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Radon and Health in the Natural and Built Environment

Tidal Synchronicity: short term radon variation (and its impact on time average levels) and anomalies associated with Earthquakes.

Although long-term (1 year) average radon levels in domestic sites determine the overall lung cancer risk to occupants, for a variety of reasons it is generally preferable to make radon determinations using shorter-term (a week to 3 months) methods. In a recent DEFRA study (ref.) short-term exposures were explored as measures of long-term trends. The time-dependence of radon levels at a number of sites in the U.K. and elsewhere, were monitored at hourly intervals over extended periods using real-time RAD-7 monitors. Regression and cross-correlation of radon levels with environmental parameters showed weak contributions to variability from mean temperature and rainfall, while autocorrelation and Fourier transformation identified a number of characteristically periodic features. Daily, weekly and monthly contributions, some common to more than one site, others location-specific, were identified, with differing strengths reflecting local occupation patterns. Two sites exhibited components having periodicity of 23.9hours (the luni-solar diurnal period) and 24.0hours (the solar day), while one gave indication of a 168hour (one week) cycle. In addition, evidence appeared of periodicity around 661hours (27days13hours), the Lunar Month. This together with a positive correlation with tidal strength, suggests that 'Earth Tides' and Ocean Tidal Loading contribute to the periodic liberation of radon, possibly via geophysically driven variations in ground-water level.

The two hourly-sampling radon detectors were operated simultaneously in separate locations 2.25km apart for a 25-week period. This period of operation encompassed the period in September 2002 during which the Dudley earthquake (magnitude-5.0) and smaller aftershocks occurred in the English West Midlands , UK . Analysis of the radon time-series reveals a short period when the two time-series displayed simultaneous in-phase short-term (6-9 hour) radon anomalies prior to the main Dudley earthquake.

This research into indoor domestic radon concentrations has led to the discovery of radon anomalies prior to the main Dudley earthquake (Crockett et al., 2006a). These were not merely radon spikes but a time-series that produced simultaneous in-phase radon, short-term anomalies, in 2 real time detectors, before the quake. This development in understanding opens up the possibility of being able to detect such signals in advance of an earthquake, at least on geology similar to the region of the UK examined.

This research work has led to the realisation that radon levels vary because of tidal impact (Synchronicity) and that simultaneous in-phase signals, of radon, have appeared before an earthquake in England . This has implications for short-term testing, as synchronicity will have an impact on assessing longer-term radon averages and could necessitate the application of suitable protocols. Tides will have an impact upon radon levels in the UK particularly in those regions where the loading is the greatest (West Coast).

Data analysis of earthquake catalogues worldwide suggests that there is a correlation between tidal impact (Synchronicity) and the Sumatran Earthquake and its aftershocks (26th December 2004; Crockett et al., 2006b). Our initial analysis of data sets for the Sumatran earthquake suggests a link with a significant proportion of quakes correlated to the time of full and new moons.

Executive Summary

Researchers

Funding Body/Source

  • AHRB
  • EU
  • DEFRA
  • The Radon Council

Duration

2000 - ongoing

Project Summary

This research is concerned with radon and health issues in the natural and built environment. A particular focus is on radon in caves and abandoned mines, as well as tidal synchronicity of indoor radon (and associated earthquake activity) together with the link between radon and geology.