Handbook of Radon.
4. Introduction to radon and indoor air quality.
The first point about radon is that although it is considered to be a serious indoor pollutant it is entirely natural and usually no-one's fault. This has tended to limit public concern, in sharp contrast to the anxiety generated over small risks in other areas involving ionising radiation.
Governments have been concerned for many decades with pollution of the outdoor air. Only a few decades ago, London smog killed hundreds of people before controls were introduced on both industrial and domestic emissions. Urban pollution is still a major problem in some parts of the world, and accounts for probably tens of thousands of deaths and a great deal of respiratory and other illness amongst all age groups. As western countries in particular have cleaned up the outdoor air (in cities if not more widely) they have also begun to embrace energy conservation, and buildings have been made more airtight.
There are two main reasons why Governments and Industry are now more concerned with 'indoor air quality'. First, many modern materials used in building construction and furnishing produce chemical pollutants. The second reason is that with modern scientific equipment, minute concentrations of pollutants can be measured with reasonable accuracy. Only when these facilities are available can either officials or politicians start to show concern, and to consider legislation and apportionment of blame.
Radon is not a new pollutant. It has always existed in buildings, and in the outdoor air. It was discovered as a radionuclide only in 1900, and was suspected of being a cause of ill-health in 1924. Only in 1951 were radon daughters (as opposed to radon gas) suspected of being a cause of lung cancer in miners.
Radon is a naturally occurring radioactive gas produced in minute quantities in most, if not all, soils and rocks. It is a product of the radioactive decay chain of naturally occurring uranium and has no taste, colour or smell. Nevertheless it is an interesting element: despite being a 'noble gas' it will form compounds and if cooled to a solid at the temperature of liquid air (-195 C) it glows with an orange-red light.
The parent radionuclide is radium, which has a half-life of 1622 years. Therefore, production of radon in the ground is essentially constant. In outdoor air, concentrations are extremely small in all parts of the UK, but higher concentrations occur inside buildings.
Houses in which the radon level is particularly high are a principal concern because many people spend most of their lives at home.
Most of the so-called 'high level houses' in the UK are in the south west, mainly the counties of Devon and Cornwall (see Section 9). Radon is a proven cause, or a proven contributory factor for lung cancer in miners. However, there is little convincing evidence for harm to householders, but this is being sought by way of epidemiological studies in many countries.
It seems likely that radon will be confirmed as a real risk in houses, but nevertheless it should be kept in perspective as a health issue (see Sections 23, 25, 31) and not taken automatically to represent a severe threat simply because it is connected with radiation.
Scientists are divided over whether small doses of radiation cause harm to people or not. Whatever the true position, there are many apparent anomalies, including that people who live in regions of higher than normal background radiation often have a lower overall cancer rate, and that in some experiments, irradiated animals lived longer than those that had not been irradiated.