetic acid (TTHA) was encapsulated in small unilamellar vesicles (SUV) or dehydration rehydration vesicles (DRV) and its effect was examined in the amelioration of cadmium toxicity. Mice were administered cadmium (0.2 mg/kg B.wt.) as CdCl2 in-traperitoneally daily for five days. After a period of four weeks rest. they were given two intravenous injections of TTHA as free material or encapsulated in liposomes (0.16 m mole/kg) at a gap of 48 hours. Urinary and fecal elimination of cadmium and its distribution in the liver, kidney and spleen was monitored after TTHA treatment. The results indicate the efficacy of TTHA in removing cadmium from the body organs of preexposed animals and its excretion through urine and feces was maximum when it was encapsulated in SUV liposomes.
The effects of 60 dB (A) steady pink noise on sleep induction were studied. Two experiments were conducted. First, 10 night-sleep polygrams of a young male subject were recorded consecutively as controls. Five night polygrams of the same subject were then recorded with exposure to steady 60 dB (A) pink noise. Second, polygrams of four students were recorded using the same noise exposure as in the first experiment. Polygrams for the control night were also recorded. Noise exposure tended to shorten sleep latency, i.e., the values were 4.2 and 9.5 min in the first and second experiment, respectively. The steady 60 dB (A) noise made sleep induction easier.