The nation's worst polluting plant is the BP PLC oil refinery where 15 workers died in an explosion last year, raising questions about whether the company has been underreporting toxic emissions.
BP's Texas City refinery released three times as much pollution in 2004 as it did in 2003, according to the most recent data from the Environmental Protection Agency.
The increase at BP was so large that it accounted for the bulk of a 15 percent increase in refinery emissions nationwide in 2004, the highest level since 2000.
The company is investigating whether it has been accurately documenting pollution, the Houston Chronicle reported on Sunday. There could be more federal fines levied against the energy giant if mistakes are found.
BP already faces a record $21.3 million fine from the U.S. Occupational Safety and Health Administration for 300 safety and health violations found at the Texas City refinery after the deadly explosion in March 2005 that also injured 170 workers.
The company reported that it released 10.25 million pounds of pollution in 2004, up from 3.3 million pounds the year before, according to EPA's Toxics Release Inventory, which tracks nearly 650 toxic chemicals released into the air, water and land.
BP cautioned that its latest pollution estimates might not be correct because of a recent change in how the plant calculates emissions.
"These were on-paper calculations not based on real measurements through valves or stacks," spokesman Neil Geary told the newspaper.
According to the EPA, the Texas City plant had more than three times the toxic pollutants as the nation's second most-polluted plant, an Exxon Mobil Corp. refinery in Baton Rouge, La.
The Texas Commission on Environmental Quality said it was too early to speculate about the accuracy of BP's reported figures. A spokesman said the difference might have been in reported emissions, not actual emissions.
But the Environmental Integrity Project, a Washington-D.C. based advocacy group, said the increase shouldn't be dismissed as merely an increase on paper.
"It's real; it just never got reported before," said Eric Shaeffer, a former EPA staffer and the organization's founder. "You can argue that it's not an increase, but the next sentence has to be, 'We've always been bad.'"
Most of the increase in pollution was from formaldehyde and ammonia, which can form smog and soot and irritate the eyes, nose and throat.
BP says that when all pollution is taken into account, emissions from its Texas City plant have dropped 40 percent since 2000.
Before last year's explosion, the refinery processed up to 460,000 barrels of crude oil a day and 3 percent of the nation's gasoline.
BP still faces criticism for management lapses that may have contributed to last year's explosion. The company faces a possible Justice Department investigation and is dealing with victims' lawsuits.
Copyright © 2006 The Associated Press