Fuel/Dispersant mixture is more toxic

This table unequivocally shows that a fuel/dispersant mixture is more toxic than either fuel or dispersant by itself. This is from the EPA website. LC50 is the Lethal Concentration that kills 50 percent of indicator species, in this case Menidia beryllina (the current EPA-approved marine vertebrate used in both acute and chronic toxicity testing.) and Mysidopsis bahia (opossum shrimp, an estuarine species suitable for life-cycle toxicity tests to determine the effect of a pollutant).


Corexit EC9500A has an LC50 of 25.20 ppm (96-hr) for Menidia beryllina and 32.23 ppm (48-hr) for Mysidopsis bahia.

No. 2 Fuel Oil has an LC50 of 10.72 ppm (96-hr) for Menidia beryllina and 16.12 ppm (48-hr) for Mysidopsis bahia.

Corexit EC9500A & No. 2 Fuel Oil (1:10) has an LC50 of 2.61 ppm (96-hr) for Menidia beryllina and 3.40 ppm (48-hr) for Mysidopsis bahia.

These results indicate that combining the dispersant with the fuel oil increases toxicity 4-10 times.

http://www.epa.gov/oem/content/ncp/products/corex950.htm