farmers used to spray oil on there dirt roads to keep dust down, what do you think a primary ingrediant is in asphalt. the environment can break down oil within reason. dumping a oil change down the drain is NOT realistic but i have never seen or heard of the oil from a running chainsaw causing a problem.
if it was a problem the EPA would be all over it.
Actually, last time I checked (a few yrs ago), the regulatory figures were indeed cracking down on non-vegi based bar/chain lubes. Point Reyes and Denali National Parks are the ones in N America that I recall banning petrol based bar/chain lubes and many if not most Euro nations banned it some years ago.
The thing about this whole argument that isn't well understood is the silent or undetected damage certain oils cause or "can" cause. Just because one hasn't developed cancer doesn't mean that he hasn't experienced other problems that could be traced back to his choice of oils. The same can be said for plants and all the little microbes that our eyes don't see.
We all have choices and one of those choices is to avoid, or at least make an effort to minimize, our exposure to compounds that are either known to be problematic or are thought to be whether we're talking personal health or that of the little creatures our naked eyes don't see. That isn't "environmentalism" or lipstick liberalism. It's just practicality.