FAIRBANKS, Alaska (AP) — In the pristine expanse of Alaska’s interior lies a dirty secret: some of the most polluted winter air in the United States can be found in and around Fairbanks. The Fairbanks area routinely exceeds limits set by the U.S. Environmental Protection Agency for particle pollution that can be inhaled and cause health problems, even death. Over seven weeks this winter, nearly 50 scientists from the U.S. and Europe descended on Fairbanks to study the sources of air pollution and how they interact in the city’s cold and dark climate. The goal is to come up with a list of best practices for people around the world who live in the circumpolar north. Results will be shared next year.