I think EPA laws make it much harder to have a place like that, due to potential leakage of oil/gas/etc.
Mmm...you'd be surprised at how clean some of these places can be. A lot of the yards I've been to in PA were actually quite a bit ahead of their time with regard to hazmat collection for junkers. Many of those guys don't want to work around puddles of spilled gas and other caustic fluids, especially if the owners are smokers!
Antifreeze spills are also not terribly condusive to keeping around guard dogs at night.
No, most yards are pretty clean. The less reputable ones may be a problem, but I never go to those more than once if I get a bad vibe from the employees and/or surroundings.
Now the impact that you DO directly get from the EPA on places like these are federal tax credits for early recycling of junked vehicles back into the system, for steel, plastic, rubber and other car-making raw materials. I heard that story several times from my mechanic and yard owners that I used to frequent. I couldn't figure out why it was getting so difficult to find parts for my 10yo+ vehicles, when back in the 80's or 90's, I could still find 20-30 year-old vehicles in the rows. Many yards now find it more lucrative to quickly recycle their cars than it is to keep them around for 5-10 years for potential customers that may or may not show up for them. That's why I've gone strictly eBay when it comes to finding parts.