At first glance ，concerns regarding motor vehicle pollution in China seemmisplaced.With a population more than four times as large as the United States（1.22billion versus 268million ）the number of cars ，trucks，and buses inChina is a mere fraction of that in the United States （less than fourteen millionin China versus 210million in the United States）。On a per capita basis，Chinahas one of the lowest vehicle populations in the world，as illustrated in Table1.According to Table 1，it is clear that among these countries only India hasa lower vehicle ownership density than China.However ，to stop at this superficialoverview would be very misleading.In recent years，the vehicle population in Chinahas been increasing sharply ，with much of this growth taking place in cities.Nationally，the annual growth of vehicles has averaged approximately fourteen percentper year.One result of this rapid growth has been the emergence of serious airpollution problems，especially in cities.Furthermore，the growth in vehiclesin China is expected to continue and perhaps even accelerate in coming decades，increasing concerns regarding further environmental degradation.Chinese policymakershave begun to respond to the growing problem of air pollution.For example the governmenthas initiated a public reporting system whereby a growing number of Chinese citiesare now routinely reporting their current air quality ，as illustrated by the mostrecent data summarized in Table 2（following page）。
As Table 2shows，several cities have an air pollution index above 400fortotal suspended particulates（TSP ），which means these cities measured TSP levelsabove 875mg/m3（micrograms per cubic meter）。
Table B illustrates that most Chinese cities already have serious air pollutionproblems particularly with TSP and nitrogen oxides（NOx ）。As this informationhas become publicly available ，citizen pressure has been buil
