Which Micropollutants in Water Environments Deserve More Attention Globally?

Abstract

Increasing chemical pollution of aquatic environments is a growing concern with global relevance. A large number of organic chemicals are termed as “micropollutants” due to their low concentrations, and long-term exposure to micropollutants may pose considerable risks to aquatic organisms and human health. In recent decades, numerous treatment methods and technologies have been proposed to remove micropollutants in water, and typically several micropollutants were chosen as target pollutants to evaluate removal efficiencies. However, it is often unclear whether their toxicity and occurrence levels and frequencies enable them to contribute significantly to the overall chemical pollution in global aquatic environments. This review intends to answer an important lingering question: Which micropollutants or class of micropollutants deserve more attention globally and should be removed with higher priority? Different risk-based prioritization approaches were used to address this question. The risk quotient (RQ) method was found to be a feasible approach to prioritize micropollutants in a large scale due to its relatively simple assessment procedure and extensive use. A total of 83 prioritization case studies using the RQ method in the past decade were compiled, and 473 compounds that were selected by screening 3466 compounds of three broad classes (pharmaceuticals and personal care products (PPCPs), pesticides, and industrial chemicals) were found to have risks (RQ > 0.01). To determine the micropollutants of global importance, we propose an overall risk surrogate, that is, the weighted average risk quotient (WARQ). The WARQ integrates the risk intensity and frequency of micropollutants in global aquatic environments to achieve a more comprehensive priority determination. Through metadata analysis, we recommend a ranked list of 53 micropollutants, including 36 PPCPs (e.g., sulfamethoxazole and ibuprofen), seven pesticides (e.g., heptachlor and diazinon), and 10 industrial chemicals (e.g., perfluorooctanesulfonic acid and 4-nonylphenol) for risk management and remediation efforts. One caveat is that the ranked list of global importance does not consider transformation products of micropollutants (including disinfection byproducts) and new forms of pollutants (including antibiotic resistance genes and microplastics), and this list of global importance may not be directly applicable to a specific region or country. Also, it needs mentioning that there might be no best answer toward this question, and hopefully this review can act as a small step toward a better answer.

Antibiotics in global rivers

“…The weighted frequency of RQ (WFRQ) for a specific antibiotic was proposed as a risk surrogate for the prioritization of antibiotics, which was calculated using the method modified from Yang et al [71] (eq. ( 1)).…”

“…where F x the fraction of RQ data numbers of rank class x in the total RQ numbers for a specific antibiotic (i.e., the frequency of rank class x), and x was assigned of 1 for high risk (RQ>1), 2 for medium risk (0.1<RQ<1), 3 for low risk (0.01<RQ<0.1), or 4 for insignificant risk (RQ<0.01). W x is the weighting index, which was assigned of 1 for high, 0.5 for medium, 0.25 for low, or 0 for insignificant risks, respectively [71]. F x herein was the frequency of rank class x rather than the number of data.…”

Effects of dissolved organic matter characteristics on the photosensitized degradation of pharmaceuticals in wastewater treatment wetlands

“…[1][2][3] The presence of pharmaceuticals, even at trace levels, may pose ecological risks to the aquatic environment and human health. [4][5][6] As many of these compounds are recalcitrant to conventional wastewater treatment, alternative processes are necessary to ensure their effective removal. 7,8 Advanced treatment technologies based on physical and chemical processes have been proposed to degrade organic contaminants, 9,10 but these technologies can be resource intensive to implement and maintain.…”

CNT encapsulated MnOx for an enhanced flow-through electro-Fenton process: the involvement of Mn(iv)

“…1,2 These micropollutants contain a vast category of anthropogenic compounds and are usually present in water at trace levels (ranging from ng L −1 to μg L −1 ), posing a great challenge to existing wastewater treatment systems. 3 Bisphenol A (BPA), an important monomer for synthesizing epoxy plastics and polycarbonate, frequently appears in water. 4 In aquatic environments, BPA was detected at the μg L −1 level, while its concentration in landfill leachates can reach as high as 3.5 mg L −1 .…”