Developmental neurotoxicants in human milk: Comparison of levels and intakes in three European countries

Trend analyses of persistent organic pollutants in human milk from first-time mothers in Norway between 2002 and 2021

INTRODUCTION

Persistent organic pollutants (POPs) are stable compounds characterized by their resistance to degradation. From the 1960-70's organochlorine pesticides (OCPs), such as DDTs and polychlorinated biphenyls (PCBs) raised concerns regarding health and environmental impacts. This has led to the banning of POPs in the USA and Europe including Norway in 1980 and worldwide under the 2004 Stockholm Convention. The exposure of nursing infants to POPs has been a significant focus, prompting extensive research into the presence of these substances in human breast milk. In this study, we explored the temporal trends of POPs concentrations in breast milk sampled between 2002 and 2021 by comparing the concentration across the mother's year of birth.

METHOD

Two Norwegian cohorts of lactating women were utilized (the HUMIS study and the "Iodine in Early Life"-Study). Concentrations of 15 different POPs, including PCBs, OCPs, and brominated diphenyl ethers (BDEs) were measured in 513 breast milk samples that had been collected over two decades in a subset of first-time mothers.

RESULTS

Time trend analysis indicated a steady decrease in concentration levels when adjusted for maternal age. The largest reduction was observed in β-HCH, age-adjusted (-17.1%, 95% CI -18.7, -15.4), followed by ∑6BDE (-9.1%, 95% CI -10.5, -7.7), ∑6PCBs (-7.1%, 95% CI -7.7, -6.5), and ∑2DDTs (-7.0%, 95% CI -8.0, -6.0). In contrast, an increasing trend was noted in the median concentrations of β-HCH, ∑2DDTs, and ∑6BDE in the mothers born in 1990-1994 to 1995-2002.

CONCLUSION

Our study demonstrates a decline of most POPs in breast milk, likely attributed to international regulatory efforts like the Stockholm Convention. Notably, an increase in the 95th percentile concentrations of β-HCH, ∑2DDTs, and ∑6BDEs was noted in mothers born in 1990-1994 compared to those born in 1995-2002 suggests demographic shifts that may influence exposure levels. Further research is needed to explore and understand the underlying factors for the rise in median concentrations of ∑6BDEs.

Perinatal exposure to potential endocrine disrupting chemicals and autism spectrum disorder: From Norwegian birth cohort to zebrafish studies

BACKGROUND

The etiology of autism spectrum disorder (ASD) is multifactorial, involving genetic and environmental contributors such as endocrine-disrupting chemicals (EDCs).

OBJECTIVE

To evaluate the association between perinatal exposure to 27 potential EDCs and ASD among Norwegian children, and to further examine the neurodevelopmental toxicity of associated chemicals using zebrafish embryos and larvae.

METHOD

1,199 mothers enrolled in the prospective birth-cohort (HUMIS, 2002-2009) study. Breastmilk levels of 27 chemicals were measured: polychlorinated biphenyls, organochlorine pesticides, polybrominated diphenyl ethers, and perfluoroalkyl substances as a proxy for perinatal exposure. We employed multivariable logistic regression to determine association, utilized elastic net logistic regression as variable selection method, and conducted an in vivo study with zebrafish larvae to confirm the neurodevelopmental effect.

RESULTS

A total of 20 children had specialist confirmed diagnosis of autism among 1,199 mother-child pairs in this study. β-Hexachlorocyclohexane (β-HCH) was the only chemical associated with ASD, after adjusting for 26 other chemicals. Mothers with the highest levels of β-HCH in their milk had a significant increased risk of having a child with ASD (OR = 1.82, 95 % CI: 1.20, 2.77 for an interquartile range increase in ln-transformed β-HCH concentration). The median concentration of β-HCH in breast milk was 4.37 ng/g lipid (interquartile range: 2.92-6.47), and the estimated daily intake (EDI) for Norwegian children through breastfeeding was 0.03 µg/kg of body weight. The neurodevelopmental and social behavioral effects of β-HCH were established in zebrafish embryos and larvae across various concentrations, with further analysis suggesting that perturbation of dopaminergic neuron development may underlie the neurotoxicity associated with β-HCH.

CONCLUSIONS

Prenatal exposure to β-HCH was associated with an increased risk of specialist-confirmed diagnoses of ASD among Norwegian children, and the EDI surpasses the established threshold. Zebrafish experiments confirm β-HCH neurotoxicity, suggesting dopaminergic neuron disruption as a potential underlying mechanism.

