Prenatal and early postnatal exposure to perfluoroalkyl substances and bone mineral content and density in the Odense child cohort

INTRODUCTION

Exposure to perfluoroalkyl substances (PFAS) has been associated with lower bone mineral density (BMD) in animal and human studies, but prospective data from children are limited.

OBJECTIVES

To determine associations between prenatal and early postnatal PFAS exposure and BMD at age 7 years.

METHODS

In the Odense Child Cohort, Denmark, pregnant women were recruited in 2010-2012, and their children were invited for subsequent health examinations. At 12 weeks of gestation the pregnant women delivered a serum sample, and at age 18 months serum was obtained from the child to measure perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) by LC-MS/MS. At age 7 years DXA scans were performed to measure bone mineral content (BMC) and BMD Z-score. PFAS in pregnancy (n = 924) and/or at age 18 months (n = 511) were regressed against DXA measurements, adjusted for maternal education, child height Z-score, sex (for BMC) and for postnatal exposure, additionally duration of total breastfeeding. We additionally performed structural equation models determining combined effects of pre-and postnatal PFAS exposures.

RESULTS

Higher prenatal and early postnatal serum concentrations of all measured PFAS were associated with lower BMC and BMD Z-scores at age 7 years, all estimates were negative although not all significant. For each doubling of prenatal or 18-month exposure to PFDA, BMD Z-scores were lowered by -0.07 (95 % CI -0.10; -0.03) and -0.14 (-0.25; -0.03), respectively after adjustment. Pre- and postnatal PFAS were correlated, but structural equation models suggested that associations with BMD were stronger for 18-month than prenatal PFAS exposure.

DISCUSSION

Bone density is established in childhood, and a reduction in BMD during early childhood may have long-term implication for peak bone mass and lifelong bone health. Future studies of the impact of PFAS exposure on fracture incidence will help elucidate the clinical relevance.

Severity of COVID-19 at elevated exposure to perfluorinated alkylates

Background

The course of coronavirus disease 2019 (COVID-19) seems to be aggravated by air pollution, and some industrial chemicals, such as the perfluorinated alkylate substances (PFASs), are immunotoxic and may contribute as well.

Methods

From Danish biobanks, we obtained plasma samples from 323 subjects aged 30-70 years with known SARS-CoV-2 infection. The PFAS concentrations measured at the background exposures included five PFASs known to be immunotoxic. Register data was obtained to classify disease status, other health information, and demographic variables. We used ordinal and ordered logistic regression analyses to determine associations between PFAS concentrations and disease outcome.

Results

Plasma-PFAS concentrations were higher in males, in subjects with Western European background, and tended to increase with age, but were not associated with the presence of chronic disease. Of the study population, 108 (33%) had not been hospitalized, and of those hospitalized, 53 (16%) had been in intensive care or were deceased. Among the five PFASs considered, perfluorobutanoic acid (PFBA) showed an odds ratio (OR) of 2.19 (95% confidence interval, CI, 1.39-3.46) for increasing severities of the disease, although the OR decreased to 1.77 (95% CI, 1.09, 2.87) after adjustment for age, sex, sampling site and interval between blood sampling and diagnosis.

Conclusions

Measures of individual exposures to immunotoxic PFASs included PFBA that accumulates in the lungs. Elevated plasma-PFBA concentrations were associated with an increased risk of more severe course of CIVID-19. Given the low background exposure levels in this study, the role of PFAS exposure in COVID-19 needs to be ascertained in populations with elevated exposures.

Epigenetics as a mechanism linking developmental exposures to long-term toxicity

A variety of experimental and epidemiological studies lend support to the Developmental Origin of Health and Disease (DOHaD) concept. Yet, the actual mechanisms accounting for mid- and long-term effects of early-life exposures remain unclear. Epigenetic alterations such as changes in DNA methylation, histone modifications and the expression of certain RNAs have been suggested as possible mediators of long-term health effects of environmental stressors. This report captures discussions and conclusions debated during the last Prenatal Programming and Toxicity meeting held in Japan. Its first aim is to propose a number of criteria that are critical to support the primary contribution of epigenetics in DOHaD and intergenerational transmission of environmental stressors effects. The main criteria are the full characterization of the stressors, the actual window of exposure, the target tissue and function, the specificity of the epigenetic changes and the biological plausibility of the linkage between those changes and health outcomes. The second aim is to discuss long-term effects of a number of stressors such as smoking, air pollution and endocrine disruptors in order to identify the arguments supporting the involvement of an epigenetic mechanism. Based on the developed criteria, missing evidence and suggestions for future research will be identified. The third aim is to critically analyze the evidence supporting the involvement of epigenetic mechanisms in intergenerational and transgenerational effects of environmental exposure and to particularly discuss the role of placenta and sperm. While the article is not a systematic review and is not meant to be exhaustive, it critically assesses the contribution of epigenetics in the long-term effects of environmental exposures as well as provides insight for future research.

