Ceramic wall tiles are non-combustible and are not generally regarded as hazardous or toxic materials. Like all building materials, reasonable care has to be taken when handling (e.g. cut edges can be sharp when installing or removing.) Health and safety requirements are usually more relevant to the safe use and handling of tile adhesives and grout (for example avoiding long contact with skin or eyes).
Wall tiles tend to need less comprehensive cleaning guidelines than floor tiles and we would normally recommend that after the initial clean off of wall grout residue to a satisfactory standard, the tiles should be periodically or as necessary washed down with a neutral type of detergent solution to remove any build-up of grease or grime.
Should a build-up of lime scale develop on wall tiles e.g. shower walls in hard water areas, then this can easily be removed by using H.G Lime Scale Remover, closely following the dilution rates and instructions shown on the bottle.