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OBJECTIVE Bacteria on the facepiece of a dust respirator were measured just after use and after 24-hours storage at a room temperature after being worn, and bacteria disinfection methods other than ethanol were examined. METHODS The existence of bacteria on a facepiece of a mask that had been worn for about one hour in a laboratory was investigated. In order to eliminate bacteria before use on the next day, five methods of bacteria disinfection were investigated: wiping with a facial tissue impregnated with ethanol as a control; wiping with a facial tissue wetted with tap water; wiping with a dry facial tissue after wiping with one wetted with tap water; wiping with a dry facial tissue after wiping with one wetted with distilled water; and wiping with a dry facial tissue two times. The tests were carried out using silicone rubber sheets plated with bacteria collected from human skin. The disinfection methods that were as effective as facial paper wetted with ethanol, were then assayed on the facepiece of the dust respirator. RESULTS Bacteria were detected on the facepiece immediately after it had been worn. Bacteria were also detected on the facepiece after it had been stored at 25°C for 24-hours after being worn. The methods of wiping with a dry facial tissue after wiping with either tap water or distilled water were almost as statistically effective as wiping with ethanol wetted facial paper. Bacteria on the facepiece were decreased by wiping with a dry facial tissue after wiping with one wetted with tap water. DISCUSSION Colonies of bacteria were detected on a facepiece that had been stored 24 hours after being worn, which suggests that bacteria disinfection just after a respirator has been worn should be recommended. It is very important that the water on the facepiece should be removed after wiping with a wet facial tissue.

Bioaerosols cause sick building syndrome (SBS) and allergy. Many kinds of bioaerosol impactors are used for measurement of airborne microorganism concentrations in Japan. However, because the impactors are set on agar plates, some microorganisms cannot make colonies on the plates because of their lower viability or demands of nutrition. On the other hand, by double staining using ethidium bromide (EtBr) and carboxyfluorescein diacetate (CFDA), both total cells and cells with esterase activities can be detected without incubation. In this study, we calculated total cell concentrations and percentages of cells with esterase activities by the combination of filter sampling and double staining (EtBr and CFDA) from air of a laboratory, a conference room and outdoors. Temperature and humidity in the laboratory were constantly kept by an air conditioner, but in the conference room, an air conditioner was only operated sometimes because of its low frequency of use. There were no significant differences between total cell concentrations and humidity in both rooms, but increase of the percentages of cells with esterase activities depended on rainfall before the samplings (n=15, p

Bioaerosols including bacteria and fungi have been almost unrecognized as pollutants of work environments in Japan. The combination of filter sampling and DNA staining by ethidium bromide (EtBr) was examined for the detection and evaluation of total numbers of bioaerosols, including viable and dead microorganisms, for risk assessment in work environments. With direct counting of microorganisms by EtBr concentrations of total cells were obtained in a shorter time than plate culture, the traditional method for detection of microorganisms. Total cell concentrations (cells/m3) were about 100 times greater than colonized cell concentrations (CFU/m3) in all samples. In some microscopic fields, macro conidia produced from some kinds of fungi were observed, but they were not detected by plate culture. Airborne bacterial 16S rDNA amplified by PCR were determined for their base sequences by DNA sequence analysis and classified by sequence-based homologies. Base sequences from 2 samples each contained 6 common groups of phylum. The combination of filter sampling and direct counting by EtBr staining was shown to be a better method for detecting and evaluating total cell concentrations in the risk assessment of sick building syndrome and allergy.

We investigated the methodology for installing effective smoking rooms in workplaces. It is absolutely necessary to install exhaust ventilation in smoking rooms. There are two bases for deciding the exhaust ventilation rate. The most important is to eliminate the leakage of environmental tobacco smoke (ETS) from the smoking room. An airflow rate of more than 0.2 m/s at the opening of the smoking room is required by the Guidelines for Smoking Control in Workplaces (Ministry of Labour, Welfare and Health) to eliminate the leakage. This ventilation rate is decided by multiplying the opening area by 0.2 m/s. The second important point is to keep the concentration of ETS in the smoking room less than control concentration (0.15 mg/m3). This ventilation rate is decided by dividing the rate of generation of ETS by the control concentration. It is confirmed that an effective smoking room can be installed by following these guidelines. We used real-time monitoring to evaluate the leakage of ETS from the smoking room and the ETS concentration in the smoking room before and after the improvement. It is concluded that real-time monitoring of ETS is a useful method for evaluating the effectiveness of the smoking room.

We installed an effective, practical and low-cost smoking corner in an office to protect against passive smoking. The smoking corner was separated from the non-smoking area with transparent, nonflammable screens. Four exhaust fans were installed in the smoking corner so that there was no leakage of environmental tobacco smoke. The required exhaust air rate in the smoking corner was pre-calculated from the volume of the smoking corner and the rate of consumption of cigarettes. The suspended airborne particle concentration definitely decreased in the non-smoking area after installation of the smoking corner. The result of a questionnaire survey also revealed the improvement in the air quality in this office.

The present study describes an investigation on the use and management of ethylene oxide (EO) which is used mainly as a sterilant in medical institutions in a Cabinet-order designated city. Information was obtained from a self-administered questionnaire on safety and health matters related to sterilization with EO gas. The questionnaire was sent to 189 medical institutions including major hospitals and randomly selected clinics. 127 questionnaire were returned and the analysis was carried out for 120 respondents, excluding seven respondents whose answers were found to be inappropriate. The proportion of medical institutions, employing more than 50 workers, in which an occupational health physician and/or health supervisor was appointed was 70% and was lower than for other industries. 1.6% of the employees engaged in EO sterilization activities in the hospitals, whereas in clinics the percentage was as high as 20%. Several problems were found both in the management and work methods with EO: operations were not isolated in 46%; gas leaks and back-streaming of exhaust gas were found in 59% and 41%, respectively; and personal protective clothing was not used in 69%. Improvement was found only for three items among the institutions where an occupational health physician was appointed. These results suggest that good workplace controls and practices are essential for medical institutions using hazardous materials including EO for sterilization.