Prenatal exposure to perfluoroalkyl acids and allergic diseases in early childhood

Gene expression patterns associated with PFOA exposure in Czech young men and women

Perfluorooctanoic acid (PFOA), a member of per- and polyfluoroalkyl substances (PFASs), has been widely used in manufacturing for decades. Currently, PFOA is strictly regulated, but due to its high stability and persistence, it is detected in both environmental as well as in human matrices. To elucidate mechanisms of PFOA toxicity in humans, we determined the genome-wide transcriptomic changes of peripheral blood mononuclear cells (PBMC) responding to PFOA exposure in a sex-stratified analysis. This work employed samples from 145 female and 143 male participants of the CELSPAC: YA study to characterize PFOA-associated transcripts in a broader context using computational analysis. PFOA-associated gene expression differed significantly between men and women, as only 2 % of mapped genes were expressed in both sexes. Disease-specific enrichment analysis revealed cancer and immune-related disease terms as those most enriched in male and female populations. Patterns of enriched terms within the gene set enrichment analysis indicated three main targets of PFOA toxicity: i) lipid metabolism for women; ii) cell cycle regulation for men; and iii) immune system response for both sexes. In summary, our genome-wide transcriptomics analysis described sex-specific differences in PFOA-associated gene expression and provided evidence about biological pathways underlying PFOA toxicity in humans.

Prenatal dietary exposure to mixtures of chemicals is associated with allergy or respiratory diseases in children in the ELFE nationwide cohort

INTRODUCTION

Prenatal exposure to environmental chemicals may be associated with allergies later in life. We aimed to examine the association between prenatal dietary exposure to mixtures of chemicals and allergic or respiratory diseases up to age 5.5 y.

METHODS

We included 11,638 mother-child pairs from the French "Étude Longitudinale Française depuis l'Enfance" (ELFE) cohort. Maternal dietary exposure during pregnancy to eight mixtures of chemicals was previously assessed. Allergic and respiratory diseases (eczema, food allergy, wheezing and asthma) were reported by parents between birth and age 5.5 years. Associations were evaluated with adjusted logistic regressions. Results are expressed as odds ratio (OR[95%CI]) for a variation of one SD increase in mixture pattern.

RESULTS

Maternal dietary exposure to a mixture composed mainly of trace elements, furans and polycyclic aromatic hydrocarbons (PAHs) was positively associated with the risk of eczema (1.10 [1.05; 1.15]), this association was consistent across sensitivity analyses. Dietary exposure to one mixture of pesticides was positively associated with the risk of food allergy (1.10 [1.02; 1.18]), whereas the exposure to another mixture of pesticides was positively but slightly related to the risk of wheezing (1.05 [1.01; 1.08]). This last association was not found in all sensitivity analyses. Dietary exposure to a mixture composed by perfluoroalkyl acids, PAHs and trace elements was negatively associated with the risk of asthma (0.89 [0.80; 0.99]), this association was consistent across sensitivity analyses, except the complete-case analysis.

CONCLUSION

Whereas few individual chemicals were related to the risk of allergic and respiratory diseases, some consistent associations were found between prenatal dietary exposure to some mixtures of chemicals and the risk of allergic or respiratory diseases. The positive association between trace elements, furans and PAHs and the risk of eczema, and that between pesticides mixtures and food allergy need to be confirmed in other studies. Conversely, the negative association between perfluoroalkyl acids, PAHs and trace elements and the risk of asthma need to be further explored.

Associations between prenatal exposure to per- and polyfluoroalkyl substances and wheezing and asthma symptoms in 4-year-old children: The Japan Environment and Children's Study

The effects of early-life exposure to per- and polyfluoroalkyl substances (PFAS) on the onset of asthma in children have been unclear. We examined the association between prenatal PFAS exposure and wheezing and asthma symptoms among 4-year-old children in a total of 17,856 mother-child pairs from the Japan Environment and Children's Study. Maternal first-trimester serum concentrations of six PFAS were used for the exposure assessment. We defined "wheeze ever," "current wheeze," "current symptoms of severe asthma," and "asthma ever" at the age of 4 years by the responses to the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, and "doctor-diagnosed asthma" by the response to a corresponding question. Multivariate logistic regression models were used to examine exposure-outcome associations. Our findings revealed that doubling of the PFOA concentration was associated with a reduced occurrence of "wheeze ever," yielding an adjusted odds ratio of 0.94 (95% CI: 0.90-0.98). Also, doubling in the concentrations of PFOA and PFHxS was associated with a decreased prevalence of "asthma ever," with adjusted odds ratios of 0.94 (95% CI: 0.88-1.00) and 0.95 (95% CI: 0.90-0.99), respectively. However, these associations were not significant after applying the Bonferroni correction. The estimated exposure-response curves were nearly linear with a subtle or flat slope. When stratified by the child's sex or the mother's history of asthma, most of the estimated confidence intervals were overlapped between each pair of strata. Regional stratification analysis indicated low-to-moderate heterogeneity in 12 exposure-outcome pairs and moderate-to-high heterogeneity in 9 out of the 30 examined pairs. This study found no clear associations between prenatal PFAS exposure and the prevalence of wheezing and asthma among children at the age of 4 years.

In utero exposure to poly- and perfluoroalkyl substances and children respiratory health in the three first years of life

BACKGROUND

Poly- and perfluoroalkyl substances (PFAS) are used in a wide range of products. Experimental studies suggested impaired lung development and pro-inflammatory response following exposure to some PFAS. We aimed to assess the associations between prenatal exposure to PFAS and children respiratory health.

METHODS

The study is based on 433 mother-child pairs. 26 PFAS were measured in maternal serum collected during pregnancy. Lung function parameters were measured at 2 months using tidal breathing flow-volume loops and multiple-breath nitrogen washout and at 36 months using oscillometry. Incidence of respiratory health diseases (asthma, wheeze, bronchitis, bronchiolitis) in the first 36 months of life was assessed by repeated questionnaires. A cluster-based analysis was applied to identify prenatal PFAS exposure patterns. Adjusted linear and logistic regressions were performed to assess the associations between PFAS exposure patterns as well as individual PFAS, and each respiratory health parameter.

RESULTS

We excluded 13 PFAS due to low quantification (<5%). Relying on the 13 remaining PFAS, we identified three exposure clusters, characterized by low (N = 163), medium (N = 236) and high (N = 51) pregnancy PFAS concentrations. Compared to children belonging to the low exposure group, children in the moderate exposure group had higher reactance at 7 Hz (X7) and lower frequency dependence of resistance between 7 Hz and 19 Hz (R7-19) at 36 months, suggesting better lung function. No association of any exposure metric was detected with respiratory diseases in the first 3 years of life.

CONCLUSIONS

Our study relying on both mixture and uni-pollutant analyses, does not provide evidence for a deleterious effect of prenatal PFAS exposure on respiratory health at an early age.

Impact of PFAS exposure on prevalence of immune-mediated diseases in adults in the Czech Republic

BACKGROUND

Per- and polyfluoroalkyl substances (PFASs) are emerging environmental contaminants with multiple hazardous properties including immunomodulation potency. Human exposure to PFASs has been associated with various immune-mediated diseases and outcomes. This study aimed to investigate the association between PFAS exposure and immune-mediated diseases such as allergies, eczemas, and autoimmune diseases in a population of adults in the Czech Republic.

METHODS

This study included 309 adults from the Central European Longitudinal Study of Parents and Children: Young Adults (CELSPAC: YA). 12 PFASs were measured in participants' serum by HPLC-MS/MS, 3 PFASs were removed from the subsequent analyses due to low detection frequency. The associations of 9 PFASs with 9 immune-mediated diseases were assessed by logistic regression. Furthermore, Bayesian kernel machine regression (BKMR) was used to estimate the effect of the PFAS mixture on immune-mediated diseases. All analyses were adjusted for sex, age, BMI, smoking, education, and family history of immune-mediated diseases. In cases of a statistically significant interaction of PFASs and sex, stratified analyses were performed for men and women.

RESULTS

Perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) were negatively associated with both atopic eczema (OR per IQR increase 0.58 (95% CI 0.37-0.90) for PFOA and 0.56 (0.32-0.95) for PFOS) and contact dermatitis (0.37 (0.16-0.85) for PFOA and 0.33 (0.11-0.94) for PFOS). Perfluoroundecanoate (PFUnDA) was negatively associated with pollen, dust, and mite allergy (0.62 (0.43-0.89)). BKMR modelling showed a negative tendency in the overall effect of PFAS mixture on immune-health outcomes. Based on the stratified analysis, sex was suggested to be an effect modifier in the association of PFOS and atopic eczema.

CONCLUSION

Our results contribute to the body of literature that observes the immunosuppressive effect of PFAS exposure during eczemas and allergies, both for PFASs individually and as a mixture.

Exposure to perfluoroalkyl substances and neonatal immunoglobulin profiles in the upstate KIDS study (2008-2010)

Infant exposure to per/polyfluoroalkyl compounds is associated with immune disruption. We examined associations between neonatal concentrations of perflurooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) and immunoglobulin (Ig) isotype profiles in a prospective cohort of infants. We measured Ig isotypes, including IgA, IgE, IgM and the IgG subclasses IgG1, IgG2, IgG3, and IgG4, and PFOA and PFOS in newborn dried bloodspots from N = 3175 infants in the Upstate KIDS Study (2008-2010). We examined the association between newborn Ig isotype levels and individual PFOS and PFOA concentrations using mixed effects regression models with a random intercept to account for twins among study participants. We assessed the joint effect PFOA and PFOS with quantile-based g-computation on all singletons and one randomly selected twin (N = 2901), with Ig categorized as above or below median value. Models were adjusted for infant sex, and maternal pre-pregnancy body mass index, race, parity, age and infertility treatment. In adjusted models, PFOA was inversely associated with IgE (coefficient = -0.12 per unit increase in PFOA, 95% CI: -0.065, -0.17), whereas IgG2, IgM, and IgA were positively associated with PFOA (coefficient for IgG2 = 0.22, 95% CI: 0.15, 0.27; coefficient for IgM = 0.11, 95% CI: 0.08, 0.15; and coefficient for IgA = 0.15, 95% CI: 0.07, 0.18). There was no relation between PFOS and Ig isotypes. Analysis of the joint effect of PFOA and PFOS showed an OR of 1.2 (95% CI: 1.04, 1.36) for IgA and OR of 1.12 (95% CI: 1.00, 1.24) for IgG2 levels above the median for every quartile increase. PFOA levels were significantly associated with elevated IgA, IgM, IgG2, and reduced levels of IgE in single-pollutant models. A small but significant joint effect of PFOA and PFOS was observed. Our results suggest that early exposure to PFOA and PFOS may disrupt neonatal immunoglobulin levels.

