Variability of indoor radon concentration in UK homes.

This study investigated the variability of indoor radon concentrations in 518 100 homes in the UK. The statistical analysis included measurements in 395 720 homes with downstairs living rooms and upstairs bedrooms. The radon concentration in these bedrooms was found to be on average 63% of the living room value. The analysis of 122 380 homes with living rooms and bedrooms situated on the same floor found that there is a small difference in radon concentration of 9% between the two rooms. The results showed that the ratios of the living room to bedroom radon concentrations were approximately lognormally distributed. The geometric mean of the ratio was found to be 1.6 for rooms situated on different storeys and 1.1 for rooms situated on the same floor. It was found that house characteristics and energy efficiency measures affect the distribution of radon within homes. Detached houses and those with suspended floors had higher radon levels in their upstairs bedroom, 66.7% and 76.9% of the downstairs living room values, respectively. For homes built between 1993 and 2007, the bedroom to living room ratio increased from 58.8% to 76.9% due to the increased airtightness and improved energy performance of the modern buildings. Homes with installed wall and loft insulation had much higher bedroom to living room ratio (76.9%) than those without energy efficiency measures (52.6%).

RADON BASELINE MONITORING AROUND A POTENTIAL SHALE GAS DEVELOPMENT SITE IN YORKSHIRE, ENGLAND.

The Vale of Pickering in Yorkshire, England has been identified as a potential area for shale gas extraction. Public Health England joined a collaboration led by the British Geological Survey for environmental baseline monitoring near the potential shale gas extraction site following a grant award from UK Government Department for Business, Energy and Industrial Strategy. The analysis of results for the first 6 months of indoor monitoring indicated that the results followed a log-normal distribution. The numbers of homes found to be at or above the Action Level followed the numbers predicted by the radon potential maps. The results from the measurements of outdoor air in this study indicated that the radon concentrations are slightly higher than previously measured but close to the detection limit of the technique.

New Correction Factors Based on Seasonal Variability of Outdoor Temperature for Estimating Annual Radon Concentrations in UK.

Indoor radon concentrations generally vary with season. Radon gas enters buildings from beneath due to a small air pressure difference between the inside of a house and outdoors. This underpressure which draws soil gas including radon into the house depends on the difference between the indoor and outdoor temperatures. The variation in a typical house in UK showed that the mean indoor radon concentration reaches a maximum in January and a minimum in July. Sine functions were used to model the indoor radon data and monthly average outdoor temperatures, covering the period between 2005 and 2014. The analysis showed a strong negative correlation between the modelled indoor radon data and outdoor temperature. This correlation was used to calculate new correction factors that could be used for estimation of annual radon concentration in UK homes. The comparison between the results obtained with the new correction factors and the previously published correction factors showed that the new correction factors perform consistently better on the selected data sets.

Radon, the lognormal distribution and deviation from it.

It has been recognised for many years that the distributions of indoor radon concentrations in many countries conform more or less closely to a lognormal distribution. For homes situated over a single geological unit with a consistent source of radon in the ground, conformance with the lognormal distribution can be understood in terms of the multiplicative factors affecting the relationship between radium in the ground and radon in indoor air. The fact that national as well as local distributions of indoor radon also usually conform to the lognormal can be attributed to the fact that the mixture of a number of different lognormal distributions will often result in a lognormal distribution. In some cases, however, the national distributions of indoor radon deviate from a lognormal distribution: the reasons for this are examined using model normal distributions. A study of the deviation of the UK distribution from log-normality above 500 Bq m(-3) provides a better estimate of the number of homes with very high radon concentrations.