Evaluation of elution behavior and morphological change of the Cryptomeria japonica pollen grain and release of its daughter allergenic particles by air polluted rainfall

摘要

In Japan, Cryptomeria japonica pollen are scattered during each spring season. Daughter allergenic particles are released, which are smaller in size than their parent pollen grain and are abundant in a particle size below 1.1 μm in the atmosphere; nevertheless, Cryptomeria japonica pollen size is about 30 μm. Therefore, daughter allergenic particles of pollen are transported in the urban atmosphere for a long time after their release. In particular, the daily variation delays in the peaks of allergenic Cry j 1 concentrations of Cryptomeria japonica pollen compared with the peaks of airborne pollen counts were observed in high levels during one or two sunny days after rainfall. In addition, long range transportation of Asian dust from the East Asian continent, called yellow sand, was also found during the pollen scattering seasons in Japan, due to global warming. Therefore, the interaction between pollen and air pollutants, including yellow sand, should be of concern. Thus, in this study, the morphological change of Cryptomeria japonica pollen and the elution behavior of its allergenic contents (Cry j 1) were also investigated when in contact with simulated air polluted rain containing various crustal particles and/or secondary formed inorganic particles. As a result, pollen might burst at high humidity beforerainfall. Additionally, Cry j 1 was emitted from the so-called Ubisch body, which contains allergenic Cry j 1 abundantly when pollen is in contact with rainfall. In particular, we found that 60% of allergenic Cry j 1 contents released in air polluted rainfall contained Ca~(2+) ion derived from road dust and Asian dust. Therefore, rainfall should be a main reason to induce transition of pollen allergenic contents to fine particles. In conclusion, allergenic particles that are small sized and translated as fine particles by rainfall invade into the lower respiratory tract, which can contribute to the hypersensitivity of asthma.