Endocrine disruption assessment: exposure, biomonitoring and potential activity of widespread endocrine disruptors during pregnancy and early stages of life
- Autores: María Ángeles Martínez Rodríguez
- Directores de la Tesis: Marta Schuhmacher Ansuategui (dir. tes.), Vikas Kumar (codir. tes.), Joaquim Rovira Solano (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: José Luis Domingo Roig (presid.), Martine Vrijheid (secret.), Dimosthenis Sarigiannis (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Endocrine disruptors (EDs) are exogenous substances that alter function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub)populations. There is a group of EDs that takes an important place due to their widespread distribution and presence in food-packaging or food contact materials. The packaging is an essential element in food manufacture. However, packaging could be a source of contamination as migration can occur from these materials with the transfer of chemicals or particles into the food. According to that, bisphenol A (BPA) and two analogues of it, bisphenol S (BPS) and bisphenol F (BPF); phthalates and non-phthalate plasticizers; perfluorooalkilated substances (PFAS) specifically perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) and tetrabromobisphenol A (TBBPA) were selected in this thesis.
The general hypothesis of this thesis is that, there is exposure to Endocrine Disruptors (EDs) during the prenatal period and early stages of life and this exposure can cause adverse outcomes. Therefore, the general objective is to assess the exposure levels to different EDs from pregnant women of EXHES cohort in Tarragona, Spain and to study how these chemicals can affect normal cellular development. This main goal has been divided into four different specific objectives: (I) to estimate the exposure to EDs for pregnant women and their babies. (II) Biomonitoring the levels of EDs in urine, blood and breast milk from pregnant women. (III) To reconstruct the exposure to EDs using biomonitored levels and the physiologically based pharmacokinetic (PBPK) model. (IV) To determine the endocrine potential activity of some widely used EDs.
In Chapter 1 (publication 1 and 2), exposure to two high distributed EDs, BPA and DEHP from the EXHES Tarragona, Spain, cohort of pregnant women and their babies were calculated. Exposure assessments based on data obtained from questionnaires and personal interviews were used. Subsequently, the contribution of each item to the total exposure for the EXHES cohort was evaluated. Results showed that diet had the highest contribution to total exposure with >99.9% for BPA and 63% for DEHP. However, with this method, based on data obtained from questionnaires and interviews, it is possible to underestimate the exposure due to a lack of knowledge of all possible sources that would also contribute to total exposure. Consequently, another possible approach for investigating human exposure to different chemicals could be to reconstruct the exposure through biomonitoring data. For that reason, it was compared the previously estimated exposure with the reconstructed exposure using the DEHP in urine as a case study (chapter 2, publication 3). Apart from phthalates metabolites determination, DINCH metabolites were also measured in urine. Surprisingly, they were detected in almost all (94 %) pregnant women's urine samples. Results showed a correlation between lower birth weights with higher levels of DINCH metabolites in maternal urine (p<0.05).
Both approaches, the estimated and the reconstructed, were combined with PBPK modelling to predict the amount of BPA and MEHP (DEHP metabolite) that can reach the fetus. The results showed that both values obtained from the PBPK model using estimated or reconstructed data were close to each other. However, the PBPK simulated exposure for reconstructed dose was closer to the extrapolated 24 h biomonitoring data. In general terms, BPA and MEHP stay longer in the fetal body, which may cause a higher risk to fetuses and makes the fetus more vulnerable to the exposure compared with the mothers. Consequently, PBPK results from dose reconstruction were more accurate compared with the previously estimated PBPK-simulation. These results suggested that is possible to estimate the exposure of a chemical from their metabolites concentrations in spot urine. Also, these results from reconstructed data are closer to a real exposure scenario. Our values for BPA and DEHP estimated and reconstructed were far away from the tolerable dietary intake (TDI) values of the EFSA (4 μg/kgbw/day) and ECHA (50 μg/kgbw/day) for BPA and DEHP, respectively.
