(FORTUNE Magazine) – Dead seals did for Europe's environmental awareness last summer what medical waste did in the U.S. After 12,000 of the creatures washed up along the coasts of the heavily polluted North Sea, voters spoke out in favor of tougher laws. Environment-conscious Swedes gave their radical Green Party nearly 6% of the popular vote in recent elections, sending 20 Greens to parliament for the first time. That's second only to the 44-strong Green faction in West Germany's lower house. In Japan, which launched an industrial cleanup in the 1970s, rising traffic and an economic boom have allowed pollution to rebound. The most remarkable change in Europe has been the about-face of Britain's Margaret Thatcher. A few years ago the Iron Lady sternly denounced environmental pressure groups as ''the enemy within.'' But in her first major speech on the subject after nine years in office, Thatcher recently called protecting the environment ''one of the great challenges of the late 20th century.'' She identified acid rain, ozone depletion, and the greenhouse effect as major concerns. Her words have already brought one big policy change. Last year, at an international conference in Montreal, Britons were among those who successfully blocked a proposed 80% reduction in ozone-destroying CFC emissions by 1999. Within days of Thatcher's speech, Lord Caithness, her environment minister, declared that Britain is now determined to slash CFC emissions by 85% ''as soon as possible.'' Europe's environmental agenda for the 1990s presages a bigger spending rise, in relative terms, than the U.S. faces. No. 1 on the priority list is probably the North Sea. At a conference last year the countries that border its befouled waters pledged to cease all dumping of sewage sludge and the burning of toxic waste in ships like the one at left by the mid-1990s. West Germany's environment minister estimates that his country alone would need to spend $11 billion on the North Sea cleanup. Next in urgency comes auto exhaust pollution. West Europeans have been slow to adopt catalytic converters, mandatory on new U.S. cars since the mid-1970s. Despite evidence that mounting car and truck traffic is defiling urban air, France recently scuttled an EEC plan that would have called for modest pollution controls on the small cars that account for about half the European market. Peugeot, a major French employer, convinced the government that such a rule would make its cars too expensive, costing sales and ultimately French jobs. By 1994, however, catalytic devices will be mandatory throughout the EEC for larger cars. Just as Canada rails against sulfur oxides from the U.S., Scandinavia and other downwind countries point the finger at Britain. Last June the EEC's 12 members ended five years of wrangling and agreed on who should cut back and how much. Britain, West Europe's biggest contributor of sulfur oxides, will go beyond what is required in the U.S.: It will install scrubbers on old coal- burning power plants. Even the Germans, who already match the toughest U.S. standards, will have to spend heavily polishing their pristine performance.