An environmental group yesterday sued chocolate companies including Hershey and Mars for not disclosing the amount of toxic metals such as lead that are in their products, as required under California law...the American Environmental Safety Institute said research shows that dangerous levels of lead and cadmium in chocolate pose a serious health risk, especially to children...The environmental group cited Mars Inc., Hershey Foods Corp., Nestle USA Inc., Kraft Foods NorthAmerica Inc., Rocky Mountain Chocolate Factory Inc. and See's Candies Inc. for violating California's Proposition 65