Aquatic Ecosystems: Harbingers of Endocrine Disruption

In the 1950s, top predator wildlife populations in aquatic systems signaled disturbances in their environment through a series of adverse health effects. Bioaccumulation in plant and animal tissue, with accompanying biomagnification in the animals that consumed these tissues, led to extremely high concentrations of some synthetic chemicals in top predator species in aquatic trophic systems. By the late 1960s technological improvements in analytical chemistry allowed for associations between a suite of persistent chemicals in the tissues of affected animals and the health status of wildlife populations. This group of contaminants, the organochlorine chemicals, and their effects on wildlife provided the insight into the phenomenon called “endocrine disruption,” where certain synthetic chemicals can interfere with the natural chemical messengers that control normal development and function. Because the effects were most often expressed in offspring that were exposed via maternal transfer before, or soon after, birth or hatching, the damage in wildlife was often overlooked. Forensic field research over the past decade has revealed far wider damage than heretofore had been realized. In addition, interest in chemicals that can interfere with the endocrine system has expanded to include natural plant and animal compounds, nonhalogenated compounds, and other large-volume chemicals (>4.5 × 106 kg/yr) that had been considered benign until only recently. Concern about the effects of contaminants in wildlife and their implications for human health led to the discovery that human offspring are experiencing developmental and neurological damage. These effects have been associated with exposure to certain organochlorine chemicals and their co-contaminants at, or slightly above, ambient concentrations in the industrialized world.