Global performance and trends of research on per- and polyfluoroalkyl substances (PFASs) between 2001 and 2018 using bibliometric analysis

Per- and polyfluoroalkyl substances (PFASs) are widely used in food packaging, non-stick pots, and surfactants. However, their persistence in the environment, hazardous nature, and potential for bioaccumulation and long-range transport have alarmed an increasing number of scholars and research institutions. Although several literature reviews on PFASs research exist, only a few of them have considered bibliometric indices. In this study, 3,373 PFASs-related articles published between 2001 and 2018 were analyzed using a bibliometric analysis method based on the Science Citation Index (SCI) Expanded. The software tools for mapping knowledge domain (MKD) (VOSviewer and Science of Science (Sci2)) were used to analyze the performance of contributors and PFASs research topics, hotspots, and trends. Our results reveal that the number of PFASs-related articles published annually has increased significantly, with most originating from the United States (followed by those from China). The Chinese Academy of Sciences has published the most articles. A comprehensive analysis of title, keywords, and keywords plus showed that PFASs research hotspots include humans, precursors, and detection methods, with the main focuses being environmental science, toxicology, and environmental engineering. The four main research topics of PFASs were identified, and a literature review was carried out for each one. Overall, this study can supply researchers with a deeper understanding of the development of PFASs studies and provide a comprehensive data reference for researchers to further grasp the research direction in this field.

Association between prenatal polycyclic aromatic hydrocarbons and infantile allergic diseases modified by maternal glutathione S-transferase polymorphisms: results from the MOCEH birth cohort

Background

Prenatal exposure to polycyclic aromatic hydrocarbons (PAH) has been linked to allergic disease onset. Variations in the glutathione S-transferase (GST) gene family can impact the progression of allergic diseases. We sought to examine the association between prenatal PAH exposure and infantile allergic diseases in 6-month-old infants, and how maternal glutathione S-transferase M1 (GSTM1) or T1 (GSTT1) polymorphism affects the association between prenatal PAH exposure and allergic diseases in the Mothers and Children's Environmental Health (MOCEH) study.

Methods

The study sample comprised 349 infants and their mothers from the MOCEH study, for whom 1-hydroxypyrene (1-OHP) and 2-naphthol were measured in both the early period of pregnancy and late period of pregnancy. An infant was deemed to be affected by an allergic disease if diagnosed with or if developed at least one of the allergic diseases. A logistic regression analysis was performed to study the association between urinary 1-OHP and 2-naphthol levels during pregnancy and allergic diseases in 6-month-old infants. Furthermore, analyses stratified by maternal GSTM1 or GSTT1 present/null polymorphisms were performed.

Results

The risk of allergic diseases in 6-month-old infants was significantly increased in accordance with an increase in urinary 1-OHP during the early period of pregnancy (odds ratio [OR]: 1.84; 95% confidence interval [CI]: 1.05, 3.23; by one log-transformed unit of 1-OHP μg/g creatinine). The increased risk of infantile allergic diseases associated with urinary 1-OHP during the early period of pregnancy was limited to the maternal GSTT1 null type (OR: 2.69; 95% CI: 1.17, 6.21, by one log-transformed unit of 1-OHP μg/g creatinine); however, the Relative Excess Risk due to Interaction was not statistically significant.

Conclusions

The present study found that infantile allergic diseases could be affected by intrauterine PAH exposure, particularly in the early prenatal period and the risk was limited to the maternal GSTT1 null type.

Perfluoroalkyl substances exposure and immunity, allergic response, infection, and asthma in children: review of epidemiologic studies

Background

Increased exposure to perfluoroalkyl substances (PFAS) potentially affects infant and childhood health through immunosuppression. Given rapidly evolving research on PFAS, it is important to comprehensively examine the impact of PFAS exposure among the pediatric population as new research becomes available due to potential fragility of the developing immune system.

Objectives

This review assessed the effects of PFAS fetal, infant and childhood exposures upon the development of immune function during early life stages.

Methods

Researchers completed a literature review, searching PubMed for human studies published since 2010 for PFAS and health outcomes among infants and children. Included articles incorporated key search terms in the title or abstract; non-research reports and non-English papers were excluded. The search identified 518 studies for possible inclusion. Following hands-on review, 34 were determined relevant. Subsequent analyses found 8 additional relevant articles, totaling 42 studies.

Results

Major immune-related sequelae from PFAS exposures on infant and child health outcomes documented in recent literature include:

• Strong indication of immunosuppression, with diminished childhood antibody response to vaccination, particularly with PFOA, PFOS and PFHxS exposures.

• Some indication of increased risks of childhood infectious diseases/infections, particularly from PFOS exposures.

• Limited indication of an effect of PFAS exposure on allergic reactions/allergen specific IgE antibodies.

• Limited indication of an effect of PFAS exposure on atopic dermatitis (AD).

• Limited indication of an effect of PFAS exposure on asthma and lung function.

Conclusion

This review summarizes recent findings of PFAS effects on infant and childhood immune health. Evidence of immunosuppression, diminished vaccine efficacy, and increased risk of infections, allergies, asthma and AD were described following in utero, infant, and early childhood PFAS exposures. Further investigation is warranted to characterize PFAS exposure pathways and potential modes of action in relation to PFAS effects on the developing immune system. Incontrovertible proof of PFAS immunotoxic effects could optimally be obtained by a large prospective study cohort of mothers and children from infancy through school-age. Regular assessments of circulating antibodies and response to infant and childhood vaccines during growth years could prove invaluable.

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This review summarizes findings of PFAS effects on infant and child immune health.

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In utero, infant, and early childhood PFAS exposures were examined.

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Strong evidence of PFAS exposure on diminished childhood antibody vaccination response.

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Moderate evidence of PFAS exposure on increased risk of childhood infectious diseases.

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Limited evidence of PFAS exposure on allergic reactions, atopic dermatitis, asthma.

Perfluorooctane sulfonate and bisphenol A induce a similar level of mast cell activation via a common signaling pathway, Fyn-Lyn-Syk activation

Perfluoroalkyl compounds (PFCs) as food contaminants are widely distributed persistent organic pollutants (POPs) and have been suggested to induce immune dysfunction. However, their effects on immune function are not conclusive. Mast cells play a central role in allergic and non-allergic inflammatory responses. Therefore, we have examined the effects of PFCs (PFHxS, PFOA, PFOS) on mast cell-mediated inflammatory responses using in vitro mouse bone marrow-derived mast cells (BMMCs) and human mast cells (HMC-1) and in vivo mice model. The effects of PFCs were compared with those of bisphenol A (BPA), a well-studied environmental pollutant. Among PFCs tested, PFOS had the highest effects. Both PFOS and BPA increased degranulation and production of inflammatory eicosanoids in mast cells at a similar level, which subsequently led to increased skin edema and serum LTC₄ and PGD₂ in mice. Both PFOS and BPA increased not only downstream signaling (PLCγ1, AKT, ERK), but also upstream signaling (Fyn, Lyn, Syk/LAT) in mast cells. Taken together, PFOS and BPA induce mast cell-mediated inflammatory responses via a common signaling pathways. Our results may help establish the scientific basis for understanding the etiology of mast cell-mediated inflammatory responses and improve the immune dysfunction risk assessment for emerging POPs such as PFCs.

Hokkaido birth cohort study on environment and children's health: cohort profile 2021

BACKGROUND

The Hokkaido Study on Environment and Children's Health is an ongoing study consisting of two birth cohorts of different population sizes: the Sapporo cohort and the Hokkaido cohort. Our primary objectives are to (1) examine the effects that low-level environmental chemical exposures have on birth outcomes, including birth defects and growth retardation; (2) follow the development of allergies, infectious diseases, and neurobehavioral developmental disorders, as well as perform a longitudinal observation of child development; (3) identify high-risk groups based on genetic susceptibility to environmental chemicals; and (4) identify the additive effects of various chemicals, including tobacco.

METHODS

The purpose of this report is to provide an update on the progress of the Hokkaido Study, summarize recent results, and suggest future directions. In particular, this report provides the latest details from questionnaire surveys, face-to-face examinations, and a collection of biological specimens from children and measurements of their chemical exposures.

RESULTS

The latest findings indicate different risk factors of parental characteristics on birth outcomes and the mediating effect between socioeconomic status and children that are small for the gestational age. Maternal serum folate was not associated with birth defects. Prenatal chemical exposure and smoking were associated with birth size and growth, as well as cord blood biomarkers, such as adiponectin, leptin, thyroid, and reproductive hormones. We also found significant associations between the chemical levels and neuro development, asthma, and allergies.

CONCLUSIONS

Chemical exposure to children can occur both before and after birth. Longer follow-up for children is crucial in birth cohort studies to reinforce the Developmental Origins of Health and Disease hypothesis. In contrast, considering shifts in the exposure levels due to regulation is also essential, which may also change the association to health outcomes. This study found that individual susceptibility to adverse health effects depends on the genotype. Epigenome modification of DNA methylation was also discovered, indicating the necessity of examining molecular biology perspectives. International collaborations can add a new dimension to the current knowledge and provide novel discoveries in the future.

