Associations of Short-Term Exposure to Fine Particulate Matter with Neural Damage Biomarkers: A Panel Study of Healthy Retired Adults

Associations among blood heavy metals, neurofilament light chains and cognition function in US adults: NHANES 2013-2014

BACKGROUND

Heavy metals could induce neurotoxicity, leading to cognitive function and motor deficiencies. Serum neurofilament light chain (sNfL) is a promising biomarker for neurological injury, and it may indicate nerve damage from heavy metals exposure. However, there's limited research exploring the associations among heavy metals, sNfL, and cognitive function in adults, and the existing findings are inconsistent.

OBJECTIVE

959 participants were enrolled from the National Health and Nutrition Examination Surveys (NHANES) 2013-2014. This study was aimed to investigate the possible associations among heavy metals, sNfL, and cognitive function in adults.

METHODS

We utilized data from the National Health and Nutrition Examination Survey (NHANES) 2013-2014, comprising 959 participants. Heavy metals were detected in blood samples including lead (Pb), cadmium (Cd), mercury (Hg), manganese (Mn), and selenium (Se), with measurements taken using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technology. The level of sNfL was quantified via an innovative high-throughput immunoassay technology developed by Siemens Healthineers. Cognitive function were assessed using the Animal Fluency Test (AFT), the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), and the Digit Number Symbol Substitution Test (DSST). Additionally, generalized linear models (GLMs), weighted quantile sum regression (WQS), Bayesian kernel machine regression (BKMR), quantile-based g computation (qgcomp), and restricted cubic splines (RCS) analyses were employed to examine the associations between heavy metals exposure and sNfL level. Finally, a mediation analysis to explore the interaction among heavy metals, sNfL, and cognitive function in adults aged 60 and above.

RESULTS

The generalized linear models exhibited a positive correlation between blood Pb or Cd levels and sNfL (β = 0.14, 95 % CI: 0.08-0.20; β = 0.14, 95 % CI: 0.07-0.20), in total population. Both WQS and BKMR analysis consistently showed a strong correlation between higher levels of the blood heavy metals mixture and increased sNfL (OR=0.051, 95 %CI: 0.025-0.090). The qgcomp model indicated that Cd had a significant positive correlation with sNfL, while Mn and Se showed a significant negative correlation with sNfL. Moreover, we have identified a significant relationship between sNfL or Cd and cognitive function scores (AFT, DSST) in adults aged 60 and above. The mediation analysis further revealed that sNfL partially mediated the relationship between Cd and AFT or DSST scores, with interpretive efficiencies of 23.35 % and 32.7 %, respectively.

CONCLUSION

This study is the first to utilize sNfL data to establish a link between heavy metals exposure and cognitive function. The finding highlight the the positive correlation between Pb or Cd and sNfL, the negative correlation between Se and sNfL. The impact of Cd exposure on cognitive function in individuals older than 60 was partially explained by sNfL. Further investigations are required to validate these findings, considering the constraints of the NHANES study.

Particulate matter 2.5 (PM2.5) - associated cognitive impairment and morbidity in humans and animal models: a systematic review

Particulate matter with an aerodynamic diameter of less than 2.5 µm (PM2.5) is one of the criteria air pollutants that (1) serve as an essential carrier of airborne toxicants arising from combustion-related events including emissions from industries, automobiles, and wildfires and (2) play an important role in transient to long-lasting cognitive dysfunction as well as several other neurological disorders. A systematic review was conducted to address differences in study design and various biochemical and molecular markers employed to elucidate neurological disorders in PM2.5 -exposed humans and animal models. Out of 340,068 scientific publications screened from 7 databases, 312 studies were identified that targeted the relationship between exposure to PM2.5 and cognitive dysfunction. Equivocal evidence was identified from pre-clinical (animal model) and human studies that PM2.5 exposure contributes to dementia, Parkinson disease, multiple sclerosis, stroke, depression, autism spectrum disorder, attention deficit hyperactivity disorder, and neurodevelopment. In addition, there was substantial evidence from human studies that PM2.5 also was associated with Alzheimer's disease, anxiety, neuropathy, and brain tumors. The role of exposome in characterizing neurobehavioral anomalies and opportunities available to leverage the neuroexposome initiative for conducting longitudinal studies is discussed. Our review also provided some areas that warrant consideration, one of which is unraveling the role of microbiome, and the other role of climate change in PM2.5 exposure-induced neurological disorders.

Association between chronic PM2.5 exposure and neurodegenerative biomarkers in adults from critically polluted area

BACKGROUND

Air pollution is a significant public health concern, increasingly recognized for its association with adverse health outcomes including neurodegenerative and neuroinflammatory conditions. The present study aimed to characterize plasma levels of key biomarkers related to neurodegeneration and neuroinflammation among middle-aged to elderly adults living in areas designated as critically polluted.

