FOR decades the United States and other industrial nations have sought to balance their dependence on automobiles and the necessity to control, if not eliminate, exhaust emissions.Success has been elusive. Now a combination of developments offers some hope that lasting remedies for the smog that has long plagued most large cities and even cast its pall over less-urban areas may be within reach. Officials of nine Eastern states and the District of Columbia have committed themselves, in varying degrees, to adoption of California's stringent standards for reducing exhaust emissions. California's law, adopted in 1990, gradually heightens emission standards. It requires that, by the year 2003, 10 percent of new cars sold by the automakers be "zero-emission" (probably battery-operated) vehicles. And it assumes that cleaner-burning gasoline will be available by 1995. The usual demurrers from the oil and auto industries have been heard. Service-station owners warn that the more sophisticated and costly equipment required would put many of them out of the inspection business, as well as costing car owners much more than at present. Researchers for oil and auto companies argue that the proposed standards would be too costly and of doubtful effectiveness in many states. Drastic reduction of harmful emissions from autos, power plants, industrial plants and implements, and other sources will be costly. It is no surprise that US automakers, their sales dishearteningly low and their loses disturbingly large, are not eager to participate in a smog-reduction plan that would have a substantial impact on costs, sales, and profits. But California and the other states signing on to its plan are facing up to the fact that, whatever the cost, the air pollution problem has to be met head-on. Over the past three decades there has been a pattern of producing blue-sky antipollution plans that fall short of their goals or are simply ignored. Surely, after all this time, the American public must be aware that further dithering will, in the long run, prove much more costly than paying the price for clean air.