DENVER — The air around 11 Colorado schools was cleaner this past school year thanks to a program encouraging parents and schools to take a simple step and turn off vehicle engines.

The Clean Air for Schools: Engine Off! program ran in schools in Adams, Arapahoe, Boulder, Denver, Douglas, Garfield and Mesa counties this past school years, said Kim Tyrrell of the American Lung Association in Colorado.

The program encourages parents and school officials to turn off vehicles while dropping-off and picking-up students.

The year-long program includes collection and analysis of emissions data in and around school properties, an educational campaign spearheaded by school faculty and students, and student-led interventions including securing parent pledges and in-classroom presentations.

On average, the 11 schools reduced emissions by 67 percent or the carbon monoxide equivalent of over 168,000 individual cigarettes no longer being smoked each day, Tyrrell said.

“Human lungs develop until the age of 18, and exposure to excess exhaust and smoke can stunt lung growth as well as contribute to many lung disorders, including asthma,” said Tyrrell.

CASEO was supported by a variety of partners including the Colorado Department of Transportation, International Paper Foundation, Kaiser Permanente and National Jewish Health.