Middle-ear disease in children exposed prenatally to polychlorinated biphenyls and polychlorinated dibenzofurans

Updating an Overview of Teratology

In this chapter, the authors aim to update an overview of the principles of teratology, beginning with the definition of teratology, the critical point at which this process occurs, and some of the most common etiological agents that improve our understanding of teratology.Modern teratology has greatly improved in recent years with advances in new methods in molecular biology, toxicology, animal laboratory science, and genetics, increasing our knowledge of ambient influences. Nevertheless, there is a lot to do to reduce the influence of hazardous intervening agents, whether they target our genetics or not, that can negatively affect pregnancy and induce congenital development disorders, including morphological, biochemical, or behavioral defects.Certain agents might indeed be related to certain defects, but we have not been able to identify the cause of most congenital defects, which highlights the importance of finding and testing out new genetics techniques and conducting laboratory animal science to unravel the etiology and pathogenicity of each congenital defect.

Current knowledge on the effects of environmental contaminants in early life nutrition

Breast milk represents the optimal source of feeding for newborns, in terms of nutritional compounds and as it provides immunological, metabolic, organic, and neurological well-being. As a complex biological fluid, it consists not only of nutritional compounds but also contains environmental contaminants. Formulas through production, contact with bottles and cups, and complementary feeding can also be contaminated. The current review focuses on endocrine-disrupting chemicals, and made-man xenoestrogens present in the environment and both commonly present in food sources, agricultural practices, packaging, consumer products, industry, and medical care. These contaminants are transferred by passive diffusion to breast milk and are delivered during breastfeeding. They mainly act by activating or antagonizing hormonal receptors. We summarize the effects on the immune system, gut microbiota, and metabolism. Exposure to endocrine-disrupting chemicals and indirect food additives may induce tissue inflammation and polarize lymphocytes, increase proinflammatory cytokines, promote allergic sensitization, and microbial dysbiosis, activate nuclear receptors and increase the incidence of allergic, autoimmune, and metabolic diseases. Breast milk is the most important optimal source in early life. This mini-review summarizes current knowledge on environmental contaminants and paves the way for strategies to prevent milk contamination and limit maternal and infant exposure during pregnancy and the first months of life.

Prenatal exposure to dioxin-like compounds is associated with decreased cord blood IgE and increased risk of wheezing in children aged up to 7years: The Hokkaido study

INTRODUCTION

In utero exposure to dioxin-like compounds (DLCs) may cause imbalance of immune development in early infancy. However, there are few epidemiological studies into the effects of in utero exposure to DLCs on allergies and infections during childhood. This study evaluates associations between concentrations of maternal DLCs and cord blood immunoglobulin (Ig) E, as well as allergies and infections during childhood.

METHOD

We recruited 514 pregnant women in a maternity hospital in Sapporo, Japan, and measured concentrations of DLCs in 426 maternal blood samples using high-resolution gas chromatography/high-resolution mass spectrometry. We examined the relationship between concentrations of maternal DLCs and cord blood IgE at birth (n=239), as well as for allergies and infections in children at 3.5 (n=327) and 7 (n=264) years, using regression analysis adjusted for confounding variables.

RESULTS

We found a positive association between maternal DLC concentrations and frequency of wheezing in children aged up to 7years [odds ratio (OR); 7.81 (95% confidence interval (CI), 1.42 to 42.9)]. At 3.5years, boys showed inverse associations between maternal DLC concentrations and cord blood IgE [partial regression coefficient; -0.87 (95% CI), -1.68 to -0.06], and frequency of wheezing [OR; 0.03 (95% CI), 0.00 to 0.94] but girls did not.

DISCUSSION

As one reason for the significant association observed at 7 but absent at 3.5years, we suggest that allergic symptoms are more obvious in older children due to matured immune function.

CONCLUSION

The findings suggest that prenatal exposure to DLCs may modify offspring immune responses and result in increased risk of allergy among children of school age.

An Overview of Teratology

In this chapter, we provide an overview of the basic principles of teratology, beginning with its definition, the critical point for teratogenesis to occur and the most evident etiological agents to improve the understanding of this science.Teratology is a recent science that began in the early twentieth century, and has greatly improved over the recent years with the advancements in molecular biology, toxicology, animal laboratory science, and genetics, as well as the improvement on the knowledge of the environmental influences.Nevertheless, more work is required to reduce the influence of hazardous products that could be deleterious during pregnancy, thus reducing teratogenic defects in the newborn. While some teratogenic defects are attributed to their agents with certainty, the same for a lot of other such defects is lacking, necessitating consistent studies to decipher the influence of various teratogenic agents on their corresponding teratogenic defects. It is here that the laboratory animal science is of great importance both in the present and in the future.

Health effects associated with measured levels of contaminants in the Arctic

The Human Health Assessment Group has over the past decade recommended that effect studies be conducted in the circumpolar area. Such studies examine the association between contaminant exposure in the Arctic populations and health effects. Because foetuses and young children are the most vulnerable, effect studies are often prospective child cohort studies. The emphasis in this article is on a description of the effects associated with contaminant exposure in the Arctic. The main topics addressed are neurobehavioural, immunological, reproductive, cardiovascular, endocrine and carcinogenic effect. For each topic, the association between exposure and effects is described, and some results are reported for similar studies outside the Arctic.

Gestational exposure to polychlorinated biphenyls and dibenzofurans induced asymmetric hearing loss: Yucheng children study

INTRODUCTION

In 1979, approximately 2000 people in central Taiwan were exposed to polychlorinated biphenyls and dibenzofurans (PCBs/PCDFs) due to ingestion of contaminated rice oil. The children born to mothers exposed to PCBs/PCDFs were called Yucheng children. We conducted a follow-up study to examine the association between gestational PCBs/PCDFS exposure and auditory function in Yucheng children's early adulthood.

