To tell you the truth, you would have to look through every last chemical that is in the additive/oil and all the components in that particular blend of gasoline. Would be very time consuming trying to verify all that info. From working in a refinery/refineries and being an Industrial firefighter/hazmat tech for more than 20 years, I can honestly tell you none of it is GOOD for you. Just the gasoline alone when you are filling up the fuel can..... Benzine is one of the worst chemicals that you can be exposed to, yet we do it all the time when filling up the car.... that sweet smell in the air is one of the worst carcinogens known. Our allowable time weighted average for exposure over an 8 hour work period usd to be 1 ppm ( Part per million). I think it has been changed to "0" now. Not good stuff.
The other one I see on here is people using leaded gasoline. I know its good stuff , but oh boy.... using that in an area with restricted ventilation for long periods of time.....It sounds corny, but I am actually concerned for the people using it - the amount of lead they are breathing in is a serious risk to their health.
In the end when it comes down to chemicals and acute and chronic health risks and potential for damage, dosage is the most important factor ( Mg/Kg) and then exposure over time. Some chemicals produce acute effects with no chronic issues, some no acute issues but with serious chronic potential ( Mutagens, carcinogens) like benzene.
The most practical way to reduce risk from the exhaust is through engineering controls ( Ventilation , isolation, wind at your back...L0l) or secondarily, PPE. I don't foresee any of you using a half face respirator when using a chainsaw. The gist of it is , think about what you are doing before you start and try to arrange how you are working when possible to reduce the amount of exposure to the exhaust while working with a chainsaw..... trying to isolate any one additive or chemical is pretty much a moot point.... all of the exhaust is harmful to your body in one shape or form. Take care of yourselves guys, your body will thank you. ( As a side not, I think on average refinery workers live ten years shorter than the average for all fields of work) We have had 7 fatalities in the refinery I work in since I have been there over 21 years. As a firefighter, seeing the after effects up close of what happens to your co-workers when things go really bad is an eye opener on the possible effects of working in an industrial environment. I try to protect myself from short and long term risks as much as possible on an everyday basis..... sometimes its just a little prethought that makes the difference, Mark.