Researchers have figured out what makes certain chemicals accumulate to toxic levels in aquatic food webs. And, scientists have developed a screening technique to determine which chemicals pose the greatest risk to the environment.According to the study led by the U.S. Geological Survey, two traits were identified that indicate how chemicals can build up and reach toxic levels:  how easily a chemical is broken down or metabolized by an organism and the chemical’s ability to dissolve in water.These traits account for how most chemicals concentrate, or biomagnify, in ever-higher levels as one goes up the food chain from its base to its top predators, such as fish, people, or polar bears. Chemicals that have the ability to biomagnify, such as DDT, can have adverse effects on human and wildlife health and the environment.