Short Communications

Seven patients with one or two lead shots retained in the appendix were identified by radiography. For each case, two sex- and age-matched control patients without lead shot in the appendix were found. None of the 7 patients with lead shot in the appendix had blood lead levels (median 0.55 μmol/l) approaching the toxic levels, but they averaged almost twice the levels of the controls (median 0.29 μmol/l). Thus, lead shots may add to individual lead exposures, and blood lead analysis should be performed, at least when more than a few lead shots are present.

Children's white blood cell counts in relation to developmental exposures to methylmercury and persistent organic pollutants

BACKGROUND

To explore possible markers of developmental immunotoxicity, we prospectively examined 56 children to determine associations between exposures to methylmercury and persistent organic pollutants since birth and the comprehensive differential counts of white blood cells (WBC) at age 5 years.

MATERIALS AND METHODS

Extended differential count included: neutrophils, eosinophils, basophils, lymphocytes (includingT cells, NK cells, and B cells), and monocytes. Organochlorine compounds (OCs) including polychlorinated biphenyls (PCBs) and pesticides, five perfluoroalkyl substances (PFASs), and total mercury (Hg) were measured in maternal (n=56) and children's blood at 18 months (n=42) and 5 years (n=54). We constructed latent functions for exposures at three different ages using factor analyses and applied structural equation models adjusted for covariates.

RESULTS

Prenatal mercury exposure was associated with depleted total WBC, especially for lymphocytes, where a one standard deviation (SD) increase in the exposure was associated with a decrease by 23% SD (95% CI: -43, -4) in the cell count. Prenatal exposure to OCs was marginally associated with decreases in neutrophil counts. In contrast, the 5-year PFASs concentrations were associated with higher basophil counts (B=46% SD, 95% CI: 13, 79). Significantly reduced subpopulations of lymphocytes such as B cells, CD4-positive T helper cells and CD4 positive recent thymic emigrants may suggest cellular immunity effects and dysregulation of T-cell mediated immunity.

CONCLUSION

Developmental exposure to environmental immunotoxicants appears to have different impacts on WBC counts in childhood.

Prenatal pesticide exposure and PON1 genotype associated with adolescent body fat distribution evaluated by dual X-ray absorptiometry (DXA)

Many modern pesticides have endocrine disrupting abilities and early-life exposure may affect growth and disease risk later in life. Previously, we reported associations between prenatal pesticide exposure and higher childhood body fat content measured by anthropometry. The associations were affected by child PON1 Q192R genotype. We aimed to study whether prenatal pesticide exposure was still associated with body fat content and distribution in the children at puberty and the potential impact of both maternal and child PON1 Q192R genotype. In this prospective cohort study of 247 children born by occupationally exposed or unexposed women (greenhouse workers and controls) two follow-up examinations (age 10-15 and 11-16 years) including simple anthropometry, skinfold measurements, pubertal staging and blood sampling were performed. Total and regional fat% was determined by dual X-ray absorptiometry (DXA) at age 10-15. Prenatal pesticide exposure was associated with increased total, android, and gynoid fat percentage (DXA) at age 10-15 years after adjustment for sex, socioeconomic status, and puberty (all β = 0.5 standard deviation score (SDS) p < 0.05). Stratified by sex, the associations were significant in girls (total fat: β = 0.7 SDS, android-gynoid ratio: β = 0.1, both p < 0.05), but not in boys. Carrying the R-allele (child or mother, separately, or both) augmented the differences between exposed and unexposed children (total fat: β = 1.0 SDS, β = 0.8 SDS, p < 0.05, respectively, and β = 1.2 SDS, p < 0.01). No exposure-related differences were found if either the child or mother had the QQ wild-type. At age 11-16, exposed children tended to have a higher total fat% estimated by skinfolds than unexposed children (p = 0.06). No significant associations between prenatal exposure and body mass index or waist circumference were found. Prenatal pesticide exposure was associated with higher adolescent body fat content, including android fat deposition, independent of puberty. Girls appeared more susceptible than boys. Furthermore, the association depended on maternal and child PON1 Q192R genotype.

