Particulate matter is a major pollutant that is found in both outdoor and indoor air. They are a complex mixture of solid particles and liquid droplets. Their chemical composition varies according to the emitting sources, their transport in the air and weather conditions.

A distinction is made between:

• the “PM10”, which stands for “Particulate Matter”, whose diameter is less than 10 microns
• the “PM2,5”, which again stands for “Particulate Matter”, whose diameter is less than 2.5 microns.

Due to their very small diameter, particulate matter penetrates easily into the body and are very reactive. They can therefore cause or aggravate a number of diseases.

In addition to particulate matter, other pollutants can be found in the air:

• Ozone (O₃)
• Nitrogen dioxide (NO₂)
• Sulfur dioxide (SO₂)
• Benzo[a]pyrene
• etc.

DID YOU KNOW? 92% of the world’s population live in locations where air quality levels do not meet the limits imposed by the World Health Organization (WHO). These are mainly developing countries.

Particulate matter is emitted naturally via soil erosion through winds, fires, volcanic eruptions, etc.

But human activities greatly increase their concentration:

• combustion of fossil fuels (petrol, diesel, oil, wood, coal, etc.) for the production of electricity, transport, heating
• waste incineration
• industrial activities related to cement production, casting, fine chemicals
• activities associated with the construction or agriculture industries

DID YOU KNOW? According to the European Environment Agency (link is external), in Belgium 1,050 premature deaths were attributed to particulate matter in 2013.

When we breathe, particulate matter penetrates easily into the body. It then travels more or less deeply through the airways according to their size. The smallest particles can reach the lungs and some of their components pass into the bloodstream.

Particulate matter represents a known or highly probable risk factor for the expression of several diseases:

• acute or chronic respiratory diseases (bronchitis, asthma, lung cancer)
• cardiovascular diseases (stroke, myocardial infarction)
• neurological effects (decline of cognitive function, development of Alzheimer’s, Parkinson’s, etc.)
• impacts on pregnancy, the foetus (premature birth, low birth weight, etc.)
• effects on the immune system
• diabetes

Since 2013, fine particulate matter and, more broadly, outdoor pollution have been classified as “carcinogenic” by the International Agency for Research on Cancer (IARC).

Please note! The expression of these diseases depends on the chemical composition of theparticulate matter and, more generally, on the dose, the frequency of exposure and individual sensitivity. In this context, young people, the elderly and the sick constitute a population at risk.

DID YOU KNOW? Avoid intense physical exertion during peaks of particulate matter pollution. These are more likely to occur in winter due to a greater use of heating systems and less dispersion of pollutants (absence of wind, thermal inversion, etc.).