METHODS

A total of 202 adults, aged 41 to 60 years, residing in CPA (CEPI > 70) for over ten years were recruited in the study. The exposures of air pollutant were measured as per the established protocols by CPCB. The plasma levels of neurodegenerative markers (Aβ(1-42), Total τ, α-Synuclein, BDNF and GFAP) were estimated using commercially available ultra-sensitive ELISA kits. The data analysis was performed through mean and standard deviation, percentile distribution and multivariate logistic regression using SPSS 26.0.

RESULTS

This study confirmed the elevated PM2.5 levels at the study location exceeding the regulatory limits. Women exhibited relatively higher Amyloid Aβ(1-42), α-Synuclein and GFAP levels, while men exhibited relatively higher Total τ, & BDNF levels. Further, older participants (aged 50 - 60 years) exhibited higher levels of all markers but α-Synuclein, as compared to the younger peers (aged 40 - 50 years). A weak positive trend (p = 0.08) was observed for α-Synuclein with prolonged exposure.

CONCLUSION

This study is among the first community-based investigations in India to assess plasma levels of neurodegenerative and neuroinflammatory biomarkers in apparently healthy adults chronically exposed to high ambient air pollution. By integrating chronic exposure data from a Critically Polluted Area (CEPI > 70) with biomarker profiling, the study offers early insights into potential neurobiological alterations associated with environmental pollutants, highlighting sex- and age-specific vulnerabilities. These findings emphasize the importance of considering environmental influences in neurodegenerative disease research and the potential need for tailored health interventions.

Five-month real-ambient PM2.5 exposure impairs learning in Brown Norway rats: Insights from multi omics-based analysis

PM2.5, recognized as a potential pathogenic factor for nervous system diseases, remains an area with many unknowns, particularly regarding its effects on human health. After five-month real-ambient PM2.5 exposure, we observed no significant pathological damage to the lung, liver, spleen, or kidney tissues. However, PM2.5 exposure led to neuronal degeneration in the hippocampal CA1 region of Brown Norway (BN) rats. The level of IL-6, IL-13, IL-1β, IL-12, IL-4, GRO/KC, MIP-1α, CM-CSF significantly increased in lung lavage fluid (P < 0.05 for all). Notably, we detected a slight impairment in spatial learning ability, as evidenced by the Barnes maze training outcomes. There were no significant changes in the bacterial community in lung lavage fluid (P = 0.621), but the bacterial community in the gut significantly changed (P < 0.001), with more species identified (P < 0.05). The metabolomic analysis revealed 147 and 149 significantly changed metabolites in the pulmonary system and serum, respectively (P < 0.05). PM2.5 exposure caused a decrease in Nervonic acid (NA) in both the lung and serum, which likely contributed to spatial learning impairment (P < 0.01). The correlation between lung metabolites, gut bacterial species, and serum metabolites indicated that PM2.5 exposure likely impaired spatial learning through the lung-gut-brain axis pathway. Lung and serum metabolic disorders and intestinal microbial imbalance occurred in BN rats post-five-month real-ambient PM2.5 exposure. There were two potential ways that PM2.5 exposure caused the decline of spatial learning ability in wild-type BN rats: (1) PM2.5 exposure led to a significant decrease of neuroprotective Nervonic acid in lung and serum metabolites. (2) PM2.5 exposure likely led to reduced spatial learning ability through the lung-gut-brain axis.

Association of aging acceleration with serum neurofilament light chain levels: Implications for the roles of modifiable aging factors

INTRODUCTION

Neurofilament light chain (NfL) is a specific biomarker of neuroaxonal damage and related neurodegenerative diseases. Aging acceleration, which reflects the impact of modifiable factors on the aging process, is increasingly recognized for its relevance. While normal aging is known to contribute substantially to neuroaxonal damage and many neurodegenerative diseases, the effects of aging acceleration warrant further investigation. This study aimed to investigate the association and causality between aging acceleration and serum NfL levels.

METHODS

We conducted a cross-sectional study involving 1695 adult participants from NHANES 2013-2014 to evaluate the association, dose-response relationship, and interaction network between aging acceleration and serum NfL levels. And we used Mendelian randomization (MR) to assess the causal effects between serum NfL levels and aging acceleration.

RESULTS

Significant positive associations were observed between aging acceleration and serum NfL levels. In linear regression, the regression coefficients were 0.016 (95 % CI: 0.011-0.021) for biological age acceleration and 0.020 (95 % CI: 0.012-0.028) for phenotypic age acceleration. In logistic regression, the odds ratios were 1.052 (95 % CI: 1.029-1.076) and 1.093 (95 % CI: 1.064-1.123), respectively. Restricted cubic spline regression identified significant positive dose-response relationships, and bidirectional MR analyses demonstrated forward causal effects.

CONCLUSION

Our study indicates that aging acceleration is significantly associated with serum NfL levels, with higher levels of aging acceleration linked to an increased risk of neuroaxonal damage. These findings provide robust evidence that aging acceleration affects the risk of neuroaxonal damage and highlight the importance of modifiable aging factors.

