Ambient air pollution and neurotoxicity on brain structure: Evidence from women's health initiative memory study

Association of midlife air pollution exposures and residential road proximity with incident dementia: The Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Increasing evidence links higher air pollution exposures to increased risk of cognitive impairment. While midlife risk factors are often most strongly linked to dementia risk, few studies have considered associations between midlife roadway proximity or ambient air pollution exposure and incident dementia decades later, in late life.

OBJECTIVES

Our objective was to determine if midlife exposures to ambient air pollution or roadway proximity are associated with increased risk of dementia in the Atherosclerosis Risk in Communities (ARIC) study over up to 29 years of follow-up.

METHODS

Our eligible sample included Black and White ARIC participants without dementia at Visit 2 (1990-1992). Participants were followed through Visit 7 (2018-2019), with dementia status and onset date defined based on formal dementia ascertainment at study visits, informant interviews, and surveillance efforts. We used adjusted Weibull survival models to assess the associations of midlife ambient air pollution and road proximity with incident dementia.

RESULTS

The median age at baseline (1990-1992, Visit 2) of the 12,700 eligible ARIC participants was 57.0 years; 56.0% were female, 24.2% were Black, and 78.9% had at least a high school education. Over up to 29 years of follow-up, 2511 (19.8%) persons developed dementia. No associations were found between ambient air pollutants and proximity to major roadways with risk of incident dementia. In exploratory analyses, living closer to roadways in midlife increased dementia risk in individuals younger at baseline and those without midlife hypertension, and there was evidence of increased risk of dementia with increased midlife exposure to NOx, several PM2.5 components, and trace metals among those with diabetes in midlife.

CONCLUSIONS

Midlife exposure to ambient air pollution and midlife roadway proximity was not associated with dementia risk over decades of follow-up. Further investigation to explore potential for greater susceptibility among specific subgroups identified here is needed.

High-quality models for assessing the effects of environmental pollutants on the nervous system: 3D brain organoids

The prevalence of environmental problems and the increasing risk of human exposure to environmental pollutants have become a global concern. The increasing environmental pollution is one of the main reasons for the rising incidence of most neurological-related diseases in recent years. However, the ethical constraints of direct human research and the racial limitations of animal models have slowed the progress of research in this area. The purpose of this study is to review the neurotoxicity of different environmental pollutants on the brain using brain organoids as a new model and to conclude that brain organoids may play a key role in assessing the mechanisms by which environmental pollutants affect neurogenesis and cause neurological pathogenesis. To accurately determine the negative effects of environmental pollutants on the nervous system, self-organizing brain organoids that are highly similar to the developing brain have become a new model system for studying the effects of environmental pollutants on human brain development and disease. This study uses brain organoids as a model to summarize the neurotoxicity of different environmental pollutants on the nervous system, including structural changes in brain organoids, inhibition of neuronal differentiation and migration, impairment of mitochondrial function, damage to cellular cilia, and influence on signaling pathways. In conclusion, exposure to environmental pollutants may cause different neurotoxicity to the nervous system. Therefore, it is crucial to understand how to use brain organoids to ameliorate neurological disorders caused by environmental pollution.

Association of ambient air pollution and Air Quality Index with risk of sudden sensorineural hearing loss: a cross-sectional study

OBJECTIVES

To explore the associations of air pollutants and Air Quality Index (AQI) with risk of sudden sensorineural hearing loss (SSNHL) DESIGN: Cross-sectional study SETTING: Medical record data and local population data collected between 2014 and 2022 in Changshu, China were retrospectively reviewed.

PARTICIPANTS

Adults aged 18 years and above who were diagnosed with SSNHL in Changshu No. 1 People's Hospital or Changshu No. 2 People's Hospital from the spring of 2014 to the fall of 2022 were included in the study.

OUTCOME MEASURE

SSNHL was diagnosed by clinicians using the Chinese diagnostic criteria for SSNHL.

RESULTS

Compared with those exposed to the lowest tertile of carbon monoxide (CO), the prevalence ratio for those exposed to middle and high tertiles of CO were 1.113 (95% CI 1.022 to 1.213) and 1.230 (95% CI 1.105 to 1.369), respectively. The risk of SSNHL was increased by 30.6% (95% CI 9.9% to 55.4%) per doubling increment of CO. No categorical association was found between ozone (O3) exposure and risk of SSNHL, however, an increased risk of 22.2% (0.8%-48.2%) was identified for each doubling of O3. No association was identified between other pollutants and AQI and risk of SSNHL.

CONCLUSIONS

In this study, CO and O3 were associated with an increased risk of SSNHL in Changshu, China. Further studies are warranted to confirm our findings.

PM2.5 induces developmental neurotoxicity in cortical organoids

There is mounting evidence implicating the potential neurotoxic effects of PM2.5 during brain development, as it has been observed to traverse both the placental barrier and the fetal blood-brain barrier. However, the current utilization of 2D cell culture and animal models falls short in providing an accurate representation of human brain development. Consequently, the precise mechanisms underlying PM2.5-induced developmental neurotoxicity in humans remain obscure. To address this research gap, we constructed three-dimensional (3D) cortical organoids that faithfully recapitulate the initial stages of human cerebral cortex development. Our goal is to investigate the mechanisms of PM2.5-induced neurotoxicity using 3D brain organoids that express cortical layer proteins. Our findings demonstrate that exposure to PM2.5 concentrations of 5 μg/mL and 50 μg/mL induces neuronal apoptosis and disrupts normal neural differentiation, thereby suggesting a detrimental impact on neurodevelopment. Furthermore, transcriptomic analysis revealed PM2.5 exposure induced aberrations in mitochondrial complex I functionality, which is reminiscent of Parkinson's syndrome, potentially mediated by misguided axon guidance and compromised synaptic maintenance. This study is a pioneering assessment of the neurotoxicity of PM2.5 pollution on human brain tissues based on 3D cortical organoids, and the results are of great significance in guiding the formulation of the next air pollution prevention and control policies in China to achieve the sustainable improvement of air quality and to formulate pollution abatement strategies that can maximize the benefits to public health.

Air Pollution and Parkinson Disease in a Population-Based Study

Importance

The role of air pollution in risk and progression of Parkinson disease (PD) is unclear.

Objective

To assess whether air pollution is associated with increased risk of PD and clinical characteristics of PD.

Design, Setting, and Participants

This population-based case-control study included patients with PD and matched controls from the Rochester Epidemiology Project from 1998 to 2015. Data were analyzed from January to June 2024.

Exposures

Mean annual exposure to particulate matter with a diameter of 2.5 µm or less (PM2.5) from 1998 to 2015 and mean annual exposure to nitrogen dioxide (NO2) from 2000 to 2014.

Main Outcomes and Measures

Outcomes of interest were PD risk, all-cause mortality, presence of tremor-predominant vs akinetic rigid PD, and development of dyskinesia. Models were adjusted for age, sex, race and ethnicity, year of index, and urban vs rural residence.

Results

A total of 346 patients with PD (median [IQR] age 72 [65-80] years; 216 [62.4%] male) were identified and matched on age and sex with 4813 controls (median [IQR] age, 72 [65-79] years, 2946 [61.2%] male). Greater PM2.5 exposure was associated with increased PD risk, and this risk was greatest after restricting to populations within metropolitan cores (odds ratio [OR], 1.23; 95% CI, 1.11-1.35) for the top quintile of PM2.5 exposure compared with the bottom quintile. Greater NO2 exposure was also associated with increased PD risk when comparing the top quintile with the bottom quintile (OR, 1.13; 95% CI, 1.07-1.19). Air pollution was associated with a 36% increased risk of akinetic rigid presentation (OR per each 1-μg/m3 increase in PM2.5, 1.36; 95% CI, 1.02-1.80). In analyses among patients with PD only, higher PM2.5 exposure was associated with greater risk for developing dyskinesia (HR per 1-μg/m3 increase in PM2.5, 1.42; 95% CI, 1.17-1.73), as was increased NO2 exposure (HR per 1 μg/m3 increase in NO2, 1.13; 95% CI, 1.06-1.19). There was no association between PM2.5 and all-cause mortality among patients with PD.

Conclusions and Relevance

In this case-control study of air pollution and PD, higher levels of PM2.5 and NO2 exposure were associated with increased risk of PD; also, higher levels of PM2.5 exposure were associated with increased risk of developing akinetic rigid PD and dyskinesia compared with patients with PD exposed to lower levels. These findings suggest that reducing air pollution may reduce risk of PD, modify the PD phenotype, and reduce risk of dyskinesia.

Air pollution: a latent key driving force of dementia

Many researchers have studied the role of air pollutants on cognitive function, changes in brain structure, and occurrence of dementia. Due to the wide range of studies and often contradictory results, the present systematic review was conducted to try and clarify the relationship between air pollutants and dementia. To identify studies for this review, a systematic search was conducted in Scopus, PubMed, and Web of Science databases (without historical restrictions) until May 22, 2023. The PECO statement was created to clarify the research question, and articles that did not meet the criteria of this statement were excluded. In this review, animal studies, laboratory studies, books, review articles, conference papers and letters to the editors were avoided. Also, studies focused on the effect of air pollutants on cellular and biochemical changes (without investigating dementia) were also excluded. A quality assessment was done according to the type of design of each article, using the checklist developed by the Joanna Briggs Institute (JBI). Finally, selected studies were reviewed and discussed in terms of Alzheimer's dementia and non-Alzheimer's dementia. We identified 14,924 articles through a systematic search in databases, and after comprehensive reviews, 53 articles were found to be eligible for inclusion in the current systematic review. The results showed that chronic exposure to higher levels of air pollutants was associated with adverse effects on cognitive abilities and the presence of dementia. Studies strongly supported the negative effects of PM2.5 and then NO2 on the brain and the development of neurodegenerative disorders in old age. Because the onset of brain structural changes due to dementia begins decades before the onset of disease symptoms, and that exposure to air pollution is considered a modifiable risk factor, taking preventive measures to reduce air pollution and introducing behavioral interventions to reduce people's exposure to pollutants is advisable.

