Relationship between prenatal exposure to polychlorinated biphenyls and birth weight: A systematic analysis of published epidemiological studies through a standardization of biomonitoring data

Maternal serum dioxin-like activity and gestational age at birth and indices of foetal growth: The Aarhus birth cohort

Human exposure to lipophilic persistent organic pollutants (lipPOP) is ubiquitous and life-long, beginning during foetal development. Exposure to lipPOP elicits a number of species and tissue specific responses including dioxin-like activity which involve the activation of aryl hydrocarbon receptor (AhR). This study aims i) to describe the combined dioxin-like activity in serum from Danish pregnant women collected during 2011-2013; ii) to assess the association between maternal serum dioxin-like activity, gestational age at birth and foetal growth indices. The serum lipPOP fraction was extracted using Solid Phase Extraction and cleaned-up on Supelco multi-layer silica and florisil columns. The combined dioxin-like activity of the extract was determined using the AhR reporter gene bioassay, expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent (TEQ) [AhR-TEQ (pg/g lipid)]. The associations of AhR-TEQ and foetal growth indices (birth weight, birth length and head circumference) and gestational age were assessed by linear regression models. We detected AhR-TEQ in 93.9 % of maternal first trimester serum samples, with a median level of 185 pg/g lipid. Each ln-unit increase in AhR-TEQ was associated with an increase in birth weight of 36 g (95 % CI: 5; 68), birth length of 0.2 cm (95 % CI: 0.01; 0.3) and pregnancy duration of 1 day (95 % CI: 0; 1.5). In women who never smoked, higher AhR-TEQ values were associated with higher birth weight and longer duration of gestation, while in smokers the association was the opposite. Mediation analyses suggested that gestational age may mediate the association of AhR-TEQ with foetal growth indices. We conclude that AhR activating substances are present in the bloodstream of almost all pregnant women in Denmark and the AhR-TEQ level was around four times higher than previously reported. The AhR-TEQ was associated with slightly longer gestational duration and thereby higher birth weight and birth length.

Dioxin-like Activity in Pregnant Women and Indices of Fetal Growth: The ACCEPT Birth Cohort

Exposure to lipophilic persistent organic pollutants (lipPOPs) elicits a number of species- and tissue-specific toxic responses, many of which involve the aryl hydrocarbon receptor (AhR). This study aims to measure the combined serum dioxin-like activity of lipPOPs in Greenlandic Inuit pregnant women and the associations with fetal growth indices. The combined dioxin-like activity of serum lipPOPs extracts was determined using the AhR reporter gene bioassay and expressed as pico-gram (pg) TCDD equivalent (TEQ) per gram serum lipid [AhR-TEQ (pg/g lipid)]. Significant AhR-TEQ was found in >87% of serum samples with the median level of 86.2 pg TEQ/g lipid. The AhR-TEQ level positively correlated with the marine food intake biomarker n-3/n-6 polyunsaturated fatty acids ratio, while negatively correlated with body mass index and parity. Women giving birth to infants with low birth weight (<2500 g) and length (<50 cm) had higher AhR-TEQ level compared to those with normal weight and length infants. For previous smokers, we found significant inverse associations between maternal AhR-TEQ level and fetal growth indices. In conclusion, exposure of Greenlandic Inuit pregnant women to dioxin-like compounds through traditional marine food can adversely influence the fetal growth via induced AhR activity. Smoking might have modifying effects.

