Repeated Iron-Soot Exposure and Nose-to-brain Transport of Inhaled Ultrafine Particles

Fine particulate matter components associated with exacerbated depressive symptoms among middle-aged and older adults in China

Growing awareness acknowledges ambient fine particulate matter (PM2.5) as an environmental risk factor for mental disorders, especially among older people. However, there remains limited evidence regarding which specific chemical components of PM2.5 may be more detrimental. This nationwide prospective cohort study included 22,126 middle-aged and older adult participants of the China Health and Retirement Longitudinal Study (CHARLS, 2011-2016), to explore the individual and joint associations between long-term exposure to various PM2.5 components (sulfate, nitrate, ammonium, organic matter, and black carbon) and depressive symptoms. The depressive symptoms were assessed using the 10-item Center for Epidemiological Studies-Depression Scale (CES-D-10). Using the novel quantile-based g-computation for multi-pollutant mixture analysis, we found that exposure to the mixture of major PM2.5 components was significantly associated with aggravating depressive symptoms, with the exposure-response curve exhibiting consistent linear or supra-linear shape without a lower threshold. The estimated weight index indicated that, among major PM2.5 components, only nitrate, sulfate, and black carbon significantly contributed to the exacerbation of depressive symptoms. Given the expanding aging population, stricter regulation on the emissions of particularly toxic PM2.5 components may mitigate the escalating disease burden of depression.

Long-term effect of fine particulate matter constituents on reproductive hormones homeostasis in women attending assisted reproductive technologies: A population-based longitudinal study

Fine particulate matter (PM2.5) may disrupt women's reproductive hormones, posing potential reproductive risks. However, the exact compositions of PM2.5 responsible for these effects remain unclear. Our investigation explored the long-term impacts of PM2.5 constituents on reproductive hormones, based on a large longitudinal assisted reproductive cohort study in Anhui, China. We included 24,396 reproductive hormone samples from 19,845 women attending assisted reproductive technologies (ART) between 2014 and 2020. Using high-resolution gridded data (1-km resolution), we calculated the residence-specified PM2.5 constituents during the year before the month of hormone testing. Relationships between PM2.5 constituents [organic matter (OM), chloride (Cl-), sulfate (SO42-), ammonium (NH4+), black carbon, and nitrate] and reproductive hormones were investigated using the linear mixed model with subject-specific intercepts. The constituent-proportion model and the constituent-residual model were also constructed. Additionally, cubic spline analysis was used to examine the potential non-linear exposure-response relationship. We found that per interquartile range (IQR) increment in OM was associated with a 5.31 % (3.74 %, 6.89 %) increase in estradiol, and per IQR increment in Cl- and NH4+ were associated with 13.56 % (7.63 %, 19.82 %) and 9.07 % (4.35 %, 14.01 %) increases in luteinizing hormone. Conversely, per IQR increment in OM and Cl- were associated with -7.27 % (-9.34 %, -5.16 %) and -8.52 % (-10.99 %, -5.98 %) decreases in progesterone, and per IQR increment in SO42- was associated with a -9.15 % (-10.31 %, -7.98 %) decrease in testosterone. These associations were held in both proportional and residual models. Moreover, exposure-response curves for estradiol and progesterone with PM2.5 constituents exhibited approximately U-shaped. These results suggested that specific PM2.5 constituents might disrupt reproductive hormone homeostasis in women attending ART, providing new evidence for formulating PM2.5 pollution reduction strategies that could benefit women's reproductive health.

Soot nanoparticles promote ferroptosis in dopaminergic neurons via alteration of m6A RNA methylation in Parkinson's disease

Soot nanoparticles (SNPs) are black carbon prevalent in atmospheric environment with significant impacts on public health, leading to neurodegenerative diseases including development of Parkinson's disease (PD). This study investigated the effects of SNPs exposure on PD symptoms, employing both in vivo and in vitro PD models. In the in vivo experiments, animal behavior assessments showed that SNPs exposure exacerbated motor and cognitive impairments in PD mice. Molecular biology techniques further unveiled that SNPs aggravated degeneration of dopaminergic neurons. In vitro experiments revealed that SNPs exposure intensified ferroptosis of PD cells by increasing reactive oxygen species and iron ion levels, while reducing glutathione levels and mitochondrial membrane potential. Sequencing tests indicated elevated N6-methyladenosine (m6A) alteration of the ferroptosis-related protein, acyl-CoA synthetase long chain family member 4 (ACSL4). This study demonstrates that SNPs may exacerbate the onset and progression of PD by recruiting YTH domain-containing family protein 1 (YTHDF1) protein, enhancing m6A methylation in the ACSL4 5'UTR, amplifying ACSL4 protein expression, and accelerating the ferroptosis process in dopaminergic neurons. These molecular mechanisms underlying SNPs exacerbation of PD development may provide crucial insights for formulating environmental safety regulations and potential therapeutic strategies addressing PD in populations residing in regions with varied air quality.

Exposure to PM2.5 and its constituents is associated with metabolic dysfunction-associated fatty liver disease: a cohort study in Northwest of China

Accumulating animal studies have demonstrated associations between ambient air pollution (AP) and metabolic dysfunction-associated fatty liver disease (MAFLD), but relevant epidemiological evidence is limited. We evaluated the association of long-term exposure to AP with the risk of incident MAFLD in Northwest China. The average AP concentration between baseline and follow-up was used to assess individual exposure levels. Cox proportional hazard models and restricted cubic spline functions (RCS) were used to estimate the association of PM2.5 and its constituents with the risk of MAFLD and the dose-response relationship. Quantile g-computation was used to assess the joint effects of mixed exposure to air pollutants on MAFLD and the weights of the various pollutants. We observed 1516 cases of new-onset MAFLD, with an incidence of 10.89%. Increased exposure to pollutants was significantly associated with increased odds of MAFLD, with hazard ratios (HRs) of 2.93 (95% CI: 1.22, 7.00), 2.86 (1.44, 5.66), 7.55 (3.39, 16.84), 4.83 (1.89, 12.38), 3.35 (1.35, 8.34), 1.89 (1.02, 1.62) for each interquartile range increase in PM2.5, SO42-, NO3-, NH4+, OM, and BC, respectively. Stratified analyses suggested that females, frequent exercisers and never-drinkers were more susceptible to MAFLD associated with ambient PM2.5 and its constituents. Mixed exposure to SO42-, NO3-, NH4+, OM and BC was associated with an increased risk of MAFLD, and the weight of BC had the strongest effect on MAFLD. Exposure to ambient PM2.5 and its constituents increased the risk of MAFLD.

Source-Specific Air Pollution and Loss of Independence in Older Adults Across the US

Importance

Air pollution is a recognized risk factor associated with chronic diseases, including respiratory and cardiovascular conditions, which can lead to physical and cognitive impairments in later life. Although these losses of function, individually or in combination, reduce individuals' likelihood of living independently, little is known about the association of air pollution with this critical outcome.

Objective

To investigate associations between air pollution and loss of independence in later life.

Design, Setting, and Participants

This cohort study was conducted as part of the Environmental Predictors Of Cognitive Health and Aging study and used 1998 to 2016 data from the Health and Retirement Study. Participants included respondents from this nationally representative, population-based cohort who were older than 50 years and had not previously reported a loss of independence. Analyses were performed from August 31 to October 15, 2023.

Exposures

Mean 10-year pollutant concentrations (particulate matter less than 2.5 μm in diameter [PM2.5] or ranging from 2.5 μm to 10 μm in diameter [PM10-2.5], nitrogen dioxide [NO2], and ozone [O3]) were estimated at respondent addresses using spatiotemporal models along with PM2.5 levels from 9 emission sources.

Main Outcomes and Measures

Loss of independence was defined as newly receiving care for at least 1 activity of daily living or instrumental activity of daily living due to health and memory problems or moving to a nursing home. Associations were estimated with generalized estimating equation regression adjusting for potential confounders.

Results

Among 25 314 respondents older than 50 years (mean [SD] baseline age, 61.1 [9.4] years; 11 208 male [44.3%]), 9985 individuals (39.4%) experienced lost independence during a mean (SD) follow-up of 10.2 (5.5) years. Higher exposure levels of mean concentration were associated with increased risks of lost independence for total PM2.5 levels (risk ratio [RR] per 1-IQR of 10-year mean, 1.05; 95% CI, 1.01-1.10), PM2.5 levels from road traffic (RR per 1-IQR of 10-year mean, 1.09; 95% CI, 1.03-1.16) and nonroad traffic (RR per 1-IQR of 10-year mean, 1.13; 95% CI, 1.03-1.24), and NO2 levels (RR per 1-IQR of 10-year mean, 1.05; 95% CI, 1.01-1.08). Compared with other sources, traffic-generated pollutants were most consistently and robustly associated with loss of independence; only road traffic-related PM2.5 levels remained associated with increased risk after adjustment for PM2.5 from other sources (RR per 1-IQR increase in 10-year mean concentration, 1.10; 95% CI, 1.00-1.21). Other pollutant-outcome associations were null, except for O3 levels, which were associated with lower risks of lost independence (RR per 1-IQR increase in 10-year mean concentration, 0.94; 95% CI, 0.92-0.97).