Metal mixtures exposure with risk of elevated serum neurofilament light chain concentrations in U.S. general adults, NHANES 2013-2014

BACKGROUND

A relatively well-established link was observed between metal mixtures exposure and neurodegenerative diseases. However, the relationship between metal mixtures exposure and serum neurofilament light chain (sNfL) concentrations, a valuable non-invasive biomarker of neurodegenerative diseases, in general adult populations remains understudied and unclear.

OBJECTIVE

This study seeks to elucidate the potential impact of metal mixtures exposure on sNfL concentrations in a representative sample of U.S. general adults.

METHODS

Twelve urinary metal levels, including barium (Ba), cadmium (Cd), cobalt (Co), cesium (Cs), molybdenum (Mo), lead (Pb), antimony (Sb), tin (Sn), strontium (Sr), thallium (Tl), tungsten (W) and uranium (U), were analyzed in U.S. general adults recruited from the 2013-2014 National Health and Nutrition Examination Survey using inductively coupled plasma mass spectrometry (ICP-MS) after a simple dilution step. Urine samples are diluted with 2 % concentrated nitric acid (1:9). We employed a two-pronged approach, combining weighted quantile sum (WQS) and Bayesian kernel machine regression (BKMR) models, to examine the association between the multiple-metals effect and sNfL concentrations. Survey-weighted multivariate linear regression was used to explore the correlation between single-metal effect and sNfL concentrations.

RESULTS

With the increasing quartiles of log-transformed sNfL (log-sNfL) concentrations, the fourth quartile had a higher proportion of smokers and hypertensive individuals (P < 0.001). Cd (69.6 %) and Pb (8.9 %) were the primary drivers of the association between metal mixtures exposure and sNfL concentrations. Analysis of WQS and BKMR models showed a positive association between metal mixtures exposure and sNfL concentrations, especially in older, and male participants.

CONCLUSION

In the U.S. general adult, a significant correlation between metal mixtures exposure and increased sNfL concentrations was observed, and urinary Cd levels play a pivotal role in this positive correlation. Notably, stronger risk associations were observed among elderly, males, smokers, and hypertensive individuals. The results could be significant for detecting and tracking the beginning of neurodegenerative diseases early, as well as helping to pinpoint individuals at high risk.

Sex-specific associations of per- and polyfluoroalkyl substances with brain-derived neurotrophic factors (BDNF) in cord serum

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) is perceived as an emerging environmental endocrine disruptor, which have been linked to children neurodevelopment. However, the potential mechanisms are not clear. Brain-derived neurotrophic factor (BDNF) is a vital protein in neurodevelopment, and the associations between PFAS exposure and BDNF require exploration.

OBJECTIVE

We aimed to explore the relationships between PFAS exposure and the levels of BDNF in cord serum.

METHODS

A total of 1,189 mother-infant dyads from the Sheyang Mini Birth Cohort Study (SMBCS) were enrolled. The levels of 12 PFAS and BDNF were measured in cord serum. We utilized generalized linear models (GLMs), quantile-based g-computation (QGC) models, and Bayesian Kernel Machine Regression (BKMR) models to explore the relationships between single and mixed PFAS exposure and BDNF concentration. Additionally, the potential sex differences were explored by sex-stratified analysis.

RESULTS

Median concentrations of the included 10 PFAS ranged from 0.04 to 3.97 μg/L. In the single chemical models, four PFAS congeners, namely perfluorononanoic acid (PFNA), perfluorooctane sulfonic acid (PFOS), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), were negatively associated with BDNF levels in cord serum among females only (β: -0.116 to -0.062, p < 0.05). In the BKMR models of total mother-infant dyads and female fetuses, the significant negative relationships between PFAS mixtures and BDNF were observed, and PFUnDA was identified as an important contributor (Posterior inclusion probability, PIP = 0.8584 for the total subjects; PIP = 0.8488 for the females). PFOS was another important driver based on the mixture approaches.

CONCLUSIONS

We found that PFNA, PFOS, PFDA, and PFUnDA were associated with decreased BDNF concentration in the females, although the causal inference might be limited. PFAS mixtures were also negatively linked with BDNF levels in the total mother-infant pairs and female fetuses. The adverse effect of PFAS exposure on fetal BDNF levels might be sex-specific.

