Climate change will increase U.S wildfires, and the smoky air will cause terrible problems in areas far beyond those burned, reports an environmental group Thursday.      Two-thirds of Americans, or nearly 212 million, lived in states suffering from wildfire smoke three years ago, according to the report by the Natural Resources Defense Council (NRDC). These areas, which had smoke for at least a week, were nearly 50 times greater than those burned directly by fire. " It affects a much wider area of the United States than people have realized, " says author Kim Knowlton, a Columbia University health professor, adding the smoke can move up to hundreds of miles. She says the smoke contains air pollution and can cause several kinds of disease. Texas was hit hardest in 2011, when smoke stayed for at least a week in areas that are home to 25 million people, according to NRDC's report. Illinois, which recorded no wildfires within its borders( ) ,ranked ( ) second with nearly 12 million people affected by smoke that moved in from elsewhere. The other eight states with the most people exposed ( ) to smoky air were, in descending ( ) order: Florida, Missouri, Georgia, Louisiana, Michigan, Alabama, Oklahoma and Iowa. Nearly two dozen states had no wildfires within their borders in 2011, but eight of them still had at least one week of smoky air: Illinois, Missouri, Iowa, Kansas, Nebraska, Indiana, Wisconsin and Ohio. Only 18 states and the District of Columbia had no people exposed to at least a week of smoke that year, although five of them----Alaska, California, Hawaii, Nevada and Utah---had a large area burned by wildfires. The problem will only get worse, Knowlton say. Scientific research shows climate is causing higher temperatures and health problems. What would be the best title for the passage?
Climate change causes more wildfires. More wildfires cause climate change. Wildfire smoke becomes a serious health problem. Air pollution becomes a terrible problem.