Current air quality

For up to date information on current air quality across Wales, including Monmouthshire, please visit the Welsh air quality website.

Local air quality management

Environmental health monitor air pollutant levels to assess current and future air quality. This information is used to determine whether we are meeting the air quality objectives of the UK National Air Quality Strategy.

The strategy plans to improve air quality based on reducing concentrations of seven key pollutants. We are responsible for carrying out this strategy and will work with local people, commerce, industry, environmental groups, Natural Resources Wales and the Welsh Government.

The seven pollutants each have air quality objective levels that should not be exceeded.

The process has several stages:

We review and assess air quality in a phased approach on a three year cycle.

In the first year an updating and screening assessment is undertaken to identify those matters that have changed since the last review and assessment, which might lead to a risk of an air quality objective being exceeded – If there is a risk that any changes may be significant then a screening assessment is carried out

In years two and three a progress report is undertaken

Where an updating and screening assessment or progress report has identified a risk that an air quality objective will be exceeded at a location with relevant public exposure a detailed assessment is undertaken to identify whether or not a likely exceedance will occur

If the detailed assessment identifies an exceedance an air quality management area is declared

When an air quality management area has been declared a further assessment is undertaken to confirm the exceedance, define what improvement in air quality is required and provide information on the source of the pollution

Following the further assessment an air quality action plan is produced to identify measures to achieve the required reduction in emissions

For several years, we have been monitoring pollutants likely to affect air quality. This will determine whether objective levels are being met and whether any AQMAs are needed.

Currently there are two areas in the county that are in exceedance of the nitrogen dioxide objective level. These are Bridge Street in Usk and part of the A48 in Chepstow which includes Hardwick Hill. These areas have been declared air quality management areas and action plans have been produced for both.

Annual review and assessment reports

The latest review and assessment report is the 2017 Progress Report which presents monitoring data for January – December 2016, along with an update on progress towards the Chepstow and Usk air quality action plans.

The Progress Report identified that detailed assessments are not required and is the third of the 2015-2017 three year phase of review and assessment.

In addition to the regular annual reports, Natural Resources Wales undertook a study on the A40 with their Mobile Monitoring Facility monitoring PM10, PM2.5, nitrogen dioxide, sulphur dioxide and carbon monoxide December 2014 and June 2015.

The study indicated that all of the air quality objectives were met in 2015 at relevant receptors. A further summary is provided in the 2016 Progress Report, and the full report is also available:-

Study of Ambient Air Quality at Monmouth

The next report in 2018 will be the first in the 2018-2020 round of review and assessments.

Detailed assessments will be required if a risk is identified that an air quality objective will be exceeded at a location with relevant public exposure.

Pollutants in Monmouthshire

The review and assessments have shown that for all pollutants air quality in Monmouthshire is meeting the objectives, with the exception of nitrogen dioxide at two locations. The cause of the two exceedances is road transport.

The following roads have been shown to cause high levels of nitrogen dioxide:

  • Bridge Street, Usk
  • A48, Hardwick Hill/Mount Pleasant at Chepstow

Please see the Usk and Chepstow action plans and 2017 Progress Report for more details.

You can also view the 2016 report, 2015 report2014 report2013 report2012 report and 2011 report.

In addition the following roads have been at risk of exceedance of the nitrogen dioxide objective level and will continue to be monitored closely.

The junction of the A40 and A466 Wyebridge Street in the vicinity of Monmouth Boy’s School

Merthyr Road, Abergavenny

Nitrogen dioxide and health

For information about how exposure to high levels of nitrogen dioxide and other key air quality pollutants, can effect health please visit the Welsh air quality website.

Air quality monitoring

In Monmouthshire the major source of pollution is from road transport sources, therefore we monitor for the three key pollutants associated with vehicle emissions, these are nitrogen dioxide, PM10 and PM2.5.

PM10 & PM2.5

PM10 and PM2.5 are the very fine particulates that can be carried deep into the lungs. Currently there are no exceedances of PM10 or PM2.5 objectives in Monmouthshire.

Nitrogen dioxide

The air quality objectives for nitrogen dioxide are:

Annual – 40 micrograms per cubic metre (µg m-3)

Hourly – 200 micrograms per cubic metre (µg m-3) not to be exceeded more than 18 times a year

The annual objective level is being exceeded in locations along Bridge Street in Usk and Hardwick Hill in Chepstow.

Types of monitoring

We use two types of monitoring for nitrogen dioxide concentrations along our road networks and one type for PM10 and PM2.5.

Nitrogen dioxide diffusion tubes

Diffusion tubes are small and relatively inexpensive and do not need a power supply, therefore we can fix them to lamp posts and houses in many locations in Monmouthshire to build up a good monitoring network close to where people live. Nitrogen dioxide in the air enters the tubes and gets absorbed onto a filter. Every month an officer changes the tubes and they are analysed in a laboratory.

Currently there are 41 diffusion tube monitoring sites in Monmouthshire located in Abergavenny, Monmouth, Usk and Chepstow. We have previously undertaken monitored in Raglan, Magor and Undy, however as levels were below the objective levels the tubes were re-located to more at risk locations.

Automatic monitoring

Automatic monitoring is a more expensive, but more accurate way to measure air quality. We currently have one automatic monitoring station located on Hardwick Hill in Chepstow. This unit is capable of continuously monitoring several pollutants. Current air quality data monitored by the automatic monitoring station in Chepstow can be found by visiting the Welsh Air Quality website and selecting Chepstow from the map.

There are three analysers in the monitoring station which monitor the key vehicle emission pollutants:

Nitrogen dioxide and nitric oxide

PM10 (small particles less than 10 µm diameter)

PM2.5  (small particles less than PM2.5 diameter)

Nitrogen dioxide is monitored with a chemiluminescent analyser and PM10 and PM2.5 are measured with TEOM-FDMS analysers. The monitors allow comparison with the annual, 24 hour, and hourly objectives.

Bias adjustment of nitrogen dioxide diffusion tube data

As the nitrogen dioxide automatic monitor is more accurate than the diffusion tubes we undertake a co-location study by exposing 3 diffusion tubes next to the Chepstow automatic monitor. The diffusion tube results can then be adjusted to take the difference into account. To make the tubes more accurate we also use data from other councils who undertake co-location studies around the UK.