Particulates are liquid or solid particles fine enough to be suspended in the air. They may be naturally formed – for example, in Canterbury, two sources are sea spray and dust blown off the Canterbury plains. They can also be artificially produced, especially as a result of burning. Most particulates are produced by motor vehicles, particularly diesel engines, or wood burners. Industry can also release particulates into the air.

The smaller particulates cause the most health problems. You breathe in particulates with the air that you breathe. The larger particulates get caught in your mucus membranes before they reach your lungs, but the smaller particulates can make it all the way to your lungs and the smaller they are, the further they go. The particulates that make it to the lungs are 10 microns or less or about 1/7 of the width of one of your hairs. These are known as PM10 particulates.

Associate Professor Simon Kingham is a researcher in the Geography Department at the University of Canterbury. He is researching the links between transport, woodburners, pollution, and health. Scientists like Simon Kingham are interested in measuring them and comparing levels of PM10 to levels of ill health in different areas. Also of interest are even finer particles that are 2.5 microns or less, known as PM2.5, which can make it even further into your lungs.

The particulates can cause respiratory illnesses because they block the small tubes that carry air into lung tissue. People who are more at risk from particulates are children, the elderly and people who already have breathing problems such as asthma or bronchitis. Your body responds to particulates in your lungs by producing mucus, which you have to cough out. They also place your body under stress, which may lead to cardiovascular illness.

Where the particulates come from is really important. The particulates that are formed naturally are not so much a problem because your immune system can deal with most of them. When there are additional particulates, such as those formed as a result of burning, your system may be overloaded and not cope, so you do not breathe as well. When materials are burned, they can form toxic molecules that may cause cancer, so particulates can make you really sick.

You might like to find out how scientists measure the particulates in the air. How do we know that it is the particulates that cause respiratory illnesses?

Activity idea

Try out this activity in which students investigate exhaust emissions, car use and air quality.

Published 8 January 2009, Updated 10 February 2015