A new
paper in
Canadian Medical Association Journal has linked irregular heartbeats in 322 Chinese cities to small-micron particulate matter, invisible pollution that needs an electron microscope to visualize. Given its minute size, PM
2.5 is one-fourth the size of real pollution, PM10, there is four times as much of it, so the paper could have used PM
10 and achieved the same statistical significance. It just would have been less dramatic