How Helsinki’s air quality has improved over the past 30 years

Dust particle concentrations can still present a tough challenge to beat, though

At the end of last week, Helsniki’s municipal website was proud to report that over the past three decades the city has drastically improved its air quality profile. The Finnish capital is generally a good place to fill up your lungs.

Sulfur dioxide concentrations have fallen by more than 90% and this gas is no longer a major air quality problem in that metropolitan area. Concentrations of nitrogen dioxide have also been halved. In contrast, the decrease in particle concentrations has not been as significant as the reduction in the other two pollutants.

Sulfur dioxide – the resounding success story

Sulfur dioxide (SO2) comes mainly from energy production and partly from emissions from ships. Sulfur dioxide levels fell, especially in the 1980s and 1990s, when emissions from energy production and industry were curtailed.

Sulfur emissions from road transport decreased with the transition to low-sulfur and sulfur-free fuel. Today, road transport is responsible for less than 1% of sulfur dioxide emissions in the Helsinki metropolitan area.

Sulfur dioxide concentrations have also fallen in ports, especially in the 2010s. These concentrations have been reduced by the tightening of emission standards for shipping in the Baltic Sea in 2010 and 2015.

Nitric oxide – NO_x to old cars

Nitrogen oxides (NO_x) in the breathing air come from emissions from transport, especially diesel cars and heavy vehicles. Nitrogen dioxide concentrations have fallen significantly at metering stations in the Helsinki Metropolitan Area over the past nearly 30 years. In the busiest places, the concentrations of NO_x in the exhaust gases have roughly halved from what they were when measurements began in the late 1980s.

The decline in nitrogen dioxide concentrations has been facilitated by the renewal of the car fleet and emission reduction techniques, as well as the reduction of emissions from the city’s public transit HSL bus fleet. The annual limit value for nitrogen dioxide was still exceeded in 2015. Today, the concentrations are below the annual limit value and the limit value is not expected to be exceeded in the future.

Fine particles, not quite in a fine condition yet

Respirable particles are mainly street dust in traffic environments. The most significant local sources of fine particles are emissions from traffic and wood burning, and the latter varies a lot due to weather conditions. 

Concentrations of particulate matter have decreased in the region over the years, but the decrease in concentrations has not been as significant as in the reduction of sulfur dioxide and nitrogen dioxide.

Concentrations of respirable particles have decreased by about a third of what they were when measurements began in the mid-1990s. The amount of street dust has been reduced by, among other things, intensified cleaning of the streets and dust binding with diluted calcium chloride solution, the use of a sand screen and a reduction in driving speeds.

The street dust season of spring 2021 was heavier on the capital city than in the previous year, partly because the winter of 2021 was colder and the streets still had to be sanded at the end of February. The other reason of course was the decreased traffic during the initial COVID lockdowns. Street dust was highest in March, but concentrations of respirable particles were also high in early April.