Telomere Length, Long-Term Black Carbon Exposure, and Cognitive Function in a Cohort of Older Men: The VA Normative Aging Study

Associations between solar and geomagnetic activity and cognitive function in the Normative Aging study

BACKGROUND

Studies show that changes in solar and geomagnetic activity (SGA) influence melatonin secretion and the autonomic nervous system. We evaluated associations between solar and geomagnetic activity and cognitive function in the Normative Aging Study from 1992 to 2013.

METHODS

We used logistic and linear generalized estimating equations and regressions to evaluate the associations between moving averages of sunspot number (SSN) and Kp index (a measure of geomagnetic activity) and a binary measure for Mini-Mental State Examination (MMSE) scores (≤25 or > 25) and six other cognitive tests as continuous measures, combined into one global composite score and considered separately.

RESULTS

A one-IQR increase in same-day SSN and Kp index were associated with 17% (95% CI: 3%, 34%) and 19% (95% CI: 4%, 36%) increases in the odds of low MMSE score. We observed small increases in the global cognitive score with increasing SSN, although we observed decreases specifically in relation to the backwards digit span test.

CONCLUSIONS

Periods of high SGA were associated with cognitive function. SGA may not equally impact all aspects of cognitive function, as evidenced by differences in associations observed for the MMSE, global cognitive score, and individual cognitive tests. Given that much of the pathology of cognitive decline in the elderly remains unexplained, studies specifically targeting decline and with longer follow-up periods are warranted.

Prenatal exposure to air pollution and BWGA Z-score: Modifying effects of placenta leukocyte telomere length and infant sex

BACKGROUND

Air pollutants, such as fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3), have been associated with adverse birth outcomes, including low birth weight, often exhibiting sex-specific effects. However, the modifying effect of placental telomere length (TL), reflecting cumulative lifetime oxidative stress in mothers, remains unexplored.

METHOD

Using data from a Northeastern U.S. birth cohort (n = 306), we employed linear regression and weighted quantile sum models to assess trimester-average air pollution exposures and birth weight for gestational age (BWGA) z-scores. Placental TL, categorized by median split, was considered as an effect modifier. Interactions among air pollutants, placental TL, infant sex, and BWGA z-score were evaluated.

RESULTS

Without placental TL as a modifier, only 1st trimester O3 was significantly associated with BWGA z-scores (coefficient: 0.33, 95% CI: 0.03, 0.63). In models considering TL interactions, a significant modifying effect was observed between 3rd trimester NO2 and BWGA z-scores (interaction p-value = 0.02). Specifically, a one interquartile range (1-IQR) increase in 3rd trimester NO2 was linked to a 0.28 (95% CI: 0.06, 0.52) change in BWGA z-score among shorter placental TL group, with no significant association among longer TL group. Among male infants, there were significant associations between 3rd trimester PM2.5 exposure and BWGA z-scores in the longer TL group (coefficient: -0.34, 95% CI: -0.61, -0.02), and between 1st trimester O3 exposure and BWGA z-scores among males in the shorter TL group (coefficient: 0.59, 95% CI: 0.06, 1.08). For females, only a negative association in 2nd trimester mixture model was observed within the longer TL group (coefficient: -0.10, 95% CI: -0.21, -0.01).

CONCLUSION

These findings highlight the need to consider the complex interactions among prenatal air pollutant exposures, placental TL, and fetal sex to better elucidate those at greatest risk for adverse birth outcomes.

Sources and composition of elemental carbon during haze events in North China by a high time-resolved study

