Núria Ribas-Fitó

Exposure to hexachlorobenzene during pregnancy increases the risk of overweight in children aged 6 years

Aim: To determine whether prenatal exposure to hexachlorobenzene (HCB) has potential adverse effects on childs weight and body mass index (BMI) in a general population with no local pollution sources.

Prenatal dichlorodiphenyldichloroethylene (DDE) and asthma in children.

Prevalence of asthma increases with increasing dichlorodiphenyldichloroethylene (DDE) levels. However, the effect of early-life exposure, the fundamental window of exposure, is unknown. We assessed the association between prenatal DDE and other organochlorine compounds, and atopy and asthma during infancy. All women presenting for antenatal care in Menorca (Spain) over 12 months starting in mid-1997 were invited to take part in a longitudinal study; 482 children were subsequently enrolled, and 468 (97.1%) provided complete outcome data up to the fourth year of study. Prenatal exposure of organochlorine compounds was measured in cord serum in 405 (83%) children. Asthma was defined on the basis of wheezing at 4 years of age, persistent wheezing, or doctor-diagnosed asthma. We measured specific immunoglobulin-E (IgE) against house dust mite, cat, and grass in sera extracted at 4 years of age. DDE (median = 1.03 ng/mL) was detected in all children, as well as hexachlorobenzene (0.68 ng/mL) and polychlorobiphenyls (0.69 ng/mL). Wheezing at 4 years of age increased with DDE concentration, particularly at the highest quartile [9% in the lowest quartile (< 0.57 ng/mL) vs. 19% in the highest quartile (1.90 ng/mL); relative risk = 2.63 (95% confidence interval 1.19–4.69), adjusting for maternal asthma, breast-feeding, education, social class, or other organochlorines]. The association was not modified by IgE sensitization and occurred with the same strength among nonatopic subjects and among those with persistent wheezing or diagnosed asthma. DDE was not associated with atopy alone. Prenatal exposure to DDE residues may contribute to development of asthma.

Exposure to hexachlorobenzene during pregnancy and children's social behavior at 4 years of age

Background Hexachlorobenzene (HCB) is an organochlorine chemical that has been used in agriculture and industrial processes. Behavioral impairment after HCB exposure has been described in animal models, but little information is available in humans. Objectives Our goal was to study the association of prenatal exposure to HCB with the social behavior of preschool children. Methods Two birth cohorts in Ribera d’Ebre and Menorca (Spain) were set up between 1997 and 1999 (n = 475). The California Preschool Social Competence Scale and the Attention-Deficit Hyperactivity Disorder (ADHD) were scored by each 4-year-old child’s teacher. Organochlorine compounds were measured in cord serum. Children’s diet and parental sociodemographic information were obtained through questionnaire. Results Children with concentrations of HCB > 1.5 ng/mL at birth had a statistically significant increased risk of having poor Social Competence [relative risk (RR) = 4.04; 95% confidence interval (CI), 1.76–9.58] and ADHD (RR = 2.71; 95% CI, 1.05–6.96) scores. No association was found between HCB and the cognitive and psychomotor performance of these children. Conclusions Prenatal exposure to current concentrations of HCB in Spain is associated with a decrease in the behavioral competence at preschool ages. These results should be considered when evaluating the potential neurotoxicologic effects of HCB.

Attention behaviour and hyperactivity at age 4 and duration of breast-feeding.

Aim: The relation of longer duration of breast‐feeding to cognitive development was been demonstrated in several previous studies, however its potential impact on behaviour is unknown. We assess which behavioural areas (executive function, social competence, attention behaviour and hyperactivity) are related to long‐term breast‐feeding in young children.

Maternal use of folic acid supplements during pregnancy and four-year-old neurodevelopment in a population-based birth cohort.

The use of folic acid supplements during very early pregnancy is recommended in order to reduce the incidence of neural tube defects. Little is known about the possible benefits of folic acid on child neurodevelopment. A total of 420 children (87% of those eligible) from a birth cohort had complete data for final analyses at age 4 years. Information about folic acid and other over-the-counter dietary supplements was obtained prospectively using interviewer-administered questionnaires at the end of the first trimester of pregnancy. Psychological outcomes were assessed by two psychologists and teachers 4 years later. Low maternal socio-economic status, smoking, high parity and short duration of breast feeding were associated with lower prevalence of folic acid supplement use. Verbal (b = 3.98, SE = 1.69), motor (b = 4.54, SE = 1.66) and verbal-executive function (b = 3.97, SE = 1.68) scores, social competence (b = 3.97, SE = 1.61) and inattention symptom [OR = 0.46; 95% CI 0.22, 0.95] scores were associated with reported folic acid use. Reported folic acid supplement use during pregnancy was associated with improved neurodevelopment in children after adjusting for a number of sociodemographic and behavioural factors.

