Although it is known that aerosols such as PM2.5 affect human health, there is a large area difference in the extent of the effects among the epidemiologic studies, and elucidating the mechanisms for this difference has been awaited.

The candidates for the factors that explain area-difference would include new exposure index and confounding factors.  For the new indices, size and chemical property of the aerosols and come metals are proposed.  For examining whether these factors really contributed or not, the information from A01 and A02 that precisely measure actual level of exposure in Asian countries is useful.  Regarding trans-boundary air pollution, because A01 and A02 provide the information of the aerosols from their sources and destinations, it should be easy to connect the impact assessment results to the preventive measures at the air pollution sources. 

Another issue is a pollen disease.  Cedar pollen disease has been a common problem in Japan, and its onset and exacerbation are thought to be linked to trans-boundary air pollution including Asian dust.  Hence it is important to analyze these complex exposure patterns.

As for confounders, various factors including exposure difference between outdoor and indoor, weather should be considered.  First, we investigate the candidate exposure indices obtained from A01 and A02, experimentally excluding the effects of these factors.  However, because in vitro or in vivo studies do not necessarily provide us the impact identical to that for humans, epidemiological studies that examine the human impacts also important.  In the epidemiological studies, we control for confounders by including the factors as the predictors in the model.  As of now, the studies in Asia have been analyzed individually with different models, and it was impossible to distinguish whether the difference is due to area or due to model.  To overcome this problem, we will analyze the multi-country data with a unified method in this study.  Another advantage of this study is that we can obtain detailed exposure information from A1 and A2, which cannot usually be available in epidemiological studies.  For example, NMMAPS studies in the US use air pollution data from the US observatory stations (Check if this is correct).  With this new feature, we believe our study add some new insights in the human impact of aerosols.

Another unique feature of this study is that it takes trans-boundary pollution into account.  Although some studies on Asian dust and human health have been conducted in Korea and Taiwan, we still do not have enough evidence to reach conclusion.

This study can be regarded as the first comprehensive study of human impact of aerosols.