Investigation of Health Effects from Exposure to Airborne Benzyl Chloride: Case of an Explosion of Uninterruptible Power Supply in a Hospital

Abstract

 The Office of Disease Control and Prevention, Region 4 Saraburi Province (ODPC 4) was notified by the Lopburi Provincial Public Health Office (LPPHO) regarding an accident involving the explosion of an uninterruptible power supply (UPS) within a hospital, on 28 December 2024. Following the explosion, executives and staff concerned about their health effects due to the presence of residual chemical odor. ODPC 4 and related organizations conducted 4 onsite investigations on 6, 13, 15, and 16 January 2025, respectively. The objectives were to confirm the diagnosis, describe the incident, survey a potentially dangerous environment, and propose health measures to prevent chemical exposure. A descriptive epidemiological study was conducted by interview and chemical vapor was measured by the portable gas analyzers. Descriptive statistics were used to analyze data. The investigation found 129 people exposed to chemicals. Of those, 79 people presented symptoms of respiratory irritation followed by no symptom (48 people) and eye burning/tear flowing (36 people). Health surveillance of 55 people from high-risk groups, including blood lead levels, complete blood counts, blood nitrogen estimates, blood values indicating kidney function, and stress assessments, found that all high-risk groups maintain normal results. Benzyl chloride content was measured in averaged value of 3.61, 2.70, 3.22, and 1.21 ppm, respectively (Average standard value over the entire working period less than 1 ppm). Benzyl chloride vapor was deduced from considerable electrical insulation burning which contained polyvinyl chloride (PVC) and spread to different hospital areas. Due to the molecular mass of benzyl chloride is about four times heavier than the atmospheric air, it will acquire negative pressure after the air is aspirated from a room and the benzyl chloride will recur if not replaced by the fresh air. Therefore, residual benzyl chloride vapor was identified after air extraction in some rooms. Benzyl chloride half-life in air is four days. However, in the fourth measurement, the evaporation value of benzyl chloride decreased from the initial value in all areas, which is expected to be due to the aforementioned improvement measure. These findings suggest preventive measures should include studying chemical information before managing ventilation, as well as providing knowledge and protective equipment for staff properly in the area.