Environmental survey of pharmaceutical concentrations in seawater and PM2.5 concentrations in the atmosphere on Niijima Island, Tokyo

To evaluate the environmental quality of Niijima Island, we conducted a seawater survey using carbamazepine, a pharmaceutical derived from domestic wastewater, as an indicator and an air quality survey based on fine particulate matter (PM2.5) concentrations. The measured carbamazepine concentrations from ten coastal sites ranged from 0.01–0.11 ng/L (mean, 0.03 ng/L). These concentrations are markedly lower than those previously reported for the coastal waters of Tokyo Bay, indicating that the coastal waters of Niijima were minimally affected by domestic wastewater. This difference is primarily attributable to the small population and limited anthropogenic input from the island. Atmospheric PM2.5 concentrations on Niijima ranged from 4.0–11.1 µg/m3 (mean, 7.3 µg/m3), less than half the annual environmental standard for Japan (15 µg/m3) and substantially lower than the concentration measured during the same period in Ina Town, Saitama Prefecture (mean, 13.0 µg/m3). Chemical component analyses revealed that elevated PM2.5 concentrations in the metropolitan area during winter and summer were mainly associated with atmospheric stagnation and the long-range transport of secondary and combustion-derived particles, respectively. In contrast, Niijima is less influenced by these factors. Overall, the results demonstrate that both the seawater and air quality on Niijima Island are well preserved. This study provides scientific evidence of the environmental value of this region and highlights the importance of evaluating and disseminating data in areas with favorable environmental conditions.