Pay packages for expats often include extra cash for employee housing, private schools and security. Next up: Extra money for air pollution?

Coca-Cola Co. now offers environmental hardship pay for employees who have relocated to China, where smog has reached harmful levels in several cities, the company said this week.

A spokesperson for the Atlanta-based beverage giant declined to confirm the value of the wage premium or how many employees are eligible for the benefit. The Australian Financial Review reported the allowance to be around 15% of an employee's base salary.

It is not uncommon for multinational companies to provide hardship allowances to incentivize employees to work in China, in part because of the heavy levels of smog, said Ed Hannibal, global leader of the mobility practice at HR consulting firm Mercer LLC. He said the value of hardship pay will depend on where the office is located, as some cities have higher levels of pollution than others.

"They will provide that as a compensation tool in order to offset the severe living conditions and to keep people on the ground," Hannibal said. Many companies also pay for air or water purification systems to be installed the homes of China-based employees, he said.