In-utero exposure to dichlorodiphenyltrichloroethane and cognitive development among infants and school-aged children

Impact of antenatal exposure to a mixture of persistent organic pollutants on intellectual development

OBJECTIVE

Strong experimental evidence exists that several endocrine disrupting chemicals (EDCs) have neurobehavioral toxicity. However, evidence of associations between prenatal exposure and child's cognitive development is inconsistent. Moreover, toxicants are generally analyzed one by one without considering aggregate effects. We examined here the impact of a prenatal exposure to a mixture of persistent organic pollutants (POPs) on intellectual abilities in preschool children, and compared their effects to those described in the literature.

METHODS

Sixty-two children were included in a longitudinal cohort. Four organochlorine pesticides, four polychlorinated biphenyls (PCBs) and seven perfluorinated compounds (PFCs) were measured in cord blood. Intellectual abilities were assessed at 6 years of age using the Wechsler Preschool and Primary Scale of Intelligence 4th ed. (WPPSI-IV). We examined the associations between a mixture of POPs and cognitive performances using principal components approach (PCA) and weighted quantile sum (WQS) regression taking sex difference into account.

RESULTS

No negative correlation was found when analyses were performed on boys and girls together. In sex-stratified analyses, lower scores in full scale intelligence quotient (FSIQ) and fluid reasoning index (FRI) were observed in boys most exposed to a mixture of POPs. Increase of the WQS index was also associated with lower verbal comprehension index (VCI) scores in girls only. No other negative correlation was found using both WQS and PCA models.

CONCLUSION

Our study suggests deleterious associations between antenatal exposure to a mixture of POPs and sex-specific cognitive level, clarifying some trends described in the literature.

Pesticides: An alarming detrimental to health and environment

Pesticides are chemical substances of natural or synthetic origin that are used to eradicate pests and insects. These are indispensable in the agricultural processes for better crop production. Pesticide use aims to promote crop yield and protect the crops from diseases and damage. Pesticides must be handled carefully and disposed of appropriately because they are dangerous to people and other species by default. Environmental pollution occurs when pesticide contamination spreads away from the intended plants. Older pesticides such as lindane and dichlorodiphenyltrichloroethane (DDT) may remain in water and soil for a longer time. These accumulate in various parts of the food chain and cause damage to the ecosystem. Biological techniques in the management of pest control such as importation, augmentation, and conservation, and the accompanying procedures are more efficient, less expensive, and ecologically sound than other ways. This review mainly focuses on the consequences on the targeted and non-targeted organisms including the health and well-being of humans by the use of pesticides and their toxicity. The side effects that occur when a pesticide's LD50 exceeds the accepted limit through oral or skin penetration due to their binding to various receptors such as estrogen receptors, GABA, EGFR, and others. These pesticide classes include carbamates, pyrethroids, organochlorides, organophosphorus, and others. The current study seeks to highlight the urgent requirement for a novel agricultural concept that includes a major reduction in the use of chemical pesticides.

Dichlorodiphenyltrichloroethane for Malaria and Agricultural Uses and Its Impacts on Human Health

Pesticides are widely used in agriculture and disease control, and dichlorodiphenyltrichloroethane (DDT) is one of the most used pesticides in human history. Besides its significant contributions in pest control in agriculture, DDT was credited as having saved millions of human lives for controlling malaria and other deadly insect-transmitted diseases. Even today, the use of DDT in some countries for malaria control cannot be replaced without endangering people who live there. The recent COVID-19 pandemic has changed our lives and reminded us of the challenges in dealing with infectious diseases, especially deadly ones including malaria. However, DDT and its metabolites are stable, persist long, are found in almost every corner of the world, and their persistent effects on humans, animals, and the environment must be seriously considered. This review will focus on the history of DDT use for agriculture and malaria control, the pathways for the spread of DDT, benefits and risks of DDT use, DDT exposure to animals, humans, and the environment, and the associated human health risks. These knowledge and findings of DDT will benefit the selection and management of pesticides worldwide.

