A study that found high levels of toxic chemicals in the air in a heavily fracked county in Ohio has been retracted by its authors after they say they discovered errors in their calculations.

The erroneous calculations led the researchers from Oregon State University and the University of Cincinnati to conclude in the original study that air in Carroll County, which has 480 permitted fracking wells, contained levels of polycyclic aromatic hydrocarbons (PAH), that were above the thresholds higher than the Environmental Protection Agency considers safe. PAH are organic compounds containing carbon and hydrogen and are found in fossil fuels.

The retraction notice said: “After publication the authors discovered a mistake in the air concentration calculations. PAH air concentrations reported in the original article are therefore incorrect. The calculation error resulted from using incorrect units of the ideal gas constant, and improper cell linkages in the spreadsheet used to adjust air concentrations for sampling temperature. Correcting this error changes air concentrations significantly relative to those reported in the published article. This correction also changes some of the conclusions reported in the original article.

Due to the impact of this correction on the reported findings, all authors retract the original article. The original article was published on March 26, 2015 and retracted on June 29, 2016.”

InsideClimate News reported on the original study, which was published in the journal Environmental Science and Technology. The retraction was first reported by Retraction Watch.