Report on 25 years of cedar and cypress pollen observations—A study of regional differences and annual changes in Yamanashi—

Abstract

Recently, the prevalence of Japanese cedar pollinosis has been increasing, and it is a national disease in Japan. Yamanashi Prefecture has the highest cedar- and cypress-specific IgE antibody positivity rate and the highest cedar pollinosis prevalence in Japan. A major cause of the increase in prevalence is the increase in pollen antigens. In 1998, we started observation using Durham-type pollen collectors in several areas in Yamanashi Prefecture. Using pollen count data for 25 years up to 2023, we compared regional differences and annual changes and examined their correlation with weather conditions. Regional differences in pollen quantity reflected distance from the pollen source. Cedar pollen increased gradually. Cypress pollen showed differences in the increase rate depending on the region. Both correlated with sunshine duration and average temperature in the previous summer. However, no significant correlation was observed with weather conditions during dispersal. Cypress pollen quantity may increase in all areas in the future.