Warning: Driving Could Be Hazardous to Your Health

Under the plan, 20 percent of the space or time of any auto ad would have to be set aside for information on a car's fuel consumption and carbon dioxide emissions, cited as a contributor to global climate change. So, should we prepare for warnings along the lines of, "Driving this car may damage the health of the planet"?

Perhaps not just yet. The European Union lawmaking road is long and curvy, and the Parliament cannot initiate legislation. Instead, it sometimes tries to legislate by press release, taking populist stances in an effort to put pressure on industry and the European Commission. The commission, which holds much of the real lawmaking power within the 27-country bloc, often takes a softer line.

Chris Davies, a British member of the European Parliament who sponsored the measure, said the proposed labels could make a difference. Many auto ads now seem to be aimed at enticing consumers to buy bigger, faster, more gas-guzzling cars than they need, he said. "The rationale is to try to get carmakers to compete on environmental information about their cars, rather than purely on power, speed and appearance," he said.