Total Effective Xenoestrogen Burden Research Articles

Total Effective Xenoestrogen Burden in Serum Samples and Risk of Endometrial Cancer in the Spanish Screenwide Case-Control Study.

Endometrial cancer is a hormone-dependent cancer, and estrogens play a relevant role in its etiology. However, little is known about the effects of environmental pollutants that act as xenoestrogens or that influence estrogenic activity through different pathways. We aimed to assess the relationship between the combined estrogenic activity of mixtures of xenoestrogens present in serum samples and the risk of endometrial cancer in the Screenwide case-control study. The total effective xenoestrogen burden (TEXB) attributable to organohalogenated compounds () and to endogenous hormones and more polar xenoestrogens () was assessed in serum from 156 patients with endometrial cancer (cases) and 150 controls by combining chemical extraction and separation by high-performance liquid chromatography with the E-SCREEN bioassay for estrogenicity. Median and levels for cases (0.30 and , respectively) and controls (0.42 and , respectively) did not significantly differ ( and 0.933, respectively). An inverted-U risk trend across serum and levels was observed in multivariate adjusted models: Positive associations were observed for the second category of exposure in comparison to the lowest category of exposure [ (95% CI: 1.13, 3.94) for , and (95% CI: 1.62, 6.81) for ], whereas no significant associations were observed between the third category of exposure and the first [ (95% CI: 0.64, 2.31) for , and (95% CI: 0.75, 3.33) for ]. In mutually adjusted models for and levels, the association of with endometrial cancer risk was attenuated [ (95% CI: 0.61, 3.47) for the second category of exposure], as well as estimates for (; 95% CI: 1.03, 6.99). Most of the individual halogenated contaminants showed no associations with both TEXB and endometrial cancer. We evaluated serum total xenoestrogen burden in relation to endometrial cancer risk and found an inverted-U risk trend across increasing categories of exposure. The use of in vitro bioassays with human samples may lead to a paradigm shift in the way we understand the negative impact of chemical mixtures on human health effects. These results are relevant from a public health perspective and for decision-makers in charge of controlling the production and distribution of chemicals with xenoestrogenic activity. https://doi.org/10.1289/EHP13202.

Placental concentrations of xenoestrogenic organochlorine pesticides and polychlorinated biphenyls and assessment of their xenoestrogenicity in the PA-MAMI mother-child cohort

BackgroundOrganochlorine pesticides (OCPs) and polychlorinated biphenyls (PCB), they have contributed to the exposure of women to persistent organic pollutants (POPs). These compounds can cross the placental barrier and interfere with the hormonal system of newborns. AimTo determine concentrations of OCPs and PCBs and their xenoestrogenic activity in placentas of women from the PA-MAMI cohort of Panama. MethodsThirty-nine placenta samples from women in the Azuero peninsula (Panama) were analyzed. Five OCPs [p-p'-dichlorodiphenyldichloroethylene (p-p’-DDE), beta-hexachlorohexane (β-HCH), γ-hexachlorohexane (lindane), hexachlorobenzene (HCB) and mirex] and three PCB congeners (PCB-138, PCB-153 and PCB-180) were quantified in placenta extracts. The xenoestrogenic activity of extracts was assessed with the E-Screen bioassay to estimate the total effective xenoestrogen burden (TEXB). ResultsAll placental samples were positive for at least three POP residues and >70% for at least six. The frequencies of quantified OCPs ranged from 100% for p,p'-DDE and HCB to 30.8% for β-HCH. The highest median concentration was for lindane (380.0 pg/g placenta), followed by p,p'-DDE (280.0 pg/g placenta), and HCB (90.0 pg/g placenta). Exposure to p,p’-DDE was associated with greater meat consumption, suggesting that animal fat is a major source of exposure to DDT metabolites. The frequency of detected PCBs ranged between 70 and 90%; the highest median concentration was for PCB 138 (17.0 pg/g placenta), followed by PCB 153 (16.0 pg/g placenta). All placentas were positive in the estrogenicity bioassay with a median TEXB-α of 0.91 pM Eeq/g of placenta. Exposure to lindane was positively associated with the xenoestrogenicity of TEXB- α, whereas this association was negative in the case of exposure to PCB 153. ConclusionsTo our best knowledge, this study contributes the first evidence on the presence of POPs and xenoestrogenic burden in placentas from Latin-American women. Given concerns about the consequences of prenatal exposure to these compounds on children's health, preventive measures are highly recommended to eliminate or minimize the risk of OCP exposure during pregnancy.

