Assessing the risk of exposure to Gram-negative bacteria in indoor environments based on the endotoxin levels of airborne bacteria

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04822
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 23020:Architectural environment and building equipment-related
• Research Institution: University of Occupational and Environmental Health, Japan
• Principal Investigator: Ishimatsu Sumiyo 産業医科大学, 産業保健学部, 教授 (40289591)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: エンドトキシン濃度 / 浮遊細菌数濃度 / PM2.5 / 総粉じん

Outline of Final Research Achievements

To assess the exposure risk of Gram-negative bacteria, I conducted temporal measurements of bacterial concentration and endotoxin (ET) concentration in total particulate matter and PM2.5 in two indoor and outdoor environments, and obtained the following results. The primary source of Gram-negative bacteria indoors is from the outdoors, and even during the occurrence of yellow sand, the indoor ET concentration remained well below the DECOS TLV-TWA, indicating a low health risk associated with exposure. There was a positive correlation between outdoor bacterial concentration and ET concentration, regardless of particle size, suggesting that the proportion of Gram-negative bacteria with ET remained relatively constant. While the correlation between the two decreased indoors, considering that the ET concentration reflects the fluctuations of Gram-negative bacteria, it is believed that the ET concentration can be utilized as an exposure indicator for Gram-negative bacteria.

Free Research Field

作業環境管理学

Academic Significance and Societal Importance of the Research Achievements

本研究の目的は、グラム陰性細菌が持つエンドトキシン（ET）をもとにして、細菌種に関係なくグラム陰性細菌集団としての健康リスク評価指標の可能性を探ったものである。屋外では浮遊細菌数濃度とET濃度に正の相関性が認められたことから、ETは浮遊細菌曝露の健康リスク指標になりうると考えられた。室内では両者の相関性は低くなったが、ET濃度はグラム陰性細菌以外には関係しないため、ET濃度はグラム陰性細菌への曝露リスク指標となると考える。