Outdoor PM2.5 concentration associates with nosocomial bacterial infection in neonates in Guangzhou, China

Particulate matter with a diameter below 2.5 µm (PM2.5) is a major urban air pollutant. This is a well-acknowledged risk factor for diseases. PM2.5 positively correlates with the abundance and species of airborne bacteria. The sensitivity and fragility of neonates lead to this population being frequently admitted to the hospital and thus exposed to risk factors for nosocomial infection. However, the association between the outdoor PM2.5 concentration and nosocomial infection is under-researched. This study aimed to explore the association between the outdoor PM2.5 concentration and nosocomial bacterial infection in neonates. A total of 7482 neonates admitted to the neonatal ward at a hospital in Guangzhou, China, between 2017 and 2020 were recruited. Weather data and the average daily concentrations of PM2.5, PM10, SO2, and NO2 within the same period were collected. Multivariable Fine–Gray competing risk models were constructed to explore the association between PM2.5 and nosocomial bacterial infections in the form of a PM2.5 single-pollutant model and PM2.5 + SO2, PM2.5 + NO2, and PM2.5 + PM2.5~10 double-pollutant models. Sixty-two neonates experienced nosocomial infections within the follow-up period. In the PM2.5 single-pollutant model, we found a positive association between PM2.5 and bacterial infection. Every 10-µg increase in the average of daily PM2.5 concentration was associated with an average of 27% (95% CI, 1.02–1.55, P = 0.03) higher subdistribution hazard rate of nosocomial infection. No statistically significant association with infection was found in the PM2.5 + SO2, PM2.5 + NO2, and PM2.5 + PM2.5~10 models. The outdoor PM2.5 concentration is positively associated with nosocomial bacterial infection in neonates.