Long-term exposure to PM2.5 compositions and O3 and their interactive effects on DNA methylation of peripheral brain-derived neurotrophic factor promoter

This study examined the associations of long-term exposure to ambient fine particulate matter (PM2.5) compositions/ozone with methylation of peripheral brain-derived neurotrophic factor (BDNF) promoters. A total of 101 participants were recruited from a cohort in Shijiazhuang, Hebei province, China. They underwent baseline and follow-up surveys in 2011 and 2015. DNA methylation levels were detected by bisulfite-PCR amplification and pyrosequencing. Participants' three-year average levels of PM2.5 compositions and ozone were estimated. Bayesian kernel machine regression (BKMR) models were used to examine the joint effects of pollutants on methylation levels. Exposure to PM2.5 compositions and ozone mixtures at the 75th percentile was associated with increased methylation levels at CpG2 of BDNF promoter (203%, 95% CI: 89, 316) than the lowest level of exposure, and sulfate dominated the effect in the BKMR models.Our findings provide clues to the epigenetic mechanisms for the associations of PM2.5 compositions and ozone with BDNF.

Neurotoxicity of fine and ultrafine particulate matter: A comprehensive review using a toxicity pathway-oriented adverse outcome pathway framework

Fine particulate matter (PM2.5) can cause brain damage and diseases. Of note, ultrafine particles (UFPs) with an aerodynamic diameter less than or equal to 100 nm are a growing concern. Evidence has suggested toxic effects of PM2.5 and UFPs on the brain and links to neurological diseases. However, the underlying mechanism has not yet been fully illustrated due to the variety of the study models, different endpoints, etc. The adverse outcome pathway (AOP) framework is a pathway-based approach that could systematize mechanistic knowledge to assist health risk assessment of pollutants. Here, we constructed AOPs by collecting molecular mechanisms in PM-induced neurotoxicity assessments. We chose particulate matter (PM) as a stressor in the Comparative Toxicogenomics Database (CTD) and identified the critical toxicity pathways based on Ingenuity Pathway Analysis (IPA). We found 65 studies investigating the potential mechanisms linking PM2.5 and UFPs to neurotoxicity, which contained 2, 675 genes in all. IPA analysis showed that neuroinflammation signaling and glucocorticoid receptor signaling were the common toxicity pathways. The upstream regulator analysis (URA) of PM2.5 and UFPs demonstrated that the neuroinflammation signaling was the most initially triggered upstream event. Therefore, neuroinflammation was recognized as the MIE. Strikingly, there is a clear sequence of activation of downstream signaling pathways with UFPs, but not with PM2.5. Moreover, we found that inflammation response and homeostasis imbalance were key cellular events in PM2.5 and emphasized lipid metabolism and mitochondrial dysfunction, and blood-brain barrier (BBB) impairment in UFPs. Previous AOPs, which only focused on phenotypic changes in neurotoxicity upon PM exposure, we for the first time propose AOP framework in which PM2.5 and UFPs may activate pathway cascade reactions, resulting in adverse outcomes associated with neurotoxicity. Our toxicity pathway-based approach not only advances risk assessment for PM-induced neurotoxicity but shines a spotlight on constructing AOP frameworks for new chemicals.

Potential Early Effect Biomarkers for Ambient Air Pollution Related Mental Disorders

Air pollution is one of the greatest environmental risks to health, with 99% of the world's population living where the World Health Organization's air quality guidelines were not met. In addition to the respiratory and cardiovascular systems, the brain is another potential target of air pollution. Population- and experiment-based studies have shown that air pollution may affect mental health through direct or indirect biological pathways. The evidence for mental hazards associated with air pollution has been well documented. However, previous reviews mainly focused on epidemiological associations of air pollution with some specific mental disorders or possible biological mechanisms. A systematic review is absent for early effect biomarkers for characterizing mental health hazards associated with ambient air pollution, which can be used for early warning of related mental disorders and identifying susceptible populations at high risk. This review summarizes possible biomarkers involved in oxidative stress, inflammation, and epigenetic changes linking air pollution and mental disorders, as well as genetic susceptibility biomarkers. These biomarkers may provide a better understanding of air pollution's adverse effects on mental disorders and provide future research direction in this arena.

Association between volatile organic compounds and serum neurofilament light chain in US adults

OBJECTIVE

This study aimed to investigate the associations between exposure to blood volatile organic compounds (VOCs) and the level of serum neurofilament light chain (NfL) in adults.

METHODS

We analyzed data from the 2013-2014 National Health and Nutrition Examination Survey (NHANES), including 2008 participants aged 20 to 75 years old. Multiple linear regression models were used to examine the associations between 28 VOCs and NfL after adjusting for multiple potential confounders. Restricted cubic spline (RCS) was used to examine the potential non-linear associations.

RESULTS

The linear regression models showed that higher levels of 2,5-dimethylfuran (β = 0.042, 95 % confidence interval [CI]: 0.001, 0.096), ethyl acetate (β = 0.118, 95 % CI = 0.008, 0.304), and m-/p-xylene (β = 0.043, 95%CI = 0.012, 0.074) were associated with higher NfL levels. These estimates were largely consistent after adjusting for multiple confounders.

CONCLUSION

The findings of our study suggest a potential association between certain volatile organic compounds (2,5-dimethylfuran, ethyl acetate, and m-/p-xylene) and blood NfL levels, implying that they may have a role in revealing neurodegeneration and influencing neurological health.