Neurobehavioral Effects of Low-Dose Chronic Exposure to Insecticides: A Review

The modes of action of insecticides frequently involve a neurotoxic effect; therefore, the study of neurotoxic effects caused by long-term and low-dose insecticide exposure is of particular interest. This study looks at whether or not new studies conducted after 2009 and up to 2021 have provided new evidence for a better understanding of the actual neurobehavioral risk associated with long-term insecticide exposure. We selected and reviewed studies carried out on the neurobehavioral effects of neurotoxic insecticides (organophosphates and/or carbamates, pyrethroids, multiple or undefined insecticides, and organochlorines) considering occupational and non-occupational exposures. The articles were also scored and ranked based on seven parameters. Eighty-six studies were chosen for a final review process from among the 950 scientific papers identified. Twenty-six addressed occupational exposure and six environmental exposure. Among the latter group of studies, 17 focused on rural residents, to be assumed exposed because of living in rural areas, and 43 on the general population. Pending doubts have not been resolved in the last ten years due to the presence of contradictory and hardly comparable results and the fact that in most of the studies showing an evident neurobehavioral impairment the frequent presence of a previous episode of poisoning and hospitalization, with severe brain hypoxia, impaired the possibility of confirming the presence of a causal association with insecticide exposure. Interestingly, the most severely exposed groups, such as applicators who did not wear personal protective equipment, performed worse on neurobehavioral tests. As for residential exposure, there is sufficient evidence to suggest that prenatal OP exposure may increase the risk of ADHD in children.

Exposure to DDT and DDE and functional neuroimaging in adolescents from the CHAMACOS cohort

BACKGROUND

Epidemiological studies suggest that exposure to p,p'-dichloro-diphenyl-trichloroethane (p,p'-DDT) is associated with poorer cognitive function in children and adolescents, but the neural mechanisms underlying this association remain unclear.

OBJECTIVE

We investigated associations of prenatal and childhood exposure to p,p'-DDT and its metabolite p,p'-dichloro-diphenyl-dichloroethylene (p,p'-DDE) with cortical activation in adolescents using functional near-infrared spectroscopy (fNIRS).

METHODS

We administered fNIRS to 95 adolescents from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) aged 15-17 years. We assessed cortical activity in the frontal, temporal, and parietal brain regions while participants completed tasks of executive function, language comprehension, and social cognition. We measured serum p,p'-DDT and -DDE concentrations at age 9 years and then estimated exposure-outcome associations using linear regression models adjusted for sociodemographic characteristics. In secondary analyses, we back-extrapolated prenatal concentrations using prediction models and examined their association with cortical activation.

RESULTS

Median (P25-P75) p,p'-DDT and -DDE concentrations in childhood were 1.4 (1-2.3) and 141.5 (75.0-281.3) ng/g lipid, respectively. We found that childhood exposure to p,p'-DDT and -DDE was associated with altered patterns of brain activation during tasks of cognition and executive functions. For example, we observed increased activity in the left frontal lobe during a language comprehension task (β per 10 ng/g lipid increase of serum p,p'-DDE at age 9 years = 3.4; 95% CI: 0.0, 6.9 in the left inferior frontal lobe; and β = 4.2; 95% CI: 0.9, 7.5 in the left superior frontal lobe). We found no sex differences in the associations of childhood p,p'-DDT and -DDE concentrations with neural activity. Associations between prenatal p,p'-DDT and p,p'-DDE concentrations and brain activity were similar to those observed for child p,p'-DDT and -DDE concentrations.

CONCLUSIONS

Childhood p,p'-DDT and -DDE exposure may impact cortical brain activation, which could be an underlying mechanism for its previously reported associations with poorer cognitive function.

Urinary Pesticide Residual Levels and Acute Respiratory Infections in Children Under 5 Years of Age: Findings From the Offinso North Farm Health Study

BACKGROUND

Several environmental factors are associated with the risk of acute lower respiratory infections (ALRIs) and upper respiratory infections (URIs) in children under 5 years of age (YOA). Evidence implicating chemical pesticides remains equivocal. There are also no data on this subject in these children in Ghana. This study investigated the association between urinary pesticide residual levels and the risk for ALRIs/URIs in children under 5 YOA.

METHODS

The participants for this study were from the Offinso North Farm Health Study, a population-based cross-sectional study. Two hundred and fifty four parents/guardians who had answered affirmatively to the question "Has your child ever accompanied you to the farm?" were interviewed on household socio-demographic and environmental factors, being breastfed, child education, age, gender, and respiratory infection. One hundred fifty children were randomly selected to provide the first void urine.

RESULTS

The proportion of children with ALRI was 22.1% and those with URI was 35.8%. We observed a statistically significant exposure-response relation of p,p'-DDE (tertile) with ALRI (1.7-3.2 µg/L urine: prevalence ratio [PR] = 1.22 [1.05-1.70], ⩾3.2 µg/L urine: 1.50 [1.07-3.53] [P-for trend = .0297]). This observation was in children older than two YOA (P-for trend = .0404). Delta-HCH and beta-HCH (2-levels) were significantly associated with ALRI but not URI. The risk of ALRI increased with deltamethrin levels in an exposure-response manner (2.5-9.5 µg/L urine: 2.10 [1.37-3.24], ⩾9.5 µg/L urine: 4.38 [1.87-10.32] [P-for trend = .0011]) and this was also observed in children older than two YOA. Similar observation was noted for URI. Bifenthrin (>0.5 µg/L urine) was positively associated with ALRI and URI whereas permethrin (⩾1.2 µg/L urine) was not associated only with URI.

