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Inhabitants of Bogotá, more exposed to noxious particles with the massive transport system

According to data from the World Health Organization (WHO), nearly 4 million people prematurely die annually; most deaths are attributed to particulate material exposure of PM2.5 present in the atmosphere of cities in a solid or liquid manner (dust, ash, soot, metallic particles, cement, and pollen among others.)

The limit values established by the WHO are three: material with particle size over 10 microns; less or equal to 10 microns –known as PM10– en less than 2.5 microns, or PM2.5. The latter is the most important in urban pollution as it causes cardiovascular and respiratory diseases, besides cancer.

Universidad Nacional de Colombia (UNal) Department of Chemical Engineering Professor Luis Carlos Belalcázar, says that after a few hours during the day inside the mass transit system the areas turn into a key location to measure certain levels of exposure faced by users.

Read more: Fog is not always a sign of pollution.

The project carried out by Universidad Nacional de Colombia (UNal), Universidad Sergio Arboleda, and the Universidad  Nacional Abierta y a Distancia (UNAD) showed that in the capital city of Colombia the passengers of the mass transit system known as TransMilenio are 10 times more exposed to inhaling noxious particles that in the Medellín Metro System.

How was pollution measured?

In Bogotá, the research team focused on several well-transited highways and streets (calle 80, Caracas, Autopista Norte, Norte-Quito-Sur [NQS], and calle 26). In Medellín, they carried it out in the Valle de Aburrá Transport Comprehensive System (Sistema Integrado de Transporte del Valle de Aburrá-SITVA) and also the Metro, Metrocable, and Streetcar (electrical) and Metroplús BRT systems, the latter which runs on natural gas.

Professor Belalcázar says that when they did the research the TransMilenio buses still had not been renovated; of the 39 buses analyzed, 30 ran on Euro IV or less technology, i.e. that were on the limit or lower the acceptable emissions according to the European emissions standard.

He also says they carried out two types of measurements, a manual which consists of collecting samples during several hours at a location and then in the lab they weighed the filter that captured the particulate matter, and compared with the weight before the measurements and based on that data and the airflow that passed through the equipment during measurement, concentration was calculated.

The other type of measurement was using a DustTrak automatic machine that measures the concentration of particulate matter in real-time and the data obtained during the route is later processed by computer. In this form, they obtained more than 80 hours of measurements, which translated into 17,000 PM2.5 data for every transit route.


Read more: Why does microplastic pollution increase during a pandemic? (In Spanish)

The findings

Once the information was processed they concluded that personal exposure does not only depend on the type of bus and antiquity, but also on what occurs around, such as street geometry, and the distance of the bus with normal cars. Belalcázar says that “We see that the Caracas Avenue in Bogotá is very closed, it has poor ventilation, is surrounded by high buildings and buses share the street with trucks and motorcycles, which influences the amount of contaminating material that people breathe inside the buses.”

The WHO has determined that the maximum daily concentrating of PM2.5 to which a person may be exposed without imminent danger is 25 micrograms per cubic meter. However, measurements of the research projects in Bogotá showed that the figure reached 300 micrograms per cubic meter, while in Medellín it did not surpass 50 micrograms per cubic meter.

In Medellín the system is fed by electricity, therefore the variation is less, and in the areas where BTR buses travel the same lanes with automobiles, the concentration is up to 3 times those measured in the same bus but in exclusive transit lanes.

“The results of this project could be fundamental for determining massive transit public policies. The data obtained allow observing that it is not only necessary to renovate the vehicles–as was done in Bogotá, where most buses now have Euro V and Euro VI technology–, but also intervene the vehicles that run around the transport system,” said Belalcázar.

Furthermore, he says it’s not only about a technical issue but also a political issue, to the extent that if maintenance is not carried out correctly, having less polluting technology will end up having the same problem; therefore there needs to be strict controls and this policy is still unclear for Bogotá and the rest of the country for that matter.

“The best option is renovation but thinking on the long-term, even if this implies greater investment. We need not only to think on the vehicle life cycle, but also on the healthcare cost of those that will get sick due to the emissions and on the impact to the environment for the use of fossil fuels,” said the researcher.

Comprehensive assessment

The research group hopes that when the mobility limitations due to the pandemic allow, they can research to measure the exposure to these particles in other transportation systems such as the Cali transportation system known Masivo Integrado de Occidente (MIO) or the Bucaramanga and Barranquilla transportation system  (Metrolínea and Transmetro, respectively).

For now, they are currently working on a methodology to assess factors such as the costs of direct transportation means and direct and indirect emissions; an example of which are electric vehicles, that although they do not produce emissions through the exhaust pipe, they do when the batteries are produced or at the sources where energy is produced.

In this respect, the expert said, “We are now promoting electric vehicles and assume emissions are zero, but this is not true as there are cases where electricity comes from thermoelectric power plants that burn coal and other fuels and that also have environmental consequences we need to consider.”

Lastly, he insists they need to advance to try to understand the best option available for the city conditions, be it shared automobiles, motorcycles, TransMilenio highways, or electric streetcars, and emphasizes overcoming the deficit of such research projects.



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