The first detection of quaternary ammonium compounds in breast milk: Implications for early-life exposure

Abstract

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.

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.

Keywords: Biomonitoring; Child Exposure/Health; Early-life Exposure; Emerging Contaminants.

Fig. 1. Concentrations of QACs detected in more than 50% of the breast milk samples (ng/mL).

Concentrations are shown as box plots, representing the 25^th and 75^th percentiles; black lines represent the median and the whiskers represent the 10^th and 90^th percentiles; the dots represent the 5^th and 95^th percentiles. The letters show the results of the one-way analysis of variance (ANOVA) and the concentrations are ranked from the highest to the lowest in alphabetical order (A stands for the highest and C for the lowest). The concentrations sharing the same letter are not statistically different at p < 0.05 (e.g., C12-BAC, C14-BAC, and C16-ATMAC).

Fig. 2. The ∑BAC and ∑ATMAC concentrations (mean ± standard error, ng/mL) in breast milk samples grouped based on mothers’ disinfection habits.

A Levels in breast milk collected from mothers who do (n = 21) vs. those who do not disinfect or use (n = 26) QAC-containing disinfecting products. B Levels in breast milk collected from mothers who use sprays (n = 8) vs. wipes (n = 13). C Levels in mothers who disinfect more frequently (more than once a week, n = 8) vs. those who disinfect less frequently (less than once a week, n = 11).