Investigation of polychlorinated biphenyls in breast milk from two regions in Bulgaria

Human breast milk is an optimally balanced infant food and a suitable tool for assessing the burden of humans with lipophilic persistent organic pollutants. The aim of this study was to investigate the accumulation profile of polychlorinated biphenyls in breast milk of women living in Bulgaria and to assess the health risk to infants. Breast milk samples were obtained from 72 healthy primiparae and multiparae mothers, living in two regions in northeastern Bulgaria - Varna region and Dobrich region, in the period October 2019-July 2021. Important information for the study, such as age, body mass, smoking and dietary habits, was collected through a questionnaire. Fifteen congeners of PCBs, including six indicator congeners, were determined by capillary gas chromatography system with mass spectrometry detection. The lipid content of the tested samples was in the range from 0.5% to 6.7%, with average value 3.25%. The six indicator PCBs in human milk samples formed up to 89% of the total PCBs levels. The most abundant congener was PCB 153, followed by PCB 138 and PCB 180. Five of the 15 PCB congeners (77, 126, 128, 156, 169) were not detected in any of the milk samples. The arithmetic mean PCB levels in milk samples from Varna (32.7 ng/g lw) were found higher than PCB levels in breast milk of mothers from Dobrich (22.5 ng/g lw). The highest PCB levels were found in milk samples from primiparae mothers in 36-40 age group (for both regions). Infant exposure to PCBs present in human milk was estimated using toxic equivalents (TEQ). The health risk to infants was assessed and was compared to the tolerable daily intake (TDI). Positive correlation was found between the arithmetic mean PCBs levels and two important factors - the age and body mass index of the primiparae group. The mean values of the analyzed PCB congeners in breast milk samples from multiparae were lower than in those from primiparae mothers. The regional differences in PCB concentrations were small, suggesting similar exposures in the studied regions. The levels of PCBs in breast milk were found lower than levels from studies in other European countries. Statistical data does not show any association between PCB levels in milk and dietary habits. The results showed that infants are not at risk of any adverse effects caused by PCBs through breast milk.

Assessment of organohalogenated pollutants in breast milk from the Czech Republic

This biomonitoring survey brings new information on the occurrence of a total of 94 organohalogenated pollutants in 231 human breast milk samples collected in 2019 and 2021 from women living in two regions of the Czech Republic (Karvina and Ceske Budejovice). This study aimed to evaluate the concentrations of 6 indicator polychlorinated biphenyls (PCBs), 10 organochlorine pesticides (OCPs), 34 halogenated flame retardants (HFRs), 29 perfluoroalkyl and polyfluoroalkyl substances (PFAS) and 15 polychlorinated naphthalenes (PCNs). PCBs, OCPs, most of HFRs and PCNs were identified/quantified by gas chromatography coupled to (tandem) mass spectrometry (GC-MS(/MS)), while PFAS, hexabromocyclododecane isomers (HBCD), brominated phenols, and tetrabromobisphenol A (TBBPA) by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The mean value of the sum of the 6 indicator PCBs was 123.12 nanogram per gram of lipid weight (ng g^-1 lw). Hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH) and p,p'-dichlorodiphenyl-dichloroethylene (p,p'-DDE) were the most abundant OCPs, detected in 100 % (mean 11.8 ng g^-1 lw), 94.8 % (mean 6.1 ng g^-1 lw) and 100 % (mean 101.5 ng g^-1 lw) of samples, respectively. PCN congeners 20, 52 and 66 were detected in <1 % of the samples. The HFRs concentrations were relatively low compared to the levels of OCP; The detection rate of polybrominated diphenyl ethers (PBDEs, # 47, 99 and 153) ranged 21-68 % with a mean concentrations of 0.34 ng g^-1 lw - 0.42 ng g^-1 lw. PFAS concentrations were also low, with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) dominant in this group (means of 22 pg ml^-1 and 21 pg ml^-1, respectively). Our results confirmed the long-term trend of declining levels of banned POPs in Czech mothers. The amounts of PCBs and OCPs were higher in older breastfeeding primiparous women.

