What is the relation between sex and smog?

Vehicles drive along a road with a traffic sign reading "Visibility low, slowdown the speed" on a heavily polluted day in Beijing.

Beijing: China's capital registered a boom in online orders for condoms and sportswear rather than masks and air purifiers, state media reported on Wednesday, as the city of over 22 million people reeled under the first-ever red alert for rising levels of pollution.

While it is easy to imagine a sharp rise in online orders for anti-pollution products such as masks and air purifiers on smoggy days, a boom in the sales of condoms and sports-wear might be a little unexpected, official media here reported.

According to search ratings for last week provided by Taobao.com, China's largest online shopping platform, searches for condoms were clearly correlated with those Chinese cities that had heavy smog.

Beijing has been engulfed for thick smog for several days in the past few weeks and the city's first-ever red alert was issued on Monday stating that air will remain foul till December 10.

In Beijing and some northern cities that were severely hit by smog, the rise in orders of condoms went beyond the sales in cities with cleaner air, state-run China Daily reported.

Interest in sportswear also increased during the heavy smog. Those cities with serious haze recorded more frequent searches for sportswear, as residents have a stronger willingness to exercise outside once the air gets cleaner.

Beijing has taken a series of emergency pollution control restrictions, ranging from closing industrial operations to reducing road traffic by half.

Beijing's vehicle restrictions of odd and even number plates will last until noon on Thursday.

Many parents complained the sudden closure of schools for three-day which has warranted them to stay back to take care of them and felt schools are better equipped to deal with pollution than homes.

A Beijing resident said an air purifier has been installed in the school with funds raised from parents.

"We don't have air filter at home. In all aspects, learning at school on smoggy days better than doing it at home," she said.

Although coal-burning is strictly banned in downtown Beijing and some of its suburban areas, coal is still being used for home heating in all rural areas of the smog-affected northern provinces.

Xie Shaodong, an environmental professor at Peking University, said, "The main cause is the widespread use of low-quality coal in rural regions and in areas with a lack of environmental supervision."

Chai Fahe, deputy director of the China Research Academy of Environmental Sciences, said that even in distant suburban areas of Beijing pollution remains heavy because coal is used for heating and rules are not being enforced strictly.