That tinge of strange smoke once smelled mostly in the high seats at rock shows has become commonplace in parts of America where voters have legalized marijuana.

A Washington Post survey found that in some city wards nearly 70 percent of people smell marijuana smoke at least once a month during their perambulations and 1 in 3 people smell it every day, just a year after the city legalized it for recreational use and personal possession, though not sales. “People aren’t as discreet as they were before it was legal,” a 21-year-old D.C. resident named Wuan Smith told the Post.

Indeed, America’s growing experiment with legalized recreational pot has literally changed the atmosphere around a drug that has for decades been one of the top reasons for arrests in the US.

With pot out of the shadows in some states, the direct exposure to smoke has led to conflicts. Colorado, which in 2012 was the first state to legalize recreational marijuana, has seen odor complaints rise, with 30 percent of such complaints now regarding pot in Denver.

But research also shows the smell of smoke and budding marijuana flowers hasn’t negatively impacted support for legal marijuana among Americans.

Support for marijuana has grown among African-American residents in D.C. by 23 percentage points, to 60 percent, since 2010. Part of that support may be explained by the fact that African-Americans, research has shown, have been disproportionately affected by marijuana prohibition laws, even though more white people partake. The upshot is that marijuana arrests plummeted, with only seven people being arrested this year in D.C. for pot, compared to over 1,200 such arrests in 2013. (Pot possession is legal in D.C., but sales are not.)

Four states and D.C. have legalized pot for recreational use, and more states are considering legalization. But concerns about children getting access and their exposure to second-hand smoke as well as other the societal effects of marijuana still run deep in some parts of the country. Such concerns among older and more conservative voters played a role in Ohio nixing a marijuana referendum earlier this month, by a solid margin.

Many critics predicted a rise in public intoxication, buzzed driving and crime after Colorado legalized pot, and concerns about children's exposure to the drug. But one of the biggest complaints so far has been odor issues as grow operations expand. When pot was illegal, those operations often took measures to contain the smell, including carbon-filtering the air. With the threat of prosecution gone, some cultivators are no longer worried.

That can cause problems. High Valley Farms in Pitkin County has been the focus of a county commission probe as neighbors complain about a skunky aroma floating out of the facility.

“Six months ago our neighborhood smelled like a neighborhood, and now it smells like someone is holding up a package of marijuana to your face.,” neighbor Bart Axelman told the Denver Post.

But even Mr. Axelman conceded that, despite his complaint, he’s “in no way opposed” to the state’s burgeoning marijuana business.

Denver code enforcement officer Ben Siller uses a device called a “Nasal Ranger” to sniff out potential illegal emanators. As part of its law, Denver bans any smells that exceed 1 part odor to 7 parts filtered air, or if at least five people complain. Under those rules, however, no one has been cited for excessive odor so far in the Mile High City.

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Mr. Siller said he expects complaints to subside as legal marijuana becomes rote.

“You do have people who just object to the whole idea,” Mr. Siller, Denver’s code enforcement officer, told USA Today. “[The smell] is discernible. It’s there but you get used to it, just like any odor.”