Changes in the total effective xenoestrogen burden (TEXB) of breast cancer patients during an 18-month post-surgical follow-up

We aimed to assess changes in the total effective xenoestrogen burden (TEXB) −a biomarker of combined effect of mixtures of xenoestrogens- in breast cancer patients at surgery (breast adipose tissue) and at different time points during an 18-month follow-up (abdominal adipose tissue), and to analyze the potential influence of socio-demographic, reproductive, tumor, and treatment characteristics on TEXB levels. TEXB-alpha (due to persistent organohalogenated chemicals) and TEXB-beta (due mainly to endogenous estrogens) were quantified in 44 women. TEXB values significantly increased over follow-up (p <0.001); the largest difference was observed at 6-12 months post-surgery (p <0.001); then decreased over time. TEXB-alpha at 6-18 months was significantly higher in younger patients with estrogen receptor positivity (p=0.034) and in those receiving anti-neoplasm chemotherapy. Cancer treatment may be responsible for the increase in TEXB-alpha observed in patients with hormone-dependent tumors, which may confer to xenoestrogens a role in the progression of the disease.

Total Effective Xenoestrogen Burden in Serum Samples and Risk for Breast Cancer in a Population-Based Multicase–Control Study in Spain

Background:Most studies on endocrine-disrupting chemicals and breast cancer have focused on single compounds and have produced inconclusive findings.Objectives:We assessed the combined estrogenic effects of mixtures of xenoestrogens in serum and their relationship to breast cancer risk.Methods:A total of 186 incident pretreatment breast cancer cases and 196 frequency-matched controls were randomly sampled from a large population-based multicase–control study in Spain. The total effective xenoestrogen burden attributable to organohalogenated xenoestrogens (TEXB-α) and endogenous hormones and more polar xenoestrogens (TEXB-β) was determined in serum samples using high-performance liquid chromatography and E-Screen bioassay. Odds ratios for breast cancer comparing tertiles of serum TEXB-α and TEXB-β were estimated using logistic models, and smooth risk trends were obtained using spline models.Results:Cases had higher geometric mean TEXB-α and TEXB-β levels (8.32 and 9.94 Eeq pM/mL, respectively) than controls (2.99 and 5.96 Eeq pM/mL, respectively). The fully adjusted odds ratios for breast cancer (95% confidence intervals) comparing the second and third tertiles of TEXB-α with the first tertile were 1.77 (0.76, 4.10) and 3.45 (1.50, 7.97), respectively, and those for TEXB-β were 2.35 (1.10, 5.03) and 4.01 (1.88, 8.56), respectively. A steady increase in risk was evident across all detected TEXB-α levels and a sigmoidal trend was observed for TEXB-β. Individual xenoestrogens showed weak and opposing associations with breast cancer risk.Conclusions:This is the first study to show a strong positive association between serum total xenoestrogen burden and breast cancer risk, highlighting the importance of evaluating xenoestrogen mixtures, rather than single compounds, when studying hormone-related cancers.Citation:Pastor-Barriuso R, Fernández MF, Castaño-Vinyals G, Whelan D, Pérez-Gómez B, Llorca J, Villanueva CM, Guevara M, Molina-Molina JM, Artacho-Cordón F, Barriuso-Lapresa L, Tusquets I, Dierssen-Sotos T, Aragonés N, Olea N, Kogevinas M, Pollán M. 2016. Total effective xenoestrogen burden in serum samples and risk for breast cancer in a population-based multicase–control study in Spain. Environ Health Perspect 124:1575–1582; http://dx.doi.org/10.1289/EHP157

