Fine Particles (PM10)
Particulate matter air pollution consists of a mixture of particles suspended in the air we breathe. PM10 are particles less than 10 microns in size (a micron is one 1000th millimetre. Compare this with the diameter of an average hair at around 75 -100 microns in diameter). PM10 particles are produced naturally by volcanoes, wind-blown fine sand and soil, sea salt and mould spores, or can result from human activity e.g. emissions from transport and power stations. PM10 particles are also formed in the atmosphere from other pollutants e.g. sulphates and nitrates. Because these particles are so small, some can stay airborne for several days and travel from as far a field as Eastern Europe, and the Sahara. However, in general the highest levels are found next to busy roads.
The particles of most interest are those small enough to be breathed into the deepest part of the lung and are known as PM10. Particles larger than this are filtered out in our upper respiratory tract. Particulates are amongst the most harmful of air pollutants to human health. This is especially the case for people with pre-existing lung and heart problems for whom exposure may trigger asthma attacks or cause hospitalisation in severe cases. Future research is likely to concentrate on understanding how particulates cause ill health and look at particle numbers and size in relation to health effects. There is still considerable debate as to whether it is the number of particles or mass that is significant to health, however, it is known that these particles are inhaled deep into the lungs, where, over time, they will reduce lung capacity and function.