This is a great article on the biology of lead exposure.
Unfortunately on the exposure side research wasn’t done and it propagates the myth that lead exposure is only an issue for those with lead pipes or lead paint. It’s true that these are the main sources of severe lead exposure. However the article points out that there is no safe level of exposure to lead and these aren’t the main ways we are exposed to lead in the US anymore.
Today we are mostly exposed by low level contamination and thankfully this usually results in only mildly elevated lead levels. In a toddler sticking things in the mouth this could be almost any object. For adults it is food and drinks and the objects we use to make them.
I know this because my toddler had elevated lead levels even though our neighborhood never had lead paint and our water does not have lead (I tested the water coming out of our faucets).
The US has few laws against lead contamination and they aren’t very stringent and there is little proactive enforcement. This non profit has ended up creating several recalls after reporting their own testing: https://tamararubin.com/category/recall/
Most of the recalls were products marketed for children such as baby bottles. But if a child eats off an adult plate there aren’t any laws against that being contaminated.
Some actions you can take are:
* test children’s lead levels and your own
* make sure toddlers aren't playing with old toys (pre 1978 really risky, after 2010 is best)
* stop buying things that have a prop 65 warning (I know prop 65 isn’t perfect, but it’s often a lead warning).
* Remove risky objects like the above from your children’s classrooms.
* For cooking and food and drinks use clear glass, stainless steel, and cast iron
* avoid processed foods. There are a lot of particulars here about what is most likely to be high in lead. Chocolate, spices, salt, and cassava products are particularly high in heavy metals.