Radon in air

Figure 1: Radon potential in the Fylde

Radon is a naturally occurring radioactive gas that is released from the ground and is present everywhere. Outdoor radon levels in the UK are low, typically a few Becquerels per cubic metre of air.

Indoor radon levels vary across the UK from less than ten to thousands of Becquerels per cubic metre of air. More information is available at www.UKradon.org.

The 2014 Public Health England (PHE) report (PHE-CRCE-009) on the potential public health impact of shale gas in the UK recognised that radon may be released to the environment from shale gas activities but at levels that are not expected to result in significant additional radon exposure. The report recommended the establishment of baseline radon levels in areas of interest for shale gas activities.

In this project, Public Health England is monitoring the existing outdoor and indoor radon concentrations in the Fylde, Lancashire.

Radon Affected Areas are those where at least 1% of homes are expected to have high radon levels. The area of Fylde in Lancashire is not a Radon Affected Area. This is illustrated in Figure 1.

Indoor radon monitoring

To establish the local baseline range of indoor radon levels, householders were invited to participate in this research by accepting radon tests in their homes. Three areas were selected for indoor radon monitoring in the Fylde:

  • the area around Little Plumpton, at about 2–3 km from the Preston New Road (PNR) extraction site;
  • the area around Roseacre Wood, another site where shale gas extraction has been considered;
  • the area around Woodplumpton, a control site at about 10 km from PNR. The control site was chosen to be situated within a similar distance of both the PNR and Roseacre Wood sites.

Addresses were selected randomly in and around Little Plumpton, Roseacre Wood and Woodplumpton. Invitations to take part in the baseline survey were issued by post in April 2017, following a well–established PHE procedure. Householders who accepted the invitation were sent passive radon measurement packs.

Figure 2: PHE standard pack of passive radon detectors.

Each test consists of PHE’s standard pack of 2 passive detectors, shown in Figure 2, that are placed for 3 months in an occupied bedroom and living area. Indoor radon will be monitored over the length of this study in the selected houses. Each participant will receive several 3-month packs. In addition, each home received detectors to carry out monitoring for a longer continuous period.

The analysis of the results for the first 3–month period (May–July 2017) is presented here. Annual average radon concentrations were calculated, employing seasonal correction factors as outlined in the PHE Validation scheme (Howarth C B and Miles J C H, 2008). Indoor radon concentrations follow a log–normal distribution. Parameters of the distribution in each area: arithmetic mean (AM), geometric mean (GM) and geometric standard deviation (GSD), are reported in Table 1. The results for the homes around Little Plumpton, Roseacre Wood and Woodplumpton are consistent with the expected low radon potential for this area.

Area(number of homes)   First 3–month results (May–July 17), Bq/m3
Range Arithmetic Mean (AM) Geometric Mean (GM) Geometric Standard Deviation (GSD)
Little Plumpton (36) 6–92 40 33 1.9
Roseacre Wood (40) 10 –77 30 26 1.7
Woodplumpton (34) 8–92 29 25 1.7

Local radon distributions for the first 3–month test in homes in and around Little Plumpton, Roseacre Wood and Woodplumpton (control area) are given in Figures 3 a, b and c, respectively.

Figure 3: Reported indoor radon concentrations in the areas around Little Plumpton.
Figure 3: Reported indoor radon concentrations in the areas around Roseacre Wood.
Figure 3: Reported indoor radon concentrations in the areas around Woodplumpton.

Outdoor radon monitoring

This part of the project will establish the baseline outdoor level of radon in air. Two areas have been selected for outdoor radon monitoring in the Fylde:

  • the area around Little Plumpton at about 2 km from the Preston New Road (PNR) site (9 sampling points);
  • the area around Woodplumpton at about 10 km from the PNR site, control site (10 sampling points).

Passive radon monitors, very similar to those used routinely in homes, have been placed for 3 months or longer in small aluminium–wrapped plastic pots in discreet open–air locations. The outdoor radon monitoring pack and placement of detectors are shown in Figure 4 and Figure 5.

Figure 4: PHE outdoor radon monitoring pack.
Figure 5: Placement of outdoor detectors.

Results from the first 3–month period (March to May 2017)

Two small aluminium–wrapped plastic pots placed at each sampling point (see Figure 5), contain four 3–month and four 1–year passive detectors to record the radon concentration. The average radon concentrations at each sampling point estimated from the first 3–month measurements in the areas around Little Plumpton and Woodplumpton are presented in Figures 6a and 6b.

The results averaged for each area for the 3–month period indicate that the average radon levels were the same around the PNR and control sites:

  • 4 ± 1 Bq/m3 for the area around Little Plumpton;
  • 4 ± 1 Bq/m3 for the local control area around Woodplumpton.

The above results are similar to those measured in previous studies (Wrixon et al., 1988). It should be noted that the 3–month results are close to the detection limit for the passive radon detection technique.

Figure 3: Reported indoor radon concentrations in the areas around Little Plumpton.
Figure 6: Average radon concentrations (with error bars) at the sampling points around Woodplumpton.

Monitoring near the Preston New Road site

Baseline monitoring is also being carried out in the project enclosure near the PNR site. An active AlphaGUARD monitor was placed to investigate the short–term variations in radon concentrations. Passive radon monitors were also installed to compare the AlphaGUARD results with the long–term average radon concentrations.

The data from the AlphaGUARD for the period March–June 2017 are plotted in Figure 7. The background of the instrument was taken into account when the data were processed. The radon data, taken at 1–hour intervals, are log–normally distributed. The distribution parameters for the above monitoring period are given in Table 2. The average radon concentrations measured with the passive detectors in the enclosure was 7 ± 2 Bq/m3. The values are in a good agreement with the arithmetic mean of the distribution, 6 Bq/m3, in Table 2. The time series for radon, as measured (without background correction), are given in Figure 8.

Figure 7: AlphaGUARD data from the enclosure near the Preston New Road site.
Figure 8: Time series of radon concentrations as recorded by the AlphaGUARD from the enclosure near the Preston New Road site.

Period of monitoring Bq/m3
March–June 2017 1–35 6 5 1.9


Howarth, C B, and Miles, J C H. 2008. Validation scheme for organisations making measurements of radon in dwellings: 2008 revision. Chilton, HPA–RPD–047.

Miles, J C H, and Algar, R A. 1988. Variations in radon–222 concentrations. Journal of Radiological Protection 8 (2), 103–106.

Kibble, A, Cabianca, T, Daraktchieva, Z, Gooding, T, Smithard, J, Kowalczyk, G, McColl, N P, Singh, M, Mitchem, L, Lamb, P, Vardoulakis, S, and Kamanyire, R. 2014. Review of the Potential Public Health Impacts of Exposures to Chemical and Radioactive Pollutants as a Result of the Shale Gas Extraction Process, Chilton, PHE–CRCE–009.

Wrixon, A D, Green, B M R, Lomas, P R, Miles, J C H, Cliff, K D, Francis, E A, Driscoll, C M H, James, A C, and O’Riordan, M C. 1988. Natural Radiation Exposure in UK Dwellings. Chilton, NRPB–R190.


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