Burden of disease and costs of exposure to endocrine disrupting chemicals in the European Union: an updated analysis

A previous report documented that endocrine disrupting chemicals contribute substantially to certain forms of disease and disability. In the present analysis, our main objective was to update a range of health and economic costs that can be reasonably attributed to endocrine disrupting chemical exposures in the European Union, leveraging new burden and disease cost estimates of female reproductive conditions from accompanying report. Expert panels evaluated the epidemiologic evidence, using adapted criteria from the WHO Grading of Recommendations Assessment, Development and Evaluation Working Group, and evaluated laboratory and animal evidence of endocrine disruption using definitions recently promulgated by the Danish Environmental Protection Agency. The Delphi method was used to make decisions on the strength of the data. Expert panels consensus was achieved for probable (>20%) endocrine disrupting chemical causation for IQ loss and associated intellectual disability; autism; attention deficit hyperactivity disorder; endometriosis; fibroids; childhood obesity; adult obesity; adult diabetes; cryptorchidism; male infertility, and mortality associated with reduced testosterone. Accounting for probability of causation, and using the midpoint of each range for probability of causation, Monte Carlo simulations produced a median annual cost of €163 billion (1.28% of EU Gross Domestic Product) across 1000 simulations. We conclude that endocrine disrupting chemical exposures in the EU are likely to contribute substantially to disease and dysfunction across the life course with costs in the hundreds of billions of Euros per year. These estimates represent only those endocrine disrupting chemicals with the highest probability of causation; a broader analysis would have produced greater estimates of burden of disease and costs.

Toxicology research for precautionary decision-making and the role of Human & Experimental Toxicology

A key aim of toxicology is the prevention of adverse effects due to toxic hazards. Therefore, the dissemination of toxicology research findings must confront two important challenges: one being the lack of information on the vast majority of potentially toxic industrial chemicals and the other being the strict criteria for scientific proof usually required for decision-making in regard to prevention. The present study ascertains the coverage of environmental chemicals in four volumes of Human & Experimental Toxicology and the presentation and interpretation of research findings in published articles. Links in SciFinder showed that the 530 articles published in four selected volumes between 1984 and 2014 primarily dealt with metals (126 links) and other toxicants that have received substantial attention in the past. Thirteen compounds identified by US authorities in 2006 as high-priority substances, for which toxicology documentation is badly needed, were not covered in the journal issues at all. When reviewing published articles, reliance on p values was standard, and non-significant findings were often called 'negative.' This tradition may contribute to the perceived need to extend existing research on toxic hazards that have already been well characterized. Several sources of bias towards the null hypothesis can affect toxicology research, but are generally not considered, thus adding to the current inclination to avoid false positive findings. In this regard, toxicology is particularly prone to bias because of the known paucity of false positives and, in particular, the existence of a vast number of toxic hazards which by default are considered innocuous due to lack of documentation. The Precautionary Principle could inspire decision-making on the basis of incomplete documentation and should stimulate a change in toxicology traditions and in toxicology research publication.

Spermatogenic capacity in fertile men with elevated exposure to polychlorinated biphenyls

BACKGROUND

Endocrine disrupting industrial chemicals, such as polychlorinated biphenyls (PCBs), are suspected to adversely affect male reproductive functions.

OBJECTIVES

The Faroe Islands community exhibits an unusually wide range of exposures to dietary contaminants, and in this setting we examined the possible association between PCB exposure and semen quality and reproductive hormones in fertile Faroese men.

METHODS

Participants in this cross-sectional study include 266 proven fertile men residing in the Faroe Islands. PCB levels and hormone profiles were measured in serum samples taken at the clinical examination that included semen quality parameters.

RESULTS

A significant positive association was seen between serum-PCB and the testosterone/estradiol ratio (p=0.04). In the unadjusted analyses, elevated PCB exposure was associated with increased serum concentrations of SHBG (p=0.01) and FSH (p=0.05). We found no association between the serum PCB concentration and the semen quality variables.

CONCLUSION

In this population of highly exposed fertile men, the current serum-PCB concentration was associated with higher androgen/estrogen ratio. Further studies are needed to establish the findings and further document PCB-associated hormonal effects, any time windows of increased susceptibility, and the role of PCB in sub-fecundity.

Exposure to persistent organic pollutants and sperm sex chromosome ratio in men from the Faroe Islands

People in the Arctic as well as fishermen on the polluted Swedish east coast are highly exposed to persistent organic pollutants (POPs). These compounds have been shown to affect the sperm Y:X chromosome ratio. In present study, the aim was to investigate whether polychlorinated biphenyl (PCB) congeners and 1,1,-dichloro-2,2,-bis(p-chlorophenyl)ethane (p,p'-DDE) influence sperm sex chromosome ratio in Faroese men, and whether these men differ regarding Y:X ratio compared to Greenland Inuit and Swedish fishermen. The study population (n=449) consisted of young men from the general population (n=276) as well as proven fertile men (n=173). The Y:X ratio was assessed by fluorescent in situ hybridization. Serum concentrations of POPs were measured using gas chromatography. Associations between POP concentrations and Y:X ratio were calculated using linear and non-linear regression models as well as trend analysis and pairwise comparison of exposure data categorized into quartiles. The selected POPs were associated with Y:X ratio in fertile Faroese men, but not in the total population; p,p'-DDE (95% CI for B=-0.005 to -0.001, p=0.005) and ΣPCB (95% CI for B=-0.005 to -0.001, p=0.012). Since p,p'-DDE and ΣPCB correlated significantly (r=0.927, p<0.001), the results involving the exposure variables can be regarded as a single finding. The Y:X ratio for the total Faroese population was 0.500±0.018, which was statistically significantly lower than in both Inuit and Swedish fishermen (0.512 for both). In conclusion, Faroese men presented with lower Y:X ratio than Greenland Inuit and Swedish fishermen. Although no direct health effects are expected due to the lower Faroese Y:X ratio, it could be indicative of adverse effects on the reproductive system.

