Linet, who led the U.S. study, does not think the new com bined analysis strengthens the case for an EMF-cancer connec tion. All of this increase may be due to bias, she said in an interview. We ve shown in our own study that some of it has to do with who participates and who does not. You ve had this relatively consistent pattern, across different countries and across studies that were conducted in different ways, Greenland said. It s hard for me to see how selection bias would operate in the same way in all these cases.
Day stands somewhere in between.
Bias and confounding may be the main factors in operation, he said. On the other hand, Day said, an excess was seen which is very unlikely to be due to chance, and is consistent with a causal role for EMFs at these high levels. It cannot just be dismissed. Many of these things are not well-measured, Greenland observed. Traffic exhaust is one of the most controversial.