Conclusions and Relevance

This study found that long-term exposure to air pollution was associated with the need for help for lost independence in later life, with especially large and consistent increases in risk for pollution generated by traffic-related sources. These findings suggest that controlling air pollution could be associated with diversion or delay of the need for care and prolonged ability to live independently.

Automated SEM/EDX imaging for the in-depth characterization of non-exhaust traffic emissions from the Munich subway system

A SEM/EDX based automated measurement and classification algorithm was tested as a method for the in-depth analysis of micro-environments in the Munich subway using a custom build mobile measurements system. Sampling was conducted at platform stations, to investigate the personal exposure of commuters to subway particulate matter during platform stays. EDX spectra and morphological features of all analyzed particles were automatically obtained and particles were automatically classified based on pre-defined chemical and morphological boundaries. Source apportionment for individual particles, such as abrasion processes at the wheel-brake interface, was partially possible based on the established particle classes. An average of 98.87 ± 1.06 % of over 200,000 analyzed particles were automatically assigned to the pre-defined classes, with 84.68 ± 16.45 % of particles classified as highly ferruginous. Manual EDX analysis further revealed, that heavy metal rich particles were also present in the ultrafine size range well below 100 nm.

Nose-to-brain delivery of nanotherapeutics: Transport mechanisms and applications

The blood-brain barrier presents a key limitation to the administration of therapeutic molecules for the treatment of brain disease. While drugs administered orally or intravenously must cross this barrier to reach brain targets, the unique anatomical structure of the olfactory system provides a route to deliver drugs directly to the brain. Entering the brain via receptor, carrier, and adsorption-mediated transcytosis in the nasal olfactory and trigeminal regions has the potential to increase drug delivery. In this review, we introduce the physiological and anatomical structures of the nasal cavity, and summarize the possible modes of transport and the relevant receptors and carriers in the nose-to-brain pathway. Additionally, we provide examples of nanotherapeutics developed for intranasal drug delivery to the brain. Further development of nanoparticles that can be applied to intranasal delivery systems promises to improve drug efficacy and reduce drug resistance and adverse effects by increasing molecular access to the brain. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease.

Exposure to ambient black carbon and particulate matter during pregnancy in associations with risk of pre-eclampsia: A meta-analysis based on population-based studies

Air pollution control protocols and policies formulated for PM2.5 and PM10 (particulate matter [PM] with an aerodynamic diameter of ≤2.5 and 10 μm), however, such protocols and policies have not been available for black carbon (BC). A growing number of studies have evaluated the association between long-term exposure to ambient air pollution with BC and PM and pre-eclampsia. We applied a meta-analysis to estimate pooled odds ratios (ORs) and 95 % confidence intervals (CIs) based on four exposure windows (first/second/third trimester and entire pregnancy). 24 studies meeting our selection criteria (8 for BC, 21 and 15 for PM2.5 and PM10) were finally included after screening studies published up to June 22, 2023. An increase of 1 μg/m3 BC during the second trimester and entire pregnancy were associated with a 16 % (OR: 1.16, 95 % CI: [1.02, 1.32]) and a 15 % (OR: 1.15, 95 % CI: [1.03, 1.29]) increased risk of pre-eclampsia, respectively. A 10 μg/m3 increase in second-trimester exposure to PM2.5 and PM10 was associated with a 1 % (OR: 1.01, 95 % CI: [1.00, 1.03]) and a 5 % (OR: 1.05, 95 % CI: [1.01, 1.10]) increased risk of pre-eclampsia. An 11 % (OR: 1.11, 95 % CI: [1.03, 1.21]) increased risk of pre-eclampsia was found to be associated with a 10 μg/m3 increase in PM10 exposure during the entire pregnancy. The results support the potential effect of exposure to ambient particulate pollutants on risk of pre-eclampsia and emphasize the necessity of strategies and protocols for controlling BC. Greater efforts in controlling ambient particulate pollution and especially BC are needed in order to prevent pregnant women from developing pre-eclampsia.

Ambient PM2.5 components and prevalence of chronic kidney disease: a nationwide cross-sectional survey in China

OBJECTIVES

Chronic kidney disease (CKD) is a global public health concern, and accumulating evidence has indicated that air pollution increases the odds of CKD. However, a limited number of studies have examined the long-term effects of ambient fine particulate matter (PM2.5) components on the risk of CKD among general population; thus, major knowledge gaps remain.

METHODS

Using data from a nationwide representative cross-sectional survey in China and a validated PM2.5 composition dataset, we established generalized linear models to quantify the association between five major components of PM2.5 and CKD prevalence.

RESULTS

There were significant associations between long-term exposure to three PM2.5 components [including black carbon (BC), sulfate (SO42-), organic matter (OM)] and increased odds of CKD prevalence. Along with an interquartile range (IQR) increment in BC (3.3 μg/m3), SO42- (9.7 μg/m3), and OM (16.2 μg/m3) at a 4-year moving average, the odds ratios (ORs) for CKD prevalence were 1.28 (95% CI 1.07, 1.54), 1.23 (95% CI 1.03, 1.45), and 1.23 (95% CI 1.02, 1.47), respectively. We did not detect any significant association of the other two PM2.5 components [nitrate (NO3-) or ammonium (NH4+)] with CKD prevalence. Stratified analyses revealed no differences (P ≥ 0.05) in the effect estimates of subgroups based on administrative region, sex, age, and other demographic characteristics. For instance, along with an IQR increment in BC at a 4-year moving average, the ORs of CKD prevalence among males and females were 1.30 (95% CI 0.98, 1.73) and 1.29 (95% CI 1.01, 1.65), respectively. The odds of CKD were generally higher with increasing PM2.5 composition concentration.

CONCLUSIONS

Our study demonstrated that long-term exposure to specific PM2.5 components including BC, SO42-, and OM increased CKD risk in the general population. This study could provide new insights into source-directed PM2.5 control and CKD prevention.

Characterizing the neuroimmune environment of offspring in a novel model of maternal allergic asthma and particulate matter exposure

Inflammation during pregnancy is associated with an increased risk for neurodevelopmental disorders (NDD). Increased gestational inflammation can be a result of an immune condition/disease, exposure to infection, and/or environmental factors. Epidemiology studies suggest that cases of NDD are on the rise. Similarly, rates of asthma are increasing, and the presence of maternal asthma during pregnancy increases the likelihood of a child being later diagnosed with NDD such as autism spectrum disorders (ASD). Particulate matter (PM), via air pollution, is an environmental factor known to worsen the symptoms of asthma, but also, PM has been associated with increased risk of neuropsychiatric disorders. Despite the links between asthma and PM with neuropsychiatric disorders, there is a lack of laboratory models investigating combined prenatal exposure to asthma and PM on offspring neurodevelopment. Thus, we developed a novel mouse model that combines exposure to maternal allergic asthma (MAA) and ultrafine iron-soot (UIS), a common component of PM. In the current study, female BALB/c mice were sensitized for allergic asthma with ovalbumin (OVA) prior to pregnancy. Following mating and beginning on gestational day 2 (GD2), dams were exposed to either aerosolized OVA to induce allergic asthma or phosphate buffered saline (PBS) for 1 h. Following the 1-h exposure, pregnant females were then exposed to UIS with a size distribution of 55 to 169 nm at an average concentration of 176 ± 45 μg/m3) (SD), or clean air for 4 h, over 8 exposure sessions. Offspring brains were collected at postnatal days (P)15 and (P)35. Cortices and hippocampal regions were then isolated and assessed for changes in cytokines using a Luminex bead-based multiplex assay. Analyses identified changes in many cytokines across treatment groups at both timepoints in the cortex, including interleukin-1 beta (IL-1β), and IL-17, which remained elevated from P15 to P35 in all treatment conditions compared to controls. There was a suppressive effect of the combined MAA plus UIS on the anti-inflammatory cytokine IL-10. Potentially shifting the cytokine balance towards more neuroinflammation. In the hippocampus at P15, elevations in cytokines were also identified across the treatment groups, namely IL-7. The combination of MAA and UIS exposure (MAA-UIS) during pregnancy resulted in an increase in microglia density in the hippocampus of offspring, as identified by IBA-1 staining. Together, these data indicate that exposure to MAA, UIS, and MAA-UIS result in changes in the neuroimmune environment of offspring that persist into adulthood.