[The use of intrauterine device in nulliparous over 18 years: a Belgian consensus]

Under the presidency of prof. H. Depypere (UZ Ghent) and Prof. P. Simon (ULB Erasme) a Belgian panel of thirteen experts (gynecologists, representatives of universities and scientific associations for gynecology-obstetrics) reached a consensus on the use of intrauterine systems, both copper IUDs as hormone IUDs, in nultiparous women.

Smaller genitals at school age in boys whose mothers were exposed to non-persistent pesticides in early pregnancy

Endocrine disrupting chemicals are believed to play a role in the development of the testicular dysgenesis syndrome. Many pesticides are known to have endocrine disrupting abilities. In a previous study, sons of women who were occupationally exposed to non-persistent pesticides in early pregnancy showed signs of impaired reproductive function (reduced genital size and altered serum hormone concentrations) at three months of age. To assess the possible long-term effects of prenatal pesticide exposure, the boys were re-examined at 6-11 years. The 94 boys (59 exposed, 35 unexposed) underwent genital examinations including ultrasound of testicular volumes, puberty staging (Tanner), anthropometry, and blood sampling. Only a few of the boys had reached puberty (n = 3). Among prepubescent boys, testicular volume and penile length (age- and weight-adjusted) were reduced if mothers were exposed to pesticides. The effects were associated with the maternal exposure levels, so that high-exposed boys had smaller genitals than medium-exposed boys, who had smaller genitals than those who were unexposed. Boys of mothers in the high exposure group (n = 23) had 24.7% smaller testes (95% CI: -62.2; -10.1) and 9.4% shorter penile length (95% CI: -16.8; -1.1) compared with the unexposed. The testicular volume and penile length at school age could be tracked to measures from the same boys made at 3 months, e.g. those that had small testes at school age also had small testes at 3 months. Pituitary and testicular hormone serum concentrations did not differ between exposed and unexposed boys. Eight prenatally exposed boys had genital malformations (no unexposed). These boys had smaller testis, shorter penile length and lower inhibin B concentrations than prepubertal boys without genital malformations. The findings support the results obtained at three months of age and indicate that prenatal pesticide exposure has long-term effects on reproductive function in boys.

Carcinogenicity of occupational nickel exposures: an evaluation of the epidemiological evidence

The health effects documented in recent epidemiological studies of nickel-exposed workers relate to past exposures, mostly of unknown magnitude and unknown nickel speciation. Major studies have been carried out at nickel smelters and refineries. Although each study suffers from some deficiencies, as is common in such retrospective studies, the findings in concert strongly indicate that nickel emitted from the calcining and sintering operations is a potent carcinogen resulting in nasal and pulmonary cancers. Some risk appears to be present in other refinery operations, such as Orford furnace, copper and nickel sulfate, and crushing departments, and one study has suggested a risk associated with soluble nickel compounds in the electrolysis department, although this finding has not been confirmed. Only one study demonstrated an exposure-response relationship, which, however, was not statistically significant. Other studies showed a relationship between increased exposure time and augmented cancer risk. In nickel-using industries, no excess cancer related to nickel exposures has been demonstrated beyond doubt; concurrent exposures to other potential carcinogens constitute a confounding variable that makes interpretation difficult. However, the studies have not excluded that a cancer hazard may be present outside the nickel-producing facilities. Further, case-referent studies of respiratory cancers suggest that a nickel-related etiology may well exist in the nickel-using industries. As the exact identity of the carcinogenic form or forms of nickel remains unknown, exposure to all nickel compounds should be kept as low as reasonably achievable.