Maternal exposure to airborne polychlorinated biphenyls (PCBs) and risk of adverse birth outcomes

Human health effects of airborne lower-chlorinated polychlorinated biphenyls (LC-PCBs) are largely unexplored. Since PCBs may cross the placenta, maternal exposure could potentially have negative consequences for fetal development. We aimed to determine if exposure to airborne PCB during pregnancy was associated with adverse birth outcomes. In this cohort study, exposed women had lived in PCB contaminated apartments at least one year during the 3.6 years before conception or the entire first trimester of pregnancy. The women and their children were followed for birth outcomes in Danish health registers. Logistic regression was performed to estimate odds ratios (OR) for changes in secondary sex ratio, preterm birth, major congenital malformations, cryptorchidism, and being born small for gestational age. We performed linear regression to estimate difference in birth weight among children of exposed and unexposed mothers. All models were adjusted for maternal age, educational level, ethnicity, and calendar time. We identified 885 exposed pregnancies and 3327 unexposed pregnancies. Relative to unexposed women, exposed women had OR 0.97 (95% CI 0.82, 1.15) for secondary sex ratio, OR 1.13 (95% CI 0.76, 1.67) for preterm birth, OR 1.28 (95% CI 0.81, 2.01) for having a child with major malformations, OR 1.73 (95% CI 1.01, 2.95) for cryptorchidism and OR 1.23 (95% CI 0.88, 1.72) for giving birth to a child born small for gestational age. The difference in birth weight for children of exposed compared to unexposed women was − 32 g (95% CI—79, 14). We observed an increased risk of cryptorchidism among boys after maternal airborne LC-PCB exposure, but due to the proxy measure of exposure, inability to perform dose–response analyses, and the lack of comparable literature, larger cohort studies with direct measures of exposure are needed to investigate the safety of airborne LC-PCB exposure during pregnancy

Effects of DDT, DDE, aldrin and dieldrin on prostaglandin, oxytocin and steroid hormone release from smooth chorion explants of cattle

Chlorooganic xenobiotics (XBs) such as DDT, DDE, aldrin and dieldrin interfere with release of hormones from chorionic villi that are necessary for sustaining the normal course pregnancy: prostaglandins (PGs), oxytocin (OT), progesterone (P₄) and estradiol (E₂). Approximately 20 %-40 % of these hormones originate from the smooth chorion. The aim of current studies was to investigate effects of these XBs on synthesis and release of PGE₂, PGF_2α, OT, P₄ and E₂ from explants of smooth chorion of cattle, obtained during the120-150 and 151-180 day gestational period. Explants were incubated with DDT, DDE, aldrin or dieldrin at concentrations of 1 and 10 ng/mL for 24 h, and concentrations of PGE₂, PGF_2α, OT, P₄ and E₂ in post incubation medium and the relative abundances of COX-2, PTGES, AKR1B1, NP-I/OT, PAM, HSD3B, and CYP19A1 mRNA transcripts in tissue explants were determined. The XBs did not have effects on cell viability in explants (P > 0.05), however, there were effects on prostaglandins, OT and P₄ secretion and relative abundance of mRNA transcript for genes encoding the main enzymes involved in synthesis of these hormones (P < 0.05). The XBs that were evaluated did not have effects on E₂ synthesis and secretion (P > 0.05). In summary, XBs evaluated in the present study had effects on the pattern of prostaglandin secretion, and can increase OT and P₄ release from smooth chorion explants. Because XBs inhibit hormonal action throughout the chorion, there is an increase in risk of abortions or premature births in animals.

Environmental contaminants and child's growth

Experimental data have suggested that some contaminants in the environment may increase the risk of obesity. Infants can be exposed to chemicals either prenatally, by trans-placental passage of chemicals, or postnatally by their own diet and by other external pathways (air inhalation, dust, hand-to-mouth exposure) after birth. To provide a review of epidemiological evidence on the association between prenatal exposure to chemicals and prenatal and postnatal growth, we present the literature from systematic review articles and international meta-analyses, when available, or recent research articles when summarizing articles were not available. The most studied contaminants in this field were persistent organic pollutants (e.g. organochlorinated pesticides, polychlorinated biphenyls), non-persistent pollutants (e.g. phthalates, bisphenol A), toxic heavy metals (i.e. cadmium, lead and mercury), arsenic, mycotoxins and acrylamide. Mounting evidence suggests that child's growth may be associated with prenatal or postnatal exposures to environmental contaminants. Improving exposure assessment and studying the contaminants as mixtures should allow to gain knowledge about the environmental determinants of growth and obesity.

