The city of light is really hard to see these days

Thomson Reuters — Air pollution in Paris has hit health-threatening levels over 80 percent higher than in London and Berlin as a sunny spell reaches western Europe, prompting the city to curb road speeds and offer free public transport.

Charges were also waived for the city's pioneering cycle and electric car-sharing schemes this week as a visible haze hung over the streets of the French capital.

Background pollution — the outdoor air quality experienced by the average citizen — topped the 100 maximum measurable index level in Paris on Thursday, data from pollution watchdog airqualitynow.eu showed, making the French capital the only European capital in the "very high" level zone.