Radiation

Service outline:

Radiation occurs from two sources. Natural radiation exists due to materials present in the earth and particles arriving from outer space. Artificial radiation is caused by man made processes. There is no difference in the effects of the radiation regarding it's source.

An average person in the UK will receive approximately 10% of their annual dose of radiation from the suns cosmic rays, whilst another 50% is due to Radon (Rn) a gas generated from naturally occurring uranium present in the earth. Artificial radiation sources included medical treatments (approximately 15%) and fall out from nuclear tests and accidents (approximately 1%).

Radon is a naturally occurring radioactive gas which is formed by the decay of small amounts of uranium present in all rocks and soils. As a gas, Radon can move easily through the ground, particularly if it is porous or fissured to the surface.

In the open air Radon disperses rapidly and levels are low. However, in buildings, such as homes, Radon can be drawn in through cracks and gaps in the floor and can reach unacceptably high concentrations.

Radon decays to minute radioactive particles which can be breathed in. Some of these particles lodge in the lining of the lungs and irradiate the tissues, thus increasing the risk of lung cancer.

Following research undertaken by the National Radiological Protection Board (NRPB) in the late 1980s an "Action Level" of 200 becquerels per cubic metre of air (Bqm-3) was established in order to help limit the health risk. The becquerel is the unit in which radioactivity is measured.

If the annual average Radon concentration is at or above the Action Level, the NRPB advise that remedial action should be taken to reduce the Radon concentration in a property.

2. RADON AFFECTED AREAS

During the mid 1990s, the NRPB carried out an extensive national sampling programme for Radon, in order to establish the extent of the problem in England. The results of this survey were then used to help produce the Radon Atlas of England, published by the NRPB in 1996.

The Radon Atlas is a Radon probability map which divides the whole of England into 5km squares of the Ordnance Survey Grid. It identifies areas - known as Radon Affected Areas -where 1% or more of homes are estimated to be at or above the Action Level.

The Atlas shows that there are six Radon Affected Areas within the Ribble Valley affecting approximately 800 dwellings (see linked map ). It identifies that properties located within one of these areas maybe more at risk. This means that there is a low probability of between 1% and 3% or a slightly higher risk of between 3% and 10% that your property has an annual average Radon concentration exceeding the Action Level.

Whilst this information is obviously of concern, it must be emphasised that there are two additional categories included in the National Radon Atlas, these being 10 - 30% and > 30% of homes above the Action Level. No part of the Ribble Valley currently falls into either of the top two categories, although it should be noted that the NRPB are currently updating the Radon Atlas (as more information has been acquired since its initial publication).

ACTION TAKEN BY RIBBLE VALLEY BOROUGH COUNCIL WITHIN THE SIX RADON AFFECTED AREAS

(i) COUNCIL-OWNED DWELLINGS

At the beginning of 1999 Ribble Valley Borough Council carried out a survey of 17 of its own properties located within the Radon affected areas of our district. The results of the survey identified that FOUR of the properties measured had readings above the Action Level of 200Bqm-3, whilst another four had levels in excess of 100Bqm-3. The national average is 20Bqm-3.

Interestingly, there were large fluctuations in the results between adjoining properties and this can be caused by a number of factors such as building construction, living style of occupants etc. These significant local variations are a major problem when trying to identify exactly which properties may exceed the Action Level.

(ii) OTHER DWELLINGS

In 1999 letters were sent to all remaining housds (796) located within our Radon Affected Areas, giving residents the opportunity of having a Radon survey undertaken within their own property.Â households requested a Radon survey and the findings of this survey are summarised below:

RADON CONCENTRATION (Bqm-3)

50 = 18
50 - 100 = 9
100 - 150 = 3
150 - 200 = 0
200 = 2

These results indicate that two properties had high annual average Radon concentrations (the actual readings recorded were 240Bqm-3 and 260Bqm-3 respectively).

4. ADDITIONAL INFORMATION

The NRPB have produced a wide range of booklets on Radon. These can be obtained from NRPB, Chilton, Didcot, Oxon OX11 0RX, or via the NRPB Freephone No: 0800 614529. Alternatively, you can visit the NRPB website: Health Protection Agency