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By: Carlos Olimpo Restrepo S. Journalist at UdeA Communications Department  

A study conducted by the Botanical Studies Group and the Clinical and Experimental Allergology Group, both at the Universidad de Antioquia, showed that the air in this area of the department contains high pollen concentrations, similar to those recorded in temperate zones around the world. The research also showed that several species in the city's atmosphere can cause allergies and clinical symptoms in the population. 

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Pollen from Cecropia peltata, the trumpet tree commonly known as yarumo, is one of the trees with the highest incidence of respiratory allergies among the inhabitants of Valle de Aburrá. Photo: Alex Espinosa   
 
Every time we breathe, we fill our lungs with air—an average of half a liter per inhalation at rest in an adult—an unconscious act with which we obtain the oxygen necessary to keep our bodies alive. We also inhale different pollutants derived from human activities, especially in cities, many of them in the form of particulate matter, technically called PM. In addition, pollen particles enter our bodies. 

For this reason, Professor Fernando Alzate Guarín, from Universidad de Antioquia’s Biology Institute, does not hesitate to say that "breathing is dying a little" when presenting the results of a doctoral study on biological contamination in the air of Valle de Aburrá. It was carried out at Universidad de Antioquia for more than five years, and researchers from the Botanical Studies Group (GEOBOTA), attached to the Faculty of Exact and Natural Sciences, and the Clinical and Experimental Allergology Group (GACE), of the Faculty of Medicine, participated. 

Alzate, PhD in Biology and coordinator of GEOBOTA, supported the work proposed in 2019 by Alex Espinosa Correa, a biology PhD student at UdeA. Espinosa was struck by the limited research on biological air pollution in Colombia. Allergists from the Faculty of Medicine, UdeA’s GACE group, and Hospital Alma Máter, where the clinical component of this research was analyzed, also participated in the project.  

Some of the findings of Espinosa Correa’s doctoral thesis "Aerobiological study in the city of Medellin, Colombia: A biological variable of air quality in a highly polluted city" are now available in the palynology and aerobiology scientific journal Grana and the environmental journal Science of the Total Environment. 

During the sampling period, 26 types of pollen were identified, among which the most abundant was that of the Cecropia family. Three distinct concentration patterns were observed: One characterized by a single peak between November and March, associated with three specific plant families; another showing two peaks—one between December and January, and another between April and September—linked to multiple families; and a third pattern exclusive to Cecropia, which exhibited three peaks occurring in December–January, April–May, and July–August. 

"The presence of pollen particles in the atmosphere is not considered by local authorities as a factor in declaring air quality emergencies or establishing public health policies," Espinosa Correa noted. 

The collection of air samples began in June 2019 and concluded in September 2022. A Hirst-type sampler or collector was used. It draws air through a hole and carries it to an adhesive film, where the particles that come from the atmosphere remain. The sampler was installed on the University Research Headquarters (SIU) terrace, in downtown Medellin. In this way, between 25 and 30 kilometers around are covered, which meant that the air was analyzed in most of the municipalities of Valle de Aburrá. 

An environment full of pollen all year round 

Alex Espinosa Correa's research established that "the pollen grain load in the atmosphere of Medellin ranges between 43,608 and 51,536 grains per day and per cubic meter, which represents higher values than expected, and similar to those recorded in temperate zones of the world, where there is supposed to be a higher pollen load." 

Furthermore, the big difference is that this phenomenon is permanent in Aburrá, not seasonal as in the temperate regions of the north and south of the planet. These are between the tropics and the poles and have a defined regime of four seasons per year. 

According to the student, "Daily concentration peaks were observed in the months following the rainy seasons, primarily between December and January and July and August, while hourly concentration peaks occurred around midday." However, at night, generally starting around 10:00 p.m., pollen emissions from one plant in particular, the yarumo, increase. 

