A new study published in the September edition Atmospheric Environment has reported that diesel cars sold by ten major automobile manufacturers in Europe between 2000 and 2015 generate up to 16 times more emissions on the road than in regulatory tests ― a level that exceeds European limits (1). In contrast to the Volkswagen scandal, the excess emissions do not violate any EU laws. However, the researchers point to the problem of “permissive testing procedures at the EU level and defective emissions control strategies.”
The study, led by Steven Barrett, Professor of Aeronautics and Astronautics at Massachusetts Institute of Technology (MIT), showed that diesel cars in the EU emit much more nitrogen oxide (NOx) ― the product of a reaction between nitrogen and oxygen gases during combustion ― on the road than the regulatory limits. When the NOx reacts with ammonia in the atmosphere, fine particles are formed that when inhaled can become lodged in the lungs leading to respiratory diseases, asthma, and other serious health conditions. Moreover, NOx emissions are known to contribute to ozone formation, which is also associated with a number of health problems. According to the study, in 2015 alone, excess NOx emissions from diesel cars caused 2700 premature mortalities, with cars produced by Volkswagen, Renault, and General Motors associated with the most yearly premature deaths ― in the hundreds.
The researchers assessed the total amount of excess emissions for each diesel car model of the major manufacturers: Volkswagen, Renault, Peugeot-Citroën, Fiat, Ford, General Motors, BMW, Daimler, Toyota, and Hyundai. Between them, they represent more than 90 per cent of diesel cars sold between 2000 and 2015. Excess emissions associated with each manufacturer were then calculated based on the number of cars and country of sale for each particular model. The excess emissions calculations were based on available emissions data from both laboratory testing and on-road tests. In addition, the team used a well-known chemistry transport model to simulate the distribution of NOx particles in the atmosphere in order to track where excess NOx emissions end up and to determine the EU populations most at risk.
The authors conclude that “if all manufacturers reduced emissions of the vehicles currently on the road to those of the best-performing manufacturer in the corresponding Euro standard, approximately 1900 premature deaths per year could be avoided.” The researchers also found that 70 per cent of the total health impact is transboundary. In other words, countries that produce very little NOx emissions experience a disproportionate number of premature deaths, likely owing to excess emissions drifting over from other countries. This suggests that to rectify the problem, coordination on a continental scale is required.
In 2015, diesel cars accounted for 41.3% of the total passenger car fleet in Europe. Diesel cars were originally promoted across the continent as they produce less carbon dioxide emissions compared to petrol engines. An increased awareness of the detrimental of NOx emissions on human health has led to changes in the EU standards on diesel exhausts in an effort to reduce these emissions. But it seems clear that regulators will need to do a lot more to prevent mortalities associated with NOx emissions.
(1) Chossière, G.P. et al. Country- and manufacturer-level attribution of air quality impacts due to excess NOx emissions from diesel passenger vehicles in Europe. Atmospheric Environment (2018). DOI: 10.1016/j.atmosenv.2018.06.047