Characterizing the Neuroimmune Environment of Offspring in a Novel Model of Maternal Allergic Asthma and Particulate Matter Exposure

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by the presence of decreased social interactions and an increase in stereotyped and repetitive behaviors. Epidemiology studies suggest that cases of ASD are on the rise. Similarly, rates of asthma are increasing, and the presence of maternal asthma during pregnancy increases the likelihood of a child being later diagnosed with ASD. Particulate matter (PM), via air pollution, is an environmental factor known to worsen the symptoms of asthma, but also, PM has been associated with increased risk of neuropsychiatric disorders including ASD. Despite the links between asthma and PM with neuropsychiatric disorders, there is a lack of laboratory models investigating combined prenatal exposure to asthma and PM on offspring neurodevelopment. Thus, we developed a novel mouse model that combines exposure to maternal allergic asthma (MAA) and ultrafine iron-soot (UIS), a common component of PM. In the current study, female BALB/c mice were primed for allergic asthma with ovalbumin (OVA) prior to pregnancy. Following mating and beginning on gestational day 2 (GD2), dams were exposed to either aerosolized OVA or phosphate buffered saline (PBS) for 1 hour. Following the 1-hour exposure, pregnant females were then exposed to UIS or clean air for 4 hours. Offspring brains were collected at postnatal days (P)15 and (P)35. Cortices and hippocampal regions were then isolated and assessed for changes in cytokines using a Luminex bead-based multiplex assay. Analyses identified changes in many cytokines across treatment groups at both timepoints in the cortex, including interleukin-1 beta (IL-1β), IL-2, IL-13, and IL-17, which remained elevated from P15 to P35 in all treatment conditions compared to controls. In the hippocampus at P15, elevations in cytokines were also identified across the treatment groups, namely interferon gamma (IFNγ) and IL-7. The combination of MAA and UIS exposure (MAA-UIS) during pregnancy resulted in an increase in microglia density in the hippocampus of offspring, as identified by IBA-1 staining. Together, these data indicate that exposure to MAA, UIS, and MAA-UIS result in changes in the neuroimmune environment of offspring that persist into adulthood.

Long-term effects of ambient PM2.5 constituents on metabolic syndrome in Chinese children and adolescents

Metabolic syndrome (MetS) is considered a main public health issue as it remarkably adds the risk of cardiovascular disease, leading to a heavy burden of disease. There is growing evidence linking fine particulate matter (PM_2.5) exposure to MetS. However, the influences of PM_2.5 constituents, especially in children and adolescents, remain unclear. Our study was according to a national analysis among Chinese children and adolescents to examine the associations between long-term exposure to PM_2.5 main constituents and MetS. A total of 10,066 children and adolescents aged 10-18 years were recruited in 7 provinces in China, with blood tests, health exams, and questionnaire surveys. We estimated long-term exposures to PM_2.5 mass and its five constituents, containing black carbon (BC), organic matter (OM), inorganic nitrate (NO₃^-), sulfate (SO₄^2-), and soil particles (SOIL) from multi-source data fusion models. Mixed-effects logistic regression models were used with the adjustment of a variety of covariates. In the surveyed populations, 2.9% were classified as MetS. From the single-pollutant models, we discovered that long-term exposures to PM_2.5 mass, BC, OM, NO₃^-, as well as SO₄^2-, were significantly associated with the prevalence of MetS, with odds ratios (ORs) per 1 μg/m³ that were 1.02 (95% confidence interval (CI): 1.01, 1.03) for PM_2.5 mass, 1.24 (95% CI: 1.14, 1.35) for BC, 1.07 (95% CI: 1.04, 1.11) for OM, 1.09 (95% CI: 1.04, 1.13) for NO₃^-, and 1.14 (95% CI:1.04, 1.24) for SO₄^2-. The influence of BC on the prevalence of MetS was robust in both the multi-pollutant model and the PM_2.5-constituent joint model. The paper indicates long-term exposure to PM_2.5 mass and specific PM_2.5 constituents, particularly for BC, was significantly associated with a higher MetS prevalence among children and adolescents in China. Our results highlight the significance of establishing further regulations on PM_2.5 constituents.

Association of long-term exposure to PM2.5 constituents with glucose metabolism in Chinese rural population

BACKGROUND

Evidence on the associations of fine particulate matter (PM_2.5) constituents and glucose metabolism is limited in resource-limited areas. This study aimed to explore the associations of PM_2.5 constituents with glucose metabolism in rural areas, and to further specify the most responsible constituent.

METHODS

A total of 38,442 adults were recruited from the Henan Rural Cohort Study during 2015-2017. Three-year averaged concentrations of PM_2.5 mass and its constituents (black carbon (BC), ammonium (NH₄⁺), nitrate (NO₃^-), organic matter (OM), inorganic sulfate (SO₄^2-), soil particles (SOIL) and sea salt (SS)) were estimated by a hybrid satellite-based model. Generalized linear model was applied to explore the associations of PM_2.5 mass and its constituents with type 2 diabetes mellitus (T2DM), fasting blood glucose (FBG), insulin, and HOMA-β. Proportion and residual analyses were employed to specify the most responsible constituent.

RESULTS

The adjusted odds ratio (OR) for T2DM associated with 1 μg/m³ increase was 1.02 for PM_2.5 mass, 1.28 for BC, 1.15 for NH₄⁺, 1.08 for NO₃^-, 1.10 for OM, 1.11 for SO₄^2-, and 1.12 for SOIL. Significant associations of PM_2.5 mass and its constituents with elevated FBG, decreased insulin and HOMA-β were also observed. Proportion and residual analyses indicated that BC was the most responsible constituent, in which 1 percentage increment in the proportion of BC in PM_2.5 corresponded with 1.51-fold risk for T2DM, 0.17 mmol/L increase in FBG, 2.18 μU/mL decrease in insulin, and 38.26 % decrease in HOMA-β; and 1 μg/m³ increment in the PM_2.5-adjusted BC corresponded with 1.59-fold risk for T2DM, 0.53 mmol/L increase in FBG, 4.79 μU/mL decrease in insulin, and 91.32 % decrease in HOMA-β.

CONCLUSIONS

PM_2.5 mass and its constituents (BC, NH₄⁺, NO₃^-, OM, SO₄^2-, SOIL) were associated with T2DM, increased FBG, decreased insulin and HOMA-β, of which BC was most responsible for these associations.

TRIAL REGISTRATION

The Henan Rural Cohort Study has been registered at Chinese Clinical Trial Register (Registration number: ChiCTR-OOC-15006699). Date of registration: 06 July 2015. http://www.chictr.org.cn/showproj.aspx?proj=11375.

Associations of Autism Spectrum Disorder with PM2.5 Components: A Comparative Study Using Two Different Exposure Models

This retrospective cohort study examined associations of autism spectrum disorder (ASD) with prenatal exposure to major fine particulate matter (PM2.5) components estimated using two independent exposure models. The cohort included 318 750 mother-child pairs with singleton deliveries in Kaiser Permanente Southern California hospitals from 2001 to 2014 and followed until age five. ASD cases during follow-up (N = 4559) were identified by ICD codes. Prenatal exposures to PM2.5, elemental (EC) and black carbon (BC), organic matter (OM), nitrate (NO3-), and sulfate (SO42-) were constructed using (i) a source-oriented chemical transport model and (ii) a hybrid model. Exposures were assigned to each maternal address during the entire pregnancy, first, second, and third trimester. In single-pollutant models, ASD was associated with pregnancy-average PM2.5, EC/BC, OM, and SO42- exposures from both exposure models, after adjustment for covariates. The direction of effect estimates was consistent for EC/BC and OM and least consistent for NO3-. EC/BC, OM, and SO42- were generally robust to adjustment for other components and for PM2.5. EC/BC and OM effect estimates were generally larger and more consistent in the first and second trimester and SO42- in the third trimester. Future PM2.5 composition health effect studies might consider using multiple exposure models and a weight of evidence approach when interpreting effect estimates.

Incident dementia and long-term exposure to constituents of fine particle air pollution: A national cohort study in the United States

Growing evidence suggests that fine particulate matter (PM2.5) likely increases the risks of dementia, yet little is known about the relative contributions of different constituents. Here, we conducted a nationwide population-based cohort study (2000 to 2017) by integrating the Medicare Chronic Conditions Warehouse database and two independently sourced datasets of high-resolution PM2.5 major chemical composition, including black carbon (BC), organic matter (OM), nitrate (NO3-), sulfate (SO42-), ammonium (NH4+), and soil dust (DUST). To investigate the impact of long-term exposure to PM2.5 constituents on incident all-cause dementia and Alzheimer's disease (AD), hazard ratios for dementia and AD were estimated using Cox proportional hazards models, and penalized splines were used to evaluate potential nonlinear concentration-response (C-R) relationships. Results using two exposure datasets consistently indicated higher rates of incident dementia and AD for an increased exposure to PM2.5 and its major constituents. An interquartile range increase in PM2.5 mass was associated with a 6 to 7% increase in dementia incidence and a 9% increase in AD incidence. For different PM2.5 constituents, associations remained significant for BC, OM, SO42-, and NH4+ for both end points (even after adjustments of other constituents), among which BC and SO42- showed the strongest associations. All constituents had largely linear C-R relationships in the low exposure range, but most tailed off at higher exposure concentrations. Our findings suggest that long-term exposure to PM2.5 is significantly associated with higher rates of incident dementia and AD and that SO42-, BC, and OM related to traffic and fossil fuel combustion might drive the observed associations.

