In recent years, the emission which has received most publicity is carbon dioxide. This is a greenhouse gas and many scientists believe it is partly responsible for global warming. So far, it has not been proven to be directly harmful to human health – we all breathe out carbon dioxide!
Of greater concern are toxic exhaust emissions, which have a direct, adverse effect on human health. These include carbon monoxide, hydrocarbons, oxides of nitrogen and particulate matter. The way their toxicity manifests itself varies, according to the durability of the substance in question and where it is emitted.
Some toxins are primarily of concern in confined spaces, while others can have a negative impact over several miles, especially in cities.
However, we will focus here on two types of toxin produced by combustion engines which have a serious impact closer to home: carbon monoxide and particulate matter.