Air pollution can worsen any pre-existing lung condition Air pollution can worsen any pre-existing lung condition. Heavy smog, rated as 'Hazardous' by the the U.S. embassy air quality monitor, hangs over Beijing's central business district on February 22, 2013. Chinese officials have admitted for the first time that decades of reckless pollution management has led to severe health and social problems, as the government lays out a five-year plan for environmental improvement. DALLAS, May 30 (UPI) -- High levels of air pollution can increase asthma, respiratory infections, lung cancer and even death, and heat makes it worse, a U.S. researcher says. Dr. Jonathan Weissler, director of the James M. Collins Center for Biomedical Research at the University of Texas Southwestern Medical Center in Dallas, said the combination of sunlight and heat essentially bakes the atmosphere and the various airborne chemical compounds. This chemical concoction mixes with naturally occurring nitrogen oxides in the air to create smog, or ground-level ozone, Weissler said. "Oxides of nitrogen and sulfur, smoke and ozone are irritants of the airways and can worsen any pre-existing lung condition," Weissler said in a statement. People with chronic lung disease should try to minimize their time outdoors when air quality becomes extremely poor. Dallas/Fort Worth has consistently ranked among the nation's list of cities with poor air quality, Weissler said. The 2012 State of the Air Report, released in late April by the American Lung Association, ranked the Dallas/Fort Worth Metroplex 12th worst among 232 U.S. cities for ozone-related air pollution -- the most hazardous type of pollution to health. Los Angeles tops the list, followed by six other California areas: Visalia, Bakersfield, Fresno, Hanford, Sacramento and San Diego.