Many rivers in Europe are in poor health and don’t come close to meeting the European Union’s environmental standards, the World Wildlife Fund said yesterday. The group found that 50 out of 69 river stretches in 16 countries were in trouble; the worst polluted rivers included the Rhone and Seine in France, the Severn in Britain, and the Danube in Austria. In some cases, rivers in Eastern Europe, a region known for its pollution problems, were cleaner than those in Western Europe. Dams, canals, waste-dumping, and runoff from farming were among the causes of the problems. The environmental group said that all European nations should adopt E.U. rules that call for rivers, marshes, and lakes to be restored to their original state by 2015.