Effects of exposure to chemical components of fine particulate matter on mortality in Tokyo: A case-crossover study

Abstract

Fine particulate matter (PM2.5) is composed of a variety of chemical components, and the dependency of the health effects of total PM2.5 on specific components is still under discussion. We hypothesised that specific PM2.5 components are responsible for the health effects, and investigated the association between PM2.5 components and mortality in 23 Tokyo wards. We obtained mortality data from the Ministry of Health, Labour and Welfare for the period from April 2013 to March 2017. At a monitoring site within the study area, we collected daily samples of PM2.5 on a filter, and determined the daily mean concentrations of total carbon (organic carbon and elemental carbon) and ions such as nitrate and sulphate. A case-crossover design was employed, and a conditional logistic regression model was used to estimate the strength of the association. Over the study period, we identified 280,460 total non-accidental deaths, and the average daily mean concentration of total PM2.5 was 16.0 (standard deviation = 8.9) μg/m3. We observed a positive association of total PM2.5 with total, cardiovascular, and respiratory mortality. After adjustment for total PM2.5 and its components associated with mortality in the single-component models, the percentage increase per interquartile range (2.3 μg/m3) increase in the average total carbon concentration of the case- and previous-day was 2.1% (95% confidence interval = 1.0 to 3.1%) for total mortality. Carbon elements were associated with respiratory but not cardiovascular mortality. Our results suggest that specific components of PM2.5 account for its adverse health effects.