In my experience (as an ambulance paramedic for many years), the one single hazard that causes more deaths is ......... alcohol!

Actually, it is not the sole cause, but is a contributing factor in many many deaths when mixed with a variety of other factors (although it can be a cause of death in and of itself). Alcohol and cars, bad. Alcohol and guns, bad. Alcohol and other drugs, bad. Alcohol and boats, bad. Alcohol and BBQ grills, bad. Alcohol and additional alcohol, bad. Alcohol and roofs, bad. Alcohol and severe cold weather outside, bad. Alcohol and stairs, bad. Alcohol and stupid males doing a variety of stupid male things, bad.