Particles as air pollution

Particles is the term used for a mixture of solid particles and liquid droplets suspended in the air.

Particles are also known as 'particulate matter' or PM. The particles are made up of a number of components, including nitrates and sulfates, organic chemicals, metals and soil or dust particles. Some particles, such as dust, dirt, soot or smoke, are large or dark enough to be seen by the naked eye. Others are so small that they are invisible.

Particles come from natural and human-made sources (e.g. dust, pollen, bushfires, motor vehicle emissions). Total suspended particulates (TSP) are solid particles and liquid droplets 100 micrometres or less in diameter. Particle pollution also includes particles with diameters that are 10µm or smaller (including particles smaller than 2.5µm) and these are designated as PM10.

Particles from vehicles on dirt roads and dusty industries, such as mining, crushing and grinding, are generally larger than 2.5µm in diameter and are included in PM10.  Even smaller or 'fine particles' are those with diameters that are 2.5µm or smaller (designated as PM2.5) and are commonly found in smoke and haze.  For comparison, the average human hair is about 70µm in diameter, making it some 30 times larger than the PM2.5 particles measured in air quality monitoring networks.

Both PM10 and PM2.5 are components of TSP, and associated with adverse health effects ranging from respiratory problems to premature death of people with heart and lung disease.

Some particles are natural while others are generated by human activity. Natural sources include bushfires, dust storms, pollens and sea spray.

Particles generated by human activity can be emitted from sources such as motor vehicles, power plants, mining and materials handling, residential wood burning, agricultural burning, and some industrial processes; these are known as primary particles. Others are formed in complicated reactions in the atmosphere from chemicals such as sulfur dioxide and oxides of nitrogen emitted from power plants, industries and motor vehicles and are known as secondary particles.

Large particles in the air usually cause reduced visibility for a short time and settle close to their source. 

Small or fine particles can remain in the atmosphere for several days or longer and be transported great distances from their source by the wind. They are capable of scattering light which also leads to a reduction in visibility.

Particles are generally removed from the atmosphere by rain or when they come into contact with surfaces.

Visibility reduction

Fine particles (PM2.5) are the major cause of reduced visibility in parts of NSW and hence have an impact on our enjoyment of the environment.  Fine particles can also cause a nuisance when they settle and soil homes, buildings and other surfaces.

Health effects

While most healthy people can breathe in small amounts of particles without major long-term effects, extreme air pollution events such as bushfires and major dust storms can affect everyone.  Some people  (eg children, those with heart or lung disease and the elderly) can be sensitive to even relatively low levels of particle pollution.

Exposure to fine particle pollution has been linked to a variety of health problems including increased respiratory symptoms (e.g. irritation of the airways, coughing or difficulty breathing), heart problems and premature death in people with heart or lung disease.

Health effects depend on a number of factors, including:

  • particle size
  • intensity and duration of exposure
  • the chemical nature of the particles
  • a person’s health and
  • weather conditions, including wind, humidity and rainfall.