The Internet is swirling  with  rumors  today that a gloppy mixture of oil and Corexit (the primary dispersant used in the BP disaster) is raining down on Louisiana. Evidence is thin, and based almost entirely on the video below, but we have to wonder--is this even possible?
The notoriously unreliable  European Union Times  claims that a report prepared for Russian President Dmitry Medvedev by the country's Ministry of Natural Resources warns of a toxic rain from the dispersant and oil mixture. The EU Times explains:
When combined with the heating Gulf of Mexico waters, [Corexit's] molecules will be able to "phase transition”  from their present liquid to a gaseous state allowing them to be absorbed into clouds and allowing their release as toxic rain upon all of Eastern North America. Even worse, should a Katrina like tropical hurricane form in the Gulf of Mexico while tens of millions of gallons of Corexit 9500 are sitting on, or near, its surface, the resulting toxic rain falling upon the North American continent could theoretically destroy all microbial life to any depth it reaches
There are no linked sources in the EU Times article, however. And as far as we can tell, the claim is only bolstered by other questionable sources. Prison Planet  reports, for example, that "The Gulf of Mexico is heating up as summer progresses. Oil and Corexit 9500 are going through a molecular transition, changing from a liquid to a gas and then absorbed by clouds and released as toxic rain. Oil in the environment is toxic at 11 PPM (parts per million). Corexit 9500 is toxic at only 2.61 PPM." But again, no sources are listed.
We contacted the EPA for a comment on the possibility, but so far we haven't received a definitive answer. An EPA media representative did point us to this article from Tampa Bay's 10Connects news site, which quotes National Weather Servce Science and Operations Officer Charlie Paxton. According to Paxton, black rain isn't possible since oil doesn't evaporate. It is possible, however for rain to mix with other particles--perhaps including Corexit. And water spouts can pick up oil and carry it for short distances.
But chances are the video (above) of an oil/Corexit mixture showing up 45 miles off the Gulf of Mexico is fake. That's not to say that BP should continue using Corexit--the dispersant is carcinogenic--but for now, at least, it seems unlikely that Corexit will rain down on our heads.
Update: The EPA sent us this statement: "EPA has no data, information or scientific basis that suggests that oil mixed with dispersant could possibly evaporate from the Gulf into the water cycle." But one of our readers points us to a report  (PDF) from the former Minerals Management Service claiming that lighter crude oils can evaporate. So it might be possible that oil is mixing with rain.
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