But the artist behind the Docklands piece said a newly-released video showing the making of the mural portrays the artwork's message better than the mural itself.

As well as being the world's coldest capital city, with temperatures as low as minus 40 degrees Celsius, Ulaanbaatar in Mongolia is among the most polluted cities in the world.

Melbourne-based artist Khosnaran Kurelbaatar, aka Heesco, moved to Australia from Mongolia in 1999 and still has friends and family in Ulaanbaatar.

"I go visit, if not every year, then every second year," he said, adding that he has watched the city's air pollution problem "growing spontaneously".

"I have so many family members there, and seeing what they go through started really affecting me.

"It's pretty much a humanitarian disaster."

Heesco said using art to draw attention to the issue was "better than doing nothing".

"As a mural artist I do have a small amount of viewers, of followers, that I can reach," he said.

Working with organisation Breathe Mongolia, Heesco arranged for a photographer to shoot images showing the pollution on the streets of Ulaanbaatar.

He used two of those photos, both showing children wearing facemasks, as the basis for his mural.

Local videographers then filmed Heesco as he painted the work.

"I wanted to start off painting a really clear blue sky — Mongolia was once known as the land of blue sky," Heesco said.

He then painted the buildings and people before spraying lightly over the artwork with grey paint to portray the city's smog.

"In the video process you will be able to see from the beginning to the end, which I think works better."

Heesco said he hoped the mural and video would help inform the public about Mongolia's smog problem and draw the attention "of whoever is willing to contribute" to solving it.

"Mongolia needs sustainable solutions to this problem," he said.

He said places like Melbourne have the research facilities and funding required to come up with those solutions, but those researchers had to first be aware there was a problem to solve.

"People won't know unless we do something and talk about it," he said.

"Hopefully this will bring some attention to it."