"It's not a way to live, to keep your baby inside with an air filter running," she said.

As bad air chokes Chinese cities, some expatriate employees are starting to leave families in their home countries, the latest sign of pollution's rising cost to the more than half a million foreigners working in China and the multinationals seeking to retain them. Smog in Beijing was worse than government standards most days last year, and environment ministry statistics show that 71 of 74 Chinese cities failed to meet air-quality standards.

"We are seeing some companies reverting to 1980s and 1990s hardship packages for executive-level candidates in cities that are hard hit with pollution," said Angie Eagan, managing director for China at the recruitment firm MRIC. "These packages are shaped around executives leaving their families in their home country and receiving an allowance for frequent home trips."

Watch: A view of Beijing's smog from atop the Forbidden City

The World Health Organisation said in March that air pollution contributed to seven million deaths worldwide in 2012, with 40 per cent of those coming from the region dominated by China under the WHO's classification system. Outdoor air pollution can cause lung cancer, a WHO agency said last year, ranking it as a carcinogen for the first time.

Panasonic of Japan is considering increasing a living allowance for overseas workers in China by an undisclosed amount based on environmental factors, including air pollution.

Some companies remain reluctant to add to the 5 per cent to 10 per cent premium they already pay foreign employees in China, preferring to compensate them for pollution through perks such as more time off, paid trips to get away or covering the cost of insulating homes, said Fred Schlomann, managing director at human resources firm AIRINC.

A third of European Union Chamber of Commerce companies in China said air pollution had added to human-resource costs as expats made demands such as better pay and health care, as well as air filters, according to Ioana Kraft, general manager of the chamber's Shanghai chapter.

Two-thirds of the companies identified air quality as the top challenge in attracting foreign talent. Some 48 per cent of respondents to a survey this year by the American Chamber of Commerce for Beijing and Northeastern China said they had difficulties recruiting or retaining senior executives in China because of pollution.

James McGregor, Greater China chairman of consultancy Apco, is moving to Shanghai in May after being in Beijing for 25 years and says his wife spends more time in Minnesota in the US Midwest now, partly because of pollution. To provide a clean workplace, his firm installed air filters every 7.6 metres in its Beijing office, about a dozen devices for 30 staff. Even so, employees need more medical leave than 18 months ago.

"There are a lot of sick days, and sometimes our office in Beijing sounds like tuberculosis wards," said McGregor, 60. "People in our office are complaining they don't feel well, they don't have energy."

Levels of PM2.5, the tiny particles posing the greatest risk to human health, were stuck at hazardous levels for a week this year in Beijing and in 2013 peaked at 35 times the WHO's recommended limit. McGregor's firm is able to retain staff because it mostly hires locally. Even so, some clients have said that it's harder luring new talent.

"We're starting to see families not come," McGregor said. "In some cases, people are coming without their families and they are cutting a deal to go home more often."

Shane McNamara, an American executive who runs a 15-person interior design and construction company in China with his wife, said she may move her home base to Hong Kong because of the pollution. His wife, who is Chinese, has reduced work travel because of the bad air, he said.

While McNamara said he would stay on the mainland for business, he has his own health concerns. At his annual check-up at the Mayo Clinic in the US, the doctor told him that "absolutely with that kind of pollution his health would be impacted".

WHO director general Dr Margaret Chan Fung Fu-chun said in a March interview that "talented people have actually talked to me, and they've changed their decision to settle in China because of the air pollution". But, she said, "I think Chinese authorities understand this and they know what's going on."

Simon Gleave, Beijing-based partner in charge of KPMG's Asia-Pacific financial services practice, has spent US$4,000 for an air-quality monitor, US$15,000 for air filters around the house and has an indoor virtual-reality biking system for days when the air is too bad for him to cycle outside.

"If my daughter develops any health effects, though, we would leave immediately," said Gleave, who has lived in Beijing for more than a decade.

Chinese Premier Li Keqiang has called pollution a major problem and said the government would declare war on smog by removing high-emission cars from the road and closing coal-fired furnaces.

Almost two-thirds of the country's wealthy, those with assets of US$1.6 million or more, have left or plan to leave the country, according to the Hurun Report, a Shanghai-based research firm that tracks the country's rich. Environmental concerns are one of their most frequently cited reasons, according to Kristin Shi-Kupfer, who researches Chinese society at the Berlin-based Mercator Institute for China Studies.

Companies from Nestle to Japan's Sony are handing out masks to employees in China. Some are lining their offices with air filters, or hiring experts to coach executives on battling smog. Qoros Auto, a joint venture between an Israeli company and China's Chery Automobile, said it spent about 150,000 yuan (HK$188,000) for purifiers at its offices and 9,750 yuan on masks for employees.

Chris Buckley, a distributor of the Blueair brand of purifiers in Beijing, says corporate demand for air purifiers has doubled over the past year. Company orders could be in the range of US$100,000 to fit out a two-floor office, while mid- to upper-level corporate executives can get allowances of about 15,000 yuan to 20,000 yuan to offset costs of their home purifiers, he said.

Gordon Peters, a doctor who spent more than 30 years in the US Air Force and is now the Beijing-based North Asia medical director for risk advisory firm International SOS, says more corporations are hosting seminars on air pollution protection.

He lectures on checking pollution apps before leaving the house, which face masks to wear (N95 are best, as they block 95 per cent of pollutants), the importance of air purifiers and how to seal windows and doors.

While pollution is seen as a hindrance, companies are still able to attract expats because deep knowledge of the China market is becoming crucial to career and business advancement.

Robert Parkinson from the UK, who owns a 40-person executive search firm in Beijing, just spent more than US$6,000 on two purifiers for his office. While he acknowledges the pressures from pollution, he doesn't see it as a reason to leave because China offers advantages such as career experience, cultural exposure and good expat benefits.

Giambruno, who moved with her girls to Florida, is grateful for the clean air they now have. While the distance and global commute weigh on her and her husband, "that's where his job is right now, and he's got a great job and works for a great company", she said, though she declined to offer specifics of his job.

Even as Giambruno recalls things she loved about Beijing, where she worked as a freelance television producer, she also remembers outings that were cancelled when pollution spiked and smog so thick one January day that she thought she could touch it. She now appreciates Florida's blue skies.

"Every time I walk outside with the girls, I say 'breathe in,' because it's the most amazing smell: fresh air."