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(Notice) FY2013 Annual Report of Environmental Health Surveillance for Air Pollution

July 24, 2015

The Ministry of the Environment (MOE) has been implementing environmental health surveillance for air pollution every year since 1996 in response to the amendment to the Pollution related Health Damage Compensation Law of 1988. It aims to regularly and continuously observe the correlation between the health conditions of local populations and air pollution, and to take measures as necessary. The results of the FY2013 surveillance have been compiled and are presented below.

1. Overview of the Surveillance Result

 The FY2013 surveillance targeted 3-year-old children (hereinafter, "3-year-old survey") and first-year primary school children (hereinafter, "6-year-old survey") as in previous years. A cross-sectional analysis was performed using the results of these surveys (FY2013), and a longitudinal analysis was performed using the integrated results of 3-year-old surveys from FY1996 to FY2013 and 6-year-old surveys from FY2004 to FY2013. Additionally, a follow-up analysis was performed on 6-year-old survey respondents who also responded to the 3-year-old survey conducted in FY2009 and FY2010.

 The 3-year-old survey targeted approximately 87,000 3-year-old children in 37 regions throughout Japan (73,000 respondents), and the 6-year-old survey targeted approximately 85,000 6-year-old children in 38 regions throughout Japan (74,000 respondents).

 Among the respiratory symptoms surveyed, the results of analyses relating to asthma were as follows.

 In an examination of odds ratios, a significant positive correlation was observed between air pollution (SPM) and asthma in 3-year-old survey (odds ratio: 1.18, 95% confidence interval: 1.01 - 1.39). A significant positive correlation between air pollution (SPM) and asthma (developed within the past two years) was also observed in 6-year-old survey (odds ratio: 1.15, 95% confidence interval: 1.01 - 1.31). With respect to air pollutants other than SPM, no significant positive correlation was found between them and asthma in neither the 3-year-old nor 6-year-old survey.

 In an examination of the prevalence of respiratory symptoms in each subject group according to the background levels of pollutant concentrations, and according to the average background concentration level in each survey area, the results showed no correlation that indicate a higher prevalence of asthma at higher air pollution concentrations.

 In an examination of the correlation between air pollutant concentrations and yearly changes in the prevalence of respiratory symptoms, there were no regions where air pollution may have caused an increase in asthma prevalence. However, in a similar examination that was conducted in regard to incidence rate (excluding the analysis of yearly changes), a significant positive correlation was observed between air pollution (NO2, NOx) and asthma incidence, in terms of odds ratios (NO2 odds ratio: 1.13, 95% confidence interval: 1.01 - 1.27; NOx odds ratio: 1.10, 95% confidence interval: 1.03 - 1.19).

 With respect to symptoms other than asthma, an examination of odds ratios showed a significant positive correlation between the frequency of catching a cold (more than five times) and NO2, NOx, SPM, and between wheezing (not associated with a cold) + asthma and SPM in 3-year-old survey, and between the frequency of catching a cold (more than five times) and NOx in 6-year-old survey.

2. Future Issues

 The survey that was conducted this fiscal year revealed a significant positive correlation between air pollution (SPM) and asthma among 3-year-olds, and between air pollution (SPM) and asthma (developed within the past two years) among 6-year-olds. Some of the previous surveys that have been conducted since FY 2007 have also shown a similar result that can be seen as indicating a significant positive correlation. A significant positive correlation was found between air pollution (SPM) and asthma among 3-year-olds as well as 6-year-olds, and between air pollution (SPM) and asthma (developed within the past two years) among 6-year-olds. However, these results cannot be seen as indicating a certain trend of significant positive correlation.

 The examination of odds ratios for this fiscal year showed a significant positive correlation between air pollution (NO2, NOx) and asthma incidence in a follow-up analysis. However, the result cannot be seen as a certain trend, since no significant positive correlation between air pollution and asthma incidence has ever been reported in previous surveys.

 According to environmental surveys, air pollution is generally decreasing, but careful monitoring of the correlation between air pollution and asthma shall be continued with consideration to indicators of PM2.5 and photochemical oxidants, as will be discussed later, and also in light of regional characteristics.

 The results of follow-up analysis have been evaluated on a single fiscal year basis up to now, but as ten years' worth of data has been accumulated, the evaluation method for the longitudinal and comprehensive analysis shall be examined to carefully monitor the correlation between air pollution and asthma incidence.

 With regard to PM2.5, a framework for continuous monitoring is being developed. Therefore, in view of the progress of its development, methods for analysis and evaluation of PM2.5 shall continue to be examined in this survey, such as by estimating background concentrations. Consideration will also be given to photochemical oxidants, which are causing concerns about possible health effects.

 Meanwhile, as it has been pointed out in the report on the Epidemiologic Studies on Health Effects of Localized Air Pollution in Japan (SORA Project ; an initial letter of "Study On Respiratory disease and Automobile exhaust") that the scientific findings and results accumulated by the SORA Project should be utilized fully for even more effective surveillance, a working group has been established under the Council for Environmental Health Surveillance and Health Effects of Air Pollution in Japan in FY2012. The working group is presently pursuing its agenda, and will continue to engage in its activities hereafter.

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