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. Invites were issued by post in late 2015, following a well–established PHE procedure. Householders who accepted the invitation to take part in the baseline survey were sent passive radon measurement packs.

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.

The analysis of the results for the four 3–month periods (December 2015 to December 2016) is presented here.

Local radon distributions in the four selected areas in the Vale of Pickering: Kirby Misperton and Little Barugh, Yedingham and surrounding area, Pickering, and Malton are depicted in the Figure 3 a, b, c and d, respectively. Indoor radon concentrations follow a lognormal distribution. Parameters of these distributions, arithmetic mean (AM), geometric mean (GM) and geometric standard deviation (GSD), assuming radon log-normality are reported in Table 1.

Figure 3: indoor radon concentrations in the area of Kirby Misperton and Little Barugh.
Figure 3: indoor radon concentrations in the area of Yedingham.
Figure 3: indoor radon concentrations in the area of Pickering.
Figure 3: indoor radon concentrations in the area of Malton.

(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)
9–41 18 1.5 13–69 25 1.5 16–110 37 1.6 20–104 41 1.5
Yedingham and surrounding
9–72 21 1.9 10–97 26 1.8 17–170 39 1.9 21–43 46 1.8
6–270 40 2.7 9–450 44 2.6 13–460 56 2.6 17–619 71 2.5
12–170 36 2.1 11–240 39 2.1 8–150 34 2.3 20–171 45 1.7

Outdoor radon monitoring

This part of the project aims to 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. The outdoor radon monitoring pack and placement of detectors are shown in Fig 4 and Fig 5.

Figure 4: PHE outdoor radon monitoring pack
Figure 5: placement of outdoor detectors

Four sites have been selected for outdoor radon monitoring in the Vale of Pickering and one site in Oxfordshire:

  • Area around Kirby Misperton – 15 sampling points
  • Area around Yedingham, control site – 8 sampling points
  • Area around Pickering – 9 sampling points
  • Area around Malton –6 sampling points, measurements started in April 2016
  • Area around Chilton in the Vale of White Horse, Oxfordshire, control site – 8 sampling points.

Four 3–month passive detectors and 2 longer term detectors were used to record radon concentrations at each sampling point. The estimated average radon concentrations for the five 3–month monitoring periods (October 2016 – December 2016) were plotted and compared with each other at each sampling point in the area around Kirby Misperton, Yedingham (control area), Pickering and Malton in Figure 6 a, b, c and d, respectively. Results for the control site in Oxfordshire are given in Figure 7. Results from the 1–year test, are included where these are available. Aggregated results for outdoor monitoring from the five measurement periods are given in Table 2. Although the 3–month results are close to the detection limit for the technique they are consistent with the results for the 1–year period (Figures 6 and 7).

Figure 6a: average radon concentrations at the sampling points around Kirby Misperton.
Figure 6b: average radon concentrations at the sampling points around Yedingham
Figure 6c: average radon concentrations at the sampling points around Pickering.
Figure 6d: average radon concentrations at the sampling points around Malton.

Figure 7: average radon concentrations at the sampling points in the Vale of White Horse, Oxfordshire.


First 3–month
Second 3–month
Third 3–month
Fourth 3–month
(Jul–Oct 16),
Fifth 3–month
7±2 7±2 4±2 9±1 4±1
Yedingham 9±4 7±2 5±2 7±1 4±1
Pickering 6±2 10±3 5±2 8±1 4±1
Oxon 11±3 6±2 5±2 8±2 6±1
Malton -- -- 6±3 8±1 5±1

Monitoring at the KM8 enclosure

The data from the AlphaGUARD continual radon monitoring instrument, placed in an enclosure of the KM8 site for periods April–July 2016, July–October 2016 and October 2016–January 2017 are plotted in Fig 8. The background of 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 3.

A graph showing the raw data obtained from the AlphaGUARD is shown in Figure 9. This shows the time series of the radon, without background correction. The data identified some isolated peaks in radon concentrations on certain days, usually during the night.

Period of monitoring

April16–July16 1–46 5 5 2.0
July16–October16 1–81 6 4 2.4
October16–January17 1–50 6 4 2.5


Contact BGS enquiries for further information.