6. Air Quality

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6. Air Quality

6A. Present situation

Present situation

Geographical Factors and Topographical Constraints

Our city is located in the temperate coniferous-mixed forest zone with cold, wet winters according to Köppen's climate classification. The mean temperature of the warmest month is at least +10 °C and the coldest up to -3, and it rains moderately in all seasons.

The city centre of Lahti is located in a valley between ridges (Fig. A1). This induces problems (inversion) with air quality during unfavourable weather conditions. The northern location also influences air quality. Inversion occurs during winter and especially during early spring, trapping air pollutants close to the ground and inhibiting dilution. Due to cold winters, there is a need for studded tires as well as for sanding and salting roads to prevent slippery conditions. Spring is especially challenging for air quality, when sand and pulverized asphalt rises into the air.

Ridges in Lahti

Figure A1. Ridges form a circle around the city centre (marked with a dashed line), trapping air pollution.

Extensive Monitoring

Despite being a small city (120 000 inhabitants), Lahti monitors air quality at five stationary automatic measuring stations (Fig. A2). In addition, Lahti has had a mobile station since 2015. The mobile station is relocated yearly. In 2016, it was located in Nastola (Rakokivi) (Fig. A2). Besides automatic monitoring of NOx, O3, PM10 and PM2.5, there are passive two-week monitoring pipes, in three different locations, to monitor VOCs. The measuring stations in Saimaankatu and Vesku represent the city centre, while Laune is located on a busy road. Kisapuisto is located at a recreational area and represents urban background air quality. Satulakatu is located away from the city centre and significant emission sources. VOC measuring stations are located in industrial and business areas, and close to residential areas, except for Laune, which is in a traffic area. There is one meteorological station (Vesku) that aids in analysing the data.

Air pollution measuring stations

Figure A2. Air pollution measuring stations in Lahti.

Sources of Air Pollution

Air pollution primarily originates from energy production and traffic. Of the annual mean NOx, about 55% originates from industry and 45% from traffic. For particulate matter (PM10 and PM2.5) (annual mean), about 40% originates from industry and 60% from traffic. Concentrations of PM2.5 are usually rather small in Finland. From time to time, long-range transboundary pollution caused by forest fires can be seen in the monitoring. There are a few small companies that use solvents, which generate VOC emissions, along with household wood combustion in residential areas. The proportion of air pollution from long-range transport is not estimated separately.

Concentrations of hourly NO2 (120 ug/m3) levels did not exceed in 2016; it may happen in traffic areas, but is unlikely in other areas. It is highly probable that the daily PM10 average concentration limit of 50 μg/m3 may be widely exceeded outside of the city centre, in areas that have been sanded.

Air Quality Index

Finland uses an air quality index based on national guidelines and limit values. The air quality index is calculated hourly. Air quality is classified as good, satisfactory, tolerable, poor or very poor. The City of Lahti is responsible for updating and monitoring the information, based on the collected data (Fig. A2). To inform the residents about air quality, data is sent to a national air quality portal, it can be followed in real-time at www.ilmanlaatu.fi.

In 2016, air quality was classified as good 67.3%, satisfactory 27.0%, tolerable 4.2%, poor 1.1% and very poor 0.4% of the time (Fig A3). There were 136 hours of poor or very poor air quality in 26 days. The reason for this was the high amount of particulate matter concentrations.

Air quality index

Figure A3. Air quality indexes in 2016 in Lahti.

Particulate Matter

Poor and very poor air quality index values (26 days in 2016) are nearly always caused by high PM10 concentrations. PM10 concentrations were high in March and April, due to large amounts of pulverized sand and asphalt, after the snow melt. At the Laune and Rakokivi measurement stations, the national guideline value of 70 μg/m3 (second highest daily value for a month) was exceeded in March as well as in April, in Laune.

The EU daily mean limit value of PM10 (50 μg/m3) was exceeded 18 times at the Laune station (35 allowed times). The annual mean concentrations of PM10 are below the EU limit value of 40 μg/m3 (Fig. A4, Tori’s measurement station was replaced by that in Saimaankatu in 2014, which is situated close to the previous location). The EU limit value of PM2.5 (25 μg/m3) was not exceeded in 2016, as usual. The highest daily means of each month were between 8 μg/m3 and 17 μg/m3. The latter was measured in January. The annual mean concentration of PM2.5 was 6 μg/m3.

Annual concentrations

Figure A4. PM10 annual rolling average concentrations: the city centre (Tori, Saimaankatu), a busy crossroad (Laune).

NOx Gases

NO2 concentrations were low level in 2016 (long-term mean or under it throughout the year). Generally, NOx concentrations remained around average, throughout the year. The effect of traffic is evident, as NOx concentrations follow traffic rhythms.

