air
atmosphere
chemical
chimney
climate
cloud
co2
contaminate
contamination
dirty
eco
ecological
ecology
emission
emissions
emit
environment
environmental
exhaust
factory
fog
fumes
harmful
industrial
industry
manufacture
manufacturing
nature
ozone
plant
pollutant
pollute
polluting
pollution
refinery
single
sky
smog
smoke
smokestack
stack
steam
technology
toxic
tree
urban
vapor
warming
waste
working