air
asthma
atmosphere
atmospheric
blue
carbon
chimney
clouds
concern
damage
danger
dioxide
dirty
emission
emissions
emit
emitting
environment
environmental
factory
fossil
fuel
fume
fumes
global
grunge
grungy
harm
haze
horizontal
industrial
industry
plant
pollutant
pollute
pollution
problem
refinery
sky
smog
smoke
smokestack
stack
substance
technology
thermal
threat
toxic
warming