In order to clarify the level transboundary air pollution caused by polycyclic aromatic hydrocarbons (PAHs) and genotoxic substances, aerosols were collected from forest and suburban sites in Nagasaki, west Japan, for 6 years. The PAH concentration was measured, and the genotoxicity of the substances were evaluated using the umu test. The results showed no notable trends in the concentration or toxicity of either sites throughout the study period. The suburban and forest sites shared similar seasonal fluctuation patterns and quantitative values, suggesting that the western end of Japan might be affected by long-range transported pollutants, especially in winter. PAH concentration and genotoxicity showed the same seasonal patterns of increased levels in winter and lower levels in summer. This suggests that PAHs and genotoxic substances were correlated and share common sources. Back trajectory and source analyses were conducted using the diagnostic ratios of PAHs. It was predicted that air pollution by PAHs at the forest site arise predominantly as a result of biomass or coal combustion in continental regions, such as northern parts of China and the Korean Peninsula. This is particularly expected in winter. Therefore, genotoxic substances would also be strongly influenced by transboundary pollution from the continental region. In addition, it was estimated that the contribution of transboundary PAH pollution could reach 70% at the suburban site in winter.

In order to determine recent behaviors in atmospheric polycyclic aromatic hydrocarbon (PAH) concentrations at the west end of Japan and to reveal the causes of these behaviors, atmospheric PAH concentrations were measured in suburban and forest sites of Nagasaki, Japan from 2017 to 2021. The results showed that the total concentration of PAHs decreased considerably by 60% and 57% in suburban and forest sites, respectively, over this period. When analyzed by season, the rate of decrease in winter was markedly high. Therefore, the decreasing behavior in PAH concentrations in Nagasaki in recent years was considered to be mainly due to less PAHs originating from cold continental regions such as northern China. In particular, the reduction in coal and biomass combustion for winter heating in households, the efforts to improve air quality, and the limitation of economic activities in response to COVID-19 were likely responsible for the decrease in atmospheric PAH concentrations. In addition, although the PAH concentrations decreased, there was no significant change in the breakdown of the number of benzene rings in the PAH or in the attributes of their sources.

Antidepressants are environmental contaminants widely prevalent in the environment that can affect aquatic organisms, but their underlying molecular mechanisms and species-specific sensitivities remain poorly understood. To address this knowledge gap, we performed a comprehensive molecular and pharmacological characterization of monoamine transporters (MATs), the primary targets of these pharmaceuticals, from two phylogenetically distinct teleost fish, medaka (Oryzias latipes) and ayu (Plecoglossus altivelis). We first cloned the cDNAs for two serotonin transporters (SERTa and SERTb), a dopamine transporter (DAT), and a norepinephrine transporter (NET) from both species. Pharmacological assays showed that fish SERTa is substantially more sensitive than SERTb to several antidepressants. While the overall inhibitory profiles of the antidepressants were generally conserved across species, fish SERTa orthologs were consistently and markedly more sensitive to human-targeted pharmaceuticals than the human SERT ortholog. Notably, inhibitory effects were also observed for several pharmaceuticals not traditionally recognized as targeting MATs in human. These molecular mechanisms findings help illustrate the vulnerability of aquatic wildlife to environmentally relevant concentrations of these pharmaceuticals.