Pollution has gotten this bad in China:
International schools are racing to buy sealed domes that cover playgrounds, enabling children to play on days when it is unsafe to run outside, said Mary Ren, product director at the Beijing division of Yeadon, which makes bubblelike domes that purify and pressurize air. Yeadon installed a $650,000, 18,000-square-foot dome at international school Dulwich College Beijing in 2011, Ms. Ren said.
Dulwich sends children into the dome, equipped with basketball courts and special lighting, when the air quality index hits 250, said Cynthia Maclean, head of external relations at Dulwich. By comparison, New York's air quality index was 30 on Friday morning.