In utero exposure to mixtures of xenoestrogens and child neuropsychological development

BackgroundTo date, no epidemiological studies have explored the impact and persistence of in utero exposure to mixtures of xenoestrogens on the developing brain. We aimed to assess whether the cumulative effect of xenoestrogens in the placenta is associated with altered infant neuropsychological functioning at two and at four years of age, and if associations differ among boys and girls. MethodsCumulative prenatal exposure to xenoestrogens was quantified in the placenta using the biomarker Total Effective Xenoestrogen Burden (TEXB-alpha) in 489 participants from the INMA (Childhood and the Environment) Project. TEXB-alpha was split in tertiles to test its association with the mental and psychomotor scores of the Bayley Scales of Infant Development (BSID) at 1–2 years of age, and with the McCarthy Scales of Children׳s Abilities (MSCA) general cognitive index and motor scale assessed at 4–5 years of age. Interactions with sex were investigated. ResultsAfter adjustment for potential confounders, no association was observed between TEXB-alpha and mental scores at 1–2 years of age. We found a significant interactions with sex for the association between TEXB-alpha and infant psychomotor development (interaction p-value=0.029). Boys in the third tertile of exposure scored on average 5.2 points less than those in the first tertile on tests of motor development at 1-2 years of age (p-value=0.052), while no associations were observed in girls. However, this association disappeared in children at 4-5 years of age and no association between TEXB-alpha and children׳s cognition was found. ConclusionsOur results suggest that boys’ early motor development might be more vulnerable to prenatal exposure to mixtures of xenoestrogens, but associations do not persist in preschool children.

Prenatal exposure to mixtures of xenoestrogens and repetitive element DNA methylation changes in human placenta

BackgroundPrenatal exposure to endocrine disrupting compounds (EDCs) has previously shown to alter epigenetic marks. ObjectivesIn this work we explore whether prenatal exposure to mixtures of xenoestrogens has the potential to alter the placenta epigenome, by studying DNA methylation in retrotransposons as a surrogate of global DNA methylation. MethodsThe biomarker total effective xenoestrogen burden (TEXB) was measured in 192 placentas from participants in the longitudinal INMA Project. DNA methylation was quantitatively assessed by bisulfite pyrosequencing on 10 different retrotransposons including 3 different long interspersed nuclear elements (LINEs), 4 short interspersed nuclear elements (SINEs) and 3 human endogenous retroviruses (HERVs). Associations were tested using linear mixed-effects regression models and sex interaction was evaluated. ResultsA significant sex interaction was observed for AluYb8 (p-value for interaction <0.001, significant at Bonferroni corrected p-value threshold of 0.0025). Boys with the highest TEXB-alpha levels of exposure (third tertile) presented on average a decrease of 0.84% in methylation compared to those in the first tertile (p-value<0.001), while no significant effects were found in girls (p-value=0.134). ConclusionsOur findings suggest that boys may be more susceptible to the effect of exposure to xenoestrogens during prenatal development, producing shifts in DNA methylation of certain sensitive genomic repetitive sequences in a tissue important for fetal growth and development.

Adipose tissue concentrations of persistent organic pollutants and prevalence of type 2 diabetes in adults from Southern Spain

