Home radon levels and seasonal correction factors for the Isle of Man

Abstract

Ionizing radiation dose levels due to home radon can rise to levels that would be illegal for workers in the nuclear industry. It is well known that radon levels within homes and from home to home, and also from month to month, vary considerably. To define an Isle of Man radon seasonal correction factor, readings were taken in eight homes over a 12 month period. An average island indoor exposure of 48 Bq m(-3) (range 4-518 Bq m(-3)) was determined from 285 homes selected from a cohort of 1300 families participating in the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) in the Isle of Man. This compares with a UK home average of 20 Bq m(-3) and a European Union average (excluding UK) of 68 Bq m(-3). Ten homes of those measured were found to have radon levels above the National Radiological Protection Board 200 Bq m(-3) action level. There are 29,377 homes on the Isle of Man, suggesting that there could be some 900 or more homes above the action level. No statistical difference was found between the NRPB and Isle of Man seasonal correction factors.

The effects of geology and the impact of seasonal correction factors on indoor radon levels: a case study approach

“…The underlying geology of this region differs to that of many other parts of the UK, large areas being immediately underlain by large granite bodies. Grainger et al (2000) suggested that as the UK seasonal correction factors had been derived from the mainland UK database, which is dependent on UK geology, seasonal correction factors may need to be different for the Isle of Man, which has a very different geology in many ways. Grainger et al (2000) measured radon levels following NRPB protocols in homes of over 400 families for a period of 3 months in the winter.…”

“…Grainger et al (2000) suggested that as the UK seasonal correction factors had been derived from the mainland UK database, which is dependent on UK geology, seasonal correction factors may need to be different for the Isle of Man, which has a very different geology in many ways. Grainger et al (2000) measured radon levels following NRPB protocols in homes of over 400 families for a period of 3 months in the winter. They also measured seasonal variation for 12 months in 10 homes and, from this, a seasonal correction factor was derived by dividing the arithmetic mean for each time period by the annual arithmetic mean.…”

“…This study confirmed previous patterns observed in the UK of lower radon concentrations in the summer months due to ventilation effects. Using the ManneWhitney test, Grainger et al (2000) suggested that the difference between the Isle of Man and UK median radon values was not significant. They did derive different seasonal correction factors to those used in the UK but suggested that, despite this outcome, the difference between the two seasonal correction factors was not statistically significant.…”

“…The Grainger et al (2000) study used only 10 homes for its seasonal data. Two of the 10 homes could not be used to determine seasonal correction as the detectors had not been used according to NRPB protocols, as the authors point out themselves.…”

“…This is therefore a very small database. Like many such studies, Grainger et al (2000) also did not take into account the enormous variability that any one geological formation will have in uranium/radium content. Gates and Gundersen (1992b) suggest that the rate of radon flow is very dependent on small-scale geological features.…”