Meteorological conditions and pollen allergenicity

Meteorological conditions and pollen allergenicity
Fateme Mousavi,^1,*
1. 1Air & space Biology and Environment center, Aerospace Research Institute (ARI), Ministry of Science Research and Technology (MSRT)
Introduction: It is estimated that about 40% of people have some kind of allergy. The reason for this increase is attributed to environmental and climate change. Many airborne pollen grains released by tree, grass, and weed species can cause pollinosis in susceptible individuals with symptoms such as watery eyes, eye irritation, runny nose, skin irritations, dry cough, and sneezing. Meteorological factors such as temperature, humidity, rainfall can affect the release of allergens from pollen grains and its allergenic content. This review is aiming at producing relevant data that have been published on the influence of meteorological conditions on the allergenic potential of pollen grains.
Methods: In this paper, we conducted a scientific databases search using nearly 50 related scientific terms and keywords and summarized more than 20 scientific articles related to the relationship between Meteorological factors and the potential of pollen allergenicity.
Results: Pollen allergenicity is associated with allergen concentrations. Some studies have reported an increase in the pollen allergen content produced by plants grown at high temperatures and in carbon dioxide-rich atmospheres. Studies have also shown that the concentrations of the main allergen in ragweed (Ambrosia artemisiifolia), Amb a 1, increase in carbon dioxide-rich atmospheres. Global warming and rising temperatures are causing severe drought stress, especially in urban areas. In ragweed, a major allergenic species, the expression of allergenic proteins is upregulated under drought conditions. Also in a species of birch (Betul apendula), pollens from trees grown in the south (higher temperature) had the highest amount of allergenic proteins. The main allergen of Birch, Bet v 1, shows significantly more severe allergenicity in trees grown at higher temperatures. In another species of birch (Betula pubescens), a higher average daily temperature is associated with increased levels of the major allergen in birch pollen (Bet v 1). However, some studies have reported a negative relationship between Bet v 1 allergen content and temperature increase. Recent molecular studies have shown the temperature-dependent expression of the gene encoding the allergen Bet v 1. This study showed that high temperatures positively regulate the promoter activity of Bet V 1 gene. however, Recent studies indicate regional and year-to-year differences in the release of the Bet v 1 allergen from birch pollen. During the natural pollination period, mature pollen grains are dehydrated when released by the anthers at the time of dispersal. When pollen grains come in contact with a wet surface, they absorb water and undergo metabolic and ultrastructural changes. Pollen allergens are located in the pollen walls or cytoplasm and are rapidly released when pollen grains come in contact with the mucous membranes of the mouth, nose, and conjunctiva and causing pollen allergy symptoms in sensitive patients. Sometimes cytoplasmic allergens are located in the membrane around the starch grains, when pollen grains burst under osmotic stress, they are released into the atmosphere and can form a breathable allergenic aerosol. Birch pollen can explode in high humidity conditions and release an aerosol from the cytoplasmic components of the pollen (in the range of 30 μnm to 4 μm), which contains the allergen Bet v 1. Under high humidity conditions, about 65% of pollen grains form a 300 micrometer pollen tube before rupture and release of their cytoplasmic contents. The released particles form a very fine aerosol that can penetrate the lower respiratory tract and cause allergy symptoms. In 1985, a new link between thunderstorms and asthma outbreaks was identified, described as thunderstorm asthma. During thunderstorms, pollen grains may release some of their contents including starch granules containing an allergen (0.5-2.5 microns) or other cytoplasmic components into the atmosphere after bursting by osmotic shock. These starch granules can penetrate the lower respiratory tract and provoke asthma symptoms. Thunderstorm asthma is limited to late spring or summer when high levels of airborne pollen grains are present in the atmosphere.
Conclusion: In conclusion, Humidity and temperature seem to be two important factors affecting the release of allergens from pollen grain and its allergenic content. In light of this review, there is a growing body of evidence supporting the effect of meteorological conditions on the allergenic potential of pollen grains.
Keywords: allergy, pollen, pollinosis, Meteorological factors, allergen