There is increasing evidence that environmental factors play an important role in the development of type 2 diabetes. Several persistent organic pollutants are suspected to contribute to the increasing prevalence and risk of type 2 diabetes. The aim of this study was to investigate the association of the body burden of three organochlorine pesticides and three polychlorinated biphenyls and the overall estrogenic activity with the risk of type 2 diabetes in a sample of adults from Southern Spain.Samples of adipose tissue and serum were obtained from 386 subjects undergoing non-cancer-related surgery and were extracted using validated methodologies. Residues of persistent organic pollutants were analyzed by means of high-resolution gas chromatography with a mass spectrometry detector in tandem mode. The overall estrogenicity of the adipose tissue extracts was measured by using the total effective xenoestrogen burden (TEXB) biomarker. Data on lifestyle, dietary habits, and health status were gathered from face-to-face interviews and clinical records. Statistical analyses were performed with unconditional logistic regression and different adjustment levels.In the models adjusted for adipose tissue origin, sex, age, and body mass index, the 2nd and 3rd tertiles of adipose tissue concentrations of p,p′-dichlorodiphenyldichloroethylene (p,p′-DDE) were positively associated with the risk of diabetes [odds ratios (95% confidence interval)=3.6 (0.8–17.3) and 4.4 (1.0–21.0), respectively]. A positive association with β-hexachlorocyclohexane was also found when body mass index and adipose tissue origin were removed from the models, with odds ratios (95% confidence interval) of 3.3 (1.0–10.4) and 5.5 (1.7–17.3), for the 2nd and 3rd tertiles of exposure, respectively. In addition, a statistically significant interaction was observed between p,p′-DDE and body mass index, such that the risk of diabetes increased with tertiles of exposure in a linear manner in non-obese subjects but not in the obese, in whom an inverted U-shape pattern was observed.

Male specific association between xenoestrogen levels in placenta and birthweight

BackgroundFetal exposure to endocrine disrupting chemicals may increase the risk for adverse health effects at birth or later in life. ObjectivesThe objective of this study is to analyze the combined effect of xenoestrogens on reproductive and perinatal growth outcomes (child birthweight, early rapid growth and body mass index (BMI) at 14months) using the biomarker total effective xenoestrogen burden (TEXB). Methods490 placentas were randomly collected in the Spanish prospective birth cohort Environment and Childhood (INMA) project. TEXB was used to assess the estrogenicity of placental samples in two fractions: that largely attributable to environmental organohalogenated xenoestrogens (TEXB-alpha), and that mostly due to endogenous estrogens (TEXB-beta), both expressed in estrogen equivalent units (Eeq) per gram of tissue. Linear or logistic regression models were performed adjusting for cohort and confounders. Sex interactions were investigated. ResultsThe median TEXB-alpha level was 0.76pMEeq/g (interquartile range (iqr): 1.14). In multivariate models, higher TEXB-alpha levels (third tertile, >1.22pMEeq/g; iqr: 1.73) were associated with increased birthweight in boys but not in girls (β=148.2g, 95% CI: 14.01, 282.53, pint=0.057). Additionally, higher TEXB-alpha values in boys were related with a lower risk of early rapid growth (OR=0.37; 95% CI: 0.15, 0.88) and with a non significant association with larger BMI z-scores at 14months of age (β=0.29; 95% CI: −0.11, 0.69). ConclusionsThese findings suggest that prenatal exposure to xenoestrogens may increase birthweight in boys, which might have an impact on child obesity and other later health outcomes.

Predictors of the total effective xenoestrogen burden (TEXB) in human adipose tissue. A pilot study

The estrogenicity of biological extracts tested by appropriate bioassay is a standard method to evaluate the total effective xenoestrogen burden (TEXB). Information has been published on the combined effect of xenoestrogens after removing endogenous hormones. The main goal of the present study was to investigate the combined estrogenicity of endogenous and xenoestrogens in human adipose tissue samples with and without HPLC fractionation. The results suggest that both approaches may be useful to study interaction between xenoestrogens and endogenous hormones. TEXB of the whole extract provides information about the overall estrogenicity to which humans are exposed, useful to assess the potential contribution to health outcomes. Additionally, it is possible to identify the source and potency of the estrogenicity by using the method with fractionation, distinguishing the effect of organohalogenated chemicals (alpha-fraction) from that of endogenous hormones and more polar xenoestrogens (beta-fraction). Both methods are an integrative measure of internal estrogen load.

