Evaluate the Effects of Nebulizing Disinfectants on Controlling Indoor Airborne Microbes: Utilizing Hypochlorous Acid in Daycare Center

• Main Authors: Yu-Min Su, 蘇育民
• Other Authors: Huey-Jen Su
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/49681591580135211345

碩士 === 國立成功大學 === 環境醫學研究所 === 96 === Except home, kindergartens or day-care centers may be the indoor environments where pre-school-age children spend most their time. Yet, inadequate ventilation is also known to be attributable to increasing indoor air pollution as pollutants are easily accumulated, and children’s health, thereby, is thought to be in jeopardy. Among all indoor hazards of concerns, microbial contamination is given much attention especially for daycare centers. Many control or remedial strategies have been proposed for use to eliminate the exposure, and application of weak acid hypochlorous water (WAHW), identified as a good disinfectant, and was suggested to be one attractive alternative. The objective of this study was to evaluate whether spraying the WAHW could effectively reduce the airborne microbial environment of daycare centers. The study sites were randomly selected from all registered daycare centers in Tainan city, and asked for participation. Six daycare centers were chosen to investigate the indoor air quality (IAQ) in relation to ventilation rate according to the environmental questionnaires through which daycare centers with greater potential of microbial contamination were identified. Results showed the major indoor air pollutant correlated well with the varying ventilation rate was biological pollutant which was. The average indoor bacteria and fungi concentrations were 4024-18804 and 3892-9955 cfu/m3, respectively. Two daycare centers were selected for intervention study by spraying the WAHW in the classrooms without the presence of children. A week-long biological sampling of the background, including bacteria and fungi, was conducted before the remedial action took place. The WAHW was sprayed in the following week after children left the schools and before they returned the next day using a fogger. Airborne samples were also collected concurrently. Environmental sampling continued for one more week after without the application of WAHW. The identical cycle of experiements were performed twice, one in winter and the next one in summer. Two daycare centers were further identified for intervention study: KID1 with visible microbial contamination and high fungal levels measured, and KID4 with no obvious contamination yet still high fungal counts. The indoor/outdoor (I/O) ratios of airborne bacteria (median) at KID4 in the morning of three weeks were 2.69, 1.18 and 1.17 in winter, and 5.06, 0.61 and 7.36 in summer; for fungi, 1.25, 0.75 and 0.94 in winter, and 1.38, 0.63 and 1.67 in summer. For the levels of airborne fungi measured at noon time, these values were 1.13, 0.75 and 1.44 in winter and 1.38, 0.63 and 1.67 in summer. These levels appeared to decrease significantly in the weeks with spraying WAHW (p<0.05). There was, however, no particular reduction of I/O ratios observed in KID1. Meanwhile, increasing I/O ratio for environmental bacteria was correlated with greater number of people present indoors or higher ventilation measured (p<0.05). The people activity and ventilation resulting in entrance of outdoor microbes might be the reasons why reduction of indoor microbes by spraying WAHW the night before was not accomplished as expected in KID1 where high concentrations were actually measured rather than simply with the visual assessment as in KID4. Results showed that when spraying WAHW by a mechanical fogger in an indoor space without obvious contaminations, the WAHW could disinfect microbe by a significant level only over a specific period time. Future study should not only be directed with more focused design to compare concentration changes before or after the spray of WAHW, but also the variation of specific genera to better explore the rationales and mechanisms facilitating the effective reuduction of environmental microbes for formulating remedial strategy.