I just watched the movie (https://en.wikipedia.org/wiki/Nausica%C3%A4_of_the_Valley_of_the_Wind_(film) ) and was confused about what the origin of the poison/toxic air that is so important to the plot is. They only said vaguely that humans caused it. I find this article, but it doesn't even mention that: http://nausicaa.wikia.com/wiki/Miasma
Does anyone know? Thanks.