Increased regional sulfur dioxide emissions likely caused more view-blocking pollution haze in the Great Smoky Mountains and Shenandoah national parks during the 1980s, say UC Davis researchers, but the haze shows signs of abating. Their new study, recently presented at a scientific conference, answers lingering questions about a key scientific assumption behind the 1990 Clean Air Act amendments -- that air quality will improve in proportion to reduced emissions. The analysis confirms that the East has been steadily losing its struggle to maintain postcard-perfect views of favorite summer vacation spots. However, during the past three years, reduced sulfur dioxide emissions from several power plants appear to have reduced the sulfate haze slightly in the Great Smoky Mountains and Shenandoah parks -- although it's too early to tell if this is a reversal of the trend toward hazier skies, says Thomas Cahill, head of the UC Davis Air Quality Group and professor emeritus of physics and atmospheric science. The haze may be linked with increased regional affluence and rapid growth of whole-house air conditioning (from 27 percent to 38 percent during the decade beginning 1980), which apparently skewed the electricity demand toward greater summer sulfur dioxide emissions from power plants, Cahill speculates.