Associations among perfluorooctanesulfonic/perfluorooctanoic acid levels, nuclear receptor gene polymorphisms, and lipid levels in pregnant women in the Hokkaido study

The effect of interactions between perfluorooctanesulfonic (PFOS)/perfluorooctanoic acid (PFOA) levels and nuclear receptor genotypes on fatty acid (FA) levels, including those of triglycerides, is not clear understood. Therefore, in the present study, we aimed to analyse the association of PFOS/PFOA levels and single-nucleotide polymorphisms (SNPs) in nuclear receptors with FA levels in pregnant women. We analysed 504 mothers in a birth cohort between 2002 and 2005 in Japan. Serum PFOS/PFOA and FA levels were measured using liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry. Maternal genotypes in PPARA (rs1800234; rs135561), PPARG (rs3856806), PPARGC1A (rs2970847; rs8192678), PPARD (rs1053049; rs2267668), CAR (rs2307424; rs2501873), LXRA (rs2279238) and LXRB (rs1405655; rs2303044; rs4802703) were analysed. When gene-environment interaction was considered, PFOS exposure (log₁₀ scale) decreased palmitic, palmitoleic, and oleic acid levels (log₁₀ scale), with the observed β in the range of - 0.452 to - 0.244; PPARGC1A (rs8192678) and PPARD (rs1053049; rs2267668) genotypes decreased triglyceride, palmitic, palmitoleic, and oleic acid levels, with the observed β in the range of - 0.266 to - 0.176. Interactions between PFOS exposure and SNPs were significant for palmitic acid (P_int = 0.004 to 0.017). In conclusion, the interactions between maternal PFOS levels and PPARGC1A or PPARD may modify maternal FA levels.

PFAS Environmental Pollution and Antioxidant Responses: An Overview of the Impact on Human Field

Due to their unique properties, perfluorinated substances (PFAS) are widely used in multiple industrial and commercial applications, but they are toxic for animals, humans included. This review presents some available data on the PFAS environmental distribution in the world, and in particular in Europe and in the Veneto region of Italy, where it has become a serious problem for human health. The consumption of contaminated food and drinking water is considered one of the major source of exposure for humans. Worldwide epidemiological studies report the negative effects that PFAS have on human health, due to environmental pollution, including infertility, steroid hormone perturbation, thyroid, liver and kidney disorders, and metabolic disfunctions. In vitro and in vivo researches correlated PFAS exposure to oxidative stress effects (in mammals as well as in other vertebrates of human interest), produced by a PFAS-induced increase of reactive oxygen species formation. The cellular antioxidant defense system is activated by PFAS, but it is only partially able to avoid the oxidative damage to biomolecules.

Effect of prenatal exposure to per- and polyfluoroalkyl substances on childhood allergies and common infectious diseases in children up to age 7 years: The Hokkaido study on environment and children's health

Per- and polyfluoroalkyl substances (PFAS) are widely used bio-accumulative chemicals in many industrial and household products. Experimental studies reported that exposure to PFAS results in immunotoxicity. We have previously reported that prenatal exposure to PFAS decreased the risk of allergies, while it increased the risk of infectious diseases at ages 2 and 4 years. However, it remains unclear whether the adverse effects of PFAS on allergies and infectious diseases continue until a reliable age of diagnosing allergies. This study aimed at investigating the effects of prenatal exposure to PFAS on the prevalence of allergies and infectious diseases in children up to age 7, from the Hokkaido Study. Among mother-child pairs enrolled in the Hokkaido study and followed up until the age of 7 years, 2689 participants with maternal PFAS, 1st trimester of pregnancy and 7-year-old questionnaire survey data were included in this study. Eleven PFAS in the 3rd-trimester plasma were measured using ultra-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry. Wheeze, rhino-conjunctivitis, and eczema were defined using the International Study of Asthma and Allergies on Childhood (ISAAC) questionnaire. History childhood infectious diseases diagnosed by a doctor was assessed by a mother-reported questionnaire at child's age 7. The relative risk of childhood allergies was calculated by generalized estimating equation models. The odds ratio of an episode of infectious diseases was calculated by logistic regression analysis, adjusted for potential confounders. The prevalence of various allergies and infectious diseases was: wheeze, 11.9%; rhino-conjunctivitis, 11.3%; eczema, 21.0%; chickenpox, 61.5%; otitis media, 55.7%; pneumonia, 30.6%; and respiratory syncytial virus infection, 16.8%. Prenatal exposure to perfluorooctanoic acid, perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA) was inversely associated with rhino-conjunctivitis, while that for perfluorooctanoate (PFOA), perfluorooctane sulfonate, PFUnDA, perfluorododecanoic acid (PFDoDA), and perfluorotridecanoic acid was inversely associated with eczema. For infectious diseases, PFDA and PFDoDA were associated with increased risk of pneumonia and PFOA was associated with increased risk of RSV infection among children not having any siblings (only-one-child). Our results corroborate the hypothesis on immunosuppressive and immunomodulating effects of PFAS on allergies and infectious diseases in children. These effects observed previously at 2 and 4 years continued until the age of 7 years. However, additional studies assessing inflammatory biomarkers along with ISAAC questionnaires, doctor-diagnosed allergies, and longer follow-ups are necessary to better assess the effects of exposure to chemicals on human immune outcomes.

Risk to human health related to the presence of perfluoroalkyl substances in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluoroalkyl substances (PFASs) in food. Based on several similar effects in animals, toxicokinetics and observed concentrations in human blood, the CONTAM Panel decided to perform the assessment for the sum of four PFASs: PFOA, PFNA, PFHxS and PFOS. These made up half of the lower bound (LB) exposure to those PFASs with available occurrence data, the remaining contribution being primarily from PFASs with short half-lives. Equal potencies were assumed for the four PFASs included in the assessment. The mean LB exposure in adolescents and adult age groups ranged from 3 to 22, the 95th percentile from 9 to 70 ng/kg body weight (bw) per week. Toddlers and 'other children' showed a twofold higher exposure. Upper bound exposure was 4- to 49-fold higher than LB levels, but the latter were considered more reliable. 'Fish meat', 'Fruit and fruit products' and 'Eggs and egg products' contributed most to the exposure. Based on available studies in animals and humans, effects on the immune system were considered the most critical for the risk assessment. From a human study, a lowest BMDL 10 of 17.5 ng/mL for the sum of the four PFASs in serum was identified for 1-year-old children. Using PBPK modelling, this serum level of 17.5 ng/mL in children was estimated to correspond to long-term maternal exposure of 0.63 ng/kg bw per day. Since accumulation over time is important, a tolerable weekly intake (TWI) of 4.4 ng/kg bw per week was established. This TWI also protects against other potential adverse effects observed in humans. Based on the estimated LB exposure, but also reported serum levels, the CONTAM Panel concluded that parts of the European population exceed this TWI, which is of concern.

Perfluoroalkyl substances, airways infections, allergy and asthma related health outcomes - implications of gender, exposure period and study design

INTRODUCTION

Exposure to perfluoroalkyl substances (PFASs) has been inconsistently associated with asthma, allergic diseases and airways infections in early childhood. The aim of the study was, therefore, to investigate the effect of childhood exposure to PFASs on asthma and allergy related outcomes and on airways infections before and during puberty using the prospective birth cohort Environment and Childhood Asthma (ECA) Study. Aspects of gender, exposure period and study design (cross-sectional and longitudinal) were also taken into consideration.

MATERIAL AND METHODS

Included in the study was 378 participants with PFAS measurements at age 10 years and follow-up data at ages 10 years (cross sectional data) and 16 years (longitudinal data). Eight PFASs with at least 70% of measurements above the limit of quantification (LOQ) in the child's serum were included in the present study: perfluoroheptanoate (PFHpA), perfluorooctanoate (PFOA), perfluourononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA), perfluorohexane sulfonate (PFHxS), perfluoroheptane sulfonate (PFHpS) and perfluorooctane sulfonate (PFOS). The PFAS levels were converted into interquartile range (IQR). In addition, perfluorooctane sulfonamide (PFOSA) detected in 60% of the samples, was recoded into "not detected /detected". Binomial, multinomial and linear regression were used, followed by Bonferroni adjustment to correct for multiple comparisons. Sensitivity analyses evaluating the effect of extreme PFAS values and gender were performed.

RESULTS

In the cross sectional data at 10 years a positive statistically significant association was seen between PFHpA and asthma in girls. In the longitudinal data, PFNA, PFDA and PFUnDA were inversely associated with atopic dermatitis (AD) in girls and with PFHxS in all participants and in boys. Further, PFNA and PFHpS were positively associated with rhinitis in girls and with PFOA in all participants. There seems to be a suggestive pattern of increased risk of allergic sensitisation in all participants and a decreased risk in boys, but due to different results in main and sensitivity analyses these findings should be interpreted with caution. No associations were found between PFASs and lung function. For airways infections and longitudinal data, PFDA was inversely associated with common cold, while positive association was found for PFHpA, PFOA, PFHpS and PFOS and lower respiratory tract infections (LRTI).

DISCUSSION AND CONCLUSION

Our results lend further support for an immunosuppressive effect of PFASs on AD and LRTI. Gender seems to be important for some exposure-health associations. No clear pattern in exposure-health associations was observed with regard to exposure period or study design, with the exception of asthma where significant findings have mostly been reported in cross-sectional studies.

Association between perfluoroalkyl substance exposure and thyroid hormone/thyroid antibody levels in maternal and cord blood: The Hokkaido Study

BACKGROUND

Thyroid antibodies (TAs) are the most common cause of hypothyroidism during gestation. Although previous studies found that prenatal exposure to perfluoroalkyl substances (PFASs) disrupts thyroid hormones (THs) in humans, their effects on TAs during the perinatal period have not been investigated.

OBJECTIVE

To explore the associations between prenatal exposure to eleven different PFASs from two different groups (carboxylates and sulfonates) and the expression of THs and TAs in maternal and cord blood while considering maternal TA status.

METHODS

In a prospective birth cohort (the Hokkaido Study), we included 701 mother‑neonate pairs recruited in 2002-2005 for whom both prenatal maternal and cord blood samples were available. Eleven PFASs were measured in maternal plasma obtained at 28-32 weeks of gestation using ultra-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry. THs and TAs including thyroid stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured in maternal blood during early pregnancy (median 11 gestational weeks), and in cord blood at birth.

RESULTS

The median levels of TgAb and TPOAb in maternal serum were 15.0 and 6.0 IU/mL, respectively. The median TgAb level in neonates was 38.0 IU/mL, and TPOAb were detected in only 12.3% of samples. Maternal FT3 level was positively associated with PFAS levels in both TA-positive and TA-negative mothers. Maternal perfluorooctanoate was inversely associated with maternal TPOAb. Among boys, some maternal PFASs were associated with higher TSH and lower FT3 levels in maternal TA-negative group, while perfluorodecanoic acid was associated with lower TSH in maternal TA-positive group. Among girls, some PFAS of mothers showed associations with lower TSH and higher FT3 in maternal TA-negative group, while perfluorododecanoic acid was associated with lower FT4 in maternal TA-positive. Maternal PFASs showed associations with boy's TgAb inversely in maternal TA-negative group and with girl's TgAb positively in maternal TA-positive group.

