Environmental distribution of heavy metals on Nauru, Central Pacific, and possible relationships to human health.

Nauru island, near the equator in the central Pacific Ocean, has been mined for phosphate since 1907 and over 80 million tonnes of phosphate have been exported to Australia, NZ, Britain and other overseas markets. Although superphosphate, prepared from the Nauru rock phosphate has considerable value as an agricultural nutrient, it also contains high concentrations of the toxic metal cadmium. Nauru phosphate deposits have a cadmium content between 100 and 1,000 times the average lithosphere concentration. Stockpiled topsoil contains up to 353 parts per million (ppm) cadmium and calcination dumpsite sediments are elevated to 1,177 ppm Cd. Kasava grown in the topsoil contains an average of 0.27 ppm Cd (root), 0.17 Cd (leaf) and 7.8 ppm Cd (skin) and three coconut flesh samples contained cadmium loads (average = 0.17 ppm) that exceeded the recognised maximum recommended level for consumption. Cadmium concentrations were also high in processing plant dusts (up to 150 ppm) and waters samples (up to 150 ppb) collected from around the island.