This native species, whose scientific name is Cecropia peltata, together with the breadfruit tree, Artocarpus altilis, native, and the ash tree, Fraxinus uhdei, introduced into the country in the 1980s, produce the greatest sensitization and clinical symptoms in Valle de Aburrá, that is, they cause allergies. "Twenty-six different pollen types were identified and described throughout the sampling period," reported Alzate. 

Espinosa Correa emphasized, "Medellín has a large amount of pollen grains in the air all the time, and many of these can cause problems for some allergic people, who must be incapacitated by the health system, but these grains haven’t been identified yet as a constant public health problem here." 

“Identifying most pollen types in the atmosphere, in this case from Valle de Aburrá, will allow us to produce extracts to apply to patients and provide a more accurate diagnosis, and therefore, a better treatment», emphasized Alzate.  
 
This Hirst sampler was on the terrace of the University Research Headquarters for more than three years to collect pollen samples from Valle de Aburrá. Photo: Alex Espinosa 

A very important step for medicine 

The research involved both biological and clinical components. Allergists from Hospital Alma Máter and UdeA’s Faculty of Medicine, in collaboration with experts from Universidad del País Vasco, evaluated the impact of pollen on patients with allergies. 

This multidisciplinary approach allowed the researchers to identify the types of pollen and directly correlate them with allergic symptoms in the population. 

Dr. Ruth Helena Ramírez Giraldo, pediatrician and clinical allergist, coordinator of the Allergology postgraduate program, stated that, unlike Europe and the United States, where pollen is the main source of allergic diseases, the main cause in Colombia is usually mites. 

Although Colombia has many herbs and trees also found in temperate zones of the Earth, "We must keep in mind that our plants behave differently from those in Europe or the United States (...). Most of the pollen grains we breathe are ours, and we are a very different population in genetic terms from other populations of the world, and that is probably why we react differently to this situation," added Ramírez Giraldo. 

The coordinator of the specialization in Clinical Allergology at UdeA is talking about studies conducted before the one mentioned in this article. They indicated a lower prevalence of pollen allergies in Colombia—between 12% and 15% of the affected population—compared to other latitudes, which range from 40% to 60%, and current research does not show substantial changes in this aspect. 

In this regard, allergist Jorge Sánchez, a doctor at the Hospital Alma Máter and professor at UdeA’s Faculty of Medicine, stated, "The results from this research have changed our understanding of the problem. They have taken us away from the notion that the problem lies only in the types of pollen we have. There also seems to be something related to the population." 

He added, "This suggests another hypothesis worth studying. Maybe the high and constant exposure to different types of pollen resulted in a high tolerance to them, which is a protection against allergies." 

Allergies, a problem with different sources 

Humans can suffer allergies from different sources, such as insects and other animals, food, and elements present in the air, such as chemicals and pollen, which is the focus of the research by UdeA scientists. 

Researchers calculate that each person in Valle de Aburrá inhales an average of 63 pollen grains per hour, but this is not easy to see with the naked eye, as pollen grains range in size from 10 to 150 microns, depending on the species. For illustration, a human hair is, on average, 75 microns thick. For people who are intolerant to any of these elements, a single pollen grain is enough to trigger an allergy. 

"The allergies most associated with pollen grains are respiratory allergies: allergic rhinitis and asthma. In countries with seasons, these are called seasonal rhinitis and asthma. However, for us in the tropics, they can be perennial," explained Dr. Ruth Helena Ramírez Giraldo. 

The professor and researcher pointed out that patients diagnosed with or suspected of having pollen-related allergies should be referred to allergists to be tested and identify the causative allergen. 

"Doctors diagnose allergies in the country with kits of exotic pollen, usually from Argentina, Spain, or North America. Many people get negative results because there are no samples from here. That's why we needed to know what types of pollen are floating in the atmosphere of Medellin," said Fernando Alzate Guarín. 

In this regard, Dr. Jorge Sánchez added, "If we have the capacity to produce extracts from sources found in our environment, we will have scientific independence and will not depend on imported products. Furthermore, there are some plants that we only have here, and that's why it's very difficult to get these products in other parts of the world."