WASHINGTON (Reuters) - Children riding on school buses are breathing in more pollution than people standing out on the streets, U.S. researchers reported on Tuesday. They found that exhaust from the buses was leaking into the passenger cabin, and probably affecting the children. Older buses were the worst, they found. And exhaust "scrubbers" did little to help, perhaps because the exhaust is coming inside before it gets to the devices, the team at the University of California, Berkeley, found. "In a single day, a child riding a school bus will breathe in anywhere from seven to 70 times more exhaust...