In this regular column, Consultant Barry Hunt answers reader enquiries. If you have a question, email it to: [email protected] marked for Barry’s attention.

Q: I have been told granite worktops can give off radon gas. Is this true? And if it is, is it a problem?

I concluded last month’s column by mentioning the online publication of a two-part paper by independent scientists specifically covering the issue of radon gas emissions from stone. I said it had highlighted several interesting issues.

First, it should be stated that radon gas only has a half-life of just under four days, so a small release does not result in vast accumulations.

One expected result from the aforementioned independent scientists’ report was that sampling greatly affected the outcome, because of the natural variability and thus heterogeneity of stone.

There will always be locations exhibiting higher radioactivity, but in respect of total radon gas production the whole of the material present needs to be taken into consideration.

Gypsum, ceramic, brick, concrete and other building materials exhibit similar radon gas production rates to natural stone.

Therefore, when taking into account the volume of these materials within a dwelling compared with the volume of granite that may be present in a worktop installation, the contribution made to the total radon gas output by the granite is relatively minor.

There is no agreed safe limit for radon gas concentrations, which has created a focus for the doom and gloom merchants because the fact that all natural stone produces some level of radon gas cannot be denied.

However, this applies to all materials, not just stone, so should we ban everything?

The European Union has produced some guidance for minimising the risks of radon gas and so far the findings indicate that even when assuming a living space without ventilation that does not leak air, the amount of radon gas released by typical granite worktops is a fraction of the guidance value for background radon gas.

Where worktops had mesh and / or resinous backings that sealed one side, the other side produced an increased level of radon gas. This suggests a simple way of reducing the problem could be to use vapour impermeable surface sealers.

There is still a lot of work to be done on this issue of radon emissions, which is unlikely to go away. Hopefully, good science will win through, whatever the outcome.

Health & safety issues have to be taken seriously but our fears are easy to massage. It is always difficult to allay raised fears as many will always believe there has to be some degree of truth in any rumour. All I can say is that there have not been any known reports of ill-health linked to the use of granite and other rock types for kitchen worktops, nor indeed any other masonry use when considering radon gas or radioactivity.

My parting thought on this matter is that if a particular stone somewhere in the world was found to actually cause a problem, we would be immediately informed by some high authority. The problem would then be how we would know where such a stone had been used, especially given the stone industry’s penchant for renaming stones in order to protect their sources.

This would be another good reason for clarity in the naming and declaration of origin of stone placed on the market.

I very much hope this answers your question sufficiently and that your customers will now enjoy and cherish your granite worktops without fear.

References

Radiation protection 112. Radiological Protection Principles concerning the Natural Radioactivity of Building Materials. Directorate-General, Environment, Nuclear Safety and Civil Protection. Published by the European Commission, 1999. Guidance of a working party established under the terms of Article 31 of the Euratom Treaty.

Allen, JG, Minegishi, T, Myatt, TA, Stewart, JH, McCarthy, JF & Macintosh, DL. Assessing Exposure to granite countertops – part 1: Radiation. Journal of Exposure Science and Environmental Epidemiology (2009), 1-10.

Myatt, TA, Allen, JG, Minegishi, T, McCarthy, WB, Stewart, JH, Macintosh, DL & McCarthy, JF. Assessing Exposure to granite countertops – part 2: Radon. Journal of Exposure Science and Environmental Epidemiology (2009), 1-10.