One of Beijing's most prominent expats working in the technology sector is citing the city's poor air pollution as the main reason why he is quitting his job to return to the USA.

Hugo Barra publicly announced his resignation as the head of head of Xiaomi’s international unit on his Facebook page.

Calling it his "greatest and most challenging adventure of my life," Barra wrote about the success he acieved with Xiaomi and took the opportunity to thank CEO Lei Jun whom Barra referred to as "a mentor and a friend."

When explaining his reason for leaving Xiaomi, Barra wrote:

But what I've realized is that the last few years of living in such a singular environment have taken a huge toll on my life and started affecting my health.

Although Barra did not mention Beijing's notorious air pollution as the reason, Chinese news outlets like Sohu and iFanr have taken the hint and are reporting it as such.

Previously serving as Google’s Vice President of product management for Android, Barra made the switch to Xiaomi in 2013 where he soon became the Chinese tech company's highest ranking foreign executive.

Under Barra's direction, Xiaomi aggressively expanded into India where the company earned USD 1 billion in annual revenues last year, faster than any other company.

Barra's departure comes at a time when Xiaomi is struggling with poor sales.

Lei admitted on social media last year that Xiaomi tried to expand too quickly. After having gained a huge following with affordable cellphones, Xiaomi's expansion into home appliances have not been as well received. At the same time, shipments of Xiaomi's bread-and-butter smartphones fell by more than 30 percent last year to 11.4 million.

China's expat community has lost a number of key players over the years.

Last spring, Kaiser Kuo announced that he will be resigning as Baidu head of communications to return to the USA while other prominent Chinese expats that have also thrown in the towel include Charlie Custer and Mark Kitto.

And, they're not alone. In 2015, moving company Unigroup Relocation revealed that twice as many of its customers are deciding to leave China compared to those arriving.

Even though expat workers in China may receive favorable compensation packages, air pollution is something that will always be a problem for those deciding to work in China.

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Images: NetEase, Technobuffalo, iFanr