Air Pollution Emissions

We proactively work to minimize our emissions to air through local action plans at our mines and smelters.

Our approach to emissions

We focus on metals and sulfur dioxide as well as on reducing diffuse emissions (dust). Local action plans are being developed both at mines and smelters.

Significant air emissions

Significant air emissions deriving from Boliden’s operations are nitrogen oxides (NOx), sulfur oxides (SOx), metals and dust. The most common of the sulfur oxides is sulfur dioxide (SO2), and we generally use the expression “sulfur dioxide” to describe these emissions. The figures for SO2 and NOx disclosed in the table are the direct measured emissions from sources at Boliden’s smelters. The figures for metals and dust include direct-measured emissions from smelter stacks but exclude diffuse emissions. Extensive projects to map diffuse emissions and their sources have been carried out at some smelters, such as at the Bergsöe and Kokkola sites.

Deposits and runoff of, among other things, sulfur, nitrogen and metals are measured and followed up at Boliden’s sites. The sulfur deposition and the total deposition of acidifying substances, which are counted as hydrogen ions, and the deposition of inorganic nitrogen have reduced in recent years.

Diffuse emissions are generated at both mines and smelters and the environmental impact is related to dust particles containing metals being dispersed by the wind. All our operations work systematically to reduce particle emissions to the air, for example by the enclosure of dust-generating equipment and by salting and watering roads. Diffuse emissions are monitored but are difficult to quantify in an aggregated manner.

Emission reduction efforts

Our efforts to reduce emissions are based on an overall analysis of the environmental impact. The impact and risk assessments are revised on a regular basis, as are the measures to be taken. The work is controlled and conducted by each individual Business Unit, as local circumstances may differ. Follow-up at Group level is conducted monthly.

SO2 emissions to air are mainly attributable to gases generated during the smelting processes or in sulphuric acid production at sulphuric acid plants, which is a by-product of the smelting process. SO2 gases from smelting processes are mainly sent to the sulphuric acid plant where sulphuric acid is produced from the gas. The amount of SO2 emitted during the process depends on factors such as process stability, the efficiency of the gas cleaning systems, and the amount of sulfur in the raw materials. Thus, one way of reducing emissions is to maintain a stable smelting process and to conduct ongoing, effective maintenance work and process control. The monitoring and control of abatement systems for effective gas cleaning is important work that is continuously carried out.

The SO2 emissions to air decreased slightly during 2022 at Boliden Smelters within the limits of natural variations. The metal emissions to air have decreased due to improved filtration techniques at Boliden’s smelters.

Emissions to air are mainly based on periodic monitoring in accordance with monitoring programs approved by the authorities and the applicable national standards. Emissions from fuels are calculated using the fuel property data provided by the supplier. For the protection of the environment and human health, the ambient air quality is monitored continuously close to Boliden’s sites or at the border of living areas. The following pollutants are monitored: Particulate matter (TSP, PM10, PM2.5), SO2 and NOx. Metal concentrations in particulate matter (PM-10) are analyzed regularly. Data received is compared with valid ambient air limit and target values. Emissions of Volatile Organic Compounds (VOCs) are not considered significant and are therefore not disclosed.

Emissions to air
(metric tons)












Particulate matter




Metal emissions to air




Metal emissions to air (mass)




Where of lead (Pb)




Where of mercury (Hg)








1) The model for the calculation of metal-equivalence is based on the framework for the Natural Capital Protocol.