6 days ago
China's ‘green great wall' triggers hay fever misery: scientists
For Ma Bo, a resident of Hohhot, the capital of Inner Mongolia, late July marks the beginning of another round of suffering.
He has suffered from hay fever – an allergic condition triggered by inhaling pollen – for many years. His symptoms have gradually worsened since 2018, progressing from sneezing and conjunctivitis to an allergic cough and, eventually, bronchial asthma.
The artemisia plant, which is widely cultivated in northwestern China to contain wind and sand erosion, has been identified as the trigger for his symptoms. Its pollen is particularly active from late summer to mid-autumn.
This resilient plant contributes to the 'green great wall' – the weapon across the arid northern region that China uses to fight desertification – but it is also suspected of causing an increasingly concerning endemic hay fever outbreak.
Now, after years of research, a group of Chinese scientists have confirmed the plant's role in causing the disease at a molecular level and identified several allergenic substances in its pollen.
For the first time, the team has identified five volatile components from a member of the artemisia plant family, confirming they could all trigger allergic reactions. These findings 'provide a basis' for preventing and treating allergic diseases in areas where the plants are grown, according to a report in the state-owned newspaper Science Daily on Monday.
The study, which was conducted jointly by scientists from the school of pharmacy at Xian Jiaotong University and the Yulin Forestry Science Research Institute – both in northwestern China's Shaanxi province – was published in the Journal of Hazardous Materials at the end of May.
Artemisia, which has more than 100 species, is easy to grow and has low cultivation costs. However, according to a 2023 report by the Health Times, a subsidiary of People's Daily, its pollen has become a common allergy cause in northern China.
Over the past years, what has unfolded in Yulin – a city in the northernmost part of Shaanxi province – is a prime example of how well-intentioned efforts to transform harsh natural environments can induce unexpected side effects.
Yulin, situated at the confluence of the Mu Us Desert and the Loess Plateau, was once among the country's worst affected by land desertification. Large-scale planting of sand sagebrush, an artemisia species, began in the 1950s. This measure has proven highly effective, with the Mu Us Desert steadily shrinking and Shaanxi's green landscape expanding northwards by 400km (250 miles).
However, residents reported that allergies had become more common. A preliminary survey conducted in 2019 by Yulin health authorities in collaboration with Peking Union Medical College Hospital found that pollen from sand sagebrush was the main cause of allergic rhinitis in the region.
In 2023, the ongoing prevention and control of allergic rhinitis was listed by the local government as the top priority for improving livelihoods.
He Langchong, a pharmacy professor at Xian Jiaotong University who was born in Yulin, decided to take action. Starting in 2022, he and his team lived in Yulin and worked with with a local research institution to launch a long-term 'allergen tracking campaign'.
Allergies are an overreaction of the immune system to specific substances. When allergens in the air enter the human body, they bind to specific receptors and trigger allergic symptoms.
By developing an allergen gas analyser and conducting a systematic screening of plant samples, the researchers identified five volatile components. They further discovered that these components could significantly activate mast cells via a receptor called MrgX2, leading to allergic reactions. Mast cells generally aid in normal immune system function.
Additionally, by measuring changes in the content of these volatile components in plant samples taken in different months, He and his colleagues found that the total content increased gradually as the plants grew, reaching much higher levels in August and September than in other months. This pattern closely aligns with the onset of the hay fever peak season in Yulin.
Once allergens are identified, they can be monitored and the public can be advised on appropriate protective measures, according to Science Daily. In the meantime, anti-allergy drugs targeting this specific allergen can be developed based on the findings.
Shaanxi is not the only province where people are hit with the condition. Ma Bo, the resident of Hohhot, estimates that more than 30 per cent of people around him are affected. He said there was no specific treatment available, only a plan to manage symptoms.
And a resident of Lanzhou, in the northwestern Chinese province of Gansu, told the South China Morning Post he had suffered from hay fever for more than 10 years. His symptoms started in autumn each year and include severe sneezing, watery eyes and facial swelling.
In China, a forestry and grassland bureau official from Yulin admitted in a 2020 newspaper interview that the public health issue caused by sand sagebrush planting had taught officials 'a profound lesson'.
'In future desertification control efforts, we have fully considered plant diversity and potential impacts on residents' lives,' he said. - SOUTH CHINA MORNING POST
