In a story analyzing a possible cancer cluster in the three communities surrounding the former Naval Air Station-Joint Reserve Base Willow Grove, the current Horsham Air Guard Station and the former Naval Air Warfare Center, The Intelligencer turned to Civil and Environmental Engineering Associate Professor Christopher Higgins to explain whether the different cancer rates could be directly tied to the amounts of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) recently found in their drinking water. "There are so many factors for how long the compounds take to move from ....