Prenatal exposure to tailpipe and non-tailpipe tracers of particulate matter pollution and autism spectrum disorders

BACKGROUND

Traffic-related air pollution exposure is associated with increased risk of autism spectrum disorder (ASD). It is unknown whether carbonaceous material from vehicular tailpipe emissions or redox-active non-tailpipe metals, eg. from tire and brake wear, are responsible. We assessed ASD associations with fine particulate matter (PM_2.5) tracers of tailpipe (elemental carbon [EC] and organic carbon [OC]) and non-tailpipe (copper [Cu]; iron [Fe] and manganese [Mn]) sources during pregnancy in a large cohort.

METHODS

This retrospective cohort study included 318,750 children born in Kaiser Permanente Southern California (KPSC) hospitals during 2001-2014, followed until age 5. ASD cases were identified by ICD codes. Monthly estimates of PM_2.5 and PM_2.5 constituents EC, OC, Cu, Fe, and Mn with 4 km spatial resolution were obtained from a source-oriented chemical transport model. These exposures and NO₂ were assigned to each maternal address during pregnancy, and associations with ASD were assessed using Cox regression models adjusted for covariates. PM constituent effect estimates were adjusted for PM_2.5 and NO₂ to assess independent effects. To distinguish ASD risk associated with non-tailpipe from tailpipe sources, the associations with Cu, Fe, and Mn were adjusted for EC and OC, and vice versa.

RESULTS

There were 4559 children diagnosed with ASD. In single-pollutant models, increased ASD risk was associated with gestational exposures to tracers of both tailpipe and non-tailpipe emissions. The ASD hazard ratios (HRs) per inter-quartile increment of exposure) for EC, OC, Cu, Fe, and Mn were 1.11 (95% CI: 1.06-1.16), 1.09 (95% CI: 1.04-1.15), 1.09 (95% CI: 1.04-1.13), 1.14 (95% CI: 1.09-1.20), and 1.17 (95% CI: 1.12-1.22), respectively. Estimated effects of Cu, Fe, and Mn (reflecting non-tailpipe sources) were largely unchanged in two-pollutant models adjusting for PM_2.5, NO₂, EC or OC. In contrast, ASD associations with EC and OC were markedly attenuated by adjustment for non-tailpipe sources.

CONCLUSION

Results suggest that non-tailpipe emissions may contribute to ASD. Implications are that reducing tailpipe emissions, especially from vehicles with internal combustion engines, may not eliminate ASD associations with traffic-related air pollution.

Neonatal exposure to ultrafine iron but not combined iron and sulfur aerosols recapitulates air pollution-induced impulsivity in mice

Air pollution (AP) is becoming recognized as a major threat to neurological health across the lifespan with increased risk of both neurodevelopmental and neurodegenerative disorders. AP is a complex mixture of gases and particulate matter, with adsorbed contaminants including metals and trace elements, which may differentially contribute to its neurodevelopmental impacts. Iron (Fe) is one of the most abundant metals found in AP, and Fe concentrations may drive some behavioral deficits observed in children. Furthermore, brains of neonate mice exposed to concentrated ambient ultrafine particulate matter (UFP) show significant brain accumulation of Fe and sulfur (S) supporting the hypothesis that AP exposure may lead to brain metal dyshomeostasis. The current study determined the extent to which behavioral effects of UFP, namely memory deficits and impulsive-like behavior, could be recapitulated with exposure to Fe aerosols with or without concomitant SO2. Male and female neonate mice were either exposed to filtered air or spark discharge-generated ultrafine Fe particles with or without SO2 gas (n = 12/exposure/sex). Inhalation exposures occurred from postnatal day (PND) 4-7 and 10-13 for 4 hr/day, mirroring our previous UFP exposures. Mice were aged to adulthood prior to behavioral testing. While Fe or Fe + SO2 exposure did not affect gross locomotor behavior, Fe + SO2-exposed females displayed consistent thigmotaxis during locomotor testing. Neither exposure affected novel object memory. Fe or Fe + SO2 exposure produced differential outcomes on a fixed-interval reinforcement schedule with males showing higher (Fe-only) or lower (Fe + SO2) response rates and postreinforcement pauses (PRP) and females showing higher (Fe-only) PRP. Lastly, Fe-exposed, but not Fe + SO2-exposed, males showed increased impulsive-like behavior in tasks requiring response inhibition with no such effects in female mice. These findings suggest that: 1) exposure to realistic concentrations of Fe aerosols can recapitulate behavioral effects of UFP exposure, 2) the presence of SO2 can modulate behavioral effects of Fe inhalation, and 3) brain metal dyshomeostasis may be an important factor in AP neurotoxicity.

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.

Association of PM2.5 and Its Chemical Compositions with Metabolic Syndrome: A Nationwide Study in Middle-Aged and Older Chinese Adults

Studies on the association of PM_2.5 and its compositions with metabolic syndrome (MetS) were limited, and it was unclear which was the most hazardous composition. In this study, we aimed to investigate the association between PM_2.5 and its compositions with MetS and identified the most hazardous composition. In this study, we included 13,418 adults over 45 years across 446 communities from 150 counties of 28 provinces in nationwide China in 2015. MetS was defined based on the five indicators of the Joint Interim Societies, including: blood pressure (SBP (systolic blood pressure) and DBP (diastolic blood pressure)); fasting blood glucose (FBG); fasting triglyceride (FTG); high density lipoprotein cholesterol (HDL-C); and waist circumference (WC). We used chemical transport models to estimate the concentration of PM_2.5 and its compositions, including black carbon, ammonium, nitrate, organic matter, and sulfate. We used a generalized linear regression model to examine the association of PM_2.5 and its compositions with MetS. In this study, we observed that the average age was 61.40 (standard deviation (SD): 9.59). Each IQR (29.76 μg/m³) increase in PM_2.5 was associated with a 1.27 (95% CI: 1.17, 1.37) increase in the odds for MetS. We indicated that black carbon showed stronger associations than other compositions. The higher associations were observed among women, participants aged less than 60 years, who lived in urban areas and in the Northeast, smokers, drinkers, and the obese populations. In conclusion, our findings identified the most harmful composition and sensitive populations and regions that required attention, which would be helpful for policymakers.

A perspective on persistent toxicants in veterans and amyotrophic lateral sclerosis: identifying exposures determining higher ALS risk

Multiple studies indicate that United States veterans have an increased risk of developing amyotrophic lateral sclerosis (ALS) compared to civilians. However, the responsible etiological factors are unknown. In the general population, specific occupational (e.g. truck drivers, airline pilots) and environmental exposures (e.g. metals, pesticides) are associated with an increased ALS risk. As such, the increased prevalence of ALS in veterans strongly suggests that there are exposures experienced by military personnel that are disproportionate to civilians. During service, veterans may encounter numerous neurotoxic exposures (e.g. burn pits, engine exhaust, firing ranges). So far, however, there is a paucity of studies investigating environmental factors contributing to ALS in veterans and even fewer assessing their exposure using biomarkers. Herein, we discuss ALS pathogenesis in relation to a series of persistent neurotoxicants (often emitted as mixtures) including: chemical elements, nanoparticles and lipophilic toxicants such as dioxins, polycyclic aromatic hydrocarbons and polychlorinated biphenyls. We propose these toxicants should be directly measured in veteran central nervous system tissue, where they may have accumulated for decades. Specific toxicants (or mixtures thereof) may accelerate ALS development following a multistep hypothesis or act synergistically with other service-linked exposures (e.g. head trauma/concussions). Such possibilities could explain the lower age of onset observed in veterans compared to civilians. Identifying high-risk exposures within vulnerable populations is key to understanding ALS etiopathogenesis and is urgently needed to act upon modifiable risk factors for military personnel who deserve enhanced protection during their years of service, not only for their short-term, but also long-term health.

Developing a Solution for Nasal and Olfactory Transport of Nanomaterials

With advances in nanotechnology, engineered nanomaterial applications are a rapidly growing sector of the economy. Some nanomaterials can reach the brain through nose-to-brain transport. This transport creates concern for potential neurotoxicity of insoluble nanomaterials and a need for toxicity screening tests that detect nose-to-brain transport. Such tests can involve intranasal instillation of aqueous suspensions of nanomaterials in dispersion media that limit particle agglomeration. Unfortunately, protein and some elements in existing dispersion media are suboptimal for potential nose-to-brain transport of nanomaterials because olfactory transport has size- and ion-composition requirements. Therefore, we designed a protein-free dispersion media containing phospholipids and amino acids in an isotonic balanced electrolyte solution, a solution for nasal and olfactory transport (SNOT). SNOT disperses hexagonal boron nitride nanomaterials with a peak particle diameter below 100 nm. In addition, multiwalled carbon nanotubes (MWCNTs) in an established dispersion medium, when diluted with SNOT, maintain dispersion with reduced albumin concentration. Using stereomicroscopy and microscopic examination of plastic sections, dextran dyes dispersed in SNOT are demonstrated in the neuroepithelium of the nose and olfactory bulb of B6;129P2-Omp^tm3Mom/MomJ mice after intranasal instillation in SNOT. These findings support the potential for SNOT to disperse nanomaterials in a manner permitting nose-to-brain transport for neurotoxicity studies.

