Particulate matter found in Norwegian cities and towns consists of a complex mixture of particles of different size and composition. On dry roads during autumn, winter and spring, particles from road surface wear constitute a large proportion of total airborne dust, which contributes significantly to the exposure of people who are near busy roads.
“The smallest particles consist mainly of combustion particles (fine particles) from exhaust gases and wood-burning. In addition, traffic leads to road surface wear and crushing of road grit which forms larger, coarse particles. These particles are small enough to penetrate the lungs and lead to worsening of disease for people with respiratory problems. Therefore it is important that the government uses several measures to reduce levels of particulate matter, so that the air in Norwegian cities is good for everyone,” said department director Per Schwarze, referring to several international studies.
Coarse particles produced by road surface wear from studded tyres can trigger health problems, according to research findings based on population studies and experimental studies. A Swedish research group recently investigated the formation of particulate matter and studded tyre use by testing different road surfaces and car tyres. Analysis of size distribution showed that the particles were formed in a size that could penetrate deep into the lungs (“Road Dust Conference” in Stockholm, October 2010).
In several population studies in different countries, a correlation has been found between increased levels of particulate matter and aggravation of existing respiratory or cardiovascular disease after short and long-term exposure.
A comparison of short-term studies suggests that small particles (mainly combustion particles) and larger particles (mainly wear particles) are associated with adverse health effects.
For chronic obstructive pulmonary disease (COPD), asthma and hospitalisation for respiratory problems, the relationship is stronger than or at least as strong for coarse particles as for finer particles. The fact that all types of particles trigger health effects is now supported internationally by scientists working with these issues, as well as by the World Health Organisation (WHO).
In many experimental studies in cells and animals it has been shown that pure mineral particles and coarse dust particles give at least as high inflammatory reactions as smaller combustion particles.
Studies from the Norwegian Institute of Public Health also show this, but also that there is a significant variation between different types of stone types used in road surfaces. Moreover, the NIPH has studied particulate matter collected in Oslo and other European cities. The results showed that the coarse particles gave effects that were similar to fine particles.
Who is at risk?
Many studies have shown correlation between particulate concentrations and deterioration and disease. This is particularly relevant for those who have a respiratory disease like asthma or COPD, and for those who have a cardiovascular disease. This means that the release of particulate matter triggers health effects at much lower concentrations in these risk groups than in the healthy part of the population.
There is insufficient knowledge to say how low the levels need to be to avoid health effects, even among the sickest.
Facts about laws and regulations
When it comes to air quality, there are slightly different goals and limits for what is acceptable.
The Pollution Control Act contains limits for air quality. These are partly based on practical and economic considerations – not just on health. The municipalities are responsible for complying with the regulations in the Pollution Control Act. Today these limits are exceeded in some Norwegian towns and cities.
Air quality criteria:
The air quality criteria developed by the Climate and Pollution Agency (formerly SFT) and the Norwegian Institute of Public Health is only based on health. These are lower than the limits. Reaching these levels will be a major challenge for Norwegian cities and towns in the future.
The national targets set by the Norwegian authorities are more stringent than the statutory limits, but not as stringent as the air quality criteria.