Systematic analysis of the relationship between standardized biological levels of polychlorinated biphenyls and thyroid function in pregnant women and newborns

• Published in: Chemosphere (Oxford) Vol. 98; pp. 1 - 17
• Main Authors: El Majidi, Naïma, Bouchard, Michèle, Carrier, Gaétan
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-03-2014; Elsevier
• Subjects: Analysis. Health state; Biological and medical sciences; Environmental Monitoring; Environmental Pollutants - blood; Epidemiologic Studies; Epidemiology; Exposure standardization; Female; General aspects; Humans; Infant, Newborn - blood; Maternal Exposure - statistics & numerical data; Medical sciences; Newborns; Polychlorinated biphenyls; Polychlorinated Biphenyls - blood; Pregnancy; Pregnancy - blood; Prenatal exposure; Public health. Hygiene; Public health. Hygiene-occupational medicine; Thyroid Gland - physiology; Thyroid hormones; Thyroid Hormones - blood; Thyrotropin - blood; Pregnancy; Newborns; Polychlorinated biphenyls; Exposure standardization; Thyroid hormones; Prenatal exposure; Biological fluid; Standardization; Review; Epidemiology; Blood plasma; Dose activity relation; Persistent organic pollutant; Thyroid function; Chlorocarbon; Aromatic compound; Woman; Public health; Human; Statistical analysis; Polychlorobiphenyls; Exposure; Regression analysis; Whole blood; Newborn; Correlation analysis; Thyroid hormone; Umbilical cord
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2013.10.006

•A systematic analysis of published data on thyroid effects of PCBs was conducted.•Biological PCB levels were standardized between epidemiological studies.•A “standardized biological concentration–response” relationship was established.•There is little evidence of a significant impact of PCBs on thyroid function.
The impact polychlorinated biphenyl (PCB) exposure on thyroid status in pregnant women and newborns was investigated in various epidemiological studies, but findings show inconsistencies, and differences in biological indicators of exposure between studies limits comparison of results. The aim of this research was to use a procedure previously developed to standardize PCB biological concentration data between published studies to perform a systematic analysis of associations between PCB exposure and thyroid hormones (THs) (total and free T3 and T4) or thyroid stimulating hormone (TSH) in pregnant women and newborns. Biological concentrations from nineteen studies were expressed in total PCB equivalent per kg of lipids in maternal plasma (μgPCBMPEQkg−1 lipids). Systematic analysis of the “standardized biological concentration–thyroid parameters” relationship was conducted through the application of methodological criteria in both pregnant women and newborns. Standardization of PCB levels and application of methodological criteria led to assign higher confidence to ten of the reviewed studies. Among the retained studies in pregnant women, only one reported a significant association between PCBs and total T3 levels, but no association were observed when circulating TSH and free T4 levels were used to assess thyroid function. Regarding the association between prenatal PCB exposure and thyroid status in newborns, a lack of significant association was consistently obtained in the retained studies assigned an overall high confidence. The weight of evidence of a significant impact of PCB exposure on TSH and TH levels at the described biological levels in pregnant women and newborns (mean<1000μgPCBMPEQkg−1 lipids) appears low according to this systematical analysis.