Human exposure to metals in consumer-focused fused filament fabrication (FFF)/ 3D printing processes

Fused filament fabrication (FFF) or 3D printing is a growing technology used in industry, cottage industry and for consumer applications. Low-cost 3D printing devices have become increasingly popular among children and teens. Consequently, 3D printers are increasingly common in households, schools, and libraries. Because the operation of 3D printers is associated with the release of inhalable particles and volatile organic compounds (VOCs), there are concerns of possible health implications, particularly for use in schools and residential environments that may not have adequate ventilation such as classrooms bedrooms and garages, etc. Along with the growing consumer market for low-cost printers and printer pens, there is also an expanding market for a range of specialty filaments with additives such as inorganic colorants, metal particles and nanomaterials as well as metal-containing flame retardants, antioxidants, heat stabilizers and catalysts. Inhalation of particulate-associated metals may represent a health risk depending on both the metal and internal dose to the respiratory tract. Little has been reported, however, about the presence, speciation, and source of metals in the emissions; or likewise the effect of metals on emission processes and toxicological implications of these 3D printer generated emissions. This report evaluates various issues including the following: metals in feedstock with a focus on filament characteristics and function of metals; the effect of metals on the emissions and metals detected in emissions; printer emissions, particle formation, transport, and transformation; exposure and translation to internal dose; and potential toxicity on inhaled dose. Finally, data gaps and potential areas of future research are discussed within these contexts.

Ultrafine black carbon caused mitochondrial oxidative stress, mitochondrial dysfunction and mitophagy in SH-SY5Y cells

Exposure to ambient ultrafine black carbon (uBC, with aerodynamic diameter less than 100 nm) is associated with many neurodegenerative diseases. Oxidative stress is the predominantly reported neurotoxic effects caused by uBC exposure. Mitochondrion is responsible for production of majority of ROS in cells and mitochondrial dysfunction is closely related to adverse nervous outcomes. Mitophagy is an important cellular process to eliminate dysfunctional or damaged mitochondria. However, the mechanisms that modulate mitophagy and mitochondrial dysfunction initiated by uBC remain to be elucidated. The purpose of this study was to investigate how mitochondrial oxidative stress regulated mitochondrial dysfunction and mitophagy in human neuroblastoma cell line (SH-SY5Y) after uBC treatment. RNA interference was further applied to explore the roles of mitophagy in mitochondrial dysfunction. We found uBC triggered cell apoptosis via ROS-mitochondrial apoptotic pathway. The uBC also caused serious mitochondrial damage and respiratory dysfunction, indicated by the abnormalities in mitochondrial division and fusion related proteins, decreased mitochondria number and ATP level. Increased PTEN induced putative kinase 1 (PINK1) and Parkin protein levels and the autolysosome numbers suggested uBC could promote Pink1/Parkin-dependent mitophagy process in SH-SY5Y cells. Mitophagy inhibition could reserve mitochondria number and ATP activity, but not fusion and division related protein levels in SH-SY5Y cells exposed to uBC. Administration of a mitochondria-targeted antioxidant (mitoquinone) significantly eliminated uBC caused apoptosis, mitochondrial dysfunction and mitophagy. Our data suggested mitochondrial oxidative stress regulated uBC induced mitochondrial dysfunction and PINK1/Parkin-dependent mitophagy. PINK1/Parkin-dependent mitophagy probably participated in regulating uBC caused mitochondrial dysfunction but not by controlling mitochondrial fusion and division related proteins. Our results may provide some new insights and evidences to understand the mechanisms of neurotoxicity induced by uBC.

Direct nose to the brain nanomedicine delivery presents a formidable challenge

This advanced review describes the anatomical and physiological barriers and mechanisms impacting nanomedicine translocation from the nasal cavity directly to the brain. There are significant physiological and anatomical differences in the nasal cavity, olfactory area, and airflow reaching the olfactory epithelium between humans and experimentally studied species that should be considered when extrapolating experimental results to humans. Mucus, transporters, and tight junction proteins present barriers to material translocation across the olfactory epithelium. Uptake of nanoparticles through the olfactory mucosa and translocation to the brain can be intracellular via cranial nerves (intraneuronal) or other cells of the olfactory epithelium, or extracellular along cranial nerve pathways (perineural) and surrounding blood vessels (perivascular, the glymphatic system). Transport rates vary greatly among the nose to brain pathways. Nanomedicine physicochemical properties (size, surface charge, surface coating, and particle stability) can affect uptake efficiency, which is usually less than 5%. Incorporation of therapeutic agents in nanoparticles has been shown to produce pharmacokinetic and pharmacodynamic benefits. Assessment of adverse effects has included olfactory mucosa toxicity, ciliotoxicity, and olfactory bulb and brain neurotoxicity. The results have generally suggested the investigated nanomedicines do not present significant toxicity. Research needs to advance the understanding of nanomedicine translocation and its drug cargo after intranasal administration is presented. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Long-term effects of PM2.5 components on blood pressure and hypertension in Chinese children and adolescents

Growing evidence has linked fine particulate matter (PM_2.5) exposure to elevated blood pressure, but the effects of PM_2.5 components are unclear, particularly in children and adolescents. Based on a cross-sectional investigation in China, we analyzed the associations between long-term exposure to PM_2.5 and its major components with elevated blood pressure in children and adolescents. A representative sample (N = 37,610) of children and adolescents with age 7-18 years was collected in seven Chinese provinces. Exposures to PM_2.5 and five of its major components, including black carbon (BC), organic matter (OM), inorganic nitrate (NO₃^-), sulfate (SO₄^2-), and soil particles (SOIL), were estimated using satellite-based spatiotemporal models. The associations between long-term exposures to PM_2.5 and its components and diastolic blood pressure (DBP), systolic blood pressure (SBP), and hypertension were investigated using mixed-effects logistic and linear regression models. Within the populations, 11.5 % were classified as hypertension. After adjusting for a variety of covariates, per interquartile range (IQR) increment in PM_2.5 mass and BC levels were significantly associated with a higher hypertension prevalence with odds ratios (ORs) of 1.56 (95% confidence interval (CI): 1.08, 2.25) for PM_2.5 and 1.19 (95% CI: 1.04, 1.35) for BC. Long-term exposures to PM_2.5 and BC have also been associated with elevated SBP and DBP. Additionally, OM and NO₃^- were significantly associated with increased SBP, while SOIL was significantly associated with increased DBP. In the subgroup analysis, the associations between long-term exposures to BC and blood pressure vary significantly by urbanicity of residential area and diet habits. Our study suggests that long-term exposure to PM_2.5 mass and specific PM_2.5 components, especially for BC, are significantly associated with elevated blood pressure and a higher hypertension prevalence in Chinese children and adolescents.

Association between indoor air pollution and cognitive function among nationally representative sample of middle-aged and older adults in India-A multilevel modelling approach

We have used a nationally representative sample of middle-aged and older adults in India to study the association between indoor air pollution and cognitive function. Longitudinal aging study in India (LASI) Wave-I data was utilized for this study. A two-level mixed-effects linear regression model was used to study the association between indoor air pollution and cognitive function and interpreted as adjusted beta coefficient (ꞵ) with 95% confidence interval (CI). In total, 56,179 participants aged ≥45 years were included in the analysis. The proportion of participants living in households with indoor air pollution were 30.6% (95%CI: 30.0%-31.3%). After adjusting for all the potential confounders (age, gender, education, region, religion, separate kitchen, socioeconomic status, marital status, residence, smoking, alcohol consumption, body mass index, self-rated health, and sleep problems), participants living in households with indoor air pollution had significant decline in the cognitive function when compared to those living in households without indoor air pollution (ꞵ = -0.57; 95%CI: -0.69 to -0.45). Since the LASI survey is being conducted as a biennial panel survey, assessing the impact of indoor air pollution on cognitive decline using the follow-up data can provide further insights into the pathogenesis of condition.

Brain accumulation of inhaled uranium in the rat depends on aerosol concentration, exposure repetitions, particle size and solubility

A rostro-caudal gradient of uranium (U) in the brain has been suggested after its inhalation. To study the factors influencing this mapping, we first used 30-min acute inhalation at 56 mg/m³ of the relatively soluble form UO₄ in the rat. These exposure parameters were then used as a reference in comparison with the other experimental conditions. Other groups received acute inhalation at different concentrations, repeated low dose inhalation of UO₄ (10 exposures) or acute low dose inhalation of the insoluble form UO₂. At 24 h after the last exposure, all rats showed a brain U accumulation with a rostro-caudal gradient as compared to controls. However, the total concentration to the brain was greater after repeated exposure than acute exposure, demonstrating an accumulative effect. In comparison with the low dose soluble U exposure, a higher accumulation in the front of the brain was observed after exposure to higher dose, to insoluble particles and following repetition of exposures, thus demonstrating a dose effect and influences of solubility and repetition of exposures. In the last part, exposure to ultrafine U particles made it possible to show 24 h after exposure the presence of U in the brain according to a rostro-caudal gradient. Finally, the time-course after exposure to micronic or nanometric U particles has revealed greater residence times for nanoparticles.

