"I was surprised that the mercury was everywhere and in measurable amounts"
Gee, I have been avoiding products comging from China because they all have a high mercury and lead content, just from the air and so on where they are manufactured. Things like COFFEE MUGS are bad, as they will leach into your drink and body. [and have you found a coffee mug NOT made in china lately? - I try, and cannot find them]
Now we know that this is true in North America too, likely not as bad as in China. They say it is 'from the air', in that air pollution has put mercury there. What industrial operation here does more of that than any other? - our enemy the coal-fired power plants. I say "Shut em down" if they cannot stop the mercury and CO2.
Mercury - a neurotoxin - might be responsible for much of the modern plague of early dementia, immune disorders, and chronic pain conditions.