title: Lead contamination in cocoa and cocoa products: isotopic evidence of global contamination.
abstract: In this article we present lead concentrations and isotopic compositions from analyses of cocoa beans, their shells, and soils from six Nigerian cocoa farms, and analyses of manufactured cocoa and chocolate products. The average lead concentration of cocoa beans was </= 0.5 ng/g, which is one of the lowest reported values for a natural food. In contrast, lead concentrations of manufactured cocoa and chocolate products were as high as 230 and 70 ng/g, respectively, which are consistent with market-basket surveys that have repeatedly listed lead concentrations in chocolate products among the highest reported for all foods. One source of contamination of the finished products is tentatively attributed to atmospheric emissions of leaded gasoline, which is still being used in Nigeria. Because of the high capacity of cocoa bean shells to adsorb lead, contamination from leaded gasoline emissions may occur during the fermentation and sun-drying of unshelled beans at cocoa farms. This mechanism is supported by similarities in lead isotopic compositions of cocoa bean shells from the different farms (206Pb/207Pb = 1.1548-1.1581; 208Pb/207Pb = 2.4344-2.4394) with those of finished cocoa products (206Pb/207Pb = 1.1475-1.1977; 208Pb/207Pb = 2.4234-2.4673). However, the much higher lead concentrations and larger variability in lead isotopic composition of finished cocoa products, which falls within the global range of industrial lead aerosols, indicate that most contamination occurs during shipping and/or processing of the cocoa beans and the manufacture of cocoa and chocolate products.
authors.affiliation: Environmental Toxicology, WIGS,University of California, Santa Cruz, California, USA. rankin@etox.ucsc.edu
authors.forename: Charley W
authors.initials: CW
authors.lastname: Rankin
authors.forename: Jerome O
authors.initials: JO
authors.lastname: Nriagu
authors.forename: Jugdeep K
authors.initials: JK
authors.lastname: Aggarwal
authors.forename: Toyin A
authors.initials: TA
authors.lastname: Arowolo
authors.forename: Kola
authors.initials: K
authors.lastname: Adebayo
authors.forename: A Russell
authors.initials: AR
authors.lastname: Flegal
mesh_terms: D002099:Cacao / Q000737:chemistry*; D007554:Isotopes; D007854:Lead / Q000032:analysis*; D009549:Nigeria; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D007554:Isotopes; D012989:Soil Pollutants; D007854:Lead