You are probably aware that cars and trucks are a big source of air pollution in the United States, but did you know how big? After all, there are lots of other things that emit pollutants in the US, like power plants, for example. So how big is it? According to the EPA, cars and trucks generate about half of the air pollution in our country. This pollution not only comes out of a vehicle’s tailpipe as the result of the internal combustion process but it also comes from the wearing down of tires and other automotive related processes.
Have you ever wondered what this air pollution specifically consists of? Thompson Mazda of Baltimore, MD, a full-service Mazda dealer, said to us that it isn’t quite as complicated as it sounds and you can boil it down to five primary components. Let’s take a look at each one.
Carbon Monoxide (CO)
Not to be confused with CO2 (Carbon Dioxide), CO is a colorless, odorless gas that causes serious, often fatal, health problems. Motor vehicles emit massive amounts of carbon monoxide. However, it isn’t a very stable molecule (half-life is 4 to 6 hours) and breaks down quickly.
Gasoline is made up of a soup of different hydrocarbon components and some of these are emitted into the atmosphere because of incomplete combustion. HCs often combine with NOx in the presence of ultraviolet sunlight to form ozone (O3) which has adverse health effects and, well, you know about the upper atmosphere.
Nitrogen oxides (NOx)
These compounds are generated by the combination of the nitrogen and oxygen in an engine’s incoming air. The two main components are oxide (NO) and nitrogen dioxide (NO2). As we mentioned in the text above, the compound combines with hydrocarbons and other volatile organic compounds (VOCs) in the presence of ultraviolet sunlight to produce photochemical smog, mainly ozone (O3).
Alkyl lead compounds are used as fuel additives in large vehicles and aircraft to control engine pre-ignition. Thankfully, they aren’t sold in the US for passenger car use anymore. Lead is released into the atmosphere from the combustion of leaded gasoline. Enough lead in the atmosphere can cause nasty things like lead poisoning and other health concerns.
Particulate Matter (PM)
Ever wonder where are the rubber goes from the millions of tires we wear down every year? It becomes a very fine particulate matter that falls down to the ground. At least it doesn’t pollute the atmosphere.
Reducing automotive air pollution
The first two techniques that automotive engineers used to reduce internal engine pollutants are exhaust gas recirculation (EGR) and mechanical airpumps. EGR is a technique where a small amount of exhaust gas is feed back into the engine during operation. The result was a cooler combustion process which lead to lower NOx levels. EGR was introduced 30 years ago and is still used today. Air pumping is a technique where outside air is pumped under pressure into a car’s intake manifold so that more oxygen is available for combustion. It is not used as much today.
The next technology that Detroit developed to reduce pollution is Catalytic Conversion. Catalytic converters are mounted in the exhaust pipe and they transform harmful pollutants into benign compounds. Catalytic Convertors require unleaded gasoline which also will decrease the atmospheric lead concentration.
Today sophisticated automotive control systems further reduce pollutants by monitoring O2 levels and adjusting the fuel injectors and engine timing.