METHODS

In 1985 and early 1992, Yucheng children and their age, gender, socio-economic matched unexposed referent children were recruited for physical examination and long-term follow-ups. In 2007, Yucheng children and referent children were invited to participate in a health examination, including assessment of pure-tone air-conduction thresholds and distortion product otoacoustic emissions (DPOAEs) test. Gestational exposure to PCBs/PCDFs in Yucheng children were estimated by back-extrapolation of their mother's serum concentration to the time of childbirth.

RESULTS

A total of 86 Yucheng children (51.2% males) and 97 referent children (50.5% males) were included for analysis. No difference was found in demographic characteristics between two groups. Among the Yucheng children, 53 had estimated PCBs/PCDFs concentrations. We found that Yucheng children were at higher risk of having elevated hearing threshold at low frequencies in the right ear. Estimated maternal concentrations of 2,3,4,7,8-pnCDF at the time of birth were associated with increased hearing thresholds and decreased DPOAEs amplitudes at low frequencies in the right ear.

CONCLUSION

Gestational exposure to PCBs/PCDFs caused adverse asymmetrical hearing effects detectable even in early adulthood.

Prenatal and postnatal serum PCB concentrations and cochlear function in children at 45 months of age

BACKGROUND

Some experimental and human data suggest that exposure to polychlorinated biphenyls (PCBs) may induce ototoxicity, though results of previous epidemiologic studies are mixed and generally focus on either prenatal or postnatal PCB concentrations exclusively.

OBJECTIVES

Our aim was to evaluate the association between pre- and postnatal PCB concentrations in relation to cochlear status, assessed by distortion product otoacoustic emissions (DPOAEs), and to further clarify the critical periods in development where cochlear status may be most susceptible to PCBs.

METHODS

A total of 351 children from a birth cohort in eastern Slovakia underwent otoacoustic testing at 45 months of age. Maternal pregnancy, cord, and child 6-, 16-, and 45-month blood samples were collected and analyzed for PCB concentrations. At 45 months of age, DPOAEs were assessed at 11 frequencies in both ears. Multivariate, generalized linear models were used to estimate the associations between PCB concentrations at different ages and DPOAEs, adjusting for potential confounders.

RESULTS

Maternal and cord PCB-153 concentrations were not associated with DPOAEs at 45 months. Higher postnatal PCB concentrations at 6-, 16-, and 45-months of age were associated with lower (poorer) DPOAE amplitudes. When all postnatal PCB exposures were considered as an area-under-the-curve metric, an increase in PCB-153 concentration from the 25th to the 75th percentile was associated with a 1.6-dB SPL (sound pressure level) decrease in DPOAE amplitude (95% CI: -2.6, -0.5; p = 0.003).

CONCLUSIONS

In this study, postnatal rather than maternal or cord PCB concentrations were associated with poorer performance on otoacoustic tests at age 45 months.

Current status of the epidemiologic evidence linking polychlorinated biphenyls and non-hodgkin lymphoma, and the role of immune dysregulation

BACKGROUND

Although case-control studies conducted to date have largely affirmed the relationship between polychlorinated biphenyls (PCBs) and non-Hodgkin lymphoma (NHL), occupational cohort studies of PCB-exposed workers have been generally interpreted as negative, thereby raising doubts about a potential causal association. A common theme of immune dysregulation unifies many of NHL's strongest risk factors, and several authors have posited that subclinical immune dysregulation may increase NHL risk by decreasing host resistance, reducing control of cellular proliferation and differentiation, and diminishing tumor surveillance mechanisms.

OBJECTIVES

The goals of this review were a) to evaluate the epidemiological research examining the association between PCB exposure and NHL and discuss the contribution to the weight of evidence of case-control studies and occupational cohort studies; and b) to summarize the evidence for immune dysregulation as a means by which PCBs may cause NHL.

METHODS

We performed a literature search using PubMed and seven additional online biomedical and toxicological referencing libraries to identify literature published through August 2011.

DISCUSSION AND CONCLUSIONS

Overall, we conclude that the weight of evidence supports a causal role of PCBs in lymphomagenesis. The strongest epidemiological evidence for the relationship between PCBs and NHL comes from case-control studies conducted among the general population. Epidemiological and toxicological data demonstrating immunosuppressive and inflammatory effects of PCBs further contribute to the weight of evidence by providing a plausible explanation for how PCBs can cause NHL through immune dysregulation.

Effects of prenatal exposure to dioxin-like compounds on allergies and infections during infancy

Dioxin-like compounds are endocrine disruptors. The effects of prenatal exposure to environmental levels of dioxins on immune function during infancy have not been clarified, although dioxins induce immunosuppression in offspring of animals. Moreover, human studies have not assessed the effects of gender- or congener-specific differences. The purpose of this study was to investigate the association between dioxin levels in maternal blood and the risk of infection and allergies in infancy. We examined 364 mothers and their infants enrolled in a Hokkaido Study on Environment and Children's Health between 2002 and 2005 in Sapporo, Japan. Relevant information was collected from a baseline questionnaire during pregnancy, medical records at delivery, and a follow-up questionnaire when the child was 18 months of age that assessed development of allergies and infections in infancy. Dioxin-like compound levels in maternal blood were measured with high-resolution gas chromatography/high-resolution mass spectrometry. Relatively higher levels of polychlorinated dibenzofuran were associated with a significantly increased risk of otitis media, especially among male infants (odds ratio=2.5, 95% confidence interval=1.1-5.9). Relatively higher levels of 2,3,4,7,8-pentachlorodibenzofuran were also associated with a significantly increased risk of otitis media (odds ratio=5.3, 95% confidence interval=1.5-19). However, we observed a weak association between dioxin-like compound levels and allergic symptoms in infancy. At environmental levels, prenatal exposure to dioxin-like compounds may alter immune function and increase the risk of infections in infancy, especially among males. The compound 2,3,4,7,8-pentachlorodibenzofuran may be responsible for this.

Increased thyroid volume, prevalence of thyroid antibodies and impaired fasting glucose in young adults from organochlorine cocktail polluted area: outcome of transgenerational transmission?

