Air pollution that has turned Paris skies a murky yellow is giving a break to millions of French travelers – all public transportation in the Paris region and two other cities is free for the next three days. Nearly three-quarters of France is under alert in what the European Environment Agency says is the worst air pollution since 2007. Subways, buses and trains are free Friday through Sunday in the entire Paris region, as well as the cities of Caen and Rouen. Bike-shares are also free, as are one-hour sessions for electric car shares. Meteorologists say unusually warm days followed by cool nights have worsened the situation. An environmental group brought a complaint earlier this week denouncing the “inertia of the government” that it says has put lives in danger.