[Investigation of the Effects of Exposure to Chemical Substances on Child Health]

There is mounting concern about the effects of early-life exposure to chemical substances on children's health and development. We summarize the past and ongoing birth cohort studies carried out worldwide on the association between environmental exposure and children's health. Our PubMed search with the keywords 'birth cohort' revealed that the number of articles jumped from 200-300 in the 1980s to over 1,000 in the 1990s. Many of these articles reported elevated risks to children's health posed by chemical exposure owing their vulnerability. At the same time, policies implemented to reduce exposure to lead and dioxins were successful in the past few decades. Research also demonstrated that intervention to reduce exposure to certain chemicals whose exposure routes were well documented was also successful. We summarize the effects of early-life exposure to chemical substances on children's health and development. Our findings will hopefully help safeguard the environment in which future generations grow and live.

Prenatal exposure to polychlorinated biphenyls and fetal growth in British girls

Polychlorinated biphenyls (PCBs) are synthetic chemicals that bioaccumulate in the food chain. PCBs were used primarily for industrial applications due to their insulating and fire retardant properties, but were banned in the 1970s in the United States and in the 1980s in the United Kingdom, as adverse health effects following exposure were identified. Previous studies of populations with high PCB exposure have reported inverse associations with birth weight and gestational length. Birth weight is a powerful predictor of infant survival, and low birth weight can predispose infants to chronic conditions in adult life such as diabetes and cardiovascular diseases. Using data from the Avon Longitudinal Study of Parents and Children, we investigated the association between prenatal exposure to PCBs and fetal growth in a sample of 448 mother-daughter dyads. Concentrations of three common PCB analytes, PCB-118, PCB-153 and PCB-187, were measured in maternal serum collected during pregnancy, and fetal growth was measured by birth weight and birth length. Multivariable linear regression was used to examine the associations between PCB analytes and measures of fetal growth, after adjusting for parity, maternal age, pre-pregnancy BMI, educational status, tobacco use and gestational age of infant at sample collection. Birth length, ponderal index and gestational age were not associated with any of the PCB analytes. Mothers' educational status modified associations for PCB analytes with birthweight. We observed significant inverse associations with birth weight only among daughters of mothers with less education. Daughter's birth weight was -138.4 g lower (95% CI: -218.0, -58.9) for each 10 ng/g lipid increase in maternal serum PCB-118. Similarly, every 10 ng/g lipid increase in maternal serum PCB-153 was associated with a -41.9 g (95% CI: -71.6, -12.2) lower birth weight. Every 10 ng/g lipids increase in maternal serum PCB-187, was associated with a -170.4 g (95% CI: -306.1, -34.7) lower birth weight, among girls with mothers in the lowest education group. Our findings suggest that prenatal exposure to PCBs is inversely associated with daughters' birth weight and that mothers' education, which is a possible marker for socioeconomic status, significantly modified the association between maternal PCB concentrations and birth weight in female newborns.

Prenatal exposure to chlordecone, gestational weight gain, and birth weight in a Guadeloupean birth cohort

BACKGROUND

Chlordecone is a persistent organochlorine insecticide with well-defined estrogenic properties. It was intensively used in the French West Indies until 1993 to control the banana root borer. Because of the long-term contamination of soils and water, the population is currently exposed to chlordecone through food consumption. Chlordecone has been found in the blood of pregnant women and in cord blood. It has been shown to be an endocrine-disrupting chemical and exposure during pregnancy may affect fetal growth.

OBJECTIVES

The objective of our study was to examine the association between prenatal exposure to chlordecone and fetal growth based on the TIMOUN birth cohort conducted in Guadeloupe, with a focus on the potential modification of this relationship by maternal body mass index (BMI) and gestational weight gain (GWG).

