Several groups of CECs are of particular concern because of their high rates of human usage, and because some can exert biological effects on nontarget organisms similar to the mode of action for which they were designed. We recognize that this working definition is narrower than that used, for example, by the US Environmental Protection Agency EPA and most notably excludes nanomaterials and some persistent organic pollutants. However, the diversity of CECs within and beyond our working definition requires exclusions to retain a focused review.
Some of these compounds are not completely removed by wastewater treatment processes; once they enter the receiving environment, they degrade slowly in water, sediment, and biofilms Heberer ; Bolong et al. Contaminants of emerging concern also enter aquatic environments from landfill leachates, surface runoff, atmospheric deposition, and application of biosolids and manure to agricultural land Pal et al. After CECs are released, their distribution in the environment can be related to their physicochemical properties e.
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Some CECs such as flame retardants are transported long range, which results in a global distribution even in remote regions Liu and Wong ; Aus der Beek et al. Contaminants of emerging concern can be transformed by biotic i. Studies are mostly devoted to lethal and sublethal effects of CECs at the individual level, with limited information on how these effects cascade through the food web via either direct or indirect effects.
Very few investigations have focused on the effects of CECs on food webs, although clear detriment has been shown in an experimental lake with a synthetic estrogen Kidd et al.