Human exposure to carcinogens in ambient air in Denmark, Finland and Sweden

The concentrations of seventeen pollutants (particulate mass fractions PM2.5 and PM10, a range of metals, inorganic gases and organic compounds) are for the first time analyzed in a screening of the carcinogenic risk at a resolution of 1 × 1 km2 in ambient air in three Nordic countries. Modelled annual mean air concentrations in 2010 show no exceedances of the EU air quality limit, guideline or target values. The only modelled exceedance of US-EPA 1:100,000 cancer risk concentrations (0.12 ng/m3, US-EPA IRIS, 2015) occurs for B(a)P in Denmark, for approximately 80% of the Danish population. However, the EU target value threshold of 1 ng/m3 for B(a)P is not exceeded in the modelled values in any parts of Denmark. No emission data for B(a)P were available for the whole domain of the other two considered Nordic countries and important uncertainties are still related to the emissions. Long-range transport is significant for the concentrations of all of the considered pollutants, except for B(a)P that commonly originates mostly from local residential wood combustion. The ambient air concentrations of NOx, SO2, Cd, Cr and Pb also have significant contributions from national sources; 45-65% for NOx and SO2, and for the metals from 15 to 60% in urban areas and from 1 to 20% in rural areas, within the considered Nordic area. High national contributions occur especially in urban air, due to primarily road traffic, residential wood combustion, energy production and industrial point sources. It is recommended to monitor the influence from residential wood combustion more extensively, and to analyze longer time trends for long-term human exposure.