CONCLUSIONS

The present study supports the hypothesis that exposure to chemical pesticides is associated with respiratory infections in children under 5 YOA.

Moving up but not getting ahead: Family socioeconomic position in pregnancy, social mobility, and child cognitive development in the first seven years of life

Objectives

Understanding when and how socioeconomic position (SEP) influences cognitive development is key to reducing population inequalities in health and achievement. The objective of this study was to determine the unique association between prenatal family SEP and child cognitive development, and to determine whether marked postnatal social mobility was associated with improvements in child cognitive performance to age 7.

Methods

Data were from children enrolled in the US National Collaborative Perinatal Project (NCPP) (n = 28,761) during 1959-1965, a dataset large enough to observe marked mobility, which remains uncommon. Multivariable linear regression was used to examine the relationship between SEP (i.e., parental income, education, occupation) during gestation and cognitive performance at 8 months (Bayley Scales of Infant Development Mental Development Index) and at 7 years (Wechsler Intelligence Scale for Children).

Results

Holding demographic and perinatal factors constant, family SEP during gestation was not associated with cognitive performance at 8 months (B = -0.03, 95% CI: -0.07-0.01) but was positively associated with performance at 7 years even after accounting for SEP at 7 years (B = 1.28, 95% CI: 1.11-1.45). Children whose families experienced the most extreme upward mobility (from the lowest to highest income quartile) showed a 12 percentile increase in cognitive performance in the first 7 years of life. Those with the most extreme downward mobility (from the highest to lowest income quartile) still experienced an 8 percentile increase in cognitive performance in this interval.

Conclusions

The proportion of children in poverty today is similar to 1965 and intergenerational mobility has declined markedly. Prenatal SEP may contribute to inequalities in child cognitive performance that even extraordinary social mobility cannot erase. To optimize cognitive development across generations, current means-tested programs to support families with young children should be supplemented by universal approaches to ensure access to opportunity before young people become parents.

Wrong place, wrong time: The long-run effects of in-utero exposure to malaria on educational attainment

This paper investigates the long-term relationship between early life exposure to malaria and human capital accumulation in Brazil. The identification strategy relies on exogenous variation in the risk of malaria outbreaks in different states and seasons of the year to identify in utero exposure according to the timing and location of birth. I find consistent negative treatment effects of in utero exposure to malaria on educational attainment. The effects are stronger for exposure during the first trimester of pregnancy than during other periods of gestation. Effective anti-malaria policies can, thus, be an important factor contributing to reducing the educational inequality by targeting pregnant women, especially those in their first months of gestation.

Markers of acute toxicity of DDT exposure in pancreatic beta-cells determined by a proteomic approach

Many compounds have the potential to harm pancreatic beta-cells; organochlorine pollutants belong to those compounds. In this work, we aimed to find markers of acute toxicity of p,p'-DDT exposure among proteins expressed in NES2Y human pancreatic beta-cells employing 2-D electrophoresis. We exposed NES2Y cells to a high concentration (150 μM, LC96 after 72 hours) of p,p'-DDT for 24 and 30 hours and determined proteins with changed expression using 2-D electrophoresis. We have found 22 proteins that changed their expression. They included proteins involved in ER stress (GRP78, and endoplasmin), mitochondrial proteins (GRP75, ECHM, IDH3A, NDUS1, and NDUS3), proteins involved in the maintenance of the cell morphology (EFHD2, TCPA, NDRG1, and ezrin), and some other proteins (HNRPF, HNRH1, K2C8, vimentin, PBDC1, EF2, PCNA, biliverdin reductase, G3BP1, FRIL, and HSP27). The proteins we have identified may serve as indicators of p,p'-DDT toxicity in beta-cells in future studies, including long-term exposure to environmentally relevant concentrations.

Review of the Effects of Perinatal Exposure to Endocrine-Disrupting Chemicals in Animals and Humans

Maternal exposure to endocrine-disrupting chemicals (EDCs) is associated with long-term hormone-dependent effects that are sometimes not revealed until maturity, middle age, or adulthood. The aim of this study was to conduct descriptive reviews on animal experimental and human epidemiological evidence of the adverse health effects of in utero and lactational exposure to selected EDCs on the first generation and subsequent generation of the exposed offspring. PubMed, Web of Science, and Toxline databases were searched for relevant human and experimental animal studies on 29 October 29 2018. Search results were screened for relevance, and studies that met the inclusion criteria were evaluated and qualitative data extracted for analysis. The search yielded 73 relevant human and 113 animal studies. Results from studies show that in utero and lactational exposure to EDCs is associated with impairment of reproductive, immunologic, metabolic, neurobehavioral, and growth physiology of the exposed offspring up to the fourth generation without additional exposure. Little convergence is seen between animal experiments and human studies in terms of the reported adverse health effects which might be associated with methodologic challenges across the studies. Based on the available animal and human evidence, in utero and lactational exposure to EDCs is detrimental to the offspring. However, more human studies are necessary to clarify the toxicological and pathophysiological mechanisms underlying these effects.