Methylmercury-induced reactive oxygen species-dependent and independent dysregulation of MAP kinase-related signaling pathway in cultured normal rat cerebellar astrocytes

Methylmercury (MeHg), a global environmental pollutant, could seriously damage the central nervous system (CNS) and cause neurological disorders such as cerebellar symptoms. Although numerous studies have revealed detailed toxicity mechanisms of MeHg in neurons, toxicity in astrocytes is barely known. Here, we tried to shed light on the toxicity mechanisms of MeHg exposure in cultured normal rat cerebellar astrocytes (NRA), focusing on the involvement of reactive oxygen species (ROS) in MeHg toxicity by assessing the effects of major antioxidants Trolox, a free-radical scavenger, N-acetyl-L-cysteine (NAC), a potent thiol-containing antioxidant, and glutathione (GSH), an endogenous thiol-containing antioxidant. Exposure to MeHg at just approximately 2 µM for 96 h increased cell viability, which was accompanied by the increase in intracellular ROS level and at ≥ 5 µM induced significant cell death and lowered ROS level. Trolox and NAC suppressed 2 µM MeHg-induced increases in cell viability and ROS level corresponding to control, although GSH with 2 µM MeHg induced significant cell death and ROS increase. On the contrary, against 4 µM MeHg-induced cell loss and ROS decrease, NAC inhibited both cell loss and ROS decrease, Trolox inhibited cell loss and further enhanced ROS decrease, and GSH moderately inhibited cell loss and increased ROS level above the control level. MeHg-induced oxidative stress was suggested by increases in the protein expression levels of heme oxygenase-1 (HO-1), Hsp70, and Nrf2, except for the decrease in SOD-1 and no change in catalase. Furthermore, MeHg exposure dose-dependently induced increases in the phosphorylation of MAP kinases (ERK1/2, p38MAPK, and SAPK/JNK) and phosphorylation and/or expression levels of transcription factors (CREB, c-Jun, and c-Fos) in NRA. NAC successfully suppressed 2 µM MeHg-induced alterations in all of the above-mentioned MeHg-responsive factors, whereas Trolox suppressed some MeHg-responsive factors but failed to suppress MeHg-induced increases in the protein expression levels of HO-1 and Hsp70 and increase in p38MAPK phosphorylation. Protein expression analyses in NRA exposed to 2 µM MeHg and GSH were excluded because of devastating cell death. These results suggested that MeHg could induce aberrant NRA activation, and ROS must be substantially involved in the toxicity mechanism of MeHg in NRA; however, other factors should be assumed.

Postnatal exposure to organic pollutants in maternal milk in north-western Spain

Evaluation of postnatal exposure to organic pollutants is especially important for suckling infants during breastfeeding, a crucial perinatal growth period when organs and hormonal systems develop. We determined levels of 60 pollutants, including organochlorine pesticides (OCPs), organophosphorus pesticides (OPPs), pyrethroids (PYRs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and polybrominated diphenyl ethers (PBDEs), in 81 breast milk samples from breastfeeding mothers from Santiago de Compostela (north-western Spain). For most detected organic pollutants, levels were correlated with the season of milk sampling, maternal age at delivery, and place of residence. Dietary consumption habits (eggs, molluscs, and vegetable oils) were also correlated with OCP, OPP, PCB, PBDE and PYR levels. We also assessed the risk to infant health of exposure to organic pollutants in breast milk. PAHs, OCPs, OPPs, and PYRs accounted for almost 95% of the targeted organic pollutants in the samples analysed.

Detection of endocrine and metabolism disrupting xenobiotics in milk-derived fat samples by fluorescent protein-tagged nuclear receptors and live cell imaging

