You don't have to worry... Putting a Y-pipe on your bike won't single-handedly "kill the environment". There are plenty of diesel trucks, buses, and lorries worldwide wih no emission controls whatsoever to do that. Even if you rode your bike 24/7/365 from now until the end of your days your mounting a Y-pipe would have absolutely no effect on global warming, depleting the ozone layer, or causing cancer...
The exhaust will actually be far *COOLER*, as there will be no catalytic converter to trap and hold excessive heat. Catalytic converters, by design, have to trap a lot of exhaust heat in order for them to get up to the proper temperature for them to do their magic (breaking down NOX and unburned hydrocarbons, etc.). Because of this both the exhaust system and the exhaust gas exiting the system are at much higher temperatures than they would be if you were using a freer flowing system.
You will *NOT* burn yuor system cases (panniers), nor will you roast the left rear turn signal light...
How do I know?
Because I have replaced the catalytic converter and the stock muffler and my left rear turn signal and my system cases are just fine after thousands of miles of operation.
Also, you will find a large portion of the members here have replaced their stock exhaust systems with various aftermarket items, and none of them has cooked off a turn signal or system case...
Cheers!
Dallara