Yeah, they should have ended 100LL a long long time ago. It's crazy how such a small amount can cause so many problems. Imagine what it was like back in the 60s. Utter insanity and they KNEW that it would cause problems.
Unfortunately there is growing evidence that lead stays in soils for decades or maybe centuries. I can imagine in the future that lead contamination of farmland might mean that we end up with a kinda crazy reversal - we end up growing all our food in undeveloped places like south america that never had as much lead contamination, and food from the USA and other developed countries is so lead contaminated that it gets exported to places like africa where they don't have strict regulations against contaminated food.
Undeveloped countries stopped using lead way after the USA. Lead contamination was a huge issue in Africa and the Middle East. It wasn't until 2014 that lead use in auto fuel was ended worldwide.
Luckily lead is very heavy and chemically active which makes it much easier to remove from soils than some of the nastier contaminants. You can essentially break it down with sulphur amendments to acidify the soil and then let the plants do the rest of the work. Eventually dilution does the rest of the work until it reaches background levels.
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.
