Prenatal exposures to persistent and non-persistent organic compounds and effects on immune system development

Air pollution and allergic disease

Over the past several decades, there has been increased awareness of the health effects of air pollution and much debate regarding the role of global warming. The prevalence of asthma and allergic disease has risen in industrialized countries, and most epidemiologic studies focus on possible causalities between air pollution and these conditions. This review examines salient articles and summarizes findings important to the interaction between allergies and air pollution, specifically volatile organic compounds, global warming, particulate pollutants, atopic risk, indoor air pollution, and prenatal exposure. Further work is necessary to determine whether patients predisposed to developing allergic disease may be more susceptible to the health effects of air pollutants due to the direct interaction between IgE-mediated disease and air pollutants. Until we have more definitive answers, patient education about the importance of good indoor air quality in the home and workplace is essential. Health care providers and the general community should also support public policy designed to improve outdoor air quality by developing programs that provide incentives for industry to comply with controlling pollution emissions.

Moving towards making social toxins mainstream in children's environmental health

PURPOSE OF REVIEW

Although traditional disciplinary research theory and methods have focused separately on how social and physical environmental factors affect children's health, evolving research underscores important integrated effects.

RECENT FINDINGS

This review outlines the specific reasons why social determinants should be considered mainstream in children's environmental health research with particular focus on interactive effects between social and physical hazards. These include sensitivity of overlapping physiological systems, via epigenesis, programming, and plasticity to social and physical environmental moderation that may impact health across the life span; ways in which social environmental vulnerabilities moderate the effects of physical environmental factors, providing specific examples related to respiratory health and neurodevelopment; overlapping exposure distribution profiles; and relevance to pediatric health disparities.

SUMMARY

Because of the covariance across exposures, and evidence that social stress and other environmental toxins (e.g., pollutants, tobacco smoke) may influence common physiological pathways (e.g., oxidative stress, proinflammatory immune pathways, autonomic disruption), understanding the potential synergistic effects promises to more completely inform children's environmental health risk. Although this discussion focuses around the respiratory and neurological systems, these concepts extend more broadly to children's psychological and physical development.

Developmental immunotoxicology: focus on health risks

Developmental immunotoxicity (DIT) has gained attention with the recognition that many chronic diseases of increasing incidence feature immune dysfunction as a component of the disease. The maturing immune system represents a vulnerable target for toxicants as it progresses through a series of novel prenatal and perinatal events that are critical for later-life host defense against a wide array of diseases. These critical maturational windows display a particular sensitivity to chemical disruption with the outcome usually taking the form of persistent immune dysfunction and/or misregulation. For this reason, health risks are significantly increased following early life vs adult immunotoxic exposure. Additionally, DIT-associated health risks are not readily predicted when based on adult-exposure safety data or via the evaluation of an unchallenged immune system in developmental toxicity testing. The same toxicant [e.g., heavy metals, 2,3,7,8-tetraclorodibenzo-p-dioxin (TCDD)] may disrupt different immune maturational processes depending upon the specific developmental timing of exposure and the target organ dose at a given stage of development. Therefore, a single toxicant may promote different immune-associated diseases that are dependent upon the specific window of early life exposure, the gender of the exposed offspring, and the genetic background of the offspring. This perspective considers the linkage between early life chemical exposure, DIT, and the postnatal immune dysfunctions associated with a variety of childhood and adult diseases. Because DIT is linked to a majority of the most significant childhood chronic diseases, safety testing for DIT is a pivotal issue in the protection of children's health.

Early-life environment, developmental immunotoxicology, and the risk of pediatric allergic disease including asthma

Incidence of childhood allergic disease including asthma (AD-A) has risen since the mid-20th century with much of the increase linked to changes in environment affecting the immune system. Childhood allergy is an early life disease where predisposing environmental exposures, sensitization, and onset of symptoms all occur before adulthood. Predisposition toward allergic disease (AD) is among the constellation of adverse outcomes following developmental immunotoxicity (DIT; problematic exposure of the developing immune system to xenobiotics and physical environmental factors). Because novel immune maturation events occur in early life, and the pregnancy state itself imposes certain restrictions on immune functional development, the period from mid-gestation until 2 years after birth is one of particular concern relative to DIT and AD-A. Several prenatal-perinatal risk factors have been identified as contributing to a DIT-mediated immune dysfunction and increased risk of AD. These include maternal smoking, environmental tobacco smoke, diesel exhaust and traffic-related particles, heavy metals, antibiotics, environmental estrogens and other endocrine disruptors, and alcohol. Diet and microbial exposure also significantly influence immune maturation and risk of allergy. This review considers (1) the critical developmental windows of vulnerability for the immune system that appear to be targets for risk of AD, (2) a model in which the immune system of the DIT-affected infant exhibits immune dysfunction skewed toward AD, and (3) the lack of allergy-relevant safety testing of drugs and chemicals that could identify DIT hazards and minimize problematic exposure of pregnant women and children.

Environmental hazards education for childbirth educators

The purpose of this article is to educate childbirth educators about environmental hazards and provide resources. Hazardous chemicals have been found in cord blood, placenta, meconium, and breastmilk samples. These chemicals include commonly known hazards such as lead, mercury, and environmental tobacco smoke, as well as some pesticides, solvents, products containing chlorine, and other chemicals referred to as "persistent organic pollutants." The fetus is particularly vulnerable to environmental chemicals that can disrupt the developmental process at critical times during gestation. Childbirth educators are encouraged to inform themselves in order to inform childbearing families to take preventive action and explore alternative behaviors to reduce exposure to environmental hazards.

