Making sense of responsible motoring
What is air pollution?
13th September 2018
Oxides of Nitrogen (NOx)
Oxides of Nitrogen are produced from the reaction of Nitrogen (N) and Oxygen (O) in the air, during combustion. There are actually two types of Oxides of Nitrogen (NOx), which are Nitric Oxide (NO) and Nitrogen Dioxide (NO2). These are not to be confused with Nitrous Oxide (N2O), commonly used in vehicle performance upgrades.

The majority of NOx is produced by road transport - a whopping 40%. The average car produces around 675g of NOx per year. The other NOx production is from the industrial sector (32%), Electrical power generation (21%) and other transportation (7%).

The industrial sector and power generation are together resposible for around 53% of NOx production
The inhalation of NOx can result in respiratory conditions, causing inflammation of the airways. Long term exposure can decrease lung function, increase the risk of respiratory conditions and increase the response to allergens. NOx also contributes to the formulation of Particulate matter (PM), and NOx gases react to form smog and acid rain.

High levels of NOx can have a detrimental effect on plant life, resulting in damage to leaves, as well as growth reduction. Vegetation which has been exposed to NOx may become more susceptible to diseases and frost damage.
The critical level of NOx to prevent detrimental effects on plant-life is 30 micro grammes per square metre. When an average car is driving on its own it is actually producing a tiny percentage of this in the immediate vicinity. However it is when lots of cars are within a built up area for long periods (such as a busy town), that the levels can go above that which is safe.
A rough limit for human contact would be 5 micro grammes per square metre, and again a single car produces too little to cause this. However, it would obviously not be good to directly breath in a cars exhaust fumes, and again cars collectively breach this level in very large numbers. Unfortunately not enough data is available to provide a true safe level. Indeed it is likely every person is very different.

In reality, the only sensible solution is to attempt to remove the production of NOx levels as much as possible, with the goal to remove them entirely from built up areas. This is actually where electric cars make the most sense.
There is no evidence to suggest the NOx output of cars is producing a global problem. However it is certainly important to try to reduce the NOx produced by cars, wherever possible.

While a small number of cars driving around a village are not causing any harm. It is in large cities like London, where hundreds of cars, buses and haulage vehicles are continuously emitting NOx, where there can be a problem. The more NOx is in the air, the more people may become ill from it; potentially leading to deaths. For this reason, government initiatives like the 'Green zone' around London, are actually a very good thing, and it actually makes complete sense to allow Electric vehicles into a large city, while restricting the entry of fossil fuel vehicles.
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Particulate Matter (PM)
Particulate matter is the term for solid particles and liquid droplets found in the air. Some particles such as dust, dirt, soot or smoke are large enough to be seen with the naked eye. Others are so small they can only be detected using specialist equipment.

Particulate matter can come from all manner of sources, such as construction sites, dirt tracks, fields or fires. Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industrial plants and transportation.

Unfortunately no one really knows how much Particulate matter is produced by cars, and what percentage the road vehicle is responsible for. However it is thought that the majority of Particulate matter comes from the power generation industry, with the remaining majority coming from the industrial sector and travel.

Petrol cars produce virtually no particulate matter, where as Diesel cars produce large quantities.
Because particulate matter is so small it can be inhaled by living organisms, and cause serious health problems. Particles less than 10 micrometres in diameter pose the greatest problems, because they can get deep into the lungs, and can also enter the bloodstream. This can lead to long term lung and heart problems.

In addition to this, particulate matter can pollute the air and reduced visibility. Some of the worlds national parks and cities are so full of particulate matter it causes a very noticeable reduction in how far you can see.

Unfortunately, although we know motor vehicles are responsible for large amounts of Particulate matter production, no one seems to have done enough research to indicate how much comes from where.
Large particles, such as sand, dirt and dust are not thought to be a major problem. Indeed unless incredibly large quantities are inhaled, they are not hazardous to health. Small particles, such as those produced by the industrial sector and transportation, are incredibly hazardous to health.

No one really knows how much is safe, however research suggest keeping levels below 10 microgrammes per square meter would provide a low risk to human life (though not completely risk free).

No one can put a realistic limit on how much is acceptable, so all we can do is continue to monitor the levels in all major cities, including the effects. But if we all do our part to help reduce PM it is hoped that the world wide levels will slowly decrease, and with it, the number of reported health issues may start to fall.
Of course a reduction in particulate matter from cars can only be a good thing. Once more it is also sensible to reduce the number of fossil fuel cars in built up areas, favouring electric vehicles instead. However no one can really say how much of an impact cars have as a whole, and it is also important for the industrial sector and power generation industry to play their part.

Converting the power generation industry to cleaner sources, such as Wind turbines, Hydro-electric, Solar and Nuclear, would dramatically reduce the planets Particulate matter production. It is therefore confusing why more is not being done to encourage this. As a happy side effect, if the power generation industry cleaned its act up, electric cars would actually become even better for us all as a direct result.
Hydro Carbons (HC)
A hydrocarbon is an organic compound consisting entirely of Hydrogen and Carbon. Hydrocarbons are naturally occurring, forming in crude oil where decomposed organic matter provides large quantities of carbon and hydrogen. When bonded this forms large quantities of hydrocarbons.

Diesel cars produce practically no hydro-carbons, where as the Petrol car (without a catalytic converter) produces large quantities. However modern cars with catalytic converters also produce close to no hydrocarbons.

Hydrocarbons are not actually produced by the combustion process of a car, but instead are fragments of fuel molecules, only partially burned and released into the atmosphere.

As far as cars go, hydrocarbons are not really a major concern. Although inhaling large quantities can result in poisoning, a modern car produces close to not hydrocarbons. In addition, even a decades old car would not produce enough hydrocarbons to create a problem, unless someone deliberately inhaled large quantities of the exhaust fumes.
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