air
area
building
chemical
chimney
city
cloud
coal
construction
contamination
danger
dark
dioxide
dirty
energy
environment
environmental
factory
fog
fumes
global
grunge
impurity
industrial
industry
manufacturing
old
pipe
plant
polluted
pollution
power
problem
rain
rusty
sepia
sky
smog
smoke
steam
steel
structure
technology
tower
toxic
urban
vintage
warming
waste
water