FY2015 Annual Report of Environmental Health Surveillance for Air Pollution

The results of the FY2015 environmental health surveillance for air pollution have been compiled and are presented below.

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 FY2015 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 (FY2015), and a longitudinal and comprehensive analysis was performed using the integrated results of 3-year-old surveys from FY1996 to FY2015 and 6-year-old surveys from FY2004 to FY2015. Additionally, a follow-up analysis was performed on 6-year-old survey respondents who also responded to the 3-year-old survey conducted in FY2011 and FY2012.

　The 3-year-old survey targeted approximately 84,000 3-year-old children in 36 regions throughout Japan (71,000 respondents), and the 6-year-old survey targeted approximately 84,000 6-year-old children in 37 regions throughout Japan (71,000 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 single-year analysis 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 tendency 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 longitudinal analysis of air pollutant concentrations and 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 tendency in which higher air pollution concentrations led to a higher prevalence (adjusted rate) of asthma. In the examination of odds ratios, a significant positive correlation was observed between air pollution (SPM) and asthma in the 6-year-old survey (odds ratio: 1.03), but no significant positive correlation was found in the 3-year-old survey. With regard to pollutants other than SPM and asthma, no significant positive correlation was found in either the 3-year-old survey or 6-year-old survey.

　A similar examination was conducted in regard to incidence through a follow-up analysis (excluding longitudinal and comprehensive analysis), but the results showed no significant positive correlation.

　With regard to factors others than air pollutants, a significant positive correlation was found with an odds ratio of around 2 in a single-year analysis of 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 of respiratory 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 and NO_xin the 3-year-old survey, and between the frequency of catching a cold (more than five times) and NO_x in the 6-year-old survey.

2. Future Issues

　A number of previous surveys* that have been conducted produced the result that indicated a significant positive correlation between air pollution (SPM) and asthma or between air pollution (SPM) and asthma within the past two years among both 3-year-old surveys (20 surveys between FY1996 and FY2015) and 6-year-old surveys (12 surveys between FY2004 and FY2015). However, these results cannot be seen as indicating a certain trend of significant positive correlation. 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 of an examination using integrated data showed 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 prevalence in the 6-year-old survey (odds ratio: 1.03), but no significant positive correlation was found in the 3-year-old survey.

　A follow-up analysis (12 surveys between FY2004 and FY2015) also showed a significant positive correlation between air pollution (NO₂, NO_x) and asthma incidence once in the past**, but these results cannot be seen as indicating a certain trend of significant positive correlation.

　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 and other such substances, as will be discussed later, and also in light of regional characteristics.

　Analysis methods for longitudinal and comprehensive analyses shall also be examined, such as by performing a longitudinal comparison using five years' integrated data, for example, in consideration of the long-term trend in air pollution.

　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 and the handling of data shall be further examined.

　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; from the initial letters 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. The working group is presently pursuing its agenda, and will continue to engage in its activities hereafter.

* Asthma: (3-year-old surveys) FY 2008, 2013; (6-year-old surveys) FY2007, 2009

Asthma within past two years: (6-year-old surveys) FY2007, 2009, 2013

**FY2013

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