CONCLUSIONS

Our results suggest thyroid disrupting effects of PFAS exposure and susceptibility vary depending on maternal TA levels.

Association between prenatal exposure to perfluoroalkyl substances and asthma-related diseases in preschool children

Thus far, the few studies on the associations between perfluoroalkyl substances (PFASs) and asthma in children have yielded inconsistent results. In this study, we aimed to evaluate whether and to what extent prenatal PFASs exposure is associated with childhood asthmatic diseases. Eight PFASs were measured in cord blood drawn from 358 children in the Shanghai Allergy Birth Cohort, and a 5-year follow-up plan was completed. Asthma was diagnosed and reported by pediatric respiratory physicians via repeated symptoms (wheezing and coughing) and laboratory examination (Immunoglobulin E level test and skin prick test). A total of 26.6% and 17.4% subjects were diagnosed with wheezing and asthma, respectively. Multivariable logistic regression and piecewise linear regression were applied, and no association was found between PFASs and asthma or wheezing. However, cord serum PFOA, PFOS, and PFDA were positively correlated with serum total IgE in 5-year-old children as the level of the former beyond the turning point (4.37 ng/mL, 2.95 ng/mL, and 0.42 ng/mL, respectively), but negatively with IgE before it reach turnning point.

Derivation of a chronic reference dose for perfluorohexane sulfonate (PFHxS) for reproductive toxicity in mice

Perfluorohexane sulfonate (PFHxS) is a six-carbon perfluoroalkyl sulfonic acid that was used as an industrial surfactant, but is now found as an environmental contaminant worldwide. In addition to its use as an industrial surfactant, it is a legacy contaminant from the use of aqueous film-forming foams. Despite its widespread occurrence in the environment and evidence of biological activity associated with PFHxS and similar perfluoroalkyl sulfonic acids in rodents, there is no oral toxicity value currently available from the IRIS Database. To derive an oral reference dose (RfD) for PFHxS, available toxicity studies were reviewed using a weight-of-evidence approach. A 42-day mouse reproductive study was chosen as the critical study for the derivation of the oral RfD. Benchmark dose modeling was utilized to derive a point of departure (POD) for a reduction in litter size. A 95% lower confidence limit on the benchmark dose (BMDL) of 13,900 ng/mL (serum PFHxS) was modeled for a reduction in litter size. An oral RfD for PFHxS of 4.0 ng/kg/d was calculated by conversion of the BMDL to a human equivalent oral dose using a human half-life adjusted dosimetric conversion factor and the application of a total uncertainty factor of 300. Additional research is needed to better characterize the toxicity associated with oral exposure to PFHxS and refine the development of toxicity values.

Prenatal perfluorooctanoic acid exposure is associated with early onset atopic dermatitis in 5-year-old children

Atopic dermatitis (AD) is the most common childhood skin disease and the first step of atopic march. Perfluoroalkyl substance (PFAS) exposure is associated with atopic diseases, including AD. However, whether PFAS exposure is related to earlier AD onset remains unclear. We aimed to investigate the association between prenatal PFAS exposure and earlier onset of AD in children in a 5-year follow-up study. From 2001 to 2005, 1264 mother-infant pairs were recruited from eight Taiwanese maternity hospitals. PFAS levels were analyzed from cord blood. Information on children's health status, including AD occurrence, was obtained via phone interviews at multiple time points. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) concentrations were measured by ultra-high performance liquid chromatography/tandem mass spectrometry. Cox proportional hazards models assessed associations between prenatal PFAS exposure and early onset AD. Overall, 863 mother-infant pairs with complete measurements were recruited. The prevalence of physician-diagnosed AD before 5 years of age was 7.1%. PFOA and PFOS concentrations were grouped based on whether they were above the 75th percentile. PFOA exposure was positively associated with earlier onset of AD (Kaplan-Meier estimate, p = 0.014). In the Cox model, after adjusting for sex, family income, parental atopy, breast feeding, and maternal age at childbirth, significance was observed in children above the upper quartile (≥75th) of the PFOA group (hazard ratio: 1.89; 95% confidence interval, 1.10-3.16). Our findings suggested that children with higher prenatal PFOA exposure have a higher risk of earlier AD development. Minimizing early life PFAS exposure may help inhibit AD development.

Prenatal exposure to perfluoroalkyl substances, immune-related outcomes, and lung function in children from a Spanish birth cohort study

BACKGROUND

Prenatal exposure to perfluoroalkyl substances (PFASs) has been associated with impaired immune and respiratory health during childhood but the evidence is inconsistent and limited for lung function. We studied the association between prenatal PFASs exposure and immune and respiratory health, including lung function, up to age 7 years in the Spanish INMA birth cohort study.

METHODS

We assessed four PFASs in maternal plasma samples collected during the 1st trimester of pregnancy (years: 2003-2008): perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorononanoate (PFNA). Mothers reported the occurrence (yes/no) of lower respiratory tract infections, wheezing, asthma, and eczema in the previous 12 months at 1.5 and 4 years of the child (n = 1188) and at 7 years (n = 1071). At ages 4 (n = 503) and 7 (n = 992) years lung function was assessed using spirometry tests.

RESULTS

The most abundant PFASs were PFOS and PFOA (geometric means: 5.80 and 2.31 ng/mL, respectively). The relative risk of asthma during childhood per each doubling in PFNA concentration was 0.74 (95 CI%: 0.57, 0.96). The relative risk of eczema during childhood per every doubling in PFOS concentration was 0.86 (95 CI%: 0.75, 0.98). Higher PFOA concentrations were associated with lower forced vital capacity and lower forced expiratory volume in 1 s z-scores at 4 years [β (95 CI %): -0.17 (-0.34, -0.01) and -0.13 (-0.29, 0.03), respectively], but not at 7 years.

CONCLUSION

This longitudinal study suggests that different PFASs may affect the developing immune and respiratory systems differently. Prenatal exposure to PFNA and PFOS may be associated with reduced risk of respiratory and immune outcomes, particularly asthma and eczema whereas exposure to PFOA may be associated with reduced lung function in young children. These mixed results need to be replicated in follow-up studies at later ages.

Developmental Exposures to Perfluoroalkyl Substances (PFASs): An Update of Associated Health Outcomes

PURPOSE OF REVIEW

We reviewed and summarized the epidemiological evidence for the influence that pre- and postnatal exposures to perfluoroalkyl substances (PFASs) may have on health outcomes in offspring, with a particular focus on birth outcomes and postnatal growth, immunomodulatory effects and neurodevelopment.

RECENT FINDINGS

PFASs are persistent organic pollutants that have been widely produced and used in a range of commercial products since the 1950s. Human exposures to PFASs are nearly ubiquitous globally, but studies that addressed potential health effects of PFASs have only begun to accumulate in recent years. Animal studies suggest adverse effects resulting from developmental encompasses prenatal exposures to PFASs. In humans, the developing fetus is exposed to PFASs via active or passive placenta transfer, while newborns might be exposed via breastfeeding or PFAS in the home environment. Overall, epidemiological findings are consistent and suggest possible associations with fetal and postnatal growth and immune function, while the findings on neurodevelopmental endpoints to date are rather inconclusive. Methodological challenges and future directions for PFASs-focused research are discussed.

Maternal levels of perfluoroalkyl substances (PFASs) during pregnancy and childhood allergy and asthma related outcomes and infections in the Norwegian Mother and Child (MoBa) cohort

INTRODUCTION

Prenatal exposure to perfluoroalkyl substances (PFASs) has been inconsistently associated with asthma and allergic diseases and increased number of infections in early childhood. We examined the association of PFASs measured in pregnancy with childhood asthma, allergies and common infectious diseases in a prospective pregnancy cohort followed to age 7 years.

MATERIAL AND METHODS

Six PFASs (out of 19 measured) with at least 80% of measurements above the limit of quantification (LOQ) in maternal plasma during pregnancy in two subcohorts of the Norwegian Mother and Child Cohort Study (MoBa) were analyzed in relation to health outcomes: perfluorooctane sulfonic acid (PFOS), acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUnDA), and perfluoroheptane sulfonic acid (PFHpS). Follow-up questionnaires were completed at 3 years by 1270 women and at 7 years by 972 women among the 1943 with pregnancy questionnaire and PFAS measures. Health outcomes included parent reports of child's symptoms or doctor diagnosed asthma and allergic conditions at age 7 years and parent-reported frequency of various infections at 3 and 7 years of age. Logistic and Poisson regression were used. The false discovery rate was controlled at 5%. Sensitivity analyses on gender were performed.

RESULTS

Among the allergy and asthma outcomes, a statistically significant inverse association was seen between PFUnDA concentrations and ever having atopic eczema in girls. PFUnDA also tended to be inversely associated with both wheeze and asthma. For infections from 0 to 3 and 6 to 7 years, 11 significant positive associations were seen between PFASs and airways infections (bronchitis/pneumonia, throat infection, pseudocroup), ear infection and gastric flu/diarrhea; whereas 6 inverse associations were seen for pseudocroup, ear infections and urinary tract infections. The majority of the findings with respect to infectious diseases were found in girls only.

DISCUSSION

With the exception of an inverse association between PFUnDA and eczema, and a tendency of a similar association for wheeze and asthma, maternal PFAS levels during pregnancy showed little association with asthma or allergy related outcomes. Findings from the present study suggest immunosuppressive effects of PFASs on airways infections, such as bronchitis/pneumonia and throat infections, as well as diarrhea/gastric flu. Our results indicate a possible role of gender in the PFAS-health outcome associations.

