It is hard to tell if someone goes from 140 IQ to 135. Lead can be absorbed into the body via inhalation or ingestion. It is not readily absorbed through the skin, but skin contamination can easily be transferred to the mouth and ingested. The bones act as lead repositories, accumulating lead at the time of exposure and then slowly releasing it over time. Thus lead is a cumulative poison.
Conservators represent a population with an odd mode of exposure.
Typical examples are working on lead artifacts, particularly corroded lead, and removing old linings or patches from a painting that have been adhered with lead white paint. We also use lead weights. The same results would, no doubt, apply to our use of lead as weights in treatments and as counterweights in display cases. The study showed that both oxidized and freshly cleaned lead generate lead dust. The article states a single coating of polyurethane on the lead reduced the amount of lead removal by three orders of magnitude.