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Water contamination by emerging contaminants is increasing in the context of rising urbanization, industrialization, and agriculture production. Emerging contaminants refers to contaminants for which there is currently no regulation requiring monitoring or public reporting of their presence in our water supply or wastewaters. There are many emerging contaminants such as pesticides, pharmaceuticals, drugs, cosmetics, personal care products, surfactants, cleaning products, industrial formulations and chemicals, food additives, food packaging, metalloids, rare earth elements, nanomaterials, microplastics, and pathogens. The main sources of emerging contaminants are domestic discharges, hospital effluents, industrial wastewaters, runoff from agriculture, livestock and aquaculture, and landfill leachates. In particular, effluents from municipal wastewater treatment plants are major contributors to the presence of emerging contaminants in waters. Although many chemicals have been recently regulated as priority hazardous substances, conventional plants for wastewater and drinking water treatment were not designed to remove most emerging contaminants. Here, we review key examples of contamination in China, Portugal, Mexico, Colombia, and Brazil. Examples include persistent organic pollutants such as polychlorinated biphenyls, dibenzofurans, and polybrominated diphenyl ethers, in lake and ocean ecosystems in China; emerging contaminants such as alkylphenols, natural and synthetic estrogens, antibiotics, and antidepressants in Portuguese rivers; and pharmaceuticals, hormones, cosmetics, personal care products, and pesticides in Mexican, Brazilian, and Colombian waters. All continents are affected by these contaminants. Wastewater treatment plants should therefore be upgraded, e.g., by addition of tertiary treatment systems, to limit environmental pollution.

New dipeptides, structural analogues of known immunomodulating agents, were prepared by stereospecific condensation between 2-substituted thiazolidine-4-carboxylate esters with N-substituted L-proline or L- thiaproline. The structure of these compounds has been elucidated by combination of NMR methods and X-ray analysis. In addition, NMR measurements on dipeptides indicated the presence of S-cis and S-trans conformers around the amide bonds.