To investigate the importance of the cadmium (Cd) exposure condition in the evaluation of toxic effect on renal function and bone metabolism, six groups of Male Wistar rats were given Cd at respective daily doses of 2, 5, 10, 20, 30 and 60 mgCd/kg (as CdCl₂) via a gastric tube for 6 consecutive days a week for 60 weeks. In the groups given a low Cd dose (2, 5 and 10 mgCd/kg), relatively more Cd accumulated in the kidney without liver damage than in the liver. In the high Cd dose groups (20, 30 and 60 mgCd/kg), on the other hand, more Cd accumulated in the liver than in the kidney. The daily intake of Cd dose from the intestinal tract in each experimental group was deduced to be about 0.36%-0.54% of the cumulative dose of oral Cd administration. The daily intake of Cd into the body was estimated as 7, 22, 40, 100, 120, 260 μgCd/kg/day in the experimental groups of 2, 5, 10, 20, 30 and 60 mgCd/kg/day, respectively. Increase of plasma enzyme activity (GOT, GPT) and of urinary enzyme excretion (NAG, AAP, GST), reflecting hepatic damage and renal dysfunction, was found in the high Cd dose groups (30 and 60 mgCd/kg) from the 5th week. Non-CdMT concentration in the kidney was also significantly high in the high Cd dose groups. In the low Cd dose groups (2 and 5 mgCd/kg), although the renal Cd concentration was higher than that of the high Cd dose groups, prominent renal dysfunction and hepatic damage were not observed. Regeneration, vacuolization, and eosinophilic bodies in proximal tubular tissue were mainly observed in the groups subjected to 20, 30 and 60 mgCd/kg administration. Very slight regeneration was also observed in the renal proximal tubular tissue at the 30th week for the 5 mgCd/kg and 10 mgCd/kg groups, and at the 60th week for the 2 mgCd/kg group. Remarkable decrease of bone mineral density at the midpoint of the femur was found in the high Cd dose groups. Also, the decrease in bone mineral density was observed before or after the manifestation of the renal dysfunction, depending on the dose and the duration of Cd administration. Urinary excretion of Pyr, DPyr, and Ca increased and plasma BGP decreased in the higher Cd dose groups. Osteoid volume in the femur tissue was not increased significantly by Cd exposure. Based on these results, it was suggested that Cd exposure caused osteoporotic change. The results of the present study suggested that the toxic effect of Cd on renal function and that on bone metabolism were caused at different times and that renal Cd concentration after long-term oral Cd administration depended on the dose and the duration of Cd exposure.

View full abstract

In order to improve arc welding work in a small enclosed workspace, numerical simulations were conducted to find the most appropriate welding and ventilation conditions, such as welding currents, hood position and flow rates with no blowhole formation. In the simulations, distributions of airflow vectors and fume concentrations were calculated for two hood opening positions: one faced a welder's breathing zone, the other a contaminant source. As a result it was predicted that a hood opening facing a breathing zone remarkably lowered the fume concentration in the breathing zone compared with that facing a contaminant source. The reliability was confirmed in CO₂ arc welding experiments in the enclosed workspace by using a welding robot. In addition, the number of blowholes in welds, examined with x-ray, decreased with the increase in the welding current and with the decrease in the exhaust flow rate. These results showed that the fume concentration near welder's breathing zone and the number of blowholes could be reduced effectively by appropriate selection of the welding current and hood position, and it was confirmed that the numerical simulations were sufficiently useful to predict these appropriate welding conditions.

View full abstract

The aim of the present study was to investigate whether thermal perception threshold testing is a useful method that could replace pain threshold testing in the evaluation of small sensory nerve fiber injury in vibration-induced neuropathy. Vibration, pain, and thermal (warm and cold) perception thresholds were examined on both middle fingers of 50 patients with hand-arm vibration syndrome and 29 healthy controls of similar age. The patients were divided into three subgroups according to the Stockholm Workshop sensorineural scale. Thermal (warm and cold) thresholds as well as vibration and pain thresholds were significantly more deteriorated among the patients than in the controls. Among the patients, warm thresholds elevated and cold thresholds lowered according to the Stockholm Workshop scale. Thermal thresholds were significantly correlated with pain thresholds, and the sensitivity of the thermal threshold testing tended to be greater than that of the pain threshold testing. The present findings indicate that thermal threshold testing for warm and cold perception can be a useful substitute for pain threshold testing to examine small nerve fiber injury in vibration-induced neuropathy.

