Beijing's Olympic shutdown begins Sunday, a drastic plan to lift the Chinese capital's gray shroud of pollution just three weeks ahead of the games. Half of Beijing's 3.3 million vehicles will be pulled off the roads and many polluting factories will be shuttered. Chemical plants, power stations and foundries left open have to cut emissions by 30 percent - and dust-spewing construction in the capital will be halted. Striking venues and US$40 billion spent to improve infrastructure cannot mask Beijing's dirty air. A World Bank study found China is home to 16 of the 20 worst cities for air quality. Three-quarters of the water flowing through urban areas is unsuitable for drinking or fishing. Under the two-month plan, vehicles will be allowed on the roads every other day depending on even-odd registration numbers. In addition, 300,000 heavy polluting vehicles _ aging industrial trucks, many of which operate only at night _ were banned beginning July 1.