acid rain
air
area
bad
car
carbon dioxide
chimney
city
co2
concept
contamination
design
dirty
disaster
emissions
environment
factory
flat
graphic
greenhouse gas
harmful
hazard
heavy
house
illustration
industry
man
mask
outdoor
people
poisonous
pollutant
pollution
problem
protection
question
releasing
serious
smoke
social issue
suffering
tree
trouble
truck
umbrella
unhealthy
vector
vehicle
walking