what the hell is corexit

8/7/2019 What the Hell is Corexit

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What the Hell Is Corexit?

Monday, March 28, 2011

Corexit, the chemical dispersant being used by BP to break up its massive and growingoil spill, is not the cause of physical symptoms among cleanup workers, says the

product's manufacturer, Nalco.

Several news sources, including the NYT, are reporting today that the Naperville, Illinois-

based company is defending the safety of Corexit, "when used as directed," althoughNalco advises that BP's direct application of Corexit to the spewing oil well is

"unprecedented." The Naperville Sun Times says that 993,000 gallons of Corexit have

been sprayed or dumped in the Gulf of Mexico as of yesterday. In May, the EPA askedBP to back off on its use of Corexit in the Gulf spill.

So what's in Corexit? It's hard to know exactly, because part of the formula is proprietary.

According to the material safety datasheet for Corexit 9500, the "clear, hazy, amber"

liquid contains

10%-30% hydrotreated light petroleum distillates (a mineral spirit-type solvent, as

far as I can tell);


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1%-5% propylene glycol (a widely used solvent and chemical cousin of ethylene

glycol); and

10%-30% "organic sulfonic acid salt," which is proprietary (the EPA evidentlyhas the full formula, according to the NYT).

For humans, Corexit appears to be merely a short-term irritant; it is not defined ashazardous or toxic by EPA standards. Safety precautions (eg, gloves, splash goggles) are

intended to keep the product away from the skin and eyes. Filter masks are recommendedwhen air concentrations are expected to reach a certain threshold.

Today's PubMed search for "Corexit" returns 59 articles, dating back to 1974. No article

pertains to human safety, and 37 articles concern the product's effect on sea life. A

search for "Corexit 9500" returns 22 articles, dating back to 1996; 12 pertain to animal orplant effects.

The upshot Products like Corexit 9500 are very effective oil dispersants, but they may

increase (at least temporarily) the concentrations of toxic polycylic aromatichydrocarbons (PAH) in oil-contaminated water, presumably through their dispersant

effects. And there are evidently A TONof variables to consider when deciding to use

dispersants, like, the concentration of the crude oil, the "weathered" condition of the oil,

water salinity, oil-exposure conditions (eg, whether declining or continuous), and themyriad, myriad, myriad species at risk and their life cycles.

Singer et al (1996). Comparison of acute aquatic effects of the oil dispersant Corexit

9500 with those of other Corexit series dispersants. Corexit 9500 was found to be

similarly "toxic" to other Corexit products on early-life stages of the red abalone and kelpforest mysid. The authors, from the University of California, Santa Cruz, wrote that

Corexit 9500 is a "reformulation of a long-time industry 'standard,' Corexit 9527, to allowuse on higher viscosity oils and emulsions."

George-Ares and Clark (2000). Aquatic toxicity of two Corexit dispersants. Two Exxon

employees described the in-vitro "low to moderate toxicity" of Corexit 9500 and Corexit

9527 on "most aquatic species." They also described the variables affecting toxicity (such

as species, life stage, duration of exposure, and temperature) and addressedenvironmental factors that inform the use of dispersants.

Pollino and Holloway (2002). The toxicity of testing of crude oil and related compounds

using early life stages of the crimson-spotted rainbowfish (Melantotaenia fluviatilis).

Australian academicians determined that Corexit 9500 and Corexit 9527 wereless acutely toxic than naphthalene and crude oil-water-dispersant mixtures on the larvae

of freshwater rainbowish.


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Ramachandran et al (2004). Oil dispersant increases PAH uptake by fish exposed to

crude oil. Canadian researchers concluded that the use of dispersants, like Corexit 9500,

actually increases the exposure of fish to toxic crude-oil hydrocarbons.

Fuller et al (2004). Comparative toxicity of oil, dispersant, and oil plus dispersant to

several marine species. Scientists at Texas A&M observed that crude oil with dispersantwas equally or less toxic that crude oil alone on 2 fish and 1 shrimp species.

"Unweathered" crude oil (dominated by "soluble hydrocarbon fractions") was more toxicthan weathered oil (which was dominated by "colloidal oil fractions"). In declining

exposure conditions, weathered and unweathered oil with dispersant were equally toxic to

a standardly tested fish species, Menidia beryllina. Both media were dominated by theless toxic "colloidal oil fractions." The consistent finding in this variable-results study:

declining-exposure conditions were less toxic than continuous-exposure conditions.

Couillard et al (2005). Effect of dispersant on the composition of the water-

accommodated fraction of crude oil and its toxicity to larval marine fish. Researchers

from the Canadian Department of Fisheries and Oceans concluded that Corexit 9500,when added to seawater-accommodated fractions of light crude oil, multiplied the

concentrations of PAH and was associated with higher mortality rates in larvalmummichog.

Liu et al (2006). Field investigation on the toxicity of Alaska North Slope crude oil

(ANSC) and dispersed ANSC crude to Gulf killifish, Eastern oyster and white shrimp.

Investigators at Louisiana State University found that Corexit 9500 was an effective oildispersant and facilitated the rapid reduction of hydrocarbon concentrations. At testing

conditions, most of the tested juvenile organisms (>83%) survived "well" after 24 hours

of exposure. A crude oil concentration higher than 30 ppm was required for "any

significant toxic effect."

Ramachandran et al (2006). Influence of salinity and fish species on PAH uptake from

dispersed crude oil. Water salinity reduced PAH exposure (by reducing PAH

solubility) and the efficiency of dispersants (but only at the highest tested salinity). TheCanadian authors concluded that the risk of PAH exposure from dispersed oil will be

greatest where salinity is lowestthat is, in coastal waters.

Anderson et al (2009). Preliminary investigation of the effects of dispersed Prudhoe Bay

Crude Oil on developing topsmelt embryos, Atherinops affinis. Again, Corexit 9500increased the hydrocarbon concentrations in water-accommodated oil fractions and this

effect appeared to adversely affect the survival of topsmelt embryos, according to

researchers of the University of California, Davis.

Jung et al (2009). Biochemical changes in rockfish, Sebastes schlegeli, exposed todispersed crude oil. Korean investigators confirmed that oil dispersants, like Corexit

9500, increase the exposure of fish to oil hydrocarbons.


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Lin et al (2009). Characterization of the metabolic actions of crude versus dispersed oil in

salmon smolts via NMR-based metabolomics. Taiwanese scientists concluded that

"dispersant treatment significantly decreased the lethal potency of crude oil to salmonsmolts," and described several variable metabolic effects that may be useful for

monitoring sublethal actions of dispersed oil on fish.

Duarte et al (2010). Acute effects of chemically dispersed crude oil on gill ion regulation,

plasma ion levels and haematological parameters in tambaqui (Colossoma macropomum).Investigators in the Amazon reported that chemically dispersed crude oil impairs gill

function (ie, ion regulation) in tambaqui to a greater extent than untreated crude oil or

Corexit 9500 alone.

Video still of burning Deepwater Horizon rig from,,YouTube: ,http://www.youtube.com/deepwaterhorizonjic#p/a/f/2/0R-dCXp3XJI

06/07/10 addendum: BP's use of 1 million or so gallons of dispersant may also confound

the cleanup effort in the Gulf. It's certainly to BP's advantage to obscure the scope of thespill, and Admiral Thad Allen of the Coast Guard says that dispersants "have succeeded

at fragmenting one giant spill into 'hundreds of thousands' of mini spills," reports today's

Politics Daily. BP's use of dispersant directly on the wellhead is also likely to prevent

crude oil from rising to the surface, where it is easier to spot and clean up.

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