No, but our understanding of 'acceptable' lead levels keeps getting lower. One day, the amount of lead in our crops which we might today consider acceptable, in the future we might not.

Imagine if 100 years from now, Brazil is an up and coming economic powerhouse, and economists figure out that they are doing so well because their strategists, businesspeople, scientists and engineers are all smarter because their food contains less lead than ours does. We'd quickly start outlawing high lead food, which in turn might make big swathes of our cropland unusable for food.