Individual radiation therapy patient whole-body phantoms for peripheral dose evaluations: method and specific software

This study presents a method aimed at creating radiotherapy (RT) patient-adjustable whole-body phantoms to permit retrospective and prospective peripheral dose evaluations for enhanced patient radioprotection. Our strategy involves virtual whole-body patient models (WBPM) in different RT treatment positions for both genders and for different age groups. It includes a software tool designed to match the anatomy of the phantoms with the anatomy of the actual patients, based on the quality of patient data available. The procedure for adjusting a WBPM to patient morphology includes typical dimensions available in basic auxological tables for the French population. Adjustment is semi-automatic. Because of the complexity of the human anatomy, skilled personnel are required to validate changes made in the phantom anatomy. This research is part of a global project aimed at proposing appropriate methods and software tools capable of reconstituting the anatomy and dose evaluations in the entire body of RT patients in an adapted treatment planning system (TPS). The graphic user interface is that of a TPS adapted to obtain a comfortable working process. Such WBPM have been used to supplement patient therapy planning images, usually restricted to regions involved in treatment. Here we report, as an example, the case of a patient treated for prostate cancer whose therapy planning images were complemented by an anatomy model. Although present results are preliminary and our research is ongoing, they appear encouraging, since such patient-adjusted phantoms are crucial in the optimization of radiation protection of patients and for follow-up studies.

Prevalence and incidence of Parkinson's disease in The Faroe Islands

OBJECTIVE

A study in The Faroe Islands in 1995 suggested a high prevalence of idiopathic Parkinson's disease (IPD) and total parkinsonism of 187.6 and 233.4 per 100,000 inhabitants respectively.

METHODS

Detailed case-finding methods 10 years later were used and a neurologist has verified the diagnosis.

RESULTS

The crude prevalence of IPD and total parkinsonism was 206.7 per 100,000 and 227.4 per 100,000 respectively. The age-adjusted prevalence is twice as high as data from Norway and Denmark. Age at initiation of treatment and the fatality rate did not explain the increased prevalence. During 1995-2005, the average annual incidence was 21.1 per 100,000 persons for Parkinson's disease, and 22.9 per 100,000 persons, if including atypical parkinsonism.

CONCLUSION

The high prevalence was verified and linked to a high incidence. The cause of the high prevalence is unknown, but neurotoxic contaminants in traditional food may play a role in the pathogenesis in this population, perhaps jointly with genetic predisposition.

Developmental neurotoxicity of industrial chemicals

Neurodevelopmental disorders such as autism, attention deficit disorder, mental retardation, and cerebral palsy are common, costly, and can cause lifelong disability. Their causes are mostly unknown. A few industrial chemicals (eg, lead, methylmercury, polychlorinated biphenyls [PCBs], arsenic, and toluene) are recognised causes of neurodevelopmental disorders and subclinical brain dysfunction. Exposure to these chemicals during early fetal development can cause brain injury at doses much lower than those affecting adult brain function. Recognition of these risks has led to evidence-based programmes of prevention, such as elimination of lead additives in petrol. Although these prevention campaigns are highly successful, most were initiated only after substantial delays. Another 200 chemicals are known to cause clinical neurotoxic effects in adults. Despite an absence of systematic testing, many additional chemicals have been shown to be neurotoxic in laboratory models. The toxic effects of such chemicals in the developing human brain are not known and they are not regulated to protect children. The two main impediments to prevention of neurodevelopmental deficits of chemical origin are the great gaps in testing chemicals for developmental neurotoxicity and the high level of proof required for regulation. New, precautionary approaches that recognise the unique vulnerability of the developing brain are needed for testing and control of chemicals.

Trends in mercury in hair of Greenlandic polar bears (Ursus maritimus) during 1892-2001

Mercury concentrations in hair from 397 Greenland polar bears (Ursusmaritimus) sampled between 1892 and 2001 were analyzed for temporal trends. In East Greenland the concentrations showed a significant (p < 0.0001, n = 27) increase of 3.1%/year in the period 1892-1973. In Northwest Greenland, a similar (p < 0.0001, n = 69) increase of 2.1%/year was found, which continued until 1991, when the most recent samples were obtained. In East Greenland, a significant (p = 0.009, n = 322) decrease of 0.8%/year was observed after 1973. Two Northwest Greenland samples from 1300 A.D. had a mean value of 0.52 mg/kg of dry weight, which can be considered as a baseline level. The Hg concentration during 1985-1991 from Northwest Greenland (mean value of 7.45 mg/kg of dry weight) was more than 14-fold higher than the assumed baseline level from 1300 A.D. from the same region (i.e., about 93% anthropogenic). Although a decrease was found in East Greenland after 1973, the concentration is still ca. 11-fold higher than the baseline level (i.e., about 90% anthropogenic).

Birthweight in a fishing community: significance of essential fatty acids and marine food contaminants

BACKGROUND

Marine food provides essential fatty acids that are important during pregnancy, but the benefits may be limited at high intakes and by seafood contaminants.

METHODS

In the fishing community of the Faroe Islands, 182 pregnant women with spontaneous singleton births were consecutively recruited for a cohort in 1994- 1995. Concentrations of fatty acids and seafood contaminants in blood samples were analysed as predictors of gestational length and birthweight.

