Window cleaners make about $25 a day. The maximum they can earn in a day is $1000, according to Wikimedia.

However, the job comes with a number of risks, like slipping on water or soap, and falling from heights. Window cleaning is considered the most dangerous job in the UK.

The cleaners have to obtain a license for high-rise operations and must not have high blood pressure or naturally suffer a fear of heights.

They are not allowed items which could fall, such as cell phones or wristwatches, and must stop working when it is too windy.

Take a look at the tough lives of these window cleaners...

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Migrant labourers wash a roof near The Bund on the banks of the Huangpu River in Shanghai.

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People watch as a window cleaner works outside the 14th floor at the Shard in London.

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Window washers work on a building near a ferris wheel in Tokyo's Odaiba entertainment and shopping district.

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Workers clean windows at a building in downtown Buenos Aires.

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A worker cleans the windows of an office building in Tokyo.

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Cleaners watch an Air China plane land as they sit atop the roof of the Beijing Capital International Airport's train station.

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A worker cleans the windows of an apartment block on a haze day in central Beijing.

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Cleaners prepare for window cleaning outside the 101st floor of the Shanghai World Financial Center.

More than 30 workers on the window-cleaning team of the skyscraper work in pairs every day.

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A worker cleans the windows of an apartment block in central Beijing.

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Workers clean the exterior of the 'Sun Valley' at the World Expo site in Shanghai.

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A cleaner abseils down the side of a newly renovated building in central Beijing.

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A window cleaner dressed as Santa Claus poses for photographers during an event to celebrate the upcoming Christmas holiday season at a shopping mall in Tokyo.

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Window cleaners work at an office building at Berlin's Kurfuerstendamm shopping mall.

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A worker cleans a window of an office building in Tokyo. 

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Workers clean the windows of a newly built office building in Taiyuan, Shanxi province.

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A worker cleans the windows of a hotel building in downtown Sofia.    

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A cleaner washes the glass windows of a building in Brasilia.

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A worker cleans the windows of a hotel in central Mexico City.  

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Workers clean the windows of a building in Quito.

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Window cleaners stand on a platform hanging from the front of the CCTV (China Central Television) building on a sunny day in central Beijing.

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Employees clean the windows of the main building of the European Parliament in Strasbourg.

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Sailors clean windows for the watchstanders inside the Flag Bridge of the Nimitz-class aircraft carrier USS Abraham Lincoln (CVN 72) looking for surface and air contacts during a transit through the Strait of Hormuz.

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A cleaner washes the window of the athletes' hotel in Istanbul. Athletes from around the globe are in Turkey ahead of the World Indoor Athletics Championships on Friday. 

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A worker cleans the window of an office building in Taiyuan, Shanxi province.