Teeth contain detailed records of lead contamination in humans and other primates

Lead is a powerful toxin. It can affect almost every organ and system in the body, and babies are extremely vulnerable to its harmful effects. Infants’ brains grow rapidly during the first year of life, and even low levels of lead exposure have been associated with brain development deficits.

It’s also more common than you might think. Many popular baby foods and infant formulas available in the US were recently found to contain elevated levels of lead and other heavy metals.

Few studies have examined Australian-sourced infant formulas and foods, and those that have show lead levels are generally low. However, more than half of the products sold in Australia are imported — so international problems are still a concern.

Lead leaves traces in growing teeth. In a new study published in BioEssays, we used a very sensitive technique called laser-ablation mapping to analyse the teeth of young macaque monkeys. We found traces of lead from both commercial infant formula and the milk of their own mothers. This provided clues of events that happened years, or even decades, earlier.

The stories teeth tell

The development of teeth records each day of our childhoods, including birth, as well as the chemistry of the food and water we consume. Public health specialists in Australia and the US have worked out how to measure infants’ metal intake using the concentrations of different elements and growth lines in teeth.

Our team honed this analytical model through a 2013 study of human, monkey, and Neanderthal nursing histories. We tracked changes in the trace element barium, which is stored in bones and teeth, and concentrated in calcium-rich milk. While barium is toxic in large amounts or certain compounds, small amounts in milk and foods like Brazil nuts do not seem to be particularly harmful.

In our new study we were able to show a precise correspondence between the onset of suckling and elevated lead levels, which disappeared when the macaque infants stopped consuming Enfamil formula or mothers’ milk. Captive monkey mothers may be exposed to lead from water pipes or old paint, as lead was once a widely used paint additive that has a pleasant sweet taste.

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