Dysregulated metabolic pathways associated with air pollution exposure and the risk of autism: Evidence from epidemiological studies

Autism spectrum disorder (ASD) is a developmental disorder with symptoms that range from social and communication impairments to restricted interests and repetitive behavior and is the 4th most disabling condition for children aged 5-14. Risk factors of ASD are not fully understood. Environmental risk factors are believed to play a significant role in the ASD epidemic. Research focusing on air pollution exposure as an early-life risk factor of autism is growing, with numerous studies finding associations of traffic and industrial emissions with an increased risk of ASD. One of the possible mechanisms linking autism and air pollution exposure is metabolic dysfunction. However, there were no consensus about the key metabolic pathways and corresponding metabolite signatures in mothers and children that are altered by air pollution exposure and cause the ASD. Therefore, we performed a review of published papers examining the metabolomic signatures and metabolic pathways that are associated with either air pollution exposure or ASD risk in human studies. In conclusion, we found that dysregulated lipid, fatty acid, amino acid, neurotransmitter, and microbiome metabolisms are associated with both short-term and long-term air pollution exposure and the risk of ASD. These dysregulated metabolisms may provide insights into ASD etiology related to air pollution exposure, particularly during the perinatal period in which neurodevelopment is highly susceptible to damage from oxidative stress and inflammation.

Associations of long-term exposure to low-level PM2.5 and brain disorders in 260,922 middle-aged and older adults

Long-term exposure to high-level ambient PM2.5 was associated with increased risks of brain disorders, while the associations remain uncertain when the exposure is lower than current air quality standards in numerous countries. This study aimed to assess the effects of PM2.5 exposure on the brain system in the population with annual mean concentrations ≤15 μg/m3. We analyzed data from 260,922 participants without preexisting brain diseases at baseline in the UK Biobank. The geographical distribution of PM2.5 in 2010 was estimated by a land use regression model and linked with individual residential address. We investigated associations of ambient PM2.5 with incident neurological (dementia, Parkinson's diseases [PD], epilepsy, and migraine) and psychiatric (major depressive disorder [MDD] and anxiety disorder) diseases through Cox proportional hazard models. We further estimated the links with brain imaging phenotypes by neuroimaging analysis. Results showed that in the population with PM2.5 concentrations ≤15 μg/m3, each interquartile range (IQR, 1.28 μg/m3) increment in PM2.5 was related to incidence risks of dementia, epilepsy, migraine, MDD, and anxiety disorder with hazard ratios of 1.08 (95% confidence interval [CI]: 1.03, 1.13), 1.12 (1.05, 1.20), 1.07 (1.00, 1.13), 1.06 (1.03, 1.09), and 1.05 (1.02, 1.08), respectively. We did not observe a significant association with PD. The association with dementia was stronger among the population with poor cardiovascular health (measured by Life's Essential 8) than the counterpart (P for interaction = 0.037). Likewise, per IQR increase was associated with specific brain imaging phenotypes, including volumes of total brain (β = -0.036; 95% CI: -0.050, -0.022), white matter (-0.030; -0.046, -0.014), grey matter (-0.030; -0.042, -0.017), respectively. The findings suggest long-term exposure to ambient PM2.5 at low-level still has an adverse impact on the neuro-psychiatric systems. The brain-relevant epidemiological assessment suggests that each country should update the standard for ambient PM2.5 following the World Health Organization Air Quality Guidelines 2021.

Yearly change in air pollution and brain aging among older adults: A community-based study in Taiwan

BACKGROUND

Air pollution is recognized as a modifiable risk factor for dementia, and recent evidence suggests that improving air quality could attenuate cognitive decline and reduce dementia risk. However, studies have yet to explore the effects of improved air quality on brain structures. This study aims to investigate the impact of air pollution reduction on cognitive functions and structural brain differences among cognitively normal older adults.

METHODS

Four hundred and thirty-one cognitively normal older adults were from the Epidemiology of Mild Cognitive Impairment study in Taiwan (EMCIT), a community-based cohort of adults aged 60 and older, between year 2017- 2021. Annual concentrations of PM2.5, NO2, O3, and PM10 at participants' residential addresses during the 10 years before enrollment were estimated using ensemble mixed spatial models. The yearly rate of change (slope) in air pollutants was estimated for each participant. Cognitive functions and structural brain images were collected during enrollment. The relationships between the rate of air pollution change and cognitive functions were examined using linear regression models. For air pollutants with significant findings in relation to cognitive function, we further explored the association with brain structure.

RESULTS

Overall, all pollutant concentrations, except O3, decreased over the 10-year period. The yearly rates of change (slopes) in PM2.5 and NO2 were correlated with better attention (PM2.5: r = -0.1, p = 0.047; NO2: r = -0.1, p = 0.03) and higher white matter integrity in several brain regions. These regions included anterior thalamic radiation, superior longitudinal fasciculus, inferior longitudinal fasciculus, corticospinal tract, and inferior fronto-occipital fasciculus.

CONCLUSIONS

Greater rate of reduction in air pollution was associated with better attention and attention-related white matter integrity. These results provide insight into the mechanism underlying the relationship between air pollution, brain health, and cognitive aging among older adults.

The Association between Exposure to Fine Particulate Matter and MRI-Assessed Locus Coeruleus Integrity in the Vietnam Era Twin Study of Aging (VETSA)

BACKGROUND

Increased exposure to ambient air pollution, especially fine particulate matter ≤ 2.5 μ m (PM 2.5 ) is associated with poorer brain health and increased risk for Alzheimer's disease (AD) and related dementias. The locus coeruleus (LC), located in the brainstem, is one of the earliest regions affected by tau pathology seen in AD. Its diffuse projections throughout the brain include afferents to olfactory areas that are hypothesized conduits of cerebral particle deposition. Additionally, extensive contact of the LC with the cerebrovascular system may present an additional route of exposure to environmental toxicants.

OBJECTIVE

Our aim was to investigate if exposure to PM 2.5 was associated with LC integrity in a nationwide sample of men in early old age, potentially representing one pathway through which air pollution can contribute to increased risk for AD dementia.

METHODS

We examined the relationship between PM 2.5 and in vivo magnetic resonance imaging (MRI) estimates of LC structural integrity indexed by contrast to noise ratio (LC CNR ) in 381 men [mean age = 67.3 ; standard deviation ( SD ) = 2.6 ] from the Vietnam Era Twin Study of Aging (VETSA). Exposure to PM 2.5 was taken as a 3-year average over the most recent period for which data were available (average of 5.6 years prior to the MRI scan). We focused on LC CNR in the rostral-middle portion of LC due to its stronger associations with aging and AD than the caudal LC. Associations between PM 2.5 exposures and LC integrity were tested using linear mixed effects models adjusted for age, scanner, education, household income, and interval between exposure and MRI. A co-twin control analysis was also performed to investigate whether associations remained after controlling for genetic confounding and rearing environment.

RESULTS

Multiple linear regressions revealed a significant association between PM 2.5 and rostral-middle LC CNR (β = - 0.16 ; p = 0.02 ), whereby higher exposure to PM 2.5 was associated with lower LC CNR . A co-twin control analysis found that, within monozygotic pairs, individuals with higher PM 2.5 exposure showed lower LC CNR (β = - 0.11 ; p = 0.02 ), indicating associations were not driven by genetic or shared environmental confounds. There were no associations between PM 2.5 and caudal LC CNR or hippocampal volume, suggesting a degree of specificity to the rostral-middle portion of the LC.

DISCUSSION

Given previous findings that loss of LC integrity is associated with increased accumulation of AD-related amyloid and tau pathology, impacts on LC integrity may represent a potential pathway through which exposure to air pollution increases AD risk. https://doi.org/10.1289/EHP14344.

How does the macroenvironment influence brain and behaviour-a review of current status and future perspectives

The environment influences brain and mental health, both detrimentally and beneficially. Existing research has emphasised the individual psychosocial 'microenvironment'. Less attention has been paid to 'macroenvironmental' challenges, including climate change, pollution, urbanicity, and socioeconomic disparity. Notably, the implications of climate and pollution on brain and mental health have only recently gained prominence. With the advent of large-scale big-data cohorts and an increasingly dense mapping of macroenvironmental parameters, we are now in a position to characterise the relation between macroenvironment, brain, and behaviour across different geographic and cultural locations globally. This review synthesises findings from recent epidemiological and neuroimaging studies, aiming to provide a comprehensive overview of the existing evidence between the macroenvironment and the structure and functions of the brain, with a particular emphasis on its implications for mental illness. We discuss putative underlying mechanisms and address the most common exposures of the macroenvironment. Finally, we identify critical areas for future research to enhance our understanding of the aetiology of mental illness and to inform effective interventions for healthier environments and mental health promotion.

Microglial TLR4 Mediates White Matter Injury in a Combined Model of Diesel Exhaust Exposure and Cerebral Hypoperfusion

BACKGROUND

Air pollution particulate matter exposure and chronic cerebral hypoperfusion (CCH) contribute to white matter toxicity through shared mechanisms of neuroinflammation, oxidative stress, and myelin breakdown. Prior studies showed that exposure of mice to joint particulate matter and CCH caused supra-additive injury to corpus callosum white matter. This study examines the role of TLR4 (toll-like receptor 4) signaling in mediating neurotoxicity and myelin damage observed in joint particulate matter and CCH exposures.

