Elisabeth Anderson, a Swede who works in Beijing, said a Swedish friend of hers just left Beijing because of the air quality.

Anderson said her friend had spent most of her time working in Beijing during her 10-year stay in China.

"She has contracted a lung disease, so she is worried that a longer stay will make the illness worse," she said.

Rhio Zablam, from the Philippines, works at a media firm in Beijing. He married a Chinese woman in 2011, and they had a baby in February.

"My wife and I are worried about the air pollution in Beijing because it might be harmful to the growth of my baby," the 34-year-old said. "Although the smog does not occur every day, I have not yet brought my baby out of the house till now."

Zablam said he plans to buy an air purifier as many of his European friends in Beijing have done.

Zablam said he hopes the government takes concrete measures to clean up the air.

"Our foreign colleagues have concerns about Beijing's air quality when they are asked to make a business travel to the capital," an employee of headhunter Adecco Description's Shanghai office said, speaking on condition of anonymity.

"Shanghai is definitely my favorite Chinese city," said William Hatcher, who has been living and working in the metropolis for about two years, after living in Changsha, Hunan province, for two years. Hatcher said the difference between the two cities is like "day and night".

Hatcher, a 25-year-old English-language teacher from the United States, said the best part of Shanghai is the variety of food, culture, people and places to go, while the disadvantage is dealing with the bureaucracy when applying for things like visa renewals.

"It's tolerable, but can be frustrating," Hatcher said.

He said he is not worried about the environment problems, adding: "After all, they are not as bad as in Beijing."

But for James Eron, a US citizen and father of two girls, air pollution and food safety have been the biggest worries related to his girls' health. And his solution is having air purifiers in his house and trying to eat organic food and at well-known places.

What appeals most to the 43-year-old entrepreneur, who now owns a cloud computing and server operations company in Shanghai, is the "multiculture" of Shanghai, which has people from different places.

The survey by International Talent magazine also found that among the 1,050 foreign professionals surveyed, 30 percent plan to settle down in China, and most of them are 35 years old or older who have families with them in the country. They prefer to live in cities such as Chengdu and Hangzhou, where they can enjoy better living environments.

Expats also expect more simplified visa procedures and easier access to China's green cards, the survey found.

Hou Liqiang contributed to this story.