METHODS

Chlordecone was determined in cord plasma at birth in 593 babies. Birth weight was the indicator of fetal growth. Maternal pre-pregnancy BMI and GWG were determined. Adherence to GWG recommendations of the US Institute of Medicine based on maternal pre-pregnancy BMI was assessed. Birth weight was analyzed relative to cord blood chlordecone levels using linear and non-linear regression models.

RESULTS

Overall chlordecone in cord blood was not associated with birth weight, but we found an interaction between chlordecone exposure with GWG and adherence to GWG recommendations. After stratification by GWG, we found a significant U-shaped association between birth weight and chlordecone exposure, within the upper quartiles of GWG or excessive GWG.

CONCLUSION

Chlordecone exposure may affect fetal growth, particularly when excessive GWG is present.

Organochlorine Compounds and Ultrasound Measurements of Fetal Growth in the INMA Cohort (Spain)

BACKGROUND

Several studies have reported decreases in birth size associated with exposure to organochlorine compounds (OCs), but uncertainties remain regarding the critical windows of prenatal exposure and the effects on fetal body segments.

OBJECTIVE

We examined the relationship between prenatal OC concentrations and fetal anthropometry.

METHODS

We measured 4,4´-dichlorodiphenyldichloroethylene (4,4´-DDE), hexachlorobenzene (HCB), and polychlorinated biphenyl (PCB) congeners (138, 153, and 180) in 2,369 maternal and 1,140 cord serum samples in four Spanish cohorts (2003-2008). We used linear mixed models to obtain longitudinal growth curves for estimated fetal weight (EFW), abdominal circumference (AC), biparietal diameter (BPD), and femur length (FL) adjusted by parental and fetal characteristics. We calculated standard deviation (SD) scores of growth at 0-12, 12-20, and 20-34 weeks of gestation as well as size at gestational week 34 for the four parameters. We studied the association between OCs and the fetal outcomes by cohort-specific linear models and subsequent meta-analyses.

RESULTS

PCBs were associated with a reduction in AC up to mid-pregnancy, and BPD and FL from gestational week 20 onward. An inverse association was also found between HCB and AC growth in early pregnancy. The reduction of these parameters ranged from -4% to -2% for a doubling in the OC concentrations. No association between 4,4´-DDE and fetal growth was observed.

CONCLUSIONS

To our knowledge, this is the first study to report an association between prenatal exposure to some PCBs and HCB and fetal growth: AC during the first two trimesters of pregnancy, and BPD and FL later in pregnancy.

CITATION

Lopez-Espinosa MJ, Murcia M, Iñiguez C, Vizcaino E, Costa O, Fernández-Somoano A, Basterrechea M, Lertxundi A, Guxens M, Gascon M, Goñi-Irigoyen F, Grimalt JO, Tardón A, Ballester F. 2016. Organochlorine compounds and ultrasound measurements of fetal growth in the INMA cohort (Spain). Environ Health Perspect 124:157-163; http://dx.doi.org/10.1289/ehp.1408907.

Effects of in utero exposure to polychlorinated biphenyls, methylmercury, and polyunsaturated fatty acids on birth size

The adverse effects of in utero exposure to polychlorinated biphenyls (PCBs) or methylmercury (MeHg), and the beneficial effects of nutrients from maternal fish intake might have opposing influences on fetal growth. In this study, we assessed the effects of in utero exposure to PCBs and MeHg on birth size in the Japanese population, which is known to have a high frequency of fish consumption. The concentrations of PCBs and polyunsaturated fatty acids in maternal blood, and the total mercury in hair (as a biomarker of MeHg exposure) were measured during pregnancy and at delivery. Maternal intakes of fish (subtypes: fatty and lean) and shellfishes were calculated from a food frequency questionnaire administered at delivery. Newborn anthropometric measurement data were obtained from birth records. The associations between chemical exposures and birth size were analyzed by using multiple regression analysis with adjustment for confounding factors among 367 mother-newborn pairs. The birth weight was 3073±37 g (mean±SD). The incidence of babies small for gestational age (SGA) by weight was 4.9%. The median concentrations of total PCBs and hair mercury were 108 ng/g lipid and 1.41 μg/g, respectively. There was no overall association between mercury concentrations and birth weight, birth length, chest circumference, and head circumference. We observed that the risk of SGA by weight decreased with increasing mercury concentration in regression analyses with adjustment for polyunsaturated fatty acids. Our results suggest that the beneficial effect of essential nutrition may mask the adverse effects of MeHg on birth size. The concentrations of PCBs had no association with birth size.

