According to a Tribune investigation, Metra's aging fleet of locomotives emits high levels of diesel pollution, a toxin linked to cancer, heart attacks, respiratory diseases, diabetes, and brain damage. The air trapped inside stainless-steel train cars, for example, contains levels of diesel soot up to 72 times higher than on the streets outside. The transit agency says it is doing the best it can to clean up trains on a tight budget and have now scheduled a meeting to discuss the problem Tuesday with federal, state, and local officials.

UPDATE (2:20 p.m.): U.S. Senator Dick Durbin is calling for an Environmental Protection Agency investigation into the pollution coming from Metra trains in response to the Tribune's coverage this morning.