The correlation is the ratio of the lead isotopes, which is specific for that Asien region. Lead from other sources has a different isotope ratio. (Don't have d

The correlation is the ratio of the lead isotopes, which is specific for that Asien region. Lead from other sources has a different isotope ratio. (Don't have data right now so I don't know how specific it is.) (Of course, mixing has to be taken into account when backtracking.) It is actually a pretty good argument. However, it only applies to PM2.5 lead itself, since different materials can behave very differently (chemistry etc). Also, how and where the lead came from the metal ores and coal into the air is not part of the research.