Health effects

Numerous investigations have shown links between exposure to air pollution and health effects, often what it seems without any threshold concentration. EU member countries are obliged to show compliance with air quality norms, today defined for PM10, NO2, CO, ozone and benzene, based on recommendations from WHO (2003)

Current EU legislation regulates the mass of inhalable particles (PM10). Recent findings indicate a stronger relation between health effects and fine particles PM2.5 (see figure below). WHO has therefore recommended that guidelines for regulation of the mass of the fine fraction, i.e. the particles with diameter below 2.5 µm (PM2.5) shall be developed. However, the typical urban aerosol has no natural division at 2.5 µm, rather it shows three peaks named as the coarse mode (µm particles), accumulation size mode (typical peak at 100-200 nm) and the nuclei size mode (peak at 10-20 nm). The smaller the particle, the deeper it will penetrate into the respiratory system. Ultrafine particles (diameter <100 nm) enters the alveolar region. Traffic exhaust particles have a number concentration peak at about 20 nm, which also is the size of maximum lung deposition rate. Particles may carry toxic materials on their surface, so small particles in high number concentrations, which gives a high surface area, can potentially carry more toxic materials into the lungs.

SMHI is involved in urban model development in order to assess exposure both to gaseous pollutants as well as particle mass and number concentrations.