Nuclear receptors (NRs) are ligand-modulated transcription factors that regulate multiple physiological functions in our body. Many NRs in their unliganded state are localized in cytoplasm. The ligand-inducible nuclear translocation of NRs provides a valuable tool for studying the NR-ligand interactions and their downstream effects. The translocation response of NRs can be studied irrespective of the nature of the interacting ligand (agonist, antagonist, or a small molecule modulator). These nuclear translocation studies offer an advantage over promoter-reporter-based transcription assays where transcription response is observed only with the activating hormones or agonistic ligands. Globally, milk serves as a major dietary source. However, suspected presence of endocrine/metabolism disrupting chemicals like bisphenols, parabens, organochlorine pesticides, carbamates, non-steroidal anti-inflammatory drugs, chloramphenicol, brominated flame retardants, etc. has been reported. Considering that these chemicals may impart serious developmental and metabolism-related health concerns, it is essential to develop assays suitable for the detection of xenobiotics present at differing levels in milk. Since milk samples cannot be used directly on cultured cells or for microscopy, a combination of screening strategies has been developed herein based on the revelation that i) lipophilic NR ligands can be successfully retrieved in milk-fat; ii) milk-fat treatment of cells is compatible with live-cell imaging studies; and finally, iii) treatment of cells with xenobiotics-spiked and normal milk derived fat provides a visual and quantifiable response of NR translocation in living cells. Utilizing a milk-fat extraction method and Green Fluorescent Protein (GFP) tagged NRs expressed in cultured mammalian cells, followed by an assessment of NR response proved to be an effective approach for screening xenobiotics present in milk samples.HighlightsDiverse endocrine and metabolism disrupting chemicals are suspected to contaminate milk.Nuclear receptors serve as 'xenosensors' for assessing the presence of xenobiotics in milk.Nuclear import of steroid receptors with (ant)agonist can be examined in live cells.Lipophilic xenobiotics are extracted and observed enriched in milk-fat fraction.A comprehensive cell-based protocol aids in the detection of xenobiotics in milk.

Mixture of environmental pollutants in breast milk from a Spanish cohort of nursing mothers

Breastfeeding is one of the most effective ways to ensure child health and survival, with several benefits for both the infants and their mothers. However, breast milk can contain environmental pollutants with endocrine disruption capacity, neurotoxicity and/or potential to alter microbiota. Monitoring breast milk provides information on the current chemical exposure of breastfed infants and, in addition, on the current and historical exposure of nursing mothers. In this study, the levels of a wide range of pollutants were measured in breast milk of Spanish nursing mothers. Target chemicals were dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), oxy-chlordane, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), per- and poly-fluoroalkyl substances (PFASs) (including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA)), chlorpyrifos, bisphenol A (BPA), tetrabromobisphenol A (TBBPA), and a number of toxic and essential elements. Traces of most chemicals were found. A correlation between the levels of some persistent organic pollutants (POPs) and maternal characteristics (age and body mass index) was observed, while smoking was associated to higher concentrations of some toxic elements. Higher levels of PCBs were detected in samples from Spanish primiparous mothers compared to non-Spanish multiparous women. Breast milk from low-income mothers showed higher content of DDT and DDE than high-income mothers. Although breastfeeding is clearly beneficial for babies, the exposure to this mixture of hazardous substances, as well as their interaction and combined effects must not be disregarded.

A case-cohort study of perinatal exposure to potential endocrine disrupters and the risk of cryptorchidism in the Norwegian HUMIS study

BACKGROUND

Exposure to endocrine-disrupting chemicals (EDCs) during the critical period of testicular descent may increase the risk of cryptorchidism and male fertility.

OBJECTIVE

To investigate 27 potential EDCs measured in breast milk as a proxy for perinatal exposure and the risk of cryptorchidism in a prospective cohort.

METHOD

The Norwegian Human Milk Study (2002-2009) enrolled 2606 mother-infant pairs, of which 1326 were mother-son pairs. In a case-cohort design, we studied 641 male infants who had 27 EDCs already quantified in milk samples: 5 organochlorine pesticides, 14 polychlorinated biphenyls (PCBs), 6 brominated flame retardants, and 2 poly- and perfluoroalkyl substances. We defined cases of congenital, recurrent, persistent and ever-reported cryptorchidism based on questionnaires mothers completed when children were 1, 6, 12 and 24 months old. Variable selection via elastic net logistic regression identified the best cryptorchidism predictors while multivariable logistic regression models determined their effect estimates.

RESULTS

The prevalence of reported congenital cryptorchidism was 6.1%, with half spontaneously descending within six months of birth, after which prevalence stabilized between 2.2 and 2.4%. The ever-reported prevalence of cryptorchidism at 1, 6, 12, or 24 months was 12.2%. Elastic net models identified PCB-74 (OR = 1.31, 95% CI: 1.001-1.703), PCB-114 (OR = 1.36, 95% CI: 1.05-1.77), PCB-194 (OR = 1.28, 95% CI: 1.03-1.53) and β-HCH (OR = 1.26, 95% CI: 1.03-1.53 (per interquartile range increase in concentration of EDCs) as best predictors of congenital cryptorchidism. No EDCs were selected for either recurrent or persistent cryptorchidism, and only PCB-194 was selected by elastic net for ever-reported cryptorchidism (OR = 1.23, 95% CI: 1.01-1.51), in contrast to unpenalized multivariable logistic regression, where most of the individual congeners of PCBs showed significant associations.

