Wearing surgical masks to draw media attention, Greenpeace activists sailed out of Russia yesterday on a month-long crusade to raise public awareness about the problems of chemical pollution in the Baltic Sea. They will visit Estonia and other spots along the sea before arriving in Stockholm, Sweden, where officials from countries around the world are convening toward the end of May to show their support for a treaty phasing out some persistent organic pollutants (POPs). Greenpeace says that POPs in the Baltic Sea may be responsible for lower birth-weights and slower development among some children born in the region, and that the treaty should be viewed as only one step toward addressing the problem.