Brain-derived neurotrophic factor (BDNF): an effect biomarker of neurodevelopment in human biomonitoring programs

The present narrative review summarizes recent findings focusing on the role of brain-derived neurotrophic factor (BDNF) as a biomarker of effect for neurodevelopmental alterations during adolescence, based on health effects of exposure to environmental chemical pollutants. To this end, information was gathered from the PubMed database and the results obtained in the European project Human Biomonitoring for Europe (HBM4EU), in which BDNF was measured at two levels of biological organization: total BDNF protein (serum) and BDNF gene DNA methylation (whole blood) levels. The obtained information is organized as follows. First, human biomonitoring, biomarkers of effect and the current state of the art on neurodevelopmental alterations in the population are presented. Second, BDNF secretion and mechanisms of action are briefly explained. Third, previous studies using BDNF as an effect biomarker were consulted in PubMed database and summarized. Finally, the impact of bisphenol A (BPA), metals, and non-persistent pesticide metabolites on BDNF secretion patterns and its mediation role with behavioral outcomes are addressed and discussed. These findings were obtained from three pilot studies conducted in HBM4EU project. Published findings suggested that exposure to some chemical pollutants such as fine particle matter (PM), PFAS, heavy metals, bisphenols, and non-persistent pesticides may alter circulating BDNF levels in healthy population. Therefore, BDNF could be used as a valuable effect biomarker to investigate developmental neurotoxicity of some chemical pollutants.

Short-term effects of ambient PM1, PM2.5, and PM10 on internal metal/metalloid profiles in older adults: A distributed lag analysis in China

There is limited evidence linking exposure to ambient particulate matter (PM) with internal doses of metals and metalloids (metal(loid)s). This study aimed to evaluate the effects of short-term exposure to ambient PM on urine metal(loid)s among Chinese older adults. Biological monitoring data of 15 urine metal(loid)s collected in 3, 970 community-dwelling older adults in Fuyang city, Anhui Province, China, from July to September 2018, were utilized. PMs with an aerodynamic diameter ≤ 1 µm (PM1), ≤ 2.5 µm (PM2.5), and ≤ 10 µm (PM10) up to eight days before urine collection were estimated by space-time extremely randomized trees (STET) model. Residential greenness was reflected by Normalized Difference Vegetation Index (NDVI). We used generalized additive model (GAM) combined with distributed lag linear/non-linear models (DLMs/DLNMs) to estimate the associations between short-term PM exposure and urine metal(loid)s. The results suggested that the cumulative exposures to PM1, PM2.5, or PM10 over two days (lag0-1 days) before urine collection were associated with elevated urine metal(loid)s in DLMs, while exhibited linear or "inverted U-shaped" relationships with seven urine metal(loid)s in DLNMs, including Gallium (Ga), Arsenic (As), Aluminum (Al), Magnesium (Mg), Calcium (Ca), Uranium (U), and Barium (Ba). Aforementioned results indicated robust rather than spurious associations between PMs and these seven metal(loid)s. After standardizations for three PMs, PM1 was the greatest contributor to U, PM2.5 made the greatest contributions to Ga, As, Al, and Ba, and PM10 contributed the most to Mg and Ca. Furthermore, the effects of three PMs on urine Ga, As, Al, Mg, Ca, and Ba were reduced when exposed to higher levels of NDVI. Overall, short-term exposures to ambient PMs contribute to elevated urinary metal(loid) levels in older adults, and three PMs exhibit various contributions to different urine metal(loid)s. Moreover, residential greenness may attenuate the effects of PMs on urine metal(loid)s.

Association between air pollutant exposure, body water distribution and sleep disorder indices in individuals with low-arousal-threshold obstructive sleep apnoea

BACKGROUND

Air pollution may alter body water distribution, it may also be linked to low-arousal-threshold obstructive sleep apnoea (low-ArTH OSA). Here, we explored the mediation effects of air pollution on body water distribution and low-ArTH OSA manifestations.

METHODS

In this retrospective study, we obtained sleep centre data from healthy participants and patients with low-ArTH OSA (N=1924) in northern Taiwan. Air pollutant exposure at different time intervals (1, 3, 6 and 12 months) was estimated using the nearest station estimation method, and government air-quality data were also obtained. Regression models were used to assess the associations of estimated exposure, sleep disorder indices and body water distribution with the risk of low-ArTH OSA. Mediation analysis was performed to explore the relationships between air pollution, body water distribution and sleep disorder indices.

RESULTS

First, exposure to particulate matter (PM) with a diameter of ≤10 µm (PM10) for 1 and 3 months and exposure to PM with a diameter of ≤2.5 µm (PM2.5) for 3 months were significantly associated with the Apnoea-Hypopnoea Index (AHI), Oxygen Desaturation Index (ODI), Arousal Index (ArI) and intracellular-to-extracellular water ratio (I-E water ratio). Significant associations were observed between the risk of low-ArTH OSA and 1- month exposure to PM10 (OR 1.42, 95% CI 1.09 to 1.84), PM2.5 (OR 1.33, 95% CI 1.02 to 1.74) and ozone (OR 1.27, 95% CI 1.01 to 1.6). I-E water ratio alternation caused by 1-month exposure to PM10 and 3-month exposure to PM2.5 and PM10 had partial mediation effects on AHI and ODI.