METHODS

Experiments utilized a novel murine model of inducible monocyte/microglia-specific TLR4 knockout (i-mTLR4-ko). Bilateral carotid artery stenosis (BCAS) was induced surgically to model CCH. TLR4-intact (control) and i-mTLR4-ko mice were exposed to 8 weeks of either aerosolized diesel exhaust particulate (DEP) or filtered air (FA) in 8 experimental groups: (1) control/FA (n=10), (2) control/DEP (n=10), (3) control/FA+BCAS (n=9), (4) control/DEP+BCAS (n=10), (5) i-mTLR4-ko/FA (n=9), (6) i-mTLR4-ko/DEP (n=8), (7) i-mTLR4-ko/FA+BCAS (n=8), and (8) i-mTLR4-ko/DEP+BCAS (n=10). Corpus callosum levels of 4-hydroxynonenal, 8-Oxo-2'-deoxyguanosine, Iba-1 (ionized calcium-binding adapter molecule 1), and dMBP (degraded myelin basic protein) were assayed via immunofluorescence to measure oxidative stress, neuroinflammation, and myelin breakdown, respectively.

RESULTS

Compared with control/FA mice, control/DEP+BCAS mice exhibited increased dMBP (41%; P<0.01), Iba-1 (51%; P<0.0001), 4-hydroxynonenal (100%; P<0.0001), and 8-Oxo-2'-deoxyguanosine (65%; P<0.05). I-mTLR4 knockout attenuated responses to DEP/BCAS for all markers.

CONCLUSIONS

i-mTLR4-ko markedly reduced neuroinflammation and oxidative stress and attenuated white matter degradation following DEP and CCH exposures. This suggests a potential role for targeting TLR4 signaling in individuals with vascular cognitive impairment, particularly those exposed to substantial ambient air pollution.

Machine learning and XAI approaches highlight the strong connection between O 3 and N O 2 pollutants and Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia with millions of affected patients worldwide. Currently, there is still no cure and AD is often diagnosed long time after onset because there is no clear diagnosis. Thus, it is essential to study the physiology and pathogenesis of AD, investigating the risk factors that could be strongly connected to the disease onset. Despite AD, like other complex diseases, is the result of the combination of several factors, there is emerging agreement that environmental pollution should play a pivotal role in the causes of disease. In this work, we implemented an Artificial Intelligence model to predict AD mortality, expressed as Standardized Mortality Ratio, at Italian provincial level over 5 years. We employed a set of publicly available variables concerning pollution, health, society and economy to feed a Random Forest algorithm. Using methods based on eXplainable Artificial Intelligence (XAI) we found that air pollution (mainly O 3 and N O 2 ) contribute the most to AD mortality prediction. These results could help to shed light on the etiology of Alzheimer's disease and to confirm the urgent need to further investigate the relationship between the environment and the disease.

The impact of air pollution on neurocognitive development: Adverse effects and health disparities

Air pollution is recognized as a major public health concern. The number of deaths related to ambient air pollution has increased in recent years and is projected to continue rising. Additionally, both short- and long-term air pollution exposure has been linked with deleterious effects on neurocognitive function and development. While air pollution poses as a threat to everyone, people of color and individuals of lower socioeconomic status are often exposed to elevated levels of air pollution as a function of systemic racism and classism. Further, given additional disparities in access to healthcare and other compounding stressors, adverse effects of air pollution on neurocognitive health are exacerbated among individuals who hold marginalized identities-making effects both less likely to be detected and treated. This review examines evidence of the effects of air pollution on neurocognitive development across the lifespan and incorporates an environmental justice perspective to highlight disparities in air pollution exposure across race and socioeconomic status. Last, upon the reviewed evidence, limitations of past research and recommendations for policy are discussed.

Association between late-life air pollution exposure and medial temporal lobe atrophy in older women

Background

Ambient air pollution exposures increase risk for Alzheimer's disease (AD) and related dementias, possibly due to structural changes in the medial temporal lobe (MTL). However, existing MRI studies examining exposure effects on the MTL were cross-sectional and focused on the hippocampus, yielding mixed results.

Method

To determine whether air pollution exposures were associated with MTL atrophy over time, we conducted a longitudinal study including 653 cognitively unimpaired community-dwelling older women from the Women's Health Initiative Memory Study with two MRI brain scans (MRI-1: 2005-6; MRI-2: 2009-10; Mage at MRI-1=77.3±3.5years). Using regionalized universal kriging models, exposures at residential locations were estimated as 3-year annual averages of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) prior to MRI-1. Bilateral gray matter volumes of the hippocampus, amygdala, parahippocampal gyrus (PHG), and entorhinal cortex (ERC) were summed to operationalize the MTL. We used linear regressions to estimate exposure effects on 5-year volume changes in the MTL and its subregions, adjusting for intracranial volume, sociodemographic, lifestyle, and clinical characteristics.

Results

On average, MTL volume decreased by 0.53±1.00cm3 over 5 years. For each interquartile increase of PM2.5 (3.26μg/m3) and NO2 (6.77ppb), adjusted MTL volume had greater shrinkage by 0.32cm3 (95%CI=[-0.43, -0.21]) and 0.12cm3 (95%CI=[-0.22, -0.01]), respectively. The exposure effects did not differ by APOE ε4 genotype, sociodemographic, and cardiovascular risk factors, and remained among women with low-level PM2.5 exposure. Greater PHG atrophy was associated with higher PM2.5 (b=-0.24, 95%CI=[-0.29, -0.19]) and NO2 exposures (b=-0.09, 95%CI=[-0.14, -0.04]). Higher exposure to PM2.5 but not NO2 was also associated with greater ERC atrophy. Exposures were not associated with amygdala or hippocampal atrophy.

Conclusion

In summary, higher late-life PM2.5 and NO2 exposures were associated with greater MTL atrophy over time in cognitively unimpaired older women. The PHG and ERC - the MTL cortical subregions where AD neuropathologies likely begin, may be preferentially vulnerable to air pollution neurotoxicity.

Alzheimer's Related Neurodegeneration Mediates Air Pollution Effects on Medial Temporal Lobe Atrophy

Exposure to ambient air pollution, especially particulate matter with aerodynamic diameter <2.5 μm (PM2.5) and nitrogen dioxide (NO2), are environmental risk factors for Alzheimer's disease and related dementia. The medial temporal lobe (MTL) is an important brain region subserving episodic memory that atrophies with age, during the Alzheimer's disease continuum, and is vulnerable to the effects of cerebrovascular disease. Despite the importance of air pollution it is unclear whether exposure leads to atrophy of the MTL and by what pathways. Here we conducted a longitudinal study examining associations between ambient air pollution exposure and MTL atrophy and whether putative air pollution exposure effects resembled Alzheimer's disease-related neurodegeneration or cerebrovascular disease-related neurodegeneration. Participants included older women (n = 627; aged 71-87) who underwent two structural brain MRI scans (MRI-1: 2005-6; MRI-2: 2009-10) as part of the Women's Health Initiative Memory Study of Magnetic Resonance Imaging. Regionalized universal kriging was used to estimate annual concentrations of PM2.5 and NO2 at residential locations aggregated to 3-year averages prior to MRI-1. The outcome was 5-year standardized change in MTL volumes. Mediators included voxel-based MRI measures of the spatial pattern of neurodegeneration of Alzheimer's disease (Alzheimer's disease pattern similarity scores [AD-PS]) and whole-brain white matter small-vessel ischemic disease (WM-SVID) volume as a proxy of global cerebrovascular damage. Structural equation models were constructed to examine whether the associations between exposures with MTL atrophy were mediated by the initial level or concurrent change in AD-PS score or WM-SVID while adjusting for sociodemographic, lifestyle, clinical characteristics, and intracranial volume. Living in locations with higher PM2.5 (per interquartile range [IQR]=3.17μg/m3) or NO2 (per IQR=6.63ppb) was associated with greater MTL atrophy (βPM2.5 = -0.29, 95% confidence interval [CI]=[-0.41,-0.18]; βNO2 =-0.12, 95%CI=[-0.23,-0.02]). Greater PM2.5 was associated with larger increases in AD-PS (βPM2.5 = 0.23, 95%CI=[0.12,0.33]) over time, which partially mediated associations with MTL atrophy (indirect effect= -0.10; 95%CI=[-0.15, -0.05]), explaining approximately 32% of the total effect. NO2 was positively associated with AD-PS at MRI-1 (βNO2=0.13, 95%CI=[0.03,0.24]), which partially mediated the association with MTL atrophy (indirect effect= -0.01, 95% CI=[-0.03,-0.001]). Global WM-SVID at MRI-1 or concurrent change were not significant mediators between exposures and MTL atrophy. Findings support the mediating role of Alzheimer's disease-related neurodegeneration contributing to MTL atrophy associated with late-life exposures to air pollutants. Alzheimer's disease-related neurodegeneration only partially explained associations between exposure and MTL atrophy suggesting the role of multiple neuropathological processes underlying air pollution neurotoxicity on brain aging.

