There's certainly the other things you could be doing with the
land. But let's assume you examined that and decided a lawn was really the best way to go...
It sounds like you already have a bit of an understanding of some of the environmental impacts of your choice: the sod had to travel farther than the seed, it might have been raised with careless water usage, heavy nitrogen fertilizer, etc.
But like with many other things that are grown, the environmental impact is really a function of the farm that you bought it from. I'm familiar with plenty of eco-friendly sod farms in the Pac Northwest that use thoughtful water techniques, and keep their soil rich naturally. My recommendation (unless you've sodded already) is to research where your sod is coming from, and use the most
local, eco-friendly place you can.
Other than that, make sure that your soil is well-prepared to receive the sod. It needs to be in as good of condition as if you were seeding - else your sod won't take
root! And you don't want to waste a batch of sod since it's tugging at your conscience.
Best of luck with your new lawn!