Calcium carbonate is a naturally occurring mineral that is found in rocks and minerals such as calcite, aragonite, and limestone. It is commonly used in industries such as paint, paper, plastics, and rubber as a filler and pigment. The manufacturing process of calcium carbonate involves extracting the mineral from quarries or mines, crushing and grinding it into a fine powder, and then purifying it through various chemical processes.

CSPI says it might reconsider its rating if specifications for food-grade titanium dioxide in the U.S. are updated to ensure nanoparticles are minimized, and new studies are conducted to assess its capacity to cause cancer or other health problems.