Selenium status in lactating mothers-infants and its potential protective role against the neurotoxicity of methylmercury, lead, manganese, and DDT

A total of 206 lactating mothers and their infants (3-12 months) were included in this study to evaluate postnatal exposure to neurotoxic pollutants such as methylmercury (MeHg), lead (Pb), manganese (Mn), dichlorodiphenyltrichloroethane (DDT) and its metabolites [dichlorodiphenyldichloroethane (DDD), and dichlorodiphenyldichloroethylene (DDE)] and their association with delayed neurological development and to explore the protective role of selenium (Se) against chemical neurotoxicity. Neurodevelopmental performance was evaluated using Denver Developmental Screening Test II and Parents' Evaluation of Developmental Status (PEDS). Multivariate log-binomial regression modeling was applied for both single and multiple exposures to chemicals using a principal component analysis that generated six principal components. Both mothers and their infants had been exposed to metals and DDT metabolites, with some exceeding the accepted permissible limits. The geometric means of MeHg, Pb, Mn, DDD, DDE and DDT levels in breast milk were 1.333, 45.327, 15.576, 0.069, 0.542 and 1.08 μg/l, respectively. A single-exposure model identified a high risk of reduced PEDS performance significantly associated with DDD in breast milk [relative risk (RR) = 1.484; 95% confidence interval (95%CI) = 1.091-2.019] and marginally significantly associated with Pb in the mothers' blood (RR = 2.164; 95%CI = 0.87-5.382). We did not find a protective role of Se in neurodevelopment due to its high levels in the mothers. Models of multi-chemical exposure indicated that Mn in blood and breast milk, Se in blood and Pb in the mothers' urine were marginally significantly associated with a high risk of reduced PEDS performance (RR = 0.424; 95%CI = 0.176-1.022). The use of multi-chemical exposure approach in early life risk assessments is important because it indicates real-world exposure. Our results were not conclusive because the sample size was small, so future studies examining the implications to health of the impact of prenatal/postnatal exposure to a mixture of chemicals in the Saudi population are merited.

Serum concentrations and detection rates of selected organochlorine pesticides in a sample of Greek school-aged children with neurodevelopmental disorders

Prospective studies indicate that the exposure to organochlorine pesticides (OCPs) during fetal life, infancy, and early childhood may be associated with features of neurodevelopmental disorders in children. However, few studies have investigated the concentrations of serum OCPs in children with categorically diagnosed neurodevelopmental disorders. The aim of this study was to assess the concentrations and detection rates of dichlorodiphenyltrichloroethane (DDT) metabolites, hexachlorocyclohexane (HCH) isomers, cyclodienes, and methoxychlor in serum samples of children with autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and specific learning disorder (SLD), all of normal intelligence, compared to typically developing controls (TD). In total, 114 schoolchildren, aged 6-13 years old, were assessed and distributed into four groups: ASD (n = 39), ADHD (n = 21), SLD (n = 32), and TD (n = 18). Each clinical group was compared to the TD group. Concentrations of serum OCPs were determined by gas chromatography and are presented as ng/g lipid. Concentrations of β-HCH, the sum of HCH isomers, and o,p'-DDD were significantly higher in ASD children: ASD vs. TD (mean ± SD): 10.5 ± 7.7 vs. 6.1 ± 4.0, (p = 0.049); 12.0 ± 10.3 vs. 6.6 ± 4.0, (p = 0.025); 7.4 ± 6.5 vs. 2.8 ± 2.3, (p = 0.0019), respectively. The detection rates of p,p'-DDT, at least one substance from DDTs detected, and the cyclodiene heptachlor epoxide, were significantly lower in the ASD group: ASD vs. TD: 12.8% vs. 38.9%, (p = 0.037); 69.2% vs. 94.4%, (p = 0.044); 10.3% vs. 38.9%, (p = 0.026), respectively. No significant differences between the ADHD or SLD groups and the TD group were observed. We demonstrated higher serum concentrations and lower detection rates of selected OCPs in ASD than TD children. Our results add to potential neurodevelopmental concerns surrounding OCPs and provide evidence of specificity in the relations between HCHs and ASD.

