The University of Tennessee performed a study that found harmful air pollutants entered the truck cab while the truck idled for long periods of time. Typically, trucks park and idle alongside other trucks during mandated rest periods. In this situation, the amount of pollution entering the truck In fact, according to this study some trucks showed in-cab concentrations of harmful pollutants that were higher than the outside air. Why. Because once the air gets into the truck cab it stays there and accumulates more harmful pollutants. If a truck driver is sleeping in the truck cab, he or she is breathing that unhealthy air for their entire rest period.