The other pollutants from petrol, diesel and alternative fuel engines are mainly Carbon Monoxide, Oxides of Nitrogen, un-burnt Hydrocarbons and fine particles. The first three are gases and are invisible.
Fine particles are usually invisible although in certain operating conditions diesels will produce visible particles, appearing as smoke. Petrol engines will also produce visible particles if they are burning engine oil or running rich, for example, following a cold start.
Unlike CO2, emissions of these pollutants are not directly linked to fuel consumption. Pollutant levels are more dependent on vehicle technology and the state of maintenance of the vehicle. Other factors, such as driving style, driving conditions and ambient temperature also affect emission of pollutants.
However, as a starting point new passenger cars must meet minimum EU emissions standards.
The effects of these exhaust gas pollutants and their effects are described in more detail below:
Carbon Monoxide reduces the blood’s Oxygen carrying capacity which can reduce availability of Oxygen to key organs. Extreme levels of exposure, such as might occur due to blocked flues in domestic boilers, can be fatal. At lower concentrations CO may pose a health risk, particularly to those suffering from heart disease.
Oxides of Nitrogen react in the atmosphere to form Nitrogen Dioxide (NO2) which can have adverse effects on health, particularly among people with respiratory illness. High levels of exposure have been linked with increased hospital admissions due to respiratory problems, while long term exposure may affect lung function and increase the response to allergens in sensitive people. NOx also contributes to smog formation, acid rain, can damage vegetation, contributes to ground level Ozone formation and can react in the atmosphere to form fine particles (‘secondary particles’).
Fine particles can have an adverse effect on human health, particularly among those with existing respiratory disorders. Particles have been associated with increased hospital admissions due to respiratory and cardiovascular problems, bringing forward the deaths of those suffering from respiratory illnesses and a reduction in life expectancy.
Hydrocarbons, contribute to ground level Ozone formation leading to risk of damage to the human respiratory system. In addition, some kinds of HCs are carcinogenic and they are also indirect greenhouse gases.
The Government is convinced that action to reduce harmful emissions must continue. Its approach to tackling air pollution is set out in the Air Quality Strategy for England, Scotland, Wales and Northern Ireland. This sets health based standards for eight main air pollutants, from which air quality objectives are derived, together with a timescale for their achievement.
The Strategy identifies the action required at a national and international level, and the contribution industry, transport and local government can make to ensure objectives are met.
Achieving the air quality standards for Nitrogen Dioxide and fine particles presents the greatest challenge, especially in urban areas and close to busy roads. Emissions of the above pollutants are being reduced by improving the quality of fuels and by setting increasingly stringent emission limits for new vehicles.