Relationship between Pollen Diseases and Meteorological Factors in Japan

Pollen counts have been increasing and patients suffering from pollen allergy now exceed 14% of the population of Japan. The amount of pollen has a positive relationship with the air temperatures and solar radiation of the preceding summer. Using this relationship, pollen counts of the next season are estimated roughly. According to the results of cedar flower observations in late autumn, the forecast is made more accurate. The warmer spring is, the earlier the pollen season starts. However, a warm winter results in a relatively late pollen season in the same regions of southern Japan, because warm winters disturb cedars’ dormancy. Cedar and cypress forests occupy 18% of Japan’s total land area. The pollen counts in 2050 are expected to be 1.6 times more and the number of patients to be 1.4 times than at present.