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The Effect of Lung Burden on Biopersistence and Pulmonary Effects in Rats Exposed to Potassium Octatitanate Whiskers by Inhalation: Takako OYABU, et al. Institute of IndustrialEcological Sciences, University of Occupational and Environmental Health, Japan-The effect of lung burden on biopersistence and histopathological changes caused by potassium octatitanate whiskers (POW) which is one of the asbestos substitutes were investigated for 1-yr and 4-wk inhalation periods. In the 1-yr inhalation experiment, male Wistar rats were exposed to POW (TW) for 6 h/d, 5 d/wk under the same conditions as a previous study of POW (PT1, JFM fiber) which is made by different manufacturer. The exposure concentration was 1.9 ± 0.7 mg/m 3 and the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) in the chamber were 1.6 µm and 2.9. Rats were sacrificed at 3 d and 1 yr after the inhalation experiment and TW deposits in the lungs were determined by ICP-AES. Lung burden at 3 d and 1 yr after the inhalation was 2.39 ± 0.50 mg and 1.37 ± 0.96 mg, respectively, the deposition fraction was 8.1% and biological half time (BHT) was 15 months. Aggregated dust cells and mild fibrotic changes around these dust cells were observed in the exposed rat lung. These results were almost the same as those obtained in the previous 1-yr PT1 study. In the 4-wk inhalation experiment, to investigate the effect of lung burden on biopersistence and histopathological change, male Wistar rats were exposed to PT1. The exposure Occupational and Environmental Health, Japan, Yahatanishi, concentration was 102 ± 21 mg/m 3 , MMAD (GSD), the geometiric mean length and diameter (GSD) of the PT1 in the chamber were 1.6 µm (3.0), 2.2 µm (1.8) and 0.33 µm (1.5), respectively. Rats were sacrificed at 3 d, 1 wk, and 1, 3, 6 and 12 months after the inhalation experiment. The lung burden of POW at 3 d after 4 wk inhalation was 1.49 ± 0.19 mg, which was close to the estimated amount of overload. The BHT of the total mass (4.1 months) was not prolonged, but aggregated dust cells were observed in the subpleural region and around the bronchioles and mild fibrotic changes were observed only around the dust cells at one year after the 4-wk inhalation. It is considered that the excessive exposure which impairs the function of alveolar macrophage mediated clearance may cause the aggregation of dust cells and fibrotic changes. It is well known that the inhalation of asbestos in the working environment leads to pulmonary fibrosis, lung cancer and mesothelioma. With the prohibition of asbestos usage and advances in manufacturing technology, various kinds of asbestos substitutes are now being produced, but due to the fibrous nature of these substances similar to asbestos, their health effects should be investigated. One of these substitutes, potassium octatitanate whisker (POW), has two types, TW and PT1, which are made by different manufacturers. In order to examine whether the pulmonary effect of these POWs differ from maker to maker, we carried ...

Silicon carbide whisker (SiCW) is a durable asbestos substitute. To clarify the biopersistence, the changes of geometrical configurations of deposited whiskers, and potential carcinogenicity and fibrogenicity, 42 Wistar male rats were exposed to SiCW for 6 h/day, 5 days/wk for 1 yr by inhalation. The mass median aerodynamic diameter (geometric standard deviation, GSD), the geometric mean fiber diameter (GSD), and the geometric mean fiber length (GSD) were 2.4 microm (2.4), 0.5 microm (1.5) and 2.8 microm (2.3), respectively. The daily average exposure concentrations were 2.6 +/- 0.4 mg/m3 (98 +/- 19 fibers/ml) and the rats were sacrificed at 6 days and 3, 6, and 12 mo after the exposure. The SiCW amount deposited in each rat lung at 6 days after the exposure, determined by an x-ray diffraction method, was 5.3 +/- 1.4 mg. The biological half-time (BHT) was 16 mo calculated from the deposited SiCW at 6 days and 3, 6, and 12 mo. The BHT was more prolonged than normal physiological clearance. The diameter of SiCW in the lung at each sacrificed time during 12 mo of clearance after the inhalation did not change. However, as for the length of SiCW in the lung, longer SiCW tended to be retained in the lung as the clearance time increased, especially after 6 mo. The histopathological examination revealed bronchoalveolar hyperplasia (BAH) in 2 rats at 1 yr after the exposure and severe fibrotic changes around aggregated SiCW.

The aim of this study was to clarify the association between sleeping time and job stress in male Japanese workers. Male workers at one manufacturing plant were surveyed about job stress and sleeping time using a selfcompleted questionnaire. A total of 274 white-collar daytime workers were analyzed. Job stress factors and stress response were assessed using the Job Stress Questionnaire. Sleeping time on working days was divided into ≤ 5 h, 6 h, 7 h, and ≥ 8 h, and associations between job stress factors and stress response were analyzed. Shorter sleeping time was related to overtime work; about a quarter of those with sleep of ≤ 5 h worked more than 15 h overtime per week. Workers with shorter sleeping time, particularly those with ≤ 5 h sleeping time, were more likely to have job stress factors of quantitative workload and interpersonal conflict as well as psychological stress responses, such as anger, fatigue, tension/anxiety, and depressive symptoms. With shorter sleep, in subjects ≤ 39 years, scores of activity and fatigue decreased or increased respectively, whereas in those ≥ 40 years, scores for tension/anxiety and depressive symptoms increased. Shorter sleeping time was related to overtime work and increased job stress in male white-collar workers. Depression symptoms may be more closely associated with shorter sleeping times in workers aged ≥ 40. Adequate sleep duration is important for maintaining mental health.