acid
air
backlit
cancer
chemical
chemicals
chimney
cloud
clouds
contaminate
contamination
damage
danger
destruction
dirty
dust
ecology
emission
energy
environment
environmental
factory
fume
future
generate
global
greenhouse effect
hell
industrial
industry
ozone
poison
pollute
polluting
pollution
rain
silhouette
sky
smog
smoke
smokestack
smokestacks
steam
thick
toxic
vapor
warming
waste