BBPA is rapidly metabolized. Therefore in the absence of a constant exposure source and intensity, biomarker levels would be expected to change over time, as has previously been reported. Only free (unconjugated) BPA exhibits endocrine activity*** however, in general, existing epidemiological studies have measured total BPA (the sum of free and conjugated) biomarkers. Total BPA biomarker concentration may further be impacted by contamination with environmental sources of free BPA, or in the biospecimen collection process or materials.
We propose a reliability study of BPA biomarkers over the course of pregnancy that separates total and free BPA, using the reliability substudy urine samples collected in MoBa.
Heidi Aase, Norwegian Institute of Public Health