Quaternary ammonium compounds (QACs or “quats”) make up a class of chemicals used as disinfectants in cleaning and other consumer products. While disinfection is recommended for maintaining a safe environment during the COVID-19 pandemic, the increased use of QACs is concerning as exposure to these compounds has been associated with adverse effects on reproductive and respiratory systems. We have determined the occurrence of 19 QACs in residential dust collected before and during the COVID-19 pandemic. QACs were detected in >90% of the samples collected during the pandemic at concentrations ranging from 1.95 to 531 μg/g ( n = 40; median of 58.9 μg/g). The total QAC concentrations in these samples were significantly higher than in samples collected before the COVID-19 pandemic ( p < 0.05; n = 21; median of 36.3 μg/g). Higher QAC concentrations were found in households that generally disinfected more frequently ( p < 0.05). Disinfecting products commonly used in these homes were analyzed, and the QAC profiles in dust and in products were similar, suggesting that these products can be a significant source of QACs. Our findings indicate that indoor exposure to QACs is widespread and has increased during the pandemic.

The constant potential and constant current discharge techniques were used to determine the hydrogen diffusion coefficients in an LaNi~.~A10.v~ electrode. The values obtained were 2.97 • 10-~1 and 3.30 • 10-~1 cm2/s, respectively. The advantages and disadvantages of these two techniques are discussed.

Metabolism is an organism's primary defense against xenobiotics, yet it also increases the production of toxic metabolites. It is generally recognized that phenolic xenobiotics, a group of ubiquitous endocrine disruptors, undergo rapid phase II metabolism to generate more water-soluble glucuronide and sulfate conjugates as a detoxification pathway. However, the toxicological effects of the compounds invariably point to the phase I metabolic cytochrome P450 enzymes. Here we show that phenolic xenobiotics undergo an unknown metabolic pathway to form more lipophilic and bioactive products. In a nontargeted screening of the metabolites of a widely used antibacterial ingredient: triclosan (TCS), we identified a metabolic pathway via in vitro incubation with weever, quail, and human microsomes and in vivo exposure in mice, which generated a group of products: TCS-O-TCS. The lipophilic metabolite of TCS was frequently detected in urine samples from the general population, and TCS-O-TCS activated the constitutive androstane receptor with the binding activity about 7.2 times higher than that of the parent compound. The metabolic pathway was mediated mainly by phase I enzymes localized on the microsomes and widely observed in chlorinated phenols, phenols, and hydroxylated aromatics. The pathway was also present in different phenolic xenobiotics and formed groups of unknown pollutants in organisms (e.g., TCS-O-bisphenol A and TCS-O-benzo()pyrene), thus providing a cross-talk reaction between different phenolic pollutants during metabolic processes in organisms.

This is the first study in the last 15 years to analyze per-and polyfluoroalkyl substances (PFAS) in breast milk collected from mothers (n = 50) in the United States, and our findings indicate that both legacy and current-use PFAS now contaminate breast milk, exposing nursing infants. Breast milk was analyzed for 39 PFAS, including 9 short-chain and 30 long-chain compounds, and 16 of these PFAS were detected in 4−100% of the samples. The ∑PFAS concentration in breast milk ranged from 52.0 to 1850 pg/mL with a median concentration of 121 pg/mL. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were the most abundant PFAS in these samples (medians 30.4 and 13.9 pg/mL, respectively). Two short-chain PFAS, including perfluoro-n-hexanoic acid (PFHxA, C6) and perfluoro-nheptanoic acid (PFHpA, C7), were detected in most of the samples with median concentrations of 9.69 and 6.10 pg/mL, respectively. Analysis of the available breast milk PFAS data from around the world over the period of 1996−2019 showed that while the levels of the phased-out PFOS and PFOA have been declining with halving times of 8.1 and 17 years, respectively, the detection frequencies of current-use short-chain PFAS have been increasing with a doubling time of 4.1 years.

