acid rain
air
blue
cancer
chance
chemical
chemicals
chimney
climate
cloud
clouds
co2
contamination
damage
danger
destruction
dirty
dust
ecology
emission
energy
environment
environmental
factory
future
generate
get contaminated
global
greenhouse effect
industrial
industry
mill
ozone
paper
poison
pollute
polluting
pollution
sky
smog
smoke
smokestack
smokestacks
steam
thick
toxic
warming
waste