Interactions of chronic lead exposure and intermittent stress: consequences for brain catecholamine systems and associated behaviors and HPA axis function

Lead exposure and its relationship with fecal cortisol levels in black howler monkeys (Alouatta pigra)

Efficiently detecting early environmental threats to wildlife is vital for conservation. Beyond obvious dangers like habitat loss or deforestation, our study focuses on one of the most hazardous toxic metals for wildlife: lead (Pb). Pb is a widespread, cumulative, and insidious environmental pollutant that can trigger a wide range of physiological, biochemical, and behavioral disorders. In fact, Pb can cause permanent dysfunction of the major stress system, the hypothalamic pituitary adrenal (HPA) axis. We analyzed Pb and cortisol concentrations in fecal samples from Alouatta pigra in southern Mexico. Fecal samples were collected across six sites categorized as free-ranging (n = 65; conserved and disturbed) and from captive animals (n = 58). Additionally, we collected soil samples (n = 35). We found that Pb was present in 28% of fecal samples and 83% of soil samples. There was a positive relation between fecal and soil Pb levels, and fecal Pb concentration was negatively associated with cortisol levels. However, the claim of Pb being a direct interference with HPA axis requires further investigation. Given our findings, assessing wildlife exposure can be a valuable tool for understanding potential Pb exposure levels in the environment and its possible implications for human health. It can also serve as an early warning system of these consequences.

Prenatal manganese biomarkers and operant test battery performance in Mexican children: Effect modification by child sex

BACKGROUND

Manganese (Mn) is essential to healthy neurodevelopment, but both Mn deficiency and over-exposure have been linked to prefrontal cortex (PFC) impairments, the brain region that regulates cognitive and neurobehavioral processes responsible for spatial memory, learning, motivation, and time perception. These processes facilitated by attention, inhibitory control, working memory, and cognitive flexibility are often sexually dimorphic and complex, driven by multiple interconnected neurologic and cognitive domains.

OBJECTIVE

We investigated the role of child sex as an effect modifier of the association between prenatal Mn exposure and performance in an operant testing battery (OTB) that assessed multiple cognitive and behavioral functional domains.

METHODS

Children (N = 575) aged 6-8 years completed five OTB tasks. Blood and urinary Mn measurements were collected from mothers in the 2nd and 3rd trimesters. Multiple regression models estimated the association between Mn biomarkers at each trimester with OTB performance while adjusting for socio-demographic covariates. Covariate-adjusted weighted quantile sum (WQS) regression models were used to estimate the association of a Mn multi-media biomarker (MMB) mixture with OTB performance. Interaction terms were used to estimate modification effect by child sex.

RESULTS

Higher blood Mn exposure was associated with better response rates (more motivation) on the progressive ratio task and higher overall accuracy on the delayed matching-to-sample task. In the WQS models, the MMB mixture was associated with better response rates (more motivation) on the progressive ratio task. Additionally, for the linear and WQS models, we observed a modification effect by child sex in the progressive ratio and delayed matching-to-sample tasks. Higher prenatal Mn biomarker levels were associated with improved task performance for girls and reduced performance in boys.

CONCLUSION

Higher prenatal blood Mn concentrations and the MMB mixture predicted improved performance on two of five operant tasks. Higher prenatal Mn concentrations regulated executive functions in children in a sexually dimorphic manner. Higher prenatal Mn exposure is associated with improved performance on spatial memory and motivation tasks in girls, suggesting that Mn's nutritional role is sexually dimorphic, and should be considered when making dietary and/or environmental intervention recommendations.

Associations of prenatal and childhood Pb exposure with allostatic load in adolescence: Findings from the ELEMENT cohort study

The biological pathways which link lead (Pb) and long-term outcomes are unclear, though rodent models and a few human studies suggest Pb may alter the body's stress response systems, which over time, can elicit dysregulated stress responses with cumulative impacts. This study examined associations between prenatal and early childhood Pb exposure and adolescent allostatic load, an index of an individual's body burden of stress in multiple biological systems, and further examined sex-based associations. Among 391 (51% male) participants in the ELEMENT birth cohort, we related trimester-specific maternal blood Pb, 1-month postpartum maternal tibia and patella Pb, and child blood Pb at 12-24 months to an allostatic load index in adolescence comprised of biomarkers of cardiovascular, metabolic, neuroendocrine, and immune function. The results were overall mixed, with prenatal exposure, particularly maternal bone Pb, being positively associated with allostatic load, and early childhood Pb showing mixed results for males and females. In adjusted Poisson regression models, 1 mcg/g increase in tibia Pb was associated with a 1% change in expected allostatic load (IRR = 1.01; 95%CI 0.99, 1.02). We found a significant Pb × sex interaction (IRR = 1.05; 95%CI 1.01, 1.10); where males saw an increasing percent change in allostatic load as 12 month Pb levels increased compared to females who saw a decreasing allostatic load. Further examination of allostatic load will facilitate the determination of potential mechanistic pathways between developmental toxicant exposures and later-in-life cardiometabolic outcomes.

Uncovering the Molecular Link Between Lead Toxicity and Parkinson's Disease

Significance: Parkinson's disease (PD) is a progressive neurodegenerative disorder that affects millions around the world. The etiology of PD remains unknown, but environmental and occupational exposures to heavy metals are likely at play, and may impact the severity of the disease. Lead is a toxin known to affect many organs in the body throughout life, particularly the central nervous system. Recent Advances: In this study, we summarize and examine the evidence for such environmental and/or occupational exposures, with a focus on the molecular mechanisms associated with lead exposure and its potential contribution to the onset of parkinsonism in PD. In particular, populational studies suggest higher bone and blood lead levels are associated with increased risk of PD. Interestingly, low levels of lead exposure in the very early stages of life cause increase the production of alpha-synuclein protein in animal models. Critical Issues: Although the specific mechanisms underlying this association have not been fully assessed, oxidative stress and mitochondrial dysfunction are likely implicated and may explain the toxic effects that connect lead exposure to parkinsonism. Future Directions: Additional pre-clinical and clinical studies should be performed in order to further document the molecular link between lead toxicity and PD, as this may open novel perspectives in terms of disease prevention. Antioxid. Redox Signal. 39, 321-335.

The mediating role of gut microbiota in the associations of prenatal maternal combined exposure to lead and stress with neurodevelopmental deficits in young rats

Prenatal single and combined exposure to lead (Pb) and stress (Ps) impairs neurodevelopment. Prenatal single exposure to Pb or Ps affects the composition of intestinal microbiota, and bidirectional communication between gut microbiota and central nervous system has been well recognized. However, whether gut microbiota mediated the effects of prenatal Pb+Ps co-exposure on neurodevelopmental deficits remains unclear. This study established rat models with prenatal single and combined exposure to Ps and Pb. We investigated the effects of such prenatal single and combined exposure on hippocampal structures using morphological analyses, on learning/memory using the Morris-water-maze test, and on fecal microbiota using 16S rRNA sequencing. The mediating roles of gut microbiota were analyzed using the bootstrap method. The study found both single and combined exposure affected hippocampal ultra-structures and spatial learning/memory, and the most significant impairments were observed in the Pb+Ps group. Prenatal Pb+Ps co-exposure decreased fecal microbial alpha/beta-diversity. Significantly lower levels of B/F-ratio, class-Bacteroidia, order-Bacteroidales, and family-S24-7, and significantly higher levels of class-Bacilli, order-Lactobacillales, family-Lactobacillaceae, and genus-Lactobacillus were observed in the co-exposure group, compared with the controls. Increased relative abundances of genus-Helicobacter mediated the detrimental effect of prenatal Ps+Pb co-exposure on learning/memory [β (95%CI) for the total and indirect effects: - 10.70 (-19.19, -2.21) and - 4.65(-11.07, -1.85)], accounting for 43.47% of the total effect. As a result, increased relative abundances of genus-Lactobacillus alleviated the adverse effects of the co-exposure on learning/memory, and the alleviation effect accounted for 44.55% of the direct effect [β (95%CI) for the direct and indirect effects: - 0.28(-0.48, -0.08) and 0.13(0.01, 0.41)]. This study suggested that prenatal combined exposure to Pb and Ps induced more impairments in offspring gut microbiota and neurodevelopment than single exposure, and alterations in fecal microbiome may mediate the developmental neurotoxicity induced by such prenatal co-exposure.

