Association between daily ambient air pollution and respiratory symptoms in children with asthma and healthy children in western Japan

ABSTRACT

Objective: In recent years, air pollutant concentrations in Japan have decreased slightly; however, there are growing concerns about the influences of transnational air pollution on respiratory illness. We aimed to clarify the short-term association between the ambient air pollution and respiratory symptoms among children without asthma, children with asthma not using long-term medications (CA-nonLTM), and those using them (CA-LTM). Methods: A total of 138 children attending 2 primary schools and 71 children with asthma regularly visiting cooperating medical institutions were recruited. Study participants measured peak expiratory flow (PEF) twice a day and recorded coughing, nasal symptoms, and medication use in a diary. Predicted associations between daily air pollutant concentrations and respiratory symptoms, and PEF were evaluated using case-crossover and generalized estimate equation models. Results: Changes in %maxPEF per 10 ppb oxidant (Ox) increase in children without asthma, CA-nonLTM, and CA-LTM were −0.26% (95% CI: −0.49, −0.03), −0.51% (95% CI: −0.89, −0.12), and −0.20% (95% CI: −0.42, 0.01), respectively. The odds ratios for coughing per 10 ppb Ox increase in the Lag0 model were 1.34 (95% CI: 1.11, 1.60), 1.52 (95% CI: 1.12, 2.07), and 1.06 (95% CI: 0.93, 1.20), respectively. These suggested that the Ox concentration has graded effects on %maxPEF and coughing, in the following descending order, CA-nonLTM, children without asthma, and CA-LTM. The Ox concentration was also positively associated with nasal symptoms in children without asthma and CA-LTM. Conclusion: 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.

KEYWORDS:

• Peak expiratory flow
• medication use
• school children
• asthma attack
• air pollution
• ozone
• PM_2.5

Acknowledgements

We thank 22 cooperating medical institutions: Aichi children's health and medical center (Aichi prefecture), Toyooka hospital (Hyogo), JA Hiroshima general hospital (Hiroshima), Kato kid's clinic (Hiroshima), Koyo new town hospital (Hiroshima), Yamaguchi grand medical center (Yamaguchi), Yamaguchi university hospital (Yamaguchi), Ehime prefectural Imabari hospital (Ehime), Ehime prefectural Niihama hospital (Ehime), Kera pediatrics allergy clinic (Kochi), Araki pediatric and allergy clinic (Fukuoka), Koga pediatric clinic (Fukuoka), Matsuda pediatric clinic (Fukuoka), Matsumoto pediatric clinic (Fukuoka), Nakao pediatric clinic (Fukuoka), Okabe allergic clinic (Fukuoka), Umeno pediatrics physician's office (Fukuoka), Yamauchi clinic (Kumamoto), Oita university hospital (Oita), Imamura pediatrics (Kagoshima), Makurazaki kodomo clinic (Kagoshima), and Naha city hospital (Okinawa).

We also thank members of the Environmental Health Affairs Office of the Ministry of the Environment Government of Japan (who worked as coordinating officers) and the Center for Environmental Information Science, Tokyo, Japan (a data center for this study). The views expressed in this article are those of the authors and do not necessarily reflect those of the Ministry of the Environment Government of Japan.

Declaration of interest

The authors have no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Funding

This study was partly funded by the Ministry of the Environment Government of Japan.