key: cord-0696521-rqqg4tyo authors: Zheng, Guomao; Schreder, Erika; Sathyanarayana, Sheela; Salamova, Amina title: The first detection of quaternary ammonium compounds in breast milk: Implications for early-life exposure date: 2022-04-18 journal: J Expo Sci Environ Epidemiol DOI: 10.1038/s41370-022-00439-4 sha: 65ce4528bf8ec056f772c8414f7aa44daae580c4 doc_id: 696521 cord_uid: rqqg4tyo BACKGROUND: Quaternary ammonium compounds (QACs), commonly used in cleaning, disinfecting, and personal care products, have recently gained worldwide attention due to the massive use of disinfectants during the COVID-19 pandemic. However, despite extensive use of these chemicals, no studies have focused on the analysis of QACs in human milk, a major route of exposure for infants. [Image: see text] OBJECTIVE: Our objectives were to identify and measure QACs in breast milk and evaluate early-life exposure to this group of compounds for nursing infants. METHODS: Eighteen QACs, including 6 benzylalkyldimethyl ammonium compounds (BACs, with alkyl chain lengths of C8-C18), 6 dialkyldimethyl ammonium compounds (DDACs, C8-C18), and 6 alkyltrimethyl ammonium compounds (ATMACs, C8-C18), were measured in breast milk samples collected from U.S. mothers. Daily lactational intake was estimated based on the determined concentrations for 0–12 month old nursing infants. RESULTS: Thirteen of the 18 QACs were detected in breast milk and 7 of them were found in more than half of the samples. The total QAC concentrations (ΣQAC) ranged from 0.33 to 7.4 ng/mL (median 1.5 ng/mL). The most abundant QAC was C14-BAC with a median concentration of 0.45 ng/mL. The highest median ΣQAC estimated daily intake (EDI) was determined for <1-month old infants based on the average (using the median concentration) and high (using the 95(th) percentile concentration) exposure scenarios (230 and 750 ng/kg body weight/day, respectively). SIGNIFICANCE: Our findings provide the first evidence of the detection of several QACs in breast milk and identify breastfeeding as an exposure pathway to QACs for nursing infants. IMPACT STATEMENT: Our findings provide the first evidence of QAC occurrence in breast milk and identify breastfeeding as one of the exposure pathways to QACs for nursing infants. Quaternary ammonium compounds (QACs) are a large group of organic substances used as disinfectants and surfactants in a range of applications, including but not limited to cleaning, disinfecting, and personal care products, pharmaceuticals, pesticides, and biomedical materials [1] . The three most well-known QAC groups include benzylalkyldimethyl ammonium compounds (BACs), dialkyldimethyl ammonium compounds (DDACs), and alkyltrimethyl ammonium compounds (ATMACs), some of which were produced in volumes ranging from 10 to 50 million pounds in the United States in 2015 [1] . After the ban of triclosan use in antibacterial soap by the United States Food and Drug Administration in 2016, some QACs have been used as its replacements [1, 2] . Moreover, the use of QACs as disinfectants has increased since the outbreak of the coronavirus disease 2019 (COVID- 19) due to their effectiveness against SARS-2-CoV [1] . This pattern of increased use may continue even beyond the pandemic as the global consumption of disinfecting products is predicted to increase at a rate of 10% per year from 2020 to 2027 [3] . QACs have been detected in the environment, including wastewater sludge, surface waters, sediments, and soil [4] [5] [6] [7] [8] [9] [10] . They have also been found in foodstuff (e.g., fruits, milk, and vegetables), dust, and air, suggesting that humans can be exposed to QACs via diet, dust ingestion, dermal absorption, and inhalation [11] [12] [13] [14] [15] [16] [17] [18] . However, despite extensive use, there is very limited data on human exposure to and biomonitoring of QACs. The only two existing biomonitoring studies detected several QACs (e.g., C12-and C14-BACs) in blood and have demonstrated that these compounds can bioaccumulate in the human body [17, 19] . Moreover, the latest research indicates that human exposure to QACs has increased during the COVID-19 pandemic [16, 17] . However, there are no studies on the occurrence of QACs in human breast milk, a major nutritional source for infants. There is a growing concern regarding the toxicity of some QACs. Most studies on sub-chronic toxicity of BACs and DDACs have shown that exposure to these compounds can result in skin irritation [20] [21] [22] and adverse respiratory effects [23] [24] [25] [26] . Recent in vitro, in vivo, and epidemiological studies on the chronic QAC exposure show that exposure to BACs and DDACs is associated with immunotoxicity [19] , metabolic disorders [27, 28] , and reproductive toxicity [29, 30] . Furthermore, BACs can cross the placenta and alter cholesterol and lipid homeostasis in neonatal mice brains after gestational exposure [31] , suggesting that BACs are potential neurotoxicants. Infants are more vulnerable to adverse effects of environmental exposures due to their rapid development and growth [32, 33] ; therefore, it is critical to evaluate the early-life environmental exposures. Breastfeeding is recognized as a significant exposure pathway to many environmental contaminants for nursing infants [34] [35] [36] . For the first time, this study reports the levels of eighteen QACs, including 6 BACs (with alkyl chain lengths of C8-C18), 6 DDACs (C8-C18), and 6 ATMACs (C8-C18), in breast milk samples collected from U.S. mothers, as well as estimates the daily lactational intake of these compounds for nursing infants. Forty-eight primiparous women pregnant and planning to breastfeed or currently breastfeeding and residing in Seattle, Washington, United States were recruited over social media channels and via parenting groups and paper flyers during March-October 2019 (before the COVID-19 pandemic) [36] . Breast milk was manually extracted into a provided empty glass jar pre-cleaned with water, isopropyl alcohol, and methanol (breast pumps were not used). After collection, the samples were taken from participants within 24 h and stored at −4 o C until shipment to Indiana University, where they were stored at −20 o C until analysis. Information on demographics and socioeconomic status, as well as the use of household cleaners, disinfectants, personal care products, and the household disinfection frequency was also collected (Table 1) . Ingredient information for each product listed in surveys was searched online. The products were grouped based on the following categories: cleaning products without QACs, cleaning products with QACs, personal care products with ATMACs, and personal care products without ATMACs. The QACs-containing products included sprays (squirt bottles) and wipes. Two mL of breast milk (thawed at room temperature) were spiked with surrogate standards (d 7 -C12-BAC and d 9 -C10-ATMAC) and ultrasonicated in 4 mL of acetonitrile for 1 h. The supernatant was transferred to a new tube after the sample was centrifuged (3000 rpm, 5 min). The residue was re-extracted twice, and supernatants were combined, concentrated to 2 mL under N 2 in a water bath at 40°C and diluted with 4 mL of 5% ammonium hydroxide in water (v/v). The sample was loaded on an Oasis WCX cartridge (6 cc, 150 mg, 30 µm) preconditioned with 6 mL of methanol and 6 mL of water. After washing with 3 mL of 5% ammonium hydroxide in water (v/v) and 3 mL of 10% methanol in water (v/v), the cartridges were dried under vacuum. The target analytes were eluted with 6 mL of 2% formic acid in methanol (v/v). The extract was evaporated to The target compounds were identified and quantified on an ultraperformance liquid chromatograph coupled to a triple-quadrupole mass spectrometer (Agilent 1290 Infinity II UPLC -6470 QQQ-MS) in the positive electrospray ionization (ESI+) mode using a previously developed method [17] . An Acquity UPLC BEH C 18 column (50 mm, 2.1 mm i.d., 1.7 μm thickness, Waters, Milford, MA) was used for the UPLC separation of the target analytes. A delay column (ZORBAX RR Eclipse Plus C 18 , 50 mm, 4.6 mm i.d., 3.5 µm thickness, Agilent, Palo Alto, CA) was set up to reduce the background contamination from the instrument. The mobile phase consisted of water (A) and acetonitrile (B), both containing 0.1% formic acid. The flow rate was 0.4 mL/min. The following gradient was employed: 10% B for 0.5 min initially, ramped to 100% B at 6 min and held for 4 min, returned to 10% B at 10.5 min and equilibrated for 3.5 min after every run. The injection volume was 5 μL. The nebulizer, gas flow, gas temperature, capillary voltage, sheath gas temperature, and sheath gas flow, were set at 25 psi, 10 L/min, 300°C, 3500 V, 350°C, and 12 L/min, respectively. The data acquisition was conducted under a multiple reaction monitoring (MRM) mode and the optimized MRM transitions, fragmentors, and collision energies are presented in Table S1 . All glassware was heated at 500°C for 8 h in a muffle furnace before use. Procedural blanks were used to monitor background contamination in the laboratory (n = 5). In addition, field blanks (n = 2) were collected to check background contamination during sampling. Method quantification limits (MQLs) were set as ten times the standard deviation of the target analyte levels detected in the blanks. For compounds not detected in the blanks, MQLs were based on a signal-to-noise ratio of ten. All data were blank corrected by subtracting average blank levels from the sample levels. The blank levels for some analytes (e.g., C14-and C18-DDACs and C14-ATMAC) were elevated; however, the levels in samples were still higher than in blanks, hence the detection frequencies did not significantly decrease after blank-correction. Still, the data for these analytes should be considered with caution. Procedural and field blank levels for all analytes are included in Table S2 . Quantification of the detected target analytes was performed by isotope dilution using calibration curves with concentration ranges of 0.1 − 10 ng/mL and correlation coefficients in linearity tests were all >0.99. The absolute average recoveries for the spiked samples ranged from 41 ± 0.5% (mean ± standard error) to 149 ± 5% and are given in Table S3 . The average recoveries of the surrogate standards were 80 ± 0.7% and 73 ± 0.5% for d 7 -C12-BAC and d 9 -C10-ATMAC, respectively (Table S4 ). The concentrations were not corrected based on surrogate recoveries. Lactational estimated daily intakes (EDIs, ng/kg body weight [bw] /day) of QACs were calculated using Eq. 1: where C is a median concentration of a QAC in breast milk in ng/mL and FIR is a food ingestion rate (mL/kg bw/day) representing the average daily intake of breast milk (150, 140, 110, and 83 mL/kg