Effects of cadmium and lead co-exposure on glucocorticoid levels in rural residents of northwest China

Cadmium (Cd) and lead (Pb) are important environmental endocrine disruptors that are associated with adverse health problems. However, the effects of co-exposure to Cd and Pb on glucocorticoids (GCs) in the body at environmental levels are limited. A total of 468 subjects from the Dongdagou-Xinglong cohort (DDG-XL) were included in this study. We measured the serum levels of two representative endogenous GCs [cortisol (CRL) and cortisone (CRN)], and whole blood levels of Cd and Pb. Multiple linear regression models were constructed to explore the associations of single or combined Cd and Pb exposure with serum CRL and CRN levels. The interactive effects of Cd and Pb on GCs were further assessed using mediation analysis and moderation analysis. Single-heavy metal exposure analysis with adjustment for potential confounders showed that the serum CRL level decreased when the blood Cd or Pb concentration gradually increased (P trend <0.01). Additionally, subjects with high Cd or Pb exposure (Q4) had significantly reduced serum CRN levels compared to those with low Cd or Pb exposure (Q1) (P < 0.05). In Cd and Pb co-exposure analysis, significant negative dose-response relationships were observed between co-exposure to Cd and Pb and serum CRL and CRN levels. Furthermore, mediation analysis showed that Cd completely mediated the relationship between Pb and GCs, and moderation analysis suggested that Pb might weaken the negative relationship between Cd and GCs. These findings suggest that single or combined exposure to Cd and Pb interferes with the homeostasis of serum CRL and CRN levels. Furthermore, we innovatively propose that Cd and Pb may have interactive effects on GCs levels, and Pb can antagonize the negative relationship between Cd and GCs, which may provide clues for further studies on endocrine and metabolic disorders related to these heavy metals.

Firearm licensure, lead levels and suicides in Massachusetts

Nationally, between 2011 and 2019, suicide was the second leading cause of injury death, and about half of all suicides were firearm related. An overlooked factor connecting firearms and suicide is lead exposure. Lead bullets and primers are used throughout the US and pose danger to adults and children. Most (not all) studies link lead to mental illness, while others link lead with suicide. Research has linked lead and firearm violence, but rarely examined the relationship among firearms, lead exposure, and suicide. We collected data for cities/towns in Massachusetts between 2011 and 2019 regarding the number of firearm licenses, suicides, prevalence of blood lead levels, and covariates. We hypothesized that; 1) towns with higher levels of licensure will have higher levels of firearm suicides but licensure will have little relationship with non-firearm suicide; 2) towns with higher levels of licensures would have higher rates of lead exposure; 3) higher lead levels would be associated with higher rates of suicide by all methods. Individuals living in towns with higher rates of licensure were significantly more likely to die in firearm suicides and all suicide types. They were not more or less likely to die from non-firearm suicides. Lead was a predictor of all suicide types. Our study appears to be the first to show the established firearm suicide relationships holds within municipalities in a single state. We provide evidence concerning the link between lead exposure and suicide, particularly from firearms, and provide a glimpse into the relationship between firearm prevalence and elevated blood lead levels.

Environmental Stressors and the PINE Network: Can Physical Environmental Stressors Drive Long-Term Physical and Mental Health Risks?

Both psychosocial and physical environmental stressors have been linked to chronic mental health and chronic medical conditions. The psycho-immune-neuroendocrine (PINE) network details metabolomic pathways which are responsive to varied stressors and link chronic medical conditions with mental disorders, such as major depressive disorder via a network of pathophysiological pathways. The primary objective of this review is to explore evidence of relationships between airborne particulate matter (PM, as a concrete example of a physical environmental stressor), the PINE network and chronic non-communicable diseases (NCDs), including mental health sequelae, with a view to supporting the assertion that physical environmental stressors (not only psychosocial stressors) disrupt the PINE network, leading to NCDs. Biological links have been established between PM exposure, key sub-networks of the PINE model and mental health sequelae, suggesting that in theory, long-term mental health impacts of PM exposure may exist, driven by the disruption of these biological networks. This disruption could trans-generationally influence health; however, long-term studies and information on chronic outcomes following acute exposure event are still lacking, limiting what is currently known beyond the acute exposure and all-cause mortality. More empirical evidence is needed, especially to link long-term mental health sequelae to PM exposure, arising from PINE pathophysiology. Relationships between physical and psychosocial stressors, and especially the concept of such stressors acting together to impact on PINE network function, leading to linked NCDs, evokes the concept of syndemics, and these are discussed in the context of the PINE network.

Do Neighborhood Factors Modify the Effects of Lead Exposure on Child Behavior?

Lead exposure and neighborhoods can affect children’s behavior, but it is unclear if neighborhood characteristics modify the effects of lead on behavior. Understanding these modifications has important intervention implications. Blood lead levels (BLLs) in children (~7 years) from Montevideo, Uruguay, were categorized at 2 µg/dL. Teachers completed two behavior rating scales (n = 455). At one-year follow-up (n = 380), caregivers reported child tantrums and parenting conflicts. Multilevel generalized linear models tested associations between BLLs and behavior, with neighborhood disadvantage, normalized difference vegetation index (NDVI), and distance to nearest greenspace as effect modifiers. No effect modification was noted for neighborhood disadvantage or NDVI. Children living nearest to greenspace with BLLs < 2 µg/dL were lower on behavior problem scales compared to children with BLLs ≥ 2 µg/dL. When furthest from greenspace, children were similar on behavior problems regardless of BLL. The probability of daily tantrums and conflicts was ~20% among children with BLLs < 2 µg/dL compared to ~45% among children with BLLs ≥ 2 µg/dL when closest to greenspace. Furthest from greenspace, BLLs were not associated with tantrums and conflicts. Effect modification of BLL on child behavior by distance to greenspace suggests that interventions should consider both greenspace access and lead exposure prevention.

Impact of Environmental Pollutants on Gut Microbiome and Mental Health via the Gut–Brain Axis

Over the last few years, the microbiome has emerged as a high-priority research area to discover missing links between brain health and gut dysbiosis. Emerging evidence suggests that the commensal gut microbiome is an important regulator of the gut–brain axis and plays a critical role in brain physiology. Engaging microbiome-generated metabolites such as short-chain fatty acids, the immune system, the enteric nervous system, the endocrine system (including the HPA axis), tryptophan metabolism or the vagus nerve plays a crucial role in communication between the gut microbes and the brain. Humans are exposed to a wide range of pollutants in everyday life that impact our intestinal microbiota and manipulate the bidirectional communication between the gut and the brain, resulting in predisposition to psychiatric or neurological disorders. However, the interaction between xenobiotics, microbiota and neurotoxicity has yet to be completely investigated. Although research into the precise processes of the microbiota–gut–brain axis is growing rapidly, comprehending the implications of environmental contaminants remains challenging. In these milieus, we herein discuss how various environmental pollutants such as phthalates, heavy metals, Bisphenol A and particulate matter may alter the intricate microbiota–gut–brain axis thereby impacting our neurological and overall mental health.

Interactions of agricultural pesticide use near home during pregnancy and adverse childhood experiences on adolescent neurobehavioral development in the CHAMACOS study

BACKGROUND

Studies have documented independent adverse associations between prenatal and early-life exposure to environmental chemicals and social adversity with child neurodevelopment; however, few have considered these exposures jointly. The objective of this analysis is to examine whether associations of pesticide mixtures and adolescent neurobehavioral development are modified by early-life adversity in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) cohort.

METHODS

We used linear mixed effects Bayesian Hierarchical Models (BHM) to examine the joint effect of applications of 11 agricultural pesticides within 1 km of maternal homes during pregnancy and youth-reported Adverse Childhood Experiences (ACEs) with maternal and youth-reported internalizing behaviors, hyperactivity, and attention problems assessed via the Behavior Assessment for Children (BASC) (mean = 50, standard deviation = 10) at ages 16 and 18 years (n = 458).

RESULTS

The median (25th-75th percentiles) of ACEs was 1 (0-3); 72.3% of participants had low ACEs (0-2 events) and 27.7% had ACEs (3+ events). Overall, there was little evidence of modification of exposure-outcome associations by ACEs. A two-fold increase in malathion use was associated with increased internalizing behaviors among those with high ACEs from both maternal- (β = 1.9; 95% Credible Interval (CrI): 0.2, 3.7 for high ACEs vs. β = -0.1; 95% CrI: 1.2, 0.9 for low ACEs) and youth-report (β = 2.1; 95% CrI: 0.4, 3.8 for high ACEs vs. β = 0.2; 95% CrI: 0.8, 1.2 for low ACEs). Applications of malathion and dimethoate were also associated with higher youth-reported hyperactivity and/or inattention among those with high ACEs.

CONCLUSION

We observed little evidence of effect modification of agricultural pesticide use near the home during pregnancy and adolescent behavioral problems by child ACEs. Future studies should examine critical windows of susceptibility of exposure to chemical and non-chemical stressors and should consider biomarker-based exposure assessment methods.

Social status and susceptibility to wildfire smoke among outdoor-housed female rhesus monkeys: A natural experiment

Introduction

Wildfire smoke (WFS) exposure is a growing threat to human health, and lower socioeconomic position (SEP) has been shown to increase pollution susceptibility. Studies of SEP-related susceptibility, however, are often compromised due to spatial confounding between lower-SEP and pollution. Here we examine outdoor-housed nonhuman primates, living in natural social hierarchy in a common location, born during years of high vs. low WFS, to examine the separate and combined effects of WFS and social rank, an analog to SEP, on lung and immune function.