Prenatal exposure to PCB-153, p,p'-DDE and birth outcomes in 9000 mother-child pairs: exposure-response relationship and effect modifiers

Low-level exposure to polychlorinated biphenyl-153 (PCB-153) and dichlorodiphenyldichloroethylene (p-p'-DDE) can impair fetal growth; however, the exposure-response relationship and effect modifiers of such association are not well established. This study is an extension of an earlier European meta-analysis. Our aim was to explore exposure-response relationship between PCB-153 and p-p'-DDE and birth outcomes; to evaluate whether any no exposure-effect level and susceptible subgroups exist; and to assess the role of maternal gestational weight gain (GWG). We used a pooled dataset of 9377 mother-child pairs enrolled in 14 study populations from 11 European birth cohorts. General additive models were used to evaluate the shape of the relationships between organochlorine compounds and birth outcomes. We observed an inverse linear exposure-response relationship between prenatal exposure to PCB-153 and birth weight [decline of 194g (95% CI -314, -74) per 1μg/L increase in PCB-153]. We showed effects on birth weight over the entire exposure range, including at low levels. This reduction seems to be stronger among children of mothers who were non-Caucasian or had smoked during pregnancy. The most susceptible subgroup was girls whose mothers smoked during pregnancy. After adjusting for absolute GWG or estimated fat mass, a reduction in birth weight was still observed. This study suggests that the association between low-level exposure to PCB-153 and birth weight exists and follows an inverse linear exposure-response relationship with effects even at low levels, and that maternal smoking and ethnicity modify this association.

Growth in Inuit children exposed to polychlorinated biphenyls and lead during fetal development and childhood

BACKGROUND

Because of their geographical location and traditional lifestyle, Canadian Inuit children are highly exposed to polychlorinated biphenyls (PCBs) and lead (Pb), environmental contaminants that are thought to affect fetal and child growth. We examined the associations of these exposures with the fetal and postnatal growth of Inuit children.

METHODS

We conducted a prospective cohort study among Inuit from Nunavik (Arctic Québec). Mothers were recruited at their first prenatal visit; children (n=290) were evaluated at birth and at 8-14 years of age. Concentrations of PCB 153 and Pb were determined in umbilical cord and child blood. Weight, height and head circumference were measured at birth and during childhood.

RESULTS

Cord blood PCB 153 concentrations were not associated with anthropometric measurements at birth or school age, but child blood PCB 153 concentrations were associated with reduced weight, height and head circumference during childhood. There was no association between cord Pb levels and anthropometric outcomes at birth, but cord blood Pb was related to smaller height and shows a tendency of a smaller head circumference during childhood.

INTERPRETATION

Our results suggest that chronic exposure to PCBs during childhood is negatively associated with skeletal growth and weight, while prenatal Pb exposure is related to reduced growth during childhood. This study is the first to link prenatal Pb exposure to poorer growth in school-age children.

