In this regular column, Consultant Barry Hunt answers reader enquiries. If you have a question, email it to: nss@qmj.co.uk marked for Barry’s attention.
I have a customer who wants a stone floor in his surgery but is worried about possible blood spillage. Can you get blood out of stone?
Blood is made up of 45% cells and 55% plasma. It has a mildly alkaline pH. This simplistic view is overshadowed by the fact that potentially up to 40,000 different proteins are believed to enter the blood along with inorganic salts and organic substances. The cells are present in the following approximate ratio of 600:40:1 for red, platelets and white respectively. About 90% of the plasma is water.
There is actually little in blood that would appear to be a threat to any stone. The threat is further reduced by the fact that most blood spills are treated by The Health & Social Care Act 2008 as potentially hazardous and thus must be cleaned up as soon as possible. Thus the focus shifts to the materials used to clean up and sterilise such spills.
The NHS recommendations for cleaning up blood spills provide a range of methods to deal with different situations from minor blood spatter to major spills. However, the active agents are essentially the same and clean-up and sterilisation rely upon the release of chlorine, which is strongly oxidising.
Two chemicals commonly used are sodium hypochlorite, which is often found in toilet bleaches and other strong cleaners, and sodium dichloroisocyanurate, which seems to be the preferred choice because it is less affected by organic compounds and not so aggressive to metallic and other surfaces. Sodium hypochlorite is alkaline while sodium dichloroisocyanurate is acidic, so each has the potential to attack different components of stones.
The key with using these and other similar products is a combination of speed, minimal safe application, and finally neutralising the cleaned area of any chemical residues.
But what properties of stone would assist in minimising the potential for problems? And what else might be done to further reduce this potential?
Because of the chlorine-based chemicals, the advice is essentially the same as that given for stone used in swimming pool environments, which will be covered in a forthcoming Stone Federation technical advice document.
The main issue relating to a surgery floor, as it is with any floor liable to staining, would be to minimise the potential absorbency of the stone so that no viruses or pathogens in the blood are left in the stone. Therefore, porous sandstones and limestones, and travertines that require filling, would not be recommended for a surgery. Interlocking crystalline materials exhibiting very low absorption are more appropriate, as are smoother finishes that do not trap dirt. Joints should be flush and not recessed.
The stone would benefit from an impregnating treatment to further reduce the potential for infiltration of both blood and cleaning products. However, the treatment would need to be resistant to the cleaning chemicals.
Some silicone-based treatments are reported to be unaffected by chlorine but there is no overall opinion as to whether and then how surface-applied natural stone treatments can be employed. Potentially only resin-based impregnators might be successfully applied to natural stone in order to provide the best overall resistance.
Therefore, in answer to your question, there are many stones that could be successfully used in locations where blood might be spilled, providing the risks are minimised by good selection and maintenance.