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

Particulate matter with a diameter below 2.5 µm (PM 2.5 ) is a major urban air pollutant. This is a well-acknowledged risk factor for diseases. PM 2.5 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 PM 2.5 concentration and nosocomial infection is under-researched. This study aimed to explore the association between the outdoor PM 2.5 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 PM 2.5 , PM 10 , SO 2 , and NO 2 within the same period were collected. Multivariable Fine–Gray competing risk models were constructed to explore the association between PM 2.5 and nosocomial bacterial infections in the form of a PM 2.5 single-pollutant model and PM 2.5 + SO 2 , PM 2.5 + NO 2 , and PM 2.5 + PM 2.5~10 double-pollutant models. Sixty-two neonates experienced nosocomial infections within the follow-up period. In the PM 2.5 single-pollutant model, we found a positive association between PM 2.5 and bacterial infection. Every 10-µg increase in the average of daily PM 2.5 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 PM 2.5 + SO 2 , PM 2.5 + NO 2 , and PM 2.5 + PM 2.5~10 models. The outdoor PM 2.5 concentration is positively associated with nosocomial bacterial infection in neonates.