Chemicals are the basis of life, but some anthropogenic organic chemicals pose inherent dangers. Pesticides, industrial chemicals, pharmaceuticals, and other synthetic chemicals can enter the environment and the food chain, causing unwanted effects and disease. Medical research indicates that as much as two-thirds of chronic human disease risk cannot be explained by genetics alone and may result from the environment or gene-environment interactions (1). Furthermore, the Lancet Commission on Pollution and Health has estimated that 16% of global premature deaths are linked to pollution (2). These statistics highlight the need for research to elucidate the complex links among exposure to chemicals, environmental quality, and health.
Concentrations of many legacy chemicals are decreasing after national and international actions led to near-global phase-out of these chemicals (3). However, the number of new chemicals is rising, with the Chemical Abstract Service Registry growing from 20 million to 156 million chemicals between 2002 and 2019. Regulation of problematic chemicals can take decades; once enacted, such rules can lead to chemical substitutions that are less well characterized. There have been several cases in which the replacement chemical had properties, including toxicity, similar to those of the chemical it was intended to replace. Notable examples include plasticizers, flame retardants, chlorinated paraffins, and polyfluoroalkyl substances.
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