Changes of Pollen Allergens in Northern China.

Background: Allergic rhinitis (AR) is a significant global health issue, with pollen allergens being a major cause of seasonal AR and asthma. In northern China, the prevalence of pollen-related allergies is notably higher than in the south due to higher pollen levels. Over the past few decades, climate change and urbanization have considerably transformed pollen profile in northern China.

Summary: Northern China experiences two annual pollen peaks: a spring peak (March to May) dominated by tree pollens (e.g., Cupressaceae, Ulmaceae) and a summer/autumn peak (August to September) dominated by weed pollens, particularly from Artemisia, Humulus, and Chenopodiaceae. Climate change has accelerated the onset of flowering periods, increased pollen production, and extended pollen seasons, with extreme weather events and air pollution further exacerbating pollen production and sensitization. Urbanization has increased tree pollens, resulting in spring peak pollen levels gradually exceeding those of summer/autumn in most northern regions. As ecological construction concepts have advanced, the selection of plant species for the shelterbelt and ornamental trees in cities has evolved, leads to changes in the dominant pollens in the north and northeast. Artemisia has been extensively planted in the Northwest for windbreak and sand fixation purposes, resulting in a significant rise in Artemisia pollen levels and sensitization rate with a widespread influence across northern China.

Key messages: Pollen allergens in northern China are a major driver of AR and asthma, with two distinct seasonal peaks. Changes in pollen profiles are influenced by natural factors such as geographical location and climate change, as well as social factors, including urbanization, national policies, and urban planning. In northern China, Spring pollen is predominantly composed of tree pollens, significantly influenced by urban planning across different regions. In contrast, summer and autumn pollen is primarily dominated by weed and grass pollens, with weed pollens exhibiting strong allergenic potential and widespread dispersal. The Northwest region is a major potential source for these weed pollens.