bw/day for <1, 1-3, 3-6, and 6-12 month old infants, respectively) [37] . Statistical analyses were conducted using IBM SPSS Statistics 24 and Minitab 13 and plots were generated using Sigma Plot 13. Correlation heatmaps and hierarchical clustering were done using Pearson correlation analysis in R studio. No significant correlation was found between the lipid content and QAC concentrations in breast milk (Table S5) ; hence concentrations are given in ng/mL. Concentrations below MQLs were replaced with MQL/2 values for the descriptive statistics and correlation analyses. The significance level was set at p < 0.05. A description of the participants' demographic characteristics is presented in Table 1 . All mothers were breastfeeding their first child. Most of the participants were Caucasian and lived in or around Seattle, Washington (the average [with standard error] residence time was 13 ± 11 years). Participants' age ranged from 24 to 42 years old (average 34 ± 4.0 years). Ninety-six percent of the mothers had attained higher education and 80% lived in middle or upper-middle income neighborhoods. Fifty-eight percent had a normal BMI (18.5-24.9), while 34% were overweight or obese. No significant correlation was found between the QAC concentrations and demographic characteristics, possibly due to the limited sample size. The detection frequencies and concentrations of the 18 QACs measured in breast milk are given in Table 2 . Thirteen of the 18 QACs were detected in breast milk and 7 were found in more than half of the samples. All analyzed samples had at least one QAC detected above the limit of detection. The total QAC concentrations (ΣQAC, the sum of the 13 detected QACs) ranged from 0.33 to 7.4 ng/mL with a median concentration of 1.5 ng/mL. BACs were the most abundant QACs found in these samples with a median ΣBAC concentration (the sum of 5 detected BACs) of 0.92 ng/mL accounting for 71% of the ΣQAC concentration, followed by ATMACs detected at a median ∑ATMAC [the sum of 6 detected ATMACs] concentration of 0.44 ng/mL (29% of the ΣQAC concentration). DDACs were detected in 15% of the samples and at lower concentrations (<2.2-2.8 ng/mL). C10-C16 BACs and C14-and C16-ATMACs were detected in the majority of the samples (67-88%). The most abundant QAC was C14-BAC with a median concentration of 0.45 ng/mL, followed by C12-BAC (median 0.38 ng/mL), C16-ATMAC (0.21 ng/mL), and C14-ATMAC (0.16 ng/mL). These four compounds accounted for 92% of the ΣQAC concentrations. C10-and C16-BACs and C18-ATMAC were detected at significantly lower concentrations (p < 0.05 based on a one-way analysis of variance [ANOVA], Table 2 and Fig. 1 ). Although C10-DDAC was only detected in 8% of the samples, high concentrations of C10-DDAC were exclusively found in the samples collected from the mothers who reported using QACcontaining disinfectants. C18-BAC, C8-and C10-DDACs, and C8-C12 ATMACs were found in less than half of the samples, and C8-BAC and C12-C18 DDACs were not detected. The individual QACs with detection frequencies over 50% were clustered into two major groups based on the correlation heatmaps and hierarchical clustering (Fig. S1 ). The first group consisted of C10-C16 BACs and C14-ATMAC (r: 0.44-0.96, p < 0.05) and the other cluster included C16-and C18-ATMACs (r: 0.33-0.44, p < 0.05). Forty-two percent of mothers in this study indicated that they regularly used QAC-containing disinfecting products in their homes. Among those using such products, sixty-two percent used disinfecting wipes, while the rest used sprays (squirt bottles). More than half of mothers reported disinfecting less than once a week. Overall, the mean ∑QAC concentration in breast milk from the mothers who used QAC-containing disinfecting products was 1.3 times higher than that in mothers who did not disinfect or used disinfectants without QACs ( Higher ∑ATMAC concentrations were found in the group of mothers who used QAC-containing disinfecting products, specifically in those who used disinfecting sprays (Fig. 2) . No relationship was found between the ∑ATMAC concentrations and the use of personal care products that list ATMACs as the main ingredients. Lactational estimated daily intakes (EDIs) of QACs for infants of <1, 1-3, 3-6, and 6-12 month old are presented in Table 3 . The highest median ΣQAC EDI was found for the <1 month old infants (230 ng/kg bw/day), followed by that for the 1-3 month old (210 ng/kg bw/day), 3-6 month old (170 ng/kg bw/day), and 6-12 month old (120 ng/kg bw/day) infants. This decline can be explained by the increase in the body weight and decrease in breast milk consumption with age. The median EDI for C14-BAC was the highest for all age groups (37-68 ng/kg bw/day), followed by the EDI for C12-BAC (32-57 ng/kg bw/day). In the highexposure scenario (based on the 95 th percentile concentrations), the ΣQAC EDI increased to 420-750 ng/kg bw/day. Our findings indicate widepsread detection of QACs in breast milk with at least one QAC found in each sample and 7 QACs detected in more than half of the samples. As this is the first study reporting the occurrence of QACs in breast milk, a direct comparison of our results with other studies is not possible. When comparing the QAC levels in this study to the previously reported levels of emerging *Percent contribution to the ∑QAC concentration was not calculated because of DF < 50%.