[2008] The Difference Between Ingested and Injected Aluminum
So only 1 percent of ingested aluminum is absorbed.
Now let's look at the amount of aluminum babies consume:
"Breast milk contains 40mcg/L aluminum, milk-based formulas contain ~225mcg/L, and soy-based formulas contain ~500mcg/L."
1% of each of those amounts equals .4 mcg, 2.25 mcg, and 5 mcg. So their kidneys only have to filter about .4 to 5mcg of aluminum from daily milk/formula consumption.
However, 100% of injected aluminum has to be filtered by the kidneys. So, the amount of aluminum in vaccines is not just 'a drop in the bucket' compared to consumed aluminum.
.4 mcg - 5 mcg of aluminum from food sources pales in comparison to the 295 - 1225 mcg a child could receive in one day from vaccines (The exact amount depends on the brands given).