Assessment of PCDD/F, PCB, OCP and BPA dietary exposure of non-breast-fed European infants

The aim of this study is to obtain data on the exposure of non-breast-fed infants to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), polychlorinated biphenyls (PCB), organochlorine pesticides (OCP), and bisphenol A (BPA) and its chlorinated derivatives through consumption of commercial infant foods with largest shares of the market in 22 European Union countries. The E-Screen bioassay was employed to assess the oestrogenicity of the baby foods and the ethoxyresorufin-O-deethylase (EROD) induction was measured to determine the levels of PCDD/F and PCB. Consequently, the highest total effective xenoestrogen burden (TEXB) of 73.60 pM Eeq g−1 was found in the soy-based formula and the EROD bioassay was always below the limit of quantification (LOQ) (3.5 pg g−1). Overall, the estimated dietary exposure to BPA via commercial baby foods was lower than the tolerable daily intake (TDI) of 50 µg kg−1 body weight (bw). Furthermore, the findings indicated that the dietary exposure of 0–9-month-old infants through the products investigated here does not exceed the maximum TDI of 4 pg WHO-TEQ (toxic equivalents) kg−1 bw. However, exposure to more than 2 pg WHO-TEQ kg−1 bw day−1 might occur for 0–4-month-old infants consuming ‘starting’ hypoallergenic formula. Moreover, analysis of OCP indicated that the dietary exposure of non-breast-fed infants was not harmful. Considering the importance of early development and the vulnerability of infants and children, it is essential to determine their dietary exposure to contaminants in order to decide which efforts of risk reduction should receive highest priority.

Assessment of the total effective xenoestrogen burden in extracts of human placentas

We have standardized a method to assess the total effective xenoestrogen burden (TEXB) in human placentas by the extraction and separation by high-performance liquid chromatography of two fractions containing lipophilic xenoestrogens (alpha) and endogenous hormones (beta), followed by assessing their estrogenicity in MCF-7 breast cancer cell-based E-Screen and Yeast Estrogen Screen (YES) bioassays. The means of TEXB alpha concentrations (in estradiol equivalent (Eeq) units) were 1.32 and 0.77 Eeq pM g−1 placenta in the E-Screen and YES, respectively; TEXB beta concentrations were 6.97 and 11.56 Eeq pM g−1 placenta, respectively. The interclass correlation coefficient was low and a fair level of agreement was observed after kappa test correction. According to the E-Screen and YES, TEXB alpha was ≥LOD in 70.0 and 55.0% of the placentas and 92.5 and 82.5% in beta, respectively. Although both bioassays can be recommended for assessing TEXB, there is greater experience with the use of the E-Screen for estrogenic assessment after extensive extraction of complex human matrices.

The total effective xenoestrogen burden, a biomarker of exposure to xenoestrogen mixtures, is predicted by the (anti)estrogenicity of its components

Appropriate biomarkers of human exposure are required for epidemiological studies of endocrine disruption. We addressed this issue by improving a standardized method to assess the total effective xenoestrogen burden (TEXB), a biomarker of xenoestrogen exposure. Extensive separation of xenoestrogens from endogenous hormones was made in 20 adipose tissue samples by HPLC, and two eluates were separated and tested in the E-Screen bioassay. An extensive fractionation protocol was also developed. The objective of this study was to investigate predictors of TEXB by using a multiple regression model after adjusting by confounding factors. The final model included the estrogenicity of 8 out of 11 individual 1-min fractions into which the xenoestrogen eluate was split and the marital status of patients, and it explained 97% of TEXB variability, and variables. Our results indicate that TEXB of complex mixtures can be accurately predicted from the estrogenicity of a small number of components.

2097 ORAL Biomarker analysis of lapatinib with paclitaxel versus paclitaxel as first-line treatment in 580 patients with metastatic breast cancer

To analyse the link between breast cancer and the combined effect of environmental xenoestrogens, we developed, standardised and applied a biomarker of exposure to assess the total effective xenoestrogen burden (TEXB) in human adipose tissue in a case–control study. Environmental oestrogens (TEXB-alpha) are separated from endogenous oestrogens (TEXB-beta), and the combined oestrogenic effect is determined from its proliferative effect (E-Screen assay). The aim of the study was to identify potential confounders, effect modifiers or other covariates associated with higher TEXB levels. In cases, age, family history of breast cancer, lactation experience and smoking were associated with TEXB-alpha. In controls, only age was associated with TEXB-alpha levels. In cases, age, educational level, age at menarche, menopausal status, marital status, lactation experience and smoking were associated with TEXB-beta. In controls, only menopausal status was significantly associated with TEXB-beta levels. In conclusion, TEXB, as a biomarker of exposure, takes account of environmental, dietary, lifestyle, genetic and reproductive factors, which are not usually systematically measured across studies.

