air quality levels this summer were some of the worst this decade in several eastern states of the us , according to the Environmental Protection Agency ( epa) . "It's not the worst on record, but far from what it should be to ensure public safety,' said Carol Browner, epa administrator. For example, New York City recorded 14 days so far this year when the prime ingredient of smog, ozone, was above a Federal threshold of 120 parts per billion for an hour. That compares with 7 days in 1998. The high for New York was 43 days in 1988, a record year for most eastern cities.

Smog levels in the 1990s are generally down from the 1980s because government regulations have forced industries and automakers to adhere to stricter emissions standards. However, the regulations have not been enough to eliminate violations, officials said, especially with more drivers using more gasoline and with industries burning more fuels such as coal. In Washington dc, the levels were above the 120 parts per billion mark on seven days, the highest since 1993; Baltimore and Philadelphia also experienced one of the worst years in the 1990s. Unusually warm weather could have also played a part.

Meanwhile, scientists have found evidence that carbon monoxide ( co) levels are falling in several eastern states of the us , an indication that efforts to curb pollution are finally paying off. Monitoring in the state of Virginia show that there has been a steady decrease in co levels. co is one of the by-products of burning fossil fuels such as oil and gas.