Bulgaria's Bad Air Highlights European Pollution Problem

"Hold your breath if you visit Bulgaria," writes Danny Hakim. "The air in the small Black Sea nation is thicker with several major air pollutants than the air in any other country in Europe, according to a new study prepared by Europe’s environmental regulators."

"But Bulgaria is hardly alone in having air quality challenges," he adds. "While Bulgarian cities lead in the concentration of particulates, Poland is a frequent runner-up, and cities in northern Italy lead in ozone, according to separate data provided by the agency.