Proponents say there’s proof in Montgomery County and in Washington, D.C., which did not ban plastic bags but together started charging 5-cent fees on them in 2009. By 2015, proponents said, the policy reduced plastic contamination in the Anacostia River and other waterways to as little as a quarter of previous levels, though the data has been criticized as being unscientific. There and elsewhere, surveys have shown significant increases in reusable bag use.