I don't think that's how it all quite works ANCPER.
Everything is risk assessed and nothing is 'no risk'. There's always a chance of something happening, however remotely small even with safeguards in place. The workplaces of today with a decent OH&S system in place will attempt to get any activity in the very low/low range. Anything higher and further safeguards are required to reduce the risk. If the companies of today were legislated to provide risk free environments, we wouldn't have a job - it is affordable safety.
There is a very good chance the crap we breathe doing walkarounds behind an engine, or the oils we get all over ourselves, the sealants we smooth over with our fingers, the skydrol we have all over the hydraulic lines spewing out under pressure and all over the place, etc, do have an adverse effect on our health.
However, pinpointing any of them to any ailment when our normal outside of work environment is full of unnatural pollution which has been shown to cause illness over decades of exposure is going to be near on impossible. If people were dropping dead a week after a smoke/fumes event, different story, but the numbers don't stack up.
The doctor advised that this type of Leukemia is caused by radiation and/or Benzine (a product found in oils and fuels)!!! Makes you wonder ??
Like unleaded fuel..