Beijing's skyline hid under particle-filled smog on Tuesday, as China's capital city and about 10 percent of the country faced an environmental alert for overly polluted air.
Here's how the China's latest air quality crisis, crippling cities for the sixth day running, breaks down.
4: The number of notches on China’s new color-coded environmental alert scale. For the first time on Tuesday, the government raised the warning to the second-highest level, Orange.
147: The number of companies that have suspended or cut back production this week, as part of Beijing’s response to the Orange Alert.
500: The reading on the Beijing US Embassy’s air quality indicator on Tuesday, that measured particulate matter in the air. That’s 20 times the level considered safe by the World Health Organization.
1,300: The number of microbial species that inhabit Beijing's air, scientists discovered after sequencing DNA extracted from 14 air samples taken over 7 days. The smoggiest days even saw a bump in bacterial counts, they reported in January this year.
19.3 million: The number of vehicles on China’s roads in 2013. Trucks make up 5 percent of that traffic, but belch out 60 percent of the particle pollution generated by vehicles. Beijing hosts an estimated 5 million vehicles, but industries carry the blame for much of the serious pollution in that region.
50 percent: The fraction of people who are checking into respiratory wards when they they're admitted to hospitals, a hike up from the usual 20 percent, according to the Beijing Morning Post.
1: Lawsuits brought against the Chinese government over spiking levels of pollution. A man from the industry-heavy Hebei province sought compensation for the cash he spent on "face masks, an air purifier and a treadmill to get indoor exercise."
$141 million: How much Chinese shoppers spent on protective face masks last year, and that’s just on one e-commerce site Taobao. The masks have become a fashion (and health) staple among city dwellers, but their benefits are up for debate.