Association of Hexachlorobenzene and Other Organochlorine Compounds with Anthropometric Measures at Birth

The aim of the present study was to assess the association of prenatal exposure to hexachlorobenzene (HCB) and other organochlorine compounds with anthropometric measures at birth. A total of 98 mother-infant pairs (83% of all children born in a specific area polluted with HCB in the period 1997–1999) were recruited after giving written consent. Levels of organochlorine compounds were measured in 72 maternal serum samples at delivery and in 70 cord serum samples. Of the organochlorines measured in cord serum, median levels of HCB were higher than for the other compounds (median of HCB = 1.13 ng/mL, median of dichlorodiphenyl dichloroethylene = 0.85 ng/mL, and median of total polychlorinated biphenyls = 0.27 ng/mL). Premature newborns had higher concentrations of HCB [1.94 ng/mL among prematures versus 1.10 among nonprematures (p < 0.10)], dichlorodiphenyl dichloroethylene [2.40 versus 0.80 (p < 0.05)], and polychlorinated biphenyls in cord serum [0.70 versus 0.14 (p < 0.10)]. Those infants born with a small length for gestational age had higher levels of HCB in cord serum than those with an adequate length for gestational age [1.64 ng/mL versus 1.00 ng/mL (p < 0.05)]. In addition, HCB cord serum levels were negatively associated in a dose-response way with crown-heel length [for each doubling of the dose there was a decrease of 0.46 (SE = 0.22) cm] after adjusting for smoking, gestational age, and other organochlorine compounds. The associations of dichlorodiphenyl dichloroethylene and polychlorinated biphenyls with length were not significant. The results did not vary when stratified for prematurity. These data suggest that HCB reduces intrauterine physical linear growth.

Early exposure to dichlorodiphenyldichloroethylene, breastfeeding and asthma at age six

Our aims were to assess association of dichlorodiphenyldichloroethylene (DDE) with childhood asthma measured up to age 6 and the effect of DDE on the protective effect of breastfeeding on asthma. In addition, we attempted to assess the relevant time‐window of DDE exposure (i.e. at birth or at 4 years).

Effects of PCBs, p,p′-DDT, p,p′-DDE, HCB and β-HCH on thyroid function in preschool children

Objective: Several studies have shown that some organochlorine compounds (OCs) can interfere with the thyroid system. As thyroid hormones (THs) are essential for normal brain development, it is important to study the association between THs and OCs during pregnancy and childhood. We have evaluated the relationship between thyroid function and OCs in preschool children. Methods: Children from a general population birth cohort in Menorca (n = 259), Spain were assessed at the age of 4 years. Concentrations of THs (free T4 and total T3), thyrotropin (TSH) and a range of OCs were measured in peripheral blood. Results: Blood levels of dichlorodiphenyl trichloroethane (p,p′-DDT), β-hexachlorocylcohexane (β-HCH), polychlorinated biphenyls (congeners PCB-138, PCB-153 and PCB-118) were related to lower total T3 levels (p<0.05). In addition, free T4 was inversely associated with PCB-118, while no relationship was found between TSH and any of the measured OCs. Conclusions: This study suggests that even at background levels of exposure, OCs may affect the thyroid system, particularly total T3 levels.

Organochlorine compounds and concentrations of thyroid stimulating hormone in newborns.

Aims: To assess the association between prenatal exposure to organochlorine compounds and thyroid status in newborns from an area with high levels of hexachlorobenzene (HCB). Methods: A total of 98 mother-infant pairs (83.1% of all children born during the period 1997–99 in a specific area polluted with HCB) were recruited. Levels of organochlorine compounds were measured in 70 cord serum samples. Concentrations of thyroid stimulating hormone (TSH) were measured in plasma of all newborns three days after birth. Results: All newborns had concentrations of TSH within the range of normal reference values (<25 mU/l). Dichlorodiphenyl dichloroethylene (p,p′DDE), beta-hexachlorocyclohexane (β-HCH), polychlorinated biphenyl (PCB) 138 and 118 were related to higher concentrations of TSH, although only significant for β-HCH. Levels of HCB were not associated with TSH. Conclusions: Although this community is highly exposed to HCB, no association was found between this organochlorine and TSH concentrations at birth.

Concentraciones de compuestos tóxicos persistentes en la población española: el rompecabezas sin piezas y la protección de la salud pública

La contaminacion por compuestos toxicos persistentes (CTP) de la poblacion general es un hecho relevante desde una perspectiva de salud publica. Es, asimismo, importante para el sistema sanitario asistencial y para las politicas ambientales, alimentarias, industriales y economicas. Aunque en Espana los conocimientos sobre la contaminacion de los alimentos por CTP presentan grandes vacios temporales y geograficos, aun es menor la informacion sobre sus concentraciones en las personas: no existe ningun estudio representativo de una poblacion general sana efectuado en una zona geografica amplia. Los estudios disponibles indican que un 80-100% de la poblacion tiene concentraciones detectables de DDE, policlorobifenilos, hexaclorobenceno o lindano. En Espana el numero de estudios sobre los efectos que los CTP tienen en las personas es todavia mas exiguo. Los estudios internacionales sugieren que dosis de algunos CTP por debajo de las que normalmente se consideran «seguras» pueden causar efectos biologicos y clinicos relevantes. Los mecanismos de accion no comprenden solo la disrupcion endocrina. La valoracion de la significacion clinica y social del espectro de efectos mas sutiles y con periodos de latencia mayores de los CTP presenta interesantes retos y oportunidades. Espana y otros paises europeos sufren un deficit de indicadores poblacionales sobre el impacto que los procesos ambientales tienen en la salud humana. Los distintos ambitos de la Administracion deben monitorizar los valores biologicos de los CTPs y valorar sus posibles riesgos para la salud. Junto con mas de cien otros paises, proximamente Espana intentara implementar el Tratado sobre los Contaminantes Organicos Persistentes (Convenio de Estocolmo). Ello constituye un nuevo motivo para desarrollar programas mas eficientes de vigilancia y control de los residuos de los CTP en alimentos, humanos y medio ambiente. Como parte de la aplicacion del Convenio, es necesario iniciar un informe periodico sobre los factores que condicionan las concentraciones internas de CTP en la poblacion general espanola.