Time Series Analysis of Climate and Air Pollution Factors Associated with Atmospheric Nitrogen Dioxide Concentration in Japan.

Takeshi Miyama,Chika Minejima,Kenichi Azuma,Yasuyuki Itano,Hiroshi Matsui,Masayuki Ohyama,Norimichi Takenaka

doi:10.3390/ijerph17249507

Abstract

Nitrogen dioxide (NO2) is an air pollutant discharged from combustion of human activities. Nitrous acid (HONO), measured as NO2, is thought to impact respiratory function more than NO2. HONO and NO2 have an equilibrium relationship, and their reaction is affected by climate conditions. This study was conducted to discuss the extent of HONO contained in NO2, depending on the level of urbanization. Whether climate conditions that promote HONO production enhanced the level of NO2 measured was investigated using time series analysis. Climate and outdoor air pollution data measured in April 2009–March 2017 in urban (Tokyo, Osaka, and Aichi) and rural (Yamanashi) areas in Japan were used for the analysis. Air temperature had a trend of negative associations with NO2, which might indicate the decomposition of HONO in the equilibrium between HONO and NO2. The associations of relative humidity with NO2 did not have consistent trends by prefecture: humidity only in Yamanashi was positively associated with NO2. In high relative humidity conditions, the equilibrium goes towards HONO production, which was observed in Yamanashi, suggesting the proportion of HONO in NO2 might be low/high in urban/rural areas.

Highlights

Nitrogen dioxide (NO2 ) is an air pollutant discharged from combustion of human activities such as driving cars, and numerous epidemiological studies have suggested a relationship between NO2 and impaired respiratory function or asthma symptoms [1,2,3,4].NO2 is monitored at air pollution monitoring stations (APMSs) in Japan [5], and previous studies have implied that climate factors affect NO2 levels [1,6,7]
The negative relationship between air temperature and the NO2 concentration measured at ambient air pollution monitoring station (AAPMS) from this study suggests that the identified associations showed the same trends for HONO with climate factors, and that a certain proportion of HONO was in measured NO2
The relationships between climate factors and NO2 concentrations measured in the atmosphere, the differences between the types of monitoring stations, and differences between urban and rural areas were assessed using seasonal autoregressive integrated moving average (SARIMA) and SARIMAX models in this study

Summary

Introduction

NO2 is monitored at air pollution monitoring stations (APMSs) in Japan [5], and previous studies have implied that climate factors affect NO2 levels [1,6,7]. Since climate and air pollutant time series data demonstrate seasonality and autocorrelation effects, those effects should be adjusted to find associations among the factors. A large number of studies investigated the effect of NO2 on human health status such as morbidity and mortality of diseases using time series analysis (e.g., [8,9,10]). In those studies, climate and other pollutant factors were dealt as confounders/covariates of NO2. Public Health 2020, 17, 9507; doi:10.3390/ijerph17249507 www.mdpi.com/journal/ijerph

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