I never thought about using shopping bags ... lead could be present because of the printing on them ... some inks have lead in them ... I would think that is no longer so but if they are made off shore it might be true ... but the so called "smart pots" really do work ... a friend here locally started using smart pots and took some pics of the roots ... holy snikes they did make a big difference ... they don't appear to be that outrageously expensive ... so you might be better off ordering them rather than the shopping bags ... but still I may get one and give it a go ... I am using plastic 3 gal bags now ... I plan to get some smart pots for the next batch ... I have also thought about using cheap 3 gal plastic waste baskets with holes drilled in them then lined with landscape fabric .. that would eliminate having to wash the smart pots ...