No. That's a really good point you raise. The Association of Workers' Compensation Boards across Canada, which collects the most reliable data that covers most, but not all, workplace accidents and fatalities, measures on a number of collection criteria but they don't collect the data on alcohol or drug-related fatalities.
In Ontario, the chief coroner has a policy—it's not legislation or regulation but a policy—that every time a worker dies at work, the worker is tested for drugs or alcohol. That's how we often know what the substance is; otherwise the employers or the public never know.