Contribution of airborne fine particles containing Cryptomeria japonica pollen allergens to airborne organic carbonaceous aerosols during a severe pollination episode

摘要

Japanese cedar pollinosis has been recognized recently as a serious social problem because of its high prevalence in Japan. It is well-known that the pollen grains of Cryptomeria japonica pollen (so-called Japanese cedar pollen) usually exist as coarse particles about 30 μm. However, it was supposed that the major allergen Cry j 1 (Cry j 1 particles) could be released to the atmosphere as respirable-sized particles and modified by some air pollutants during airborne transportation. Cry j 1 particles represent major seasonal allergen sources and are suspected to cause pollen asthma. Moreover, since Cry j 1 particles mainly consist of protein materials and cytoplasm from the pollens, they should be organic carbonaceous aerosols in fine particle sizes because protein materials are also some kind of organic carbon (OC). Therefore, one of the Cry j 1 release processes in which Cry j 1 eluted from several simulated rainfalls of various salt components have been investigated. As a result, about 60% of Cry j 1 was released in simulated rain containing Ca~(2+) ions. At the same time, it is important to examine the release behavior of Cry j 1 particles and to evaluate the source contributions calculated from Cry j 1 particles to organic carbonaceous aerosols. The aim of this study is to examine the particle size distribution of Cry j 1 and OC in airborne aerosols to clarify some mechanisms provoking pollen asthma and to evaluate source contributions during a severe pollination episode of FY 2005. Airborne Cry j 1 particles were collected with high volume Andersen air samplers, and Cry j 1 and OC (OC1-OC4) concentrations were determined by the ELISA method and the thermal-optical carbon analyzer respectively. More than 80% of Cry j 1 existed as fine particles below 1.1 urn, which consisted of OC2, OC3 and OC4. Source contributions of OC derived from pollen may be averagely occupied ～30% in airborne organic carbonaceous aerosols as total OC in fine particles (PM_(1.1)) below 1.1 μm respectively. Thus, it was possible that OC contribution below 1.1 μm is overestimated by conventional concepts of various anthropogenic and secondary formed sources because Cry j 1 particles are also below 1.1 μm which are the composite OC sources released from pollen grains.