Annual mean concentrations of NO2 have decreased considerably, over the past decades (Fig. A5). The EU limit of 40 μg/m3 was never exceeded. In 2016, annual mean concentrations of NO2 were as follows: Vesku 23 μg/m3, Laune 15 μg/m3, Kisapuisto 8 μg/m3 and Rakokivi 7 μg/m3.

The NO2 EU hourly mean limit value (200 μg/m3) was never exceeded at any of the stations. The hourly mean values (second highest value per month), comparable to the national guideline value, varied at the measurement stations as follows: Vesku 44 - 79 μg/m3, Laune 27 - 81 μg/m3, Kisapuisto 17 - 52 μg/m3 and Rakokivi 12 - 39 μg/m3.

Mean consentrations

Figure A5. Annual mean concentrations of NO2 gases and trends of three monitoring stations 1993-2016.

6B. Past Performance

Air Quality Management

An Air Quality Action Plan (1997), is the basis for today’s actions and strategies. The most important measures for reducing air pollution, target road traffic. Thorough monitoring ensures that immediate action is taken and residents are warned if air quality deteriorates.

As a complement to national and European Union regulations, Lahti has additional local air quality regulations. These are included in the Environmental Regulations of the City of Lahti.

The City and local businesses have signed an agreement to monitor air quality. The businesses fund the monitoring work according to the polluter pays principle.

Sanding of streets causes dust, which is harmful to health. To minimize the pulverization of sand, a type of sand that causes less dust is selected. When air quality worsens in the early spring, we immediately inform our street cleaning operators. A large-scale and thorough street cleaning operation is carried out to minimize the period of bad air quality (Fig. B1). If cleaning is not reasonable yet, the streets are irrigated.

Street dust cleaning

Figure B1. Cleaning street dust is a key measure for improving air quality.

Promoting Sustainable Transportation and Walking

Pedestrian city centre:

  • Car-free zones in the city centre.
  • Pedestrian paths are widened.
  • Transformation of Aleksanterinkatu Street to a primarily pedestrian area, completed in November 2016 (cost 3.1 M€) (Fig. B2). Additional bicycle racks, parking for 1 100 bicycles.

→ At least 4 000 fewer cars, compared to 15 000 cars per day (in 2011).

 A great network of cycling paths: 532 km of combined pedestrian and cycling paths.

The main cycling network has a high maintenance level during the winter to promote winter biking.

2014 public transportation network reform:

  • Approximately 90% of local public transportation is operated by Euro VI (investment 1.5 M€).
  • Increased frequency of bus service.
  • New routes added (40% increase in kilometres).
  • Nearly all routes go through Lahti’s market square and the new Travel Centre.
  • In 2015, 82.8% of residents lived in the pedestrian/public transportation zone (maximum frequency for public transport: every 30 minutes; maximum distance to a bus stop: 250 m).

Lahti’s Master Plan is concentrating on consolidating land use and ensuring a population density of at least 15 inhab./ha enabling a good public transportation and cycling path network.

2016 a transportation hub was built uniting train and bus transportation, parking houses for bicycles and cars. Investment 18 M€.

To enhance smart mobility, in terms of commuting, we financed companies to execute smart mobility plans for their employees.

We own 8 electric cars, a few electric bicycles and traditional bicycles that can be used by city employees.

An electric bicycle test-ride was arranged by the city in 2016. A few of the residents were able to borrow the bicycle for a week and replace their car journeys with the e-bicycle.

Campaigns to support the use of public transport: On the World Car Free Day bus tickets on reduced price. The City gave free bus rides to commuters for a period of four months for 144 number of workers of the Department of Technical and Environmental Services.

Pedestrian paths

Figure B2. We have created widened pedestrian paths and car-free zones in the city centre over the past years.

As a result of these endeavours, Lahti’s residents are now using fewer cars and more bicycles and public transportation (Fig. B3).

Trasport modes

Figure B3. Many residents have switched from cars to bicycles, and in the future, to public transportation.

Ecosystem Services

Important ecosystem services have been mapped for built areas. The need to improve or keep particular ecosystem services is included in Lahti’s Master Plan.

Sustainable Energy

2010-2016 Consumers energy advisory in the Päijät-Häme project: energy counselling targeted residents and housing cooperatives in the Lahti region. This budgeted 77 000 € during 2014-2015 and then 25 000 € annually for 2016-2020.

In 2015-2016 The “Eco-efficient Energy Solutions” project developed an e-service for property owners and residents to assist in comparing different sustainable energy solutions. Investment 190 000 €.

Lahti Energy Ltd. (part of the Lahti City Group) has invested in energy efficient and sustainable district heating. The district heating network is extensive; over 90% of population and 99% of municipal buildings uses district heating. Over 95% of district heating is produced efficiently in the CHP-plant of Kymijärvi I-II.

Lahti Energy Ltd.:

  • Supports schools by educational material kits on energy saving.
  • Advises residents on solar power, delivers ready-made solar power packages to households.
  • Installed two electric charging points (for four cars) in Lahti, charging is free for registered users.

