Monitoring and Mitigating Air Pollution in Healthcare: Characterising PM2.5 and NO2 Variability to Inform Sustainability Actions at Two UK Hospitals

Hospitals and public institutions often operate under significant financial constraints. When resources are insufficient to meet core service demands, as has been the case for the United Kingdom National Health Service (NHS), investment in air quality monitoring becomes even more challenging. This is despite clear evidence that healthcare settings are not insulated from the impacts of air pollution. Low-cost air quality sensors, which cost far less than reference grade instruments, offer a practical opportunity to generate meaningful environmental data in these environments.

At two major hospitals in Northeast England, the Royal Victoria Infirmary (RVI) and Freeman Hospital (FH) of Newcastle upon Tyne Hospitals NHS Foundation Trust, the deployment of 36 passive diffusion tubes, 9 indoor PurpleAir particulate monitors, and 3 ambient multisensor devices has enabled continuous monitoring of nitrogen dioxide (NO₂), and particulate matter with aerodynamic diameters <10µm (PM₁₀) and <2.5µm (PM_2.5) over a three-year period. These data provide valuable temporal and spatial insights across two large modern hospital campuses.

Results show that although many hospital pollution hotspots reflect wider urban traffic patterns, vehicle movements within the hospital premises also contribute substantially. A change in parking policy resulted in marked reductions in ambient pollution concentrations. At one section of the RVI, the mean difference in NO₂ concentration before and after the policy change showed a statistically significant reduction of 2.02µg/m³ with a two-sided p value of 0.007 based on a paired sample t test. This confirms that nitrogen dioxide levels decreased following the intervention. The t value of 2.722 indicates a moderate effect size.

The cleanest locations across both hospitals were consistently a staff and patient green space and a strictly managed no idling car park. Spatial analysis of diffusion tube data shows annual mean nitrogen dioxide concentrations of 19.4µg/m³ ±5.05 at FH, and 23.6µg/m³ ±5.33 at RVI in 2023. In 2024 both hospitals recorded reductions in annual mean concentrations of 4.1µg/m³ at FH and 4.4µg/m³ at RVI. Increased standard deviation in the same year highlights substantial site level variability. All ambient monitors demonstrated high variation in pollution levels within each hospital with annual mean values exceeding the World Health Organization guideline. This underscores the need for targeted interventions even within compact hospital settings of approximately 0.14 square kilometres.

Indoor PM_2.5 concentrations also showed frequent exceedances of the World Health Organization one hour guideline of 15µg/m3 and the United Kingdom 24 hour guideline of 25µg/m³. For example, the New Victoria Wing reception at RVI recorded 281 hourly exceedances in 2024. In contrast, PM10 exceedances were rare and remained below the legal limit of 35 events per year.

Both hospitals have committed to achieving Excellent status within the Clean Air Hospital Framework as part of efforts to reduce emissions and protect patients, staff and the surrounding community. The Framework provides a set of actions across Travel, Procurement, Construction, Energy, Local Air Quality, Outreach and Leadership. Low-cost sensors support implementation by enabling hotspot identification, tracking the effectiveness of interventions and providing high resolution pollution insights at an accessible cost.