Residents of Mongolia are drinking "oxygen cocktails" and "lung tea” to help protect themselves from air pollution.

Sold for as little as $1, adverts in Mongolia claim "drinking just one oxygen cocktail is equal to a three-hour-walk in a lush forest".

Yet, the World Health Organization (WHO) states there is no scientific evidence supporting such drinks' benefits.

Slum dwellers who are forced to use coal stoves to cook and heat their homes in the capital city of Ulaanbaatar, where temperatures can plummet to as low as -40C, are thought to be driving the problem.

According to Unicef, Ulaanbaatar is the most polluted capital city in the world, with an air pollution level 133 times higher than the safe limit set by the WHO.

Respiratory infections in the capital have nearly tripled, with pneumonia being the leading cause of death in under five-year-olds, data from Unicef shows.

For $2, shopping centres are selling cans of oxygen called "Life is Air" with the promise of turning an ordinary glass of juice into an "oxygen cocktail".

Many pharmacies also are stocking machines that turn juice frothy for as little as $1 and are recommended by doctors for pregnant women.

Some Mongolian residents are also turning to special teas in an effort to clean their lungs, with sales rising up to 30 percent when pollution peaks during winter.

Baatar Chantsaldulam, CEO of "lung-tea" company Dr Baatar, told AFP: “First it takes all the toxins out of the blood, then it turns the toxins in the lung into mucus, and all the plants in tea helps boost the human immune system."

Yet, Maria Neira, head of the WHO's public health department, said the only way to minimise the effects of pollution is to avoid exposure, adding there is no scientific evidence oxygen cocktails or lung teas have any benefit.

Angry residents claim the Mongolian government is not doing enough to combat air pollution, arguing the public should not have to pay $300 forat-homeairpurifiers.

TumurMandakhjargal, from the nonprofit organisation Parents Against Smog, said: "For the past 10 years, people have known that air pollution has reached dangerous levels.

"However, policymakers only address the issue by talking about passing out clean stoves and clean coal."