In 137 females (F) and 94 males (M) aged 21-35 years from organochlorines (OCs) polluted area (POLL) increased thyroid volume (ThV), prevalence of antibodies to thyroperoxidase (TPOab), thyrotropin receptor (TRab) and of impaired fasting glucose (IFG) was found compared to 116 F and 107 M from background pollution area (BCGR). In F and M from POLL also strikingly increased level of PCBs, DDE and HCB was found. Such findings were compared to the generation of their parents aged 41-55 years consisting of 320F/213M from POLL and 406F/231M from BCGR. However, in spite of strikingly lower level of those OCs in young adults from POLL, they showed about the same prevalence of adverse health signs as the old generation. From such reason 44 young F and 40 young M with lowest PCBs level from POLL were selected to obtain nearly the same PCB level as found in all young F and M from BCGR. In such PCB adjusted groups the prevalence of TPOab, TRab, IFG and increased ThV was still significantly higher than that in all young subjects from BCGR. At the same time, also the level of DDE and HCB in such PCBs adjusted groups was considerably lower. It was concluded that such adverse effects in young adults from POLL possibly did not result from their actual OCs levels, but very likely from their exposure to high OCs levels of their mothers during their prenatal and perinatal life. Thus, the data may be compatible with present views on transgenerational transmission of endocrine disruptors action.

Epidemiologic evidence of relationships between reproductive and child health outcomes and environmental chemical contaminants

This review summarizes the level of epidemiologic evidence for relationships between prenatal and/or early life exposure to environmental chemical contaminants and fetal, child, and adult health. Discussion focuses on fetal loss, intrauterine growth restriction, preterm birth, birth defects, respiratory and other childhood diseases, neuropsychological deficits, premature or delayed sexual maturation, and certain adult cancers linked to fetal or childhood exposures. Environmental exposures considered here include chemical toxicants in air, water, soil/house dust and foods (including human breast milk), and consumer products. Reports reviewed here included original epidemiologic studies (with at least basic descriptions of methods and results), literature reviews, expert group reports, meta-analyses, and pooled analyses. Levels of evidence for causal relationships were categorized as sufficient, limited, or inadequate according to predefined criteria. There was sufficient epidemiological evidence for causal relationships between several adverse pregnancy or child health outcomes and prenatal or childhood exposure to environmental chemical contaminants. These included prenatal high-level methylmercury (CH(3)Hg) exposure (delayed developmental milestones and cognitive, motor, auditory, and visual deficits), high-level prenatal exposure to polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and related toxicants (neonatal tooth abnormalities, cognitive and motor deficits), maternal active smoking (delayed conception, preterm birth, fetal growth deficit [FGD] and sudden infant death syndrome [SIDS]) and prenatal environmental tobacco smoke (ETS) exposure (preterm birth), low-level childhood lead exposure (cognitive deficits and renal tubular damage), high-level childhood CH(3)Hg exposure (visual deficits), high-level childhood exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (chloracne), childhood ETS exposure (SIDS, new-onset asthma, increased asthma severity, lung and middle ear infections, and adult breast and lung cancer), childhood exposure to biomass smoke (lung infections), and childhood exposure to outdoor air pollutants (increased asthma severity). Evidence for some proven relationships came from investigation of relatively small numbers of children with high-dose prenatal or early childhood exposures, e.g., CH(3)Hg poisoning episodes in Japan and Iraq. In contrast, consensus on a causal relationship between incident asthma and ETS exposure came only recently after many studies and prolonged debate. There were many relationships supported by limited epidemiologic evidence, ranging from several studies with fairly consistent findings and evidence of dose-response relationships to those where 20 or more studies provided inconsistent or otherwise less than convincing evidence of an association. The latter included childhood cancer and parental or childhood exposures to pesticides. In most cases, relationships supported by inadequate epidemiologic evidence reflect scarcity of evidence as opposed to strong evidence of no effect. This summary points to three main needs: (1) Where relationships between child health and environmental exposures are supported by sufficient evidence of causal relationships, there is a need for (a) policies and programs to minimize population exposures and (b) population-based biomonitoring to track exposure levels, i.e., through ongoing or periodic surveys with measurements of contaminant levels in blood, urine and other samples. (2) For relationships supported by limited evidence, there is a need for targeted research and policy options ranging from ongoing evaluation of evidence to proactive actions. (3) There is a great need for population-based, multidisciplinary and collaborative research on the many relationships supported by inadequate evidence, as these represent major knowledge gaps. Expert groups faced with evaluating epidemiologic evidence of potential causal relationships repeatedly encounter problems in summarizing the available data. A major driver for undertaking such summaries is the need to compensate for the limited sample sizes of individual epidemiologic studies. Sample size limitations are major obstacles to exploration of prenatal, paternal, and childhood exposures during specific time windows, exposure intensity, exposure-exposure or exposure-gene interactions, and relatively rare health outcomes such as childhood cancer. Such research needs call for investments in research infrastructure, including human resources and methods development (standardized protocols, biomarker research, validated exposure metrics, reference analytic laboratories). These are needed to generate research findings that can be compared and subjected to pooled analyses aimed at knowledge synthesis.

The influence of the environment and other exogenous agents on spontaneous abortion risk

It is estimated that close to 30% of all pregnancies end in spontaneous abortion. Although about 60% of spontaneous abortions are thought to be due to genetic, infectious, hormonal, and immunological factors, the role of the environment remains poorly understood. Pregnancy involves a delicate balance of hormonal and immunological functions, which may be affected by environmental substances. Many toxic substances that are persistent in the environment and accumulate in the fatty tissues may disrupt this equilibrium. This overview addresses known risk factors for spontaneous abortions and examines the role, if any, that environmental factors (chemical and physical) may play in the etiology of this adverse health outcome.