RESULTS

Serum concentrations of eicosapentaenoic acid (EPA) increased with maternal marine food intake, while the tendency was less clear for docosahexaenoic acid (DHA). An increase in the relative concentration of DHA in cord serum phospholipids by 1% was associated with an increased duration of gestation by 1.5 days (95% CI : 0.7-2.2). However, birthweight adjusted for gestational length decreased by 246 g (95% CI : 16-476) for each increase by 1% of the EPA concentration in cord serum. Concentrations of the seafood pollutants mercury and polychlorinated biphenyls (PCB) were associated with fatty acids levels, but the contaminants did not appear to affect any of the outcome parameters.

CONCLUSION

An increased intake of marine fats appears to prolong the duration of gestation, but birthweight adjusted for gestational age may decrease at high intake levels. This effect does not seem to be due to increased exposures to seafood contaminants.

Benchmark dose calculation from epidemiological data

A threshold for dose-dependent toxicity is crucial for standards setting but may not be possible to specify from empirical studies. Crump (1984) instead proposed calculating the lower statistical confidence bound of the benchmark dose, which he defined as the dose that causes a small excess risk. This concept has several advantages and has been adopted by regulatory agencies for establishing safe exposure limits for toxic substances such as mercury. We have examined the validity of this method as applied to an epidemiological study of continuous response data associated with mercury exposure. For models that are linear in the parameters, we derived an approximative expression for the lower confidence bound of the benchmark dose. We find that the benchmark calculations are highly dependent on the choice of the dose-effect function and the definition of the benchmark dose. We therefore recommend that several sets of biologically relevant default settings be used to illustrate the effect on the benchmark results and to stimulate research that will guide an a priori choice of proper default settings.

Neurobehavioral deficits associated with PCB in 7-year-old children prenatally exposed to seafood neurotoxicants

Prenatal exposure to polychlorinated biphenyls (PCBs) was examined by analysis of cord tissue from 435 children from a Faroese birth cohort. Analysis of 50 paired cord blood samples showed excellent correlation with the cord tissue concentration (r=.90). Among 17 neuropsychological outcomes determined at age 7 years, the cord PCB concentration was associated with deficits on the Boston Naming Test (without cues, two-tailed P=.09 not adjusted for mercury; with cues, P=.03), the Continuous Performance Test reaction time (P=.03), and, possibly, on long-term recall on the California Verbal Learning Test (P=.15). The association between cord PCB and cord-blood mercury (r=.42) suggested possible confounding. While no PCB effects were apparent in children with low mercury exposure, PCB-associated deficits within the highest tertile of mercury exposure indicated a possible interaction between the two neurotoxicants. PCB-associated increased thresholds were seen at two of eight frequencies on audiometry, but only on the left side, and no deficits occurred on evoked potentials or contrast sensitivity. The limited PCB-related neurotoxicity in this cohort appears to be affected by concomitant methylmercury exposure.

Impact of contrast sensitivity performance on visually presented neurobehavioral tests in mercury-exposed children

Presentation of neuropsychological tests on a computer screen may involve a visual challenge to the examinee. The possible need for adjustment for visual contrast sensitivity on test performance was therefore determined from data on 917 mercury-exposed children who were examined at age 7 years. Contrast sensitivity was found to be associated with performance on the computer-assisted Continuous Performance Test. However, it showed similar associations with performance on traditional pencil-and-paper tests, especially Bender Visual Motor Gestalt Test and Wechsler Intelligence Scale for Children-Revised (WISC-R) Block Designs. Contrast sensitivity was not associated with prenatal mercury exposure, and adjustment for visual function had only a negligible effect on the regression coefficients for mercury as predictor of neuropsychological deficits. The mercury-associated neurobehavioral deficits are therefore unlikely to be due to mercury-induced visual system dysfunction causing secondary deficits in cognitive domain testing. Visuospatial processing appears to be a determinant in contrast sensitivity performance, and careful consideration of whether to control for contrast sensitivity in future studies of neurotoxicant effects is therefore recommended.

Selection bias in determining the age dependence of waiting time to pregnancy

Many studies have found decreased fecundability, that is, the ability to conceive in a menstrual cycle, with increasing female age. To evaluate the effect of maternal age on waiting time to pregnancy, the authors reviewed hospital charts of all pregnant women attending prophylactic antenatal care at Odense University Hospital, Denmark, during 1972-1987. Only the first pregnancy of each woman and only planned pregnancies were included (n = 14,754). The fecundability odds ratio (FR) was calculated as the odds of a conception in a menstrual cycle among the older women divided by the odds among women aged 15-24 years. The FR for women aged 25-29 years was 1.12 (95% confidence interval (CI): 1.04, 1.20), for women aged 30-34 years it was 1.15 (95% CI: 1.01, 1.30), and for women above 34 years the FR was 2.44 (95% CI: 1.84, 3.22) after adjustment for confounders. The increased fecundability with age is contrary to previous studies and may be explained by selection bias, as sterile women were not included. In addition, some very fertile young women who became pregnant by accident before efficient birth control methods were available and therefore were excluded from time to pregnancy studies may now use oral contraceptives until they plan a pregnancy later in life and are included.

