We've been getting Corexited for a long time now

50.3 PPM is a lot and I have no doubt that it came from the Corexit 9527 which they have said they aren't using.  The thing is, most have us have been essentially Corexited for a long time because, as Nalco pointed out in their self serving explanation of components which make up Corexit, the 2-Butoxyethanol is found in common household products (albeit not usually 30 to 60% by weight like in Corexit).

From Wiki:

2-Butoxyethanol is a solvent in paints and surface coatings, as well as cleaning products and inks. Other products that contain 2-butoxyethanol include acrylic resin formulations, asphalt release agents, firefighting foam, leather protectors, oil spill dispersants, bowling pin and lane degreaser, and photographic strip solutions. Other products containing 2-butoxyethanol as a primary ingredient include some whiteboard cleaners, liquid soaps, cosmetics, dry cleaning solutions, lacquers, varnishes, herbicides, and latex paints.

2-Butoxyethanol is frequently found in popular cleaning products. It provides cleaning power and the characteristic odor of Windex and other glass cleaners. It is the main ingredient of many home, commercial and industrial cleaning solutions, such as Simple Green All-Purpose Cleaner.

I wonder how many have been fooled by that name "Simple Green"?