Environmental hazards: evidence for effects on child health

The human fetus, child, and adult may experience adverse health outcomes from parental or childhood exposures to environmental toxicants. The fetus and infant are especially vulnerable to toxicants that disrupt developmental processes during relatively narrow time windows. This review summarizes knowledge of associations between child health and development outcomes and environmental exposures, including lead, methylmercury, polychlorinated biphenyls (PCBs), dioxins and related polyhalogenated aromatic hydrocarbons (PHAHs), certain pesticides, environmental tobacco smoke (ETS), aeroallergens, ambient air toxicants (especially particulate matter [PM] and ozone), chlorination disinfection by-products (DBPs), sunlight, power-frequency magnetic fields, radiofrequency (RF) radiation, residential proximity to hazardous waste disposal sites, and solvents. The adverse health effects linked to such exposures include fetal death, birth defects, being small for gestational age (SGA), preterm birth, clinically overt cognitive, neurologic, and behavioral abnormalities, subtle neuropsychologic deficits, childhood cancer, asthma, other respiratory diseases, and acute poisoning. Some environmental toxicants, notably lead, ionizing radiation, ETS, and certain ambient air toxicants, produce adverse health effects at relatively low exposure levels during fetal or child developmental time windows. For the many associations supported by limited or inadequate epidemiologic evidence, major sources of uncertainty include the limited number of studies conducted on specific exposure-outcome relationships and methodologic limitations. The latter include (1) crude exposure indices, (2) limited range of exposure levels, (3) small sample sizes, and (4) limited knowledge and control of potential confounders. Important knowledge gaps include the role of preconceptual paternal exposures, a topic much less studied than maternal or childhood exposures. Large longitudinal studies beginning before or during early pregnancy are urgently needed to accurately measure and assess the relative importance of parental and childhood exposures and evaluate relatively subtle health outcomes such as neuropsychologic and other functional deficits. Large case-control studies are also needed to assess the role of environmental exposures and their interactions with genetic factors in relatively uncommon outcomes such as specific types of birth defects and childhood cancers. There is also an urgent need to accelerate development and use of biomarkers of exposure and genetic susceptibility in epidemiologic studies. This review supports the priority assigned by international agencies to relationships between child health and air quality (indoor and outdoor), lead, pesticides, water contaminants, and ETS. To adequately address such priorities, governments and agencies must strengthen environmental health research capacities and adopt policies to reduce parental and childhood exposures to proven and emerging environmental threats.

In utero pesticide exposure and childhood morbidity

In humans, immune development begins early in embryonic life and continues throughout the early postnatal period. Although a number of pesticides have been observed to induce developmental immunotoxicity in mice, few human studies have examined the long term effects of in utero pesticide exposure on childhood morbidity. Empirical evidence suggests that the vulnerable period for toxic insults to the developing immune system extends from early gestation to adolescence in humans and animals. Using data from the Ontario Farm Family Health Study, we examined the relationship between farm couple exposures to pesticides during pregnancy and subsequent health outcomes in their offspring, including: persistent cough or bronchitis, asthma, and allergies or hayfever. No strong associations between pesticide exposures during pregnancy and persistent cough or bronchitis, or asthma were found. There was suggestive evidence that allergies and hayfever appeared to be more common in offspring, especially male offspring, exposed to certain specific pesticides during the period of pregnancy. Nevertheless, given the indirect indicators of pesticide exposure used in this study, and the scarcity of human studies on in utero exposure to pesticides and the development of allergies and other child health outcomes, these findings serve primarily to generate hypotheses for future research.

The chemical erosion of human health: adverse environmental exposure and in-utero pollution - determinants of congenital disorders and chronic disease

Epidemiological research designed to explore causality of illness has produced increasing evidence to verify that exposure to toxic agents is contributing to the escalating burden of chronic affliction, including congenital disorders. While endeavoring to facilitate optimal health and well-being for patients, the medical profession is currently challenged by the consequences of environmental factors unique to the modern era. In the last half century, there have been profound shifts in health-related habits of individuals and population groups, and recent research suggests that changes in the home and workplace environment are responsible for many common health problems including various congenital anomalies. As a result of increasing concern about environmental influences on health, 'Human Exposure Assessment,' the investigation and study of specific patient exposures and related health concerns, is a rapidly expanding area of scientific research. Practitioners of clinical medicine, including providers of maternity care, should acquire the skills to elicit a proper environmental exposure history and the necessary tools to implement proactive patient education relating to precautionary avoidance.

Effect of prenatal exposure to polychlorinated biphenyls on incidence of acute respiratory infections in preschool Inuit children

OBJECTIVE

We set out to assess whether environmental prenatal exposure to polychlorinated biphenyls (PCBs) is associated with incidence of acute respiratory infections in preschool Inuit children.

STUDY DESIGN

We reviewed the medical charts of 343 children from 0 to 5 years of age and evaluated the associations between PCB-153 concentration in umbilical cord plasma and the incidence rates of acute otitis media (AOM) and of upper and lower respiratory tract infections (URTIs and LRTIs, respectively).

RESULTS

The incidence rates of AOM and LRTIs were positively associated with prenatal exposure to PCBs. Compared with children in the first quartile of exposure (least exposed), children in fourth quartile (most exposed) had rate ratios of 1.25 (p<0.001) and 1.40 (p<0.001) for AOM and LRTIs, respectively. There was no association between prenatal PCB exposure and incidence rate of URTIs or hospitalization.

CONCLUSION

Prenatal exposure to PCBs could be responsible for a significant portion of respiratory infections in children of this population.

Concentrations of polychlorinated biphenyl congeners in cultivated oysters (Crassostrea gigas) in western Taiwan

Spatial and temporal variations of polychlorinated biphenyl (PCB) concentrations in cultivated oysters from five aquaculture areas along the western coast of Taiwan were investigated. Poor correlations between total PCB concentrations (ng/g dry weight [dw]) and physiologic parameters of oysters (shell length, width, thickness, and lipid content) were found. Total PCB concentrations ranged from 3.4 to 94 cng/g dw. The highest value was found in oysters from the Lu'ermen aquaculture area, which receives wastewater from a sodium hydroxide and pentachlorophenol factory. Furthermore, principal component analysis confirmed that the PCB congener pattern in this area was distinct from others and that two additional pollution sources might exist in the Tainan and Hsinchu areas. Oysters with PCB concentrations > 1 SD above the geometric mean were found mainly in Tainan (stations TN5 to TN9) with only one increased concentration in the Yunlin (station YL2) and Hsinchu (station HC4) aquaculture areas. Except for four confined stations, TN3 to TN6, where total PCB concentrations were higher (p = 0.028) in the warmer (May and July) than in the colder season (November and March), seasonal variation of total PCB concentrations in oysters was not significant. Geometric mean and geometric mean plus 1 SD of total PCB concentrations in this study are lower than those in South Korea and the United States (Mussel Watch).

