I have to look at a tiling job being carried out in a Leisure Centre(swimming pool area) The tilers have to remove the grout with the use of powered tool(dusty job), then re-grout all areas What are the health and safety issues?(example dust, ergonomics, COSHH, manual handling, work at height) Is the grout dust explosive?

Can't they remove the grout with the water still in the swimming pool....no dust problem! Vibration may be an issue perhaps?

You could look at them using water feed power tools to keep the dust down which do work well. I can remember being tasked with a job like the one you are looking at nightmare! Plenty of rest breaks because it becomes back breaking work and very boring to which you lose concentration on the task in hand over very large areas.