Association of Maternal Insecticide Levels With Autism in Offspring From a National Birth Cohort

OBJECTIVE

Autism is a complex neurodevelopmental disorder with a largely unknown etiology. To date, few studies have investigated prenatal exposure to toxins and risk of autism by using maternal biomarkers of exposure. Persistent organic pollutants are lipophilic halogenated organic compounds and include the insecticide dichlorodiphenyltrichloroethane (DDT), as well as its metabolite p,p'-dichlorodiphenyl dichloroethylene (p,p'-DDE), and polychlorinated biphenyls (PCBs). The objective of this study was to test whether elevated maternal levels of persistent organic pollutants are associated with autism among offspring.

METHOD

The investigation was derived from the Finnish Prenatal Study of Autism, a national birth cohort study based on a nested case-control design. Cases of autism among children born between 1987 and 2005 were ascertained by national registry linkages. In cases of childhood autism and matched control subjects (778 matched case-control pairs), maternal serum specimens from early pregnancy were assayed for levels of p,p'-DDE and total levels of PCBs.

RESULTS

The odds of autism among offspring were significantly increased with maternal p,p'-DDE levels that were in the highest 75th percentile, with adjustment for maternal age, parity, and history of psychiatric disorders (odds ratio=1.32, 95% CI=1.02, 1.71). The odds of autism with intellectual disability were increased by greater than twofold with maternal p,p'-DDE levels above this threshold (odds ratio=2.21, 95% CI=1.32, 3.69). There was no association between total levels of maternal PCBs and autism.

CONCLUSIONS

These findings provide the first biomarker-based evidence that maternal exposure to insecticides is associated with autism among offspring. Although further research is necessary to replicate this finding, this study has implications for the prevention of autism and may provide a better understanding of its pathogenesis.

Prenatal Exposure to DDT and Pyrethroids for Malaria Control and Child Neurodevelopment: The VHEMBE Cohort, South Africa

BACKGROUND

Although indoor residual spraying (IRS) with dichlorodiphenyltrichloroethane (DDT) and pyrethroids effectively controls malaria, it potentially increases human exposure to these insecticides. Previous studies suggest that prenatal exposure to these insecticides may impact human neurodevelopment.

OBJECTIVES

We aimed to estimate the effects of maternal insecticide exposure and neurodevelopment of toddlers living in a malaria-endemic region currently using IRS.

METHODS

The Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) is a birth cohort of 752 mother-child pairs in Limpopo, South Africa. We measured maternal exposure to DDT and its breakdown product, dichlorodiphenyldichloroethylene (DDE), in maternal serum, and measured pyrethroid metabolites in maternal urine. We assessed children's neurodevelopment at 1 and 2 y of age using the Bayley Scales of Infant Development, third edition (BSID-III), and examined associations with maternal exposure.

RESULTS

DDT and DDE were not associated with significantly lower scores for any BSID-III scale. In contrast, each 10-fold increase in cis-DCCA, trans-DCCA, and 3-phenoxybenzoic acid were associated, respectively, with a -0.63 (95% CI: -1.14, -0.12), -0.48 (95% CI: -0.92, -0.05), and -0.58 (-1.11, -0.06) decrement in Social-Emotional scores at 1 y of age. In addition, each 10-fold increase in maternal cis-DBCA levels was associated with significant decrements at 2 y of age in Language Composite scores and Expressive Communication scores [β=-1.74 (95% CI: -3.34, -0.13) and β=-0.40 (95% CI: -0.77, -0.04), respectively, for a 10-fold increase]. Significant differences by sex were estimated for pyrethroid metabolites and motor function scores at 2 y of age, with higher scores for boys and lower scores for girls.

CONCLUSIONS

Prenatal exposure to pyrethroids may be associated at 1 y of age with poorer social-emotional development. At 2 y of age, poorer language development was observed with higher prenatal pyrethroid levels. Considering the widespread use of pyrethroids, these findings deserve further investigation. https://doi.org/10.1289/EHP2129.

Levels and Determinants of DDT and DDE Exposure in the VHEMBE Cohort

BACKGROUND

Although indoor residual spraying (IRS) is an effective tool for malaria control, its use contributes to high insecticide exposure in sprayed communities and raises concerns about possible unintended health effects.

OBJECTIVE

The Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) is a birth cohort study initiated in 2012 to characterize prenatal exposure to IRS insecticides and exposures' impacts on child health and development in rural South Africa.

METHODS

In this report, we describe the VHEMBE cohort and dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) serum concentrations measured in VHEMBE mothers when they presented for delivery. In addition, we applied a causal inference framework to estimate the potential reduction in population-level p,p'-DDT and p,p'-DDE serum concentrations under five hypothetical interventions. A total of 751 mothers were enrolled.