Public Information

  • Air quality can be followed in real-time at www.ilmanlaatu.fi.
  • SMS warning service: a message is sent if the air quality reaches a harmful level (Fig. B4).
  • Our website offers air quality reports from 2006 to 2016.
  • A Facebook posting is immediately set (on the Urban Environment Facebook page) if air quality reaches unhealthy levels.
  • Media releases are given to local media, when air quality deteriorates, and forecasts are compiled so that vulnerable groups may plan their actions and outings.


Mobile warning service

Figure B4. We use an SMS warning service to inform the residents about harmful levels of air quality.


Air quality has improved over the past few decades (Fig. B3).

Particulate matter and NOx gases

Figure B5. Significantly less particulate matter and NOx gases are emitted from traffic and industry today.

6C. Future Plans

Lahti City Strategy

Our goal: “We are internationally successful as a bold environmental city for people and businesses!” Environmental protection is at the heart of this strategy and taking care of the environment is one of the five promises. Lahti will invest in a circular economy and in developing a carbon neutral and sustainable resource managed city. We are committed to increasing the use of public transportation, walking and cycling.

Development Plan for Walking and Cycling 2025 [13]

We aim to achieve easy walking and cycling in the city. To promote sustainable transportation modes and lessen the negative effects of car traffic (e.g. pollution), three strategic goals have been set:

  1. Changing attitudes.
  2. Urban structure.
  3. Infrastructure (Fig. C1).

The city is planning to launch a bicycle borrowing system (long-term goal). Another preliminary decision has been reached for the long-run, whereby public transportation buses will change to electric buses and biogas will be enhanced in other logistics.

Better City Centre


Main cycling networkFigure C1. The main cycling network. The new, planned cycling paths are shown with a dotted line. Click map to enlarge.

The street network will undergo a change (Fig. C2). Vapaudenkatu Street is developed primarily for public transportation. Vapaudenkatu’s two-way, high-quality cycling path will be increased westward. Rautatienkatu Street (not highlighted on the map) will be further developed as a pedestrian zone. Most car traffic will be directed to an outer “circle” around the city centre, lessening the traffic inside the circle (see also Fig. A1). This enables additional cycling paths (e.g. along Vesijärvenkatu Street) to be constructed.

Road network in 2020

Figure C2. Road network in 2020. The city centre is developed into a pedestrian zone.

Directing Lorry Traffic Away from the City Centre

Construction of a bypass road will start in 2018. The bypass road will allow lorry transports to be directed away from the centre and enable the city centre to be developed into a pedestrian zone. Air pollution will be reduced in the centre and Mannerheiminkatu Road (currently main road no 12, red line) can be developed into a normal city street.

Although the new bypass will not reduce the total traffic volume in the city, it makes traffic smoother and promotes walking and cycling in the city centre, as well as reduces air pollutants where more people are affected.

Sustainable Energy

The Sustainable Energy Action Plan (SEAP) includes measures for more sustainable heating and electricity production, energy efficiency, traffic and traffic planning and increasing environmental awareness.

At least six new charging points will be installed by the Lahti City Group organizations.

In 2015-2018, Lahti Energy Ltd will invest 20 M€ in wind power, located mainly on the west coast of Finland.

Lahti Energy Ltd and the City Council have decided that a new biofuel power plant, Kymijärvi III, will be built in Lahti and, it should be operational by 2020 [15]. In 2015, 42.65% of the district heating was generated from renewable sources and, with the new biofuel power plant, this will rise to 80% The investment will cost 150 M€. The old coal-operated power plant, Kymijärvi I, will be phased out, which will improve air quality, by reducing emissions (SO₂, NO/NOₓ, PM).

Monitoring of Air Quality

Together with local businesses, we have decided to start monitoring the levels of benzopyrene B(a)P during certain time periods in winter 2017-2018. Since benzopyrene comes from traffic and burning wood, it will be measured in an older residential area.

Lahti has joined the Smart & Clean Foundation. The Smart & Clean foundation is setting up a comprehensive, city-wide, air quality system test bed in the Helsinki Region, which could be set up in Lahti, as well. This kind of air quality system would produce open data, and enable targeted measures to prevent and lower air pollution and its consequences.


In 2016, the Lahti City Group’s expenditures on air and climate protection amounted to 4.6 M€, investments were 0.9 M€. We will continue to invest in keeping our streets clean, reducing pollution from power plants and reducing traffic.

Public Information

There is a plan to put a mobile application (free of charge for users) into use where residents can access information on current air quality. The National Air Quality Portal will be integrated as a part of the national Finnish Meteorological Institute web pages at www.fmi.fi. It may improve visibility for inhabitants, as people tend to use the Finnish Meteorological Institute web pages to check the weather forecast. The new air quality service will replace the Air Quality Portal, by the end of 2017.



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