Stock photography, photos: Clean air polluted by a smoke stack Stock photos of Photographed 2004 Oulu,Finland,Scandinavia,Europe Photograph: © Reino Hanninen Click for a larger image and more information Keywords associated with this stock photo: sky,air,clean,fresh,pure,blue,white,cloud,soft,pollute,defilement,polluter,industry,heating,global,warming,quality,evironment,environmental,environmentalism,symbol,symbolic,symbolism,chimney,smoke,1,one,solitary,lone,concept,nature,conservation,protection,effect,conservancy,contradiction,industrial,conflict,clear,greenhouse,ecology,ecological,metaphor,emission,pollutant,gas,weather,atmosphere,polluting,smokestack,stack,contrast,simple,energy,production,danger,atmospheric,co2,carbon,dioxide,concern,threat,Finland,Europe,sunny,sunshine,day,daytime,outside,outdoors,winter,wintertime,concept