Thursday, May 19

More pollen and more severe allergies due to climate change


Between 10% and 40% of the world’s population is affected by allergic rhinitis due to exposure to seasonal pollen. In pollen allergies, the most common symptoms are sneezing, itchy nose and nasal congestion. Inhaled allergens can also cause an exacerbation of allergic bronchial asthma.

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In addition, most allergen-specific immunoglobulin E (IgE)-mediated food allergies in adults follow prior sensitization to aeroallergens. In a context of climate changewith an impact on natural ecosystems and crops, the incidence of allergenic pollen is subject to variations that can be drastic and have a considerable impact on the health of the population.

Extreme weather events, such as drought or severe rainfall, gusty winds, electrical storms, and increased episodes of long-distance pollen transport represent new challenges In this stage.

Heat and abundance of pollen

A extensive research conducted in the last decade has shown that airborne pollen has increased. Increased sensitization rates and more severe symptoms have been partially the result of increased pollen production from wind-pollinated plants, which has led to a long-term increase in the abundance of pollen in the air we breathe.

There is strong evidence that plants produce more pollen and earlier when temperatures are higher, that is, in urban locations, at lower elevations, on south-facing 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 variable time lag between actual exposure to pollen and occurrence of allergic symptoms.

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

A general advance and prolongation of the pollen season and an increase in concentrations have been observed throughout North America that are strongly coupled to the observed warming. The results of the study reveal that the climate change due to humans it has already exacerbated pollen seasons in the last three decades, with consequent deleterious effects on respiratory health.

Extreme weather events and allergenic pollen

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

international research documents that grass pollen is the main aeroallergen worldwide. Climate changes (increase in aridity and in the frequency of extreme temperatures) that favor the extension of grass and composite steppes can increase the amount of pollen in the atmosphere.



The rise in average temperature, the irregularity of rainfall and an increase in the amplitude of oscillations favor the occupation of semi-natural habitats by invasive species. Agricultural land abandoned due to loss of profitability as a result of climate change is also occupied by opportunistic invasive species.

the species Ambrosia artemisiifolia L. is in Europe a invasive and exotic plant. In addition, its pollen is highly allergenic. Primary estimates indicated that ragweed sensitization will more than double in Europerising from 33 million people in 2020 to 77 in 2060. The largest proportional increases will occur in places where awareness is currently rare.

Relationship Between Thunderstorms and Asthma

After thunderstorms it is common for acute asthma attacks to be triggered. Thunderstorm discharges can concentrate aeroallergens (grass pollen) at ground level and release respirable allergenic particles after rupture by osmotic shock related to moisture and precipitation.

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

Thunderstorms during pollen seasons can cause an exacerbation of respiratory allergy and asthma in patients with hay fever. a similar phenomenon observed in the case of molds. An Detailed analysis has suggested that the change will lead to more frequent environments favorable to severe storms, but the interpretation of how individual hazards will change is open to question.

long-distance pollen transport

There are examples of long-distance pollen transport. There have been several episodes of transport of extra-regional pollen to Tenerife (Canary Islands). The three main origins were:

Sporadic long-distance pollen transport events must be taken into account in Tenerife as possible agents responsible for episodes of respiratory allergy.



During the last two weeks of May 2003, transport of pollen to long distance south of Greenland. The results indicate that northeastern North America is the area of ​​origin of transported pollen grains associated with a time of maximum flux of pollen emitted into the atmosphere in the area of ​​origin.

The haze and the mist

in Beijingepisodes of severe haze are associated with a reduction in winter northerly winds at the surface, a weakening of northwesterly winds in the middle troposphere, and an increase in the thermal stability of the lower atmosphere.

It is not clear how these weather conditions may respond to climate change, although a 50% increase in the frequency and 80% increase in the persistence of favorable weather conditions is projected.

the sahara it produces more wind dust than any other desert in the world. The saharan dust it has an important impact on climatic processes, nutrient cycles, soil formation and sediment cycles. These influences extend far beyond Africa, thanks to the great distances that the Saharan dust travels, affecting the respiratory health of populations affected not only by the mineral particles but also by the associated pollen.

Changes in pollen allergenicity

The pollen allergenicity it is not only the result of the allergen, but also of the contributing factors of the pollen. Thus, exposure to allergens is necessary, but not sufficient for allergy development.

Pollens release a wide range of different bioactive 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 enhancing already manifested allergic immune responses.

Likewise, temperature seems to have a direct effect on the release of allergens, as revealed by the interannual variability in a birch pollen study in Germany.

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



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