There have been experiments with laying hens divided into 4 groups which receive rations with different amounts of lead and cadmium. The amount and distribution of the two toxic elements in the egg components have been studied and the environmental risk for human food use has been assessed. Two new criteria defining the chemical heterogeneity of the biosphere at sub-organismal level have been devised: Clark of distribution and Clark of safety. These criteria are proposed to increase the effectiveness of management. Disparities in the distribution of the tested elements in the egg white, egg yolk and shell and the degree of safety for human health have been found. | New criteria for chemical heterogeneity of the biosphere 2. distribution of cadmium and lead in the egg of hens