Aroclor 1254 impairs the hearing ability of Xenopus laevis

In this study we assessed the effects of chronic, dietary exposure of Aroclor 1254 (A1254) on the hearing of Xenopus frogs. We used the auditory brainstem response (ABR) to assay changes in hearing physiology; ABR thresholds, as well as latency-intensity and amplitude-intensity profiles of the initial positive (P1) and negative (N1) peaks were measured. Two groups of animals that received 50 ppm and 100 ppm of A1254 in their diet from 5 days post-fertilization through metamorphosis were compared to a control group that received untreated chow. The results showed significant threshold elevations in the 3-4 kHz range and significantly delayed peak latencies and reduced amplitudes at these frequencies in A1254 treated animals as compared to control animals. These findings indicate that A1254 selectively damages the high-frequency sensorineural hearing system associated with the basilar papilla of frogs. This preferential damage may be related to inherent differences in the vulnerability of the basilar versus amphibian papilla in the frog. The overall results of this study are also consistent with the reported A1254-induced auditory deficits in mammals indicating that the basilar papilla of the Xenopus frog may serve as an effective model for studying the effects of A1254 on the auditory system.

Overview of exposure, toxicity, and risks to children from current levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds in the USA

Studies of children indicate that exposure of the general population to low levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) does not result in any clinical evidence of disease, although accidental exposure to high levels either before or after birth have led to a number of developmental deficits. Breast-fed infants have higher exposures than formula-fed infants, but studies consistently find that breast-fed infants perform better on developmental neurologic tests than their formula-fed counterparts, supporting the well-recognized benefits of breast feeding. Children receive higher exposures to PCDD/Fs from food than adults on a body-weight basis but those exposures are below the World Health Organization's tolerable daily intake. Laboratory rodents appear to be at least an order of magnitude more sensitive than humans to the aryl hydrocarbon receptor-mediated effects of these substances, which makes them poor surrogates for predicting quantitative risks but makes them good models for establishing safe levels of human exposure by organizations mandated to protect public health. Any exposure limit for PCDD/Fs based on developmental toxicity in sensitive laboratory animals can be expected to be especially protective of human health, including the health of infants and children. Because body burdens and environmental levels continue to decline, it is unlikely that children alive today in the USA will experience exposures to PCDD/Fs that are injurious to their health.

A dose-response study of the effects of prenatal and lactational exposure to TCDD on the immune response to influenza a virus

The goal of the current study was to evaluate the immune response to a common respiratory pathogen, influenza A virus, in mice exposed to increasing doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during development. Additionally, the treatment paradigm was designed to provide exposure throughout fetal and neonatal development, beginning on d 1 of gestation. To accomplish this, impregnated C57Bl/6 mice were treated with 0.25 microg/kg TCDD on d 0 and 7 of pregnancy, followed by 2 additional doses of 0.25, 1, or 5 microg/kg given on d 14 and postpartum d 2. The adult offspring were infected with influenza virus, and components of the adaptive and innate immune responses were evaluated. Our results show that developmental exposure to TCDD dose-responsively suppressed both the cell-mediated and antibody responses to influenza virus in female but not males. In contrast, TCDD exposure enhanced the innate immune responses in offspring of both sexes; specifically, neutrophilia and interferon (IFN) gamma levels in the lung were increased. These alterations in functional immunity did not result from overt toxicity to the immune organs, as developmental TCDD exposure did not alter the cellular composition of the thymus, spleen, or bone marrow. These findings extend our knowledge of the dose-responsive nature of immunological defects induced by developmental exposure to TCDD and offer insight regarding the dose required to alter the immune response to viral infection. Moreover, we demonstrate a clear dose at which no observable effects on immune function later in life were detected.

Human health implications of environmental contaminants in Arctic Canada: A review

The objectives of this paper are to: assess the impact of exposure to current levels of environmental contaminants in the Canadian Arctic on human health; identify the data and knowledge gaps that need to be filled by future human health research and monitoring; examine how these issues have changed since our first assessment [Van Oostdam, J., Gilman, A., Dewailly, E., Usher, P., Wheatley, B., Kuhnlein, H. et al., 1999. Human health implications of environmental contaminants in Arctic Canada: a review. Sci Total Environ 230, 1-82]. The primary exposure pathway for contaminants for various organochlorines (OCs) and toxic metals is through the traditional northern diet. Exposures tend to be higher in the eastern than the western Canadian Arctic. In recent dietary surveys among five Inuit regions, mean intakes by 20- to 40-year-old adults in Baffin, Kivalliq and Inuvialuit communities exceeded the provisional tolerable daily intakes (pTDIs) for the OCs, chlordane and toxaphene. The most recent findings in NWT and Nunavut indicate that almost half of the blood samples from Inuit mothers exceeded the level of concern value of 5 microg/L for PCBs, but none exceeded the action level of 100 microg/L. For Dene/Métis and Caucasians of the Northwest Territories exposure to OCs are mostly below this level of concern. Based on the exceedances of the pTDI and of various blood guidelines, mercury and to a lesser extent lead (from the use of lead shot in hunting game) are also concerns among Arctic peoples. The developing foetus is likely to be more sensitive to the effects of OCs and metals than adults, and is the age groups of greatest risk in the Arctic. Studies of infant development in Nunavik have linked deficits in immune function, an increase in childhood respiratory infections and birth weight to prenatal exposure to OCs. Balancing the risks and benefits of a diet of country foods is very difficult. The nutritional benefits of country food and its contribution to the total diet are substantial. Country food contributes significantly more protein, iron and zinc to the diets of consumers than southern/market foods. The increase in obesity, diabetes and cardiovascular disease has been linked to a shift away from a country food diet and a less active lifestyle. These foods are an integral component of good health among Aboriginal peoples. The social, cultural, spiritual, nutritional and economic benefits of these foods must be considered in concert with the risks of exposure to environmental contaminants through their exposure. Consequently, the contamination of country food raises problems which go far beyond the usual confines of public health and cannot be resolved simply by risk-based health advisories or food substitutions alone. All decisions should involve the community and consider many aspects of socio-cultural stability to arrive at a decision that will be the most protective and least detrimental to the communities.

