Traffic emissions are air pollutants emitted by transport, causing an unhealthy environment and have a negative influence on air quality. Examples of traffic emissions are: nitrogen oxides (NOx), total hydrocarbon (THC), non-methane hydrocarbons (NMHC), carbon monoxide (CO) carbon dioxide (CO2) and particulate matter (PM).
Particulate matter emissions
Particulate matter emissions have an influence on health of people. They can cause severe respiratory problems. Therefore, there are regulations for the maximum allowed emissions and concentrations of particulate matter. Most severe effects are for the smallest particles. Two types of fine dust are distinguished, namely PM10 and PM2.5. PM10 are particles with a diameter up to 10 micrometer, while PM2.5 are particles with a diameter smaller than 2.5 micrometer. Since the health effect is related to the concentration of fine dust, this is furthermore connected to a specific location at the road network. Other influences are e.g. the weather.
Greenhouse gas emissions
Greenhouse gas emissions play a role in the global warming effect of the earth. The most important greenhouse gas emitted by vehicles is CO2. There is no health effect for CO2, nor is it related to the location where it is emitted.
Emissions of other pollutants
Other pollutants from traffic are for example nitrogen oxide (NOx) and sulfur oxide (SOx). A more complete list can be found on this site.