Paris Spent €1.4 Billion to Clean Up the Seine. Has It Worked?

Eight years after Paris city officials resolved to clean up the Seine once and for all, the city has declared victory over the E. coli, enterococci and other assorted micro-organisms that for centuries struck down the unfortunate bather. To show off the river’s newly pristine waters, the Seine was chosen to host the Olympic open-swimming competitions — marking the first time that an urban river has been used for swimming events at the Games since they were revived in 1896.

It’s a risky move: The Seine has long had a dirty reputation, and swimming in the river has been banned ...