The same methodology applied in chapters 1 and 2 to assess the estimated exposure was used again for PFASs, a group of synthetic chemicals, which include PFOS and PFOA (chapter 2, publication 4). Besides, to verify the accuracy of this method, the estimated exposure was compared with biomonitoring data for the same cohort. In agreement with many other studies, results showed that again, dietary intake was the main route of exposure to PFOS (>99%) and PFOA (>96%). Concerning the prenatal exposure, the model simulation results obtained for plasma were compared with biomonitoring data from the same cohort. To achieve this goal, PFOA and PFOS were biomonitored in maternal blood. It was detected traces of PFOS in all samples. PFOA and PFOS plasma levels in the first trimester were significantly higher than those at delivery and in cord blood. Decreases of 69% and 25% in PFOA and PFOS plasma levels, respectively, between the first trimester and at delivery were registered. This fact could be due to both a placental transfer and a dilution process caused by the increase of blood plasma volume. In this study, around 70% and 60% of maternal plasma levels in the first trimester were found in cord blood for PFOA and PFOS, respectively. Modelled levels were higher than those obtained by biomonitoring. The performance of the PBPK model can be further improved by introducing temporal dynamics of exposure concentration and physiological parameters for long-term exposure. Despite this, the PBPK model was able to validate analytical data from biomonitoring samples, even with a small cohort population. Dietary exposure of PFOA in our study were close to, but below, the provisional tolerable weekly intake (TWI) set by EFSA (6 ng/kgbw/week). In turn, the dietary intake of PFOS was calculated to be well above the most updated provisional TWI (13 ng/kgbw/week). Therefore, more studies regarding the exposure of PFOS are needed.
Apart from estimate the prenatal exposure to EDs (publications from 1 to 4), the exposure to BPA during the early stages of life through breast and infant formula milk (chapter 2, publication 5) was established. To assess that, it was used the concentration levels of BPA in breast and formula milk. The presence of some pollutants like BPA, TBBPA, fatty acids and a wide spectrum of major and trace elements were analysed in human milk and infant formula. The concentration of BPA was significantly higher in infant formula samples than in breast milk, which also contained significantly lower values of some essential elements. The fatty acid profiling also revealed major differences between human milk and infant formulas, which should be taken into account in the development of new formulas a well as in specific recommendations for the diet of breastfeeding mothers. Results showed that estimated BPA was higher in formula-fed infants than in breastfed infants. However, BPA intake was far below the TDI threshold set by EFSA (4 μg/kgbw/day) for both formula-fed and breastfed infants. Consequently, the results of this study reinforce that breastfeeding should be always the first feeding option in early life.
Finally, in this thesis, it was also evaluated the effects of endocrine-disrupting activity. BPA and its analogues, BPS and BPF, were selected as a case study. The European Union (EU) banned the use of BPA in plastic materials that can be in contact with food intended for children (0–3 years). However, the principal analogues of BPA, BPS, and BPF are still being used. Then, in publication 6 (chapter 3) we wanted to clarify if BPA has equal or different effects than its analogues, BPS and BPF, in cell toxicity and on the adipose differentiation process. This was assessed by in vitro experiments with preadipocytic 3T3-L1 cell line. Results suggest that BPA has a greater toxic effect at equal and even lower concentrations than its analogues. However, BPS followed by BPF has higher endocrine-disrupting activity compared with BPA and the control. Further studies on these analogues would be necessary to corroborate these results, and consequently, changes in the legislation on the bisphenols' family would be necessary.
As a general conclusion, the exposure to selected EDs (BPA, and its analogues, BPS and BPF; phthalates and non-phthalate plasticizers; PFAS, specifically PFOS and PFOA, and TBBPA) is a common phenomenon in adult populations and during early stages of life, such as prenatal and newborn children. This exposure can cause adverse outcomes. For that reason, more studies regarding endocrine potential activity are crucial to reevaluate the statements and the TDI exposure including dietary and non-dietary sources. Regulations based on the assessment of the safety of the most vulnerable exposure population, pregnant women and their children, should be established in the endocrine disruption context.
