Fog was outdoors, hanging over the river, creeping in and out of alleyways and passages, swirling thickly between the bare trees of all the parks and gardens of the city, and indoors, too, seething through cracks and crannies like sour breath, gaining a sly entrance at every opening of a door. It was a yellow fog, a filthy, evil-smelling fog, a fog that choked and blinded, smeared and stained. Groping their way blindly across roads, men and women took their lives in their hands, stumbling along the pavements, they clutched at railings and at one another, for guidance.

Wikipedia-"London's poor air quality had been a problem since at least the 13th century." The Great Smog of London is a horror story all on its own. I feel like a lot of people don't realize how very long we've been polluting so very much.