Maternal seafood diet, methylmercury exposure, and neonatal neurologic function

OBJECTIVE

To determine whether neonatal neurologic function is adversely affected by seafood contaminants from maternal diet during pregnancy.

STUDY DESIGN

One hundred eighty-two singleton term births were evaluated in the Faeroe Islands, where marine food includes pilot whale. Maternal serum, hair, and milk and umbilical cord blood were analyzed for contaminants. Levels of essential fatty acids, selenium, and thyroid hormones were determined in cord blood. Each infant's neurologic optimality score was determined at 2 weeks of age adjusted for gestational age, and predictors were assessed by regression analysis.

RESULTS

Exposures to methylmercury and polychlorinated biphenyls were increased in relation to maternal seafood intake, as were omega3 fatty acid concentrations in cord serum. Thyroid function was normal. After adjustment for confounders, a 10-fold increase of the cord-blood mercury concentration was associated with a decreased neurologic optimality score of 2.0 (P =. 03). This effect corresponds to a decrease in gestational age of about 3 weeks. Other indicators of the seafood diet had no effect on this outcome.

CONCLUSIONS

Prenatal exposure to methylmercury from contaminated seafood was associated with an increased risk of neurodevelopmental deficit. Thus in this North Atlantic population, methylmercury constituted an important neurologic risk factor, although effects of other seafood components were not detectable.

Toxicologic evidence of developmental neurotoxicity of environmental chemicals

Developmental neurotoxicity constitutes effects occurring in the offspring primarily as a result of exposure of the mother during pregnancy and lactation. To exert their effect, these chemicals or their metabolites must pass the placenta and/or the blood-brain barrier. In experimental animals, exposure to neurotoxic chemicals during critical periods of brain development has induced permanent functional disturbances in the CNS. Although available data suggest that proper animal models exist, only few chemicals have been tested. Neurotoxicity testing is not required by national authorities for classification of chemicals. Epidemiological evidence is very limited, but severe irreversible effects have been observed in humans following in utero exposures to a few known developmental neurotoxicants. The large number of chemicals with a potential for developmental neurotoxicity in humans stresses the importance of generating basic kinetic data on these chemicals based on relevant experimental models. First of all, data are needed on their ability to pass the placenta and the developing blood-brain barrier, to accumulate, and to be metabolized in the placenta and/or the fetus. These kinetic data will be essential in establishing a scientifically based hazard evaluation and risk assessment.

Effects of industrial detergents on the barrier function of human skin

Detergents are involved in the causation of contact dermatitis and in promoting percutaneous absorption of toxic chemicals, but limited information is available to allow an assessment of their relative effects on the skin barrier function. The effect of detergents on skin permeability to water and nickel was examined in an in-vitro model using human skin. Twenty-four of the most widely used detergents were studied. After a two-hour exposure to an aqueous detergent solution, penetration of labeled model compounds was followed for 66 hours. Interindividual variation was substantial, but 12 of the detergents caused statistically significant increases in the penetration of water, nickel, or both. Nonionic detergents were as likely as anionic detergents to have this effect. This study demonstrates that useful information may be obtained by a simple in-vitro method, and that such data may provide a basis for substitution efforts.

Benchmark dose calculations of methylmercury-associated neurobehavioural deficits

Prenatal methylmercury exposure is associated with neuropsychological deficits in Faroese children at age 7 years. Lower confidence bounds of benchmark doses (BMDLs) have now been calculated. With the cord-blood mercury concentration as the dose parameter, a logarithmic dose-response model tended to show a better fit than a linear dose model for the attention, language and verbal memory tests. The lowest BMDLs averaged approximately 5 microgram/l cord blood, which corresponds to a maternal hair concentration of approximately 1 microgram/g. However, most BMDLs for hair mercury concentrations were higher. Thus, the results of the benchmark calculations depend on the assumed dose-response model.

Linac radiosurgery for cerebral arteriovenous malformations: results in 169 patients

PURPOSE

To present the SALT group results using Linac radiosurgery (RS) for AVM in 169 evaluable patients treated from January 1990 thru December 1993.

METHODS AND MATERIALS

Median age was 33 years (range 6-68 years). Irradiation was the only treatment in 55% patients. Other treatment modalities had been used prior to RS in 45%: one or more embolizations in 36%, surgery in 6%, and embolization and surgery in 3% patients. Nidus were supratentorial in 94% patients, infratentorial in 6% patients. Circular 15 MV x-ray minibeams (6-20 mm) were delivered in coronal arcs by a GE-CGR Saturne 43 Linac. Patient set-up included a Betti arm-chair, a Talairach frame. Prescribed peripheral dose was 25 Gy on the 60%-70% isodose (max dose 100%). Arteriographic results were reassessed in December 1997 at 48 to 96 months follow-up.