How does the macroenvironment influence brain and behaviour - a review of current status and future perspectives

The environment influences mental health, both detrimentally and beneficially. Current research has emphasized the individual psychosocial 'microenvironment'. Less attention has been paid to 'macro-environmental' challenges including climate change, pollution, urbanicity and socioeconomic disparity. With the advent of large-scale big-data cohorts and an increasingly dense mapping of macroenvironmental parameters, we are now in a position to characterise the relation between macroenvironment, brain, and behaviour across different geographic and cultural locations globally. This review synthesises findings from recent epidemiological and neuroimaging studies, aiming to provide a comprehensive overview of the existing evidence between the macroenvironment and the structure and functions of the brain, with a particular emphasis on its implications for mental illness. We discuss putative underlying mechanisms and address the most common exposures of the macroenvironment. Finally, we identify critical areas for future research to enhance our understanding of the aetiology of mental illness and to inform effective interventions for healthier environments and mental health promotion.

Environmental violence: a tool for planetary health research

From climate change to toxic pollution and the interactive effects of multiple pollution streams, human health is under siege. Human-produced environmental risks to health and wellbeing are high and contributing to patterns of global morbidity, mortality, economic inequality, displacement, and insecurity. The implications of human-produced environmental harms to global health are complex just as are their causes. The concept of environmental violence offers a potentially robust frame for engaging this issue. We argue that a more specified and structured framework and definition of environmental violence-focusing on human-produced harms by way of pollution emissions-is both timely and beneficial for engaging the complexities of global public health. To clarify why and how this is the case, we review the literature for publications that use the term environmental violence and we subsequently propose a specific definition focused on human-produced pollution along with a framework for tracking and analysing environmental violence and its constituent components. Finally, we discuss the potential value of our framework for research and policy making regarding human health.

The association of long-term exposure to criteria air pollutants, fine particulate matter components, and airborne trace metals with late-life brain amyloid burden in the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Studies suggest associations between long-term ambient air pollution exposure and outcomes related to Alzheimer's disease (AD). Whether a link exists between pollutants and brain amyloid accumulation, a biomarker of AD, is unclear. We assessed whether long-term air pollutant exposures are associated with late-life brain amyloid deposition in Atherosclerosis Risk in Communities (ARIC) study participants.

METHODS

We used a chemical transport model with data fusion to estimate ambient concentrations of PM2.5 and its components, NO2, NOx, O3 (24-hour and 8-hour), CO, and airborne trace metals. We linked concentrations to geocoded participant addresses and calculated 10-year mean exposures (2002 to 2011). Brain amyloid deposition was measured using florbetapir amyloid positron emission tomography (PET) scans in 346 participants without dementia in 2012-2014, and we defined amyloid positivity as a global cortical standardized uptake value ratio ≥ the sample median of 1.2. We used logistic regression models to quantify the association between amyloid positivity and each air pollutant, adjusting for putative confounders. In sensitivity analyses, we considered whether use of alternate air pollution estimation approaches impacted findings for PM2.5, NO2, NOx, and 24-hour O3.

RESULTS

At PET imaging, eligible participants (N = 318) had a mean age of 78 years, 56% were female, 43% were Black, and 27% had mild cognitive impairment. We did not find evidence of associations between long-term exposure to any pollutant and brain amyloid positivity in adjusted models. Findings were materially unchanged in sensitivity analyses using alternate air pollution estimation approaches for PM2.5, NO2, NOx, and 24-hour O3.

CONCLUSIONS

Air pollution may impact cognition and dementia independent of amyloid accumulation, though whether air pollution influences AD pathogenesis later in the disease course or at higher exposure levels deserves further consideration.

Ambient Air Pollution Exposure and Cerebral White Matter Hyperintensities in Older Adults: A Cross-Sectional Analysis in the Three-City Montpellier Study

BACKGROUND

Growing epidemiological evidence suggests an adverse relationship between exposure to air pollutants and cognitive health, and this could be related to the effect of air pollution on vascular health.

OBJECTIVE

We aim to evaluate the association between air pollution exposure and a magnetic resonance imaging (MRI) marker of cerebral vascular burden, white matter hyperintensities (WMH).

METHODS

This cross-sectional analysis used data from the French Three-City Montpellier study. Randomly selected participants 65-80 years of age underwent an MRI examination to estimate their total and regional cerebral WMH volumes. Exposure to fine particulate matter (PM 2.5 ), nitrogen dioxide (NO 2 ), and black carbon (BC) at the participants' residential address during the 5 years before the MRI examination was estimated with land use regression models. Multinomial and binomial logistic regression assessed the associations between exposure to each of the three pollutants and categories of total and lobar WMH volumes.

RESULTS

Participants' (n = 582 ) median age at MRI was 70.7 years [interquartile range (IQR): 6.1], and 52% (n = 300 ) were women. Median exposure to air pollution over the 5 years before MRI acquisition was 24.3 (IQR: 1.7) μ g / m 3 for PM 2.5 , 48.9 (14.6) μ g / m 3 for NO 2 , and 2.66 (0.60) 10 - 5 / m for BC. We found no significant association between exposure to the three air pollutants and total WMH volume. We found that PM 2.5 exposure was significantly associated with higher risk of temporal lobe WMH burden [odds ratio (OR) for an IQR increase = 1.82 (95% confidence interval: 1.41, 2.36) for the second volume tercile, 2.04 (1.59, 2.61) for the third volume tercile, reference: first volume tercile]. Associations for other regional WMH volumes were inconsistent.

CONCLUSION

In this population-based study in older adults, PM 2.5 exposure was associated with increased risk of high WMH volume in the temporal lobe, strengthening the evidence on PM 2.5 adverse effect on the brain. Further studies looking at different markers of cerebrovascular damage are still needed to document the potential vascular effects of air pollution. https://doi.org/10.1289/EHP12231.

Characteristics of urban neighbourhood environments and cognitive age in mid-age and older adults

In this cross-sectional study, we examined the extent to which features of the neighbourhood natural, built, and socio-economic environments were related to cognitive age in adults (N = 3418, Mage = 61 years) in Australia. Machine learning estimated an individual's cognitive age from assessments of processing speed, verbal memory, premorbid intelligence. A 'cognitive age gap' was calculated by subtracting chronological age from predicted cognitive age and was used as a marker of cognitive age. Greater parkland availability and higher neighbourhood socio-economic status were associated with a lower cognitive age gap score in confounder- and mediator-adjusted regression models. Cross-sectional design is a limitation. Living in affluent neighbourhoods with access to parks maybe beneficial for cognitive health, although selection mechanisms may contribute to the findings.

Magnetic resonance imaging of white matter response to diesel exhaust particles

Air pollution is associated with risks of dementia and accelerated cognitive decline. Rodent air pollution models have shown white matter vulnerability. This study uses diffusion tensor imaging (DTI) to quantify changes to white matter microstructure and tractography in multiple myelinated regions after exposure to diesel exhaust particulate (DEP). Adult C57BL/6 male mice were exposed to re-aerosolized DEP (NIST SRM 2975) at a concentration of 100 ug/m3 for 200 hours. Ex-vivo MRI analysis and fractional anisotropy (FA)-aided white matter tractography were conducted to study the effect of DEP exposure on the brain white matter tracts. Immunohistochemistry was used to assess myelin and axonal structure. DEP exposure for 8 weeks altered myelin composition in multiple regions. Diffusion tensor imaging (DTI) showed decreased FA in the corpus callosum (30%), external capsule (15%), internal capsule (15%), and cingulum (31 %). Separate immunohistochemistry analyses confirmed prior findings. Myelin basic protein (MBP) was decreased (corpus callosum: 28%, external capsule: 29%), and degraded MPB increased (corpus callosum: 32%, external capsule: 53%) in the DEP group. White matter is highly susceptible to chronic DEP exposure. This study demonstrates the utility of DTI as a neuroanatomical tool in the context of air pollution and white matter myelin vulnerability.

An Examination of the Joint Effect of the Social Environment and Air Pollution on Dementia Among US Older Adults

Evidence suggests exposure to air pollution increases the risk of dementia. Cognitively stimulating activities and social interactions, made available through the social environment, may slow cognitive decline. We examined whether the social environment buffers the adverse effect of air pollution on dementia in a cohort of older adults.

Methods

This study draws from the Ginkgo Evaluation of Memory Study. Participants aged 75 years and older were enrolled between 2000 and 2002 and evaluated for dementia semi-annually through 2008. Long-term exposure to particulate matter and nitrogen dioxide was assigned from spatial and spatiotemporal models. Census tract-level measures of the social environment and individual measures of social activity were used as measures of the social environment. We generated Cox proportional hazard models with census tract as a random effect and adjusted for demographic and study visit characteristics. Relative excess risk due to interaction was estimated as a qualitative measure of additive interaction.

Results

This study included 2,564 individuals. We observed associations between increased risk of dementia and fine particulate matter (µg/m3), coarse particulate matter (µg/m3), and nitrogen dioxide (ppb); HRs per 5 unit increase were 1.55 (1.01, 2.18), 1.31 (1.07, 1.60), and 1.18 (1.02, 1.37), respectively. We found no evidence of additive interaction between air pollution and the neighborhood social environment.

Conclusions

We found no consistent evidence to suggest a synergistic effect between exposure to air pollution and measures of the social environment. Given the many qualities of the social environment that may reduce dementia pathology, further examination is encouraged.

Air Pollution: A Silent Key Driver of Dementia

In 2017, the Lancet Commission on Dementia Prevention, Intervention, and Care included air pollution in its list of potential risk factors for dementia; in 2018, the Lancet Commission on Pollution concluded that the evidence for a causal relationship between fine particulate matter (PM) and dementia is encouraging. However, few interventions exist to delay or prevent the onset of dementia. Air quality data are becoming increasingly available, and the science underlying the associated health effects is also evolving rapidly. Recent interest in this area has led to the publication of population-based cohort studies, but these studies have used different approaches to identify cases of dementia. The purpose of this article is to review recent evidence describing the association between exposure to air pollution and dementia with special emphasis on fine particulate matter of 2.5 microns or less. We also summarize here the proposed detailed mechanisms by which air pollutants reach the brain and activate the innate immune response. In addition, the article also provides a short overview of existing limitations in the treatment of dementia.

