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Background to air pollution measurement and monitoring

This page outlines our operations for monitoring air pollution.

Why do we monitor air pollution?

Air pollution has been monitored in the UK for many years. The council has participated in national networks providing information on air quality in the borough for 25 years. 

The information we collect is used to help us review and assess air quality in the borough, to measure whether air quality standards are being met, to provide good local information for policy decisions and provide the community with information on the air it breathes.

What pollutants are monitored?

Environmental Health Services continuously measures levels of air pollutants nitrogen dioxide (N02) and particulate matter (PM10) at Cable Street and Dalton Square in  central Lancaster. Measurements are also made of nitrogen dioxide using inexpensive equipment (diffusion tubes) at around 50 locations across the Lancaster district.

How do we monitor?

Air pollution in the Lancaster district is monitored by the Environmental Protection Team. There are two main types of air pollution monitoring equipment which are routinely employed; Passive Sampling (non-automatic) and Continuous Analysers (automatic). We use a combination of the two techniques together.

Passive Sampling (non-automatic)

Lancaster City Council has about 50 passive sampler sites monitoring nitrogen dioxide using diffusion tubes. Diffusion tubes provide an inexpensive method of monitoring air quality at multiple locations. They provide general indications of concentrations and trends of pollutants over a period of time.

The tubes are usually mounted to lamp posts or building frontages to give readings over a period of a month. Monthly results are then compared with the results from automatic monitoring stations and corrected to provide an annual average concentration. The main benefit of using this method is the relatively low cost, allowing us to carrying out monitoring at a wider range of locations.  This is particularly useful when considering changes brought about by new development or changes in traffic. The deployment of diffusion tube sites is reviewed on an annual basis.

Location of diffusion tube sites

Continuous Analysers (automatic)

We have two automatic monitoring station continuously measuring air pollution levels at Cable Street and Dalton Square in Lancaster city centre. The statiosn provide a more expensive method of air quality monitoring compared to the passive sampling, however the information collated is more accurate. The monitoring station at Cable Street contains two analysers, one  measuring nitrogen dioxide (NO2) and the other fine particulate matter (PM10).   The station at Dalton Square monitors nitrogen dioxide only. Air is continuously pumped into each analyser and the level of pollutant in the air is recorded. The pollution levels are stored by a data logger and accessed remotely by a computer and modem.

Further information regarding the monitoring of pollutants is provided in our air quality review and assessment reports.

Where do we monitor?

Environmental Health Services monitors pollution levels at many sites across the district. Unfortunately, we are not able to monitor every street, so sites have been chosen to represent different locations across the borough. Some sites have been selected where air pollution levels might be highest or present particular threats. Sites fall into two categories – roadside or background depending on the distance from a busy road.

There are about 50 diffusion tubes in all, providing data monthly averaged measurements of nitrogen dioxide.

The continuous monitoring stations are located on Cable Street in Lancaster, opposite the bus station and inside Dalton Square next to the town hall in Lancaster.

Last updated: 08 October 2020

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