As convenient as store-bought baby food is, it can pose hidden dangers for infant brains, say U.S. congressional investigators. A report issued by the House of Representatives on February 4 found “dangerous levels of toxic heavy metals,” including arsenic, lead, cadmium and mercury, in baby foods made by major companies Hain Foods, Gerber, Beech-Nut and Happy Family Organics. Walmart, Campbell Soup Company and Sprout Organic Foods refused to cooperate with the investigation. On March 5, the U.S. Food and Drug Administration pledged to enact new standards, increase inspections and testing, and support research to lower baby food contaminants.

Low levels of exposure to heavy metals can cause serious, irreversible damage to children’s brain development, studies show. Naturally present in the environment, they enter baby foods through soil, water and air; companies attempt to minimize this impact through processing. In one example, Hain Celestial, which makes Earth’s Best Organic, says it no longer uses brown rice, which can harbor arsenic.