When measuring air quality impacts of construction work it is necessary to measure the emission of dust particles. This can now be done by recording the dust in two distinct ways which reflect the typical concerns. The off-site measurements are carried out in two ways.
The use of a proprietary technique (Dustscan) using ‘sticky pads’ which are left exposed for a period and then examined. This particular scheme has been validated and produces some measurement of the deposition and an indication of the direction from which the dust may have originated.
The use of an electronic system which measure dust both as total suspended particulates (TSP) and pm10. The equipment also is cable of measuring wind speed and direction etc.
The concerns around air borne particulates relate to potential human health risks the soiling caused to items like cars, window sills, etc. and potential health effects. Visible soiling tends to be caused by larger particles which will be picked up by the Dustscan sticky pads. It is generally believed that the most significant health effects are caused by very small particles which can penetrate to the bottom of the lung. These are accepted as being 10 microns or smaller and are referred to as pm10 particles. These are measured by the electronic equipment together with TSP, wind speed and direction. Other weather information is also gathered at the Knighton site.
The monitoring stations, while installed to monitor the EDF development, monitor the environment at their location and elevated levels are not necessarily due to EDF activity.
Other sources of large particulates locally may include agricultural and horticultural work, open burning e.g. bonfires, wood burning and other construction works. Pm10’s may arise naturally from sea salt from the estuary, pollen and fungal spores. Manmade sources can include exhaust gases from trucks, cars and garden equipment, controlled combustion e.g. oil fired central heating, closed wood burners, agricultural and horticultural activities including mowing and construction activities.
Additional information on more general air quality issues in West Somerset and the surrounding areas can be found on our air quality page.