Methods

Twenty-one females were born during extreme WFS events in summer 2008; 22 were born in summer 2009, during low WFS. Pulmonary function and circulating cytokines were measured three years later, in adolescence. We estimated fine particulate (PM_2.5) and ozone exposures during each animal's first 90 days and three years of age using regulatory data. Early-life social status was estimated using maternal rank at birth, as rank in females is relatively stable throughout life, and closely approximates mother's rank. We tested associations among WFS exposure, rank, and endpoints using linear regression and ANOVA.

Results

Higher WFS exposure in infancy was, on average, associated with lower functional residual capacity (FRC), residual volume (RV), tissue compliance (Ct), and IL-8 secretion in adolescence. Higher social rank conferred significantly higher expiratory reserve volume (ERV) and functional residual capacity (FRC) solely among those born in the high-WFS year (2008). Differences in effects of rank between years were not significant after adjustment for multiple comparisons.

Conclusions

Exposure to WFS in infancy generally conferred lower adolescent respiratory volumes and inflammatory cytokines. Higher rank conferred higher respiratory volumes only among females born during WFS, suggesting the possibility that the health benefits of rank may be more apparent under environmental challenge.

The urban lead (Pb) burden in humans, animals and the natural environment

Centuries of human activities, particularly housing and transportation practices from the late 19th century through the 1980's, dispersed hundreds of millions of tons of lead into our urban areas. The urban lead burden is evident among humans, wild and domesticated animals, and plants. Animal lead exposures closely mirror and often exceed the lead exposure patterns of their human partners. Some examples: Pigeons in New York City neighborhoods mimicked the lead exposures of neighborhood children, with more contaminated areas associated with higher exposures in both species. Also, immediately following the lead in drinking water crisis in Flint MI in 2015, blood lead levels in pet dogs in Flint were 4 times higher than in surrounding towns. And combining lead's neurotoxicity with urban stress results in well-characterized aggressive behaviors across multiple species. Lead pollution is not distributed evenly across urban areas. Although average US pediatric lead exposures have declined by 90% since the 1970s, there remain well defined neighborhoods where children continue to have toxic lead exposures; animals are poisoned there, too. Those neighborhoods tend to have disproportionate commercial and industrial lead activity; a history of dense traffic; older and deteriorating housing; past and operating landfills, dumps and hazardous waste sites; and often lead contaminated drinking water. The population there tends to be low income and minority. Urban wild and domesticated animals bear that same lead burden. Soil, buildings, dust and even trees constitute huge lead repositories throughout urban areas. Until and unless we begin to address the lead repositories in our cities, the urban lead burden will continue to impose enormous costs distributed disproportionately across the domains of the natural environment. Evidence-based research has shown the efficacy and cost-effectiveness of some US public policies to prevent or reduce these exposures. We end with a series of recommendations to manage lead-safe urban environments.

Forced swimming stress increases natatory activity of lead-exposed mice

Recent evidence points to the relationship between lead toxicity and the function of the hypothalamic-pituitary-adrenal axis, which suggests that lead exposure could influence how an individual cope with stress. Here we test this hypothesis by investigating the behavioral effects of lead exposure in mice during the forced swimming test (FST), a parading in which animals are exposed to a stressful situation and environment. Swiss mice received either 180 ppm or 540 ppm of lead acetate (Pb) in their ad-lib water supply for 60-90 days, starting at postnatal day 30. Control (Ctrl) mice drank tap water. At the end of the exposure period, mice were submitted to a 5-min session of FST or to an open-field session of the same duration. Data from naïve animals showed that corticosterone levels were higher for animals tested in the FST compared to animals tested in the open-field. Blood-lead levels (BLL) in Pb-exposed mice ranged from 14.3 to 106.9 µg/dL. No differences were observed in spontaneous locomotion between Ctrl and Pb-exposed groups in the open-field. However, in the FST, Pb-treated mice displayed higher swimming activity than Ctrl ones and this effect was observed even for animals with BLL higher than 20 µg/dL. Furthermore, significant differences in brain glutathione levels, used as an indicator of led toxicity, were only observed for BLL higher than 40 µg/dL. Overall, these findings suggest that swimming activity in the FST is a good indicator of lead toxicity and confirm our prediction that lead toxicity influences behavioral responses associated to stress.

Environment-wide association study on childhood obesity in the U.S

BACKGROUND

Childhood obesity is a national public health issue with increasing prevalence. It has been linked to diet, lack of physical activity, and genetic susceptibility, with more recent evidence that it could also result from environmental factors. Studies linking it to environmental factors are limited, unsystematic, incomprehensive, and inconclusive.

OBJECTIVE

To conduct an environment-wide association study (EWAS) to comprehensively investigate all the environmental factors available in a nationally representative sample of children to determine factors associated with childhood obesity.

METHODS

We utilized the 1999-2016 National Health and Nutrition Examination Survey (NHANES) datasets and included all children/adolescents (6-17 years). Obesity was measured using body mass index and waist to height ratio. A multinomial and binary logistic regression were used adjusting for age, sex, race/ethnicity, creatinine, calorie intake, physical activity, screen time, limitation to physical activities, and socioeconomic status. We then controlled for multiple hypothesis testing and validated our findings on a different cohort of children.

RESULTS

We found that metals such as beryllium (OR: 3.305 CI: 1.460-7.479) and platinum (OR: 1.346 CI: 1.107-1.636); vitamins such as gamma-tocopherol (OR: 8.297 CI: 5.683-12.114) and delta-tocopherol (OR: 1.841 CI:1.476-2.297); heterocyclic aromatic amines such as 2-Amino-9H-pyrido (2,3-b) indole (OR: 1.323 CI: 1.083-1.617) and 2-Amino-3-methyl-9H-pyriodo(2,3-b)indole (OR: 2.799 CI: 1.442-5.433); polycyclic aromatic amines such as 9- fluorene (OR: 1.509 CI: 1.230-1.851) and 4-phenanthrene (OR: 2.828 CI: 1.632-4.899); and caffeine metabolites such as 1,3,7-trimethyluric acid (OR: 1.22 CI: 1.029-1.414) and 1,3,7-trimethylxanthine (OR: 1.258 CI: 1.075-1.473) were positively and significantly associated with childhood obesity.

CONCLUSION

Following the unique concept of EWAS, certain environmental factors were associated with childhood obesity. Further studies are required to confirm these associations while investigating their mechanisms of action.

Metabolomic signatures of lead exposure in the VA Normative Aging Study

BACKGROUND

Lead (Pb) is widespread and exposure to this non-essential heavy metal can cause multiple negative health effects; however the mechanisms underlying these effects remain incompletely understood.

OBJECTIVES

To identify plasma metabolomic signatures of Pb exposure, as measured in blood and toenails.

METHODS

In a subset of men from the VA Normative Aging Study, mass-spectrometry based plasma metabolomic profiling was performed. Pb levels were measured in blood samples and toenail clippings collected concurrently. Multivariable linear regression models, smoothing splines and Pathway analyses were employed to identify metabolites associated with Pb exposure.

RESULTS

In 399 men, 858 metabolites were measured and passed QC, of which 154 (17.9%) were significantly associated with blood Pb (p < 0.05). Eleven of these passed stringent correction for multiple testing, including pro-hydroxy-pro (β(95%CI): 1.52 (0.93,2.12), p = 7.18x10^-7), N-acetylglycine (β(95%CI): 1.44 (0.85,2.02), p = 1.12x10^-6), tartarate (β(95%CI): 0.68 (0.35,1.00), p = 4.84x10^-5), vanillylmandelate (β(95%CI): 1.05 (0.47,1.63), p = 4.44x10^-7), and lysine (β(95%CI): 1.88 (-2.8,-0.95), p = 9.10x10^-5). A subset of 48 men had a second blood sample collected a mean of 6.1 years after their first. Three of the top eleven metabolites were also significant in this second blood sample. Furthermore, we identified 70 plasma metabolites associated with Pb as measured in toenails. Twenty-three plasma metabolites were significantly associated with both blood and toenail measures, while others appeared to be specific to the biosample in which Pb was measured. For example, benzanoate metabolism appeared to be of importance with the longer-term exposure assessed by toenails.

DISCUSSION

Pb exposure is responsible for 0.6% of the global burden of disease and metabolomics is particularly well-suited to explore its pathogenic mechanisms. In this study, we identified metabolites and metabolomic pathways associated with Pb exposure that suggest that Pb exposure acts through oxidative stress and immune dysfunction. These findings help us to better understand the biology of this important public health burden.

