Particulate matter

Pollution by particulate matter (PM10 and PM2.5) is the environmental factor with the greatest negative impact on human health. The effects range from respiratory ailments to lung cancer. The main pollutants are industry, small-scale furnaces, traffic and agriculture.

Combine harvester in the field
Harvest time, photo: BMLRT / Alexander Haiden

What is dust?

Dust is a natural component of the air and exists thus almost everywhere!

By large dust, we mean in general dust, which is visible for the human eye and is deposited in the direct environment of the place of origin. Large quantities of large dust are generated for example in the course of demolition work and/or in buildings. In the environment, large dust can often be easily identified as fine precipitation on terraces and cars. The mucous membranes of the nose of humans and animals retain most of the larger particles effectively.

Particulate matter is generated first and foremost in the course of all unfiltered industrial and combustion processes (industry, trade, power stations, households and road traffic). Especially tyre and brake disk abrasion and the carbon black released by motor vehicles, which is rising with increasing traffic density, contribute considerably to particulate matter pollution in urban areas. Re-suspension of dust from soils and utilised agricultural areas (in the case of longer periods of drought) as well as pollen and spores are considered to be further sources of dust input.

Apart from the size-related definition of dust, sometimes terms such as “dust precipitation” or “suspended particulate matter” can be found in language use.

Dust precipitation consists first and foremost of large dust, which is transported by the wind mostly only a few hundred metres away from the original source and then falls down to the ground.

By suspended particulate matter we mean dust fractions of smaller parts which are stirred up again and again due to their small size and remain for days and weeks in the atmosphere and are often transported over a distance of 1000 km, before they are, for example, finally washed out for example by precipitation.

Particulate matter

The definition of particulate matter dates originally back to the National Air Quality Standard for Particulate Matter (briefly called PM standard), which was introduced in 1987 of the US environmental authority EPA (Environmental Protection Agency). It constitutes a re-evaluation of different kinds of air pollutants: Whereas previously only the overall amount of air pollutants was taken into consideration, the focus is now on the directly breathable share of air pollutants.  In this way the fact that particulate matter is only restrained by the mucous membranes in the nasopharyngeal space and/or the tiny hair in the nose area to a certain degree, whereas coarse particles do not constitute a burden for the respiratory tract, is taken into consideration. 

In the first version of the American guideline the Standard PM10 was defined, for which a fixed threshold value has to be complied with also within the EU since the beginning of 2005. As opposed to the definition usually mentioned PM10 does not constitute a sharp differentiation of an aerodynamic diameter of 10 micrometres (10 µm); it has rather been attempted to imitate the deposition behaviour in the upper respiratory tract, which means particles with an aerodynamic diameter of less than 1 µm are completely integrated, with larger particles a certain percentage is included in the calculations, which decreases with rising size and finally reaches about 15 µm 0%.

Technically speaking this application corresponds to a weighting function (in the technical language it is called parting curve and/or separation function) on air pollutants (in practice this is achieved by means of a size-selective inlet on the measuring instruments). The designation PM10 is, in the final analysis, also derived from this weighting function mentioned before, as at about 10 µm exactly half of the particles are included in the weighting.

In 1997, the American guideline was supplemented by PM2.5, which describes the respirable particulate matter. The definition is analogous to PM10, however, the weighting function is much steeper (100% weighting < 0,5 µm;  0% weighting > 3,5 µm; 50% weighting at about 2,5 µm).

Health effects

A current evaluation of the health effects of particulate matter by the World Health Organisation (WHO) has shown clearly that there is a correlation between an increased PM2.5 pollution and severe health effects. These effects range from respiratory ailments such as coughing, the permanent increase in asthma attacks, to lung cancer.  Besides, it is also assumed that there are effects on cardiovascular diseases (heart attack) which could lead to a significant reduction of life expectancy.

Effective measures against the particulate matter problem

In the field of traffic this would be, among other things, tempo limits in polluted areas, temporary driving bans for diesel vehicles without particle filter in the case of permanently high pollution as well as the development of public short-distance transport (in conurbations).

In the field of trade and industry these are emission-reducing measures in large industrial plants (restorations, filters, etc.), a reduction of construction site lorry traffic (e.g. transport via railway) as well as particulate matter-reducing tender criteria with large construction projects (e.g. moistening of access roads).

For households, among other things, replacing obsolete boilers by modern low-emission biomass heating, the further development of district heating as well as increased thermal insulation measures in the course of the renovation of old buildings could be further options.

Of course the personal contribution of each and every individual has to be emphasized as well, this includes, of course, to avoid unnecessary car trips, especially on days with high particulate matter pollution, and to use public means of transport, or to overcome short distances by walking or cycling.    

Moreover, heating systems with solid fuels should be used in an economical way, and/or one should refrain completely from using second heating with solid fuels. In this context, we would like to refer to the initiative "Heating correctly with wood” (“Richtig heizen mit Holz”) dealing with the correct application of wood heating in order to reduce air pollutant emissions. 

By the way smoking cigarettes is a source of particulate matter, which is just as damaging to your health. Thus with smoker households values from 200 to 600 micrograms of particulate matter per cubic metres in the air were measured, which is four to twelve times the EU threshold value.