RESULTS

Serum concentrations of p,p' isomers of DDT and DDE were above the limit of detection (LOD) in ≥98% of the samples, whereas the o,p' isomers were above the LOD in at least 80% of the samples. Median (interquartile range) p,p'-DDT and p,p'-DDE serum concentrations for VHEMBE cohort participants were 55.3 (19.0-259.3) and 242.2 (91.8-878.7) ng/g-lipid, respectively. Mothers reporting to have lived in a home sprayed with DDT for malaria control had ~5-7 times higher p,p'-DDT and p,p'-DDE serum concentrations than those who never lived in a home sprayed with DDT. Of the five potential interventions tested, we found increasing access to water significantly reduced p,p'-DDT exposure and increasing the frequency of household wet mopping significantly reduced p,p'-DDT and p,p'-DDE exposure.

CONCLUSION

Our findings suggest that several intervention approaches may reduce DDT/DDE exposure in pregnant women living in IRS communities. https://doi.org/10.1289/EHP353.

Prenatal exposure to persistent organic pollutants in association with offspring neuropsychological development at 4years of age: The Rhea mother-child cohort, Crete, Greece

BACKGROUND

Persistent Organic Pollutants (POPs) are highly-resistant compounds to environmental degradation and due to fat solubility they bioaccumulate through the food chain. As they cross the placenta, in utero exposure to POPs could disrupt child neurodevelopment as they are considered to be neurotoxic.

AIMS

We examined whether in utero exposure to levels of different POPs is associated with offspring cognitive and behavioral outcomes at 4years of age in a mother-child cohort in Crete, Greece (Rhea study).

METHODS

We included 689 mother-child pairs. Concentrations of several polychlorinated biphenyls (PCBs) and other organochlorine compounds (dichlorodiphenyl dichloroethene [DDE], hexachlorobenzene [HCB]) were determined in maternal serum collected in the first trimester of pregnancy by triple quadrupole mass spectrometry. Neurodevelopment at 4years was assessed by means of the McCarthy Scales of Children's Abilities. Behavioral difficulties were assessed by Strengths and Difficulties Questionnaire and Attention Deficit Hyperactivity Disorder Test. Linear regression analyses were used to estimate the associations between the exposures and outcomes of interest after adjustment for potential confounders.

RESULTS

Children with "high" HCB concentrations (≥90th percentile) in maternal serum, demonstrated decreased scores in perceptual performance (adjusted β=-6.07; 95% CI: -10.17, -1.97), general cognitive (adjusted β=-4.97; 95% CI: -8.99, -0.96), executive function (adjusted β=-6.24; 95% CI: -10.36, -2.11) and working memory (adjusted β=-4.71; 95% CI: -9.05, -0.36) scales at 4years of age. High exposure to PCBs (≥90th percentile) during pregnancy was associated with a 4.62 points reduction in working memory score at 4years of age (95% CI: -9.10, -0.14). Prenatal exposure to DDE, HCB and PCBs was not associated with child behavioral difficulties.

CONCLUSIONS

The findings suggest that prenatal exposure to HCB and PCBs may contribute to reduced cognitive development at preschool age. Our results raise the possibility that exposure to HCB may play a more important role in child cognition than previously considered.

Novel application of statistical methods for analysis of multiple toxicants identifies DDT as a risk factor for early child behavioral problems

BACKGROUND

The aim of this study was to assess the association between postnatal exposure to multiple persistent organic pollutants (POPs) measured in breast milk samples and early behavioral problems using statistical methods to deal with correlated exposure data.

METHODS

We used data from the Norwegian HUMIS study. We measured concentrations of 24 different POPs in human milk from 612 mothers (median collection time: 32 days after delivery), including 13 polychlorinated biphenyls (PCB) congeners, 6 polybrominated diphenyl ethers (PBDE) congeners and five organochlorine compounds. We assessed child behavioral problems at 12 and 24 months using the infant toddler symptom checklist (ITSC). Higher score in ITSC corresponds to more behavioral problems. First we performed principal component analysis (PCA). Then two variable selection methods, elastic net (ENET) and Bayesian model averaging (BMA), were applied to select any toxicants associated with behavioral problems. Finally, the effect size of the selected toxicants was estimated using multivariate linear regression analyses.

RESULTS

p,p'-DDT was associated with behavioral problems at 12 months in all the applied models. Specifically, the principal component composed of organochlorine pesticides was significantly associated with behavioral problems and both ENET and BMA identified p,p'-DDT as associated with behavioral problems. Using a multiple linear regression model an interquartile increase in p,p'-DDT was associated with a 0.62 unit increase in ITSC score (95% CI 0.45, 0.79) at 12 months, corresponding to more behavioral problems. The association was modified by maternal education: the effect of p,p'-DDT was strongest in women with lower education (β=0.59; 95%CI: 0.38, 0.81) compared to the mother with higher education (β=0.14; 95%CI: -0.05, 0.34) (p-value for interaction=0.089). At 24 months, neither selection method consistently identified any toxicant associated with behavioral problems.

