Pollution was a hot topic of discussion in the early 70's and remains one of the most significant blights in the civilized world. Because of the brouhaha over pollution in America actual real steps were taken to make the skies and the waters cleaner and they worked, a shining example of what government can do when properly motivated. Many today like to mock environmental efforts as extremist and in some instances they can seem so, but in the ruthless face of industrial pollution such extremism seems warranted. That's the situation we have in Godzilla vs. Hedorah in which an alien is able to use pollution to make a deadly giant of itself and become a serious threat to the very lives of those in Japan. This is a really hideous monster and it kills and kills and kills again.
This is a wackadoodle movie in many ways with psychedelic sequences and animated sections which to my eyes help to make the movie both visually interesting and in most cases help move the narrative. Godzilla himself appears as among the most traditional things in the movie, looking not unlike he has in previous outings. His struggles again Hedorah are potent and his burned paws reveal that he himself is susceptible to the power of the mighty sludge monster. This is also a Godzilla who seems to have little time for mankind as he watches the forces that be fail and fail again to impede the threat. Without Godzilla, who fights for reasons we don't really know, this is a threat to mankind that would have succeeded and the omnipresent naive hope of youth, the feckless ministrations of authority, or the slight insights offered by science seem enough.
Now Godzilla flies in this movie, using his atomic breath as some sort of thrust. It looks rather goofy really, but is more than accommodated by the dark threatening setting in which the final battle is waged. This ain't the relentless deadly behemoth of the original, but it's as close as the series ever gets.