For years, Liu Ruiqiang put up with chronic smog in China's capital of Beijing, but he didn't want to take any chances when his daughter was born.

The salesman now carries a handheld pollution sensor everywhere. On days when air pollution reaches hazardous levels, his toddler daughter is confined to their home, where a pair of constantly whirring air purifiers make it safer to breathe.

Liu, who says he's a lower-middle class Beijinger, estimates he has spent more than 40,000 yuan ($6,375) in the past couple of years to counter the effects of pollution on little Yunshu.

"If we don't think of a way to balance it out or find some basic ways to help us recover, eventually our health will be destroyed," the 37-year-old told Reuters.