acid
air
atmosphere
bad
blue
cancer
carbon
change
chemical
chemistry
chimney
clean
climate
cloud
co2
concept
danger
dioxide
dirty
disaster
disease
ecology
effect
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emissions
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environment
factory
fuel
gas
global
greenhouse
industrial
industry
ozone
pipe
plant
poison
pollution
power
sky
smog
smoke
steam
symbol
technology
toxic
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waste
word