While waiting at a stoplight on East Broadway in South Boston last week, Sheila Greene looked up at a billboard and was stunned. In white letters against a black background, a message read: “States that legalized marijuana had 25% fewer opioid-related deaths.’’

Greene was bothered by the fact that the advertisement — from Weedmaps, a California-based company that runs an online marijuana dispensary rating service and sells inventory software to pot shops — was placed in a neighborhood hard hit by opioid abuse. “I couldn’t believe it was being advertised,’’ she said.

So she contacted a representative of Clear Channel Outdoor — which owns the billboard structure — to point out that the message violated the company’s own policy regarding “exclusionary zones.’’ Clear Channel’s website states that “advertisements of all products illegal for sale to minors that are intended to be read from places of worship, primary and secondary schools or playgrounds’’ are prohibited in such zones. Greene estimated there are about 24 places of worship, schools, playgrounds, and after-school and summer programs less than a mile from the site of the billboard at 613-617 East Broadway.