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Cedar pollen volume may hit 10-year high in parts of Japan: survey

Male cedar flowers are seen in this photo taken in February 2019 in Nagakute, Aichi Prefecture. (Mainichi)

TOKYO -- Hay fever sufferers beware: The amount of cedar pollen in spring 2023 could reach a 10-year high in some parts of Japan.

    The prediction is based on the Ministry of the Environment's November-December survey, which uncovered the most male cedar flowers in a decade in 12 prefectures.

    Male cedar flowers, which determine the amount of pollen dispersed in spring, tend to become more abundant when the previous summer (June to August) is warmer with longer hours of sunlight. The record high temperatures in late June and early July 2022 are believed to have had an impact on the latest figure.

    According to the Environment Ministry, a survey of male flowers in artificial cedar forests recorded the highest numbers per square meter in the past 10 years in Fukushima, Kanagawa, Niigata, Toyama, Ishikawa, Kyoto, Hyogo, Okayama, Tottori, Hiroshima, and Fukuoka prefectures, as well as in Tokyo.

    When the pollen discharge is high, the number of male flowers tends to fall the following year. In parts of the northern Tohoku and Shikoku regions, where the volume of cedar pollen dispersal was higher than normal in spring 2022 and which saw fewer hours of sunlight in June than an average year, the number of male flowers was smaller compared to in 2021.


    Note: The Ministry of the Environment on Jan. 18 corrected its earlier report that 14 prefectures had recorded the highest numbers of male cedar flowers in the past decade, and amended the list of prefectures. We have updated the article accordingly.

    (Japanese original by Ei Okada, Science & Environment News Department)

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