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Climate change blamed for rise in hay fever

Tokyo

Spare a thought for Japan's myriad hay-fever sufferers as they endure the highest pollen levels on record this spring. Global warming seems at least partly to blame and most experts agree that the worst is yet to come.

Hay fever in Japan is more punishing than that triggered by weed pollen, which occurs in much of the rest of the world. It is caused by an allergic reaction to cedar and cypress pollen. Severe symptoms and the spread of pollen over wide distances is forcing thousands of people, even in urban areas, to don protective masks and glasses.

There are about 7 million hectares of cypress and cedar plantations in Japan. In Tokyo alone, about a quarter of the population is suffering from hay fever. And according to government surveys the number is steadily rising.

Kouji Murayama, a researcher at the Japan Meteorological Business Support Center in Tokyo, believes that the culprit is global warming. He points to studies that show a clear link between summer temperatures and the amount of pollen produced the following spring. Such data already provide the basis for pollen forecasts.

Fever pitch: many Japanese need protective masks to help them fend off the effects of tree pollen. Credit: S. BONESS/PANOS

Tokyo's average yearly temperature has increased by 3 °C since 1890 and, according to the Japan Meteorological Agency in Tokyo, is set to rise by up to 3.5 °C by the end of this century.

Based on this forecast, Murayama predicts that the number of hay-fever sufferers in Japan will rise 40% by 2050. “Global warming will continue to intensify what is already a serious health problem in Japan,” he says.

Many agree with Murayama's findings. “It's common sense,” says Atsushi Ueda, an allergy specialist at Kumamoto University. Ueda adds that higher levels of carbon dioxide and diesel-exhaust particles can also worsen the body's response to pollen.

But other scientists argue that economic factors may be to blame. Yoko Fukuda, a researcher at Japan's Forestry Agency, points to the decline in domestic forest industries, which has left the cedar and cypress plantations unmaintained. “Such neglect has allowed the trees to mature to their prime pollen-producing age,” he explains.

To comfort the hoards of sufferers, the Forest Tree Breeding Center is working on a plan to replace all the offending trees with pollen-free cypress and cedar. But this could take decades, and political support is still uncertain, says project leader Makoto Takahashi.

Despite the difficulties, scientists are determined to find ways to improve the situation — and to ease their own symptoms. Murayama's research was first motivated by his wife's hay fever. But after conducting studies in the forests, he has experienced the problem first hand. “I can now tell you all about the miseries of pollen allergies,” he says.

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Williams, R. Climate change blamed for rise in hay fever. Nature 434, 1059 (2005). https://doi.org/10.1038/nature03682

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