It is taken for granted that medical technologies will advance apace in the future, permitting rapid healing and perhaps even shaping of the human body. This submission is to provide possible flavors for that medicine to come in.
As they travel they notice a horrible rotten smell. As they travel it gets stronger and stronger forcing them to cover their noses and mouth less they choke on the horrible smell. Stream full of dead fish. Spawning trout die in mass quantities after they spawn littering areas with dead fish dying and deteriorating in the sun.