Then in the 1980s and 90s, Canadian and Scandinavian scientists showed that the bodies of polar bears contained high levels of industrial pollutants. Learning more about the extent to which the bears could break down and eliminate the chemicals dovetailed with James' expertise in how the body metabolizes drugs.
"There is no difference to the body in metabolizing a drug or a pollutant," she said. "The process is the same."
In her research, James concentrated on five types of chemical contaminants known by the acronym POP, for persistent organic pollutants. They include compounds produced by a burning process; a compound used as a substitute for the pesticide DDT when it was banned, and which itself was subsequently banned in 2004; TCPM, an industrial compound found in the Arctic but of unknown origin and toxicity; PCP, used as a wood preservative; and PCBs, industrial chemicals used for many years in electrical applications. All of these substances, with the exception of TCPM, are regulated or banned, but they persist in the environment.
Polar bears break down these fat-soluble chemicals in two steps, each of which makes the substances more water-soluble and therefore easier to excrete, said James. The first step, however, results in a compound that is more chemically reactive and therefore more harmful to living cells, with the potential for reproductive or neurological damage. The second phase, often slower than the first, determines how successfully the animals eliminate the toxins, she said.
Studying liver tissue samples obtained from the bears, James found that the animals were surprisingly efficient at metabolizing one of the types of industrial chemicals studied those produced by a burning process, which are similar to the compounds that form when meat is cooked on a grill. The other pollutants, she determined, could not be fully excreted.
"This suggests that other species will metabolize the pollutants more slowly," said James. "When they are not sufficiently excreted the levels go up."