By Brendan O'Brien(Reuters) -Severe weather disrupted parts of the United States on Wednesday, with a tropical storm skirting Hawaii, a tornado ripping over a North Carolina pharmaceutical plant and a relentless heat wave broiling the country's southern tier. AIR QUALITYAlthough most air quality alerts across the nation expired on Wednesday morning, smoke from Canadian wildfires drifting across the United States caused poor conditions in several spots in Virginia, the Carolinas and along the East Coast. 6 on a list of major cities around the world with the worst air quality, according to IQAir