The pollution levels in the air tenants breathe is the latest check landlords must carry out on a buy to let home.

From next year, landlords must include details of high pollution levels on letting particulars for tenants to read before signing up to move in a property.

The check is part of ‘material information’ National Trading Standards want landlords to tell tenants before they move into a home.

How landlords will discover pollution levels at their rental properties is unclear.

Some data is available for London boroughs from the charity web site, but outside the capital, pollution data is scant.

James Munro, of National Trading Standards, said: “Pollution mapping is more widely available, and the facility is there to search by postcode how badly a property is affected, we’re saying that this is material information. This is something people should know if they’re buying a house especially if they have children or elderly family members moving into the property.

“If it’s a low rating, it could be a good marketing tool, but if it’s a high rating — of which there are quite a few hotspots in London — people need to know.”

The Royal College of Physicians says polluted air kills 40,000 people a year in the UK and costs healthcare services and businesses £20 billion.

The check will monitor nitrogen oxide levels in a neighbourhood.

The latest official data revealed 83% of reporting areas have pollution levels over the legal minimum.

Some of the worst polluted areas in London also have the most expensive homes.

Kensington & Chelsea, where homes can change hands for £2.5 million and command rents of £7,000 a month and plush Westminster are both among the boroughs in the capital with the worst pollutant levels.