Ten years of progress in the Hokkaido birth cohort study on environment and children's health: cohort profile--updated 2013

The Hokkaido Study on Environment and Children's Health is an ongoing cohort study that began in 2002. The study consists of two prospective birth cohorts, the Sapporo cohort (n = 514) and the Hokkaido large-scale cohort (n = 20,940). The primary goals of this study are to first examine the potential negative effects of perinatal environmental chemical exposures on birth outcomes, including congenital malformations and growth retardation; second, to evaluate the development of allergies, infectious diseases and neurodevelopmental disorders and perform longitudinal observations of the children's physical development to clarify the causal relationship between these outcomes and environmental chemicals; third, to identify individuals genetically susceptible to environmental chemicals; finally, to identify the additive effects of various environmental factors in our daily life, such as secondhand smoke exposure or low folate intake during early pregnancy. In this paper, we introduce our recent progress in the Hokkaido study with a cohort profile updated in 2013. For the last ten years, we followed pregnant women and their offspring, measuring various environmental chemicals, i.e., PCB, OH-PCB and dioxins, PFCs (Perfluorinated Compounds), Organochlorine pesticides, Phthalates, bisphenol A and mercury. We discovered that the concentration of toxic equivalents (TEQ) of dioxin and other specific congeners of PCDF or PCDD have effects on birth weight, infants' neurodevelopment and immune function. There were significant gender differences in these effects; our results suggest that male infants have more susceptibility to those chemical exposures than female infants. Interestingly, we found maternal genetic polymorphisms in AHR, CYP1A1 or GSTs that significantly modified the dioxin concentrations in maternal blood, suggesting different dioxin accumulations in the bodies of individuals with these genotypes, which would lead to different dioxin exposure levels. These genetic susceptibility factors influenced the body size of children born from mothers that either smoked or were passively exposed to tobacco smoke. Further studies investigating the correlation between epigenetics, the effects of intrauterine exposure to environmental chemicals and developmental factors related to health and disease are warranted.

Persistent organic pollutants exposure during pregnancy, maternal gestational weight gain, and birth outcomes in the mother-child cohort in Crete, Greece (RHEA study)

BACKGROUND

Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs) and pesticides bioaccumulate through the food chain and cross the placenta. POPs are developmental toxicants in animals but the epidemiological evidence on pregnancy outcomes is inconsistent. Maternal gestational weight gain has been recently suggested as a key factor explaining the association between PCBs with lower birth weight.

AIMS

We examined whether in utero exposure to current low levels of different POPs is associated with fetal growth and gestational age in a mother-child cohort in Crete, Greece (Rhea study), and evaluated specifically whether maternal gestational weight gain may affect this association.

METHODS

We included 1117 mothers and their newborns from the Rhea study. Mothers were interviewed and blood samples collected during the first trimester of pregnancy. Information on birth outcomes was retrieved from medical records. Concentrations of several PCBs, other organochlorine compounds (dichlorodiphenyl dichloroethene [DDE], dichlorodiphenyl trichloroethane [DDT] and hexachlorobenzene [HCB]) and one polybrominated diphenyl ether congener (tetra-bromodiphenyl ether [BDE-47]), were determined in maternal serum by triple quadrupole mass spectrometry. Multiple linear regression models were used to investigate the associations of birth weight, gestational age, and head circumference with each compound individually on the log10 scale, and with combined exposures through the development of an exposure score.

RESULTS

In multivariate models, birth weight was negatively associated with increasing levels of HCB (β=-161.1g; 95% CI: -296.6, -25.7) and PCBs (β=-174.1g; 95% CI: -332.4, -15.9); after further adjustment for gestational weight gain these estimates were slightly reduced (β=-154.3g; 95% CI: -300.8, -7.9 for HCB and β=-135.7g; 95% CI: -315.4, 43.9 for PCBs). Furthermore, in stratified analysis, the association between POPs and birth weight was only observed in women with inadequate or excessive gestational weight gain. Small, negative associations were observed with head circumference while no association was observed with gestational age.

CONCLUSIONS

The findings suggest that prenatal exposure to PCBs and HCB impairs fetal growth and adds to the growing literature that demonstrates an association between low-level environmental pollutant exposure and fetal growth. Furthermore our results suggest that the association of POPs, maternal gestational weight gain and birth weight is probably more complex than that previously hypothesized.

