Radon in air

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 PHE report (PHE–CRCE–009, 2014) 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.

Figure 1: radon potential of the Vale of Pickering

In this project Public Health England is monitoring the existing outdoor and indoor radon concentrations in the Vale of Pickering, Yorkshire.

Radon Affected Areas are those where at least 1% of homes are expected to have high radon levels. Established UK advice is that homes in radon Affected Areas should be monitored for radon. Much of the Vale of Pickering is not a radon Affected Area. There are some radon Affected Area areas towards the edge of the Vale. This is illustrated in Figure 1. Monitoring locations include both types of area.

Indoor and outdoor radon monitoring in the Vale of Pickering

The programme outlined here aims to obtain baseline results for the indoor and outdoor radon levels in and around the Vale of Pickering. The main area of the Vale is not a radon Affected Area so less than 1% of homes are expected to be above the UK Action Level, which is 200 Bq/m3. However, at around 5 to 8 km to the north and south of the centre of the valley, there are areas of naturally elevated radon potential. In these areas there is a higher probability for homes to have elevated radon levels.

Indoor radon monitoring

Figure 2: PHE standard pack of passive radon detectors

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. Addresses were selected randomly in and around Kirby Misperton, Little Barugh, Yedingham, Pickering and Malton.

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 received several 3–month packs. In addition each home received a pack to carry out monitoring for a longer continuous period.

Results from the four 3–month tests covering the period from December 2016 to December 2017 are presented in Table 1. The 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). The distribution parameters assuming log–normality confirm that homes in Kirby Misperton and Little Barugh are situated in areas with low radon potential while Pickering is situated in an area with higher radon potential (a radon Affected Area). For Malton, the probability assessment was inconclusive due to a reduced statistical power; results from only a dozen properties were available. Malton is classified as a radon Affected Area from previous studies (Miles et al, HPA–RPD–033, 2007).

(number of homes)

First 3–month results
Second 3–month results
Third 3–month results
Fourth 3–month results
Range GM GSD Range GM GSD Range GM GSD Range GM GSD
Kirby Misperton
and Little Barugh (27/27/29/28)
9–60 22 1.6 11–80 26 1.6 11–110 39 1.7 7–80 30 1.7
Yedingham and surrounding
8–80 25 1.9 10–130 29 1.9 12–240 41 2.3 9–130 32 2.1
7–400 41 2.8 9–350 47 2.7 9–410 52 2.9 7–450 49 2.9
13–60 29 1.7 10–80 27 1.7 8–60 26 1.8 11–50 31 1.7

Outdoor radon monitoring

This part of the project will establish the baseline outdoor level of radon in air. Outdoor radon monitoring is being carried out at a range of locations.

Passive radon monitors, very similar to those used routinely in homes, have been placed in small aluminium wrapped plastic pots in discreet but open-air locations for 3 months or longer. Four 3–month and two 1–year passive detectors were used to record radon concentrations at each monitoring point.

The outdoor radon monitoring pack and placement of detectors are shown in Fig 3 and Fig 4.

Figure 3: PHE outdoor radon monitoring pack.
Figure 4: Placement of outdoor detectors.

Four sites were selected for outdoor radon monitoring in the Vale of Pickering around Kirby Misperton (the area closest to the KMA site), Yedingham (control site), Pickering and Malton (sites in radon Affected Areas). One site in Oxfordshire was selected as an additional control.

The 3–month monitoring period in the Vale of Pickering was replaced by a 6–month monitoring period in April 2017. The results from the second year of monitoring (fifth 3–month, sixth 3–month and first 6–month monitoring periods) were plotted and compared with the result obtained from the 1–year test (October 2015 to October 2016), where these are available. The information for each sampling point in the area around Kirby Misperton, Yedingham (control area), Pickering and Malton are shown in Figures 5 to 8, respectively. The results for each detector at each location for each period were averaged and plotted. It was not possible to obtain results for all sites as some of the detectors were removed or damaged during the measurement period due to vandalism. This was most evident in the Malton area. Some sites where this damage occurred early on in the programme were re-located; for these monitoring points the 1-year monitoring results were not available.

Figure 5: average radon concentrations at the sampling points around Kirby Misperton.
Figure 6: average radon concentrations at the sampling points around Yedingham.
Figure 7: average radon concentrations at the sampling points around Pickering.
Figure 8: Average radon concentrations at the sampling points around Malton.

The results from the control area in Oxfordshire are shown in Figure 9. The points were located in private gardens. Monitoring was carried out for 15 months from October 2015 to January 2017. In January 2017 one participant left while 3 new participants joined the programme. Where available the averaged results from the four 3–month monitoring periods at each sampling point in the control area from January 2017 to January 2018, were plotted and compared with the 1–year test carried out previously from October 2015 to October 2016.

Figure 9: average radon concentrations at the sampling points in Oxfordshire.

Monitoring at the KMA enclosure

The data from the AlphaGUARD continual radon monitoring instrument, placed in the enclosure at the KMA site for the six 3–month periods between April 2016 and October 2017 were analysed. The inherent background of the instrument of 3 Bq/m3, resulting from the longer half–life alpha emitting radionuclides (from environmental exposure and materials within the instrument), was taken into account when data were processed. The radon data, taken at 1 hour intervals, are log–normally distributed. The distribution parameters for the above monitoring periods are given in Table 2. The average radon concentrations measured over the six monitoring periods were in the range 4 to 6 Bq/m3. In order for a comparison to be made between the outdoor radon concentrations measured with the instrument and the other outdoor results, passive monitors were also placed in the enclosure at the KMA site.

The average radon concentrations measured using 10 passive detectors are similar to the arithmetic means (AM) of the distributions measured with the AlphaGUARD for these periods as shown in Table 2. This demonstrates a good agreement between the two different measurement techniques.

A graph showing the raw data obtained from the AlphaGUARD, without background correction, is given in Figure 10. No data were collected for a short period in July 2016 when the instrument was removed and returned to PHE Chilton for downloading of data.

Period of monitoring

AlphaGUARD Passive detectors
Bq/m3 Bq/m3
Range Arithmetic Mean (AM) Geometric Mean (GM) Geometric Standard Deviation (GSD) Arithmetic Mean (AM) Standard Deviation (SD)
April16–July16 1–46 5 5 2.0 4 1
July16–October16 1–81 6 4 2.4 8 1
October16–January17 1–50 6 4 2.5 7 1
January17–April17 1–29 4 3 2.3 5 1
April17–July17 1–47 5 3 2.4 - -
July17–October17 1–38 5 3 2.4 7 1

Figure 10: time series of radon concentrations recorded by AlphaGUARD between April 2016 and October 2017.


Contact BGS enquiries for further information.