Exposure to per-fluoroalkyl and polyfluoroalkyl substances leads to immunotoxicity: epidemiological and toxicological evidence

In this perspective, we evaluate key and emerging epidemiological and toxicological data concerning immunotoxicity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) and seek to reconcile conflicting conclusions from two reviews published in 2016. We summarize ways that immunosuppression and immunoenhancement are defined and explain how specific outcomes are used to evaluate immunotoxicity in humans and experimental animals. We observe that different approaches to defining immunotoxicological outcomes, particularly those that do not produce clinical disease, may lead to different conclusions from epidemiological and toxicological studies. The fundamental point that we make is that aspects of epidemiological studies considered as limitations can be minimized when data from toxicological studies support epidemiological findings. Taken together, we find that results of epidemiological studies, supported by findings from toxicological studies, provide strong evidence that humans exposed to PFOA and PFOS are at risk for immunosuppression.

Prenatal perfluorooctanoic acid exposure and glutathione s-transferase T1/M1 genotypes and their association with atopic dermatitis at 2 years of age

Background

Perfluoroalkyl substance (PFAS) exposure was found associated with atopic diseases. Atopic dermatitis (AD) is a childhood skin disorder. However, the effect of interaction between PFASs and glutathione S-transferase (GST) T1/M1 genotype on AD remains unclear.

Objective

To investigate the association between gene-environmental interaction and childhood AD using a birth cohort study.

Methods

From 2001 to 2005, 1,264 mother–newborn pairs were recruited from eight Taiwanese maternity hospitals. PFAS levels and Genotypes were analysed from cord blood. Information on children’s health status including AD occurrence was obtained via phone interviews at 6 months and 2 years. Cord plasma concentrations of nine PFASs were measured via ultra-high performance liquid chromatography/tandem mass spectrometry. GSTT1/M1 was genotyped (null/present) via polymerase chain reaction. Environment-gene interaction effects on AD were assessed using multiple logistic regression analysis.

Results

Overall, 839 mother–newborn pairs completed all measurements. The prevalence of ever having physician-diagnosed AD by 2 years of age was 5.4%. Among PFASs, perfluorooctanoic acid (PFOA) was positively associated with AD adjusted for potential confounders. After grouping PFOA levels into three groups: undetected, below and above the median in those with detected, children in above the median group who had the GSTT1-null, or GSTM1-null genotype exhibited a higher odds ratio for AD (OR [95%CI] = 3.45 [1.26–9.99] and 2.92 [1.12–7.91], respectively) as compared to the undetected group.

Conclusions

Our data demonstrated that in-utero PFOA exposure with GSTT1/M1 null genotype were associated with AD. Minimizing early-life PFAS exposure may help against AD development, especially in genetically susceptible individuals.

Per- and polyfluoroalkyl substances in human breast milk and current analytical methods

Per- and polyfluoroalkyl substances (PFASs) have since become a major health concern as they have been reportedly found in human tissues, blood and breast milk. The main aim of the study was to review the current data on PFASs in human breast milk, including the challenges of analysis as well as the possible modes of transfer from maternal blood. In this paper, previously published data on the concentrations of PFASs in human breast milk from around the world were reviewed and summarised. Eligible studies with reference lists published before 1 June 2017 were included by searching several databases (including Scopus, ScienceOpen and SciFinder). From this search, studies with the number of participants in each study ranging from 2 to 1237 were identified. The review indicated that based on the structural profiles and concentration levels, there was variation in the geographical distribution of these compounds in breast milk. Although there are no recorded investigations on the modes of transfer from maternal blood to breast milk, literature suggests that the PFASs tend to be transferred through binding to various proteins. The review also examined the different sample preparation and analytical methods employed to measure the concentrations of PFASs in human breast milk. This showed that solid phase extraction was the most common extraction method. After extraction, liquid chromatography coupled with tandem mass spectrometry was the most common analysis method. Since several of these methods were initially dedicated to monitoring PFASs in food and water, they demonstrate some limitations with regard to specificity and sensitivity to human fluids. Additionally, there are currently no published records of certified reference materials and/or proficiency scheme devoted to standardising PFAS concentrations in breast milk.

Risk to human health related to the presence of perfluorooctane sulfonic acid and perfluorooctanoic acid in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in food. Regarding PFOS and PFOA occurrence, the final data set available for dietary exposure assessment contained a total of 20,019 analytical results (PFOS n = 10,191 and PFOA n = 9,828). There were large differences between upper and lower bound exposure due to analytical methods with insufficient sensitivity. The CONTAM Panel considered the lower bound estimates to be closer to true exposure levels. Important contributors to the lower bound mean chronic exposure were 'Fish and other seafood', 'Meat and meat products' and 'Eggs and egg products', for PFOS, and 'Milk and dairy products', 'Drinking water' and 'Fish and other seafood' for PFOA. PFOS and PFOA are readily absorbed in the gastrointestinal tract, excreted in urine and faeces, and do not undergo metabolism. Estimated human half-lives for PFOS and PFOA are about 5 years and 2-4 years, respectively. The derivation of a health-based guidance value was based on human epidemiological studies. For PFOS, the increase in serum total cholesterol in adults, and the decrease in antibody response at vaccination in children were identified as the critical effects. For PFOA, the increase in serum total cholesterol was the critical effect. Also reduced birth weight (for both compounds) and increased prevalence of high serum levels of the liver enzyme alanine aminotransferase (ALT) (for PFOA) were considered. After benchmark modelling of serum levels of PFOS and PFOA, and estimating the corresponding daily intakes, the CONTAM Panel established a tolerable weekly intake (TWI) of 13 ng/kg body weight (bw) per week for PFOS and 6 ng/kg bw per week for PFOA. For both compounds, exposure of a considerable proportion of the population exceeds the proposed TWIs.

Risk to human health related to the presence of perfluorooctane sulfonic acid and perfluorooctanoic acid in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in food. Regarding PFOS and PFOA occurrence, the final data set available for dietary exposure assessment contained a total of 20,019 analytical results (PFOS n = 10,191 and PFOA n = 9,828). There were large differences between upper and lower bound exposure due to analytical methods with insufficient sensitivity. The CONTAM Panel considered the lower bound estimates to be closer to true exposure levels. Important contributors to the lower bound mean chronic exposure were 'Fish and other seafood', 'Meat and meat products' and 'Eggs and egg products', for PFOS, and 'Milk and dairy products', 'Drinking water' and 'Fish and other seafood' for PFOA. PFOS and PFOA are readily absorbed in the gastrointestinal tract, excreted in urine and faeces, and do not undergo metabolism. Estimated human half-lives for PFOS and PFOA are about 5 years and 2-4 years, respectively. The derivation of a health-based guidance value was based on human epidemiological studies. For PFOS, the increase in serum total cholesterol in adults, and the decrease in antibody response at vaccination in children were identified as the critical effects. For PFOA, the increase in serum total cholesterol was the critical effect. Also reduced birth weight (for both compounds) and increased prevalence of high serum levels of the liver enzyme alanine aminotransferase (ALT) (for PFOA) were considered. After benchmark modelling of serum levels of PFOS and PFOA, and estimating the corresponding daily intakes, the CONTAM Panel established a tolerable weekly intake (TWI) of 13 ng/kg body weight (bw) per week for PFOS and 6 ng/kg bw per week for PFOA. For both compounds, exposure of a considerable proportion of the population exceeds the proposed TWIs.

Developmental Origins of Disease: Emerging Prenatal Risk Factors and Future Disease Risk

Purpose of review

Many of the diseases and dysfunctions described in the paradigm of the developmental origins of health and disease have been studied in relation to prenatal nutrition or environmental toxicant exposures. Here, we selectively review the current research on four exposures-two nutritional and two environmental-that have recently emerged as prenatal risk factors for long-term health outcomes.

Recent findings

Recent studies have provided strong evidence that prenatal exposure to (1) excessive intake of sugar-sweetened beverages, (2) unhealthy dietary patterns, (3) perfluoroalkyl substances, and (4) fine particulate matter, may increase risk of adverse health outcomes, such as obesity, cardiometabolic dysfunction, and allergy/asthma.

Summary

Emerging prenatal nutritional factors and environmental toxicants influence offspring long-term health. More work is needed to identify the role of paternal exposures and maternal exposures during the preconception period and to further elucidate causality through intervention studies. The ubiquity of these emerging nutritional and environmental exposures makes this area of inquiry of considerable public health importance.

An epigenome-wide study of cord blood DNA methylations in relation to prenatal perfluoroalkyl substance exposure: The Hokkaido study

BACKGROUND

Prenatal exposure to perfluoroalkyl substances (PFASs) influences fetal development and later in life.

OBJECTIVE

To investigate cord blood DNA methylation changes associated with prenatal exposure to PFASs.

METHODS

We assessed DNA methylation in cord blood samples from 190 mother-child pairs from the Sapporo cohort of the Hokkaido Study (discovery cohort) and from 37 mother-child pairs from the Taiwan Maternal and Infant Cohort Study (replication cohort) using the Illumina HumanMethylation 450 BeadChip. We examined the associations between methylation and PFAS levels in maternal serum using robust linear regression models and identified differentially methylated positions (DMPs) and regions (DMRs).

RESULTS

We found four DMPs with a false discovery rate below 0.05 in the discovery cohort. Among the top 20 DMPs ranked by the lowest P-values for perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) exposure, four DMPs showed the same direction of effect and P-value < 0.05 in the replication assay: cg16242615 mapped to ZBTB7A, cg21876869 located in the intergenic region (IGR) of USP2-AS1, cg00173435 mapped to TCP11L2, and cg18901140 located in IGR of NTN1. For DMRs, we found a region associated with PFOA exposure with family-wise error rate < 0.1 located in ZFP57, showing the same direction of effect in the replication cohort. Among the top five DMRs ranked by the lowest P-values that were associated with exposure to PFOS and PFOA, in addition to ZFP57, DMRs in the CYP2E1, SMAD3, SLC17A9, GFPT2, DUSP22, and TCERG1L genes showed the same direction of effect in the replication cohort.

CONCLUSION

We suggest that prenatal exposure to PFASs may affect DNA methylation status at birth. Longitudinal studies are needed to examine whether methylation changes observed are associated with differential health outcomes.

