I walked really close in front of a huge truck and the fumes were really bad. could this put me at risk for lung cancer?

Small risk; no habit: Don't make a habit of breathing in fumes, because the more you breathe in, the more it puts you at risk for lung cancer in the future. However, the risk is cumulative. ONE day of breathing polluted fumes won't cause lung cancer, but day after day, the risk adds up. I wouldn't worry about the truck, but if you're REALLY worried of pollution, make effort to move to a cleaner location in the future.