Contamination in packaged foods.

According to a manager at a Trade Joe's, much of the frozen and packaged food on their shelves has been around for a few months before stocking onto their shelves. She said I could also call the customer service line and cite a specific lot number to find out when it was packaged.

So this got me thinking about the next few months to years, if the packaged food now is "clean" because it's components were harvested before the fallout's arrival, what about the packaged food going to be purchased within the next few months to a year?

Should we switch to only Southern Hemisphere whole foods after some time? And then maybe after a year or two switch to fresh foods?