Andrew Blackwell&rsquos choice of places to visit, chronicled in his book Visit Sunny Chernobyl and Other Adventures in the World&rsquos Most Polluted Places, to quote a friend, is &ldquoplurally depressing&rdquo Chernobyl, the oil sands of Alberta, Port Arthur in Texas, the Pacific Garbage Patch and the sorry saga of the Yamuna, river-turned-sewer.