Microbiology: A Systems Approach 4th Edition by Marjorie Kelly Cowan

Exercise 15

Critical thinking is the ability to reason and solve problems using facts and concepts. These questions can be approached from a number of angles and, in most cases, they do not have a single correct answer.
PCBs are human-made pollutants that are not synthesized in nature. However, a remote lake in Alaska was found to contain PCBs even though humans had never set foot near this body of water. Based upon what you have learned in this chapter, develop a hypothesis that could explain this finding.