Human exposure to endocrine-disrupting chemicals and prenatal risk factors for cryptorchidism and hypospadias: a nested case-control study.

BackgroundExposure to xenoestrogens during pregnancy may disturb the development and function of male sexual organs.ObjectiveIn this study we aimed to determine whether the combined effect of environmental estrogens measured as total effective xenoestrogen burden (TEXB) is a risk factor for male urogenital malformations.MethodsIn a case–control study, nested in a mother–child cohort (n = 702) established at Granada University Hospital, we compared 50 newborns with diagnosis of cryptorchidism and/or hypospadias with 114 boys without malformations matched by gestational age, date of birth, and parity. Controls did not differ from the total cohort in confounding variables. TEXB and levels of 16 organochlorine pesticides were measured in placenta tissues. Characteristics of parents, pregnancy, and birth were gathered by questionnaire. We used conditional and unconditional regression models to estimate odds ratios (ORs) and 95% confidence intervals (CIs).ResultsTEXB from organohalogenated compounds was detectable in 72% and 54% of case and control placentas, respectively. Compared with controls, cases had an OR for detectable versus non-detectable TEXB of 2.82 (95% CI, 1.10–7.24). More pesticides were detected in cases than in controls (9.34 ± 3.19 vs. 6.97 ± 3.93). ORs for cases with detectable levels of pesticides, after adjusting for potential confounders in the conditional regression analysis, were o,p′-DDT (OR = 2.25; 95% CI, 1.03–4.89), p,p′-DDT (OR = 2.63; 95% CI, 1.21–5.72), lindane (OR = 3.38; 95% CI, 1.36–8.38), mirex (OR = 2.85; 95% CI, 1.22–6.66), and endosulfan alpha (OR = 2.19; 95% CI, 0.99–4.82). Engagement of mothers in agriculture (OR = 3.47; 95% CI, 1.33–9.03), fathers’ occupational exposure to xenoestrogens (OR = 2.98; 95% CI, 1.11–8.01), and history of previous stillbirths (OR = 4.20; 95% CI, 1.11–16.66) were also associated with risk of malformations.ConclusionsWe found an increased risk for male urogenital malformations related to the combined effect of environmental estrogens in placenta.

Analysis of population characteristics related to the total effective xenoestrogen burden: A biomarker of xenoestrogen exposure in breast cancer

To analyse the link between breast cancer and the combined effect of environmental xenoestrogens, we developed, standardised and applied a biomarker of exposure to assess the total effective xenoestrogen burden (TEXB) in human adipose tissue in a case–control study. Environmental oestrogens (TEXB-alpha) are separated from endogenous oestrogens (TEXB-beta), and the combined oestrogenic effect is determined from its proliferative effect (E-Screen assay). The aim of the study was to identify potential confounders, effect modifiers or other covariates associated with higher TEXB levels. In cases, age, family history of breast cancer, lactation experience and smoking were associated with TEXB-alpha. In controls, only age was associated with TEXB-alpha levels. In cases, age, educational level, age at menarche, menopausal status, marital status, lactation experience and smoking were associated with TEXB-beta. In controls, only menopausal status was significantly associated with TEXB-beta levels. In conclusion, TEXB, as a biomarker of exposure, takes account of environmental, dietary, lifestyle, genetic and reproductive factors, which are not usually systematically measured across studies.

