As someone has already said, the employer has a duty of care for his employees. As long as you do your best to look after their health, you can't do any more. This means getting your H&S policies down and signed by each employee, swapping roles during the day to try and avoid RSI's, training courses on how to lift/work at height, sun cream in the spring/summer etc etc.
A few guys on here used to employ and went back to working on their own cos of the hassle. Others do very well so I guess it's an organisational thing.