Lifetime air pollution exposure, cognitive deficits, and brain imaging outcomes: A systematic review

As the amount of air pollution and human exposure has increased, the effects on human health have become an important public health issue. A field of growing interest is how air pollution exposure affects brain structure and function underlying cognitive deficits and if structural and connectivity changes mediate the relationship between the two. We conducted a systematic review to examine the literature on air pollution, brain structure and connectivity, and cognition studies. Eleven studies matched our inclusion criteria and were included in the qualitative analysis. Results suggest significant associations between air pollution and decreased volumes of specific brain structures, cortical thickness and surface area such as in the prefrontal cortex and temporal lobe, as well as the weakening of functional connectivity pathways, largely the Default Mode (DMN) and Frontal Parietal (FPN) networks, as detected by fMRI. Associations between air pollution and cognitive outcomes were found in most of the studies (n = 9), though some studies showed stronger associations than others. For children & adolescents, these deficiencies largely involved heavy reasoning, problem solving, and logic. For young and middle-aged adults, the associations were mostly seen for executive function and visuospatial cognitive domains. To our knowledge, this is the first systematic review to consolidate findings on the associations among air pollution, brain structure, and cognitive function. In the future, it will be important to conduct further longitudinal studies that follow children who have been exposed at a young age and examine associations with brain structure and cognition throughout adulthood.

Particulate matter and ultrafine particles in urban air pollution and their effect on the nervous system

According to the World Health Organization, both indoor and urban air pollution are responsible for the deaths of around 3.5 million people annually. During the last few decades, the interest in understanding the composition and health consequences of the complex mixture of polluted air has steadily increased. Today, after decades of detailed research, it is well-recognized that polluted air is a complex mixture containing not only gases (CO, NO_x, and SO₂) and volatile organic compounds but also suspended particles such as particulate matter (PM). PM comprises particles with sizes in the range of 30 to 2.5 μm (PM₃₀, PM₁₀, and PM_2.5) and ultrafine particles (UFPs) (less than 0.1 μm, including nanoparticles). All these constituents have different chemical compositions, origins and health consequences. It has been observed that the concentration of PM and UFPs is high in urban areas with moderate traffic and increases in heavy traffic areas. There is evidence that inhaling PM derived from fossil fuel combustion is associated with a wide variety of harmful effects on human health, which are not solely associated with the respiratory system. There is accumulating evidence that the brains of urban inhabitants contain high concentrations of nanoparticles derived from combustion and there is both epidemiological and experimental evidence that this is correlated with the appearance of neurodegenerative human diseases. Neurological disorders, such as Alzheimer's and Parkinson's disease, multiple sclerosis, and cerebrovascular accidents, are among the main debilitating disorders of our time and their epidemiology can be classified as a public health emergency. Therefore, it is crucial to understand the pathophysiology and molecular mechanisms related to PM exposure, specifically to UFPs, present as pollutants in air, as well as their correlation with the development of neurodegenerative diseases. Furthermore, PM can enhance the transmission of airborne diseases and trigger inflammatory and immune responses, increasing the risk of health complications and mortality. Therefore, understanding the different levels of this issue is important to create and promote preventive actions by both the government and civilians to construct a strategic plan to treat and cope with the current and future epidemic of these types of disorders on a global scale.

Associations of Particulate Matter Exposures With Brain Gray Matter Thickness and White Matter Hyperintensities: Effect Modification by Low-Grade Chronic Inflammation

BACKGROUND

Numerous studies have shown the effect of particulate matter exposure on brain imaging markers. However, little evidence exists about whether the effect differs by the level of low-grade chronic systemic inflammation. We investigated whether the level of c-reactive protein (CRP, a marker of systemic inflammation) modifies the associations of particulate matter exposures with brain cortical gray matter thickness and white matter hyperintensities (WMH).

METHODS

We conducted a cross-sectional study of baseline data from a prospective cohort study including adults with no dementia or stroke. Long-term concentrations of particulate matter ≤ 10 µm in diameter (PM10) and ≤ 2.5 µm (PM2.5) at each participant's home address were estimated. Global cortical thickness (n = 874) and WMH volumes (n = 397) were estimated from brain magnetic resonance images. We built linear and logistic regression models for cortical thickness and WMH volumes (higher versus lower than median), respectively. Significance of difference in the association between the CRP group (higher versus lower than median) was expressed as P for interaction.

RESULTS

Particulate matter exposures were significantly associated with a reduced global cortical thickness only in the higher CRP group among men (P for interaction = 0.015 for PM10 and 0.006 for PM2.5). A 10 μg/m³ increase in PM10 was associated with the higher volumes of total WMH (odds ratio, 1.78; 95% confidence interval, 1.07-2.97) and periventricular WMH (2.00; 1.20-3.33). A 1 μg/m³ increase in PM2.5 was associated with the higher volume of periventricular WMH (odds ratio, 1.66; 95% confidence interval, 1.08-2.56). These associations did not significantly differ by the level of high sensitivity CRP.

CONCLUSION

Particulate matter exposures were associated with a reduced global cortical thickness in men with a high level of chronic inflammation. Men with a high level of chronic inflammation may be susceptible to cortical atrophy attributable to particulate matter exposures.

Particulate matter exposure and chronic cerebral hypoperfusion promote oxidative stress and induce neuronal and oligodendrocyte apoptosis in male mice

Chronic cerebral hypoperfusion (CCH) may amplify the neurotoxicity of nanoscale particulate matter (nPM), resulting in white matter injury. This study characterized the joint effects of nPM (diameter ≤ 200 nm) and CCH secondary to bilateral carotid artery stenosis (BCAS) exposure on neuronal and white matter injury in a murine model. nPM was collected near a highway and re-aerosolized for exposure. Ten-week-old C57BL/6 male mice were randomized into four groups: filtered air (FA), nPM, FA + BCAS, and nPM + BCAS. Mice were exposed to FA or nPM for 10 weeks. BCAS surgeries were performed. Markers of inflammation, oxidative stress, and apoptosis were examined. nPM + BCAS exposure increased brain hemisphere TNFα protein compared to FA. iNOS and HNE immunofluorescence were increased in the corpus callosum and cerebral cortex of nPM + BCAS mice compared to FA. While nPM exposure alone did not decrease cortical neuronal cell count, nPM decreased corpus callosum oligodendrocyte cell count. nPM exposure decreased mature oligodendrocyte cell count and increased oligodendrocyte precursor cell count in the corpus callosum. nPM + BCAS mice exhibited a 200% increase in cortical neuronal TUNEL staining and a 700% increase in corpus callosum oligodendrocyte TUNEL staining compared to FA. There was a supra-additive interaction between nPM and BCAS on cortical neuronal TUNEL staining (2.6× the additive effects of nPM + BCAS). nPM + BCAS exposure increased apoptosis, neuroinflammation, and oxidative stress in the cerebral cortex and corpus callosum. nPM + BCAS exposure increased neuronal apoptosis above the separate responses to each exposure. However, oligodendrocytes in the corpus callosum demonstrated a greater susceptibility to the combined neurotoxic effects of nPM + BCAS exposure.

Curcumin Ameliorates Neurobehavioral Deficits in Ambient Dusty Particulate Matter-Exposure Rats: The Role of Oxidative Stress

It has been consistently found that exposure to ambient air pollution, such as particulate matter (PM), results in cognitive impairments and mental disorders. This study aimed to investigate the possible neuroprotective effects of curcumin, a polyphenol compound, on the neurobehavioral deficits and to identify the role of oxidative stress in dusty PM exposure rats. Rats received curcumin (50 mg/kg, daily, gavage, 2 weeks) 30 min before placing animals in a clean air chamber (≤ 150 µg/m³, 60 min daily, 2 weeks) or ambient dusty PM chamber (2000-8000 µg/m³, 60 min daily, 2 weeks). Subsequently, the cognitive and non-cognitive functions of the animals were evaluated using standard behavioral tests. Moreover, blood-brain barrier (BBB) permeability, brain water content (BWC), oxidative-antioxidative status, and histological changes were determined in the cerebral cortex and hippocampal areas of the rats. Our results showed that curcumin administration in dusty PM exposure rats attenuates memory impairment, decreases anxiety-/depression-like behaviors, and improves locomotor/exploratory activities. These findings were accompanied by reduced BBB permeability and BWC, decreasing oxidative stress, and lessening neuronal loss in the cerebral cortex and different hippocampal areas. The results of this study suggest that curcumin's antioxidant properties may contribute to its efficacy in improving neurobehavioral deficits and preventing neuronal loss associated with dusty PM exposure.

Air Pollution-Related Neurotoxicity Across the Life Span

Air pollution is a complex mixture of gases and particulate matter, with adsorbed organic and inorganic contaminants, to which exposure is lifelong. Epidemiological studies increasingly associate air pollution with multiple neurodevelopmental disorders and neurodegenerative diseases, findings supported by experimental animal models. This breadth of neurotoxicity across these central nervous system diseases and disorders likely reflects shared vulnerability of their inflammatory and oxidative stress-based mechanisms and a corresponding ability to produce brain metal dyshomeo-stasis. Future research to define the responsible contaminants of air pollution underlying this neurotoxicity is critical to understanding mechanisms of these diseases and disorders and protecting public health.

