BEIJING, Jan. 8 -- Given China’s importance to major carmakers and Chinese dependence on cars, any proposal to discourage car use, if broached at all, must be tactfully watered down so as not to incur bad feelings.

In recent years in the so-called exemplary first-tiered cities, cars have become so popular that they are evolving from aspirational symbols of the good life to a daily necessity.

I have the courage to raise this sensitive topic, since I am largely emboldened by the recent exchanges over the innocuousness of car exhausts, as some experts allege.

Significantly, this latest attempt at whitewashing cars came at a time of wholesale environmental degradation, particularly damning in the form of pervasive smog. There is a crying need for prompt, and collective action in addressing the issue.

One of the first shots in the auto emissions-smog debate was fired by an otherwise respectable TV host, Cui Yongyuan, who dismissed car emissions as no more polluting than “farts.” Then came Zhang Renjian, a researcher in Beijing, who downplayed car exhaust in a paper claiming that they contribute to less than 4 percent of the smog in Beijing.