FDA
 

I no longer have a garden but still occasionally can items, for instance during Thanksgiving I will can sweet potatoes. I am meticulous about washing and peeling so that the resulting canned sweet taters are wholesome and ready for being made into pies or muffins. Apparently some commercial enterprises are not (or don't have to be) quite as compulsive and there are actually FDA permitted levels of contaminants allowed for various foods. Sweet taters are not on the chart but I can just imagine that commercial taters are not 100% pure.
Scroll down at the link for the chart.

https://www.fda.gov/food/ingredients...evels-handbook