"Beginning with the Smallest Intake": Children's Brain Development and the Role of Neuroscience in Global Environmental Health

Ammunition Waste Pollution and Preliminary Assessment of Risks to Child Health from Toxic Metals at the Greek Refugee Camp Mavrovouni

The Mavrovouni refugee camp near the former Moria camp on the island of Lesvos, Greece, housed approximately 3000 asylum-seekers including children as of October 2021. The camp was built on the site of a military shooting range. This study aimed to characterize the soil contaminants and assess the risk of toxic environmental exposures for children living in Mavrovouni. Methods: Samples of surface soil (0−2 cm depth; particle size < 2 mm) from eight locations inside the camp were compared with two reference samples. Soil samples were microwave digested using a mixture of nitric and hydrofluoric acids and analyzed for lead (Pb), antimony (Sb), bismuth (Bi), and other metals using inductively coupled plasma mass spectrometry. These values were compared with action limits established by the Norwegian Environment Agency for kindergartens, playgrounds, and schools. Findings: Five of eight soil samples from inside the camp exceeded Pb levels of 100 mg/kg, which is currently the maximum acceptable value of Pb in soil for playgrounds in Norway. Two sites had extreme soil Pb levels of approximately 8000 mg/kg and 6000 mg/kg. The concen-tration of Sb and Bi in the surface soil of the firing range area strongly indicated environmental contamination, most likely from previous military activity and ammunition residue that has re-mained on the surface soil. Concentrations of arsenic (As), cadmium (Cd), copper (Cu), and zinc (Zn) in surface soil were lower than action limits. Discussion: Extremely high levels of Pb, together with high levels of Sb and Bi, were identified in soil where children live and play in the Mavrovouni refugee camp. This is the first independent study of environmental contamination at this camp and adds to the limited evidence base documenting Pb exposures prior to migrant and refugee reset-tlement. On top of the multiple existing public health crises and traumas that these asylum-seeking families face, exposure to toxic ammunition residues may have profound impacts on children’s development and health for years to come.

Maternal Blood Levels of Toxic and Essential Elements and Birth Outcomes in Argentina: The EMASAR Study

Pregnant women’s levels of toxic and essential minerals have been linked to birth outcomes yet have not been adequately investigated in South America. In Argentina, n = 696 maternal whole blood samples from Ushuaia (n = 198) and Salta (n = 498) were collected in 2011–2012 among singleton women at 36 ± 12 h postpartum and analyzed for blood concentrations of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), copper (Cu), manganese (Mn), selenium (Se) and zinc (Zn). This study examined the associations between maternal elements levels and birth outcomes, and sociodemographic factors contributing to elements levels. Maternal age, parity, body mass index, smoking, and education were linked to concentrations of some but not all elements. In adjusted models, one ln-unit increase in Pb levels was associated with increased gestational age (0.2 weeks, 95% CI = 0.01–0.48) and decreased birth weight (−88.90 g, 95% CI = −173.69 to −4.11) and birth length (−0.46 cm, 95% CI = −0.85 to −0.08) in the Salta sample. Toxic elements concentrations were not associated with birth outcomes in Ushuaia participants. Birth outcomes are multifactorial problems, and these findings provide a foundation for understanding how the body burden of toxic and essential elements, within the socioeconomic context, may influence birth outcomes.

Atmospheric particulate matter aggravates CNS demyelination through involvement of TLR-4/NF-kB signaling and microglial activation

Atmospheric Particulate Matter (PM) is one of the leading environmental risk factors for the global burden of disease. Increasing epidemiological studies demonstrated that PM plays a significant role in CNS demyelinating disorders; however, there is no direct testimony of this, and yet the molecular mechanism by which the occurrence remains unclear. Using multiple in vivo and in vitro strategies, in the present study we demonstrate that PM exposure aggravates neuroinflammation, myelin injury, and dysfunction of movement coordination ability via boosting microglial pro-inflammatory activities, in both the pathological demyelination and physiological myelinogenesis animal models. Indeed, pharmacological disturbance combined with RNA-seq and ChIP-seq suggests that TLR-4/NF-kB signaling mediated a core network of genes that control PM-triggered microglia pathogenicity. In summary, our study defines a novel atmospheric environmental mechanism that mediates PM-aggravated microglia pathogenic activities, and establishes a systematic approach for the investigation of the effects of environmental exposure in neurologic disorders.