CONCLUSION

Within a mixture of 24 toxicants measured in breast milk, p,p'-DDT was the single toxicant associated with behavioral problems at 12 months using different methods for handling numerous correlated exposures.

Prenatal DDT and DDE exposure and child IQ in the CHAMACOS cohort

Although banned in most countries, dichlorodiphenyl-trichloroethane (DDT) continues to be used for vector control in some malaria endemic areas. Previous findings from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) cohort study found increased prenatal levels of DDT and its breakdown product dichlorodiphenyl-dichloroethylene (DDE) to be associated with altered neurodevelopment in children at 1 and 2years of age. In this study, we combined the measured maternal DDT/E concentrations during pregnancy obtained for the prospective birth cohort with predicted prenatal DDT and DDE levels estimated for a retrospective birth cohort. Using generalized estimating equation (GEE) and linear regression models, we evaluated the relationship of prenatal maternal DDT and DDE serum concentrations with children's cognition at ages 7 and 10.5years as assessed using the Full Scale Intelligence Quotient (IQ) and 4 subtest scores (Working Memory, Perceptual Reasoning, Verbal Comprehension, and Processing Speed) of the Wechsler Intelligence Scale for Children (WISC). In GEE analyses incorporating both age 7 and 10.5 scores (n=619), we found prenatal DDT and DDE levels were not associated with Full Scale IQ or any of the WISC subscales (p-value>0.05). In linear regression analyses assessing each time point separately, prenatal DDT levels were inversely associated with Processing Speed at age 7years (n=316), but prenatal DDT and DDE levels were not associated with Full Scale IQ or any of the WISC subscales at age 10.5years (n=595). We found evidence for effect modification by sex. In girls, but not boys, prenatal DDE levels were inversely associated with Full Scale IQ and Processing Speed at age 7years. We conclude that prenatal DDT levels may be associated with delayed Processing Speed in children at age 7years and the relationship between prenatal DDE levels and children's cognitive development may be modified by sex, with girls being more adversely affected.

Effect of prolonged exposure to sublethal concentrations of DDT and DDE on protein expression in human pancreatic beta cells

Pollution of the environment represents one of less explored potential reasons for the worldwide epidemic of type 2 diabetes. One of the most prevalent organochlorine pollutants remains the pesticide DDT and its degradation product DDE. Despite some epidemiologic correlations between levels of DDT and DDE in human organism and the prevalence of diabetes, there is almost no information about the exact targets of these compounds inside pancreatic beta cells. To detect functional areas of pancreatic beta cells that could be affected by exposure to DDT and DDE, we analyzed changes in protein expression in the NES2Y human pancreatic beta cell line exposed to three sublethal concentrations (0.1 μM, 1 μM, 10 μM) of DDT and DDE for 1 month. Protein separation and identification was achieved using high-resolution 2D-electrophoresis, computer analysis and mass spectrometry. With these techniques, four proteins were found downregulated after exposure to 10 μM DDT: three cytoskeletal proteins (cytokeratin 8, cytokeratin 18 and actin) and one protein involved in glycolysis (alpha-enolase). Two proteins were downregulated after exposure to 10 μM DDE: cytokeratin 18 and heterogenous nuclear ribonucleoprotein H1 (HNRH1). These changes correlate with previously described effects of other stress conditions (e.g. exposure to palmitate, hyperglycemia, imidazoline derivative, and cytokines) on protein expression in pancreatic beta cells. We conclude that cytoskeletal proteins and their processing, glucose metabolism, and mRNA processing may represent targets affected by exposure to conditions hostile to pancreatic beta cells, including exposure to DDT and DDE.

Risk of DDT residue in maize consumed by infants as complementary diet in southwest Ethiopia

Infants in Ethiopia are consuming food items such as maize as a complementary diet. However, this may expose infants to toxic contaminants like DDT. Maize samples were collected from the households visited during a consumption survey and from markets in Jimma zone, southwestern Ethiopia. The residues of total DDT and its metabolites were analyzed using the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method combined with dispersive solid phase extraction cleanup (d-SPE). Deterministic and probabilistic methods of analysis were applied to determine the consumer exposure of infants to total DDT. The results from the exposure assessment were compared with the health based guidance value in this case the provisional tolerable daily intake (PTDI). All maize samples (n=127) were contaminated by DDT, with a mean concentration of 1.770 mg/kg, which was far above the maximum residue limit (MRL). The mean and 97.5 percentile (P 97.5) estimated daily intake of total DDT for consumers were respectively 0.011 and 0.309 mg/kg bw/day for deterministic and 0.011 and 0.083 mg/kg bw/day for probabilistic exposure assessment. For total infant population (consumers and non-consumers), the 97.5 percentile estimated daily intake were 0.265 and 0.032 mg/kg bw/day from the deterministic and probabilistic exposure assessments, respectively. Health risk estimation revealed that, the mean and 97.5 percentile for consumers, and 97.5 percentile estimated daily intake of total DDT for total population were above the PTDI. Therefore, in Ethiopia, the use of maize as complementary food for infants may pose a health risk due to DDT residue.