Non-coplanar PCB-mediated modulation of human leukocyte phagocytosis: a new mechanism for immunotoxicity

Organochlorine (OC) contaminants, notably polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are ubiquitous in all ecosystems and found in the tissues of humans and wildlife. Although the immunotoxicity of coplanar, dioxinlike PCBs is well documented, the adverse effects exerted by non-coplanar, non-dioxinlike PCBs have received little attention. Direct causal relationship between PCB and dioxin exposure and the observed detrimental effects on the immune system has yet to be fully established in humans. The immunomodulatory potential of toxic coplanar PCB 169 and TCDD and abundant non-coplanar PCBs 138, 153, and 180 on human leukocyte phagocytosis, an important innate immune function that initiates the clearance of pathogens, was tested upon in vitro exposure. Mixture and concentration-response experiments demonstrated a suppression of phagocytosis by non-coplanar PCBs suggesting a previously unrecognized aryl hydrocarbon receptor (AhR)-independent pathway. Regression analysis revealed that reduction of phagocytosis was mostly explained by the non-coplanar congeners. The effects on phagocytosis could not be accurately predicted by either the currently used toxic equivalence (TEQ) approach or the mouse model, thus undermining the use of the traditional models in the risk assessment for OC mixtures containing non-coplanar congeners. Our results are cause for concern as they suggest an AhR-independent pathway through which non-coplanar PCBs modulate phagocytosis, the immune system's first line of defense, possibly increasing the risk to developing infectious disease.

Serum hormones in boys prenatally exposed to polychlorinated biphenyls and dibenzofurans

Polychlorinated biphenyls (PCBs) and dibenzofurans (PCDFs) are persistent environmental pollutants shown to adversely interact with several functions of the endocrine system. In 1978-1979, over 2000 Taiwanese people ingested rice oil accidentally contaminated with PCBs and PCDFs. This is one of the major toxic exposure episodes that occurred globally and was later called Yucheng (oil disease in Chinese). The children born to exposed Yucheng women were therefore exposed in utero to high doses of PCBs/PCDFs. In 1995, 60 Yucheng and 61 control boys participated in physical examination, and serum hormones were measured by radioimmunoassay (RIA). Age, body weight, body height, Tanner status, testicular size, serum luteinizing hormone (LH), prolactin (PRL), thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH) levels were not statistically different between Yucheng and control boys in the subgroups of before and at the age of puberty. However, the serum estradiol (E2) levels were significant higher in Yucheng boys at the age of puberty. Yucheng and control boys were further divided into two subgroups, those before (age <13 yr) and those at the age of puberty (age > or = 13 yr). There was a decrease of serum testosterone (TT) levels and increase of serum follicle-stimulating hormone (FSH) levels in Yucheng boys at the age of puberty as compared with controls. There was a significant decrease of the square root of TT/E2 and TT/FSH; however, the square root of E2/FSH was increased in Yucheng boys at the age of puberty as compared with controls. Data indicated that prenatal exposure to PCBs and PCDFs may have implications for boys' sex hormone homeostasis at puberty. Further studies are needed to identify the congeners of PCBs/PCDFs responsible for disruption of the endocrine system, as well as the mechanisms of such disruption.

Serum concentrations and profiles of polychlorinated biphenyls in Taiwan Yu-cheng victims twenty years after the incident

In 1979, about 2000 people in central Taiwan were intoxicated via rice oil consumption that was contaminated with polychlorinated biphenyls (PCBs). This "Yu-cheng" incident was one of the two known major human PCB intoxication episodes. Twenty years after the intoxication, serum samples of 435 Yu-cheng victims, 414 adults and 21 children, were collected. Sixteen PCB congeners were analyzed with a gas chromatograph-electron capture detector. We found the median concentration of total PCBs in the adult serum was 1500 ng/g lipid, still substantially higher than that of the general population in Taiwan (3.7-fold) and most seafood consumers in the world. Most of analyzed PCB congeners in children were below or around the detection limits. Congener #138, however, had the highest concentrations, approximately accounting for 55% and 29% in the child and adult groups, respectively. Given that PCBs are persistent organic pollutants and endocrine disruptors, the concentrations and congener-specific profiles regarding the Yu-cheng victims provide valuable information for the investigation of such chemicals in humans.

