Log-Normality of Air Contaminants and Its Hidden Characteristics Useful for Industrial Hygiene Technology: Akio KOIZUMI, et al. Department of Health and Environmental Sciences, School of Public Health, Kyoto University-It is well known that concentrations of contaminants in the air fluctuate log-normally, but there has been no mathematical model that can describe the stochastic nature of this. In the present study we constructed a stochastic model that can describe log-normal distribution of the air contaminantion in workplaces. The so-called Ito-process can describe the log-normality of the stochastic nature of the air contaminants by using two parameters: ventilation performance and random release of contaminants from the source. We also derived a theorem from the model. It indicates that splitting the source into small independent compartments decreases randomness and thereby reduces exposure intensity. The reduction of randomness of contaminant release is considered to be as effective as improvement of ventilation performance in reducing workers'' exposure.

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Stability of Factor Structure and Correlation with Perceived Job Stress in General Health Questionnaire: a Three-wave Survey over One Year in Japanese Workers: Jun SHIGEMI, et al. Department of Hygiene and Preventive Medicine, Okayama University Medical School-A cross-sectional study was conducted to examine psychological symptoms and job stress in Japanese workers. To assess the stability of the relationship between the parameters for perceived job stress and mental health, two additional surveys were carried out six months and one year later. The surveys included demographic questions, the General Health Questionnaire (GHQ), and questions relating to perceived job stress to measure the worker''s mental health and job stress. Factor analyses were conducted to clarify the factor structure of mental health. As for the GHQ, the 6 dominant factors were interpreted. These factors involved “Anxiety and depression”, “Severe depression”, “Lack of interpersonal network or social support”, “Poor social activity”, “Insomnia”, and “Lack of a positive attitude”. This structure was stable in the 2 follow up surveys. A multiple regression analysis was used to examine the relationship between extracted factors of the GHQ and job stress. The analysis showed that the factor “Anxiety and depression” had a significantly stable relationship with “Too much responsibility at work” and “Cannot keep up with new technology”.

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A Cohort Study on Raynaud''s Phenomenon in Workers Exposed to Low Level Hand-Arm Vibration: Kotaro TOMIDA, et al. Department of Hygiene, School of Medicine, Wakayama Medical University-To clarify the incidence of Raynaud''s phenomenon among workers exposed to low level hand-arm vibration for a long time, a sample cohort of workers mainly operating a bush cleaner (the vibration level was 2-4 m/s²rms) were followed up for a period of 20 yr. The sample cohort consisted of 331 male workers mainly working at maintaining public roads or afforesting and gardening on a farm. The examination was based on questionnaires used in special medical examinations for vibration syndrome from 1977 to 1996. Raynaud''s phenomenon was observed in 11 subjects. The accumulative occurrence rate increased linearly in the case of more than 11 operating years. The mean number of operating years at the occurrence of Raynaud''s phenomenon was 11.7 ± 7.1 yr. The mean total operating time at the occurrence of Raynaud''s phenomenon was 3, 756 h on the geometric average. Stockholm Workshop scale classified 1 subject as Stage 1 (mild), 4 subjects Stage 2 (moderate) and 6 subjects Stage 3 (severe). By the person-year method, the incidence of Raynaud''s phenomenon was 4.48 per 1000 person-year. These findings show that the number of operating years for a bush cleaner should be considered to prevent Raynaud''s phenomenon, even though the hand-arm vibration level is low.

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An Integrated Approach to Initiate Preventive Strategies for Workers Exposed to Teflon Pyrolytic Gases in a Plastic Industry: PerngJy TsAl, et al. Department of Environmental and Occupational Health, Medical College, National Chen Kun UniversitThis study illustrates an integrated approach for industries to find possible hazardous factors, to identify the causes of an accident, and eventually to start preventive measures after a fatal accident occurred in a Teflon heating process. A team consisting of experts from several disciplinary areas was formed for the purpose. Through literature review and the examination of clinical reports, possible hazardous factors were proposed, and then examined and confirmed through a field study. The technique of fault tree analysis (FTA) was adopted to investigate the causes of the accident logistically. Investigation of the causes of the accident was not limited to those which were directly relevant to it, but all potential causes were included. A preventive strategy was proposed with prioritized measures which were determined based on their importance from the practical standpoint. This study demonstrates the benefits of integrating expertise from a number of disciplines for accident investigation, especially for those accidents in which the scenario cannot be reconstructed.

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The Effects of Job-Related Factors and Lifestyle on the Five-Year Cumulative Incidence of Hypertension in Japanese Steelworkers: Yasushi OKUBO, et al. Department of Hygiene, School of Medicine, Chiba University-We conducted this epidemiological follow-up study from 1990 to 1995 to clarify the effects of job-related factors and/or lifestyle on the five-year cumulative incidence of hypertension in Japanese normotensive steelworkers. The subjects were normotensive 3, 061 males aged 40-54 yr, and 2, 249 subjects were followed-up completely. Job-related factors (job class, job type and promotion), lifestyle (salt intake, calorie intake, habitual exercise, alcohol consumption and smoking habit) and six subjective symptoms which were thought to be related to mental health were evaluated in relationship to the five-year cumulative incidence of hypertension. The results of the multiple logistic regression analysis indicated that age, mean blood pressure in 1990, and promotion during the five-year period were factors significantly related to hypertension. Odds ratios of age (per 1 year old), mean blood pressure (per 1 mmHg) were 1.08 and 1.19, respectively. Odds ratio of promoted workers to non-promoted workers was 0.56. Promotion was related independently to the five-year cumulative incidence of hypertension. No relationship between hypertension and other job-related factors, blood findings or subjective symptoms was noted. In conclusion, our study suggested that age and mean blood pressure strongly influence the five-year cumulative incidence of hypertension, and promotion reduced the risk of hypertension in male workers.

