PHILADELPHIA (CBS) — Long viewed as healthier than other sweet treats, some kinds of dark chocolate contain potentially dangerous amounts of heavy metals, according to research released on Thursday by Consumer Reports. Scientists at the nonprofit advocacy organization recently measured the amount of heavy metals in 28 popular brands of dark chocolate bars and cadmium was found and lead in all of them. For 23 of the bars, consuming just an ounce a day would put an adult over a level for at least one of the metals that could be harmful, CR said. Five of the bars were above those levels for both cadmium and lead. Long-term exposure to even small amounts of heavy metals can lead to a slew of health issues, including developmental problems and brain development in young children, experts say. They are risks for people of any age,” Tunde Akinleye, the CR food safety researcher who led the testing, said in a statement. Frequent exposure to lead in adults can lead to nervous system problems, hypertension, immune system suppression, kidney damage and reproductive issues, he noted. Children’s clothes from popular retailers recalled over lead poisoning risk 00:19 While most of the chocolate bars tested contained concerning levels of lead, cadmium or both, five had relatively low levels of both metals, CR found. “That shows it’s possible for companies to make products with lower amounts of heavy metals — and for consumers to find safer products that they enjoy,” Akinleye said. In determining the risks for the chocolate it tested, CR used California’s maximum allowable dose level of 0.5 micrograms for lead and 4.1 micrograms for cadmium, as there are no federal limits. CR found that an ounce of Hershey’s Special Dark Mildly Sweet Chocolate contained lead 265% above what California allows, and Trader Joe’s Dark Chocolate 72% Cacao holding 192% more. A spokesperson for Hershey’s deferred to the National Confectioners Association for comment. In an emailed statement, the trade group objected to CR’s use of levels set by California, noting that the state does not set federal food safety standards. “The products cited in this study are in compliance with strict quality and safety requirements,” a spokesperson said. for the group stated in an email to CBS MoneyWatch. “Food safety and product quality remain our highest priorities and we remain dedicated to being transparent and socially responsible.” The confectioners association in August released research showing ways that lead and cadmium in chocolate could be reduced, including having cocoa farmers plant new tree stock. According to CR’s findings, the safer choices are: Mast Organic Dark Chocolate 80% Cocoa. CR found an ounce contained 14% less lead and 40% less cadmium than California’s allowable limits. Taza Chocolate Organic Deliciously Dark Chocolate 70% Cacao held 33% less lead and 74% less cadmium. Ghirardelli Intense Dark Chocolate 86% Cacao contained 36% less lead and 39% less cadmium. Ghirardelli Intense Dark Chocolate Twilight Delight. Lead contained was 61% below the allowable level and cadmium 96% beneath its allowable limit. Valrhona Abinao Dark Chocolate 85% Cacao. Lead 63% and cadmium 73% below.