View full abstract

To establish the relationship between Zinc protoporphyrin (ZPP) concentrations and blood lead (PbB) levels and to identify reliable analytical methods of ZPP and Protoporhyrin (PP), blood samples were obtained from 263 office workers without the history of occupational lead exposure and 49 lead-acid battery workers. The mean concentrations of PbB for the normal adults and the battery workers were 9.26 μg/dl and 42.60 μg/dl, respectively. The geometric mean concentrations of ZPP and PP by HPLC were 18.73 μg/dl and 2.27 μg/dl for normal adults and were 46.99 μg/dl and 5.53 μg/dl for the exposed workers, respectively. The geometric mean concentrations of ZPP and PP by a spectrofluorometer (SF) were 30.27 μg/dl and 5.16 μg/dl for normal adults and were 50.91 μg/dl and 6.69 ± 1.39 μg/dl for the exposed workers. The geometric mean ZPP concentration measured by a hematofluorometer (HF) was 30.88 μg/dl for normal adults. The results showed that ZPP concentrations measured by HF were consistently higher than those by HPLC and SF for normal adults, and lower for the exposed workers. ZPP concentrations were not correlated with PbB levels for normal adults but a statistically significant correlation was found among the exposed workers.

View full abstract

A respirator filter of good quality has not only high aerosol collection efficiency but also low air resistance. “Quality factor”. which is expressed with aerosol penetration and pressure drop, can be used to rank the performance of respirator filters within the same category. This study focuses on evaluating several respirator filters which are widely used in Korea using quality factor. Two mechanical filters and three filtering facepieces made by different manufacturers were measured aerosol penetrations and pressure drops by an automatic filter tester (CertiTest Model 8110, TSI Inc., St. Paul, USA) at four flow rates of 10, 32, 64 and 85 L/min. NaCl aerosols used were reported to be mean size of 0.1 μm and geometric standard deviation of <1.9. The penetrations and pressure drops of all filters have strong flow rate dependency. The filter quality factors decrease sharply as flow rates are increased. The mechanical filter S and filtering facepiece M are shown better filter quality than others in the same category. Since some certified filters are found to be inappropriate in the workplace exposed to fume, this result suggests that the current certified filter test protocol for respirators should be changed for the new protocol using smaller aerosols.

View full abstract

To determine relatively useful diagnostic procedures of carbon disulfide (CS₂) poisoning in terms of validity and cost-effectiveness, several diagnostic tests are evaluated on 1, 552 people by prevalence ratio (exposed/nonexposed), dose-response relationship, sensitivity and specificity, and the cost of the tests. Several symptoms with high kappa indices are found to be useful in various combinations, showing a consistent dose-response relationship and high exposed-nonexposed ratio. In clinicopathologic tests on functions of the kidney, liver and hematopoietic systems, eight items out of 22 have been shown to have significant dose-response relationship, mostly in liver function tests. A thorough dental examination failed to identify any useful indicator peculiar to the CS₂ poisoning. Unlike Western people, the prevalence of coronary heart disease among Koreans was too low to be useful in the diagnosis of CS₂ poisoning. Among four elective tests, i.e., Minnesota Multiphasic Personality Inventory (MMPI), Brain magnetic resonance imaging (MRI), nerve conduction velocity (NCV), and fluorescent angiography (FAG), the NCV appeared to be a more sensitive and specific test than the others are. Combinations of the tests imporved the probability of diagnosing CS₂ poisoning cases when any one test out of four was positive. Addition of other valid tests increased the probability of excluding non-cases. It was concluded that diagnosis of CS₂ poisoning could be made validly and inexpensively if the diagnostic tests were carefully chosen step by step.

View full abstract

In Japan, the prevalence of smoking among males and females was 56.1% and 14.2%, respectively, in 1997. Male smoking prevalence was exceedingly high as compared to those in other industrialized countries. We conducted a randomized controlled intervention study on smoking cessation for all smokers in a worksite regardless of their willingness to quit smoking. All of the male smokers in a radiator manufacturing factory (n=263) were randomly allocated to an intervention group (n=132) or a control group (n=131). Subjects in the intervention group received individual counseling by a doctor, and those who signed a Smoking Cessation Declaration underwent a fivemonth intervention. Subjects in the control group received equivalent delayed intervention for four months. The cessation rate after the original intervention was 12.9% (17/132) and 3.1% (4/131) in the intervention and control groups, respectively (p=0.003). Among those who once succeeded in quitting, 48.6% (18/37) maintained cessation at the long-term survey. Overall, the cessation rate was 8.4% (22/263) and the prevalence of smoking among males significantly decreased from 62.9 to 56.7% (p=0.038). As a conclusion, intervention in all smokers at a worksite regardless of their willingness to quit is effective and impacts the overall smoking rate.