Air Pollution, Stress, and Allostatic Load: Linking Systemic and Central Nervous System Impacts

 Air pollution is a risk factor for cardiovascular and respiratory morbidity and mortality. A growing literature also links exposure to diverse air pollutants (e.g., nanoparticles, particulate matter, ozone, traffic-related air pollution) with brain health, including increased incidence of neurological and psychiatric disorders such as cognitive decline, dementia (including Alzheimer’s disease), anxiety, depression, and suicide. A critical gap in our understanding of adverse impacts of pollutants on the central nervous system (CNS) is the early initiating events triggered by pollutant inhalation that contribute to disease progression. Recent experimental evidence has shown that particulate matter and ozone, two common pollutants with differing characteristics and reactivity, can activate the hypothalamic-pituitary-adrenal (HPA) axis and release glucocorticoid stress hormones (cortisol in humans, corticosterone in rodents) as part of a neuroendocrine stress response. The brain is highly sensitive to stress: stress hormones affect cognition and mental health, and chronic stress can produce profound biochemical and structural changes in the brain. Chronic activation and/or dysfunction of the HPA axis also increases the burden on physiological stress response systems, conceptualized as allostatic load, and is a common pathway implicated in many diseases. The present paper provides an overview of how systemic stress-dependent biological responses common to particulate matter and ozone may provide insight into early CNS effects of pollutants, including links with oxidative, inflammatory, and metabolic processes. Evidence of pollutant effect modification by non-chemical stressors (e.g., socioeconomic position, psychosocial, noise), age (prenatal to elderly), and sex will also be reviewed in the context of susceptibility across the lifespan.

A Cumulative Risk Perspective for Occupational Health and Safety (OHS) Professionals

Cumulative risk assessment (CRA) addresses the combined risk associated with chemical and non-chemical exposures. Although CRA approaches are utilized in environmental and ecological contexts, they are rarely applied in workplaces. In this perspectives article, we strive to raise awareness among occupational health and safety (OHS) professionals and foster the greater adoption of a CRA perspective in practice. Specifically, we provide an overview of CRA literature as well as preliminary guidance on when to consider a CRA approach in occupational settings and how to establish reasonable boundaries. Examples of possible workplace co-exposures and voluntary risk management actions are discussed. We also highlight important implications for workplace CRA research and practice. In particular, future needs include simple tools for identifying combinations of chemical and non-chemical exposures, uniform risk management guidelines, and risk communication materials. Further development of practical CRA methods and tools are essential to meet the needs of complex and changing work environments.

Sex differences in the effects of lead exposure on growth and development in young children

The adverse effects of lead exposure on children's health have been widely investigated. Physical growth is a central indicator of health in early childhood. However, studies on the associations between lead exposure and the physical growth of young children are still equivocal. This study aimed to investigate the effects of lead exposure on young children's growth. A cross-sectional survey was conducted, and a total of 1678 young children were recruited. Blood lead levels were determined by graphite furnace atomic absorption spectrophotometry and anthropometric measurements were obtained by nurses. The weight-for-age Z-score (WAZ), height-for-age Z-score (HAZ) and BMI for-age Z-score (BMIZ) of the children were calculated according to World Health Organization standards. Multivariable linear models after adjustment for potential confounders were used to evaluate the associations between lead exposure and childhood anthropometric characteristics. Meanwhile, the sex differences in these associations were also examined. The median blood lead levels in total subjects, in boys and in girls were 46.44, 49.00 and 43.27 μg/L, respectively. After adjusting for confounders, a significantly negative association of blood lead levels with WAZ and HAZ was observed. After stratification by sex, the blood lead levels in children were negatively associated with WAZ and HAZ in boys but not in girls. Meanwhile, we further provide evidence that blood lead levels below 50 μg/L may also have adverse effects on young children's HAZ. Our findings suggest that lead exposure may have sex-specific effects on physical growth in young children and that blood lead level in a low levels may also have adverse effects on children's physical growth and development.

Association between blood lead exposure and mental health in pregnant women: Results from the Japan environment and children's study

OBJECTIVE

Although environmental lead exposure has decreased, several studies have shown that low-level lead exposure can result in adverse psychological symptoms. However, few studies have examined lead neurotoxicity in pregnant women. We investigated the association between lead exposure and psychological symptoms in pregnant women, and between socio-economic status and blood lead levels.

METHODS

Blood lead levels were measured in 17,267 pregnant women in the Japan Environment and Children's Study. Odds ratios (ORs) for high blood lead levels were calculated using multinomial logistic regression. Psychological symptoms were assessed using the Kessler Psychological Distress Scale (K6). ORs for depression (K6 ≥ 13 or ≥5) were calculated using logistic regression with adjustment for potential confounders.

RESULTS

The geometric mean of whole blood lead levels was 0.58 μg/dl (range 0.14-6.75 μg/dl). Higher blood lead levels were associated with older age (OR 1.79, 9 5% confidence interval [CI] 1.46-2.19), unmarried status (OR 1.75, 95 % CI 1.31-2.33), lower household income (OR 1.76, 95 % CI 1.38-2.24), and lower educational attainment (OR 1.34, 95 % CI 1.20-1.48). The percentage of women with K6 scores ≥13 and ≥5 was 3 % and 28.2 %, respectively. There was no significant association between lead exposure and K6 score (K6 ≥ 13: OR 1.00, 95 % CI 0.76-1.32; K6 ≥ 5: OR 0.98, 95 % CI 0.88-1.09).

CONCLUSION

Our results indicate a small but significant association between higher blood lead levels and lower socio-economic status in a population with low blood lead levels, but no association between low-level lead exposure and psychological symptoms.

Corticosterone mediates telomere length in raptor chicks exposed to chemical mixture

Stressors experience early in life by animals may have carry over impacts on life-traits over the life cycle. Accelerated telomere attrition induced by stress during development and growth could play a role in such delayed effects. Among stressors, exposure to chemicals may modify telomere dynamic but, to date, the trends evidenced between exposure and telomere shortening remains inconsistent. Moreover, the role of corticosterone as a possible mediator of chemical impact on telomere is not yet clearly established. Here, we investigated in wild populations of Red kite whether nestling exposure to metals and pesticides was related to corticosterone concentrations in feathers and telomere length measured in 47 individuals. Lead and mercury concentrations in blood ranged from 2.3 to 59.0 µg L^-1 and to 1.4 to 115.7 µg L^-1, respectively, and were below the toxicity thresholds proposed for wildlife. Rodenticides were detected in 30% of the chicks. Corticosterone increased with mercury and lead in interaction, showing a synergistic effect of these 2 non-essential metals on this stress hormone. Telomere length was not linked to metals and/or rodenticide exposure while it was related negatively to corticosterone. The relationship between telomere and corticosterone was modulated by nestling's age, which suggests that the rate of telomere shortening is higher when corticosterone increases. Our findings propose an effect of low exposure of Red Kite nestlings to mercury and lead mixture to raise baseline corticosterone in feathers. The relationships established suggest the hypothesis that telomere attrition could be an indirect consequence of metal exposure mediated by corticosterone.

Lineage- and Sex-Dependent Behavioral and Biochemical Transgenerational Consequences of Developmental Exposure to Lead, Prenatal Stress, and Combined Lead and Prenatal Stress in Mice

BACKGROUND

Lead (Pb) exposure and prenatal stress (PS) during development are co-occurring risk factors with shared biological substrates. PS has been associated with transgenerational passage of altered behavioral phenotypes, whereas the transgenerational behavioral or biochemical consequences of Pb exposure, and modification of any such effects by PS, is unknown.

OBJECTIVES

The present study sought to determine whether Pb, PS, or combined Pb and PS exposures produced adverse transgenerational consequences on brain and behavior.

METHODS

Maternal Pb and PS exposures were carried out in F0 mice. Outside breeders were used at each subsequent breeding, producing four F1-F2 lineages: [F1 female-F2 female (FF), FM (male), MF, and MM]. F3 offspring were generated from each of these lineages and examined for outcomes previously found to be altered by Pb, PS, or combined Pb and PS in F1 offspring: behavioral performance [fixed-interval (FI) schedule of food reward, locomotor activity, and anxiety-like behavior], dopamine function [striatal expression of tyrosine hydroxylase (Th)], glucocorticoid receptor (GR) and plasma corticosterone, as well as brain-derived neurotrophic factor (BDNF) and total percent DNA methylation of Th and Bdnf genes in the frontal cortex and hippocampus.

RESULTS

Maternal F0 Pb exposure produced runting in F3 offspring. Considered across lineages, F3 females exhibited Pb-related alterations in behavior, striatal BDNF levels, frontal cortical Th total percentage DNA methylation levels and serum corticosterone levels, whereas F3 males showed Pb- and PS-related alterations in behavior and total percent DNA methylation of hippocampal Bdnf. However, numerous lineage-specific effects were observed, most of greater magnitude than those observed across lineages, with outcomes differing by F3 sex.

