Approximately 10% of the 126,000 sites in the United States that currently contain contaminated groundwater are unlikely to be completely restored for decades, a new report from the National Research Council concludes.

After several minor-to-moderate earthquakes shook the U.S. interior in 2011, a number of reports suggested a link between hydraulic fracturing—a technique used to extract natural gas from shale-gas deposits—and increased seismic activity in areas typically not prone to such events.