Impressionist paintings are frequently characterized by the hazy, cloudy look of their landscapes, and in the case of Monet, by the fog that seems to hang eternally over the London that he so loved to paint. It’s all very pretty on the canvas, but a new exhibition at the Art Gallery of Ontario makes the case that what Monet and others were really showing us was the horrific environmental effects of the Industrial Revolution on the great cities of Europe. That’s not fog hanging over London, it’s smog. And those pretty pink clouds? Coal gas and industrial waste.