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Wednesday, May 25, 2022
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More pollen and more severe allergies due to climate change

Between 10% and 40% of the world’s population suffer from allergic rhinitis due to seasonal pollen exposure. With a pollen allergy, the most common symptoms are sneezing, itchy nose, and nasal congestion. Inhalation allergens can also exacerbate allergic bronchial asthma.

In addition, most food allergies mediated by allergen-specific immunoglobulin E (IgE) in adults occur after prior sensitization to aeroallergens. With climate change affecting natural ecosystems and crops, the incidence of allergenic pollen is subject to fluctuations, which can be dramatic and have a significant impact on public health.

Extreme weather events such as drought or heavy rainfall, wind gusts, thunderstorms and increased long-range pollen transport are new challenges in this scenario.

The heat and the abundance of pollen

Extensive research over the past decade has shown that airborne pollen has increased. Increased levels of sensitization and more severe symptoms are partly the result of increased pollen production from wind-pollinated plants, resulting in a long-term increase in airborne pollen.

There is strong evidence that plants produce more pollen earlier when temperatures are warmer, i.e. in urban areas, at lower altitudes, on southern slopes and during warmer periods.

In general, there is a positive correlation between allergic symptoms and pollen abundance. However, this relationship can vary significantly between different bioclimatic regions, between different patients, and for each type of pollen. And, of course, there is usually a different time delay between actual exposure to pollen and the onset of allergic symptoms.

The results obtained in the Netherlands indicate a strong correlation between temperature and the beginning of the pollen season: there is an advance and an increase in its duration. Earlier changes in airborne pollen seasons make it difficult to predict and effectively treat the onset of allergy symptoms.

A general advancement and extension of the pollen season, as well as an increase in concentration, have been observed throughout North America, which is closely related to the observed warming. The results of the study show that human-induced climate change has already exacerbated the pollen season over the past three decades, with subsequent harmful effects on respiratory health.

Extreme weather events and allergenic pollen

There is still great uncertainty about the expected rate of climate change, but it is clear that changes such as temperature extremes and precipitation will manifest themselves in increasingly significant and tangible ways.

International studies confirm that grass pollen is the leading aeroallergen worldwide. Climate change (increased aridity and frequency of extreme temperatures) that favors the spread of cereals and difficult steppes can increase the amount of pollen in the atmosphere.

An increase in average temperature, uneven precipitation and an increase in the amplitude of fluctuations favor the colonization of semi-natural habitats by invasive species. Agricultural lands abandoned due to loss of profitability as a result of climate change are also occupied by opportunistic invasive species.

The species Ambrosia artemisiifolia L. is an invasive and exotic plant in Europe. In addition, its pollen is highly allergenic. Initial estimates showed that ragweed sensitization in Europe would more than double, from 33 million people in 2020 to 77 million in 2060. The largest proportionate increase will occur in locations where sensitization is currently rare.

The link between thunderstorms and asthma

After a thunderstorm, acute asthma attacks often occur. Lightning discharges can concentrate aeroallergens (grass pollen) at ground level and release respirable allergenic particles after breaking due to osmotic shock associated with moisture and precipitation.

Inhalation of high concentrations of these aeroallergens by sensitized individuals can cause early asthmatic reactions followed by a late inflammatory phase.

Thunderstorms during pollen seasons can exacerbate respiratory allergies and asthma in hay fever sufferers. A similar phenomenon is observed in the case of mold. Detailed analysis has shown that this change will lead to more frequent conditions favorable to severe storms, but the interpretation of how individual hazards will change is questionable.

transport of pollen over long distances

There are examples of pollen transport over long distances. Several cases of out-of-regional transport of pollen have been reported in Tenerife (Canary Islands). The three main origins were:

In Tenerife, sporadic cases of long-range transport of pollen should be taken into account as possible agents responsible for episodes of respiratory allergy.

Long-range transport of pollen to southern Greenland was recorded during the last two weeks of May 2003. The results indicate that northeastern North America is an area of ​​origin for transported pollen grains, related to the timing of the maximum flow of pollen released into the atmosphere in the area of ​​origin.

fog and mist

In Beijing, heavy fog episodes are associated with reduced winter northerly winds near the surface, weakening northwesterly winds in the middle troposphere, and increased thermal stability in the lower atmosphere.

It is not clear how these weather patterns might respond to climate change, although a 50 percent increase in the frequency and an 80 percent increase in the duration of good weather is predicted.

The Sahara produces more wind dust than any other desert in the world. The dust of the Sahara has an important influence on climate processes, nutrient cycles, soil formation and sediment cycles. This influence extends far beyond Africa due to the long distances traveled by Saharan dust, affecting the respiratory health of the population, which is affected not only by mineral particles, but also by the pollen associated with them.

Changes in pollen allergenicity

The allergenicity of pollen depends not only on the allergen itself, but also on the factors affecting the pollen. Thus, exposure to allergens is necessary but not sufficient for the development of an allergy.

Pollen releases a wide range of biologically active substances such as sugars, lipids, secondary metabolites and hormones. In particular, these bioactive mediators bind to receptors on human immune cells, potentially promoting allergic sensitization to pollen-derived proteins or amplifying allergic immune responses already present.

In addition, temperature has a direct effect on allergen release, as evidenced by year-to-year variability in a study of birch pollen in Germany.

This article was originally published on Talk. you can read it here.


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