Biomonitoring of environmental estrogens in human tissues

Two examples are presented for the application of the total effective xenoestrogen burden as biomarker of chemical exposure measured in tissue samples from patients recruited for two case–control studies. The first study focused on environmental chemicals with hormone mimicking activity, the so-called environmental estrogens, and their participation in the etiology of breast cancer. The second study investigated mother–child exposure to persistent organochlorine chemicals and assessed their combined effect on the risk of male urogenital malformations in the newborn.

Breast cancer risk and the combined effect of environmental estrogens.

The present study aimed to determine whether the combined effects of environmental estrogens measured as the total effective xenoestrogen burden (TEXB-alpha) are a risk factor for breast cancer over and above the risk potentially linked to specific pesticides. We measured the levels of 16 organochlorine pesticides as well as TEXB in adipose tissue of 198 women at the time of breast cancer diagnosis. These were compared with findings in 260 age and hospital matched control women without breast cancer. The median levels of p,p'-DDE (1,1-dichloro-2,2-bis( p -chlorophenyl)ethylene), aldrin, endosulfan ether and lindane (the pesticides detected in > 40% of the study population) were higher in cases than controls, although the differences did not reach statistical significance. After adjusting for potential confounders, the odds ratio (OR) for breast cancer in women with detectable levels of aldrin was 1.55 (95% confidence interval (CI) 1.00-2.40). Among the postmenopausal women, the OR for aldrin and lindane was 1.84 (95% CI 1.06-3.18) and 1.76 (95% CI 1.04-2.98), respectively. Among cases with body mass index (BMI) below the median (28.6 kg/m2), the OR was 3.42 (95% CI 1.22-9.58) for women in the highest quartile of TEXB-alpha versus those in the lowest. The subgroup of leaner postmenopausal women showed an increased risk (OR: 5.67; 95% CI 1.59-20.21) for those in the highest tertile versus those in the lowest. We found an increased risk for breast cancer in the leaner women, especially in the leaner postmenopausal subgroup, related to the TEXB-alpha. The pesticides aldrin and lindane are also individually associated with risk.

Assessment of total effective xenoestrogen burden in adipose tissue and identification of chemicals responsible for the combined estrogenic effect.

Test systems to screen for estrogenicity and appropriate biomarkers of human exposure are required for epidemiological studies of endocrine disruption. We addressed these issues by developing and standardising a method to assess the total estrogenic xenobiotic burden in human adipose tissue. In this study, which is the continuation of a previous work, we have improved the protocol for extensive fractionation of a higher number of tissue samples in order to investigate bioaccumulated xenoestrogens that are candidates for estrogenicity and to assess their combined estrogenic effect. This was achieved by extensive HPLC separation of xenoestrogens from endogenous hormones followed by testing of individual fractions in the E-Screen test for estrogenicity. Organochlorine pesticides, PCBs and halogenated bisphenols and alkylphenols were collected in the most lipophilic fractions, followed by progestins, androgens and estradiol esters, and then by steroidal estrogens; phyto- and myco-estrogens were collected around the end of the run. These results were confirmed by exhaustive chemical analysis. In 458 human adipose tissue samples, the total effective xenoestrogen burden was positive in 75% of samples in the pooled fraction that contained organohalogenated xenoestrogens (mean 515.3 pM Eeq/g lipid; range 0-14.5 nM) and in 82% of samples in the pooled fraction where natural estrogens eluted (mean 696.6 pM Eeq/g lipid; range 0-12.9 nM). Organochlorine pesticides emerged as candidate chemicals for the estrogenicity of the first pooled fraction, because DDT and derivatives were present in 98.3% of the samples. However, no correlation was found between the concentration of any single chemical and the estrogenicity determined in the bioassay. There may be several reasons for this lack of concordance: (i) the estrogenic effects depicted in the E-Screen bioassay are a consequence of the combined effect of several organohalogens or (ii) the proliferative effect is due to other chemicals not measured. Because additive, synergistic or antagonistic mechanisms may account for the final effect observed in the pooled fractions, the approach proposed in this work is more appropriate for exposure assessment in epidemiological studies than the determination of individual chemicals in human samples.