CONCLUSION

Air pollution can directly increase sleep disorder indices (AHI, ODI and ArI) and alter body water distribution, thus mediating the risk of low-ArTH OSA.

Maternal exposure to fine particulate matter and brain-derived neurotrophic factor (BDNF) in the fetus: A prospective cohort study

Maternal exposure to ambient fine particulate matter (PM_2.5) during pregnancy has been associated with impaired neurobehavioral development in children. However, the specific mechanism remains unclear. Brain derived neurotrophic factor (BDNF) is an important growth factor in the nervous system. We evaluated the associations of maternal PM_2.5 exposures with fetal BDNF in the umbilical cord blood in a prospective cohort study. A total of 711 eligible mother-infant pairs from the Shanghai Birth Cohort were included in the current study. Daily maternal exposures to ambient PM_2.5 were assessed with a gap-filling approach at 1 * 1 km² resolution based on self-reported home addresses. The concentrations of BDNF in the cord blood were measured by ELISA. A linear regression model was applied to evaluate the association of maternal ambient PM_2.5 exposure with fetal BDNF level at birth. The median concentration of BDNF was 13,403 pg/ml. Vaginal deliveries and female infants had higher BDNF levels than cesarean deliveries and male infants. One natural log (ln) unit increase in maternal PM_2.5 exposure during the second trimester was significantly associated with - 0.20 (95% CI: -0.36, -0.05) ln-unit decrease in BDNF level in all births. These effects were stronger and more significant in vaginal deliveries and in male infants. Our study suggests that BDNF in the cord blood may serve as a potential biomarker in assessing the neurodevelopmental effects of maternal PM_2.5 exposure.

Associations between multiple heavy metals exposure and neural damage biomarkers in welders: A cross-sectional study

BACKGROUND

Both occupational and environmental exposure to heavy metals are associated with various neurodegenerative diseases. However, limited evidence is available on the potential effects of exposure to metallic mixtures and neural damage.

OBJECTIVES

This study aimed to evaluate the association between metal mixtures in urine and neural damage biomarkers in welders.

METHODS

In this cross-sectional study, a total of 186 workers were recruited from steel mills. Twenty-three metals in urine were measured by inductively coupled plasma mass spectrometry. Serum neural damage biomarkers, including neurofilament light chain (NfL), sphingosine-1-phosphate (S1P), prolactin (PRL), and dopamine (DA) were detected using enzyme-linked immunosorbent assay kits. Multivariable linear regression, Bayesian kernel machine regression (BKMR), and Quantile g-computation (QG-C) were employed to estimate the association between metals exposure and neural damage biomarkers.

RESULTS

Inverted u-shaped associations of nickel with NfL, S1P, and DA were observed in the BKMR model. A non-linear relationship was also found between Fe and PRL. Urinary cobalt was positively associated with serum PRL and had the strongest positive weights in the QG-C model. Urinary lead was associated with higher serum S1P levels. We also found the interaction among nickel, zinc, arsenic, strontium, iron, and lead with the neural damage biomarkers.

CONCLUSION

This study provides new evidence of a direct association between metal mixture exposure and the serum biomarkers of neural damage. Several metals Ni, Co, Pb, Sr, As and Fe, may have adverse effects on the nervous system, while Zn may have neuroprotective effects.

Effects of differential regional PM2.5 induced hepatic steatosis and underlying mechanism

Emerging evidence suggests that exposure to PM_2.5 is associated with a high risk of nonalcoholic fatty liver disease (NAFLD). NAFLD is typically characterised by hepatic steatosis. However, the underlying mechanisms and critical components of PM_2.5-induced hepatic steatosis remain to be elucidated. In this study, ten-month-old C57BL/6 female mice were exposed to PM_2.5 from four cities in China (Taiyuan, Beijing, Hangzhou, and Guangzhou) via oropharyngeal aspiration every other day for four weeks. After the exposure period, hepatic lipid accumulation was evaluated by biochemical and histopathological analyses. The expression levels of genes related to lipid metabolism and metabolomic profiles were assessed in the mouse liver. The association between biomarkers of hepatic steatosis (hepatic Oil Red O staining area and serum and liver triglyceride contents) and typical components of PM_2.5 was identified using Pearson correlation analysis. Oil Red O staining and biochemical results indicated that PM_2.5 from four cities significantly induced hepatic lipid accumulation. The most severe hepatic steatosis was observed after Guangzhou PM_2.5 exposure. Moreover, Guangzhou PM_2.5-induced the most significant changes in gene expression associated with lipid metabolism, including increased hepatic fatty acid uptake and lipid droplet formation and decreased fatty acid synthesis and lipoprotein secretion. Contemporaneously, exposure to Guangzhou PM_2.5 significantly perturbed hepatic lipid metabolism. According to metabolomic analysis, disturbed hepatic lipid metabolism was primarily concentrated in linoleic acid, α-linoleic acid, and arachidonic acid metabolism. Finally, correlation analysis revealed that copper (Cu) and other inorganic components, as well as the majority of polycyclic aromatic hydrocarbons (PAHs), were related to changes in biomarkers of hepatic steatosis. These findings showed that PM_2.5 exposure caused hepatic steatosis in aged mice, which could be related to the critical chemical components of PM_2.5. This study provides critical information regarding the components of PM_2.5, which cause hepatic steatosis.

