I agree with you about the first half of the movie akira, sheer low budget bliss. This film and subsequent cartoon spin-off gave birth to my obsession with all things toxic waste! I'd never seen anything at all like that when Melvin falls out the window into those barrels, you just knew you were watching a cult classic transpire before your very eyes. The fight scene in the taco restaurant is brilliant and easily the best part along with the aforementioned transformation buildup. My only gripe with the movie is that some scenes were too dark, that you couldn't quite make out what was going on.
Your obsession with toxic waste is something the both of us share. I grew up watching Toxic Crusaders and Teenage Mutant Ninja Turtles, and I'm still a sucker for anything involving slime or toxic waste.
The Toxic Avenger is one of my favorite films, and I'm a huge Troma nut, but I'm much more of a fan of the Nuke 'Em High series.