DISCUSSION

These findings support the possibility that exposures of previous generations to Pb or PS may influence the brain and behavior of future generations. Observed changes were sex-dependent, with F3 females showing multiple changes through Pb-exposed lineages. Lineage effects may occur through maternal responses to pregnancy, altered maternal behavior, epigenetic modifications, or a combination of mechanisms, but they have significant public health ramifications regardless of mechanism. https://doi.org/10.1289/EHP4977.

Glucocorticoid and mineralocorticoid receptors and corticosteroid homeostasis are potential targets for endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs) have received significant concern, since they ubiquitously exist in the environment and are able to induce adverse health effects on human and wildlife. Increasing evidence shows that the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), members of the steroid receptor subfamily, are potential targets for EDCs. GR and MR mediate the actions of glucocorticoids and mineralocorticoids, respectively, which are two main classes of corticosteroids involved in many physiological processes. The effects of EDCs on the homeostasis of these two classes of corticosteroids have also gained more attention recently. This review summarized the effects of environmental GR/MR ligands on receptor activity, and disruption of corticosteroid homeostasis. More than 130 chemicals classified into 7 main categories were reviewed, including metals, metalloids, pesticides, bisphenol analogues, flame retardants, other industrial chemicals and pharmaceuticals. The mechanisms by which EDCs interfere with GR/MR activity are primarily involved in ligand-receptor binding, nuclear translocation of the receptor complex, DNA-receptor binding, and changes in the expression of endogenous GR/MR genes. Besides directly interfering with receptors, enzyme-catalyzed synthesis and prereceptor regulation pathways of corticosteroids are also important targets for EDCs. The collected evidence suggests that corticosteroids and their receptors should be considered as potential targets for safety assessment of EDCs. The recognition of relevant xenobiotics and their underlying mechanisms of action is still a challenge in this emerging field of research.

The effect of lead, restraint stress or their co-exposure on the movement disorders incidence in male mice

Lead is known as an environmental contaminant with neurotoxic properties. In addition, people experience different types of chronic stress, especially in developing countries. It has been established that lead or stress causes structural and physiological damages to the neural pathway like dopaminergic connections. Nevertheless, the effect of lead and restraint stress on movement behaviors when are experienced together has not been studied yet. In this study, male albino mice were randomly divided into different groups (n = 6). Lead acetate was daily injected at 15 mg/kg intraperitoneally for 2, 4, or 6 weeks. Restraint stress (6 h in a day) was applied alone or in combination with lead acetate for 2, 4, or 6 weeks. The catalepsy, akinesia, and the balance of animals were measured by bar test, elevated beam device, and rotarod to evaluate the movement disorders. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a known neurotoxin causes movement disorders, was used as positive control group. The results showed that exposure to the lead or stress or their combination for 6 weeks caused catalepsy, akinesia, and imbalance in the animals, while exposure for 2 or 4 weeks didn’t affect the movement items indices. The combination of lead and stress did not show any significant difference compared to the exposure to each of them individually. From the findings, Lead, stress, and their combination caused movement disorders in a time dependent manner. Short time exposure did not change movement behavior. The co-exposure to the lead and stress did not show additive or synergistic effects.

Childhood Lead Exposure and Adult Neurodegenerative Disease

Millions of Americans now entering midlife and old age were exposed to high levels of lead, a neurotoxin, as children. Evidence from animal-model and human observational studies suggest that childhood lead exposure may raise the risk of adult neurodegenerative disease, particularly dementia, through a variety of possible mechanisms including epigenetic modification, delayed cardiovascular and kidney disease, direct degenerative CNS injury from lead remobilized from bone, and lowered neural and cognitive reserve. Within the next ten years, the generation of children with the highest historical lead exposures, those born in the 1960s, 1970s, and 1980s, will begin to enter the age at which dementia symptoms tend to emerge. Many will also enter the age in which lead stored in the skeleton may be remobilized at greater rates, particularly for women entering menopause and men and women experiencing osteoporosis. Should childhood lead exposure prove pro-degenerative, the next twenty years will provide the last opportunities for possible early intervention to forestall greater degenerative disease burden across the aging lead-exposed population. More evidence is needed now to characterize the nature and magnitude of the degenerative risks facing adults exposed to lead as children and to identify interventions to limit long-term harm.

The State of Public Health Lead Policies: Implications for Urban Health Inequities and Recommendations for Health Equity

Although lead has been removed from paint and gasoline sold in the U.S., lead exposures persist, with communities of color and residents in urban and low-income areas at greatest risk for exposure. The persistence of and inequities in lead exposures raise questions about the scope and implementation of policies that address lead as a public health concern. To understand the multi-level nature of lead policies, this paper and case study reviews lead policies at the national level, for the state of California, and for Santa Ana, CA, a dense urban city in Southern California. Through a community-academic partnership process, this analysis examines lead exposure pathways represented, the level of intervention (e.g., prevention, remediation), and whether policies address health inequities. Results indicate that most national and state policies focus on establishing hazardous lead exposure levels in settings and consumer products, disclosing lead hazards, and remediating lead paint. Several policies focus on mitigating exposures rather than primary prevention. The persistence of lead exposures indicates the need to identify sustainable solutions to prevent lead exposures in the first place. We close with recommendations to reduce lead exposures across the life course, consider multiple lead exposure pathways, and reduce and eliminate health inequities related to lead.

Methods for Evaluating the Combined Effects of Chemical and Nonchemical Exposures for Cumulative Environmental Health Risk Assessment

Cumulative risk assessment (CRA) has been proposed as a means of evaluating possible additive and synergistic effects of multiple chemical, physical and social stressors on human health, with the goal of informing policy and decision-making, and protecting public health. Routine application of CRA to environmental regulatory and policy decision making, however, has been limited due to a perceived lack of appropriate quantitative approaches for assessing combined effects of chemical and nonchemical exposures. Seven research projects, which represented a variety of disciplines, including population health science, laboratory science, social sciences, geography, statistics and mathematics, were funded by the US Environmental Protection Agency (EPA) to help address this knowledge gap. We synthesize key insights from these unique studies to determine the implications for CRA practice and priorities for further research. Our analyses of these seven projects demonstrate that the necessary analytical methods to support CRA are available but are ultimately context-dependent. These projects collectively provided advancements for CRA in the areas of community engagement, characterization of exposures to nonchemical stressors, and assessment of health effects associated with joint exposures to chemical and psychosocial stressors.

Adiposity Genetic Risk Score Modifies the Association Between Blood Lead Level and Body Mass Index

CONTEXT

Previous epidemiological studies had inconsistent results regarding the relationship between blood lead level (BLL) and adiposity.

OBJECTIVE

We aimed to investigate the associations of BLL with body mass index (BMI) particularly using Mendelian randomization analyses and examine the interaction between obesity-predisposing genes and BLL on the associations.

DESIGN AND SETTING

A total of 3922 participants were enrolled from 16 sites in East China in 2014 from the Survey on Prevalence in East China for Metabolic Diseases and Risk Factors (ChiCTR-ECS-14005052, www.chictr.org.cn). We calculated the weighted BMI genetic risk score (GRS) based on 29 variants that were identified and validated in East Asians. BLL was measured by atomic absorption spectrometry.

MAIN OUTCOME MEASURE

BMI was calculated, and BMI ≥25 kg/m2 was defined as overweight.

RESULTS

Multivariable logistic regression analysis demonstrated significant associations between BMI with each unit increase in lnBLL (β = 0.24; 95% CI, 0.08 to 0.40; P < 0.001) and each 1-point increase in BMI-GRS (β = 0.08; 95% CI, 0.05 to 0.11; P < 0.001). The causal regression coefficients of genetically determined BMI for lnBLL were -0.003 (95% CI, -0.075 to 0.070), which showed no significance. The GRS modified the association of BLL with BMI and overweight (BMI ≥25 kg/m2; P for interaction = 0.031 and 0.001, respectively). Each unit of lnBLL was associated with 63% higher odds of overweight (OR 1.63; 95% CI, 1.30 to 2.05) in the highest quartile of GRS, but no significant associations were found in the lower three quartiles.

CONCLUSIONS

The associations of BLL with BMI and overweight (BMI ≥25 kg/m2) were significantly modulated by BMI genetic susceptibility.

