I do not know, but I would ask those that have the equipment, to see if the NOISE from plastic wad steel cartridges is lesser, or greater, than the noise from fibre wad lead cartridges. For if the latter this may have a socio-economic impact in that it may force many clay grounds to close down?
The noise is greater even with standard steel shot cartridges, this is recognised within the HSE document but dismissed as not being an issue. But we all know noise pollution can and has close clay grounds down.