No abstract

ObjectivesThere has been little study on the effect of traffic-related air pollution on the incidence and persistence of asthma in preschool children. We evaluated the association of exposure to traffic-related air pollution with the incidence/persistence of asthma during the first 3 years of life using a population-based study.MethodsA baseline survey was conducted in 1½-year-old children (n=63 266). A follow-up survey at 3 years of age (n=43 343) identified new-onset asthma cases (n=853) and persistence of asthma (n=214). In the prevalence/persistence study, the outdoor concentrations of nitrogen oxides (NOx) and elemental carbon (EC) at home during the first 1½ years of life were estimated by a dispersion model. In the nested case–control study, which regarded incidence of asthma as cases, the personal exposure levels were estimated by dispersion model including time-activity pattern.ResultsThere was no statistically significant association between the incidence of asthma between age 1½ and 3 years and personal exposure levels to NOx nor EC. However, the persistence of asthmatic symptoms (between 1½ and 3 years) was significantly associated with outdoor concentrations of NOx. ORs for the persistence of asthmatic symptoms were 6.02 (95% CI 1.51 to 23.92) for the comparison between the upper 5th and lower 25th centiles of NOx.ConclusionsWhile no statistically significant association was observed for the incidence of asthma, the persistence of asthmatic symptoms in preschool children was significantly associated with traffic-related air pollution. This supports its importance as a risk factor in childhood airway disease.

To determine whether off-line fractional exhaled nitric oxide (FeNO) measurement is applicable to screen allergic airway inflammation for epidemiologic studies, we examined 280 adults, measuring off-line FeNO samplings, pulmonary function, and serum immunoglobulin E (IgE). Subjects with recurrent wheeze (recurrent wheezers) had significantly higher FeNO and IgE levels and significantly lower forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) than non-wheezers. Statistical analysis showed that FeNO and FEV1/FVC were significant predictors for recurrent wheezers, independent of smoking. The cut-off FeNO level for screening allergic airway inflammation was 38 ppb in non-smokers and 32.9 ppb in smokers. Thus, off-line FeNO can be used as a good marker to screen allergic airway inflammation, regardless of smoking.

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.

Our results suggest that using long-term medications to manage asthma may play an important role in preventing exacerbation of respiratory symptoms due to air pollution.