In vitro exposure systems using an air-liquid interface have been developed to assess responses of respiratory cells to air pollutants including automobile exhaust. Direct exposure to dry gas can physically damage cells independently of any toxicity. Indeed, exposure of human alveolar epithelial cells (A549) to clean dry air decreased cell viability in a time-dependent manner. Two treatments to reduce this reduction in cell viability were tested: cell cultivation on collagen gel, and humidifying the air by bubbling. A time-dependent reduction in cell viability was still detected in cells cultivated on collagen gel, though it was greatly attenuated. Exposure to humidified air (85%RH) caused less cell damage, and cell viability was maintained at similar levels after short (1hr) or long (6hr) exposure times. These results suggest that humidifying the test gas may be the most effective tool to maintain a stable cell environment during exposure.

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Catalyst Coated Membranes (CCMs) were prepared using sulfonated polyethersulfone (SPES) membranes, Pt/C electrocatalyst and electrolyte solution of Nafion DE2020. I-V performance of the CCMs was compared with Nafion211 membrane. I-V performances of the CCMs prepared with SPES membranes were relatively lower than that of Nafion 211 membranes although the SPES CCMs had similar cell resistance and lower hydrogen cross leak current compared to the Nafion CCMs. From the test outcome, which investigated the effect of dew point on I-V performance, it was indicated that improvement of proton conductivity and the water transport characteristic were necessary for the I-V performance improvement of CCMs using SPES membranes.

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TS Fuel-cell vehicles are designed so that hydrogen leaks from the tank are stopped automatically upon detection of hydrogen leakage or detection of impact in a collision. However, to understand a possible scenario if the automatic system fails, we investigated the characteristics of hydrogen leakage sound from a hydrogen-leaking vehicle and characteristics of an alternative gas that is equal to the noise level of a hydrogen leak sound. We conducted hearing tests in an anechoic chamber to clarify how to rescue people safely in the event of a continuous hydrogen leak, depending on the sense of human hearing. As a result, we found that because of the audible characteristics of hydrogen leaks from vehicles, when approaching a hydrogen-leaking vehicle, it is best to first listen while walking around the vehicle and then approach from the maximum sound direction. In addition, a leak becomes difficult to hear when subjects are very close the vehicle. We also found that there is a linear relationship between hydrogen and helium flow rates when converting them using the noise levels in front of the vehicle. The sound pressure level of the hydrogen leaking from a pipe installed in the lower part of the vehicle and that of a helium leak are almost equal.

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This report describes walking behaviors of elderly people when they crossed roads with bad visibility on Japanese several driving school courses. Elderly people were asked to cross the road in the same manner as they would in their daily lives, and their walking behaviors were unobtrusively observed. The behaviors of fifty-nine elderly people were recorded by obscured video cameras. The results of the observation showed that the elderly people tendednot to stop and look right and left when they crossed the road. The report discusses the necessity of road safety education for elderly people.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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