The reality is that unburned hydrocarbons are a major source of air
pollution. The occasional fuel dump will not have a huge effect on the
environment, but it is still better if the fuel is burned in a well-
maintained engine.

I did not say that it would be better to dump fuel rather than burn it
in the engine. Burning in the very efficient modern turbofan is a
better way to dispose of the high energy fuel, maybe the best way (just
from a chemestry point of view let alone the value of flying a plane).
I did not say there would not be an environmental impact, just that the
fuel dumped in flight is likely oxidized and would not stay in the air
or land on the ground in the form of raw fuel. I understand that fuel
dumping is very rare compared to the number of flights per year. It is
so rare that the any regulatory agencies may not be concerned about the
yearly amount of fuel dumped as compared to the overall amound of fuel
burned. The cumulative impact of automobile (gasoline) refueling vapors
being released is much greater than that due to (kerosene) fuel dumped
in flight. In addition, dumping fuel is almost always done to respond
to an urgent situation on an aircraft where the environmental cost is
outweighed by flight safety.

Aircraft engine manufacturers have made amazing strides in improved
efficiency. And still researchers are considering how to continue to
improve engines while reducing emissions. It would have been
interesting if the SUCCESS mission took measurements of fuel being
dumped in flight. If I had thought of it I would have suggested it
then. Oh well.

James