Does high organochlorine (OC) exposure impair the resistance to infection in polar bears (Ursus maritimus)? Part II: Possible effect of OCs on mitogen- and antigen-induced lymphocyte proliferation

Previous studies have reported alarmingly high levels of organochlorines (OCs), particularly polychlorinated biphenyls (PCBs), in free-ranging polar bears (Ursus maritimus). In this study plasma concentration of PCBs ranged from 14.8 to 200 ng/g wet weight. The aim of the study was to investigate associations between OCs and lymphocyte proliferation after in vitro stimulation with different mitogens and antigens. In 1998 and 1999, 26 and 30 free-ranging polar bears from Svalbard and Churchill, Canada, respectively, were recaptured 32-40 d following immunization with inactivated tetanus toxoid and hemocyanin from keyhole limpets (KLH) to sensitize lymphocytes. At recapture, blood was sampled for determination of plasma levels of PCBs and organochlorine pesticides (OCPs) and lymphocyte proliferation after in vitro stimulation with specific mitogens--phytohemagglutinin (PHA), pokeweed mitogen (PWM), concanavalin A (Con A), lipopolysaccharide (LPS), and purified protein derivative of Mycobacterium avium subsp. paratuberculosis (PPD)--and antigens: tetanus toxoid and KLH. The combinations of sum(PCBs) (sum of 12 individual PCB congeners), sum(OCPs) (sum of 6 OCPs), and their interactions contributed up to 15% of the variations in the lymphocyte responses. By using multiple regression analyses, followed by classical mathematic function analyses, thresholds for immunomodulation were estimated. Depending on the lymphocyte proliferation response studied, the estimated thresholds for significant immunomodulation were within the concentration ranges 32-89 ng/g wet weight (ww) and 7.8-14 ng/g ww for sum(PCBs) and sum(OCPs), respectively. Thus, this study demonstrated that OC exposure significantly influences specific lymphocyte proliferation responses and part of the cell-mediated immunity, which also is associated with impaired ability to produce antibodies (Lie et al., 2004).

In utero exposure to polychlorinated biphenyls and sensorineural hearing loss in 8-year-old children

Early-life exposure to polychlorinated biphenyls (PCBs), a ubiquitous environmental contaminant, increases the hearing threshold at selected frequencies in rats. Among humans from the Faroe Islands with unusually high early-life PCB exposure, exposure was directly associated with increased hearing thresholds at two frequencies, although the deficits were present in the left ear but not the right. We examined PCB levels in maternal pregnancy serum in relation with audiometrically determined hearing thresholds among offspring when they were of school age. Complete data were available for 195 children with sensorineural hearing loss (SNHL) and 615 children selected at random, all of whom were born in 1959-1966 in the Collaborative Perinatal Project (CPP) U.S. cohort. The median exposure among those selected at random, as reflected by the mother's third trimester serum total PCB concentration, was 2.8 microg/l, about twofold higher than recent background levels in the United States. Based on the average hearing threshold across the frequencies essential for speech recognition in the "worst ear," the maternal serum PCB level was unrelated to the adjusted odds of SNHL or to adjusted mean hearing threshold. Overall, an adverse effect of early-life, background-level PCB exposure on SNHL was not supported by these data.

Specific non-coplanar PCB-mediated modulation of bottlenose dolphin and beluga whale phagocytosis upon in vitro exposure

Contaminant-induced immunosuppression by organochlorines (OC), particularly polychlorinated biphenyls (PCBs), has been suspected as a cofactor in the deaths of thousands of marine mammals. One important innate defense mechanism is phagocytosis, the ability of cells to ingest extracellular macromolecules. The present study was aimed at characterizing the immunomodulatory potential of representative OCs on phagocytosis in bottlenose dolphins and beluga whales. The ability of peripheral blood leukocytes to engulf fluorescent microspheres was evaluated using flow cytometry. The immunomodulatory effects of three non-coplanar PCB congeners, 138, 153, and 180, one coplanar PCB, 169, and 2,3,7,8-TCDD and all possible mixtures (26) were tested upon in vitro exposure. In both species, all mixtures containing at least two non-coplanar PCBs significantly reduced both neutrophil and monocyte phagocytosis, with effects more marked in dolphins than in belugas. Coplanar OCs, on their own or when added to non-coplanar congeners, did not further modulate phagocytosis, suggesting an Ah receptor-independent mechanism. Concentration-response experiments with individual congeners further demonstrated a non-coplanar PCB-induced suppression of phagocytosis, while coplanar congeners produced no consistent effects. Our results suggest simple additive interactions of chemicals in a mixture. However, calculation of toxic equivalency (TEQs) failed to predict the experimentally induced immunomodulatory effects of OCs on dolphin and beluga phagocytosis, confirming the Ah receptor-independent nature of the effects on phagocytosis. Overall, our results suggest that non-AhR mechanisms may explain one facet of immunotoxicity (phagocytosis), something that is not captured using the TEQ approach. This is the first report demonstrating the immunomodulatory effects of OCs on dolphin and beluga phagocytosis, and the first overall demonstration of immunomodulatory effects on phagocytosis mediated specifically by non-coplanar PCBs.

Acute infections and environmental exposure to organochlorines in Inuit infants from Nunavik

The Inuit population of Nunavik (Canada) is exposed to immunotoxic organochlorines (OCs) mainly through the consumption of fish and marine mammal fat. We investigated the effect of perinatal exposure to polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE) on the incidence of acute infections in Inuit infants. We reviewed the medical charts of a cohort of 199 Inuit infants during the first 12 months of life and evaluated the incidence rates of upper and lower respiratory tract infections (URTI and LRTIs, respectively), otitis media, and gastrointestinal (GI) infections. Maternal plasma during delivery and infant plasma at 7 months of age were sampled and assayed for PCBs and DDE. Compared to rates for infants in the first quartile of exposure to PCBs (least exposed), adjusted rate ratios for infants in higher quartiles ranged between 1.09 and 1.32 for URTIs, 0.99 and 1.39 for otitis, 1.52 and 1.89 for GI infections, and 1.16 and 1.68 for LRTIs during the first 6 months of follow-up. For all infections combined, the rate ratios ranged from 1.17 to 1.27. The effect size was similar for DDE exposure but was lower for the full 12-month follow-up. Globally, most rate ratios were > 1.0, but few were statistically significant (p < 0.05). No association was found when postnatal exposure was considered. These results show a possible association between prenatal exposure to OCs and acute infections early in life in this Inuit population.