A Children's Health Perspective on Nano- and Microplastics

BACKGROUND

Pregnancy, infancy, and childhood are sensitive windows for environmental exposures. Yet the health effects of exposure to nano- and microplastics (NMPs) remain largely uninvestigated or unknown. Although plastic chemicals are a well-established research topic, the impacts of plastic particles are unexplored, especially with regard to early life exposures.

OBJECTIVES

This commentary aims to summarize the knowns and unknowns around child- and pregnancy-relevant exposures to NMPs via inhalation, placental transfer, ingestion and breastmilk, and dermal absorption.

METHODS

A comprehensive literature search to map the state of the science on NMPs found 37 primary research articles on the health relevance of NMPs during early life and revealed major knowledge gaps in the field. We discuss opportunities and challenges for quantifying child-specific exposures (e.g., NMPs in breastmilk or infant formula) and health effects, in light of global inequalities in baby bottle use, consumption of packaged foods, air pollution, hazardous plastic disposal, and regulatory safeguards. We also summarize research needs for linking child health and NMP exposures and address the unknowns in the context of public health action.

DISCUSSION

Few studies have addressed child-specific sources of exposure, and exposure estimates currently rely on generic assumptions rather than empirical measurements. Furthermore, toxicological research on NMPs has not specifically focused on child health, yet children's immature defense mechanisms make them particularly vulnerable. Apart from few studies investigating the placental transfer of NMPs, the physicochemical properties (e.g., polymer, size, shape, charge) driving the absorption, biodistribution, and elimination in early life have yet to be benchmarked. Accordingly, the evidence base regarding the potential health impacts of NMPs in early life remains sparse. Based on the evidence to date, we provide recommendations to fill research gaps, stimulate policymakers and industry to address the safety of NMPs, and point to opportunities for families to reduce early life exposures to plastic. https://doi.org/10.1289/EHP9086.

Blood lead and mercury levels are associated with low resting heart rate in community adolescent boys

While the neurotoxic effects of heavy metals at even low levels have been well-studied, few studies have examined the cardiovascular effects of heavy metals on resting heart rate and these have focused on adult populations. The present study aimed to examine the association between low-level environmental lead and mercury exposure and resting heart rate in community adolescents. As part of the China Jintan Cohort Study, 532 adolescents aged 12 years (SD = 0.6) were tested for blood levels of lead (BLL) and mercury (BML) and resting heart rate (RHR). Generalized linear models were conducted to test the relationship between BLL and BML and RHR, controlling for children's sex, age, and socioeconomic status. Analyses were clustered at the preschool level when the children were recruited to adjust for standard error. The mean (SD) BLL and BML were 3.14 (SD = 1.19) μg/dL and 1.26 (SD = 0.68) μg/L at age 12 years, respectively. After adjusting for confounders, we found a significant interaction between BML and BLL in predicting RHR in boys (B = -1.27, SE = 0.49, p < 0.01, n = 289). We created BLL and BML groups in boys based on median cut-offs. Boys in the High BLL/High BML group had significantly lower RHR (mean = 84.22 beats per minute [bpm], SD = 8.77, n = 61) than boys in the Low BLL/Low BML group (mean = 89.03 bpm, SD = 10.75, n = 69; p < 0.05). BML and BLL did not interact to predict RHR in girls (B = -0.18, SE = 0.88, p > 0.05, n = 242). Combined high BLL and BML were associated with low RHR in community adolescent boys. Low RHR is an indication of chronic under-arousal and has been implicated in psychopathology, particularly for externalizing behavior. Our findings may stimulate further communication and research in this area.