Elucidating long-term trends, seasonal variability, and local impacts from thirteen years of near-road particle size data (2006-2019)

Significant attention, especially in the last decade, has been focussed on elevated concentrations of ultrafine particulate matter (UFP) in urban areas and the adverse health effects associated with exposure to UFP. Despite this, there is a relative scarcity of long-term ambient UFP measurements. This study examined trends in UFP measurements made continuously near a busy roadway in downtown Toronto, Canada, between the years 2006 and 2019 using a fast mobility particle sizer (FMPS). These long-term trends were associated with other air pollutant concentrations-namely: nitric oxide (NO), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), and fine particulate matter mass concentrations (PM_2.5)-and persistent declining trends were observed for each during the study period. From 2006 to 2019, reductions of 45%, 68%, 39%, 83%, and 41%, for UFP, NO, NO₂, SO₂, and PM_2.5, respectively, were observed. These reductions are in part associated with a total phase-out of coal-fired electricity generation in Ontario, Canada, between 2004 and 2015, and continuous improvements in vehicle emissions control technologies. Additionally, deconvolution of the time-series yielded seasonal fluctuations which were analysed as a function of particle diameter and ambient temperature, the results from which may aid in the comparison of UFP measurements made in climates with different ambient temperature ranges in a meaningful way. Finally, the UFP data were background-subtracted and it was found that local sources (such as vehicle traffic) contributed ~45% to total concentrations and this fraction remained relatively constant throughout the study. A multilinear function regressed on these local and background concentrations better elucidated the sources contributing to UFP variability-background concentrations were largely covariate with SO₂ emissions whereas local concentrations were more affected by NO emissions. The data in this study shows clear co-benefits to reducing UFP concentrations by targeting NO_x and SO_x emissions.

Air Pollution Neurotoxicity in the Adult Brain: Emerging Concepts from Experimental Findings

Epidemiological studies are associating elevated exposure to air pollution with increased risk of Alzheimer's disease and other neurodegenerative disorders. In effect, air pollution accelerates many aging conditions that promote cognitive declines of aging. The underlying mechanisms and scale of effects remain largely unknown due to its chemical and physical complexity. Moreover, individual responses to air pollution are shaped by an intricate interface of pollutant mixture with the biological features of the exposed individual such as age, sex, genetic background, underlying diseases, and nutrition, but also other environmental factors including exposure to cigarette smoke. Resolving this complex manifold requires more detailed environmental and lifestyle data on diverse populations, and a systematic experimental approach. Our review aims to summarize the modest existing literature on experimental studies on air pollution neurotoxicity for adult rodents and identify key gaps and emerging challenges as we go forward. It is timely for experimental biologists to critically understand prior findings and develop innovative approaches to this urgent global problem. We hope to increase recognition of the importance of air pollution on brain aging by our colleagues in the neurosciences and in biomedical gerontology, and to support the immediate translation of the findings into public health guidelines for the regulation of remedial environmental factors that accelerate aging processes.

Effects of Iron Oxide Nanoparticles on Structural Organization of Hepatocyte Chromatin: Gray Level Co-occurrence Matrix Analysis

Gray level co-occurrence matrix (GLCM) analysis is a contemporary and innovative computer-based algorithm that can be used for the quantification of subtle changes in a cellular structure. In this work, we use this method for the detection of discrete alterations in hepatocyte chromatin distribution after in vivo exposure to iron oxide nanoparticles (IONPs). The study was performed on 40 male, healthy C57BL/6 mice divided into four groups: three experimental groups that received different doses of IONPs and 1 control group. We describe the dose-dependent reduction of chromatin textural uniformity measured as GLCM angular second moment. Similar changes were detected for chromatin textural uniformity expressed as the value of inverse difference moment. To the best of our knowledge, this is the first study to investigate the impact of iron-based nanomaterials on hepatocyte GLCM parameters. Also, this is the first study to apply discrete wavelet transform analysis, as a supplementary method to GLCM, for the assessment of hepatocyte chromatin structure in these conditions. The results may present the useful basis for future research on the application of GLCM and DWT methods in pathology and other medical research areas.

Environmentally Relevant Iron Oxide Nanoparticles Produce Limited Acute Pulmonary Effects in Rats at Realistic Exposure Levels

Iron is typically the dominant metal in the ultrafine fraction of airborne particulate matter. Various studies have investigated the toxicity of inhaled nano-sized iron oxide particles (FeO_xNPs) but their results have been contradictory, with some indicating no or minor effects and others finding effects including oxidative stress and inflammation. Most studies, however, did not use materials reflecting the characteristics of FeO_xNPs present in the environment. We, therefore, analysed the potential toxicity of FeO_xNPs of different forms (Fe₃O₄, α-Fe₂O₃ and γ-Fe₂O₃) reflecting the characteristics of high iron content nano-sized particles sampled from the environment, both individually and in a mixture (FeO_x-mix). A preliminary in vitro study indicated Fe₃O₄ and FeO_x-mix were more cytotoxic than either form of Fe₂O₃ in human bronchial epithelial cells (BEAS-2B). Follow-up in vitro (0.003, 0.03, 0.3 µg/mL, 24 h) and in vivo (Sprague–Dawley rats, nose-only exposure, 50 µg/m³ and 500 µg/m³, 3 h/d × 3 d) studies therefore focused on these materials. Experiments in vitro explored responses at the molecular level via multi-omics analyses at concentrations below those at which significant cytotoxicity was evident to avoid detection of responses secondary to toxicity. Inhalation experiments used aerosol concentrations chosen to produce similar levels of particle deposition on the airway surface as were delivered in vitro. These were markedly higher than environmental concentrations. No clinical signs of toxicity were seen nor effects on BALF cell counts or LDH levels. There were also no significant changes in transcriptomic or metabolomic responses in lung or BEAS-2B cells to suggest adverse effects.

Uptake and Transport of Ultrafine Nanoparticles (Quantum Dots) in the Nasal Mucosa

A wide variety of colloidal delivery systems, including polymeric nanoparticles, metal colloids, liposomes, and microemulsions have been reported to enhance the delivery of therapeutic agents across the nasal mucosa. The mechanisms involved in the uptake of these nanomaterials, especially ultrafine nanomaterials (diameters < 20 nm) through the nasal mucosa are not well understood. Fluorescent quantum dots (QDs) were used to investigate the uptake of ultrafine nanoparticles by bovine respiratory and olfactory mucosal tissues following in vitro exposure, and an inductively coupled plasma optical emission spectroscopy method was developed to quantify the amount of QDs localized within the tissues. QDs do not biodegrade or release their core materials and, as a result, this method allowed for the direct quantification of the nanoparticles themselves, rather than the measurement of a potentially dissociated drug or label. The results demonstrated that carboxylate-modified QDs (COOH-QDs) showed ∼2.5-fold greater accumulation in the epithelial and submucosal regions of olfactory tissues compared to that in respiratory tissues. Endocytic inhibitory studies showed that clathrin-dependent endocytosis, macropinocytosis, and caveolae-dependent endocytic process are all involved in the uptake of COOH-QDs into the respiratory tissues. In olfactory tissues, clathrin-dependent endocytosis is the major endocytic pathway involved in the uptake of COOH-QDs. Additional energy-independent pathways also appeared to allow the transfer of COOH-QDs within the olfactory mucosa. When polyethylene glycol-modified QDs known as PEGylated QDs (PEG-QDs) of similar size, ∼15 nm, were investigated, no nanoparticles were detected in the tissues suggesting that the PEG corona limits the interactions with endocytic and other uptake processes in the nasal epithelium. The capacity for nanoparticle uptake observed in the nasal mucosa, along with the ability of significant numbers of nanoparticles to enter the olfactory tissues using nonenergy-dependent pathways show that the pathways for ultrafine nanoparticle uptake in the nasal tissues have both drug delivery and toxicologic consequences. This places an increased importance on the careful selection of nanoparticle components and drugs intended for intranasal administration.

Occupational exposure to unintentionally emitted nanoscale particles and risk of cancer: From lung to central nervous system - Results from three French case-control studies

OBJECTIVES

Nanoscale particles (1-100 nm) can be of natural origin, and either intentionally or unintentionally produced by human activities. Toxicological data have suggested a possible carcinogenic effect of such particles. The aim of this study was to estimate the association between occupational exposure to nanoscale particles and risk of lung cancer, pleural mesothelioma and brain tumors in adults.

METHODS

Three French population-based case-control studies were analyzed: 1) the ICARE study including 2029 lung cancer cases and 2591 controls; 2) the PNSM study including 371 pleural mesothelioma cases and 730 controls and 3) the CERENAT study including 257 brain tumor cases and 511 controls. Occupational exposure to unintentionally emitted nanoscale particles (UNPs) was retrospectively assessed by a job exposure matrix providing a probability and a frequency of exposure.

