Some 600 delegates from more than 120 countries began a week of talks yesterday in Johannesburg, South Africa, to try to reach agreement on a treaty to ban 12 persistent organic pollutants (POPs), chemicals such as PCBs and several pesticides that have been linked to cancer, birth defects, and genetic abnormalities in humans and wildlife. Among other issues, delegates are debating whether to ban DDT in countries such as South Africa that use the pesticide to fight malaria. Many developing countries support its continued use until other ways are found to combat the disease, while enviro groups like Greenpeace want the pesticide banned worldwide immediately. Also, the U.S. is leading the charge against a European Union initiative that would make it easier in the future to ban additional chemicals under the treaty. Meanwhile, the World Wildlife Fund released a map yesterday pinpointing what it said were the 10 most toxic hotspots in the world; the list included parts of South Africa, the U.S., Japan, Russia, Canada, and Ethiopia.