Glucocorticoid measurement in plasma, urates, and feathers from California condors (Gymnogyps californianus) in response to a human-induced stressor

Vertebrates respond to stressful stimuli with the secretion of glucocorticoid (GC) hormones, such as corticosterone (CORT), and measurements of these hormones in wild species can provide insight into physiological responses to environmental and human-induced stressors. California condors (Gymnogyps californianus) are a critically endangered and intensively managed avian species for which information on GC response to stress is lacking. Here we evaluated a commercially available I125 double antibody radioimmunoassay (RIA) and an enzyme-linked immunosorbent assay (ELISA) kit for measurement of CORT and GC metabolites (GCM) in California condor plasma, urate, and feather samples. The precision and accuracy of the RIA assay outperformed the ELISA for CORT and GCM measurements, and CORT and GCM values were not comparable between the two assays for any sample type. RIA measurements of total CORT in condor plasma collected from 41 condors within 15 minutes of a handling stressor were highly variable (median = 70 ng/mL, range = 1-189 ng/mL) and significantly different between wild and captive condors (p = 0.02, two-tailed t-test, n = 10 wild and 11 captive). Urate GCM levels (median = 620 ng/g dry wt., range = 0.74-7200 ng/g dry wt., n = 216) significantly increased within 2 hr of the acute handling stressor (p = 0.032, n = 11 condors, one-tailed paired t-test), while feather section CORT concentrations (median = 18 pg/mm, range = 6.3-68 ng/g, n = 37) also varied widely within and between feathers. Comparison of multiple regression linear models shows condor age as a significant predictors of plasma CORT levels, while age, sex, and plasma CORT levels predicted GCM levels in urates collected within 30 min of the start of handling. Our findings highlight the need for validation when selecting an immunoassay for use with a new species, and suggest that non-invasively collected urates and feathers hold promise for assessing condor responses to acute or chronic environmental and human-induced stressors.

Endocrine active metals, prenatal stress and enhanced neurobehavioral disruption

Metals, including lead (Pb), methylmercury (MeHg) and arsenic (As), are long-known developmental neurotoxicants. More recently, environmental context has been recognized to modulate metals toxicity, including nutritional state and stress exposure. Modulation of metal toxicity by stress exposure can occur through shared targeting of endocrine systems, such as the hypothalamic-pituitary-adrenal axis (HPA). Our previous rodent research has identified that prenatal stress (PS) modulates neurotoxicity of two endocrine active metals (EAMs), Pb and MeHg, by altering HPA and CNS systems disrupting behavior. Here, we review this research and further test the hypothesis that prenatal stress modulates metals neurotoxicity by expanding to test the effect of developmental As ± PS exposure. Serum corticosterone and behavior was assessed in offspring of dams exposed to As ± PS. PS increased female offspring serum corticosterone at birth, while developmental As exposure decreased adult serum corticosterone in both sexes. As + PS induced reductions in locomotor activity in females and reduced response rates on a Fixed Interval schedule of reinforcement in males, with the latter suggesting unique learning deficits only in the combined exposure. As-exposed males showed increased time in the open arms of an elevated plus maze and decreased novel object recognition whereas females did not. These data further confirm the hypothesis that combined exposure to chemical (EAMs) and non-chemical (PS) stressors results in enhanced neurobehavioral toxicity. Given that humans are exposed to multiple environmental risk factors that alter endocrine function in development, such models are critical for risk assessment and public health protection, particularly for children.

Developmental manganese, lead, and barren cage exposure have adverse long-term neurocognitive, behavioral and monoamine effects in Sprague-Dawley rats

Developmental stress, including low socioeconomic status (SES), can induce dysregulation of the hypothalamic-pituitary-adrenal axis and result in long-term changes in stress reactivity. Children in lower SES households experience more stress and are more likely to be exposed to environmental neurotoxins such as lead (Pb) and manganese (Mn) than children in higher SES households. Co-exposure to stress, Pb, and Mn during early development may increase the risk of central nervous system dysfunction compared with unexposed children. To investigate the potential interaction of these factors, Sprague-Dawley rats were bred, and litters born in-house were culled on postnatal day (P)1 to 6 males and 6 females. One male and female within each litter were assigned to one of the following groups: 0 (vehicle), 10 mg/kg Pb, 100 mg/kg Mn, or 10 mg/kg Pb + 100 mg/kg Mn (PbMn), water gavage, and handled only from P4-28 with half the litters reared in cages with standard bedding (29 litters) and half with no bedding (Barren; 27 litters). Mn and PbMn groups had decreased anxiety, reduced acoustic startle, initial open-field hypoactivity, increased activity following (+)-methamphetamine, deficits in egocentric learning in the Cincinnati water maze (CWM), and deficits in latent inhibition conditioning. Pb increased anxiety and reduced open-field activity. Barren-reared rats had decreased anxiety, CWM deficits, increased startle, and initial open-field hyperactivity. Mn, PbMn, Pb Barren-reared groups had impaired Morris water maze performance. Pb altered neostriatal serotonin and norepinephrine, Mn increased hippocampal serotonin in males, Mn + Barren-rearing increased neostriatal serotonin, and Barren-rearing decreased neostriatal dopamine in males. At the doses used here, most effects were in the Mn and PbMn groups. Few interactions between Mn, Pb, and rearing stress were found, indicating that the interaction of these three variables is not as impactful as hypothesized.

Blood lead levels and hypothalamic-pituitary-adrenal function in middle-aged individuals

Experimental and epidemiological studies suggested that exposure to lead (Pb) may influence the hypothalamic-pituitary-adrenal (HPA) axis. However, previous studies have yielded mixed results. We evaluated changes in basal salivary cortisol levels and acute cortisol responsivity to psychological stress in relation with blood Pb levels (BPb), in Caucasian individuals 50-67 years of age. Data were collected through the Study of Genetics, Stress and Cognitive Development (2004-2006). Diurnal basal and stress-reactive salivary cortisol levels were collected and BPb levels were determined using inductively coupled plasma mass spectroscopy. A total of 65 participants were included in the current study. General linear mixed models were used to assess the association between BPb level and change in cortisol secretion over time, for diurnal basal pattern and stress-reactive pattern, respectively. The geometric mean BPb was 2.70μg/dL (± 1.44) and two exposure groups were created based on the median value of 2.48µg/dL. No difference in geometric mean of salivary cortisol (µg/dL) at awakening was observed between High and Low BPb groups (0.23 (± 0.11) vs 0.20 (± 0.11), p = 0.36). The overall pattern of change in both diurnal basal (from the awakening to bedtime) and reactive salivary cortisol (during the stress induction protocol) did not differ between groups. In these middle-aged and older adults, we concluded that Pb exposure, within the range observed in the current study, was associated with neither diurnal nor stress-reactive cortisol secretion. Further investigation with larger datasets are needed to confirm our observations.

Consumption of preserved egg, a high-lead-containing food, is strongly associated with depressive symptoms in Chinese adults

Previous studies have demonstrated adverse mental health effects of Pb exposure. The purpose of this study is to investigate the relationship between consumption of preserved egg (PE), a high-Pb-containing food and depressive symptoms among adults in China. A sample of 25 213 adults (mean age 41·4 (sd 11·8) years; males, 53·9 %) in Tianjin, China, was studied in a cross-sectional analysis. Dietary intake including PE was assessed using a valid self-administered FFQ. Depressive symptoms were assessed using the Self-Rating Depression Scale (SDS). The association was estimated by OR using logistic regression models adjusted for multiple confounders. The prevalence of elevated depressive symptoms was 6·6 % (SDS≥50). Compared with the least frequent PE consumption (<once/week), multivariable adjusted OR for elevated depressive symptoms were 1·52 (95 % CI 1·28, 1·81), 2·24 (95 % CI 1·76, 2·81) and 3·31 (95 % CI 2·52, 4·30) for consumption of once, 2–3 times and ≥4 times/week, respectively (Pfor trend<0·0001), indicating a clear dose–response relationship. The results suggested that higher consumption of PE was strongly associated with depressive symptoms among adults in China. These findings underscore the need to consider dietary Pb exposure as a risk factor for psychological distress.

Sclerostin activity plays a key role in the negative effect of glucocorticoid signaling on osteoblast function in mice

Stress during prenatal development is correlated with detrimental cognitive and behavioral outcomes in offspring. However, the long-term impact of prenatal stress (PS) and disrupted glucocorticoid signaling on bone mass and strength is not understood. In contrast, the detrimental effect of lead (Pb) on skeletal health is well documented. As stress and Pb act on common biological targets via glucocorticoid signaling pathways and co-occur in the environment, this study first sought to assess the combined effect of stress and Pb on bone quality in association with alterations in glucocorticoid signaling. Bone parameters were evaluated using microCT, histomorphometry, and strength determination in 8-month-old male mouse offspring subjected to PS on gestational days 16 and 17, lifetime Pb exposure (100 p.p.m. Pb in drinking water), or to both. Pb reduced trabecular bone mass and, when combined with PS, Pb unmasked an exaggerated decrement in bone mass and tensile strength. Next, to characterize a mechanism of glucocorticoid effect on bone, prednisolone was implanted subcutaneously (controlled-release pellet, 5 mg·kg^-1 per day) in 5-month-old mice that decreased osteoblastic activity and increased sclerostin and leptin levels. Furthermore, the synthetic glucocorticoid dexamethasone alters the anabolic Wnt signaling pathway. The Wnt pathway inhibitor sclerostin has several glucocorticoid response elements, and dexamethasone administration to osteoblastic cells induces sclerostin expression. Dexamethasone treatment of isolated bone marrow cells decreased bone nodule formation, whereas removal of sclerostin protected against this decrement in mineralization. Collectively, these findings suggest that bone loss associated with steroid-induced osteoporosis is a consequence of sclerostin-mediated restriction of Wnt signaling, which may mechanistically facilitate glucocorticoid toxicity in bone.

