I just came back from a long dog walk stuck on an out-of-nowhere question: How hard is it while driving along at, say, 35 miles per hour, to toss a 17-inch-square pizza box out your side window?

Clearly someone had done it – the soggy box stood out like a sore thumb in a litter-filled ditch alongside River Road here in otherwise bucolic Bar Mills.

But if texting while driving is dangerous, then what about littering large? And while texting at least has a purpose, what is the point behind wrestling a box out your window with your free hand when it would be much easier (and safer) to leave it on the floor or slip it behind the front seat until you get home?

My head-scratching reverie was actually prompted by good news: As of today in the city of Portland, polystyrene cups and takeout containers are verboten, done, illegal.

Simultaneously – and further proof to many rural Mainers that Portland is a socialist enclave shackled in political correctness – a 5-cent fee will forthwith be charged for every disposable plastic and paper shopping bag handed out by retailers throughout the city.

Naysayers aside, this is a big leap forward in keeping not only Maine’s largest city clean, but also adjacent Casco Bay. (Tip of the hat to Friends of Casco Bay for serving as the new ordinances’ catalyst.)

But it only addresses half the problem – the many and varied sources of the plastic and polystyrene that make up a big chunk of our 21st century stream of roadside trash. Still getting off the hook are the slobs who actually discard the stuff.

They’re everywhere. And never is their mindless disregard for their surroundings more apparent than mud season, when the snowbanks slowly recede to reveal all the dumping that’s gone on in the dark of winter.

The dogs and I have seen it all the past month or so, including four families’ worth of McDonald’s detritus down by Fountain Road. After walking past it two days in a row, I finally brought along two of those plastic shopping bags and filled them, until one started to split down the side.

“Do Mom and Dad hand out the burgers and shakes and chuck the rest?” I wondered. “Or do they just tell the kids, ‘Eat up and don’t forget to toss out your trash!’ ”

Then there are the drinkers: About 300 yards from their nearest point of purchase, the single-shot liquor bottles start sprouting by the dozens from the snow like so many plastic crocuses.

Right here in front of me I have an empty, pale-blue nip of Pinnacle Strawberry Shortcake Vodka – I plucked it from the sand to see if these things at least have a 5-cent deposit like other Maine beverage containers. They don’t.

The refuse list goes on: from an empty pack of Marlboro Lights (and, scattered for miles, every butt it once held) to Skoal Smokeless Tobacco, from scratched-out lottery tickets to discarded utility bills, from an old pillow down by the cemetery to a 2-foot piece of 2-inch PVC pipe about 100 yards farther up the road. Inexplicably, someone took the pipe the other day and carefully placed it atop the pillow.

Back in 2009, Keep America Beautiful undertook a study of not just the country’s current volume of litter, but also the behavior of the litterers. The 62-year-old nonprofit then compared its findings with those from a similar snapshot back in 1969.

It’s a mixed bag. Plastic litter was up a whopping 165 percent over the four-decade period, while the national tab for annual litter pickup and prevention is now pegged at $11.5 billion.

Overall, though, littering was actually down 61 percent over those 40 years. I attribute that in large part to those of us who grew up in the 1950s and 1960s and were fed a steady diet of print and television ads. They lambasted litter for the national scourge it was and exhorted us with that omnipresent jingle, “Please, please don’t be a litterbug, ’cause every litter bit hurts.”

It’s been years since the anti-litter movement had such mass-media status – some say the campaign withered in 1984 when then-New York Mayor Ed Koch launched a campaign to clean up the Big Apple by recasting “litterbugs” as “litterpigs” – the former moniker, Hizzoner explained, did not “truly convey the disgust I have for these people.”

No surprise then, according to Keep America Beautiful, that younger people who have never been taught otherwise “consistently … are more likely to litter” than we older folks and thus “present a clear market segment for focused messaging and campaigns.”

Or, rather than gently persuade litterbugs to change their ways, we could just start busting them.

Under Maine law, casting up to 15 pounds or 27 cubic feet of litter is a civil infraction punishable by a fine between $100 and $500. Get caught doing it from a car and the Secretary of State’s Office will add a penalty point to your driving record.

Like that actually happens?

“It might have,” mused Secretary of State Matthew Dunlap on Tuesday. “But it almost never makes its way to my desk. I get the rusty wheels that really squeak.”

That said, Dunlap was listening to the police radio in his car while driving home the other night when he heard a dispatcher relay a 911 call from an irate motorist who had just witnessed a major trash dump from the car ahead of him and wanted to report an environmental crime in progress.

“He had the license plate number, the vehicle description, everything,” Dunlap recalled. “That was probably the first time I’d ever heard that on the radio.”

So there’s hope.

Maybe Portland’s new ordinances, along with a polystyrene packaging ban and current consideration of a bag ban in Freeport, will rekindle our social conscience like those flaming rivers and mountains of roadside trash did a half century ago.

Maybe more corporations – Starbucks’ new reusable cup comes to mind – will wake up to the fact that environmentally friendly packaging helps their bottom line at the same time it’s protecting our ecosystem.

And maybe those of us who wouldn’t drop so much as a gum wrapper should start speaking up to the 17 percent of Americans who, according to Keep America Beautiful, can’t walk more than 12 paces without dropping their empty, 16-ounce foam coffee cup on the ground.

So let me be the first to sound off. To the greasy-fingered driver who threw out that pizza box on River Road in Bar Mills, did you know those things come in handy whenever you need to catch drippings from a paint can, or make a yard-sale sign, or patch the hole from a broken window (like I’m currently doing)?

Better yet, when you’re done – what’s the word, “repurposing?” – you can even toss those cardboard monstrosities into the nearest recycling container and back they’ll go into the pizza-supply chain.

Trust me, it’ll make you feel better.

It’ll make your – or at least my – neighborhood look better.

And no one will call you a litterpig.