Author(s)

Q. WANG, S. NAKAMURA, S. GONG, M. SUZUKI, D. NAKAJIMA, Y. TAKAI, S. LU, K. SEKIGUCHI & M. MIWA

Abstract

Japanese cedar (Cryptomeria japonica) pollinosis is the most popular pollinosis in Japan. In recent years, it was reported that the most Cryptomeria japonica pollen allergenic species were scattered as fine particles in the urban atmosphere. It is thought that allergenic fine particles are responsible for inducing asthma by breaking into lower respiratory tract; this phenomenon was observed in field investigations during sunny days after rainfall. Hence, it is considered that the release of fine allergenic species derived from pollen grains may be induced during rainfall events. For this reason, we investigated the releasing behaviour of Cryptomeria japonica pollen allergenic species in rainwater containing air pollutants, through rainwater sampling and laboratory experiments. The pollen grain counts, pollen burst ratios, ionic concentrations and pH in each rainwater sample were measured, when rainwater samples were separately collected in Saitama City, a suburban area north of Tokyo metropolis. Additionally, three simulated rainwater (SR) samples were prepared to investigate the releasing behaviour of pollen allergenic species. In the samplings, the most pollen grains were trapped into initial rainwater (IR). Moreover, burst pollen grains were observed in many rainwater samples. Burst ratio of pollen grains were positively correlated with pH and ionic concentrations in rainwater. Therefore, it was thought that pollen grains were washed out by IR containing air pollutants. On the other hand, for the laboratory experiments, the elution of allergenic Cry j 1 and Cry j 2 was observed when pollen grains were exposed to different SR samples. A time-dependent increase of Cry j 1 was observed, but the elution of Cry j 2 was not observed from pollen grains exposed to SR samples. In particular, the elution of Cry j 1 increased by contact with SR samples under conditions of Asian dust events. The results demonstrated that the burst of pollen grains is associated with the production of fine particles containing pollen allergenic species, and that the release of allergenic species was induced by rainwater containing air pollutants.

Keywords

Air-polluted precipitation, allergenic Cry j 1, allergenic Cry j 2, Asian dust, crustal particles, Cryptomeria japonica pollen, releasing