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Strength and Perceived Exertion in Isometric and Dynamic Lifting with Three Different Hand Locations: Shoko ANDO, et al. Nagoya University School of Health Sciences-The dynamic and isometric strength and physical stress in symmetric and asymmetric lifting were measured with some common pairs of hand locations and a pair of clearly defined foot positions. In the experiment, eleven healthy male students were required to lift a small box attached to the arm of a dynamometer. The size of the box was 29 cm long, 24.5 cm wide and 23 cm high, and it weighed 10 kg. Both hands were located at three different positions on the box; the two handles near the upper edges of the box gripped with the hands (Handle type), the bottom on either side (Bottom type), and the left lower proximal corner and the right upper distal corner (Oblique type). The dynamic and isometric forces at the three hand locations were significantly different, and the least values were observed in the Oblique type irrespective of the lifting angle. Perceived exertions on the category scale (CR-10) for the left arm were very high in Oblique type lifting with any combination of height and symmetry during dynamic lifting. Therefore the burden of Oblique type lifting was thought to be greater than in the other two types of lifting, if workers are ordered to handle a box in otherwise identical conditions. In dynamic lifting Handle type lifting was thought to be the best among the three types.

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A Linear Pharmacokinetic Model Predicts Usefulness of N-Methyl-2-Pyrrolidone (NMP) in Plasma or Urine as a Biomarker for Biological Monitoring for NMP Exposure: Xiaofei E, et al. Department of Hygiene, Akita University School of Medicine-N-methyl-2-pyrrolidone (NMP: C₅H₉NO:CAS number 872-50-4) is an increasingly used solvent due to the lack of ozone depleting activity. The aim of this study is to construct a simple pharmacokinetic model for NMP. In factory A, four workers who were exposed to NMP at 0.09-0.69 ppm for 12 h by time weighted average (TWA) were followed up for an entire workweek. Their NMP concentrations in plasma and urine were monitored during the observation period. Five volunteers were exposed to NMP during the observation of workers in the factory A for eight hours. NMP kinetics in plasma and urine were monitored for 2 d after exposure. Concentrations of NMP in plasma and urine as standardized by creatinine concentrations were used to construct a one compartment pharmacokinetic model. The model successfully simulated the kinetics in four workers and five volunteers. In the next step, the model was applied to eight workers in another factory: they were exposed to NMP for 12 h at 0.04 to 0.59 ppm by TWA. The model could successfully predict kinetics of NMP levels in plasma and urine at the end of work. The model was then applied to experimental exposure cases in the literature. The model successfully predicted the concentrations of NMP in plasma and urine at the exposure intensity level of 12 ppm × 8 h. These results imply that metabolic saturation does not occur up to the exposure intensity of 12 ppm × 8 h and demonstrate the usefulness of determinations of NMP in plasma and urine for biological monitoring.

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Neurophysiological Changes in Rats Subchronically Treated with Styrene or Its Metabolites: Junichi MlsuMl, et al. Department of Public Health and Hygiene, Oita Medical University-The purpose of this study was to clarify the causative agent(s) in the peripheral neuropathy induced by styrene. Styrene 600 or 300, and its metabolites; hippuric acid 600 or 300; mandelic acid 300; styrene oxide 100; mg/kg were subcutaneously injected into rats for 10 to 12 wk. The changes in maximum sensory conduction velocity (SCV), maximum motor conduction velocity (MCV), and motor distal latency (DL) in the rat''s tail nerve were tested. Compared with the control group, decreases in MCV, SCV, and an increase in DL were observed in the rats injected with styrene 600, styrene oxide 100 and mandelic acid 300 mg/kg. No significant changes were found in the rats treated with hippuric acid 300 or 600 mg/kg. The MCV and SCV values in the styrene oxide 100 and mandelic acid 300 mg/kg groups were significantly lower, and DL values were significantly longer than those in the styrene 600 mg/kg group. It is presumed that the neuropathy caused by styrene is related to the neurotoxicity of its intermediate metabolites, namely mandelic acid and styrene oxide. It appears that the neurotoxicity of mandelic acid needs to be further evaluated in styrene-produced neuropathy.

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Prevalence of Hepatitis B Virus Infection in a Population Exposed to Biological Risk: Andrea TREVISAN, et al. Department of Environmental Medicine and Public Health, University of Padova-The prevalence of hepatitis B virus infection was investigated in 1, 221 subjects (809 exposed to different degrees of biological risk and 412 presumably not exposed personnel) employed in Padua University. The population was subdivided in four groups according to no, low and occasional, intermediate, even though continuous, and high exposure to biological risk. A past history of hepatitis B virus infection was detected in 10.0% of subjects (8.8% had positive hepatitis B antibodies, 1.1% positive hepatitis B surface antigens and 0.2% positive hepatitis B enveloped antigen). Seroprevalence of positive hepatitis B antibodies increased with age (p<0.001) but was not related with sex. No significantly high prevalence of hepatitis B virus infection was found among the groups, but excluding vaccinated subjects (333, 27.3%), the prevalence was significantly higher in intermediate (p<0.025) and the high (p<0.001) risk groups when compared with the other two groups, other than in high compared with the intermediate risk group (p<0.05). The results show low prevalence (10.0%) of hepatitis B virus infection in the examined population, but increasing according to the risk extent.

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