Nutrition Portugal , Aveiro, Wednesday, June 17 of 2015, 13:33

The evolution of the contaminating emissions of cars is analysed

A study of the University of Aveiro confirms that new cars pollute less, but warns that they still give off very harmful elements that are not appropriately measured

José Pichel Andrés/DICYT A study of the University of Aveiro has revealed that the contaminating emissions of new cars have been reduced in recent years thanks to legal restrictions and technological improvements. However, the authors of the study (which has been called Projeto URBE) warn that many other elements that are harmful both to health and to the environment cannot be detected by using current methods.


The European Union establishes maximum emission values for all cars, in particular for carbon monoxide, nitrogen oxides, hydrocarbons, and particles. Catalysers, particle filters, and gas recirculation systems have reduced emissions significantly, and in addition the manufacturers have managed to lower fuel consumption.


In short, in recent years the imposing of strict limits and technological improvements has had a very positive effect. This has been confirmed by the researchers of the University of Aveiro in this analysis of cars sold between 2000 and 2014, which are known by European light vehicle regulations as Euro 3, Euro 4, and Euro 5 in order of age.


For example, “the latest diesel cars equipped with filters show insignificant particle emissions”, DiCYT was told by Célia Alves, a researcher of the Centre of Environmental and Marine Studies (Centro de Estudos do Ambiente e do Mar, CESAM) of the University of Aveiro.


This does not mean that new cars are not contaminating, but rather that “the measurement methodologies need to be rethought”, as the current system consists of fitting a sampling filter that is weighed to quantify the mass of particles given off. This method “no longer makes sense” because the particles generated by engine combustion are so tiny that they are hard to detect. However, they have a high capacity for penetrating the air sacs of the lungs, which is very harmful to health.


Polycyclic aromatic hydrocarbons associated with the particles stand out as being potentially carcinogenic, especially in cars of a lower category than Euro 4 which make up a significant percentage of those on the roads. These include volatile compounds such as naphthalene, of which older cars give off high emissions. “These volatile compounds have less carcinogenic potential but their emissions are higher, so in fact the health risk is greater”, the expert points out.


On the other hand, this study confirmed that cars that are not serviced regularly do not comply with the emission limits of their category. This means that Euro 4 and Euro 5 vehicles may pollute more than other older ones if not suitably maintained; the researchers consider this to be worrying given the current economic situation.


The study also indicates the behaviour of the various types of vehicle. In older cars diesel models are more contaminating than petrol ones, while in more modern cars this distinction becomes blurred. Moreover, town driving generates between three and four times more emissions than the open road, and during acceleration and at high speeds is when these emissions increase most sharply.


Health and the environment are affected


Célia Alves reminds us that several studies have related continuous exposure to high levels of environmental particles with reduced life expectancy. For example, the general category of “particles” given off by a car includes soot in both solid and liquid form, which may cause cardiopulmonary problems and even cancer.

Neither should it be forgotten from an environmental point of view that fossil fuels used in vehicles give off methane, nitrous oxide, CO2, and other elements which “directly or indirectly contribute towards the greenhouse effect”.


The study was published in the journal Environmental Science and Pollution Research and helps to clarify the risks that vehicles still represent to health and the environment, as they are the main form of air pollution in urban areas. Moreover, from a scientific point of view this allows the construction of models referring to contaminating emissions in southern Europe. These models attempt to identify and quantify the emissions causing air pollution. However, most of this information takes the United States as a reference, where the cylinder capacity and the proportion of cars running on petrol is much higher than in Europe.


This research was financed by the Science and Technology Foundation of Portugal. From now on the objective of the researchers is to extend the study to heavy goods vehicles and motorbikes, together with other contaminating elements that have never been taken into account when assessing the pollution that traffic causes, for example type wear.


Bibliographical reference  


Elements and polycyclic aromatic hydrocarbons in exhaust particles emitted by light-duty vehicles. Alves CA, Barbosa C, Rocha S, Calvo A, Nunes T, Cerqueira M, Pio C, Karanasiou A, Querol X. Environmental Science and Pollution Research, 2015. DOI 10.1007/s11356-015-4394-x