The toxic effects of multiple persistent organic pollutant exposures on the post-hatch immunity maturation of glaucous gulls

This study tested whether the immune system of the glaucous gull (Larus hyperboreus) chicks became affected by existing environmental contaminants. An experimental group was given food that mimicked the natural contaminant mixture found in food from the North Atlantic marine environment, while the control group was given the equivalent of nearly clean food. All chicks were immunized with herpes virus (EHV), reovirus (REO), influenza virus (EIV), and tetanus toxoid (TET) in order to test their ability to respond to foreign specific antigens. At 8 wk, the experimental group had 3- to 13-fold higher concentrations of hexachlorobenzene (HCB), oxychlordane, p,p'-DDE, and total polychlorinated biphenyls (Sigma PCB) than did the control. The experimental group produced significantly lower antibody titer against EIV and had lower concentrations of immunoglobulin-G (IgG) and -M (IgM) in blood. Hematocrit percent and leukocyte numbers did not differ between the two groups. The ability of lymphocytes to proliferate in vitro was tested with three mitogens, phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM), and three antigens, keyhole limpet hemocyanin (KLH), TET, and Mycobacterium avium subsp. paratuberculosis tuberculin purified protein derivative (PPD). The experimental group had a significantly higher peripheral blood lymphocyte response to PHA and to spleen lymphocytes in vitro stimulated with Con A and PCB congeners 99 or 153, while the Con A, PWM, KLH, TET, PPD, and Con A plus PCB-156 or -126 showed nonsignificant differences between groups. Data indicate that the combined effect of multiple persistent organic pollution exposures occurring naturally in the Arctic negatively affect the immune system of the glaucous gull chick.

Allergies and childhood leukemia

A majority of studies to date have reported an inversed association between allergies and childhood leukemia. However, this association is likely an indirect one and may represent some shared underlying immune mechanisms that have been explained in the context of the "hygiene hypothesis", which has been thought to play an important role in the development of both allergies and childhood leukemia. This review focuses on what we know so far about the role of various immune cells (Th1, Th2, T regulatory and Th17 cells) in the development of allergies and how they may potentially be related to the etiology of childhood leukemia. In addition, the utilities of genetic and molecular studies to disentangle the association between allergies and childhood leukemia and to elucidate the biological mechanisms are also discussed.

Facing the challenge of data transfer from animal models to humans: the case of persistent organohalogens

A well-documented fact for a group of persistent, bioaccumulating organohalogens contaminants, namely polychlorinated biphenyls (PCBs), is that appropriate regulation was delayed, on average, up to 50 years. Some of the delay may be attributed to the fact that the science of toxicology was in its infancy when PCBs were introduced in 1920's. Nevertheless, even following the development of modern toxicology this story repeats itself 45 years later with polybrominated diphenyl ethers (PBDEs) another compound of concern for public health. The question is why? One possible explanation may be the low coherence between experimental studies of toxic effects in animal models and human studies. To explore this further, we reviewed a total of 807 PubMed abstracts and full texts reporting studies of toxic effects of PCB and PBDE in animal models. Our analysis documents that human epidemiological studies of PBDE stand to gain little from animal studies due to the following: 1) the significant delay between the commercialisation of a substance and studies with animal models; 2) experimental exposure levels in animals are several orders of magnitude higher than exposures in the general human population; 3) the limited set of evidence-based endocrine endpoints; 4) the traditional testing sequence (adult animals--neonates--foetuses) postpones investigation of the critical developmental stages; 5) limited number of animal species with human-like toxicokinetics, physiology of development and pregnancy; 6) lack of suitable experimental outcomes for the purpose of epidemiological studies. Our comparison of published PCB and PBDE studies underscore an important shortcoming: history has, unfortunately, repeated itself. Broadening the crosstalk between the various branches of toxicology should therefore accelerate accumulation of data to enable timely and appropriate regulatory action.

Potential for early-life immune insult including developmental immunotoxicity in autism and autism spectrum disorders: focus on critical windows of immune vulnerability

Early-life immune insults (ELII) including xenobiotic-induced developmental immunotoxicity (DIT) are important factors in childhood and adult chronic diseases. However, prenatal and perinatal environmentally induced immune alterations have yet to be considered in depth in the context of autism and autism spectrum disorders (ASDs). Numerous factors produce early-life-induced immune dysfunction in offspring, including exposure to xenobiotics, maternal infections, and other prenatal-neonatal stressors. Early life sensitivity to ELII, including DIT, results from the heightened vulnerability of the developing immune system to disruption and the serious nature of the adverse outcomes arising after disruption of one-time immune maturational events. The resulting health risks extend beyond infectious diseases, cancer, allergy, and autoimmunity to include pathologies of the neurological, reproductive, and endocrine systems. Because these changes may include misregulation of resident inflammatory myelomonocytic cells in tissues such as the brain, they are a potential concern in cases of prenatal-neonatal brain pathologies and neurobehavioral deficits. Autism and ASDs are chronic developmental neurobehavioral disorders that are on the rise in the United States with prenatal and perinatal environmental factors suspected as contributors to this increase. Evidence for an association between environmentally associated childhood immune dysfunction and ASDs suggests that ELII and DIT may contribute to these conditions. However, it is not known if this linkage is directly associated with the brain pathologies or represents a separate (or secondary) outcome. This review considers the known features of ELII and DIT and how they may provide important clues to prenatal brain inflammation and the risk of autism and ASDs.