RESULTS

In adjusted analyses among men, significant associations between occupational exposure to UNPs and lung cancer (OR = 1.51; 95% CI: 1.22-1.86 and brain tumors (OR = 1.69; 95% CI: 1.17-2.44) were observed. No increased OR was observed for pleural mesothelioma (OR = 0.78; 95% CI: 0.46-1.33).

CONCLUSION

This is the first study showing positive associations between occupational exposure to UNPs and increased risk of lung cancer and brain tumors. These preliminary results should encourage further epidemiological research.

Research on Teaching a Welding Implementation Course Assisted by Sustainable Virtual Reality Technology

The purpose of this study is to explore the application of VR (virtual reality) technology to assist the development of VR welding courses in welding practice teaching, and to implement experimental teaching to verify its effectiveness. The preliminary VR welding curriculum structure was developed by this study according to the results of literature review and focus group interviews, the student-based “VR welding course” was developed, and 34 first-year students of the electric welding practice course were taken as the research subjects to implement experimental teaching and case study. The qualitative and quantitative research and analysis results are as follows. (1) The results of the final test of the welding practice of most students are significantly higher than the results of the mid-term test. (2) Most students expressed significant positive affirmation of the learning effect of the VR-assisted welding course. (3) Most students were very significantly positive regarding their learning satisfaction with the VR-assisted welding teaching course. (4) The four major implementation priorities of VR welding courses were planned. This study develops a “teaching mode of a welding implementation course assisted by virtual reality technology”, which can provide students with a safe, low-cost, repeatable, and sustainable welding skills learning environment, and has been positively affirmed by most students. In the future, the results of this study can provide reference for the introduction of virtual-reality-assisted teaching of welding related courses in various universities of science and technology, in order to strengthen teachers’ teaching ability in VR assisted implementation courses and provide students with more diversified learning stimuli.

Air Pollution-Related Brain Metal Dyshomeostasis as a Potential Risk Factor for Neurodevelopmental Disorders and Neurodegenerative Diseases

Increasing evidence links air pollution (AP) exposure to effects on the central nervous system structure and function. Particulate matter AP, especially the ultrafine (nanoparticle) components, can carry numerous metal and trace element contaminants that can reach the brain in utero and after birth. Excess brain exposure to either essential or non-essential elements can result in brain dyshomeostasis, which has been implicated in both neurodevelopmental disorders (NDDs; autism spectrum disorder, schizophrenia, and attention deficit hyperactivity disorder) and neurodegenerative diseases (NDGDs; Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and amyotrophic lateral sclerosis). This review summarizes the current understanding of the extent to which the inhalational or intranasal instillation of metals reproduces in vivo the shared features of NDDs and NDGDs, including enlarged lateral ventricles, alterations in myelination, glutamatergic dysfunction, neuronal cell death, inflammation, microglial activation, oxidative stress, mitochondrial dysfunction, altered social behaviors, cognitive dysfunction, and impulsivity. Although evidence is limited to date, neuronal cell death, oxidative stress, and mitochondrial dysfunction are reproduced by numerous metals. Understanding the specific contribution of metals/trace elements to this neurotoxicity can guide the development of more realistic animal exposure models of human AP exposure and consequently lead to a more meaningful approach to mechanistic studies, potential intervention strategies, and regulatory requirements.

Influence of Woodsmoke Exposure on Molecular Mechanisms Underlying Alzheimer's Disease: Existing Literature and Gaps in Our Understanding

Woodsmoke poses a significant health risk as a growing component of ambient air pollution in the United States. While there is a long history of association between woodsmoke exposure and diseases of the respiratory, circulatory, and cardiovascular systems, recent evidence has linked woodsmoke exposure to cognitive dysfunction, including Alzheimer’s disease dementia. Alzheimer’s disease is a progressive neurodegenerative disorder with largely idiopathic origins and no known cure. Here, we explore the growing body of literature which relates woodsmoke-generated and ambient air pollution particulate matter exposure to Alzheimer’s disease (AD) onset or exacerbation, in the context of an inflammation-centric view of AD. Epigenetic modifications, specifically changes in DNA methylation patterns, are well documented following woodsmoke exposure and have been shown to influence disease-favoring inflammatory cascades, induce oxidative stress, and modulate the immune response in vitro, in vivo, and in humans following exposure to air pollution. Though the current status of the literature does not allow us to draw definitive conclusions linking these events, this review highlights the need for additional work to fill gaps in our understanding of the directionality, causality, and susceptibility throughout the life course.

Endogenous doesn't always mean innocuous: a scoping review of iron toxicity by inhalation

Ambient air pollution is a leading risk factor for the global burden of disease. One possible pathway of particulate matter (PM)-induced toxicity is through iron (Fe), the most abundant metal in the atmosphere. The aim of the review was to consider the complexity of Fe-mediated toxicity following inhalation exposure focusing on the chemical and surface reactivity of Fe as a transition metal and possible pathways of toxicity via reactive oxygen species (ROS) generation as well as considerations of size, morphology, and source of PM. A broad term search of 4 databases identified 2189 journal articles and reports examining exposure to Fe via inhalation in the past 10 years. These were sequentially analyzed by title, abstract and full-text to identify 87 articles publishing results on the toxicity of Fe-containing PM by inhalation or instillation to the respiratory system. The remaining 87 papers were examined to summarize research dealing with in vitro, in vivo and epidemiological studies involving PM containing Fe or iron oxide following inhalation or instillation. The major findings from these investigations are summarized and tabulated. Epidemiological studies showed that exposure to Fe oxide is correlated with an increased incidence of cancer, cardiovascular diseases, and several respiratory diseases. Iron PM was found to induce inflammatory effects in vitro and in vivo and to translocate to remote locations including the brain following inhalation. A potential pathway for the PM-containing Fe-mediated toxicity by inhalation is via the generation of ROS which leads to lipid peroxidation and DNA and protein oxidation. Our recommendations include an expansion of epidemiological, in vivo and in vitro studies, integrating research improvements outlined in this review, such as the method of particle preparation, cell line type, and animal model, to enhance our understanding of the complex biological interactions of these particles.

Respiratory Health Effects of Exposure to Ambient Particulate Matter and Bioaerosols

Researchers have been studying the respiratory health effects of ambient air pollution for more than 70 years. While air pollution as a whole can include gaseous, solid, and liquid constituents, this article focuses only on the solid and liquid fractions, termed particulate matter (PM). Although PM may contain anthropogenic, geogenic, and/or biogenic fractions, in this article, particles that originate from microbial, fungal, animal, or plant sources are distinguished from PM as bioaerosols. Many advances have been made toward understanding which particle and exposure characteristics most influence deposition and clearance processes in the respiratory tract. These characteristics include particle size, shape, charge, and composition as well as the exposure concentration and dose rate. Exposure to particles has been directly associated with the exacerbation and, under certain circumstances, onset of respiratory disease. The circumstances of exposure leading to disease are dependent on stressors such as human activity level and changing particle composition in the environment. Historically, researchers assumed that bioaerosols were too large to be inhaled into the deep lung, and thus, not applicable for study in conjunction with PM2.5 (the 2.5-μm and below size fraction that can reach the deep lung); however, this concept is beginning to be challenged. While there is extensive research on the health effects of PM and bioaerosols independent of each other, only limited work has been performed on their coexposure. Studying these two particle types as dual stressors to the respiratory system may aid in more thoroughly understanding the etiology of respiratory injury and disease. © 2020 American Physiological Society. Compr Physiol 10:1-20, 2020.

Neuropathological lesions in the brains of goats in North-Western Nigeria: possible impact of artisanal mining

Indiscriminate small-scale artisanal gold mining activities were reported to have caused anthropogenic heavy metal environmental pollution in Zamfara State, north-western Nigeria. There is little or no information on the neurotoxic effects and related neuropathological lesions due to environmental pollution in the animal population. Therefore, this work investigated the concentration of heavy metal and associated lesions in the brain of goats around an artisanal mining site in Zamfara. Brain samples were collected from 40 goats at slaughter slabs in Bagega (Zamfara State) while 15 goats with the same demography but without a history of environmental exposure at the time of this study served as controls. The concentration of lead and cadmium in brain tissue and histopathologic changes were assessed using atomic absorption spectrophotometry, histology and immunohistochemistry. The metal concentrations were significantly higher in exposed goats than in the unexposed animals. Cresyl violet staining and glial fibrillary acidic protein (GFAP) immunohistochemistry indicated chromatolysis and increased astrocytic activity respectively in the exposed goats. This study is of epidemiological importance as it shows a generalised increase of the metal concentrations in the brain of goats exposed to artisanal mining in Zamfara, north-western Nigeria. This could have health effects on the animals associated with nervous co-ordination, growth and development and as a good sentinel for pathogenesis of the heavy metal exposure.

