Transportation is a primary contributor to the high levels of air pollutants in Southern California and the Central Valley. Diesel emissions from trucks are one of the state’s largest sources of fine particle pollution, or soot, which is linked to health issues including asthma, impaired lung development in children, and cardiovascular effects in adults. Many of these trucks are older models and emit high amounts of particulate matter (PM) and nitrogen oxides (NOx).

uhhh.. I'm pretty sure all those Chinese cargo ships sitting in the bays are FAR WORSE than all the trucks, combined. Let me guess, no obligation on China for cutting emissions from those ships.