Chemicals that persist in the body, i.e., are neither rapidly broken down nor excreted, are well suited to study using biomonitoring. Such persistent substances include PCBs and pesticides like DDT. The pollutants aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, polychlorinated biphenyls, dioxins, furans, and toxaphene, a group of pollutants sometimes referred to as the "dirty dozen". These compounds were the first to be targeted by the Stockholm Convention. More recently, compounds like lindane, bromodiphenyl ethers, pentachlorobenzene and PFOS have been added to the list.
The aforementioned persistent organic pollutants (POPs) are persistent in the environment as well as in the human body, which means that exposure occurs over prolonged periods of time. The concentrations of POPs found in humans are therefore often higher than those of other organic compounds, even those produced or used in higher amounts.