Officials from more than 100 nations will gather in Montreal later this month to begin negotiations on phasing out a dozen toxic chemicals. Scientists call these toxins “Persistent Organic Pollutants” because they lodge in the fatty tissues of people and animals, and can cause health problems from reproductive defects to cancer. Here to give us a preview of the talks is Cliff Curtis, director of the World Wildlife Fund’s global toxics campaign, and Mr. Rafe Pomerance, Deputy Assistant Secretary of State for the Environment. Laura Knoy asked them which chemicals are at issue and why there is concern.