Organic extracts in PM2.5 are the major triggers to induce ferroptosis in SH-SY5Y cells

As a major air pollutant, PM2.5 can induce apoptosis of nerve cells, causing impairment of the learning and memory capabilities of humans and animals. Ferroptosis is a newly discovered way of programmed cell death. It is unclear whether the neurotoxicity induced by PM2.5 is related to the ferroptosis of nerve cells. In this study, we observed the changes in ferroptosis hallmarks of SH-SY5Y cells after exposure to various doses (40, 80, and 160 μg/mL PM2.5) for 24 h, exposure to 40 μg/mL PM2.5 for various times (24, 48, and 72 h), as well as exposure to various components (Po, organic extracts; Pw, water-soluble extracts; Pc, carbon core component). The results showed that PM2.5 reduced the cell viability, the content of GSH, and the activity of GSH-PX and SOD in SH-SY5Y cells with exposure dose and duration increasing. On the other hand, PM2.5 increased the content of iron, MDA, and the level of lipid ROS in SH-SY5Y cells with exposure dose and duration increasing. Additionally, PM2.5 reduced the expression levels of HO-1, NRF2, SLC7A11, and GPX4. The ferroptosis inhibitors Fer-1 and DFO significantly increase the cells viabilities and significantly reversed the changes of other above ferroptosis hallmarks. We also observed the different effects on ferroptosis hallmarks in the SH-SY5Y cells exposed to PM2.5 (160 μg/mL) and its various components (organic extracts, water-soluble extracts, and carbon core) for 24 h. We found that only the organic extracts shared similar results with PM2.5 (160 μg/mL). This study demonstrated that PM2.5 induced ferroptosis of SH-SY5Y cells, and organic extracts might be the primary component that caused ferroptosis.

Alzheimer's disease-like cortical atrophy mediates the effect of air pollution on global cognitive function

Little is known about the effect of air pollution on Alzheimer's disease (AD)-specific brain structural pathologies. There is also a lack of evidence on whether this effect leads to poorer cognitive function. We investigated whether, and the extent to which, AD-like cortical atrophy mediated the association between air pollution exposures and cognitive function in dementia-free adults. We used cross-sectional data from 640 participants who underwent brain magnetic resonance imaging and the Montreal Cognitive Assessment (MoCA). Mean cortical thickness (as the measure of global cortical atrophy) and machine learning-based AD-like cortical atrophy score were estimated from brain images. Concentrations of particulate matter with diameters ≤ 10 μm (PM₁₀) and ≤ 2.5 μm (PM_2.5) and nitrogen dioxide (NO₂) were estimated based on each participant's residential address. Following the product method, a mediation effect was tested by conducting a series of three regression analyses (exposure to outcome; exposure to mediator; and exposure and mediator to outcome). A 10 μg/m³ increase in PM₁₀ (β = -1.13; 95 % CI, -1.73 to -0.53) and a 10 ppb increase in NO₂ (β = -1.09; 95 % CI, -1.40 to -0.78) were significantly associated with a lower MoCA score. PM₁₀ (β = 0.27; 95 % CI, 0.06 to 0.48) and NO₂ (β = 0.35; 95 % CI, 0.25 to 0.45) were significantly associated with an increased AD-like cortical atrophy score. Effects of PM₁₀ and NO₂ on MoCA scores were significantly mediated by mean cortical thickness (proportions mediated: 25 %-28 %) and AD-like cortical atrophy scores (13 %-16 %). The findings suggest that air pollution exposures may induce AD-like cortical atrophy, and that this effect may lead to poorer cognitive function in dementia-free adults.

Associations Between Ambient Air Pollution and Cognitive Abilities from Midlife to Early Old Age: Modification by APOE Genotype

BACKGROUND

Fine particulate matter (PM2.5) and nitrogen dioxide (NO2) measures of ambient air pollution are associated with accelerated age-related cognitive impairment, and Alzheimer's disease and related dementias (ADRD).

OBJECTIVE

We examined associations between air pollution, four cognitive factors, and the moderating role of apolipoprotein E (APOE) genotype in the understudied period of midlife.

METHODS

Participants were ∼1,100 men in the Vietnam Era Twin Study of Aging. Baseline cognitive assessments were from 2003 to 2007. Measures included past (1993-1999) and recent (3 years prior to baseline assessment) PM2.5 and NO2 exposure, in-person assessment of episodic memory, executive function, verbal fluency, and processing speed, and APOE genotype. Average baseline age was 56 years with a 12-year follow-up. Analyses adjusted for health and lifestyle covariates.

RESULTS

Performance in all cognitive domains declined from age 56 to 68. Higher PM2.5 exposures were associated with worse general verbal fluency. We found significant exposure-by-APOE genotype interactions for specific cognitive domains: PM2.5 with executive function and NO2 with episodic memory. Higher PM2.5 exposure was related to worse executive function in APOE ɛ4 carriers, but not in non-carriers. There were no associations with processing speed.

CONCLUSION

These results indicate negative effects of ambient air pollution exposure on fluency alongside intriguing differential modifications of cognitive performance by APOE genotype. APOE ɛ4 carriers appeared more sensitive to environmental differences. The process by which air pollution and its interaction with genetic risk for ADRD affects risk for later life cognitive decline or progression to dementia may begin in midlife.

Acute effects of ambient nitrogen dioxide exposure on serum biomarkers of nervous system damage in healthy older adults

Ambient nitrogen dioxide (NO₂)-induced adverse health effects have been studied, but documented evidence on neural systems is limited. This study aimed to determine the acute effect of NO₂ exposure on nervous system damage biomarker levels in healthy older adults. Five rounds of follow-up among 34 healthy retired people were scheduled from December 2018 to April 2019 in Xinxiang, China. The real-time NO₂ concentrations were measured using a fixed site monitor. Serum samples were acquired during each round to measure nervous system damage biomarker levels: brain-derived neurotrophic factor (BDNF), neurofilament light chain (NfL), neuron-specific enolase (NSE), protein gene product 9.5 (PGP9.5), and S100 calcium-binding protein B (S100B). A linear mixed-effect model was incorporated to analyze the association between short-term NO₂ exposure and serum concentrations of the above-mentioned biomarkers. Stratification analysis based on sex, educational attainment, glutathione S-transferase theta 1 gene (GSTT1) polymorphism, and physical activity intensity was conducted to explore their potential modification effect. The NO₂ concentration ranged from 34.7 to 59.0 µg/m³ during the study period. Acute exposure to ambient NO₂ was significantly associated with elevated serum levels of NfL, PGP9.5, and BDNF. In response to a 10 µg/m³ increase in NO₂ concentration, NfL and PGP9.5 levels increased by 76 % (95 % confidence interval [CI]: 12-140 %) and 54 % (95 % CI: 1-107 %) on the lag0 day, respectively, while BDNF levels increased by 49 % (95 % CI: 2-96 %) at lag4 day. The estimated effect of NO₂ on NSE levels in GSTT1-sufficient participants was significantly higher than that in GSTT1-null participants. Intriguingly, the estimation of NO₂ on PGP9.5 levels in females was significantly higher than that in males. Most two-pollutant models showed robust results, except for O₃, which might have had confounding effects on NO₂-induced BDNF stimulation. In summary, acute exposure to NO₂ was associated with increased levels of serum nervous system damage biomarker levels including NFL, PGP9.5, and BDNF. The present study provided insights into NO₂ exposure-induced adverse neural effects.

Air Pollution: Possible Interaction between the Immune and Nervous System?

Exposure to environmental pollutants is a serious and common public health concern associated with growing morbidity and mortality worldwide, as well as economic burden. In recent years, the toxic effects associated with air pollution have been intensively studied, with a particular focus on the lung and cardiovascular system, mainly associated with particulate matter exposure. However, epidemiological and mechanistic studies suggest that air pollution can also influence skin integrity and may have a significant adverse impact on the immune and nervous system. Air pollution exposure already starts in utero before birth, potentially causing delayed chronic diseases arising later in life. There are, indeed, time windows during the life of individuals who are more susceptible to air pollution exposure, which may result in more severe outcomes. In this review paper, we provide an overview of findings that have established the effects of air pollutants on the immune and nervous system, and speculate on the possible interaction between them, based on mechanistic data.

Annual exposure to PM10 is related to cerebral small vessel disease in general adult population

Ambient air pollution is one of the most important global health issues. Although several studies have been reported the associations between air pollution and brain function or structure, impact of the air pollution on cerebral small vessel disease (cSVD) have rarely been explored in Asian adult population. We evaluated the association between exposure to air pollutants and cSVD in Korean asymptomatic adults. This cross-sectional study included 3257 participants of a health screening program from January 2006 to December 2013. All participants performed brain magnetic resonance imaging. To assess the cSVD, we considered three features such as white matter hyperintensities (WMH), silent lacunar infarction (SLI), and cerebral microbleeds (CMBs). The annual average exposure to air pollutants [particulate matter ≤ 10 μm in aerodynamic diameter (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO)] was generated. The mean [standard deviation (SD)] age of the total 3257 participants was 56.5 (9.5) years, and 54.0% of them were male. Among all the included participants, 273 (8.4%) had SLI and 135 (4.1%) had CMBs. The mean volume (± SD) of WMH was 2.72 ± 6.57 mL. In result of linear regression analysis, the volume of WMH was associated with various potential factors including age, height, weight, smoking and alcohol consumption status, blood pressure (BP), hypertension, and diabetes mellitus. SLI-positive group, compared to the SLI-negative group, was older, shorter, and had higher BP as well as higher frequency of hypertension and diabetes mellitus. After adjusting for covariates, the annual average concentration of PM₁₀ was significantly associated with the volume of WMH [β (95% CI) for Model 1 = 0.082 (0.038- 0.125), p < 0.001; β (95% CI) for Model 2 = 0.060 (0.013, 0.107), p = 0.013]. CMBs were not associated with the annual average concentration of PM₁₀. No significant associations of NO₂, SO₂, and CO with cSVD were observed. In conclusion, PM₁₀ exposure is associated with significant increases in brain WMH' volume and silent lacunar infarcts in asymptomatic adults.

