High and rising hay fever in Japan may now have a solution

Spring in Japan is long-awaited on many levels as the Sakura or cherry blossoms are in full bloom, eliciting one of the country’s most iconic sceneries. At the same time, the season’s allure is tempered as hay fever hits millions of Japanese, with those suffering from the seasonal allergy hovering above average levels.

What’s more, with the warming climate, those numbers are only getting higher and has led to the East Asian island seeking another leading flora-based phenomenon – to take the pollen out of plants.

The number of people affected by hay fever in Japan is a mighty 40%, as per 2019 figures. These figures sit above average global rates, which range between 10% and 30%, and as such, it has long been considered the East Asian island’s social problem.

For Japan, around 70% of hay fever afflictions are caused by cedar pollen, as cedar forests cover around 12% of Japan’s land mass and account for 18% of its forests.

Usually, cedar pollen dispersion begins in the Kyushu region in early February and peaks in March. The dispersal of cypress pollen, another major allergen, then peaks in April and those with allergic symptoms to both types of pollen suffer intense symptoms until around May

While common, hay fever symptoms vary, including sneezing, runny noses, congestion, itchy eyes and skin irritations. These symptoms can lead to poor sleep quality and reduced work performance and the impact on people’s daily lives and work cannot be underestimated. The Forestry Agency estimates that the total economic loss caused by hay fever, including medical expenses and labour losses, amounts to 286 billion JPY (around $2.2 billion) per year.

In Japan, such high incidences of hay fever have only become higher, with a 20% uptick over two decades. According to a survey by the Ministry of the Environment, the amount of cedar pollen scattered this year is expected to be the highest in the past 10 years in Japan.

Further afield, in an analysis of 60 pollen-collecting stations across the United States and Canada between 1990 and 2018, the pollen season starts 20 days earlier and eight days longer on average. There was also a 20.9% increase in the number and concentration of pollen released into the air over the year and when limited to the spring pollen season, the increase was 21.5%.

Therefore, globally, pollen allergies seem to be worsening each year and the reason for this upward trend is believed to be due to climate change. Pollen dispersal, which is carried by the wind, is closely related to changes in temperature and rainfall. As Spring temperatures rise, plants release pollen much earlier and for longer periods.

According to research published last month in Nature Communications, the amount of pollen produced during the US flowering season could increase by up to 40% by 2100. It also stated that the pollen season could start up to 40 days earlier and last 15 days longer.

Global warming is lengthening the growing season for organisms and, as a result, increasing the risk to human health from allergies. Even if forests and grasslands are reduced due to drought and heat, some grasses, weeds and trees that produce allergy-inducing pollen thrive on rising temperatures and higher carbon dioxide concentrations, growing larger and producing more leaves.

Against this backdrop, the Forestry Agency in Japan is working on expanding the production of pollen-less cedar and low-pollen cedar seedlings that produce almost no pollen. By 2019, 12.1 million pollen-free and low-pollen cedar seedlings had been produced, accounting for about 50% of total cedar seedling production. The Agency aims to increase that percentage to 70% by 2032.

At the core of these developments, particularly in efforts to further streamline the development of pollen-less varieties, there has been a need to understand more about the gene responsible for male sterility and its nucleotide sequence. However, it has been difficult to decipher the sequence because the cedar genome is 20 times larger than rice’s and has a more complex genome.

Thanks to recent advances in genome analysis technology, a Japanese research group consisting of the Forestry and Forest Products Research Institute and several universities, including the University of Tokyo, succeeded last month in deciphering a nucleotide sequence that covers all 11 chromosomes of the cedar tree.

The group also identified approximately 50,000 genes and their positions and constructed a “reference genome sequence,” a standard sequence representative of the species. That is expected to accelerate the development and breeding of useful pollen-less varieties and greatly help predict the evolutionary process of cedar and the effects of climate change.

Pollen dispersal forecasts and technological advances are certainly driving measures and initiatives to alleviate allergies. However, these are only coping mechanisms.

Really making a difference to the global environment that has led to such high pollen levels means going back to the root cause – climate change. Only the can we really make a significant difference to the global environment we live in.