The dispersant is reported to be a flammable liquid. The proximity of the spray plume to the engine exhaust in this photo is interesting. Presumably the heat from the engines is insufficient to ignite the dispersant or affect the effectiveness of the plume but, from a FMECA perspective, would an engine fire while spraying present an additional safety issue over and above the obvious undesirability of an engine failure?
This kind of scenario springs to mind but could the outcome be worse given the location of the spray nozzles on the 727 compared with the fuel dump outlet on the F111?
http://youtu.be/WpPEdOMSIgQ