An environmental advocacy group is calling on the city to cut down on school bus pollution that it says could be putting Bronx children at risk.

In a new study, the Environmental Defense Fund says the air inside school buses can be about five times more polluted than that circulating outside. The study says the soot coming from the buses' tailpipe seeps in through windows.

"We know that the kind of pollution that comes out of a diesel bus can cause things like worsening of asthma," says Dr. John Balbus, a scientist with the group. "It has substances in there that inflame the lungs."

The advocacy group says the city has $7 million of federal funding that must be devoted to cleaning up New York's air. They are asking the city to use that money to either buy new buses or retrofit older buses by putting a filtering device on tailpipes and engines.