Respiratory Allergies, Asthma and Rhinitis Increase Due to Climate Change

Aeroallergenic particles accompany us everywhere. Wherever we are, they are present in every breath. Suspended in the air that we inhale, hundreds of aeroallergens roam from one place to another and although they seem harmless, they are responsible for several respiratory diseases. Recent studies reveal that climate change influences the exposure of these microscopic particles, exacerbating the development and progression of allergic reactions.

In recent decades, an increase in the global incidence of respiratory allergies has been observed, especially those that affect the upper airways (allergic rhinitis) and lower airways (atopic asthma). According to the World Allergy Organization (WAO), it is estimated that more than 350 million people worldwide suffer from asthma. Likewise, about 10 to 50% of individuals manifest symptoms consistent with allergic rhinitis. Far from being isolated problems, these conditions are more common than previously thought.

Small but dangerous

There is a wide variety of allergens that cause asthma and allergic rhinitis. Pollen is one of them and certainly the most common. Under this generic term, different types of grains produced by numerous plants are grouped, with allergies to pollens specific to each one of them. In this way, we will find people allergic to citrus pollen who tolerate grass pollen without problems, or those allergic to mugwort pollen who do not react to olive pollen, among other possibilities.

With the rebirth of flowers, plants produce diversity of pollens. Some are pollinated by insects and others simply by the wind. In particular, the latter are the ones that trigger respiratory diseases by releasing a significant amount of allergens into the environment.

Small and light, pollen grains are capable of traveling tens of kilometers from their point of origin. No one is safe, regardless of whether they live in a city or a rural area. Whatever the case, the season of greatest risk for people sensitive to pollen is spring, in the case of areas with seasons, when the concentration of this allergen in the air reaches its highest peaks. Even so, with slight ups and downs, the pollination period is variable and depends on each species, so these substances usually cause complications throughout the year.

To this is added that the variations of pollen in the air do not respond to a single environmental factor. Temperature, humidity, wind, light intensity and precipitation intervene, to a greater or lesser extent, on the bioavailability of this airborne species. Ultimately, all these variables contribute to the reproductive success of plants. A function that is a priority for any living organism on the planet. In this framework, it is not surprising that the production, release and dispersion of pollen fluctuate around optimal meteorological conditions. But yes, antagonistically, we must reflect on the possible consequences of climate change on human health.

Climate change: green light for pollen

To put it in raw numbers, the National Office of Oceanic and Atmospheric Administration (NOAA, in English), located in Colorado, United States, reported about a 48% increase in the concentration of CO2 in the atmosphere since the beginning of the revolution industry to the present. At the same time, this research center on greenhouse gases highlighted that the increase in CO2 brought about a rise in global temperature equivalent to 1.8°C. Although this figure seems lower, the effects of small changes in temperature are by no means negligible. Prolonged increases in temperature destabilize the delicate natural balance and predispose to a myriad of phenomena that affect general well-being.

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Now, how do these climatic changes affect pollen and allergies? Prior to the dispersion of this aeroallergen, CO2 and temperature play a fundamental role in its production and release. For starters, high temperatures change flowering times. Combined with elevated CO2 levels, pollen seasons are prolonged and the amount and allergenicity of grains are increased, according to a Nature Communications article published this year.

Once the pollen is in suspension, other environmental factors take over the scene. Precipitation, in particular, can favor the deposition of the allergen on the ground, giving allergy sufferers a real break. However, the rains also generate the opposite effect. Known as thunderstorm asthma, heavy rainfall breaks pollen grains into tiny particles, which given their size and concentration in the air can cause intense inflammatory symptoms in sensitized individuals. In this regard, a publication in the journal Lancet, from 2022, indicates that the risk of asthma episodes due to storms is likely to increase in the future, since climate change predisposes to erratic weather patterns and greater pollen bioavailability.

It is not a myth but pure reality. The planet's climate is changing and has an ever-increasing impact on our lives. In this sense, speaking of acute respiratory allergies due to longer and more intense pollen seasons constitutes a small part of a much more complex phenomenon that must be made visible and tackled together.