Auto repair workers exposed to PM2.5 particulate matter in Barranquilla, Colombia: telomere length and hematological parameters

Exposure to 2.5 µm particulate matter (PM_2.5) in automotive repair shops is associated with risks to health. We evaluated the effects of occupational exposure to PM_2.5 among auto repair-shop workers. Blood and urine samples were collected from 110 volunteers from Barranquilla, Colombia: 55 active workers and 55 controls. PM_2.5 concentrations were assessed at each of the sampling sites and chemical content was analyzed by SEM-EDS electron microscopy. The biological samples obtained were peripheral blood (hematological profiling, DNA extraction) and urine (malondialdehyde concentration). Telomere length was assessed by qPCR and polymorphisms in the glutathione transferase genes GSTT1 and GSTM1 by PCR-RFLP, with confirmation by allelic exclusion. White blood cell (WBC), lymphocyte (LYM%) and platelet (PLT) counts and the malondialdehyde concentration were higher (4.10 ± 0.93) in the exposed group compared to the control group (1.56 ± 0.96). TL was shorter (5071 ± 891) in the exposed individuals compared to the control group (6271 ± 805). White blood cell (WBC) and platelet counts were positively associated with exposure. Age and TBARS were correlated with TL in exposed individuals. The GSTT1 gene alleles were not in Hardy-Weinberg (H-W) equilibrium. The GSTM1 gene alleles were in H-W equilibrium and allelic exclusion analysis confirmed the presence of heterozygous GSTM1 genotypes. SEM-EDS analysis showed the presence of potentially toxic elements, including Mg, Al, Fe, Mn, Rh, Zn, and Cu. Auto repair shop workers showed effects that may be associated with exposure to mixtures of pollutants present in PM_2.5. The GSTM1 and GSTT1 genes had independent modulatory effects.

Chronic exposure to indoor air pollutants in association with attention-deficit/hyperactivity disorder symptoms in Chinese schoolchildren: A cross-sectional study

BACKGROUND

While increasing studies confirmed the adverse effects of indoor air pollution (IAP) on cardiopulmonary systems, less is known about the impact of IAP on child's brain.

OBJECTIVE

To explore the associations between multiple indoor air pollutants exposures and attention-deficit/hyperactivity disorder (ADHD) symptoms in Chinese schoolchildren.

METHODS

We invited 8630 individuals aged 6-12 years from an ongoing school-based cohort study across Guangzhou from April to May 2019. There are 7495 and 7245 children were respectively evaluated on the parent- and teacher-rated Conner's Rating Scale-Revised, and 7087 children were assessed on both versions. Indoor air pollutants exposures including cooking oil fumes, incense burning, home renovation, and secondhand smoke, were measured using a questionnaire reported by parents and children, and further converted into an index. Generalized linear mixed-effects models were performed to evaluate the associations between indoor air pollutants exposures and ADHD index and the presence of ADHD symptoms.

RESULTS

As reported by parents, 321 (4.3%) children had ADHD symptoms. Each of the four pollutants was positively associated with higher ADHD index and higher odds of ADHD symptoms. Children exposed to 1, 2, and ≥ 3 types of indoor air pollutants had higher ADHD index and higher odds of ADHD symptoms than those non-exposed children. For parent-reported ADHD symptoms, the odds ratios ranged from 1.24 [95% confidence interval (CI): 0.92-1.67] to 2.73 (95% CI: 1.86-4.01). These associations were consistent in parent- and teacher-reported ADHD symptoms, and the combination of both.

CONCLUSION

Indoor air pollutants exposures were positively associated with higher prevalence of children's ADHD symptoms assessed by whether parents or teachers.

