The Combustion ProcessGasoline and diesel fuels are mixtures of hydrocarbons (made of hydrogen, oxygen and carbon atoms.) Hydrocarbons are burned by combining with oxygen. Nitrogen and sulphur atoms are also present and combine with oxygen when burned to produce gases. Attempts to reduce exhaust emissions from gasoline and diesel engines have been compromised by limitations of testing, inherent flaws in the design and inadequate maintenance of emission control devices.
Diesel engines a pose different emission control problems than gasoline engines. Diesels require more sophisticated and expensive components than the catalytic converters fitted to gasoline engines. Diesel emissions contain nitrogen oxide gases and carbon particles, the smallest of which contribute to lung and heart disease. Increases in airborne fine particulate matter increases the risk for myocardial infarctions, strokes and heart failure. Particle deposition in the lungs activates the sympathetic nervous system and triggers the release of systemic pro-inflammatory responses.
Brook and Rajagopalanb stated: "Higher circulating levels of inflammatory cytokines cause vascular endothelial dysfunction and activation of vasoconstrictive pathways while blunting vasodilator capacity. At the molecular level, the generation of oxidative stress with the consequent up-regulation of redox sensitive pathways appears to be a common mechanism of these pro-hypertensive responses. Due to the ubiquitous, continuous and often involuntary nature of exposure, airborne fine particles may be an important and under-appreciated worldwide environmental risk factor for increased arterial BP.
In Sept. 2015 a scandal erupted when Volkswagen, the world's largest car manufacturer, was caught cheating on emission tests of their diesel engines. In testing lab conditions, VW could show conformity with emission standards fro nitrogen oxides. Subsequent independent testing of VW diesel vehicles in road tests revealed high levels of nitrogen oxides emitted in real operating conditions. Errors in media reports proliferated with talk of defeat devices and software that would fool emission tests.
Relevant engineering data was not readily available but likely the cause of the problem was the Nitrogen Oxide converter (aka NOx storage catalytic converter ) that required injections of unburned fuel to keep the converter clean and functional. The exhaust output was supposed be free of nitrogen oxides. The computer that controlled fuel injection was programmed to inject more fuel than was needed for combustion for about 2 seconds per minute. The fuel reaching the converter would burn increasing the temperature in the converter. Burning the diesel fuel in the converter would likely increase the emission of other air pollutants. The software functioned optimally for emissions testing and was turned off when the engine was in service. The NO converter was a poor design that would increase fuel consumption and decrease engine performance if the converter was operated for full emissions control.
Jack Baruth advocated the end of diesel cars and pickup trucks. He stated: "Western democracies encouraged diesel even though they were perfectly aware of the health hazards posed by diesel particulate exhaust. Those risks are far better documented than even the most "settled" climate science, and they are very real. Eurocrats chose diesel in order to be seen to be doing something about global warming, and the manufacturers had to abide by their choice. The result? Paris has had to ban cars for hours or even days at a time because of smog. According to The Guardian, "diesel-related health problems cost (the British National Health Service) more than 10 times as much as comparable problems caused by petrol fumes. Last year the UN's World Health Organization declared that diesel exhaust caused cancer and was comparable in its effects to secondary cigarette smoking. And that was when people thought that these diesels were meeting pollution standards! Now, of course, we know that many of them were not, and that even the diesel cars that weren't designed to cheat the tests are not performing in the real world the way they do in the test labs. In other words, diesel-powered automobiles are killing people, and in not inconsiderable numbers. The jury is in and the evidence is clear." (Jack Baruth. Road & Track. Oct 2015)
A review in the Science journal, Nature, questioned the relationships between auto manufacturers and regulatory bodies: "Among the questions raised by the scandal that allowed the German car maker Volkswagen to sell 11 million vehicles containing software that cheats emissions tests, many will ask why the regulators failed to notice and halt the practice. The answer is not complicated. Regulated industries exert massive, discreet pressure on regulators such as the US Environmental Protection Agency (EPA), to stop them doing their jobs properly."
To put the VW scam in perspective, the big problems were corporate cheating and deliberate violation of public trust. It appears that this deception will cost VW several billion euros and is an embarrassment for all of Germany. Regulatory agencies have been alerted to their limitations and will be changing testing procedures for all new engines that include monitoring emissions during real driving tests in real driving conditions.
See Air and Breathing by Stephen Gislason MD