Corticosterone levels in relation to trace element contamination along an urbanization gradient in the common blackbird (Turdus merula)

In a rapidly urbanizing world, trace element pollution may represent a threat to human health and wildlife, and it is therefore crucial to assess both exposition levels and associated effects of trace element contamination on urban vertebrates. In this study, we investigated the impact of urbanization on trace element contamination and stress physiology in a wild bird species, the common blackbird (Turdus merula), along an urbanization gradient (from rural to moderately urbanized areas). Specifically, we described the contamination levels of blackbirds by 4 non-essential (Ag, Cd, Hg, Pb) and 9 essential trace elements (As, Co, Cr, Cu, Fe, Mn, Ni, Se, Zn), and explored the putative disrupting effects of the non-essential element contamination on corticosterone levels (a hormonal proxy for environmental challenges). We found that non-essential trace element burden (Cd and Pb specifically) increased with increasing urbanization, indicating a significant trace element contamination even in medium sized cities and suburban areas. Interestingly, the increased feather non-essential trace element concentrations were also associated with elevated feather corticosterone levels, suggesting that urbanization probably constrains birds and that this effect may be mediated by trace element contamination. Future experimental studies are now required to disentangle the influence of multiple urban-related constraints on corticosterone levels and to specifically test the influence of each of these trace elements on corticosterone secretion.

Behavioral effects induced by subchronic exposure to Pb and their reversion are concentration and gender dependent

Lead (Pb) seems to be involved in the etiology of psychological pathologies. This study investigated the effects of subchronic Pb exposure from weaning to adulthood on anxiety, depression and aggressiveness in male and female Swiss mice. Moreover, the reversibility of the effects was evaluated retesting the animals 30 days after the end of exposure. Swiss male and female mice (21 days) were exposed to 0, 50, 100 or 500 ppm of Pb, as Pb acetate, in drinking water for 70 days and were submitted to the forced swimming, tail suspension, elevated plus-maze or intruder—resident tests. Pb exposure to 50 and 500 ppm induced anti-depressant-like effect in both males and females, whereas exposure to 500 ppm induced anxiogenic effect only in males. Interruption of exposure was able to reverse the behavioral alterations in females, but not in males exposed to the highest concentration (500 ppm). Our results suggest that behavioral effects induced by subchronic exposure to Pb from weaning to adulthood and their reversion are concentration and gender dependent. [Human & Experimental Toxicology] (2007) 26, 733—739

Blood lead level and its association with body mass index and obesity in China - Results from SPECT-China study

We aimed to report environmental and blood lead level (BLL) in China, and investigate the relationship of BLL with body mass index (BMI) and obesity. 5558 subjects were enrolled from 16 sites in China. BLL was measured by atomic absorption spectrometry. Obesity was defined as BMI ≥ 30 kg/m². Median (interquartile range) of BLL was 44.00 μg/L (29.00–62.16) for men and 37.79 μg/L (25.13–54.35) for women, about twice higher than in U.S. population. Subjects in rural and high-economic-status areas had significantly greater BLL (P < 0.001). However, in these areas, the lead levels in drinking water, river water and rice were comparable to or significantly lower than those in urban and low-economic-status areas. After adjustment for age, urbanization, economic status and metabolic factors, BLL was independently associated with BMI in women (P for trend < 0.001), but not in men. In fully adjusted model, increased quartiles of BLL were associated with significantly increased odds ratios of obesity (P for trend < 0.01) in women. In conclusion, BLLs in Chinese adults were much higher than in developed countries. There was a sex-specific association between BLL and BMI. Elevated BLL does not appear to be associated with lead levels in drinking water or rice, suggesting some other exposure source.

The role of lead and cadmium in psychiatry

Psychiatric disorders are associated with long-term disability and huge social and economic costs. The possible influence of heavy metals exposure on public health remains a matter of concern. A recurring research question that persisted among researchers in neuropsychiatry has been “are psychiatric patients more likely to have a high body burden of lead or other heavy metals?” This is an update account on the role of lead and cadmium in psychiatry. This review, which has employed search words like “lead and cadmium in psychiatry”, “lead and cadmium in schizophrenia”, “lead and cadmium in psychosis” in citation indices such as PubMed, Google Scholar, Scirus, and Scopus. A total of 415 articles were found; 60 fulfiled the inclusion criteria. Evidence-based information suggests that lead and cadmium may be involved in psychiatry. Should environmental lead and cadmium be implicated in the etiogenesis of psychiatry given the characteristic high environmental pollution in Sub Sahara Africa, it is worthwhile for toxicologists and scientists in Sub-Sahara Africa to investigate if lead and cadmium can become additional biomarkers in the diagnosis of psychiatric disorders.

Sex-dependent impacts of low-level lead exposure and prenatal stress on impulsive choice behavior and associated biochemical and neurochemical manifestations

A prior study demonstrated increased overall response rates on a fixed interval (FI) schedule of reward in female offspring that had been subjected to maternal lead (Pb) exposure, prenatal stress (PS) and offspring stress challenge relative to control, prenatal stress alone, lead alone and lead+prenatal stress alone (Virgolini et al., 2008). Response rates on FI schedules have been shown to directly relate to measures of self-control (impulsivity) in children and in infants (Darcheville et al., 1992, 1993). The current study sought to determine whether enhanced effects of Pb±PS would therefore be seen in a more direct measure of impulsive choice behavior, i.e., a delay discounting paradigm. Offspring of dams exposed to 0 or 50ppm Pb acetate from 2 to 3 months prior to breeding through lactation, with or without immobilization restraint stress (PS) on gestational days 16 and 17, were trained on a delay discounting paradigm that offered a choice between a large reward (three 45mg food pellets) after a long delay or a small reward (one 45mg food pellet) after a short delay, with the long delay value increased from 0s to 30s across sessions. Alterations in extinction of this performance, and its subsequent re-acquisition after reinforcement delivery was reinstated were also examined. Brains of littermates of behaviorally-trained offspring were utilized to examine corresponding changes in monoamines and in levels of brain derived neurotrophic factor (BDNF), the serotonin transporter (SERT) and the N-methyl-d-aspartate receptor (NMDAR) 2A in brain regions associated with impulsive choice behavior. Results showed that Pb±PS-induced changes in delay discounting occurred almost exclusively in males. In addition to increasing percent long delay responding at the indifference point (i.e., reduced impulsive choice behavior), Pb±PS slowed acquisition of delayed discounting performance, and increased numbers of both failures to and latencies to initiate trials. Overall, the profile of these alterations were more consistent with impaired learning/behavioral flexibility and/or with enhanced sensitivity to the downshift in reward opportunities imposed by the transition from delay discounting training conditions to delay discounting choice response contingencies. Consistent with these behavioral changes, Pb±PS treated males also showed reductions in brain serotonin function in all mesocorticolimbic regions, broad monoamine changes in nucleus accumbens, and reductions in both BDNF and NMDAR 2A levels and increases in SERT in frontal cortex, i.e., in regions and neurotransmitter systems known to mediate learning/behavioral flexibility, and which were of greater impact in males. The current findings do not fully support a generality of the enhancement of Pb effects by PS, as previously seen with FI performance in females (Virgolini et al., 2008), and suggest a dissociation of the behaviors controlled by FI and delay discounting paradigms, at least in response to Pb±PS in rats. Collectively, however, the findings remain consistent with sex-dependent differences in the impacts of both Pb and PS and with the need to understand both the role of contingencies of reinforcement and underlying neurobiological effects in these sex differences.

A blunted anxiolytic like effect of curcumin against acute lead induced anxiety in rat: involvement of serotonin

Anxiety is one of the most common mental disorders sharing extreme or pathological anxiety states as the primary disturbance in mood or emotional tone, with increased fear and exaggerated acute stress responses. Medicinal plants are very variable, but some of them are used as a spice such as curcumin (Curcuma longa). Curcumin shows a wide range of pharmacological potentialities, however, little is known about its anxiolytic properties. The aim of our study was to assess the anti-anxiety potential of curcumin extract against experimental lead induced-anxiety in rats. Experiments were carried out on male Wistar rats intoxicated acutely with an intraperitoneal injection of Pb (25mg/kg B.W.) and/or concomitantly with administration of curcumin (30 mg/kg B.W.) for 3 days. Using immunohistochemistry and anxiety assessment tests (dark light box and elevated plus maze), we evaluated, respectively, the expression of serotonin (5HT) in the dorsal raphe nucleus (DRN) and the anxiety state in our animals. Our results showed, for the first time, a noticeable anxiolytic effect of curcumin against lead induced anxiety in rats and this may possibly result from modulation of central neuronal monoaminergic neurotransmission, especially serotonin, which has shown a significant reduction of the immunoreactivity within the DRN.