RESULTS

The overall obliteration rate (OR) was 64% (108/169). AVM volumes ranged from 280 to 19,920 mm(3), median 2460 mm(3). OR was 70% for AVM </= 4200 mm(3) 4200 mm(3) (p 25 mm (p = 0.04). OR was 71%, in the absence of embolization, vs. 54% for previously embolized nidus (p = 0.03). OR was 71% for monocentric RS vs. 54% for multi-isocenters (p 28 Gy vs. 55% for values </= 28 Gy (p 79% vs. 57% for lower values (p 17 Gy, vs. 59% for mLd </= 16 Gy (p 40%, vs. 54% for mLi </= 40% (p 85% vs. 60% for CR </= 84% (NS). For patients treated according to our protocol, i.e., 24-26 Gy on the 60%-70% isodoses, OR was higher (68%) than for other patients (47%) (p = 0.02). After multivariate analysis, absence of previous embolization and mono isocentric-irradiation were independent factors predicting obliteration. Complications were: recurrent hemorrhage, 4 patients (1 patient died); brain necrosis on MRI, 2 patients; subsequent epilepsy, 4 patients; other subsequent neurologic deficits, 3 patients.

CONCLUSION

Overall OR was 64% (48-96 months follow-up). After monovariate analysis higher ORs were associated with smaller volumes </= 4200 mm(3), smaller nidus size </= 25 mm, absence of prior embolization, monoisocentric RS, higher values for mean and minimum lesion doses and compliance to our protocol. Higher values for the peripheral dose and isodose tended to give better results. Multivariate analysis showed that the absence of prior embolization and monoisocentric irradiation were independent factors predicting successful irradiation.

Organochlorine exposure and breast cancer survival

Recent research suggests that exposure to organochlorines, such as dieldrin that possess estrogenic properties, may increase the risk of breast cancer by promoting growth of malignant cells. Whether this potential also affects malignant cells not eradicated by treatment, and thereby survival, is unknown. To evaluate this blood samples from female participants in the Copenhagen City Heart Study, Denmark, were analyzed for organochlorines. A total of 195 breast cancer cases, who each provided two blood samples that were taken in 1976-78 and 1981-83, respectively, were included in the survival analysis. Dieldrin had a significant adverse effect on overall survival and breast cancer specific survival (RR, 2.78, 95% CI, 1. 38-5.59, P trend < 0.01; RR, 2.61, 95% CI, 0.97-7.01, P trend < 0. 01). This association was strengthened when exposure was assessed as the average serum concentration of the two measurements. These findings suggest that past exposure to estrogenic organochlorines such as dieldrin may not only affect the risk of developing breast cancer but also the survival.

[Organochlorine compounds and breast cancer--is there a connection between environmental pollution and breast cancer?]

Some organochlorine compounds may have weak oestrogenic effects and are therefore suspected of increasing the risk of breast cancer. The risk of breast cancer was assessed prospectively in relation to the serum concentration of several organochlorines. In all 240 women, who developed breast cancer between 1976 and 1993 were together with 477 breast cancer-free controls enrolled in a cohort-nested case-control study. The serum dieldrin concentration was associated with a significantly increased dose-related risk of breast cancer (Odds Ratio 2.05; 95% confidence interval 1.17-3.57; p for trend 0.01). There was no overall association between risk of breast cancer and DDT or polychlorinated biphenyls. The results support the hypothesis that exposure to oestrogenic organochlorines may increase the risk of breast cancer.

Repeated measurements of organochlorine exposure and breast cancer risk (Denmark)

OBJECTIVE

To prospectively evaluate if repeated measurements of organochlorine exposure provide a more precise measure of breast cancer risk.

METHODS

In the Copenhagen City Heart Study (CCHS) participants donated blood twice, in 1976-1978 and 1981 1983. Information on breast cancer risk factors was obtained through standardized questionnaires. A cohort nested case-control study of 155 cases and 274 matched breast cancer-free controls who had participated in both CCHS examinations was conducted. The average serum organochlorine concentration over the course of the two examinations was used, testing a possible association between organochlorine exposure and breast cancer risk.

RESULTS

A high serum concentration of p,p'-DDT over the course of the two examinations was associated with a more than three-fold significantly increased risk of breast cancer, and a dose-response relationship was apparent. Furthermore, the risk of breast cancer increased with increasing serum concentrations of PCB congener 118 and 138 and the total amount of DDT isomers (sigmaDDT), but the trends were not significant.

CONCLUSION

This study provides new evidence of the adverse effect of some organochlorines on breast cancer risk. Furthermore, repeated assessment of exposure during a relevant time period may provide a more precise risk estimate than a single measurement.