Truth be told, a huge portion of the spinach pulled from the market was...
...safe all along.
I'll say it again: I had a conversation with the regional produce manager of a large, national supermarket chain and he said he refuses to eat any produce that grows low to the ground, if it is grown in Mexico.
He is suspicious of the cleanliness of the water that is used to irrigate the fields in Mexico. They do not have stringent controls, and don't have proper facilities for the farm workers to use when they need a restroom.
Now we find that the impurities can be absorbed into the plant itself.
Michael