What is it?
Air pollution comes in a number of forms and from a range of sources. Common types of air pollution include:
- Particulate matter (usually known as PM10 and PM2.5)
- Nitrogen oxides
- Carbon monoxide
- Volatile organic compounds
and there are many more. All these pollutants cause harm to humans and animals, but the scale of the problem is not well understood by the public and each month new research uncovers further links to health problems.
What is particulate matter?
The first category above is the target of the Air Apparent sensors. Particulate matter was chosen because it is very prevalent in the air we breathe in the UK, it has well-established links to health problems and premature death, and because government monitoring is currently woefully inadequate. A city the size of Bristol has one government-run monitoring site for particulate matter, yet recent research from the University of Texas and Google shows that particulate concentrations in the air vary dramatically on a street-by-street basis.
Particulate matter is the name given to very small particles of solid or liquid which are suspended in the air. They are usually classified as PM2.5 or PM10, where numbers refer to the maximum width of the particles in thousandths of a millimetre (microns).
A PM2.5 particle is so small that more than 600 could fit on the cross-section of a human hair. It is their small size, when coupled with high concentration which makes PM2.5 pollution so damaging: the particles are fine enough to pass deep into your lungs and directly into your bloodstream where they can cause not just respiratory problems and lung cancer, but serious cardiovascular problems which can often be fatal.
PM10, while thought to be less harmful, are still small enough to pass beyond the larynx, so cause a wide range of respiratory problems including exacerbating the symptoms of asthma.
In both cases, due to the microscopic size of the particles they are not visible in the air unless concentrations are incredibly high or they are accompanied by other pollutants.
Where does it come from?
The source of the particulate matter in the air you breathe will vary depending on a number of factors, including:
- Your location (urban, residential, industrial, rural etc. as well as which country you live in)
- Weather conditions (wind strength, wind direction etc. although rain has little effect)
- Your lifestyle (how much time you spend indoors, your exposure to smoking and wood burning, how you travel)
- Seasons (dust storms from desert regions, seasonal festivals involving fireworks)
For people living in the UK, the most common sources of dangerous particulates across the year are vehicles, especially those using diesel, wood burning and heavy industry, usually in that order. This will be highly dependent on your surroundings, so understanding why areas experience high levels of pollution is important for making lifestyle choices, such as when and where to exercise.