The National Wildlife Federation (NWF) and the Natural Resources Defense Council (NRDC) have urged U.S. Attorney General Eric Holder to remember that BP plc's Macondo well blowout in the Gulf of Mexico (see Daily GPI, Aug. 4) leaked a substantial amount of natural gas besides the millions of barrels of oil that got so much attention.

"There are strong scientific as well as legal reasons why the discharge of large quantities of hydrocarbon gas must not be ignored," the groups said in their letter. "The discharges included a high proportion of hydrocarbon gas that includes methane, ethane, propane, butane, pentane, etc.

"When calculated in equivalent units of weight, the magnitude of discharged oil plus gas is equal to 1.5 times the oil alone. In other words, if 4.1 million barrels [172 million gallons] of oil were discharged into U.S. waters, the total discharge in barrel of oil equivalents (oil plus gas) was actually over 6 million barrels."

In early June the U.S. Department of Justice (DOJ) launched civil and criminal investigations into the spill (see Daily GPI, June 3).

NWF's John Kostyack said DOJ needs to calculate civil penalties based on the discharge of both oil and gas. "While the public's attention has been focused mainly on oil, both the Oil Pollution Act and Clean Water Act make it clear that penalties should consider both oil and gas," he said.

Ian MacDonald, a professor of oceanography at Florida State University, said much of the released gas would have dissolved in the water before reaching the sea surface. In the water the gas can cause neurological damage and death for fish and other marine life, he said.

"Even if microbes work to degrade the hydrocarbon gases, they'll be competing for oxygen and other nutrients with microbes attacking oil," said Lisa Suatoni, a senior scientist with NRDC's oceans program. "That could significantly affect the overall degradation process."

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