Exposição a pesticidas organoclorados e desenvolvimento cognitivo em crianças e adolescentes residentes em uma área contaminada no Brasil

Objetivos: avaliar o desempenho cognitivo de crianças e adolescentes residentes em uma área contaminada com pesticidas organoclorados (OC), e fatores associados à exposição. Métodos: realizou-se um estudo seccional com 102 indivíduos entre 6-16 anos residentes em Cidade dos Meninos, RJ, entre 2012-2013. Uma subamostra de 46 destas crianças dispunha das concentrações séricas de pesticidas OC e hormônios tireóideos, determinados entre 2003-2004. Local de residência materna e tempo de amamentação foram informados por todos os participantes. Desempenho cognitivo foi avaliado pela escala WISC-III. Utilizou-se regressão multivariada para explorar as associações. Resultados: pelo menos 40% das crianças apresentaram inteligência inferior à média (QI<90) em seis domínios cognitivos. A função executiva demonstrou o menor escore. Local de residência materna e tempo de amamentação não associaram-se à cognição, exceto a função executiva. Níveis de alfahexaclorocicloexano (HCH) associaram-se a redução de 0,45, 0,33 e 0,46 pontos nas áreas de execução, resistência à distração (RD) e velocidade de processamento (VP), respectivamente; gama-HCH associou-se a redução de 1,74 pontos na RD e 1,84 pontos na VP; e p,p’-DDT (dicloro-difenil-tricloroetano) relacionou- se a menor pontuação (-0,81) na VP. Observou-se leve associação inversa entre os níveis de triiodotironina total e organização perceptual. Conclusões: resultados sugerem que a exposição crônica aos pesticidas OC poderia acarretar déficits cognitivos nestas crianças e adolescentes.

The impact of toxins on the developing brain

The impact of toxins on the developing brain is usually subtle for an individual child, but the damage can be substantial at the population level. Numerous challenges must be addressed to definitively test the impact of toxins on brain development in children: We must quantify exposure using a biologic marker or pollutant; account for an ever-expanding set of potential confounders; identify critical windows of vulnerability; and repeatedly examine the association of biologic markers of toxins with intellectual abilities, behaviors, and brain function in distinct cohorts. Despite these challenges, numerous toxins have been implicated in the development of intellectual deficits and mental disorders in children. Yet, too little has been done to protect children from these ubiquitous but insidious toxins. The objective of this review is to provide an overview on the population impact of toxins on the developing brain and describe implications for public health.

Persistent organic pollutants measured in maternal serum and offspring neurodevelopmental outcomes--a prospective study with long-term follow-up

Fetal exposure to persistent organic pollutants (POPs) has been linked to adverse neurodevelopment, but few studies have had follow-up beyond childhood. The purpose of this study was to examine the association of maternal serum concentrations of two perfluoroalkyl acids (perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)), polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p'-DDE) and hexachlorobenzene (HCB) with offspring behavioural and affective disorders and scholastic achievement in a prebirth cohort study with 20 years of follow up. Between 1988 and 1989 pregnant women (n=965) were recruited for the prebirth Danish Fetal Origins 1988 (DaFO88) Cohort in Aarhus, Denmark. Perfluoroalkyl acids, PCBs, p,p'-DDE, and HCB were quantified in serum from week 30 of gestation (n=876 for perfluoroalkyl acids/872 for PCBs, p,p'-DDE, HCB). Offspring were followed up through national registries until 2011. We evaluated associations between maternal serum concentrations of these POPs and offspring neurodevelopmental outcomes, defined as: first admission diagnosis or prescription of medication until age >20 for (1) ADHD; (2) depression; and (3) scholastic achievement defined as mean grade on a standardized written examination given in the 9th grade (final exams of compulsory school in Denmark). Maternal concentrations of organochlorine substances and perfluoroalkyl acids were higher than present day levels. During the follow-up period there were 27 (3.1%) cases of ADHD and 104 (11.9%) cases of depression; the mean scholastic achievement was 6.7 (SD 2.3). Overall we found no association for maternal levels of any of the measured pollutants with offspring behavioural and affective disorders or with scholastic achievement. Our analyses based on biomarkers from a cohort of over 800 pregnant women with long-term close to complete follow-up through national registries showed little evidence of a programming effect of PFOA, PFOS, PCBs, p,p'-DDE, and HCB in relation to clinically and functionally relevant offspring neurodevelopmental outcomes.