CONCLUSION

In the largest multi-pollutant analysis to date considering potential confounding from co-exposure to other chemicals, perinatal exposure to PCB-74, PCB-114, PCB-194 and β-HCH were associated with increased odds of congenital cryptorchidism. Many PCBs may falsely be associated with cryptorchidism when assessed individually, due to confounding by highly correlated chemicals. Experimental studies are warranted to confirm our findings.

Fish consumption is an indicator of exposure to non-dioxin like polychlorinated biphenyls in cumulative risk assessments based on a probabilistic and sensitive approach

The health effects of non-dioxin like polychlorinated biphenyls (NDL-PCBs) include liver, immune, neurodevelopmental, and neurobehavioral effects in addition to hormone alteration. Among 209 PCB congeners, six indicator PCBs (ICES-6) account for about half of NDL-PCBs present in feed and food. The objectives of the current study were first to examine the levels of total PCBs, NDL-PCBs, and ICES-6 PCBs in 200 foods commonly consumed in Taiwan and, second, to estimate the cumulative health risks of NDL-PCB consumption. We suggest a risk management strategy that identifies foodstuffs with particularly high NDL-PCB content. In 200 food samples, which were grouped into 12 categories and 64 food types, 51 PCB congeners were detected. The concentrations of ICES-6 PCBs in all samples were lower than the maximum levels for NDL-PCBs in foodstuffs set by the European Union. PCB-153, PCB-138, and PCB-180 were the major congeners in all food, indicating that the food was contaminated in the past. ICES-6 PCBs contributed 42.2%-52.9% of total NDL-PCBs in all tested foodstuffs. The average estimated daily intake (EDI) of PCBs ranged from 1.22 ng/kg bw/day to 2.89 ng/kg bw/day in different age groups (95th quantile [P95]: 4.12-10.28 ng/kg bw/day). The P95 EDI in 3-6-year-olds was higher than 10 ng/kg/day. A qualitative sensitivity analysis in ICES-6 PCBs exposure showed that for the 3- to 6-year-old group, the highest sensitivity was how much fish they ate (37.6%) and its concentration (32.5%). The consumption of pork, eggs, fish, and other seafood accounts for over 90% of ICES-6 PCBs intake, and these foods should be highlighted in guidelines regarding NDL-PCB intake.

Evaluating the Role of the Steroid and Xenobiotic Receptor (SXR/PXR) in PCB-153 Metabolism and Protection against Associated Adverse Effects during Perinatal and Chronic Exposure in Mice

BACKGROUND

Polychlorinated biphenyls (PCBs) are environmental toxicants; PCB exposure has been associated with adverse effects on wildlife and humans. However, the mechanisms underlying these adverse effects are not fully understood. The steroid and xenobiotic receptor [SXR; also known as the pregnane X receptor (PXR) and formally known as NR1I2] is a nuclear hormone receptor that regulates inducible metabolism of drugs and xenobiotics and is activated or inhibited by various PCB congeners.

OBJECTIVES

The aim of this study was to investigate the effects of exposure to PCB-153, the most prevalent PCB congener in human tissues, on SXR knockout mice (SXRKO) and to elucidate the role of SXR in PCB-153 metabolism and promotion of its harmful effects.

METHODS

Wild-type (WT) and SXRKO mice were chronically or perinatally exposed to a low dose (54μg/kg/d) of PCB-153. Blood, livers, and spleens were analyzed using transcriptome sequencing (RNA-seq) and molecular techniques to investigate the impacts of exposure on metabolism, oxidative stress, and hematological parameters.

RESULTS

SXRKO mice perinatally exposed to PCB-153 displayed elevated oxidative stress, symptoms of hemolytic anemia, and premature death. Transcriptomal analysis revealed that expression of genes involved in metabolic processes was altered in SXRKO mice. Elevated levels of the PCB-153 metabolite, 3-OH-PCB-153, were found in exposed SXRKO mice compared to exposed WT mice. Blood hemoglobin (HGB) levels were lower throughout the lifespan, and the occurrence of intestinal tumors was larger in SXRKO mice chronically exposed to PCB-153 compared to vehicle and WT controls.

