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Polycyclic aromatic hydrocarbons (PAHs), some of which are carcinogenic/mutagenic, are generated by combustion of fossil fuels and also released through tanker or oilfield accident to cause a large scale environmental pollution. PAHs concentration in China is especially high in East Asia because of many kinds of generation sources such as coal heating systems, vehicles and factories without exhaust gas/particulate treatment systems. So, the atmospheric pollution caused by PAHs in China has been seriously concerned from the view point of health effects. Like yellow sand and sulfur oxide, PAHs exhausted in China are also transported to Japan. Additionally, strongly mutagenic nitrated PAHs (NPAHs), estrogenic/antiestrogenic PAH hydroxides (PAHOHs) and reactive oxygen species-producing PAH quinones (PAHQs) are formed from PAHs by the chemical reaction during the transport. Furthermore these PAHOHs and PAHQs are produced by the metabolism in animal body. In the biological activities caused by the above PAH derivatives, the structure-activity relationship was observed. In this review, our recent results on the generation of PAH derivatives by atmospheric transport and metabolism are reported. Also, the existing condition of PAHs as atmospheric pollutants is considered.

Airborne particulate matters contain many kinds of organic pollutants. Among them, polycyclic aromatic hydrocarbons (PAH), nitropolycyclic aromatic hydrocarbons (NPAH) and quinoid PAHs were reported to have several human health effects. We collected airborne particulates in Kitakyushu, Japan and Tieling, China in summer and winter, and analyzed the PAH and NPAH to evaluate the direct- and indirect-acting mutagenicities and generating activities of reactive oxygen species (ROS). The concentrations of PAHs and NPAHs in Tieling were much higher than in Kitakyushu, with seasonal variations. The mutagenicity level was higher in winter while the ROS generation activity was higher in summer. These results suggest that concentrations of PAH and NPAH didn't correlate with mutagenicity and ROS generation activity. More studies are needed on the environmental behaviors of compounds other than PAHs and NPAHs, such as quinoid PAHs, and their biological activities.

The relics of disrupted satellite galaxies have been found around the Milky Way and Andromeda, but direct evidence of a satellite galaxy in the early stages of disruption has remained elusive. We have discovered a dwarf satellite galaxy in the process of being torn apart by gravitational tidal forces as it merges with a larger galaxy's dark matter halo. Our results illustrate the morphological transformation of dwarf galaxies by tidal interaction and the continued buildup of galaxy halos.

Motivated by the recently improved knowledge on the kinematic and chemical properties of the Galactic metal-poor stars, we present the numerical simulation for the formation of the Galactic stellar halo to interpret the observational results. As a model for the Galaxy contraction, we adopt the currently standard theory of galaxy formation based on the hierarchical assembly of the cold dark matter fluctuations. We find, for the simulated stars with &sqbl0;Fe&solm0;H&sqbr0;