The state is cracking down on idling vehicles spewing unhealthy toxins onto city streets.

Officers from the New York State Department of Environmental Conservation checked emissions levels in diesel trucks and buses at 1st Avenue and 124 Street Friday morning. Blocks away, city Department of Environmental Protection inspectors timed idling trucks, and slapped violations on drivers who left the engine on for more than five minutes.

"I didn't know the law," said one driver who was fined. "I won't do it again."

State and city officials say they will crack down unannounced on what they call smoking or idling trucks and buses.

They said the goal is to clear the air in a community where the asthma hospitalization rate is four times higher than the national average.

"Twenty percent of the 10,000 trucks who make daily trips through this corridor emit illegal levels of pollutants through East Harlem," said State DEC Commissioner Peter Grannis.

Harlem resident Beverly Whaley has a son who has asthma.

"He was born with asthma," explained Whaley. "I believe if they cut the engines off buses, if the kids don't smell the fumes, it would help."

Many drivers delivering goods in the early-morning hours said idling is a necessary part of the job – especially in the cold.

"I know it's illegal, but I have to do it," said truck driver Jose Santos. "In the morning, I have to do it. In daytime, I shut it off."

"We like to abide by the rules. This sprinter can be shut off, but the heat I allowed to come in, so it works for us," said driver Alex Dusonic.

There are exemptions to the law that prohibits idling for more than five minutes. Drivers who are in traffic, are loading or unloading, require maintenance with the engine on, or are driving with auxiliary equipment that needs constant power, such as a cement mixer or refrigerated compartment, are excused.

Fines range from $375 to $15,000, and could include jail time.