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Diesel NOx Emissions Underestimated by 50%, Kill 38,000 Every Year & Now Affecting Sales

05.18.17 | Blog | By:

A study published in Nature and lead by the ICCT has found that laboratory tests of NOx emissions from diesel vehicles significantly underestimate the real-world emissions by as much as 50%. The research also was done in collaboration with scientists at the University of York’s Stockholm Environment Institute (SEI); University of Colorado; and the International Institute for Applied Systems Analysis.

The researchers assessed 30 studies of vehicle emissions under real-world driving conditions in 11 major vehicle markets representing 80% of new diesel vehicle sales in 2015. Those markets include Australia; Brazil; Canada; China; the European Union; India; Japan; Mexico; Russia; South Korea; and the United States.  Of these markets, they found vehicles emitted 13.2 million tons of NOx under real-world driving conditions—4.6 million tons more than the 8.6 million tons expected from vehicles’ performance under official laboratory tests.

The study also estimates that excess diesel NOx emissions in 2015 were also linked to approximately 38,000 premature deaths worldwide—mostly in the EU, China, and India. China suffers the greatest health impact with 31,400 deaths annually attributed to diesel NOx pollution, with 10,700 of those deaths linked to excess NOx emissions beyond certification limits. In Europe, where diesel-passenger cars are common, 28,500 deaths annually are attributed to diesel NOx pollution, with 11,500 of those deaths linked to excess emissions.

At a global level, the study estimates that the impact of all real-world diesel nitrogen oxide emissions will grow to 183,600 early deaths in 2040, unless something is done to reduce it. In some countries, implementing the most stringent standards already in place elsewhere could substantially improve the situation, according to the researchers.

Meantime, ICCT says that European cities are setting the tone in the diesel debate. Specifically, policy announcements from major cities have raised doubts about being unable to drive a diesel in important urban areas. This is creating doubt about the resale value of diesel cars and curbing consumers’ appetite for diesel technology, according to ICCT. The chart below shows sales versus the number of announcements from European cities limiting or banning diesel vehicles.

Source: ICCT

ICCT notes:

Diesel car registrations are down in Europe: March 2017 saw a 5-year low in France, Germany, Spain, and the UK, which together make up almost 60% of the European new car market. Dieselgate sparked this development and revealed national regulators’ failure to police the car market, but cities are now leading the charge against diesel cars.


Some cities are going further than just banning diesel cars. Barcelona, for instance, is exploring the superblock concept to clean up its air and to reclaim space from road transportation. With a plethora of options (and buzzwords) for cleaner, safer road transportation to choose from–electric vehicles, car/ride sharing, autonomous vehicles–it will be interesting to see how cities design future transportation systems. Whatever route they take, it seems increasingly likely that they will continue to drive diesel cars out of the European car market.


Tammy Klein is a consultant and strategic advisor providing market and policy intelligence and analysis on transportation fuels to the auto and oil industries, governments, and NGOs. She writes and advises on petroleum fuels, biofuels, alternative fuels, automotive fuels, and fuels policy.

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