Allergen aerosol from pollen-nucleated precipitation: A novel thunderstorm asthma trigger

Artemisia pollen is an important allergen source of respiratory allergy in Beijing, China. However, there are few pollen stations using Burkard pollen traps in Beijing, and few reports on Artemisia pollen. This research is to analyze annual, daily and diurnal variations in Artemisia pollen concentration in four monitoring stations of Beijing during 2015–2018, and then to investigate their affecting factors. Artemisia pollen season starts in late July or early August, and ends in late September and early October. Daily peak appeared in late August or early September, and diurnal peak emerged during 06:00 - 10:00 or 17:00 - 20:00. Difference in vegetation coverage between urban (less than 1%) and suburban (27.2%) stations within 500 m greatly determined difference in SPI (Seasonal pollen index) between urban and suburban. Temperature and rainfall in the period prior to pollen season, together with the frequency and wind speed of dominant wind direction were responsible for annual variations of SPI. On a daily timescale, temperature was the most important factor influencing pollen concentration, explaining 18.6–43.9% of variance. In the course of the day, increase in temperature and decrease in relative humidity contributed to dehiscence of the anther in the early morning, leading to diurnal peak after sunrise. Wind may dilute or give a rise to the locally released pollen grains depending on the wind speed. High-intensity rainfall (intensity: > 2 mm h^-1) had washing-off effects on pollen concentration in the atomosphere, Besides air masses originated from the southerly, northerly and northwesterly directions influenced daily pollen peak by long-range transport. Multiple regression model for each station was constructed to predict daily pollen concentration using previous pollen concentrations and previous meteorological variables in three years, explaining 51.8–75.3% of variance.

Allergies are complex diseases that result from interactions between multiple genetic and environmental factors. However, the increase in allergies observed in the past decades is explained exclusively by environmental changes occurring in the same period. Presently, the exposome, the totality of specific and nonspecific external environmental exposures (external exposome) to which a subject is exposed from preconception onward and their consequences at the organ and cell levels (internal exposome), is being considered to explain the inception, development, and exacerbations of allergic diseases. Among the best-studied environmental factors of the specific external exposome, indoor and outdoor aeroallergens and air pollutants play a key role in the etiopathogenesis of the inflammatory response to allergens and in clinical manifestations of allergic disease. Climate change, urbanization, and loss of biodiversity affect sources, emissions, and concentrations of main aeroallergens and air pollutants and are among the most critical challenges facing the health and quality of life of the still increasing number of allergic patients today and in the coming decades. Thunderstorm-related asthma is a dramatic example of the effects of combined environmental factors and an in vivo model for understanding the mechanisms at work in respiratory allergy. Environment- or lifestyle-driven aberrancies in the gut and skin microbiome composition represent key mediators of allergic diseases. A better knowledge of the effect of the external exposome on allergy development is crucial for urging patients, health professionals, and policymakers to take actions to mitigate the effect of environmental changes and to adapt to them.