[Importance of Two Birth Cohorts (n=20,926 and n=514): 15 Years' Experience of the Hokkaido Study on Environment and Children's Health: Malformation, Development and Allergy]

Since "Our Stolen Future" by Theo Colborn was published in 1996, global interest on the impact of chemical substances, such as the endocrine-disrupting action of chemicals, has increased. In Japan, "The Hokkaido Study on Environment and Children's Health: Malformation, Development and Allergy" was launched in 2001. It was a model of Japan Environment and Children's Study of the Ministry of the Environment. In a large-scale, Hokkaido cohort, we obtained the consent of 20,926 mothers at the organogenesis stage with the cooperation of 37 obstetrics clinics in Hokkaido. We tracked the effects of endocrine disruptors on developmental disorders. In a small-scale Sapporo cohort, we observed in detail the neuropsychiatric development of children with the consent of 514 mothers in their late pregnancy. We examined how prenatal exposure to low concentrations of environmental chemicals affect the development of organs and the postnatal development of children. Maternal exposure to POPs, such as PCB/dioxins and perfluorinated alkyl substances, has affected not only children's birth size, thyroid functions, and sex hormone levels, but also postnatal neurodevelopment, infection, and allergy among others. The associations of short-half-life substances, such as DEHP and BPA, with obesity, ASD, and ADHD have been investigated. Gene-environment interactions have been found for smoking, caffeine, folic acid, and PCB/dioxin. In 2015, our center was officially designated as the WHO Collaborating Centre for Environmental Health and Prevention of Chemical Hazards, and we continue to the contribute to the global perspectives of child health.

Determinants and Temporal Trends of Perfluoroalkyl Substances in Pregnant Women: The Hokkaido Study on Environment and Children's Health

Perfluoroalkyl substances (PFAS) are persistent bio-accumulative chemicals that impact the health of pregnant women and their children. PFAS derive from environmental and consumer products, which depend on human lifestyle, socioeconomic characteristics, and time variation. Here, we aimed to explore the temporal trends of PFAS in pregnant women and the characteristics related to maternal PFAS concentration. Our study is part of the Hokkaido Study on Environment and Children's Health, the Hokkaido large-scale cohort that recruited pregnant women between 2003 and 2011. Blood samples were acquired from pregnant women during the third trimester to measure PFAS and cotinine concentrations. Maternal basic information was collected with a baseline structured questionnaire. Eleven PFAS were measured from 2123 samples with ultra-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry. Eight PFAS were above 80% detection rate and were included in the final analysis. We used multivariable linear regression to analyze the association of pregnant women characteristics with the levels of eight PFAS. The temporal trend of PFAS was observed in two periods (August 2003 to January 2006 and February 2006 to July 2012). The concentration of perfluorooctane sulfonate (PFOS) significantly decreased from August 2003 to January 2006 and from February 2006 to July 2012. The concentrations of perfluorododecanoic acid (PFDoDA), perfluoroundecanoic acid (PFUnDA), and perfluorotridecanoic acid (PFTrDA) increased significantly between August 2003 and January 2006, whereas they decreased significantly between February 2006 and July 2012. Women with pre-pregnancy body mass index (BMI) >25 kg/m² had lower PFUnDA, PFDoDA, and PFTrDA levels than did those with normal BMI (18.5⁻24.9 kg/m²). Pregnant women, who were active smokers (cotinine > 11.49 ng/mL), had higher PFOS than the non-smokers (cotinine < 0.22 ng/mL). Lower levels of PFHxS, PFOS, PFOA, PFNA, and PFDA were observed in women, who had given birth to more than one child. There were also significant positive associations between PFAS levels and annual income or maternal education. PFAS levels varied in women with higher pre-pregnancy BMI, active smoking status, higher education level and annual income. The causes of the individual PFAS differences should be explored in an independent study.

Birth cohorts in Asia: The importance, advantages, and disadvantages of different-sized cohorts

Asia contains half of the world's children, and the countries of Asia are the most rapidly industrializing nations on the globe. Environmental threats to the health of children in Asia are myriad. Several birth cohorts were started in Asia in early 2000, and currently more than 30 cohorts in 13 countries have been established for study. Cohorts can contain from approximately 100-200 to 20,000-30,000 participants. Furthermore, national cohorts targeting over 100,000 participants have been launched in Japan and Korea. The aim of this manuscript is to discuss the importance of Asian cohorts, and the advantages and disadvantages of different-sized cohorts. As for case, one small-sized (n=514) cohort indicate that even relatively low level exposure to dioxin in utero could alter birth size, neurodevelopment, and immune and hormonal functions. Several Asian cohorts focus prenatal exposure to perfluoroalkyo substances and reported associations with birth size, thyroid hormone levels, allergies and neurodevelopment. Inconsistent findings may possibly be explained by the differences in exposure levels and target chemicals, and by possible statistical errors. In a smaller cohort, novel hypotheses or preliminary examinations are more easily verifiable. In larger cohorts, the etiology of rare diseases, such as birth defects, can be analyzed; however, they require a large cost and significant human resources. Therefore, conducting studies in only one large cohort may not always be the best strategy. International collaborations, such as the Birth Cohort Consortium of Asia, would cover the inherent limitation of sample size in addition to heterogeneity of exposure, ethnicity, and socioeconomic conditions.

Prenatal exposure to perfluoroalkyl and polyfluoroalkyl substances and childhood atopic dermatitis: a prospective birth cohort study

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been reported to suppress immune function. However, previous studies on prenatal exposure to PFASs and allergic disorders in offspring provided inconsistent results. We aimed to examine the association between prenatal exposure to PFASs and childhood atopic dermatitis (AD) in offspring up to 24 months of age.

METHODS

A prospective birth cohort study involving 1056 pregnant women was conducted in two hospitals in Shanghai from 2012 to 2015. Prenatal information was collected by an interview with the women and from medical records. Fetal umbilical cord blood was collected at birth. Cord blood plasma PFASs were measured. Children were followed at 6, 12 and 24 months and information on the development of AD was recorded. AD was diagnosed by 2 dermatologists independently based on the questionnaires. Multiple logistic regression was used to compute odds ratio (OR) and corresponding 95% confidence interval (CI) for the association between AD and each PFASs, adjusting for potential confounders.

RESULTS

A total of 687 children completed a 2-year follow-up visit and had PFASs measurement. AD was diagnosed in 173 (25.2%) children during the first 24 months. In female children, a log-unit increase in perfluorooctanoic acid (PFOA) was associated with a 2.1-fold increase in AD risk (AOR 2.07, 95% CI 1.13-3.80) after adjusting for potential confounders. The corresponding risk was 2.22 (1.07-4.58) for perfluorononanoic acid (PFNA). The highest PFOA quartile was significantly associated with AD (2.52, 1.12-5.68) compared with the lowest quartile. The highest quartile of PFNA, perfluorodecanoic acid (PFDA) and perfluorohexane sulfonic acid (PFHxS) were associated with AD with AOR (95% CI) being 2.14 (0.97-4.74), 2.14 (1.00-4.57), and 2.30 (1.03-5.15), respectively. Additionally, the second quartile of perfluorododecanoic acid (PFDoA) was associated with a 3.2-fold increase in AD risk (3.24, 1.44-7.27). However, no significant associations were found in male children.

CONCLUSIONS

Prenatal exposure to PFOA, PFDA, PFDoA and PFHxS significantly increased the risk of childhood AD in female children during the first 24 months of life. In addition, the associations between AD with prenatal exposure to PFNA were close to statistical significance.

Prenatal exposure to perfluoralkyl substances (PFASs) associated with respiratory tract infections but not allergy- and asthma-related health outcomes in childhood

BACKGROUND

Prenatal exposure to perfluoralkyl substances (PFASs) has been reported to be associated with immunosuppression in early childhood, but with contradictory findings related to atopic and lung diseases.

AIM

We aimed to determine if prenatal exposure to PFASs is associated with asthma or other allergic diseases or respiratory tract infections in childhood.

METHODS

Nineteen PFASs were measured in cord blood available from 641 infants in the Environment and Childhood Asthma (ECA) prospective birth cohort study. The six most abundant PFASs were perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonamide (PFOSA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and perfluoroundecanoic acid (PFUnDA). Health outcomes were assessed at two and ten years of age, and included reported obstructive airways disease (wheeze by 10 years; asthma by 2 and 10 years; reduced lung function at birth; allergic rhinitis by 10 years), atopic dermatitis (AD) by 2 and 10 years, allergic sensitization by 10 years, and episodes of common respiratory tract infections (common cold by 2 years, lower respiratory tract infections (LRTI) by 10 years). The associations between exposure and health outcomes were examined using logistic and Poisson regression.

RESULTS

The number of reported airways infections were significantly associated with cord blood concentrations of PFAS; common colds by two years with PFUnDA (β = 0.11 (0.08-0.14)) and LRTIs from 0 to 10 years of age with PFOS (β = 0.50 (0.42-0.57)), PFOA (β = 0.28 (0.22-0.35)), PFOSA (β = 0.10 (0.06-0.14)), PFNA (β = 0.09 (0.03-0.14)) and PFUnDA (β = 0.18 (0.13-0.23)) concentrations. Neither reduced lung function at birth, asthma, allergic rhinitis, AD nor allergic sensitization were significantly associated with any of the PFASs.

CONCLUSION

Although prenatal exposure to PFASs was not associated with atopic or lung manifestations by 10 years of age, several PFASs were associated with an increased number of respiratory tract infections in the first 10 years of life, suggesting immunosuppressive effects of PFASs.

Children's environmental health based on birth cohort studies of Asia

Numerous studies have explored the associations between environmental pollutants and pediatric health. Recent studies have investigated the issue in Asia, but no systematic review has been published to date. This study aims to elucidate the issue by summarizing relevant epidemiologic evidence for cohorts in Asia, using information from the Birth Cohort Consortium of Asia (BiCCA). Environmental pollutants include mercury, environmental tobacco smoke (ETS), polychlorinated biphenyls (PCB), perfluoroalkyl substances (PFAS) and phthalates. This study sought to classify the effects of such compounds on fetal growth and pregnancy outcomes, neurodevelopment and behavioral problems, allergic disease and immune function and the endocrine system and puberty. These evidences showed ETS has been associated with infant birth weight, children's neurodevelopment and allergy disease; mercury and PCB have been shown to affect children's neurodevelopment; phthalate has effects on endocrine function; PFAS alters children's neurodevelopment, the endocrine system, and the allergic response. However, more consistent and coordinated research is necessary to understand the whole picture of single environmental and/or co-exposure and children's health. Therefore, harmonization and international collaboration are also needed in Asia.

