Measuring environmental phenols and chlorinated organic chemicals in breast milk using automated on-line column-switching–high performance liquid chromatography–isotope dilution tandem mass spectrometry

Abstract

Breast milk is one possible route of exposure to environmental chemicals, including phenols and chlorinated organic chemicals for breast-fed infants. We developed a highly sensitive method of analyzing breast milk for triclocarban (3,4,4 -trichlorocarbanilide) and eight phenolic compounds: bisphenol A (BPA), 4-tert-octylphenol (4-tOP), ortho-phenylphenol (OPP), 2,4-dichlorophenol, 2,5-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, and 2-hydroxy-4-metoxybenzophenone (BP-3). The method includes adding a solution containing a stable isotope of each chemical, enzymatic hydrolysis of the conjugated chemicals in the milk, and on-line solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry. It can also be used to measure the free (unconjugated) species by omitting the enzymatic deconjugation step. The method, validated using pooled breast milk samples, has inter-day coefficient of variations ranging from 4.8 to 18.9% for most analytes, and spiked recoveries generally about 100%. Detection limits for most analytes are below 1 ng/mL in 100 L of breast milk. We tested the usefulness of the method by measuring concentrations of these nine compounds in 20 breast milk samples. BPA, OPP, and BP-3 were detected in more than 60% of the samples tested. The free species of these compounds appear to be most prevalent in milk.

NTP‐CERHR expert panel report on the reproductive and developmental toxicity of bisphenol A

“…Bisphenol A was measured after enzymatic hydrolysis of conjugates. Ye et al (2006) found measurable concentrations of bisphenol A in milk samples from 18 of 20 lactating women. Free bisphenol A was found in samples from 12 women.…”

“…There were no differences between pregnant and non-pregnant blood levels (median in mg/L 0.44, range 5 0.22-0.87; mean1SD 5 0.4610.20) . Median bisphenol A concentrations in human milk were reported to be r1.4 mg/L Ye et al, 2006). One of the studies reported a milk/serum ratio of 1.3 .…”

Widely Used Pesticides with Previously Unknown Endocrine Activity Revealed as in Vitro Antiandrogens

“…In our exposure ranking system, it ranked 12th out of 37 test compounds ( Table 1). Considering that ortho-phenyl phenol was highly ranked by exposure and that non agricultural sources were absent from our exposure scores, it is not surprising that it was detected in all human urine samples tested in two studies [mean concentration, 2.9 nM, n = 30 samples (Ye et al 2005); 35.2 nM, n = 22 samples (Bartels et al 1997)], 85% of breast milk samples [mean concentration, 10.6 nM, n = 20 samples (Ye et al 2006)], and 30% of amniotic fluid samples [mean concentration, 0.76 nM, n = 20 samples (Bradman et al 2003)] in the United States. ortho-Phenyl phenol was previously identified as a receptor-mediated anti androgen (Kojima et al 2004), but no data are available on its possible effects in vivo.…”

Urinary, Circulating, and Tissue Biomonitoring Studies Indicate Widespread Exposure to Bisphenol A

“…In another study, Sun et al (2004) detected unconjugated BPA (range, 0.28-0.97 ng/mL; mean, 0.61 ng/mL) in the breast milk of 100% of the women studied. A third study detected unconjugated BPA in 60% of samples (mean, 1.3 ng/mL milk) and total BPA in 90% (mean, 1.1 ng/mL milk) (Ye et al 2006). In the fourth study, Ye et al (2008a) detected unconjugated and total BPA in all four of the samples examined.…”