Providing initial evidence that airport are a larger source of pollution than they were once believed to be, environmentalists in Chicago report that the total amount of pollutant emitted annually by vehicles at O'Hare International Airport is twice as much as that which is being emitted annually by all motor vehicles in the Chicago metropolitan area.

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• Bas much annually as is emitted by the  
• Cas much compared to what is annually emitted by all  
• Dthat emitted annually by all  
• Ethat emitted annually compared to the