From what I’ve seen and heard the answer with lead is an unequivocal no - once lead exposure has occurred, the damage is done. It’s compounding and irreversible.

Take a look at the link, it's relevant to your question. As mentioned there, your body stores lead in your bones, which leeches into your blood stream. Because there does not appear to be a minimum safe threshold of exposure, even small exposure can, over time, lead to problems as the lead is circulated through your body, as mentioned in the quote. Sorry it doesn't appear clear when taken out of context.

One of the things that makes lead (and all heavy metals) so dangerous is the body lacks a mechanism to effectively clear it.

So if the only factor in aggression is the amount of lead in the body, then we would have to assume it takes time for the symptoms to subside as well.

typically the problem with heavy metal poisoning (lead, arsenic, etc) is that the body has difficulty getting rid of it, so it accumulates.

This can also be seen in big fish such as Tuna, which eat lots of small fish (which have consumed various heavy metals) and live for many years.