Although development in the Marcellus shale has leveled off, a recent study done by Drexel University has found atmospheric methane levels in the area are still incurring, according to Phys.org.

Measurements of methane and other air pollutants taken from 2012 to 2015 in the rural areas of Pennsylvania that have been the hub of natural gas development over the last 10 years, showed substantial increases.  The research found that methane levels increased 100 parts per billion over the last three years, while the global increase was without natural gas development rose six parts per billion.

Natural gas production has increased to 16 billion cubic feet per day in the Marcellus Shale region, doubling in the last three years, despite about half as many wells being drilled in 2015 as there were in 2012.

The findings suggest that measures taken to decrease methane leakage from well completions are not sufficient.

Learn more: Phys.org > Methane levels have increased in Marcellus Shale region despite dip in well installation