Related by context. Frequent words. (Click for all words.) 66 cleaner 60 dirty 50 polluting 50 nicer 48 quieter 47 cheaper 47 darker 47 polluted 47 fresher 46 worse 46 hotter 46 pollute 44 heavier 44 harsher 43 drier 43 greener 42 louder 42 better 42 less 42 smarter 41 colder 41 harder 41 busier 40 poorer 40 warmer 40 bigger 40 wiser 40 clean 40 happier 39 quicker 39 pollution 39 tougher 39 farther 39 lighter 39 than 39 faster 39 richer 39 sharper 39 thicker 38 smoother 38 filthy 38 tighter 38 soot 38 simpler 38 safer 38 newer 37 sweeter 37 older 37 expensive 37 fewer 36 milder 36 messy 36 Dirty 36 healthier 36 brighter 36 bolder 36 cluttered 36 slower 35 air pollution 35 fossil fuels 35 closer 35 shorter 35 stinks 35 cooler 35 freer 35 thinner 35 riskier 34 considerably 34 stronger 34 stale 34 pollutants 34 fossil fuel 34 more 34 harmful 33 emissions 33 coal fired 33 longer 33 cleaned 33 deeper 33 fitter 33 contaminated 33 greasy 33 Clean 33 nasty 33 easier 32 even 32 salty 32 steeper 32 smells 32 boring 32 smaller 32 calmer 32 degrading 32 wealthier 32 smog 32 stricter 31 suck 31 sooner 31 sucks 31 clearer 31 degraded