Concentration of perfluorinated compounds and cotinine in human foetal organs, placenta, and maternal plasma

BACKGROUND

Perfluoroalkyl substances (PFASs) are bio-accumulative pollutants, and prenatal exposure to PFASs is believed to impact human foetal development and may have long-term adverse health effects later in life. Additionally, maternal cigarette smoking may be associated with PFAS levels. Foetal exposure has previously been estimated from umbilical cord plasma, but the actual concentration in foetal organs has never been measured.

OBJECTIVES

The concentrations of 5 PFASs and cotinine - the primary metabolite of nicotine - were measured in human foetuses, placentas, and maternal plasma to evaluate to what extent these compounds were transferred from mother to foetus and to determine if the PFAS concentrations were associated with maternal cigarette smoking.

METHODS

Thirty-nine Danish women who underwent legal termination of pregnancy before gestational week 12 were included; 24 maternal blood samples were obtained together with 34 placental samples and 108 foetal organs. PFASs and cotinine were assayed by liquid chromatography/triple quadrupole mass spectrometry.

RESULTS

In foetal organs, the average concentrations of perfluorooctanesulphonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUnDa), and perfluorodecanoic acid (PFDA) were 0.6ng/g, 0.2ng/g, 0.1ng/g, 0.1ng/g, and 0.1ng/g, respectively. A significant positive correlation was found between the exposure duration, defined as foetal age, and foetal to maternal ratio for all five PFASs and cotinine. Smokers presented 99ng/g cotinine in plasma, 108ng/g in placenta, and 61ng/g in foetal organs. No correlation between the maternal cotinine concentrations and PFAS concentrations was found.

CONCLUSIONS

PFASs were transferred from mother to foetus, however, with different efficiencies. The concentrations of PFOS, PFOA, PFNA, PFUnDA, and PFDA in foetal organs were much lower than the maternal concentrations. Furthermore, a significant correlation between the exposure duration and all of the evaluated PFASs was found. The health-compromising concentrations of these substances during foetal development are unknown.

Prenatal exposure to perfluoroalkyl acids and prevalence of infectious diseases up to 4years of age

Perfluoroalkyl acids (PFAAs) are synthetic chemicals with ability to repel oils and water, and have been widely used in many industrial and household applications such as adhesives and water- and stain-repellent surfaces to nonstick coatings. Animal studies have shown that PFAAs have immunotoxic effects. However, few epidemiological studies have investigated the effects of PFAAs on infectious diseases occurrence. We examined the relationship between prenatal exposure to PFAAs and prevalence of infectious diseases up to 4years of life. A total of 1558 mother-child pairs, who were enrolled in the Hokkaido Study on Environment and Children's Health, were included in this data analysis. Eleven PFAAs were measured in maternal plasma taken at 28-32weeks of gestation using ultra-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry. Participant characteristics were obtained from medical birth records and self-administered questionnaires during pregnancy and after delivery. Physicians' diagnosis of common infectious diseases including otitis media, pneumonia, respiratory syncytial virus infection, and varicella up to 4years were extracted from the mother-reported questionnaires. The number of children who developed infectious diseases up to 4years of age was as follows: otitis media, 649 (41.4%); pneumonia, 287 (18.4%); respiratory syncytial virus infection, 197 (12.6%); varicella 589 (37.8%). A total of 1046 (67.1%) children had at least one of the diseases defined as total infectious diseases. After adjusting for appropriate confounders, PFOS levels in the highest quartile were associated with increased odds ratios (ORs) of total infectious diseases (Q4 vs. Q1 OR: 1.61; 95% CI: 1.18, 2.21; p for trend=0.008) in all children. In addition, perfluorohexane sulfonate (PFHxS) was associated with a higher risk of total infectious diseases only among girls (Q4 vs. Q1 OR: 1.55, 95% CI: 0.976, 2.45; p for trend=0.045). We found no association between infectious diseases and other examined PFAAs. Our findings suggest that prenatal exposure to PFOS and PFHxS may associated with infectious diseases occurrence in early life. Therefore, prenatal exposure to PFAAs may be immunotoxic for the immune system in offspring.

Exposure to Perfluorinated Alkyl Substances and Health Outcomes in Children: A Systematic Review of the Epidemiologic Literature

Perfluoroalkyl substances (PFAS), chemicals used to make products stain and stick resistant, have been linked to health effects in adults and adverse birth outcomes. A growing body of literature also addresses health effects in children exposed to PFAS. This review summarizes the epidemiologic evidence for relationships between prenatal and/or childhood exposure to PFAS and health outcomes in children as well as to provide a risk of bias analysis of the literature. A systematic review was performed by searching PubMed for studies on PFAS and child health outcomes. We identified 64 studies for inclusion and performed risk of bias analysis on those studies. We determined that risk of bias across studies was low to moderate. Six categories of health outcomes emerged. These were: immunity/infection/asthma, cardio-metabolic, neurodevelopmental/attention, thyroid, renal, and puberty onset. While there are a limited number of studies for any one particular health outcome, there is evidence for positive associations between PFAS and dyslipidemia, immunity (including vaccine response and asthma), renal function, and age at menarche. One finding of note is that while PFASs are mixtures of multiple compounds few studies examine them as such, therefore the role of these compounds as complex mixtures remains largely unknown.

The Hokkaido Birth Cohort Study on Environment and Children's Health: cohort profile-updated 2017

The Hokkaido Study on Environment and Children's Health is an ongoing study consisting of two birth cohorts of different population sizes: the Sapporo cohort and the Hokkaido cohort. Our primary study goals are (1) to examine the effects of low-level environmental chemical exposures on birth outcomes, including birth defects and growth retardation; (2) to follow the development of allergies, infectious diseases, and neurobehavioral developmental disorders and perform a longitudinal observation of child development; (3) to identify high-risk groups based on genetic susceptibility to environmental chemicals; and (4) to identify the additive effects of various chemicals, including tobacco smoking. The purpose of this report is to update the progress of the Hokkaido Study, to summarize the recent results, and to suggest future directions. In particular, this report provides the basic characteristics of the cohort populations, discusses the population remaining in the cohorts and those who were lost to follow-up at birth, and introduces the newly added follow-up studies and case-cohort study design. In the Sapporo cohort of 514 enrolled pregnant women, various specimens, including maternal and cord blood, maternal hair, and breast milk, were collected for the assessment of exposures to dioxins, polychlorinated biphenyls, organochlorine pesticides, perfluoroalkyl substances, phthalates, bisphenol A, and methylmercury. As follow-ups, face-to-face neurobehavioral developmental tests were conducted at several different ages. In the Hokkaido cohort of 20,926 enrolled pregnant women, the prevalence of complicated pregnancies and birth outcomes, such as miscarriage, stillbirth, low birth weight, preterm birth, and small for gestational age were examined. The levels of exposure to environmental chemicals were relatively low in these study populations compared to those reported previously. We also studied environmental chemical exposure in association with health outcomes, including birth size, neonatal hormone levels, neurobehavioral development, asthma, allergies, and infectious diseases. In addition, genetic and epigenetic analyses were conducted. The results of this study demonstrate the effects of environmental chemical exposures on genetically susceptible populations and on DNA methylation. Further study and continuous follow-up are necessary to elucidate the combined effects of chemical exposure on health outcomes.

Association between perfluoroalkyl substance exposure and asthma and allergic disease in children as modified by MMR vaccination

Perfluoroalkyl substances (PFASs) are highly persistent chemicals that might be associated with asthma and allergy, but the associations remain unclear. Therefore, this study examined whether pre- and postnatal PFAS exposure was associated with childhood asthma and allergy. Measles, mumps, and rubella (MMR) vaccination in early life may have a protective effect against asthma and allergy, and MMR vaccination is therefore taken into account when evaluating these associations. In a cohort of Faroese children whose mothers were recruited during pregnancy, serum concentrations of five PFASs - Perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) - were measured at three timepoints (maternal serum in pregnancy week 34-36 and child serum at ages 5 and 13 years) and their association with immunoglobulin E (IgE) (cord blood and at age 7 years) and asthma/allergic diseases (questionnaires at ages 5 and 13 years and skin prick test at age 13 years) was determined. A total of 559 children were included in the analyses. Interactions with MMR vaccination were evaluated. Among 22 MMR-unvaccinated children, higher levels of the five PFASs at age 5 years were associated with increased odds of asthma at ages 5 and 13. The associations were reversed among MMR-vaccinated children. Prenatal PFAS exposure was not associated with childhood asthma or allergic diseases regardless of MMR vaccination status. In conclusion, PFAS exposure at age 5 was associated with increased risk of asthma among a small subgroup of MMR-unvaccinated children but not among MMR-vaccinated children. While PFAS exposure may impact immune system functions, this study suggests that MMR vaccination might be a potential effect-modifier.

Prenatal exposure to persistent organic pollutants and offspring allergic sensitization and lung function at 20 years of age

BACKGROUND

Prenatal exposures to persistent organic pollutants (POPs) have been associated with asthma medication use and self-reported symptoms, but associations with lung function and allergic sensitization have been minimally explored. The aim of the study was to examine the associations between prenatal exposures to POPs and allergic sensitization and lung function in 20-year-old offspring.

METHODS

In a Danish cohort of 965 pregnant women established in 1988-1989, six polychlorinated biphenyl (PCB) congeners, hexachlorobenzene (HCB), and dichlorodiphenyldichloroethylene (p,p'-DDE) were quantified in archived maternal serum drawn in gestational week 30 (n = 872). Among those with available maternal exposure information, at age 20, 421 offspring attended attended a clinical examination including measurements of allergic sensitization (serum-specific IgE ≥ 0.35 kUA /L) (n = 418) and lung function [forced expiratory volume in one second (FEV1 ) and forced vital capacity (FVC)] (n = 414).

RESULTS

There were no associations between maternal concentrations of POPs and offspring allergic sensitization at 20 years of age. Maternal concentrations of POPs were, however, positively associated with offspring airway obstruction (FEV1 /FVC < 75%). Compared to offspring in the first tertile of exposure, offspring in the third tertile of dioxin-like PCB exposure had an OR of 2.96 (95% CI: 1.14-7.70). Similar associations for non-dioxin-like PCBs, HCB, and p,p'-DDE were 2.68 (1.06-6.81), 2.63 (1.07, 6.46), and 2.87 (1.09, 7.57), respectively. No associations were observed with reduced lung function (FEV1 % of predicted value < 90%).