Time-resolved dynamic disability adjusted life-years estimation

The quantification of how healthy the indoor air is, is a complex issue comprising of a large number of contaminants of various sources. The health implication of exposure to each of the contaminant deemed of importance can be expressed using Disability Adjusted Life Years (DALYs). The sum of all DALYs indicates how harmful the indoor air was during the investigated time-frame. This metric was originally developed by the World Bank and the WHO. In 2012, Logue et. al described two methods to estimate the DALYs related to exposure to contaminants in the indoor air based on the yearly mean exposure concentration of a population. The downside of these methods is that, when detailed exposure concentration profiles are available the method results in a loss of information. A novel method was developed to estimate DALYs originating from exposure to indoor pollutants that can be used for time-resolved exposure concentration data without this loss of information: Dynamic DALYs. The advantage of this method is that it can be calculated in real-time and for short or long periods of data. As such it can be used for pin-pointing problematic events in the exposure profile of a person and, as it can be calculated in real-time, makes it a candidate for use in automated optimization problems. The use of Dynamic DALYs is demonstrated for a simulation case-study of an occupied apartment. One continuously ventilated system (Dcont) and one smart ventilation system (Dsmart) are compared. Sources of typically indoor generated Volatile Organic Compounds (VOCs) were added and the related exposure profile and Dynamic DALY results of the working adult were analyzed. The results showcase detailed and more summative results with regards to health and energy use using the novel indicator. For Dcont and Dsmart the total Dynamic DALYs are 2.2 years and 8.6 years, respectively (population of 100 000, duration of 1 year), for the VOCs and sources considered in the analysis.

Prenatal fine particulate matter exposure associated with placental small extracellular vesicle derived microRNA and child neurodevelopmental delays

BACKGROUND AND AIMS

Prenatal fine particulate matter (PM_2.5) exposure has been linked to adverse neurodevelopment. However, epidemiological evidence remains inconclusive and little information about the effects of various PM_2.5 components on child neurodevelopment is currently known. The underlying mechanism was also not elucidated. The study aimed to evaluate the effects of PM_2.5 and components exposure on child neurodevelopmental delays and the role of placental small extracellular vesicles (sEVs)-derived miRNAs in the associations.

METHODS

We included 267 mother-child pairs in this analysis. Prenatal PM_2.5 and components (i.e. elements, water-soluble ions, and PAHs) exposure during three trimesters were monitored through personal PM_2.5 sampling. Child neurodevelopment at 2, 6, and 12 months old were evaluated by Ages and Stages Questionnaire (ASQ). We isolated sEVs from placental tissue to analyze the change of sEVs-derived miRNAs in response to PM_2.5. Associations between the PM_2.5-associated miRNAs and child neurodevelopment were evaluated using multivariate linear regression models.

RESULTS

The PM_2.5 exposure levels in the three trimesters range from 2.51 to 185.21 μg/m³. Prenatal PM_2.5 and the components of Pb, Al, V and Ti exposure in the second and third trimester were related to decreased ASQ scores communication, problem-solving and personal-social domains in children aged 2 or 6 months. RNA sequencing identified fifteen differentially expressed miRNAs. The miR-101-3p and miR-520d-5p were negatively associated with PM_2.5 and Pb component. miR-320a-3p expression was positively associated with PM_2.5 and V component. Meanwhile, the miR-320a-3p was associated with decreased ASQ scores, as reflected by ASQ-T (β: -2.154, 95 % CI: -4.313, -0.516) and problem-solving domain (β: -0.605, 95 % CI: -1.111, -0.099) in children aged 6 months.

CONCLUSION

Prenatal exposure to PM_2.5 and its Pb, Al, V & Ti component were associated with infant neurodevelopmental delays. The placenta sEVs derived miRNAs, especially miR-320a-3p, might contribute to an increased risk of neurodevelopmental delays.

Microglial Activation and Oxidative Stress in PM2.5-Induced Neurodegenerative Disorders

Fine particulate matter (PM_2.5) pollution remains a prominent environmental problem worldwide, posing great threats to human health. The adverse effects of PM_2.5 on the respiratory and cardiovascular systems have been extensively studied, while its detrimental effects on the central nervous system (CNS), specifically neurodegenerative disorders, are less investigated. Neurodegenerative disorders are characterized by reduced neurogenesis, activated microglia, and neuroinflammation. A variety of studies involving postmortem examinations, epidemiological investigations, animal experiments, and in vitro cell models have shown that PM_2.5 exposure results in neuroinflammation, oxidative stress, mitochondrial dysfunction, neuronal apoptosis, and ultimately neurodegenerative disorders, which are strongly associated with the activation of microglia. Microglia are the major innate immune cells of the brain, surveilling and maintaining the homeostasis of CNS. Upon activation by environmental and endogenous insults, such as PM exposure, microglia can enter an overactivated state that is featured by amoeboid morphology, the over-production of reactive oxygen species, and pro-inflammatory mediators. This review summarizes the evidence of microglial activation and oxidative stress and neurodegenerative disorders following PM_2.5 exposure. Moreover, the possible mechanisms underlying PM_2.5-induced microglial activation and neurodegenerative disorders are discussed. This knowledge provides certain clues for the development of therapies that may slow or halt the progression of neurodegenerative disorders induced by ambient PM.