Blood lead level association with lower body weight in NHANES 1999-2006

BACKGROUND

Lead exposure is associated with low birth-weight. The objective of this study is to determine whether lead exposure is associated with lower body weight in children, adolescents and adults.

METHODS

We analyzed data from NHANES 1999-2006 for participants aged ≥3 using multiple logistic and multivariate linear regression. Using age- and sex-standardized BMI Z-scores, overweight and obese children (ages 3-19) were classified by BMI ≥85 th and ≥95 th percentiles, respectively. The adult population (age ≥20) was classified as overweight and obese with BMI measures of 25-29.9 and ≥30, respectively. Blood lead level (BLL) was categorized by weighted quartiles.

RESULTS

Multivariate linear regressions revealed a lower BMI Z-score in children and adolescents when the highest lead quartile was compared to the lowest lead quartile (β (SE)=-0.33 (0.07), p<0.001), and a decreased BMI in adults (β (SE)=-2.58 (0.25), p<0.001). Multiple logistic analyses in children and adolescents found a negative association between BLL and the percentage of obese and overweight with BLL in the highest quartile compared to the lowest quartile (OR=0.42, 95% CI: 0.30-0.59; and OR=0.67, 95% CI: 0.52-0.88, respectively). Adults in the highest lead quartile were less likely to be obese (OR=0.42, 95% CI: 0.35-0.50) compared to those in the lowest lead quartile. Further analyses with blood lead as restricted cubic splines, confirmed the dose-relationship between blood lead and body weight outcomes.

CONCLUSIONS

BLLs are associated with lower body mass index and obesity in children, adolescents and adults.

Allostatic load amplifies the effect of blood lead levels on elevated blood pressure among middle-aged U.S. adults: a cross-sectional study

BACKGROUND

Scientists and regulators have sought to understand whether and how physiologic dysregulation due to chronic stress exposure may enhance vulnerability to the adverse health effects of toxicant exposures. We conducted a cross-sectional study to determine whether allostatic load (AL), a composite measure of physiologic response to chronic exposure to stress, amplifies the effect of lead exposure on blood pressure among middle-aged adults.

METHODS

We analyzed associations between blood lead levels and blood pressure in a nationally representative sample of 8,194 U.S. adults (aged 40-65 years) participating in the National Health and Nutritional Examination Survey, 1999--2008. Outcomes were elevated systolic (≥ 140 mm Hg) and diastolic (≥ 90 mm Hg) blood pressure. AL was defined as the aggregate score of seven components, reflecting dysregulation of the cardiovascular, inflammatory, and endocrine systems.

RESULTS

Logistic regression models showed a linear dose-response relationship for quintiles of blood lead and elevated systolic blood pressure in the high AL group (p = 0.03) but not the low AL group (p = 0.24). Similarly, the relationship between lead exposure and elevated diastolic blood pressure was stronger among the high AL group than the low AL group. Within the high AL group, the fourth and fifth quintiles had significantly elevated odds of elevated blood pressure compared to lowest quintile [OR = 1.92, (95% CI, 1.07, 3.47) and OR =2.28 (95% CI, 1.33, 3.91), respectively]. In the low AL group, none of the quintile effects were significantly different than the referent group although there was evidence of a linear trend (p =0.03). The lead by AL interaction term was not statistically significant for either systolic or diastolic blood pressure models.

CONCLUSIONS

Results suggest that higher AL may amplify the adverse effects of lead on blood pressure. Future research should assess the implications of cumulative exposures to environmental and social stressors for regulatory decision-making.

Lead exposure and fear-potentiated startle in the VA Normative Aging Study: a pilot study of a novel physiological approach to investigating neurotoxicant effects

BACKGROUND

Physiologically-based indicators of neural plasticity in humans could provide mechanistic insights into toxicant actions on learning in the brain, and perhaps prove more objective and sensitive measures of such effects than other methods.

OBJECTIVES

We explored the association between lead exposure and classical conditioning of the acoustic startle reflex (ASR)-a simple form of associative learning in the brain-in a population of elderly men. Fifty-one men from the VA Normative Aging Study with cumulative bone lead exposure measurements made with K-X-Ray-Fluorescence participated in a fear-conditioning protocol.

RESULTS

The mean age of the men was 75.5years (standard deviation [sd]=5.9) and mean patella lead concentration was 22.7μg/g bone (sd=15.9). Baseline ASR eyeblink response decreased with age, but was not associated with subsequent conditioning. Among 37 men with valid responses at the end of the protocol, higher patella lead was associated with decreased awareness of the conditioning contingency (declarative learning; adjusted odds ratio [OR] per 20μg/g patella lead=0.91, 95% confidence interval [CI]: 0.84, 0.99, p=0.03). Eyeblink conditioning (non-declarative learning) was 0.44sd less (95% CI: -0.91, 0.02; p=0.06) per 20μg/g patella lead after adjustment. Each result was stronger when correcting for the interval between lead measurement and startle testing (awareness: OR=0.88, 95% CI: 0.78, 0.99, p=0.04; conditioning: -0.79sd less, 95% CI: -1.56, 0.03, p=0.04).

CONCLUSIONS

This initial exploration suggests that lead exposure interferes with specific neural mechanisms of learning and offers the possibility that the ASR may provide a new approach to physiologically explore the effects of neurotoxicant exposures on neural mechanisms of learning in humans with a paradigm that is directly comparable to animal models.

Effects of lactational and/or in utero exposure to environmental contaminants on the glucocorticoid stress-response and DNA methylation of the glucocorticoid receptor promoter in male rats

Perinatal events can reprogram the hypothalamo-pituitary-adrenal axis for the entire lifespan leading to abnormal glucocorticoid stress-response (GSR) in adulthood: a phenomenon reported to be mediated by changes in DNA methylation of the glucocorticoid receptor (GR) gene promoter. We examined whether in utero and/or lactational exposure to mixtures of environmental contaminants can also induce abnormal GSR during adulthood. The experiment included nine treatment groups. From gestation day (GD) 0 until postnatal day (PND) 20, dams were fed daily with a cookie laced with corn oil (control) or a chemical mixture (M) [polychlorinated biphenyls (PCBs), organochlorine pesticides, and methylmercury] at 0.5 or 1.0mg/kg/day (0.5M, and M). At birth, some control (C) and M litters were cross-fostered to create four groups with the following in utero/postnatal exposure: C/C, M/C, C/M, M/M. Other dams received 1.8ng/kg/day of a mixture of aryl hydrocarbon receptor (AhR) agonists (non-ortho PCBs, PC-dibenzodioxins and PC-dibenzofurans) without or with 0.5M (0.5MAhR). In adult male offspring the abundance of GR in treated groups was not different from the control, but the AhR and M groups were significantly different from each other with opposite effects in the hippocampus and liver. There was no change in DNA methylation of the GR promoter (exon-17 and -110). Abnormal GSRs were detected in the AhR, 0.5MAhR, CM, and MM groups. The literature associates abnormal GSR with metabolic and mental health impairments, thus these results support further investigation of the influence of developmental exposure to environmental contaminants and predisposition to stress-induced diseases.

Alteration in plasma corticosterone levels following long term oral administration of lead produces depression like symptoms in rats

Lead toxicity is known to induce a broad range of physiological, biochemical and behavioral dysfunctions that may result in adverse effects on several organs, including the central nervous system. Long-term exposure to low levels of lead (Pb(2+)) has been shown to produce behavioral deficits in rodents and humans by affecting hypothalamic-pituitary-adrenal (HPA) axis. These deficits are thought to be associated with altered brain monoamine neurotransmission and due to changes in glucocorticoids levels. This study was designed to investigate the effects of Pb(2+)exposure on growth rate, locomotor activity, anxiety, depression, plasma corticosterone and brain serotonin (5-HT) levels in rats. Rats were exposed to lead in drinking water (500 ppm; lead acetate) for 5 weeks. The assessment of depression was done using the forced swimming test (FST). Estimation of brain 5-HT was determined by high-performance liquid chromatography with electrochemical detection. Plasma corticosterone was determined by spectrofluorimetric method. The present study showed that long term exposure to Pb(2+) significantly decreased the food intake followed by the decrease in growth rate in Pb(2+)exposed rats as compared to control group. No significant changes in open field activity were observed following Pb(2+)exposure while significant increase in anxiogenic effect was observed. Increased plasma corticosterone and decreased 5-HT levels were exhibited by Pb(2+)exposed rats as compared to controls. A significant increase in depressive like symptoms was exhibited by Pb(2+)exposed rats as compared to control rats. The results are discussed in the context of Pb(2+) inducing a stress-like response in rats leading to changes in plasma corticosterone and brain 5-HT levels via altering tryptophan pyrrolase activity.