By Charles Pekow Hopes for a worldwide plastics treaty gained some momentum at the fourth of five scheduled summits to hash out an agreement. But while the week-long session of the UN International Negotiating Committee made some headway, it didn’t leave environmentalists feeling overly optimistic. INC-4, which took place the last week of April in Ottawa, Canada, was the latest step in a United Nations effort to develop international law to control plastic pollution. Representatives of 170 nations converged on Ottawa, where they greatly shortened a lengthy draft text, and reached consensus on …