Carbonaceous Nanoparticle Air Pollution: Toxicity and Detection in Biological Samples

Among the different air pollutants, particulate matter (PM) is of great concern due to its abundant presence in the atmosphere, which results in adverse effects on the environment and human health. The different components of PM can be classified based on their physicochemical properties. Carbonaceous particles (CPs) constitute a major fraction of ultrafine PM and have the most harmful effects. Herein, we present a detailed overview of the main components of CPs, e.g., carbon black (CB), black carbon (BC), and brown carbon (BrC), from natural and anthropogenic sources. The emission sources and the adverse effects of CPs on the environment and human health are discussed. Particularly, we provide a detailed overview of the reported toxic effects of CPs in the human body, such as respiratory effects, cardiovascular effects, neurodegenerative effects, carcinogenic effects, etc. In addition, we also discuss the challenges faced by and limitations of the available analytical techniques for the qualitative and quantitative detection of CPs in atmospheric and biological samples. Considering the heterogeneous nature of CPs and biological samples, a detailed overview of different analytical techniques for the detection of CPs in (real-exposure) biological samples is also provided. This review provides useful insights into the classification, toxicity, and detection of CPs in biological samples.

Prenatal exposure to PM2.5 and childhood cognition: Accounting for between-site heterogeneity in a pooled analysis of ECHO cohorts in the Northeastern United States

BACKGROUND

Emerging studies have investigated the adverse health effects of PM_2.5 using data from multiple cohorts, and results often are not generalizable across cohorts. We aimed to assess associations between prenatal PM_2.5 and childhood cognition in two U.S. cohorts while accounting for between-site heterogeneity.

METHODS

Analyses included 348 mother-child dyads enrolled in the dual site (New York City and Boston) PRogramming of Intergenerational Stress Mechanisms (PRISM) cohort and in the First Thousand Days of Life (FTDL) study (Northern Virginia) participating in the Environmental influences on Child Health Outcomes (ECHO) national consortium. Residential prenatal PM_2.5 exposure was estimated using a validated satellite-based model and childhood cognition was measured using the NIH Toolbox Cognition Battery at three to eight years of age. We used a log-linear model applied to contingency tables formed by cross-classifying covariates by site to examine between-site heterogeneity using 3^rd trimester PM_2.5 exposure, age-corrected cognition scores, and covariates potentially causing heterogeneities. Multivariable linear regression models informed by the combinability analysis were used to estimate the coefficients and 95% confidence intervals (CIs) for the association between 3^rd trimester PM_2.5 exposure and age-corrected cognition scores (mean = 100, SD = 15).

RESULTS

The log-linear model indicated that inter-study associations were similar between PRISM-NYC and FTDL, which were different from those in PRISM-Boston. Accordingly, we combined the data of PRISM-NYC and FTDL cohorts. We observed associations between 3^rd trimester PM_2.5 and cognition scores, findings were varying by site, childsex, and test. For example, a 1 μg/m³ increase of 3^rd trimester PM_2.5 was associated with -4.35 (95% CI = -8.73, -0.25) mean early childhood cognition scores in females in PRISM-Boston. In the pooled NYC + FTDL site, the association between PM_2.5 and childhood cognition may be modified by maternal education and urbanicity.

CONCLUSIONS

We found associations between prenatal PM_2.5 and impaired childhood cognition. Since multi-site analyses are increasingly conducted, our findings suggest the needed awareness of between-site heterogeneity.

B vitamin intakes modify the association between particulate air pollutants and incidence of all-cause dementia: Findings from the Women's Health Initiative Memory Study

INTRODUCTION

Particulate air pollutants may induce neurotoxicity by increasing homocysteine levels, which can be lowered by high B vitamin intakes. Therefore, we examined whether intakes of three B vitamins (folate, B12 , and B6 ) modified the association between PM2.5 exposure and incidence of all-cause dementia.

METHODS

This study included 7183 women aged 65 to 80 years at baseline. B vitamin intakes from diet and supplements were estimated by food frequency questionnaires at baseline. The 3-year average PM2.5 exposure was estimated using a spatiotemporal model.

RESULTS

During a mean follow-up of 9 years, 342 participants developed all-cause dementia. We found that residing in locations with PM2.5 exposure above the regulatory standard (12 μg/m3 ) was associated with a higher risk of dementia only among participants with lower intakes of these B vitamins.

DISCUSSION

This is the first study suggesting that the putative neurotoxicity of PM2.5 exposure may be attenuated by high B vitamin intakes.

Size-Based Effects of Anthropogenic Ultrafine Particles on Lysosomal TRPML1 Channel and Autophagy in Motoneuron-like Cells

Background: An emerging body of evidence indicates an association between anthropogenic particulate matter (PM) and neurodegeneration. Although the historical focus of PM toxicity has been on the cardiopulmonary system, ultrafine PM particles can also exert detrimental effects in the brain. However, only a few studies are available on the harmful interaction between PM and CNS and on the putative pathomechanisms. Methods: Ultrafine PM particles with a diameter < 0.1 μm (PM0.1) and nanoparticles < 20 nm (NP20) were sampled in a lab-scale combustion system. Their effect on cell tracking in the space was studied by time-lapse and high-content microscopy in NSC-34 motor neurons while pHrodo™ Green conjugates were used to detect PM endocytosis. Western blotting analysis was used to quantify protein expression of lysosomal channels (i.e., TRPML1 and TPC2) and autophagy markers. Current-clamp electrophysiology and Fura2-video imaging techniques were used to measure membrane potential, intracellular Ca2+ homeostasis and TRPML1 activity in NSC-34 cells exposed to PM0.1 and NP20. Results: NP20, but not PM0.1, reduced NSC-34 motor neuron movement in the space. Furthermore, NP20 was able to shift membrane potential of motor neurons toward more depolarizing values. PM0.1 and NP20 were able to enter into the cells by endocytosis and exerted mitochondrial toxicity with the consequent stimulation of ROS production. This latter event was sufficient to determine the hyperactivation of the lysosomal channel TRPML1. Consequently, both LC3-II and p62 protein expression increased after 48 h of exposure together with AMPK activation, suggesting an engulfment of autophagy. The antioxidant molecule Trolox restored TRPML1 function and autophagy. Conclusions: Restoring TRPML1 function by an antioxidant agent may be considered a protective mechanism able to reestablish autophagy flux in motor neurons exposed to nanoparticles.

Association between Long-Term Air Pollution, Chronic Traffic Noise, and Resting-State Functional Connectivity in the 1000BRAINS Study

BACKGROUND

Older adults show a high variability in cognitive performance that cannot be explained by aging alone. Although research has linked air pollution and noise to cognitive impairment and structural brain alterations, the potential impact of air pollution and noise on functional brain organization is unknown.

OBJECTIVE

This study examined the associations between long-term air pollution and traffic noise with measures of functional brain organization in older adults. We hypothesize that exposures to high air pollution and noise levels are associated with age-like changes in functional brain organization, shown by less segregated brain networks.

METHODS

Data from 574 participants (44.1% female, 56-85 years of age) in the German 1000BRAINS study (2011-2015) were analyzed. Exposure to particulate matter (PM10, PM2.5, and PM2.5 absorbance), accumulation mode particle number (PNAM), and nitrogen dioxide (NO2) was estimated applying land-use regression and chemistry transport models. Noise exposures were assessed as weighted 24-h (Lden) and nighttime (Lnight) means. Functional brain organization of seven established brain networks (visual, sensorimotor, dorsal and ventral attention, limbic, frontoparietal and default network) was assessed using resting-state functional brain imaging data. To assess functional brain organization, we determined the degree of segregation between networks by comparing the strength of functional connections within and between networks. We estimated associations between air pollution and noise exposure with network segregation, applying multiple linear regression models adjusted for age, sex, socioeconomic status, and lifestyle variables.

RESULTS

Overall, small associations of high exposures with lesser segregated networks were visible. For the sensorimotor networks, we observed small associations between high air pollution and noise and lower network segregation, which had a similar effect size as a 1-y increase in age [e.g., in sensorimotor network, -0.006 (95% CI: -0.021, 0.009) per 0.3 ×10-5/m increase in PM2.5 absorbance and -0.004 (95% CI: -0.006, -0.002) per 1-y age increase].

CONCLUSION

High exposure to air pollution and noise was associated with less segregated functional brain networks. https://doi.org/10.1289/EHP9737.

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.

White matter pathology in alzheimer's transgenic mice with chronic exposure to low-level ambient fine particulate matter

BACKGROUND

Air pollution, especially fine particulate matter (PM), can cause brain damage, cognitive decline, and an increased risk of neurodegenerative disease, especially alzheimer's disease (AD). Typical pathological findings of amyloid and tau protein accumulation have been detected in the brain after exposure in animal studies. However, these observations were based on high levels of PM exposure, which were far from the WHO guidelines and those present in our environment. In addition, white matter involvement by air pollution has been less reported. Thus, this experiment was designed to simulate the true human world and to discuss the possible white matter pathology caused by air pollution.

