Indoor radon gas: A potential health hazard resulting from implementing energy-efficiency measures

Most members of the general public tend to regard their homes and the buildings in which they work as relatively safe havens from the physical and chemical stresses of the ambient environment. However, during recent decades a hazardous phenomenon concerning the built environment has become apparent: it can have a detrimental effect on occupants' health and has implications for energy usage. Radon gas is the culprit! It has no taste, smell or colour and its presence is therefore neither immediately apparent or readily detectable. Uranium and thorium, which occur naturally in rocks (e.g. granite) and soils, decay to form, among other elements, radon gas. This radioactive gas rises from the ground, enters the atmosphere and is then dispersed largely in the air so giving rise to low outdoor activity-concentrations, which are, at present, regarded as of little consequence for human health. However, radon gas can enter buildings, through cracks, gaps and joints in the ground floor, as well as from some of the building materials employed, such as granite. As a result, on numerous occasions relatively high indoor activity-concentrations ensue in some regions of the UK, notably Cornwall and Devon. All buildings, including dwellings, offices, schools and workplaces have been found to have radon gas accumulating in their interior environments and arising mainly from below ground level. An activity-concentration in excess of 200 Bq m-3 of air of radon is now acknowledged to be a health hazard to occupants within the affected building. Indoor radon gas has been cited as the second most frequent cause of lung cancer -- tobacco smoke being the most virulent -- with approximately 2500 premature deaths per annum in the UK being attributable to the ionising radiations transpiring from naturally-occurring radon. Indoor radon gas currently accounts for approximately half of the average UK population's exposure to ionising radiation, which is known to be responsible for carcinogenesis. The indoor radon problem has been exacerbated over recent decades due to the implementation of certain energy thrift measures, which have led to relatively airtight buildings and reduced ventilation air-exchange rates. Replacement of the air within buildings effectively reduces the concentrations of radon gas that would otherwise occur. Energy-thrift measures therefore can represent a health hazard for those occupying buildings which are prone to high indoor-radon activity-concentrations. However, research has shown that remedial actions to reduce indoor-radon concentrations can be effective economically and from an energy-efficiency viewpoint. The Government has reacted by implementing a comprehensive radon survey of UK homes. As a result, some regions of the UK have been designated as [`]radon-affected areas', where compulsorily-implemented precautions should be taken to ensure high indoor radon activity-concentrations will not occur in new homes: non-mandatory guidelines have also been issued with respect to existing buildings. However, despite the Government's extensive publicity campaign and surveys, relatively few of the existing homes identified as having indoor-radon activity-concentrations exceeding the action level of 200 Bq m-3 of air (i.e. equivalent to an annual dose of 10 mSv/year) have had remedial work carried out to reduce the presence of radon indoors. This disappointing response is due largely to (i) the Government's view that remedial actions are the responsibility of the householder and (ii) the public's apathy towards the problem. The Government, quite reasonably, sees its pertinent obligation as making the public aware of the problem and giving advice about remedial actions. Nevertheless this present investigation recommends a reallocation of resources to facilitate overcoming this problem and a change in the Government's approach, so enabling more householders to carry out remedial actions quickly. Countries world-wide are affected adversely to some extent by indoor radon gas; the problem receiving particular attention in Sweden, Canada, Germany and the USA. However, the present survey considers the indoor-radon problem from a UK perspective.