Health and safety law ?

In the fertilisers company, workers are under instructions to stop the mixers before adding each ingredient. To add ingredients there is a small panel in the vat which is open and the chemicals are poured in from container which have the correct amount in them. but now the workers have been placed on special bonus scheme to try to improve productivity and as a result number of bad working practices are followed. for example it is become common for mix to be added without switching off the mixture. Andy, one of the mixers has severe eye problems due to adding an ingredient to a mix without switching off the mixer. Advice the company management for their legal liability.