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

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 (μg PCBMPEQ kg(-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<1000 μg PCBMPEQ kg(-1) lipids) appears low according to this systematical analysis.

Maternal dietary intake of dioxins and polychlorinated biphenyls and birth size in the Norwegian Mother and Child Cohort Study (MoBa)

Maternal diet not only provides essential nutrients to the developing fetus but is also a source of prenatal exposure to environmental contaminants. We investigated the association between dietary intake of dioxins and PCBs during pregnancy and birth size. The study included 50,651 women from the Norwegian Mother and Child Cohort Study (MoBa). Dietary information was collected by FFQs and intake estimates were calculated by combining food consumption and food concentration of dioxins, dioxin-like PCBs and non-dioxin-like PCBs. We used multivariable regression models to estimate the association between dietary intake of dioxins and PCBs and fetal growth. The contribution of fish and seafood intake during pregnancy was 41% for dietary dioxins and dioxin-like PCBs and 49% for dietary non-dioxin-like PCBs. Further stratified analysis by quartiles of seafood intake during pregnancy was conducted. We found an inverse dose-response association between dietary intake of dioxins and PCBs and fetal growth after adjustment for confounders. Newborns of mothers in the upper quartile of dioxin and dioxin-like PCBs intake had 62g lower birth weight (95% CI: -73, -50), 0.26cm shorter birth length (95% CI: -0.31, -0.20) and 0.10cm shorter head circumference (95% CI: -0.14, -0.06) than newborns of mothers in the lowest quartile of intake. Similar negative associations for intake of dioxins and dioxin-like PCBs were found after excluding women with intakes above the tolerable weekly intake (TWI=14pg TEQ/kg bw/week). The negative association of dietary dioxins and PCBs with fetal growth was weaker as seafood intake was increasing. No association was found between dietary dioxin and PCB intake and the risk for small-for-gestational age neonate. In conclusion, dietary intakes of dioxins and PCBs during pregnancy were negatively associated with fetal growth, even at intakes below the TWI.

Making sense of OMICS data in population-based environmental health studies

Although experience from the application of OMICS technologies in population-based environmental health studies is still relatively limited, the accumulated evidence shows that it can allow the identification of features (genes, proteins, and metabolites), or sets of such features, which are targeted by particular exposures or correlate with disease risk. Such features or profiles can therefore serve as biomarkers of exposure or disease risk. Blood-based OMIC profiles appear to reflect to some extent events occurring in target tissues and are associated with toxicity or disease and therefore have the potential to facilitate the elucidation of exposure-disease relationships. Further progress in this direction requires better understanding of the significance of exposure-induced network perturbations for disease initiation and progression and the development of a framework that combines agnostic searches with the utilization of prior knowledge, taking account of particular elements which characterize the structure and evolution of complex systems and brings in principles of systems biology.

Systematic analysis of the relationship between standardized prenatal exposure to polychlorinated biphenyls and mental and motor development during follow-up of nine children cohorts

Impact of prenatal exposure to polychlorinated biphenyls (PCBs) on mental and motor development has been investigated in various children cohorts, but findings show temporal inconsistencies. Because a direct comparison of results obtained from different cohorts remains difficult, temporal relationship between biological PCB concentrations and long-term developmental effects is still not clearly established. The objective of this research was to use a procedure previously developed to standardize PCB biological concentration data across cohorts in order to perform a systematic analysis of temporal associations between prenatal PCB exposure and mental and motor development from neonatal period (or a young age) until school age. Prenatal exposure data from nine cohorts were standardized in terms of total PCBs per kg of lipids in maternal plasma. Systematic analysis of the "standardized biological concentration-development" relationship during follow-up of each cohort was then conducted through the application of Hill criteria. This led to retain six of the studied cohorts in the final analysis. A biological level of prenatal PCB exposure below which risk of mental or motor development should be negligible was established in the order of 1000μg/kg of lipids in maternal plasma.