Diesel or Petrol? Much More Than Just a Simple Question of Emissions

[This article has been jointly written by David Rojas-Rueda and Mark Nieuwenhuijsen, researchers at the Centre for Research in Environmental Epidemiology (CREAL), a centre allied with the Barcelona Institute for Global Health (ISGlobal). Both of them will be among the panellists in the IV Internacional City Health Conference at CosmoCaixa Barcelona on November 5 and 6.]

Airborne pollution accounts for only a small fraction of the problems caused by cars in our citiesDiesel vehicles account for a large proportion of the European market because they are promoted as being more fuel efficient and having lower CO₂ emissions than cars running on petrol. However, diesel vehicles emit more pollutants that are harmful to our health than petrol vehicles. The issue of diesel emissions has recently been highlighted by the Volkswagen scandal; however, airborne pollution accounts for only a small fraction of the problems caused by cars in our cities.

As well as polluting the air, cars produce noise and occupy a great deal of public space for both transit and parking that could be allocated to uses, such as green spaces, that would be more beneficial to our health. Ultimately, after factoring in the high percentage of people in our population who lead sedentary lives, a phenomenon closely related to high levels of car use and insufficient parks and other spaces suitable for exercise, the negative impact on our health of cars extends far beyond the emission of pollutants.  

The negative impact on our health of cars extends far beyond the emission of pollutantsWe could improve the quality of air in our cities—a public health priority—by changing technologies, that is, through a shift towards cleaner hybrid or electrical vehicles. But this would only solve part of the problem. City traffic would continue, accidents would still occur, the public space would still be occupied, and sedentary lifestyles would continue to be the norm. So why not look for a more healthy change? Instead of investing in electric cars, why not invest in public transport, in prioritising pedestrians, and in bicycles or other more ecological means of transport?

In Spain, 40% of the adult population has a sedentary lifestyle. This low level of activity could be significantly improved if we walked and cycled more since 57% of city trips are currently made by car. In Barcelona alone, at least 170 deaths could be avoided every year if 40% of trips currently undertaken by car were made using public transport or bicycles. And the deaths prevented would not only be the result of the reduction in airborne pollution; the increase in physical activity among the population would be a more important factor.

A city moving at a more human pace could become a more friendly and healthy placeA reduction in the number of cars (whether diesel, petrol or electric vehicles) would mean more space for ourselves, more connection between citizens, more green spaces, fewer traffic accidents, less noise and better air quality. A city moving at a more human pace (with people walking, cycling and using public transport) could become a more friendly and healthy place for children and adults and result in a better quality of life.

It is time town planners and the authorities responsible for transport, health and the environment began working together and making a greater effort to create healthier models for our cities and mobility systems.