HOUSTON (Reuters] – A study released by Environmental Integrity Project on Thursday found that nine U.S. Gulf Coast oil refineries exceeded federal regulations for pollution from benzene in the period 2018 to 2020. This causes cancer.

According to the study, these nine refineries are among 56 U.S. facilities with high levels of benzene. Sixty-four per cent of 56 refineries in America are found along the Gulf Coast of Texas, Louisiana, and Mississippi.

Tom Pelton, spokesperson for EIP, stated that the study was meant to impress the U.S. Environmental Protection Agency.

“We want the EPA to enforce their own rules,” he said, adding that the EPA’s benzene rules grew out a law suit by EIP.

Representatives for the refiners PBF Energy and Phillips 66 are available (NYSE:), Chevron Corp (NYSE: ) stated that they made operational improvements or had removed equipment from their Chalmette, Louisiana and Lake Charles refineries, Louisiana. This was to reduce benzene emissions below the EPA’s 9 micrograms per square meter.

Marathon Petroleum (NYSE:), the nation’s largest refiner, and TotalEnergies said Winter Storm Uri in 2021 drove up the average of fenceline benzene levels at their refineries in Texas.

Jamal Kheiry from Marathon said that his company was working on reducing benzene polluting, except for atypical events like Uri, which “negatively affected annual averages.”

Marathon’s Galveston Bay Refinery in Texas City, Texas, and Total’s Port Arthur, Texas, refinery were shut by Uri along with multiple refineries in the state as Uri caused ruptures in pipelines that supply electrical power plants.

Refineries can burn hydrocarbons stored in their safety flare systems during unplanned shut downs. The refining process produces benzene, which is part of gasoline.