Further to the letter (The Argus, August 24) about fracking chemicals, the only chemicals approved for use in the UK so far are as follows: Polyacrimide,which reduces water friction (commonly found in cosmetics and face creams); hydrochloric acid to prevent bacteria build-up in the water (commonly used to keep swimming pools clean); and occasionally a biocide if the water is taken from rivers and needs to be cleaned, as opposed to tap water from utilites.

So far Cuadrilla have only used polyacrimide in the UK .

Thanks to James Verdon, a geophysicist at Bristol University, for supplying this information to me.

M Thomason, Jobes, Balcombe