A Louisiana refinery run by San Antonio-based Valero Energy Corp. was among a dozen that exceeded federal pollution limits for the carcinogenic chemical benzene in 2021, according to a report from the Environmental Integrity Project. The new study, based on self-reported data to the Environmental Protection Agency, notes that all 12 of those refineries last year surpassed the federally set “action level” threshold of 9 micrograms per cubic meter. Under federal guidelines, polluters are required to take corrective action once they hit that level.