Ten US oil refineries released benzene emissions that exceeded federal limits last year, according to government data from green group Environmental Integrity Project (EIP).
The study is based on the first full year of data reported by US refineries since a US Environmental Protection Agency (EPA) rule was implemented in 2018.
"These results highlight refineries that need to do a better job of installing pollution controls and implementing safer workplace practices," EIP executive director Eric Schaeffer said in a statement. "Now, EPA needs to enforce these rules."
Long-term exposure to cancer-causing benzene can cause blood disorders and leukemia, according to EIP.
According to the report, benzene levels consistently exceeded the EPA standard of nine micrograms per cubic meter of air at the fence-lines of 10 of the more than 100 refineries examined by EIP.
Philadelphia Energy Solutions' refinery in Philadelphia recorded the highest benzene concentrations, at nearly five times the EPA standard, the data show.
HollyFrontier Corp's Navajo Artesia plant in New Mexico followed, with more than three times the federal standard.
Philadelphia Energy shut that refinery and filed for bankruptcy in July after a fire destroyed part of the plant.
Texas was the worst performing state, with six refineries exceeding the federal benzene standard, according to the report.
The Texas refineries, which emitted excessive benzene levels are: Total SA's Port Arthur Refinery, Chevron Corp's Pasadena Refinery, Flint Hills Resources' Corpus Christi East Refinery, Valero Energy Corp's Corpus Christi East Refinery, Royal Dutch Shell's Deer Park Refinery, and Marathon Oil Corp's Galveston Bay Texas Refinery.
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