>"The most recent evidence from epidemiological and toxicological studies suggests that low levels of exposure can, over time, damage the heart, kidneys, and brain."
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.
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.