DISCUSSION

Our results suggest that altered metabolism induced by SXR loss of function resulted in the accumulation of hydroxylated metabolites upon exposure to PCB-153, leading to oxidative stress, hemolytic anemia, and tumor development in a mouse model. These results support a major role for SXR/PXR in protection against xenobiotic-induced oxidative stress by maintaining proper metabolism in response to PCB-153 exposure. This role of SXR could be generally applicable to other environmental toxicants as well as pharmaceutical drugs. https://doi.org/10.1289/EHP6262.

Adolescent exposure to environmental level of PCBs (Aroclor 1254) induces non-alcoholic fatty liver disease in male mice

Polychlorinated biphenyls (PCBs) are persistent organic pollutants found in various environmental media, and there is growing evidence that PCBs may contribute to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). The purposes of this study were to investigate whether environmental level of Aroclor 1254 (a commercial mixture of PCBs) exposure to adolescent male mice could induce the development of NAFLD and the mechanisms involved. Twenty-one-day-old male C57BL/6 mice were exposed to Aroclor 1254 (0.5-500 μg/kg body weight) by oral gavage once every third day for 60 days. The results showed that exposure to Aroclor 1254 increased body weight and decreased the liver-somatic index in a dose-dependent manner. Aroclor 1254 administration increased lipid accumulation in the liver and induced the mRNA expression of genes associated with lipogenesis, including acetyl-CoA carboxylase 1 (Acc1), acetyl-CoA carboxylase 2 (Acc2) and fatty acid synthase (Fasn). Moreover, Aroclor 1254 decreased peroxisome proliferator-activated receptor alpha (PPARα) signaling and lipid oxidation. In addition, we found that Aroclor 1254 administration induced oxidative stress in mouse liver and elevated the protein level of cyclooxygenase 2 (COX-2), an inflammatory molecule, possibly via the endoplasmic reticulum (ER) stress inositol-requiring enzyme 1α-X-box-binding protein-1 (IRE1α-XBP1) pathway, but not the nuclear factor-κB (NF-κB) pathway. In summary, adolescent exposure to environmental level of PCBs stimulated oxidative stress, ER stress and the inflammatory response and caused NAFLD in male mice. This work provides new insight into the idea that adolescent exposure to environmental level of PCBs might induce the development of NAFLD under the regulation of ER stress in males.

QuEChERS extraction coupled to GC-MS for a fast determination of polychlorinated biphenyls in breast milk from Polish women

Polychlorinated biphenyls (PCBs) in breast milk has been determined. Therefore, it was necessary to develop and adapt an analytical method to analyze PCB compounds. The whole procedure was applied to 31 breast milk samples, which were collected from Polish mothers. The QuEChERS method was optimized as a fast and cheap sample preparation method. The procedure allowed us to obtain recovery values between 96.46% and 119.98% with acceptable relative standard deviations (3.36-12.71%). Gas chromatography with mass spectrometry (GC-MS) was used for final determination. The method was validated using parameters such as linearity, limit of detection and quantification, intra-day precision, and reproducibility. The mean concentration of ∑iPCBs in this study was 30.94 ng/g of lipid. Assigned daily intake of PCBs was lower than the tolerable daily intake, which shows that the analyzed milk is safe to the infants. However, the monitoring of PCBs in milk is still important, and the QuEChERS method with GC-MS can be an effective tool for tracking organic impurities in breast milk.

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.

Concentration of mercury, cadmium, and lead in breast milk from Norwegian mothers: Association with dietary habits, amalgam and other factors

Mercury (Hg), cadmium (Cd), and lead (Pb) are of great concern for food safety and infants are especially sensitive to exposure to the maternal body burden. We quantified these elements in breast milk from Norwegian mothers and determined their association with dietary habits, maternal amalgam fillings, and smoking. Breast milk (n = 300) from the Norwegian Human Milk Study (HUMIS) was analyzed using triple quadrupole inductively coupled plasma mass spectrometry, after an acidic decomposition using microwave technique. We used multiple linear regression to examine predictors of Hg and Cd in breast milk, and logistic regression to test predictors of Pb above the quantification limit. The median breast milk concentrations (minimum - maximum) were 0.20 μg Hg/kg (<0.058-0.89), 0.057 μg Cd/kg (0.017-1.2), and <0.67 μg Pb/kg (<0.2-7.5). Cadmium showed no significant relation with any exposure variable investigated. Lead was associated with intake of liver and kidneys from game. For Hg concentration in breast milk, number of amalgam fillings and high fish consumption were significant predictors (p < 0.001). We detected a significant association (p < 0.01) between Hg in breast milk and maternal consumption of Atlantic halibut, lean fish, mussels and scallops and lifetime consumption of crab. Seafood intake alone explained 10% of variance, while together with amalgam explained 46% of variance in Hg concentration in breast milk. Our findings emphasize the importance of following consumer advice with respect to fish and seafood and points to amalgam as an important source for Hg exposure.

