Residents of Port Talbot have for months been complaining about a thick layer of black dust they believe is coming from the town’s steelworks.

It covers pets, children, cars, homes, carpets and furniture, locals say. But it had seemed that no one outside was paying attention – until last week.

Banksy, the street artist, visited the town in the early hours of Wednesday to paint his latest mural on two sides of a suburban garage. Now the garage has been cordoned off by barriers, while traffic wardens have been brought in to manage the crowds of Banksy fans flocking to see the new artwork. Plastic protective sheeting was due to be put up over the artwork yesterday, paid for with the help of Michael Sheen, the Welsh actor, who comes from the town.

One wall shows a young boy, next to a sledge and dressed for a snowy day, arms outstretched and mouth wide open. His tongue hangs out as he catches flakes falling from the sky. But turn a corner and the source is revealed to be less pure than the driven snow – it’s a fire in a rubbish bin, spewing smoke and ash.

In an Instagram video claiming responsibility, Banksy leaves no doubt as to the target of his commentary. A drone-mounted camera tracks up from the freshly painted mural to show, across the horizon, the dark chimneys of the town’s industrial works.

A Port Talbot local, Gary Owen, 55, says he contacted Banksy in August asking him to highlight the issue. Owen, a former steelworker himself, told WalesOnline: “I think it’s really good for the people of Port Talbot, that someone as world-renowned as Banksy would do that. I suggested it [be] more like seagulls with gas masks but, when I saw it, it does make you think. It’s thought-provoking.”

The owner of the garage, Ian Lewis, told BBC Wales: “I am very pleased, I think it is a smashing bit of artwork. It is good for the town and I just want to protect it … it is here for everybody.”