Association between traffic-related air pollution and asthma in preschool children in a national Japanese nested
Hideki Hasunuma1, Tosiya Sato2, Tsutomu Iwata3
1Department of Public Health, Hyogo College of Medicine, Nishinomiya, Japan Center for Environmental Information Science, Tokyo, Japan.
Insights
Traffic-related air pollution, specifically nitrogen oxides (NOx), is linked to the persistence of asthma symptoms in preschool children. This study highlights its role as a risk factor for childhood airway disease.
Area of Science:
- Environmental Health
- Pediatric Respiratory Medicine
- Epidemiology
Background:
- Asthma is a prevalent childhood respiratory condition.
- The impact of traffic-related air pollution on asthma incidence and persistence in young children remains understudied.
- Preschool children may be particularly vulnerable to air pollutants due to developing respiratory systems.
Purpose of the Study:
- To investigate the association between traffic-related air pollution exposure and the incidence of new-onset asthma in children during their first three years of life.
- To evaluate the link between traffic-related air pollution exposure and the persistence of asthma symptoms in preschool children.
- To assess the role of nitrogen oxides (NOx) and elemental carbon (EC) as potential contributors to childhood asthma.
Main Methods:
- A large population-based cohort study involving over 63,000 children at baseline (1.5 years old) and over 43,000 at follow-up (3 years old).
- Estimation of outdoor concentrations of NOx and EC using a dispersion model based on home locations during the first 1.5 years of life.
- A nested case-control study to assess personal exposure levels, incorporating time-activity patterns, for asthma incidence.
Main Results:
- No statistically significant association was found between personal exposure to NOx or EC and the incidence of asthma between 1.5 and 3 years of age.
- A significant association was observed between outdoor NOx concentrations and the persistence of asthmatic symptoms from 1.5 to 3 years.
- Children in the highest exposure group (upper 5th centile of NOx) had significantly higher odds of persistent asthma symptoms (OR=6.02) compared to the lowest (lower 25th centile).
Conclusions:
- Traffic-related air pollution, particularly NOx, is a significant risk factor for the persistence of asthma symptoms in preschool children.
- While not linked to new-onset asthma in this study, air pollution's role in exacerbating or maintaining existing asthma is supported.
- Further research and public health interventions targeting air quality are warranted to mitigate childhood airway diseases.
Objectives:
There 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.
Methods:
A 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.
Results:
There 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 ears) 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.
Conclusions:
While 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.
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