Ultrasound gel as an unrecognized source of exposure to phthalates and phenols among pregnant women undergoing routine scan

Background: Systemic absorption of phthalates and parabens has been demonstrated after dermal application of body lotion, and medical devices such as intravenous bags and tubing have been identified as a source of exposure to di(2-ethylhexyl) phthalate (DEHP). However, use of products during medical procedures such as aqueous gel applied during obstetrical ultrasound in pregnancy has not been investigated as a potential source of endocrine disrupting chemical (EDC) exposure. Human studies have associated EDCs with various adverse pregnancy outcomes. There is a need to identify sources of inadvertent exposure to EDCs especially during vulnerable developmental periods such as pregnancy.

Objectives: We conducted a pilot study to determine whether use of gel during routine obstetrical ultrasound increased urinary concentrations of phthalate and phenol biomarkers.

Methods: We recruited 13 women from the Massachusetts General Hospital who provided spot urine samples at the time of their second trimester anatomic survey. The first sample was collected prior to the procedure (pre-exposure, time 1), and two additional samples were obtained at approximately 1-2h (time 2) and 7-12h (time 3) post-exposure following the scan.

Results: Urinary concentrations of several DEHP metabolites and metabolite of diisononyl cyclohexane-1,2-dicarboxylate (DINCH) increased across time. For example, the geometric mean concentrations of mono(2-ethyl-5-hydroxyhexyl) phthalate increased from 3.1ng/ml to 7.1ng/ml (p-value=0.03) between time 1 and time 3. We also observed significant differences in concentrations of metabolites of butylbenzyl phthalate (BBzP), di-n-butyl phthalate (DnBP), and di-isobutyl phthalate (DiBP). For example, mono-n-butyl phthalate (metabolite of DnBP) decreased from 3.5ng/ml to 1.8ng/ml (p-value=0.04) between time 1 and time 2, but then increased to 6.6ng/ml (p-value=0.002) at time 3. Propylparaben concentrations increased from 8.9ng/ml to 33.6ng/ml between time 1 and time 2 (p-value=0.005), followed by a decrease to 12.9ng/ml at time 3 (p-value=0.01). However, we cannot rule out the possibility that some of the observed differences are due to other sources of exposure to these compounds.

Conclusions: While additional research is needed, this pilot study potentially identifies a previously unknown source of phthalate and paraben exposure among pregnant women undergoing routine ultrasound examination.