The conclusions of the study, which the Lusa agency had access to, shows a decrease in traffic in Lisbon due to the effects of the measures associated with Covid-19 and were developed by CENSE - Centre for Research in Environment and Sustainability of the Faculty of Science and Technology (FCT) at Universidade Nova de Lisboa.
Researchers from CENSE / FCT Universidade Nova would assess the concentrations of nitrogen dioxide measured at five air quality monitoring stations in Lisbon managed by the Lisbon and Vale do Tejo Regional Coordination and Development Commission in order to assess the impact that isolation measures associated with Covid-19 are having in reducing air pollution, especially road traffic.
The analysis focused on the “history of five monitoring stations in Lisbon, three traffic stations (Avenida da Liberdade, Entrecampos and Santa Cruz de Benfica) and two in the background, the latter with lower concentrations, but representative of a greater area of influence”.
“Based on the analysis of ten working days, between 16 and 27 March inclusive, it is possible to conclude that with regard to the comparison of the working days of the last fortnight with the total of working days in the year 2019, the reduction of pollution varies between 21 percent in Restelo, an area usually with better air quality, 56 percent in the case of Avenida da Liberdade and 58 percent in Entrecampos”, according to the study.
In the analysis carried out, the researchers also concluded that in the last week, on working days, on Avenida da Liberdade, nitrogen dioxide levels were 60 percent below the annual average of 2019 working days and was the week with the lowest concentrations of the last seven years.
The average concentration of 23 mg / m3 (micrograms per cubic metre) is close to half the limit value for the annual concentration, which is 40 mg / m3.
It was also possible to conclude that between the first and the second week with restrictions in force, there was a reduction of concentrations of 15 percent in Avenida da Liberdade and of 25 percent in Entrecampos and Olivais.
“Despite the variability that meteorological conditions always introduce in the analysis of the data, as time progresses it is possible to confirm with greater robustness one of the few positive aspects that the current pandemic is having”, is highlighted.
According to the researchers, the measured nitrogen dioxide is mainly a direct consequence of the combustion processes of vehicles, especially those using diesel fuel, which have higher emissions than gasoline vehicles.
Speaking to Lusa, Francisco Ferreira, professor in the area of air quality at FCT at Universidade Nova and president of the environmental association Zero, explained that the pollutants that reach higher concentrations in cities, particularly in Lisbon, are nitrogen dioxide and inhalable particles.
“It is known that there is a direct relationship between the susceptibility of the population exposed to the new coronavirus and high levels of pollution, since nitrogen dioxide reduces the body’s immunity and the particles are responsible for different respi-ratory and cardiovascular problems that also make our organism more susceptible to diseases like Covid-19”, he said.
Francisco Ferreira also stressed that, in addition to the reduction in road traffic, there is a decrease in other sources such as aeroplanes and cruise ships, which also contribute to an improvement in air quality.
“We have to learn from these difficult times in order to understand in a specific case the relationship between traffic levels and air quality so that, in the future, we will implement measures that ensure that we meet the limit values for pollutants such as nitrogen dioxide , which does not happen today”, he said.
With regard to aviation, Francisco Ferreira said that, although there are no measurements, “it is very likely that there has been a significant decrease”.