Cord blood lymphocyte functions in newborns from a remote maritime population exposed to organochlorines and methylmercury

The consumption of fish and sea mammals can be an important source of exposure to organochlorine compounds (OCs) and heavy metals in populations relying on seafood for subsistence. Exposure to these substances, especially during the prenatal period, has been shown to induce immunotoxic effects in mammals. Immunological status was assessed in 48 newborns from a remote maritime population living on the Lower and Mid North Shore of the St. Lawrence River (subsistence fishing group) and 60 newborns from the coastal urban center of Sept-Iles (reference group). Women were recruited upon arrival at Sept-Iles regional hospital to give birth. Cord blood samples were collected for organochlorine and heavy metal analyses and to isolate lymphocytes for immunological assays (proportions and functional responses of the main cellular subsets T, B, and NK (natural killer) cells. Concentrations of polychlorinated biphenyls (PCBs) and mercury were respectively three- and twofold higher, significantly greater, in the subsistence fishing group than in the reference group. Compared to the reference group, the subsistence fishing group showed significant decreases in the proportion of the naive helper T-cell subset CD4+CD45RA, T-cell proliferation following an in vitro mitogenic stimulation, and plasma immunoglobulin M (IgM) level, while plasma IgC level was increased. NK cytolytic activities were similar in both groups. The proportion of CD4+CD45RA cells was inversely correlated to mercury and PCBs, while T-cell clonal expansion was negatively associated with PCBs and p,p'-DDE. Mercury was inversely correlated to plasma IgM. Data show that subtle functional alterations of the developing human immune system may result from in utero exposure to OCs and mercury. Epidemiological studies are needed to determine the relevance of these alterations in predicting detrimental health effects in the developing child.

Polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans and birth weight and immune and thyroid function in children

None of the publications reviewed provide clinical evidence that PCBs (polychlorinated biphenyls) and related chemicals adversely affect weight, immune, or thyroid function in infants or children born to healthy mothers. Birth weights of term infants fell within the normal range in all studies. The greatest difference between comparison groups was reported by G. G. Fein et al. (1984a, Intrauterine Exposure of Humans to PCBs: Newborn Effects, EPA-600/3-84-060, Environmental Protection Agency; 1984b, J. Pediatr. 105, 315-320). P. R. Taylor et al. (1989, Am. J. Epidemiol. 129, 395-406) reported smaller differences in occupationally exposed women and E. Dar et al. (1992, Environ. Res. 59, 189-201) found that women with higher PCB serum levels had larger babies. S. Patandin et al. (1998, Pediatr Res. 44, 538-545) found a negative association of PCB concentrations in maternal or cord plasma and birth weight of breast and formula-fed infants combined but not when breast-fed infants were analyzed separately. L. Rylander et al. (1995, Scand. J. Work Environ. Health 21, 368-375) reported decreased birth weights with higher dietary intake of contaminated fish. Thus, correlations between PCB exposure or polluted fish ingestion and birth weight were inconsistent. Thyroid and immune function were also within the normal range. In none of the papers were normal laboratory reference values provided and overall the statistically significant differences accounted for little of the variance.

The immunologic evaluation of the Yucheng children

The immunologic effects of in utero exposure to polychlorinated biphenyls (PCBs)/polychlorinated dibenzofurans (PCDFs) were evaluated in the Yucheng children in this study. The study subjects consisted of 105 Yucheng children and 101 control children. The Yucheng children were born, between July 1978 and June 1987, to women who had exposed to high dose of PCBs/PCDFs through consumption of contaminated rice bran oil in 1978-1979. These children had been reported to have higher frequencies of bronchitis than their controls in the first six months of life, and higher frequencies of respiratory tract and ear infection in a 6-year follow-up. The low resistance of the Yucheng children to infection suggested that their immune function was suppressed by the PCBs/PCDFs they had exposed to in utero. In the summer and fall of 1995, a thorough physical examination and blood draw were performed on the study children. The Yucheng children were reported by their parents to have higher frequencies of influenza attacks than the control children during the six months prior to the examination. The frequencies of other symptoms were similar between the two groups. The serum levels of various immunoglobulins were similar between the two groups. Fifty-one serum samples, 29 of Yucheng and 22 of control children, were available for cell-mediated immunologic analysis. The percentages of various T cell markers, CD3, CD4, and CD8, and B cell and NK cell markers were not different between the Yucheng and the control children. No dose-response relationship was found between 27 Yucheng children's serum PCB/PCDF levels and any of their immunologic markers. WE concluded that 16 years after the Yucheng incident, Yucheng children exposed to high dose of PCBs/PCDFs in utero did not show, with the serum immunologic marker analyses, suppressed immunity when compared to their controls. To explain the consistent higher frequencies of upper respiratory tract infection in the Yucheng children, immune functional tests such as delayed hypersensitive skin reaction, in vitro lymphocyte proliferation, and antibody synthesis following immunization may be necessary.

Effects of environmental synthetic chemicals on thyroid function

Synthetic chemicals are released into the environment by design (pesticides) or as a result of industrial activity. It is well known that natural environmental chemicals can cause goiter or thyroid imbalance. However, the effects of synthetic chemicals on thyroid function have received little attention, and there is much controversy over their potential clinical impact, because few studies have been conducted in humans. This article reviews the literature on possible thyroid disruption in wildlife, humans, and experimental animals and focuses on the most studied chemicals: the pesticides DDT, amitrole, and the thiocarbamate family, including ethylenethiourea, and the industrial chemicals polyhalogenated hydrocarbons, phenol derivatives, and phthalates. Wildlife observations in polluted areas clearly demonstrate a significant incidence of goiter and/or thyroid imbalance in several species. Experimental evidence in rodents, fish, and primates confirms the potentiality for thyroid disruption of several chemicals and illustrates the mechanisms involved. In adult humans, however, exposure to background levels of chemicals does not seem to have a significant negative effect on thyroid function, while exposure at higher levels, occupational or accidental, may produce mild thyroid changes. The impact of transgenerational, background exposure in utero on fetal neurodevelopment and later childhood cognitive function is now under scrutiny. There are several studies linking a lack of optimal neurological function in infants and children with high background levels of exposure to polychlorinated biphenyls (PCBs), dioxins, and/or co-contaminants, but it is unclear if the effects are caused by thyroid disruption in utero or direct neurotoxicity.