View full abstract

Wistar male rats were repeatedly exposed to methanol and toluene vapors individually and simultaneously by inhalation 6 hours a day, five days a week for 4 weeks. Blood was obtained from the tail of the rats up to 23 hours after the end of 4-week exposure and the methanol and toluene concentrations were measured. Major metabolites of methanol and toluene, that is, formic acid and hippuric acid in urine were measured up to 6 days after the end of 4-week exposure. The biological half time of toluene in blood in the simultaneous exposure group was shorter than that in the toluene exposure group. This tendency was almost the same as that for one-day exposure, although the biological half time of solvents in the rat blood was prolonged. The half times of methanol were also longer than those for one-day exposure.

View full abstract

In this study an attempt has been made to examine the efficacy of meso-2, 3-dimercaptosuccinic acid (DMSA) using galactosylated liposomes as carriers for mobilization of cadmium from the body of mice preexposed to cadmium chloride (0.005 mmoles/kg intraperitoneally daily for 4 days). Cadmium-exposed mice after a rest period of 8 weeks were administered DMSA intravenously, two injections 15 μmoles/kg with an interval of 48 h, as free form of DMSA, or DMSA encapsulated in liposomes composed of phosphatidyl choline, cholesterol and phosphatidyl ethanolamine (7:2:1; PC-lip-DMSA) or in liopsomes to which p-aminophenyl galactoside had been anchored (Gal-lip-DMSA). Excretion of cadmium through urine and feces was monitored for 5 days. Thereafter animals were sacrified, liver, kidneys, spleen and isolated hepatocytes were analysed for cadmium, copper and zinc concentration. Efficacy for cadmium mobilization from the body was found to be in the order Gal-lip-DMSA>PC-lip-DMSA>DMSA. These results show that liposomes can be used as targeted carrier system for chelating agents safely and efficiently as compared to administration of free chelating agent.

View full abstract

We carried out the study to assess, using field surveys and personal dosimetry, the potential exposure of pharmacists and pharmaceutical assistants to 60 Hz magnetic fields in a medical center of Taiwan. Field surveys were conducted twice in the pharmacy where two workers were randomly selected and solicited to wear personal dosimetry instruments for a full-shift assessment of personal exposure. We used an EMDEX II for on site measurements and did not consider any specific instrument or equipment for health care services as potential sources of magnetic field. The results showed that the average magnetic flux densities for the selected areas were between 0.63 mill-Gauss (mG) and 2.23 mG, while the full-shift time-weighted-average exposure for the two selected workers was 4.98 mG and 6.54 mG, respectively. Both inadequate consideration for the field survey of the temporal variability in magnetic flux densities over the workday and that the monitored workers spent almost half of the full-shift working in places outside of the study areas may have contributed to such discrepancy in results between field survey and personal dosimetry. This study suggests that the potential for elevated exposure to 60 Hz magnetic fields in health care settings does exist, and that using job title as a surrogate for magnetic fields exposure classification might entail certain degrees of misclassification. Although limited in its scope and sample size, the study presented here seems to demonstrate the inadequacy of using stationary workplace measurements for the assessment of personal occupational exposure to 60 Hz magnetic fields.

View full abstract

In the 1980's, the visual display terminal (VDT) was introduced in workplaces of many countries. Soon thereafter, an upsurge in reported cases of related health problems, such as musculoskeletal disorders and eyestrain, was seen. Recently, the flat panel display or notebook personal computer (PC) became the most remarkable feature in modern workplaces with VDTs and even in homes. A proactive approach must be taken to avert foreseeable ergonomic and occupational health problems from the use of this new technology. Because of its distinct physical and optical characteristics, the ergonomic requirements for notebook PCs in terms of machine layout, workstation design, lighting conditions, among others, should be different from the CRT-based computers. The Japan Ergonomics Society (JES) technical committee came up with a set of guidelines for notebook PC use following exploratory discussions that dwelt on its ergonomic aspects. To keep in stride with this development, the Technical Committee on Human-Computer Interaction under the auspices of the International Ergonomics Association worked towards the international issuance of the guidelines. This paper unveils the result of this collaborative effort.

View full abstract