Indoor penetration of ambient particulate pollution in a hospital maternity ward in Manila, Philippines: perspectives towards holistic city-level air quality management†

Several studies have analyzed and reported the relationship between particulate matter (PM) in the air and its adverse health effects, primarily on fetal development and subsequent early childhood. This study aims to understand how outdoor air made up of mainly PM, influences indoor air quality in a naturally ventilated maternity ward in an urban hospital setting. The data collection site in this study was the Dr Jose Fabella Memorial Hospital, a maternity hospital located in Manila, Philippines. Indoor and outdoor PM_2.5 levels from November 2021 to June 2022 were investigated. A strong positive correlation (r² ranging from 0.78 to 0.98) was observed between the daily outdoor and indoor PM levels. While the median concentrations were above the World Health Organization (WHO) air quality guidelines, they were below the Philippine National Ambient Air Quality Guideline Values (NAAQGV) at the time of data collection. These results underscore the importance of updating guideline values. Indoor-to-outdoor diurnal ratios (I/O), ranging from 0.77 to 1.33, with peak times (indoor-source-dominated) between 12:00 and 13:00 and trough times (outdoor-source-dominated) between 04:00 and 05:00, offered insight into the times of the day dominated by indoor versus outdoor sources and highlighted the need for continuous air monitoring while providing additional protection in indoor spaces, such as clear indoor air quality guidelines combined with indoor ventilation and filtration requirements. These results highlight the need for a holistic air quality management approach which focuses concurrently on both ambient and indoor air quality in healthcare facilities. Naturally ventilated hospitals must be included as a priority monitoring site, as they are a critical in improving air quality in the context of public health protection.