This image shows the presence of smog hanging over a major city in Asia, but it is important to note that while vehicle exhaust is a significant ingredient in urban smog, this kind of pollution is now mainly caused by industrial pollutants that are sometimes emitted by industries located long distances from urban centres.
On a practical level, though, the removal of NOx (oxides of nitrogen), which is the prime driver in the formation of smog, from the exhaust gas of motor vehicles by EGR (Exhaust Gas Recirculation) systems has produced greatly reduced levels of urban pollution, including smog, in and over large urban centres in developed countries across the globe.
From environmental and public health perspectives, the removal of NOx from vehicle exhaust has had and continues to have major advantages and benefits. We need not delve into the more technical details of the effects of NOx, and by extension, smog, on human health here, but suffice it to say that NOx is directly implicated in health issues like serious and life-threatening respiratory conditions, heart attacks and several ischemic heart diseases, and various forms of pollution-induced cancer. Other deleterious effects include stunting in young children, birth defects in infants, and according to some reports, increased levels of both infant mortality and premature death in young children and older persons with compromised immune systems.
Based on the above, there is no doubt that EGR valves/systems are needed to maintain reduced vehicle exhaust-based pollution levels on the one hand and to maintain the downward trend in the prevalence of vehicle exhaust gas-induced human health conditions, on the other.
Compared to these advantages of reducing NOx levels in vehicle exhaust gas, the fact that a fully functional EGR system on a modern vehicle can improve that vehicle’s overall performance and fuel efficiency seems trivial in the bigger scheme of things, so to speak.