Measurements of PM₂.₅ concentration were conducted aboard the research vessel Akademik Oparin from April 24 to June 10, 2021. The expedition started in Vladivostok, Russia. The vessel's route covered the southern part of the Sea of Japan, the East China Sea, the western Philippine Sea (near the Yakushima Islands), and the South China Sea. The final destination of the vessel was Hai Phong on the northern coast of Vietnam. Measurements were performed using dichotomous particulate matter analyzer PM-712 (Kimoto Electric Co., Ltd., Japan). Table 1 provides the averaged PM₂.₅ concentration data.