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FY2014 Annual Report of Environmental Health Surveillance for Air Pollution

July 22, 2016

The results of the FY2014 environmental health surveillance for air pollution have been compiled and are presented below.

The Ministry of the Environment (MOE) has been implementing the surveillance 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.

1. Overview of the Surveillance Result

 The FY2014 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 (FY2014), and a longitudinal analysis was performed using the integrated results of 3-year-old surveys from FY1996 to FY2014 and 6-year-old surveys from FY2004 to FY2014. Additionally, a follow-up analysis was performed on 6-year-old survey respondents who also responded to the 3-year-old survey conducted in FY2010 and FY2011.

 The 3-year-old survey targeted approximately 86,000 3-year-old children in 37 regions throughout Japan (72,000 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 both the 3-year-old and 6-year-old surveys, the 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, yielded results that showed no correlation in which higher air pollution concentrations led to a higher prevalence of asthma. The examination of odds ratios also yielded results that showed no significant positive correlation between air pollution and asthma prevalence.

 In the 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.

 The comprehensive analysis of the 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 found no correlation in which higher air pollution concentrations led to a higher prevalence of asthma. In the examination of odds ratios, a significant positive correlation was observed between air pollution (SPM) and asthma in both the survey of 3-year-olds (odds ratio: 1.02) and the survey of 6-year-olds (odds ratio: 1.04). However, no significant positive correlation was found between pollutants other than SPM and asthma in either the 3-year-old survey or 6-year-old survey.

 A similar examination was conducted in regard to incidence rate (excluding longitudinal and comprehensive analysis), but the results showed no significant correlation.

 With regard to factors others than air pollutants, a significant positive correlation was found with an odds ratio of around 2 in both the 3-year-old and 6-year-old surveys, in cases where the subject and the subject's parents had a past history of allergy. The examination of odds ratios using integrated data also yielded a similar result.

 In terms of the prevalence rate of respiratory diseases 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 and NOx in the survey of 3-year-old survey, and between the frequency of catching a cold (more than five times) and NOx in the survey of 6-year-old survey.

2. Future Issues

 A number of previous surveys that have been conducted since FY2007 produced a result that indicated a significant positive correlation between air pollution (SPM) and asthma or between air pollution (SPM) and asthma (developed within the past two years) among both 3-year-olds and 6-year-olds. However, these results cannot be seen as indicating a certain trend of significant positive correlation. In an examination using integrated data, the examination of odds ratios in both the 3-year-old and 6-year-old surveys shows a significant positive correlation between air pollution (SPM) and asthma, but with respect to 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 in which higher air pollution concentrations led to a higher prevalence of asthma.

 A follow-up analysis of surveys since FY2004 also showed a significant positive correlation between air pollution (NO2, NOx) and asthma incidence in the FY2013 survey, but since no significant positive correlation has ever been reported in any other year, the result cannot be seen as a certain trend.

 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 more than 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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