They are lubricating a chainsaw blade. They aren't drinking it or putting any on their body's.
Thats exactly what happens.
A test was done years ago which had dye in the oil to see what happens when in operation.
An ultra violet light was used to see what was happening.
When the chain moves on the guidebar, the oil turns into a fine mist that you cant see but the light did.
This mist is all around you not just near the saw. So basically you are breathing in polluted air.
Its better for you smoking 100 cigarettes than breathing in used engine oil which causes cancer.
Bio oil is not only better for the enviroment but better for your body.