Predisposition to Alzheimer's and Age-Related Brain Pathologies by PM2.5 Exposure: Perspective on the Roles of Oxidative Stress and TRPM2 Channel

Accumulating epidemiological evidence supports that chronic exposure to ambient fine particular matters of <2.5 μm (PM2.5) predisposes both children and adults to Alzheimer’s disease (AD) and age-related brain damage leading to dementia. There is also experimental evidence to show that PM2.5 exposure results in early onset of AD-related pathologies in transgenic AD mice and development of AD-related and age-related brain pathologies in healthy rodents. Studies have also documented that PM2.5 exposure causes AD-linked molecular and cellular alterations, such as mitochondrial dysfunction, synaptic deficits, impaired neurite growth, neuronal cell death, glial cell activation, neuroinflammation, and neurovascular dysfunction, in addition to elevated levels of amyloid β (Aβ) and tau phosphorylation. Oxidative stress and the oxidative stress-sensitive TRPM2 channel play important roles in mediating multiple molecular and cellular alterations that underpin AD-related cognitive dysfunction. Documented evidence suggests critical engagement of oxidative stress and TRPM2 channel activation in various PM2.5-induced cellular effects. Here we discuss recent studies that favor causative relationships of PM2.5 exposure to increased AD prevalence and AD- and age-related pathologies, and raise the perspective on the roles of oxidative stress and the TRPM2 channel in mediating PM2.5-induced predisposition to AD and age-related brain damage.

A New Integrative Theory of Brain-Body-Ecosystem Medicine: From the Hippocratic Holistic View of Medicine to Our Modern Society

Humans are increasingly aware that their fate will depend on the wisdom they apply in interacting with the ecosystem. Its health is defined as the condition in which the ecosystem can deliver and continuously renew its fundamental services. A healthy ecosystem allows optimal interactions between humans and the other biotic/abiotic components, and only in a healthy ecosystem can humans survive and efficiently reproduce. Thus, both the human and ecosystem health should be considered together in view of their interdependence. The present article suggests that this relationship could be considered starting from the Hippocrates (460 BC-370 BC) work "On Airs, Waters, and Places" to derive useful medical and philosophical implications for medicine which is indeed a topic that involves scientific as well as philosophical concepts that implicate a background broader than the human body. The brain-body-ecosystem medicine is proposed as a new more complete approach to safeguarding human health. Epidemiological data demonstrate that exploitation of the environment resulting in ecosystem damage affects human health and in several instances these diseases can be detected by modifications in the heart-brain interactions that can be diagnosed through the analysis of changes in heart rate variability.

Lead exposure-induced cognitive impairment through RyR-modulating intracellular calcium signaling in aged rats

Lead is widely distributed in the environment and has become a global public health issue. It is well known that lead exposure induces not only neurodevelopmental toxicity but also neurodegenerative diseases, with learning and memory impairment in the later stage. However, the molecular mechanisms remain elusive. The present study investigated the effects of early life and lifetime lead exposure on cognition and identified the molecular mechanisms involved in aged rats. The results herein demonstrated that the lead concentration in peripheral blood and brain tissues in aged rats was significantly increased in a lead dose-dependent manner. High-dose lead exposure caused cognitive functional impairment in aged rats, concomitant with a longer escape latency and a lower frequency of crossing the platform via Morris water maze testing compared to those in the control and low-dose lead exposure groups. Importantly, neuron functional defects were still observed even in early life lead exposure during the prenatal and weaning periods in aged rats. The neurotoxicity induced by lead exposure was morphologically evidenced by a recessed nuclear membrane, a swollen endoplasmic reticulum, and mitochondria in the neurons. Mechanistically, the exposure of aged rats to lead resulted in increasing free calcium concentration, reactive oxygen species, and apoptosis in the hippocampal neurons. Lead exposure increased RyR3 expression and decreased the levels of p-CaMKIIα/CaMKIIα and p-CREB/CREB in the hippocampus of aged rats. These findings indicated that early life lead exposure-induced cognition disorder was irreversible in aged rats. Lead-induced neurotoxicity might be related to the upregulation of RyR3 expression and high levels of intracellular free calcium with increasing lead concentration in injured neurons.