Air Pollutants – Fine Particles
Particles are very small pieces of solid material that are carried in the air, the larger particles are sometimes called dust, soot or smoke depending on how they have been produced. The composition of particles varies widely, and this makes finding out how our health is affected particularly difficult. The size of the particles affect whether or not they can be inhaled deep into the lungs and cause damage to our health. Particles smaller than 10 microns (µm) written like this: PM10, are generally accepted as being the size that can penetrate into the lungs. These particles are very small indeed, compare the diagram below of a particle of 10 µm with a cross section of a human hair. Human hairs are usually around 70 µm across.
The instruments that measure fine particles are usually set to measure PM10 and PM2.5. PM2.5 is even smaller at 2.5 microns, and it is believed that it is this small size particle that has the worst effect on our health.
Fine particles are emitted by a wide variety of sources including road vehicles, domestic heating (coal and wood fuels), quarrying, and other industrial sources. Secondary particulate matter and a range of other particles, including those from natural sources, also contribute to outdoor concentrations.
Evidence has recently been collected showing that day to day variations in concentrations of airborne particles, measured as PM10, PM2.5, Black Smoke or other measures, are closely associated with variations in a range of health effects. These include deaths, admissions to hospital of people with breathing difficulties, circulatory problems and the worsening of asthma symptoms. As well as these effects, long-term exposure to particulate air pollution is associated with a decrease in life expectancy. The higher the average particle level that people are exposed to throughout their life, the more their life expectancy is shortened.
Particles in the air can affect visibility as they absorb and scatter light. They can also prevent the suns rays reaching the Earth’s surface. Particles are also responsible for the blackening of stonework on buildings and in serious cases can cause soiling of cars, windows and washing. People living next to quarries, building sites, cement works and busy roads can experience dust from these sources.