Even though it is a relatively safe element when consumed in small amounts, arsenic has been shown to cause anemia in children. It can also cause liver cancer when consumed in large quantities. High levels of arsenic in baby food have been prohibited since it is believed to cause terrible illnesses.

Rice, a common ingredient in baby foods, also tends to have high levels of arsenic. Rice is grown in water, and arsenic from the soil dissolves when it comes in contact with water, he said. Because babies' brains are still developing, there is a lot of concern about how those metals could damage that development, Hansen said.