Picking Up After Your Pets

I've been walking dogs for going on five years now. I am an expert at knowing when my shoe/boot hits mud versus dog poop! Poop has a different feel to it entirely and of course stink! I hate when people don't pick up after their dogs. Maybe the excuse is it's biodegradeable...Do these people know that 30% of the e-coli found in our water systems (including our drinking water) is from pet waste. It's also considered a "bio-hazard" by the EPA...How to get that message out I'm not sure...Maybe bumper stickers that say... Be Kind Pick Up After Your Pets Behind