There are two hazard groups in WHMIS 2015: the Physical hazards group and the Health hazards group.

Quick Scoop: WHMIS 2015 Hazard Groups

If you zoom out to the highest level of the WHMIS 2015 classification system, all hazardous products are first divided into just two broad groups:

  1. Physical hazards – based on physical or chemical properties, such as flammability, reactivity, compressed gases, or corrosive effects on metals.
  1. Health hazards – based on the product’s ability to cause adverse health effects such as acute toxicity, sensitization, cancer, or organ damage.

Within these two hazard groups, WHMIS 2015 then breaks things down further into hazard classes and categories (and sometimes subcategories), but the top‑level answer to “how many hazard groups are there in WHMIS 2015?” is still two.

You might also see references to an “environmental hazards” group in GHS, but this group is not officially adopted as a WHMIS 2015 hazard group in Canada , though environmental information can be added voluntarily to labels or safety data sheets.

TL;DR: WHMIS 2015 uses 2 hazard groups (Physical and Health).