RESULTS

6 month-old female 3xTg-AD mice were divided into exposure and control groups and housed in the Taipei Air Pollutant Exposure System (TAPES) for 5 months. The mice were subjected to the Morris water maze test after exposure and were then sacrificed with brain dissection for further analyses. The mean mass concentration of PM2.5 during the exposure period was 13.85 μg/m3. After exposure, there was no difference in spatial learning function between the two groups, but there was significant decay of memory in the exposure group. Significantly decreased total brain volume and more neuronal death in the cerebral and entorhinal cortex and demyelination of the corpus callosum were noted by histopathological staining after exposure. However, there was no difference in the accumulation of amyloid or tau on immunohistochemistry staining. For the protein analysis, amyloid was detected at significantly higher levels in the cerebral cortex, with lower expression of myelin basic protein in the white matter. A diffuse tensor image study also revealed insults in multiple white matter tracts, including the optic tract.

CONCLUSIONS

In conclusion, this pilot study showed that even chronic exposure to low PM2.5 concentrations still caused brain damage, such as gross brain atrophy, cortical neuron damage, and multiple white matter tract damage. Typical amyloid cascade pathology did not appear prominently in the vulnerable brain region after exposure. These findings imply that multiple pathogenic pathways induce brain injury by air pollution, and the optic nerve may be another direct invasion route in addition to olfactory nerve.

Mental and Physical Stress Responses to Personal Ultrafine Particle Exposure in Adolescents

Incidence rates of mental health disorders among adolescents is increasing, indicating a strong need for effective prevention efforts at a population level. The etiology of mental health disorders includes genetic, social, and environmental factors. Ultrafine particles (UFPs; particles less than 0.1 μm in diameter) have been shown to exert neurotoxic effects on the brain; however, epidemiologic evidence on the relationship between UFPs and childhood mental health outcomes is unclear. The objective of this study was to determine if exposure to UFPs was associated with symptoms of mental health in adolescents. Adolescents completed personal UFP monitoring for one week as well as a series of validated Patient-Reported Outcomes Measurement Information System (PROMIS) assessments to measure five domains of mental and physical stress symptoms. Multivariable linear regression models were used to estimate the association between PROMIS domain T-scores and median weekly personal UFP exposure with the inclusion of interactions to explore sex differences. We observed that median weekly UFP exposure was significantly associated with physical stress symptoms (β: 5.92 per 10-fold increase in UFPs, 95% CI [0.72, 11.13]) but no other measured domains. Further, we did not find effect modification by sex on any of the PROMIS outcomes. The results of this study indicate UFPs are associated with physical symptoms of stress response among adolescents, potentially contributing to mental health disorders in this population.

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

Exposure to fine particulate matter (PM_2.5) is associated with various adverse health effects, such as respiratory and cardiovascular diseases. This study aimed to evaluate the association of PM_2.5 with neural damage biomarkers. A total of 34 healthy retirees were recruited from Xinxiang Medical University from December 2018 to April 2019. Concentrations of PM_2.5 constituents including 24 metals and nonmetallic elements and 6 ions, and 5 biomarkers of neural damage including brain-derived neurotrophic factor (BDNF), neurofilament light chain (NfL), neuron-specific enolase (NSE), protein gene product 9.5 (PGP9.5), and S100 calcium-binding protein B (S100B) in serum were measured. A linear mixed-effect model was employed to estimate the association of PM_2.5 and its constituents with neural damage biomarkers. Modification effects of glutathione S-transferase theta 1 gene (GSTT1) polymorphism, sex, education, and physical activity on PM_2.5 exposure with neural damage were explored. PM_2.5 and its key constituents were significantly associated with neural damage biomarkers. A 10 μg/m³ increase in PM_2.5 concentration was associated with 2.09% (95% CI, 39.3-76.5%), 100% (95% CI, 1.73-198%), and 122% (95% CI, 20.7-222%) increments in BDNF, NfL, and PGP9.5, respectively. Several constituents such as Cu, Zn, Ni, Mn, Sn, V, Rb, Pb, Al, Be, Cs, Co, Th, U, Cl^-, and F^- were significantly associated with NfL. The estimated association of PM_2.5 with NSE in GSTT1-sufficient volunteers was significantly higher than that in GSTT1-null volunteers. Therefore, short-term PM_2.5 exposure was associated with neural damage, and GSTT1 expression levels modified the PM_2.5-induced adverse neural effects.

Advanced human developmental toxicity and teratogenicity assessment using human organoid models

Tremendous progress has been made in the field of toxicology leading to the advance of developmental toxicity assessment. Conventional animal models and in vitro two-dimensional models cannot accurately describe toxic effects and predict actual in vivo responses due to obvious inter-species differences between humans and animals, as well as the lack of a physiologically relevant tissue microenvironment. Human embryonic stem cell (hESC)- and induced pluripotent stem cell (iPSC)-derived three-dimensional organoids are ideal complex and multicellular organotypic models, which are indispensable in recapitulating morphogenesis, cellular interactions, and molecular processes of early human organ development. Recently, human organoids have been used for drug discovery, chemical toxicity and safety in vitro assessment. This review discusses the recent advances in the use of human organoid models, (i.e., brain, retinal, cardiac, liver, kidney, lung, and intestinal organoid models) for developmental toxicity and teratogenicity assessment of distinct tissues/organs following exposure to pharmaceutical compounds, heavy metals, persistent organic pollutants, nanomaterials, and ambient air pollutants. Combining next-generation organoid models with innovative engineering technologies generates novel and powerful tools for developmental toxicity and teratogenicity assessment, and the rapid progress in this field is expected to continue.

Impact of air pollution exposure on the risk of Alzheimer's disease in China: A community-based cohort study

Alzheimer's disease (AD) is the most common type of dementia. Impact of air pollution (AP) on the risk of AD is unclear. It is unknown which air pollutants are independently associated with AD and whether fish consumption mitigated the association. We carried out a community-based cohort of 6115 participants aged ≥60 years in China to examine the association of PM_2.5, PM₁₀, CO, NO₂, SO₂ and O₃ exposure with AD, and differences in the association between people with low and high consumption of fish. The participants were randomly recruited from six counties in Zhejiang province for health survey to document socio-demographic and disease risk factors in 2014, and were followed up to diagnose AD in 2019. A total of 986 cohort members were diagnosed with AD. Based on the daily mean air pollutants monitored in 2013-2015 in the counties, participants were divided into low, middle and high AP exposure groups for subsequent analysis. The multiple adjusted odds ratio (OR) of AD in participants living with the middle and high levels of PM_2.5 exposure versus the low exposure were 1.50 (95% CI 0.90-2.50) and 3.92 (2.09-7.37). The increased ORs were also with PM₁₀ (1.74, 0.65-4.64; 3.00, 1.22-7.41) and CO (2.86, 1.32-6.20; 1.19, 0.45-3.18), but not with NO₂ (0.63, 0.17-2.27; 0.95, 0.28-3.19), SO₂ (0.44, 0.19-1.001; 1.21, 0.56-2.62), and O₃ (0.38, 0.20-0.74; 0.50, 0.21-1.21). There were no significant interaction effects of AP with fish consumption on AD. However, participants with low consumption of fish appeared to have higher ORs in PM_2.5 exposure (1.80, 1.39-2.33; 5.18, 3.93-6.82) than those high consumption (1.38, 0.78-2.47; 2.89, 1.50-5.59). Our findings of PM_2.5, PM₁₀ and CO exposure significantly increased the risk of AD and the potential mitigating effect of fish consumption on the association provide evidence for developing effective strategies for AD reduction and air pollution control.

The association between air pollutants and hippocampal volume from magnetic resonance imaging: A systematic review and meta-analysis

Growing epidemiological evidence suggests that air pollution may increase the risk of cognitive decline and neurodegenerative disease. A hallmark of neurodegeneration and an important diagnostic biomarker is volume reduction of a key brain structure, the hippocampus. We aimed to investigate the possibility that outdoor air nitrogen dioxide (NO₂) and particulate matter with diameter ≤2.5 μm (PM_2.5) and ≤10 μm (PM₁₀) adversely affect hippocampal volume, through a meta-analysis. We considered studies that assessed the relation between outdoor air pollution and hippocampal volume by structural magnetic resonance imaging in adults and children, searching in Pubmed and Scopus databases from inception through July 13, 2021. For inclusion, studies had to report the correlation coefficient along with its standard error or 95% confidence interval (CI) between air pollutant exposure and hippocampal volume, to use standard space for neuroimages, and to consider at least age, sex and intracranial volume as covariates or effect modifiers. We meta-analyzed the data with a random-effects model, considering separately adult and child populations. We retrieved four eligible studies in adults and two in children. In adults, the pooled summary β regression coefficients of the association of PM_2.5, PM₁₀ and NO₂ with hippocampal volume showed respectively a stronger association (summary β -7.59, 95% CI -14.08 to -1.11), a weaker association (summary β -2.02, 95% CI -4.50 to 0.47), and no association (summary β -0.44, 95% CI -1.27 to 0.40). The two studies available for children, both carried out in preadolescents, did not show an association between PM_2.5 and hippocampal volume. The inverse association between PM_2.5 and hippocampal volume in adults appeared to be stronger at higher mean PM_2.5 levels. Our results suggest that outdoor PM_2.5 and less strongly PM₁₀ could adversely affect hippocampal volume in adults, a phenomenon that may explain why air pollution has been related to memory loss, cognitive decline, and dementia.