What are heavy metals and why are they in baby food?

There are several reasons arsenic, cadmium, lead, and mercury have been found in baby food. One of the reasons is bad manufacturing practices by the manufacturers. Bad sourcing practices—where the companies get their ingredients—can also adversely affect the amount of heavy metals in baby food products. Also, the decisions made by the manufacturers themselves on which ingredients they put in their baby food affect how dangerous their products are for children. Some ingredients added into baby food, like pre-mixed minerals, are extremely high in heavy metals.