Selective memory and behavioral alterations after ambient ultrafine particulate matter exposure in aged 3xTgAD Alzheimer's disease mice

BACKGROUND

A growing body of epidemiological literature indicates that particulate matter (PM) air pollution exposure is associated with elevated Alzheimer's disease (AD) risk and may exacerbate AD-related cognitive decline. Of concern is exposure to the ultrafine PM (UFP) fraction (≤100 nm), which deposits efficiently throughout the respiratory tract, has higher rates of translocation to secondary organs, like brain, and may induce inflammatory changes. We, therefore, hypothesize that exposure to UFPs will exacerbate cognitive deficits in a mouse model of AD. The present study assessed alterations in learning and memory behaviors in aged (12.5 months) male 3xTgAD and non-transgenic mice following a 2-week exposure (4-h/day, 4 days/week) to concentrated ambient UFPs using the Harvard ultrafine concentrated ambient particle system (HUCAPS) or filtered air. Beginning one month following exposure, locomotor activity, spatial learning and memory, short-term recognition memory, appetitive motivation, and olfactory discrimination were assessed.

RESULTS

No effects on locomotor activity were found following HUCAPS exposure (number concentration, 1 × 104-4.7 × 105 particles/cm3; mass concentration, 29-132 μg/m3). HUCAPS-exposed mice, independent of AD background, showed a significantly decreased spatial learning, mediated through reference memory deficits, as well as short-term memory deficits in novel object recognition testing. AD mice displayed diminished spatial working memory, potentially a result of olfactory deficits, and short-term memory. AD background modulated HUCAPS-induced changes on appetitive motivation and olfactory discrimination, specifically enhancing olfactory discrimination in NTg mice. Modeling variation in appetitive motivation as a covariate in spatial learning and memory, however, did not support the conclusion that differences in motivation significantly underlie changes in spatial learning and memory.

CONCLUSIONS

A short-term inhalation exposure of aged mice to ambient UFPs at human-relevant concentrations resulted in protracted (testing spanning 1-6.5 months post-exposure) adverse effects on multiple memory domains (reference and short-term memory) independent of AD background. Impairments in learning and memory were present when accounting for potential covariates like motivational changes and locomotor activity. These results highlight the need for further research into the potential mechanisms underlying the cognitive effects of UFP exposure in adulthood.

The Impact of Inhaled Ambient Ultrafine Particulate Matter on Developing Brain: Potential Importance of Elemental Contaminants

Epidemiological studies report associations between air pollution (AP) exposures and several neurodevelopmental disorders including autism, attention deficit disorder, and cognitive delays. Our studies in mice of postnatal (human third trimester brain equivalent) exposures to concentrated ambient ultrafine particles (CAPs) provide biological plausibility for these associations, producing numerous neuropathological and behavioral features of these disorders, including male-biased vulnerability. These findings raise questions about the specific components of AP that underlie its neurotoxicity, which our studies suggest could involve trace elements as candidate neurotoxicants. X-ray fluorescence analyses of CAP chamber filters confirm contamination of AP exposures by multiple elements, including iron (Fe) and sulfur (S). Correspondingly, laser ablation inductively coupled plasma mass spectrometry of brains of male mice indicates marked postexposure elevations of Fe and S and other elements. Elevations of brain Fe and S in particular are consistent with potential ferroptotic, oxidative stress, and altered antioxidant capacity-based mechanisms of CAPs-induced neurotoxicity, supported by observations of increased serum oxidized glutathione and increased neuronal cell death in nucleus accumbens with no corresponding significant increase in caspase-3, in male brains following postnatal CAP exposures. Understanding the role of trace element contaminants of particulate matter AP as a source of neurotoxicity is critical for public health protection.

Combustion and friction-derived nanoparticles and industrial-sourced nanoparticles: The culprit of Alzheimer and Parkinson's diseases

Redox-active, strongly magnetic, combustion and friction-derived nanoparticles (CFDNPs) are abundant in particulate matter air pollution. Urban children and young adults with Alzheimer disease Continuum have higher numbers of brain CFDNPs versus clean air controls. CFDNPs surface charge, dynamic magnetic susceptibility, iron content and redox activity contribute to ROS generation, neurovascular unit (NVU), mitochondria, and endoplasmic reticulum (ER) damage, and are catalysts for protein misfolding, aggregation and fibrillation. CFDNPs respond to external magnetic fields and are involved in cell damage by agglomeration/clustering, magnetic rotation and/or hyperthermia. This review focus in the interaction of CFDNPs, nanomedicine and industrial NPs with biological systems and the impact of portals of entry, particle sizes, surface charge, biomolecular corona, biodistribution, mitochondrial dysfunction, cellular toxicity, anterograde and retrograde axonal transport, brain dysfunction and pathology. NPs toxicity information come from researchers synthetizing particles and improving their performance for drug delivery, drug targeting, magnetic resonance imaging and heat mediators for cancer therapy. Critical information includes how these NPs overcome all barriers, the NPs protein corona changes as they cross the NVU and the complexity of NPs interaction with soluble proteins and key organelles. Oxidative, ER and mitochondrial stress, and a faulty complex protein quality control are at the core of Alzheimer and Parkinson's diseases and NPs mechanisms of action and toxicity are strong candidates for early development and progression of both fatal diseases. Nanoparticle exposure regardless of sources carries a high risk for the developing brain homeostasis and ought to be included in the AD and PD research framework.

Nanosized carbon black exposure induces neural injury: effects on nicotinamide adenine dinucleotide phosphate oxidases and endoplasmic reticulum stress

Carbon black in ambient air is believed to be the cause of many diseases; however, its potential neural toxicity and the underlying mechanisms remain poorly understood. The present study is to evaluate the toxic effects of carbon black nanoparticles, Printex 90, on the neural cell line PC-12. The study revealed that Printex 90 treatment significantly decreased cell viability, accompanied by an enormous increase in reactive oxygen species generation and a decrease in ATP. Additionally, NOX2 and NOX4, 4-hydroxynonenal, endoplasmic reticulum (ER) stress marker proteins (IRE-1α, ATF-6, GRP78, PERK and the downstream target protein CHOP) and antioxidative enzymes (glutathione and superoxide dismutase) were evaluated. It showed that Printex 90 significantly upregulated 4-hydroxynonenal, NOX2 and NOX4 expression, and the levels, or activity, of glutathione and superoxide dismutase, were markedly reduced. For the ER stress-associated proteins, Printex 90 induced a significant increase of IRE-1α, ATF-6, GRP78, p-PERK and CHOP expression. Collectively, these results demonstrate that NOX and ER stress are involved in Printex 90-mediated neural damage. Therefore, decreased ER stress and NOX-derived reactive oxygen species generation may provide compensatory protective effects and attenuate Printex 90-induced neural injury.

Modifications of autophagy influenced the Alzheimer-like changes in SH-SY5Y cells promoted by ultrafine black carbon

Ambient ultrafine black carbon (uBC) can potentially cross blood-brain barrier, however, very little is currently known about the effects they may have on central nervous system. This study aimed to explore the roles of autophagy in Alzheimer-like pathogenic changes promoted by uBC in SH-SY5Y cells. We firstly found uBC could cause cytotoxicity and oxidative stress in SH-SY5Y cells. Additionally we found uBC initiated progressive development of Alzheimer's disease (AD) associated features, mainly including neuro-inflammation and phosphorylation of tau protein (p-Tau) accumulation. Meanwhile, autophagy process was activated by uBC probably through phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway. RNA interference and autophagosome-lysosome fusion inhibitor were applied to block autophagy process at different stages. Autophagy dysfunction at the initial membrane expansion stage could aggravate p-Tau accumulation and other Alzheimer-like changes in SH-SY5Y cells promoted by uBC. However, autophagy inhibition at the final stage could alleviate p-Tau accumulation caused by uBC. This suggested that inhibition of the infusion of autophagosome and lysosome could possibly activate ubiquitination degradation pathway to regulate p-Tau equilibrium in SH-SY5Y cells. Our findings further raise the concerns about the effects of uBC on the risk of AD and indicate potential roles of autophagy in early Alzheimer-like pathogenic changes caused by ambient uBC.

Air Pollution and Stroke

The adverse health effects of air pollution have long been recognised; however, there is less awareness that the majority of the morbidity and mortality caused by air pollution is due to its effects on the cardiovascular system. Evidence from epidemiological studies have demonstrated a strong association between air pollution and cardiovascular diseases including stroke. Although the relative risk is small at an individual level, the ubiquitous nature of exposure to air pollution means that the absolute risk at a population level is on a par with "traditional" risk factors for cardiovascular disease. Of particular concern are findings that the strength of this association is stronger in low and middle income countries where air pollution is projected to rise as a result of rapid industrialisation. The underlying biological mechanisms through which air pollutants exert their effect on the vasculature are still an area of intense discussion. A greater understanding of the effect size and mechanisms is necessary to develop effective strategies at individual and policy levels to mitigate the adverse cardiovascular effects of air pollution.