Early-life exposure to persistent organic pollutants (OCPs, PBDEs, PCBs, PFASs) and attention-deficit/hyperactivity disorder: A multi-pollutant analysis of a Norwegian birth cohort

BACKGROUND

Numerous ubiquitous environmental chemicals are established or suspected neurotoxicants, and infants are exposed to a mixture of these during the critical period of brain maturation. However, evidence for associations with the risk of attention-deficit/hyperactivity disorder (ADHD) is sparse. We investigated early-life chemical exposures in relation to ADHD.

METHODS

We used a birth cohort of 2606 Norwegian mother-child pairs enrolled 2002-2009 (HUMIS), and studied a subset of 1199 pairs oversampled for child neurodevelopmental outcomes. Concentrations of 27 persistent organic pollutants (14 polychlorinated biphenyls, 5 organochlorine pesticides, 6 brominated flame retardants, and 2 perfluoroalkyl substances) were measured in breast milk, reflecting the child's early-life exposures. We estimated postnatal exposures in the first 2 years of life using a pharmacokinetic model. Fifty-five children had a clinical diagnosis of ADHD (hyperkinetic disorder) by 2016, at a median age of 13 years. We used elastic net penalized logistic regression models to identify associations while adjusting for co-exposure confounding, and subsequently used multivariable logistic regression models to obtain effect estimates for the selected exposures.

RESULTS

Breast milk concentrations of perfluorooctane sulfonate (PFOS) and β‑hexachlorocyclohexane (β-HCH) were associated with increased odds of ADHD: odds ratio (OR) = 1.77, 95% confidence interval (CI): 1.16, 2.72 and OR = 1.75, 95% CI: 1.22, 2.53, per interquartile range increase in ln-transformed concentrations, respectively. Stronger associations were observed among girls than boys for PFOS (p_interaction = 0.025). p,p'‑Dichlorodiphenyltrichloroethane (p,p'-DDT) levels were associated with lower odds of ADHD (OR = 0.64, 95% CI: 0.42, 0.97). Hexachlorobenzene (HCB) had a non-linear association with ADHD, with increasing risk in the low-level exposure range that switched to a decreasing risk at concentrations above 8 ng/g lipid. Postnatal exposures showed similar results, whereas effect estimates for other chemicals were weaker and imprecise.

CONCLUSIONS

In a multi-pollutant analysis of four classes of chemicals, early-life exposure to β-HCH and PFOS was associated with increased risk of ADHD, with suggestion of sex-specific effects for PFOS. The unexpected inverse associations between p,p'-DDT and higher HCB levels and ADHD could be due to live birth bias; alternatively, results may be due to chance findings.

The impact of environmental pollution on the quality of mother's milk

Breastfeeding is a gold standard of neonate nutrition because human milk contains a lot of essential compounds crucial for proper development of a child. However, milk is also a biofluid which can contain environmental pollution, which can have effects on immune system and consequently on the various body organs. Polychlorinated biphenyls are organic pollutants which have been detected in human milk. They have lipophilic properties, so they can penetrate to fatty milk and ultimately to neonate digestive track. Another problem of interest is the presence in milk of heavy metals-arsenic, lead, cadmium, and mercury-as these compounds can lead to disorders in production of cytokines, which are important immunomodulators. The toxicants cause stimulation or suppression of this compounds. This can lead to health problems in children as allergy, disorders in the endocrine system, end even neurodevelopment delay and disorder. Consequently, correlations between pollutants and bioactive components in milk should be investigated. This article provides an overview of environmental pollutants found in human milk as well as of the consequences of cytokine disorder correlated with presence of heavy metals. Graphical abstract.

