Science Daily takes a deeper look at the problems with car and truck exhaust fumes:
Environmental protection and health agencies base their air pollution management on atmospheric models that rely on these experimental data from test facilities. While there have been some doubts about nitrogen oxide emissions for some time, scientists lacked the technology to measure the actual amount of emitted pollutants in a specific area and to determine their overall source strength. A team of physicists headed by Thomas Karl from the Institute of Atmospheric and Cryospheric Sciences at the University of Innsbruck has now implemented a process to do exactly that in the center of Innsbruck, Austria.
…
“We continuously measure the concentration of carbon dioxide, nitrogen oxide and volatile organic compounds at our urban observatory in Innsbruck. We record 36,000 data points per hour,” explains Karl. Using statistical methods, the scientists infer emissions from these data within a radius of about one kilometer of the measurement location. The analysis of the data of a three months long measurement campaign, which took place in 2015 and is now published in Scientific Reports, shows two main sources for nitrogen oxide concentrations in the Innsbruck air: traffic and residential combustion, with traffic accounting for more than 80 % of the nitrogen oxide emissions in the surroundings of the test station at the University. The majority of the emissions is caused by Diesel cars. “This result is relatively representative for the whole city,” says Karl who points out the far-reaching relevance of the results: “Even newer atmospheric models are based on emission inventories that underestimate nitrogen oxide emission levels up to a factor of four.” The actual nitrogen oxide emission levels may be four times higher than predicted in the some models.
…
Regulatory thresholds are meant to limit emissions. However, in Innsbruck, for example, the average level of nitrogen oxide is 36 times higher than the new emission regulation standard laid out in the Clean Air Act in the USA.