If you have employees you have a legal responsibility to provide them with a workplace that is safe, non-discriminatory and free from harassment. This applies to both their physical and mental wellbeing.
If you are unsure about your responsibilities, check with your state Safe Work service or your state Small Business Ombudsman.
The Heads Up website provides an excellent summary of your obligations and rights as an employer with particular reference to the Disability Discrimination Act 1992 (Cth) and the Work Health and Safety Act 2011 (Cth). It is well worth a read.