School bus drivers need to shut off their engines, according to a study released by the Environmental Protection Agency Monday.

EPA representatives were flanked by Department of Education officials and other groups while they discussed the results at a Hunts Point elementary school. According to the study, an engine idling for three minutes or longer generates more pollution than shutting off an engine and restarting it.

The agency said it's a major problem because many drivers believe they're actually helping the environment by idling. While non-idling laws already exist, the EPA wants better enforcement. Officials are also urging the city to retrofit school buses with filters that cut exhausts.

Health experts link vehicle exhausts to rising asthma and respiratory rates in Bronx and city children.