Iron high in sample

[hookliftpete]

Everything else is normal, lead, magnesium, copper, zinc, no water, no loss that i can see in my expansion tank, truck runs mon-friday, has sat occasionally for a day or two in the last few months as work was slow. Not in position to do an in frame, but not sure what to look at for possible problems. Fuel milage has been stable, about 8.4mpg avg. i suppose it could be a contaminated sample? I was concerned when the previous sample came back at 17ppm for iron, as it had been riding in the single digits before (6-9ppm).