Hazardous products can be harmful to your health if you do not limit your exposure to them. As you handle these materials, you’ll need to know whether they are health hazards or physical hazards.
GHS also defines an Environmental hazards group. This group (and its classes) has not been adopted in WHMIS 2015. However, you may see the environmental classes listed on labels and SDSs. Including information about environmental hazards is allowed by WHMIS 2015.