Metra is now looking for ways to cut pollution at its stations and on its trains. That follows a newspaper investigation that found diesel soot levels inside some trains are much higher than normal.

Diesel exhaust is packed with respiratory irritants and cancer-causing chemicals. And the Chicago Tribune recently found soot levels on some trains are 72 times higher than the air outside.

Metra says it’s now testing the air inside train cars and at several stations, and has formed a task force to look at long-term fixes to its pollution problem. At a meeting Friday, officials said that could include restructuring train ventilation systems, making changes to locomotive engines and using different types of fuel.

Brian Urbaszewski is with the Respiratory Health Association of Metro Chicago.

“Honestly, you know, a lot of Metra’s fleet is 20 to 40 years old,” Urbaszewski said. He suggested Metra should start to “look at replacing some of that equipment with more modern equipment that meets much tighter emissions standards.”

But Metra says new locomotives cost about $4.5 million, and retrofitting old engines runs about $1.7 million a piece. Those high costs could be prohibitive, given the commuter rail agency’s 146-locomotive fleet, said acting executive director Bill Tupper.

“We have limited funds, just like everybody else, so we have to look at where we have money available and what’s the best use of our money,” Tupper said.

Until Metra finds a more permanent fix, it’s directing some trains to be turned off while they wait at the platform inside stations.