Respiratory function declines in children with asthma associated with chemical species of fine particulate matter (PM2.5) in Nagasaki, Japan

Abstract

Background The differential effects of PM2.5 fractions on children’s lung function remain inconclusive. This study aimed to examine whether lung function in asthmatic children was associated with increased PM2.5 fractions in urban areas in Nagasaki prefecture, Japan, where the air pollution level is relatively low but influenced by transboundary air pollution. Methods We conducted a multiyear panel study of 73 asthmatic children (boys, 60.3%; mean age, 8.2 years) spanning spring 2014–2016 in two cities. We collected self-measured peak expiratory flow (PEF) twice a day and daily time-series data for PM2.5 total mass and its chemical species. We fitted a linear mixed effects model to examine short-term associations between PEF and PM2.5, adjusting for individual and time-varying confounders. A generalized linear mixed effects model was also used to estimate the association for worsening asthma defined by severe PEF decline. Back-trajectory and cluster analyses were used to investigate the long-range transboundary PM2.5 in the study areas. Results We found that morning PEFs were adversely associated with higher levels of sulfate (-1.61 L/min; 95% CI: -3.07, -0.15) in Nagasaki city and organic carbon (OC) (-1.02 L/min; 95% CI: -1.94, -0.09) in Isahaya city, per interquartile range (IQR) increase at lag1. In addition, we observed consistent findings for worsening asthma, with higher odds of severe PEF decline in the morning for sulfate (odds ratio (OR) = 2.31; 95% CI: 1.12, 4.77) and ammonium (OR = 1.73; 95% CI: 1.06, 2.84) in Nagasaki city and OC (OR = 1.51; 95% CI: 1.06, 2.15) in Isahaya city, per IQR increase at lag1. The significant chemical species were higher on days that could be largely attributed to the path of Northeast China origin (for sulfate and ammonium) or both the same path and local sources (for OC) than by other clusters. Conclusions This study provides evidence of the differential effects of PM2.5 fractions on lung function among asthmatic children in urban areas, where the Japanese national standards of air quality have been nearly met. Continuous efforts to promote mitigation actions and public awareness of hazardous transboundary air pollution are needed to protect susceptible children with asthma.

Breathing zone pollutant levels are associated with asthma exacerbations in high-risk children

“…In addition, since our cohort was of moderate size and longitudinal follow up was not available on all participants due COVID-19 pandemic related study disruptions, power to detect associations between exposures and asthma outcomes was reduced, particularly for exposures with high proportions of measurements below the LOD. Additionally, although our assessment of PM was limited to PM10 in order to collect sufficient sample for constituent analyses, we acknowledge a likely role for PM2.5 (particles less than 2.5 microns in diameter) exposures in driving asthma outcomes, as has been reported 70,[100][101][102] .…”