Despite the increasing use and discharge of novel brominated flame retardants, little information is available about their trophodynamics in the aquatic food web, and their subsequent relationships to compound metabolism. In this study, concentrations of 2,4,6-tribromophenyl allyl ether (ATE), 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), tetrabromo- o-chlorotoluene (TBCT), pentabromobenzyl acrylate (PBBA), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (TBPH), and decabromodiphenyl ethane (DBDPE) were measured in 17 species, including plankton, invertebrates, and fish from Lake Taihu, South China. Trophodynamics of the compounds were assessed, and metabolic rates were measured in the liver microsomes of crucian (trophic level [TL]: 2.93), catfish (TL: 3.86), and yellow-head catfish (TL: 4.3). Significantly positive relationships were found between trophic levels and lipid-normalized concentrations of ATE, BTBPE, and TBPH; their trophic magnification factors (TMFs) were 2.85, 2.83, and 2.42, respectively. Consistently, the three chemicals were resistant to metabolism in all fish microsomes. No significant relationship was observed for βTBECH ( p = 0.116), and DBDPE underwent trophic dilution in the food web (TMFs = 0.37, p = 0.021). Moreover, these two chemicals showed steady metabolism with incubation time in all fish microsomes. TBCT and PBBA exhibited significant trophic magnifications in the food web (TMF = 4.56, 2.01). Though different metabolic rates were observed for the two compounds among the tested fish species, TBCT and PBBA both showed metabolic resistance in high-trophic-level fish. These results indicated that metabolism of organisms at high trophic levels plays an important role in the assessment of trophic magnification potentials of these flame retardant chemicals.

Quaternary ammonium compounds (QACs) are commonly used in a variety of consumer, pharmaceutical, and medical products. In this study, bioaccumulation potentials of 18 QACs with alkyl chain lengths of C8–C18 were determined in the in vitro–in vivo extrapolation (IVIVE) model using the results of human hepatic metabolism and serum protein binding experiments. The slowest in vivo clearance rates were estimated for C12-QACs, suggesting that these compounds may preferentially build up in blood. The bioaccumulation of QACs was further confirmed by the analysis of human blood (sera) samples ( n = 222). Fifteen out of the 18 targeted QACs were detected in blood with the ΣQAC concentrations reaching up to 68.6 ng/mL. The blood samples were collected during two distinct time periods: before the outbreak of the COVID-19 pandemic (2019; n = 111) and during the pandemic (2020, n = 111). The ΣQAC concentrations were significantly higher in samples collected during the pandemic (median 6.04 ng/mL) than in those collected before (median 3.41 ng/mL). This is the first comprehensive study on the bioaccumulation and biomonitoring of the three major QAC groups and our results provide valuable information for future epidemiological, toxicological, and risk assessment studies targeting these chemicals.

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Naphthenic acids (NAs) are one class of compounds in wastewaters from petroleum industries that are known to cause toxic effects, and their removal from oilfield wastewater is an important challenge for remediation of large volumes of petrochemical effluents. The present study investigated occurrences and behaviors of total NAs and aromatic NAs in a refinery wastewater treatment plant, located in north China, which combined physicochemical and biological processes. Concentrations of total NAs were semiquantified to be 113−392 μg/L in wastewater from all the treatment units, and the percentages of aromatic NAs in total NAs was estimated to be 2.1−8.8%. The mass reduction for total NAs and aromatic NAs was 15 ± 16% and 7.5 ± 24% after the physicochemical treatment, respectively. Great mass reduction (total NAs: 65 ± 11%, aromatic NAs: 86 ± 5%) was observed in the biological treatment units, and antiestrogenic activities observed in wastewater from physicochemical treatment units disappeared in the effluent of the activated sludge system. The distributions of mass fractions of NAs demonstrated that biodegradation via activated sludge was the major mechanism for removing alicyclic NAs, aromatic NAs, and related toxicities in the plant, and the polycyclic NA congener classes were relatively recalcitrant to biodegradation, which is a complete contrast to the preferential adsorption of NAs with higher cyclicity (low Z value). Removal efficiencies of total NAs were 73 ± 17% in summer, which were higher than those in winter (53 ± 15%), and the seasonal variation was possibly due to the relatively high microbial biotransformation activities in the activated sludge system in summer (indexed by O 3 −NAs/NAs). The results of the investigations indicated that biotransformation of NA mixtures by the activated sludge system were largely affected by temperature, and employing an efficient adsorbent together with biodegradation processes would help cost-effectively remove NAs in petroleum effluents.