Fig. 2.

The life cycle of a xenobiotic: this figure partly illustrates the circulation, transformations, and effects of pesticides in humans and the environment. These substances can enhance crop protection, thereby increasing the yield of healthy foods. However, they can also contaminate soil and water meaning that they can find their way into non-target organisms, including humans. Moreover, upon exposure to pesticides humans usually generate and excrete pesticide metabolites into the environment, which can also contaminate soil and aquatic environments. Some of these metabolites, and their microbial degradation products have been isolated from water and food samples, showing that they can re-enter the human food chain [15, 16, 21]. This cycle is applicable to other types of xenobiotics, including pharmaceuticals, and personal care products, among others