LOS ANGELES, Cal. — A University of California study has shown a direct link between diesel exhaust and a hardening of the arteries which can lead to strokes.

Dr. Andre Nel, principal study author, said exposure to diesel exhaust combined with blood cholesterol can create a dangerous synergy that wreaks cardiovascular havoc. The two-punch combination of diesel exhaust and cholesterol is far more damaging than either of those would be alone, he concluded.

His findings were published in the online science journal Genome Biology. The study is the first to show a correlation between diesel particulate matter and cholesterol and their ability to cause cardiovascular problems.

“I think the general idea is now that everybody will accept that air pollution is an independent risk factor of cardiovascular disease,” says Nel. “The thing that is exciting is we now have an integrated … theory of how air pollution might cause adverse health effects.”