According to this summary, adults typically absorb up to 20% of ingested lead after a meal, whereas children typically absorb up to 50% of ingested lead after a meal.

When I search to try to find out why that is, most sites talk about how lead ingestion has a more severe effect on children than adults, due to still being in early stages of brain development (but this does not tell us why they absorb a higher percentage of lead compared to adults).

Other sites talk about behavioral reasons for increased lead absorption in children, a nice summary being here, and I have further extracted the relevant parts here:

  • Children generally ingest lead-contaminated soil and house dust at higher rates than adults because of mouthing and hand-to-mouth behaviors.
  • Children have a higher breathing rate than adults, breathing in a greater volume of air per pound.
  • Being shorter than adults, children are more likely to breathe lead-contaminated dust and soil as well as lead-containing fumes close to the ground.
  • The percent of lead absorbed in the gut, especially in an empty stomach, is estimated to be as much as 5 to 10 times greater in infants and young children than in adults [Ziegler et al. 1978 as cited in ATSDR 1999; James et al. 1985; Chamberlain et al. 1978; Alexander et al. 1974].
  • Gastrointestinal absorption of lead in children is increased by deficiencies in Ascorbate, Calcium, Iron, and Zinc [Mahaffey 1990, as cited in AAP 1993].

The first four points either tell us reasons why children absorb more lead than adults, but not the reason why children absorb more through ingestion of a meal, than adults do. The fifth point finally gives a reason for why children absorb more lead after ingestion of a meal (the reason being the lack of some substances which they claim help reduce lead absorption).

But what I found intriguing was this quote about lead absorption in children from here:

"Some of the protective mechanisms that are well developed in adults are immature in young children"

The way this sentence is constructed, gives me the feeling that they are not just talking about increased levels of things like iron and zinc in adults, since increased levels of those elements would not usually be described as a "protective mechanism". But this source did not give a citation for that sentence.

This very interesting New York Times article from 1990 said about children:

"their body mass is small so they ingest and absorb more lead per pound than adults."

But again, it would be strange to say that "being small" is a "protective mechanism" against absorption of lead.

Are there protective mechanisms against gastrointestinal lead absorption in adults (not including the presence of higher levels of ascorbate, calcium, iron and zinc) that are not yet fully developed in children? What are they?

  • ATSDR (2010) cited with your first statement states "Gastrointestinal absorption of inorganic Pb occurs primarily in the duodenum (Mushak 1991). The exact mechanisms of absorption are unknown and may involve active transport and/or diffusion through intestinal epithelial cells (transcellular) or between cells (paracellular), and may involve ionized Pb (Pb+2) and/or inorganic or organic complexes of Pb." – Chris Rogers Sep 15 '20 at 13:50
  • @ChrisRogers Thanks for adding that. It seems that a lot of years have passed since 1991 and 2010, so more might be known. Also knowing that transport is one through epithelial cells in the duodenum is helpful, but I do wonder what "protective mechanisms" adults might have there that children don't. It's also possible that the "protective mechanisms" are not in the duodenum but at a later stage, maybe allowing initial absorption but preventing further accumulation. – user1271772 Sep 15 '20 at 16:26

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