The air is too dirty to breathe in many counties across the United States, according to the Environmental Protection Agency (EPA). The agency is ordering a multibillion-dollar expansion of efforts to clean up smog in cities and towns nationwide. A total of 345 counties are in violation of ozone limits. Electric utilities, oil companies and other businesses wanted to leave the smog rule alone, saying the high cost of lower limits on ozone could hurt the economy. The EPA directed that air must contain no more than 75 units of ozone, or smog, for every billion units of air in order to be considered healthy. The 75 unites is a reduction from the current maximum concentration of 80 to 84 parts per billion. An independent EPA advisory group of scientists last year said an ozone standard of 60 to 70 parts per billion is needed to provide an adequate margin of protection for the millions of people susceptible to respiratory problems. The EPA by law is not supposed to consider economic cost in establishing the federal health standard for air quality. The agency has estimated that new pollution control efforts to comply with a 75 parts per billion standard would cost as much as $8.8 billion a year. However this does not take into account reductions in health care costs that could be even greater.