"You have a different climate in regulatory enforcement in Louisiana and Texas than you do in California, and those refineries in California are profitable," said Eric Schaeffer, director of the Environmental Integrity Project.

Environmental Integrity Project is a nonprofit organization that pushes for more effective enforcement of environmental laws.

Refineries are required to report pollution exceeding levels beyond what their operating permits allow to state environmental agencies, which enforce US regulations under EPA supervision.

A spokeswoman for the Texas pollution regulation agency declined to discuss the report.

"As a matter of policy, we don't comment on outside reports," said Lisa Wheeler of the Texas Commission on Environmental Quality.

A spokesman for the Louisiana Department of Environmental Quality said reports like the one produced by the Environmental Integrity Project help to focus attention on pollution.

"I'm glad that they've made it clear refineries are a classic source of pollution," said Chris Roberie, administrator of air quality assessment for Louisiana DEQ.

The refinery with the worse pollution level was BP Plc.'s Texas refinery, where a 2005 accident claimed the lives of 15 workers.

The BP refinery won the top spot for pollution because it reported the release of 2 million pounds of formaldehyde into the air.