Fetal toxicology

Toxic chemicals, either from natural sources or man-made, are ubiquitous in our environment. Many of the synthetic chemicals make life more comfortable and therefore production continues to grow. Simultaneously with the increase in production, an increase in neurodevelopmental disorders has been observed. Some chemicals are not biodegradable or have a very long half-life time and, despite the fact that production of a number of those chemicals has been severely reduced, they are still ubiquitous in the environment. Fetal exposure to toxic chemicals is dependent on maternal exposure to those chemicals and the developing stage of the fetus. Human evidence from epidemiologic studies is described with regard to the effect of prenatal exposure to various groups of neurotoxicants (alcohol, particulate fine matter, metals, and endocrine disrupting chemicals) on neurobehavior development. Data indicate that prenatal exposure to alcohol, polycyclic aromatic hydrocarbons, lead, methylmercury (MeHg), organophosphate pesticides (OPPs), and polychlorinated biphenyl ethers (PBDEs) impair cognitive development, whereas exposure to alcohol, MeHg, organochlorine pesticides and OPPs, polychlorinated biphenyls, PBDEs, and bisphenol A increases the risk of developing either attention deficit/hyperactivity and/or autism spectrum disorders. Psychomotor development appears to be less affected. However, data are not conclusive, which may depend on the assessment of exposure and the exposure level, among other factors.

Levels of polychlorinated biphenyls in human milk samples in European countries

Polychlorinated biphenyls (PCBs) are persistent pollutants, harmful to human health, which enter the human body mainly through food and bind to body fat. For these reasons their use in most countries is prohibited. Human milk has an advantage over other types of human samples in measuring human exposure to PCBs, as it is obtained with non-invasive sampling methods. In Europe, including Croatia, PCB levels have been monitored for many years. This review summarises PCB trends in human milk across Europe. The trend is generally downward, with higher levels prevailing in urban areas near industrial plants. The highest PCB levels were reported in the Czech Republic and Slovakia.

Legacy and alternative halogenated flame retardants in human milk in Europe: Implications for children's health

In this study, 10 polybrominated diphenyl ethers (PBDEs) and 19 alternative halogenated flame retardants (AFRs) were determined in >450 human milk samples across three European countries, representing northern, western and eastern Europe. This study provides first insights into the occurrence of selected AFRs in mother milk samples and compares them among three European countries. Sums of median concentrations of the most frequently detected PBDEs were 2.16, 0.88 and 0.45ngg^-1 lipid weight (lw) in Norway, the Netherlands and Slovakia, respectively. The sum of the concentrations of AFRs ranged from 0.14 to 0.25ngg^-1lw in all countries, which was 2 to 15 times less compared to Σ₇PBDEs. The Penta-BDE replacement, bis(2-ethylhexyl) tetrabromophthalate, BEH-TEBP, was present at the greatest concentrations of any of the AFRs and in some samples exceeded concentrations of BDE 47 and BDE 153. Four AFRs including bromobenzenes (hexabromobenzene, pentabromobenzene, pentabromotoluene) and another Penta-BDE replacement (2-ethylhexyl-2,3,4,5-tetrabromobenzoate, EH-TBB) were detected in >42% of all human milk samples. Because of the potential developmental neurotoxicity of the halogenated flame retardants, infant dietary intakes via breastfeeding were estimated; in four cases the intakes of BDE 47 exceeded the reference dose indicating that the present concentrations may pose a risk for children.

Rare-earth elements in human colostrum milk

Rare-earth elements (REEs) are used in a growing number of applications, and their release to environment has increased over the decades. Knowledge of REEs in human milk and factors that could possibly influence their concentration is scarce. This study evaluated the concentrations of 16 REEs (Ce, Eu, Er, Gd, La, Nd, Pr, Sc, Sm, Dy, Ho, Lu, Tb, Tm, Y, and Yb) in human colostrum milk collected from Polish women (n = 100) with the ICP-OES technique. The concentrations (mean ± SD) of Pr (41.9 ± 13.2 μg L^-1), Nd (11.0 ± 4.0 μg L^-1), La (7.1 ± 5.2 μg L^-1), and Er (2.2 ± 0.8 μg L^-1) were found above detection limits. The total mean ± SD concentration of detected REEs was 60.9 ± 17.8 μg L^-1. Current smokers displayed significantly increased Nd concentrations compared to women who had never smoked. No other associations between REEs in colostrum milk and age, diet in pregnancy (food supplement use and frequency of fish, meat, and vegetable consumption) or place of living (urban/rural) were found. This study adds to general understanding of the occurrence and turnover of REEs in women and human fluids.