CONCLUSION AND CLINICAL RELEVANCE

Our data indicate that prenatal exposure to POPs appears to be associated with airway obstruction but not allergic sensitization at 20 years of age. The findings support that chronic obstructive lung diseases may have at least part of their origins in early life.

Effects of prenatal exposure to perfluoroalkyl acids on prevalence ofallergic diseases among 4-year-old children

Perfluoroalkyl acids (PFAAs) are ubiquitous chemicals extremely resistant and widespread throughout the environment, frequently being detected in human blood samples. Animal studies have revealed that exposure to PFAAs results in immunotoxicity. However, the association between PFAAs, especially long-chain PFAAs, and allergies in humans is not well established. We examined whether prenatal exposure to PFAAs is associated with allergic diseases among 4-year-old children in a large-scale prospective birth cohort in Hokkaido, Japan. In total, 1558 mother-child pairs were included in this study and prenatal levels of eleven PFAAs were measured in maternal plasma samples obtained between 28 and 32weeks of pregnancy by using ultra-performance liquid chromatography-tandem mass spectrometry. Participant demographic and characteristic information were obtained from self-administered pre- and postnatal questionnaires and medical birth records. Infant allergies were assessed using the Japanese version of the International Study of Asthma and Allergies in Childhood (ISAAC) Phase Three questionnaire, which was administered 4years post-delivery. Symptoms included eczema, wheezing and rhinoconjunctivitis with a prevalence of 19.0%, 18.7%, and 5.4%, respectively. Associations of PFAA quartiles with allergic outcomes were examined using logistic models. Adjusted odds ratios (ORs) in the 4th quartile vs. 1st quartile (Q4 vs. Q1) for total allergic diseases (including at least one allergic outcome) significantly decreased for perfluorododecanoic acid (PFDoDa) (Q4 vs. Q1 OR: 0.621; 95% confidence interval (CI): 0.454, 0.847) and perfluorotridecanoic acid (PFTrDA) (Q4 vs. Q1 OR: 0.712; 95% CI: 0.524, 0.966) in all children. We obtained similar results when examining the association between PFAAs and eczema. The adjusted OR (Q4 vs. Q1) for wheezing in relation to higher maternal PFHxS levels was 0.728 (95% CI: 0.497, 1.06) in all children. In conclusion, prenatal exposure to long-chain PFAAs, such as PFDoDa and PFTrDA may have an immunosuppressive effect on allergic diseases in 4-year-old children.

Associations of serum perfluoroalkyl acid levels with T-helper cell-specific cytokines in children: By gender and asthma status

Perfluoroalkyl acids (PFAAs) are a group of common chemicals that ubiquitously exist in wildlife and humans. Experimental data suggest that they may alter T-lymphocyte functioning in situ by preferentially enhancing the development of T-helper 2 (TH2)- and inhibiting TH1-lymphocyte development and might increase allergic inflammation, but few human studies have been conducted. To evaluate the association between serum PFAAs concentrations and T-lymphocyte-related immunological markers of asthma in children, and further to assess whether gender modified this association, 231 asthmatic children and 225 non-asthmatic control children from Northern Taiwan were recruited into the Genetic and Biomarker study for Childhood Asthma. Serum concentrations of ten PFAAs and levels of TH1 [interferon (IFN)-γ, interleukin (IL)-2] and TH2 (IL-4 and IL-5) cytokines were measured. The results showed that asthmatics had significantly higher serum PFAAs concentrations compared with the healthy controls. When stratified by gender, a greater number of significant associations between PFAAs and asthma outcomes were found in males than in females. Among males, adjusted odds ratios for asthma among those with the highest versus lowest quartile of PFAAs exposure ranged from 2.59 (95% CI: 1.14, 5.87) for the perfluorobutanesulfonate (PFBS) to 4.38 (95% CI: 2.02, 9.50) for perfluorooctanesulfonate (PFOS); and serum PFAAs were associated positively with TH2 cytokines and inversely with TH1 cytokines among male asthmatics. Among females, no significant associations between PFAAs and TH2 cytokines could be detected. In conclusion, increased serum PFAAs levels may promote TH cell dysregulation and alter the availability of key TH1 and TH2 cytokines, ultimately contributing to the development of asthma that may differentially impact males to a greater degree than females. These results have potential relevance in asthma prevention.

Environmental pollutants and child health-A review of recent concerns

In recent years, many new studies have evaluated associations between environmental pollutants and child health. This review aims to provide a broad summary of this literature, comparing the state of epidemiological evidence for the effects of a wide range of environmental contaminants (air pollutants, heavy metals, organochlorine compounds, perfluoroalkyl substances, polybrominated diphenyl ethers, pesticides, phthalates and bisphenol A) on child health outcomes. The review addresses effects on foetal growth and prematurity, neurodevelopment, respiratory and immune health, and childhood growth and obesity. Findings of recent prospective studies and meta-analyses have corroborated previous good evidence, often at lower exposure levels, for effects on foetal growth of air pollution and polychlorinated biphenyls (PCBs), for neurotoxic effects of lead, methylmercury, PCBs and organophosphate pesticides, and for respiratory health effects of air pollution. Moderate evidence has emerged for a potential role of environmental pollutants in attention deficit hyperactivity disorder and autism (lead, PCBs, air pollution), respiratory and immune health (dichlorodiphenyldichloroethylene - DDE - and PCBs), and obesity (DDE). In addition, there is now moderate evidence that certain chemicals of relatively recent concern may be associated with adverse child health outcomes, specifically perfluorooctanoate and foetal growth, and polybrominated diphenyl ethers and neurodevelopment. For other chemicals of recent concern, such as phthalates and bisphenol A, the literature is characterised by large inconsistencies preventing strong conclusions. In conclusion, since most of the recent literature evaluates common exposures in the general population, and not particularly high exposure situations, this accumulating body of evidence suggests that the unborn and young child require more protection than is currently provided. Large, coordinated research efforts are needed to improve understanding of long-term effects of complex chemical mixtures.

Perfluoroalkyl substances and food allergies in adolescents

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of organic compounds that are persistent in the environment due to their stable carbon-fluorine backbone, which is not susceptible to degradation. Research suggests these chemicals may exert an immunotoxic effect. The aim of this study is to investigate the associations between four PFASs - perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS) - with food sensitization and food allergies in adolescent participants (ages 12-19years) in the National Health and Nutrition Examination Survey (NHANES) 2005-2006 and 2007-2010, respectively. We performed multivariate logistic regression to analyze the association between individual PFASs with food sensitization (defined as having at least 1 food-specific IgE level≥0.35kU/L) in NHANES 2005-2006 and food allergies (self-reported) in NHANES 2007-2010. Serum PFOA, PFOS, and PFHxS were statistically significantly associated with higher odds to have self-reported food allergies in NHANES 2007-2010. When using IgE levels as a marker of food sensitization, we found that serum PFNA was inversely associated with food sensitization (NHANES 2005-2006). In conclusion, we found that serum levels of PFASs were associated with higher odds to have self-reported food allergies. Conversely, adolescents with higher serum PFNA were less likely to be sensitized to food allergens. These results, along with previous studies, warrant further investigation, such as well-designed longitudinal studies.

A critical review of perfluorooctanoate and perfluorooctanesulfonate exposure and immunological health conditions in humans

Whether perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS), two widely used and biopersistent synthetic chemicals, are immunotoxic in humans is unclear. Accordingly, this article systematically and critically reviews the epidemiologic evidence on the association between exposure to PFOA and PFOS and various immune-related health conditions in humans. Twenty-four epidemiologic studies have reported associations of PFOA and/or PFOS with immune-related health conditions, including ten studies of immune biomarker levels or gene expression patterns, ten studies of atopic or allergic disorders, five studies of infectious diseases, four studies of vaccine responses, and five studies of chronic inflammatory or autoimmune conditions (with several studies evaluating multiple endpoints). Asthma, the most commonly studied condition, was evaluated in seven studies. With few, often methodologically limited studies of any particular health condition, generally inconsistent results, and an inability to exclude confounding, bias, or chance as an explanation for observed associations, the available epidemiologic evidence is insufficient to reach a conclusion about a causal relationship between exposure to PFOA and PFOS and any immune-related health condition in humans. When interpreting such studies, an immunodeficiency should not be presumed to exist when there is no evidence of a clinical abnormality. Large, prospective studies with repeated exposure assessment in independent populations are needed to confirm some suggestive associations with certain endpoints.

Prenatal exposure to environmental chemical contaminants and asthma and eczema in school-age children

BACKGROUND

Emerging evidence suggests that prenatal or early-life exposures to environmental contaminants may contribute to an increased risk of asthma and allergies in children. We aimed to the explore associations of prenatal exposures to a large set of environmental chemical contaminants with asthma and eczema in school-age children.

METHODS

We studied 1024 mother-child pairs from Greenland and Ukraine from the INUENDO birth cohort. Data were collected by means of an interview-based questionnaire when the children were 5-9 years of age. Questions from the ISAAC study were used to define asthma, eczema, and wheeze. We applied principal components analysis (PCA) to sixteen contaminants in maternal serum sampled during pregnancy, including perfluoroalkyl substances (PFASs), metabolites of diethylhexyl (DEHP) and diisononyl (DiNP) phthalates, PCB-153, and p,p'-DDE. Scores of five principal components (PCs) explaining 70% of the variance were included in multiple logistic regression models.

RESULTS

In a meta-analysis that included both populations, the PC2 score, reflecting exposure to DiNP, was negatively associated with current eczema (OR 0.71, 95% CI 0.52-0.96). Other associations were not consistent between the two populations. In Ukrainian children, the PC3 score (DEHP) was positively associated with current wheeze (adjusted OR 1.56, 95% CI 1.03-2.37), whereas the PC5 score, dominated by perfluorooctanoic acid (PFOA), was inversely associated with current wheeze (OR 0.64, 0.41-0.99). In Greenlandic children, a negative association of PC4 (organochlorines) with ever eczema (OR 0.78, 0.61-0.99) was found.

CONCLUSIONS

We found limited evidence to support a link between prenatal exposure to environmental chemical contaminants and childhood asthma and eczema.