Reason for warning required in California:
Analytical technology has advanced to a level of such precision that it is now possible to find traces of toxic heavy metals in virtually all foods and beverages. Of prime concern to the dietary supplement industry are lead, arsenic, cadmium and mercury. All four metals are listed in Proposition 65 and all are naturally present in foods. They cannot be avoided. They will be in foods bought at the market and consumed at home; in foods consumed at restaurants, even in vegetables you grow at home.
Just as these heavy metals are present in foods, they are consequently found in supplements made of natural materials, whether from plants or animals. And therein lies the problem for the dietary supplement industry, its retailers and consumers in California.