Trucks are the mules of this country’s spectacularly expanding economy — ubiquitous and essential, yet highly noxious... Tiny particles of sulfur-laden soot penetrate deep into residents’ lungs, interfering with the absorption of oxygen. Nitrogen oxides from truck exhaust, which build all night because cities limit truck traffic by day, bind each morning with gasoline fumes from China’s growing car fleet to form dense smog that inflames lungs and can cause severe coughing and asthma... Yet cleaning up truck pollution presents complex problems for China’s leaders... “Sinopec is trying our best to purchase low-quality crudes — much heavier and more sulfur content,” said Evan Jia, a Sinopec spokesman. “We buy those kinds of crudes to lower the purchasing cost.”... [The] pollution...contribut[es] each year to hundreds of thousands of premature deaths from heart and lung problems, according to the World Bank... Even the most modern cabs [made by Sinotruk (China National Heavy Duty Truck)] have engines that emit at least three times the levels of nitrogen oxides of new American trucks and at least seven times the particles — even with clean, low-sulfur diesel... [J]ourneys are tough on drivers’ health, as they breathe the exhaust of the trucks ahead of them.