Despite the implementation of stringent emission reduction measures in the past year, severe winter haze events still occurred frequently in North China, with only marginal decreases observed in elemental carbon (EC) concentrations. EC not only constitutes a fraction of particle mass but also interacts with boundary layer and influences haze formation. Given the complex composition of EC, characterizing its sources and composition during haze processes is challenging yet crucial for understanding haze formation and evolution. Here, hourly-resolution PM2.5 samples were collected during three different haze event (P1-P3) in the North China Plain to investigate dynamic changes in EC source across different haze processes. The average EC concentrations and char/soot ratios were 9.94 ± 4.80 μgC·m-3, 14.5 ± 6.93 μgC·m-3, 15.9 ± 5.54 μgC·m-3, and 2.42 ± 0.98, 2.70 ± 0.88, 2.61 ± 0.95 for P1, P2 and P3, respectively. Backward trajectory analysis showed distinct variations in EC concentration and composition under the influence of different air masses during the three haze events, with local air masses influenced days exhibiting higher EC concentrations and char/soot ratios. The char/soot ratio based diagnostic method suggested that EC was predominantly influenced by coal combustion and vehicle emissions. Further positive matrix factorization analysis suggested that biomass burning and residential coal combustion were the main contributors of EC (58 %) and played a dominant role in driving variations in EC concentrations during haze episodes. Potential source contribution function analysis results highlight that local biomass burning and residential coal combustion could be major reason for the EC elevation in different haze events. Our results provide valuable insights into the sources and composition of EC during haze events, facilitating the implementation of effective measures for mitigating both EC and PM pollution.

Examining the Cross-sectional Association Between Neighborhood Conditions, Discrimination, and Telomere Length in a Predominantly African American Sample

Disproportionate exposure to adverse neighborhood conditions and greater discrimination may contribute to health disparities among African Americans (AAs). We examined whether adverse neighborhood conditions, alone or in conjunction with discrimination, associate with shorter leukocyte telomere length among a predominantly AA cohort. The sample included 200 residents from two low-income neighborhoods (96% AA; mean age = 67 years). Perceived neighborhood conditions and discrimination were surveyed in 2018, and objective neighborhood conditions (total crime rate, neighborhood walkability, ambient air pollution (PM2.5, black carbon)) were collected in 2017/2018. Relative telomere length (T/S; ratio of telomeric DNA to a single-gene copy) was assessed from blood samples. Linear regression models estimated the main effects of each neighborhood condition and discrimination and their interactions on the T/S ratio. Less walkable neighborhoods were associated with shorter telomeres. Higher air pollution (PM2.5) was associated with shorter telomeres among those experiencing greater discrimination. Findings highlight the importance of understanding the intersecting influences of historic and contemporary sources of systemic racism and how they contribute to accelerated aging among adults.

Aging, longevity, and the role of environmental stressors: a focus on wildfire smoke and air quality

Aging is a complex biological process involving multiple interacting mechanisms and is being increasingly linked to environmental exposures such as wildfire smoke. In this review, we detail the hallmarks of aging, emphasizing the role of telomere attrition, cellular senescence, epigenetic alterations, proteostasis, genomic instability, and mitochondrial dysfunction, while also exploring integrative hallmarks - altered intercellular communication and stem cell exhaustion. Within each hallmark of aging, our review explores how environmental disasters like wildfires, and their resultant inhaled toxicants, interact with these aging mechanisms. The intersection between aging and environmental exposures, especially high-concentration insults from wildfires, remains under-studied. Preliminary evidence, from our group and others, suggests that inhaled wildfire smoke can accelerate markers of neurological aging and reduce learning capabilities. This is likely mediated by the augmentation of circulatory factors that compromise vascular and blood-brain barrier integrity, induce chronic neuroinflammation, and promote age-associated proteinopathy-related outcomes. Moreover, wildfire smoke may induce a reduced metabolic, senescent cellular phenotype. Future interventions could potentially leverage combined anti-inflammatory and NAD + boosting compounds to counter these effects. This review underscores the critical need to study the intricate interplay between environmental factors and the biological mechanisms of aging to pave the way for effective interventions.

Global rural health disparities in Alzheimer's disease and related dementias: State of the science

INTRODUCTION

Individuals living in rural communities are at heightened risk for Alzheimer's disease and related dementias (ADRD), which parallels other persistent place-based health disparities. Identifying multiple potentially modifiable risk factors specific to rural areas that contribute to ADRD is an essential first step in understanding the complex interplay between various barriers and facilitators.

METHODS

An interdisciplinary, international group of ADRD researchers convened to address the overarching question of: "What can be done to begin minimizing the rural health disparities that contribute uniquely to ADRD?" In this state of the science appraisal, we explore what is known about the biological, behavioral, sociocultural, and environmental influences on ADRD disparities in rural settings.

RESULTS

A range of individual, interpersonal, and community factors were identified, including strengths of rural residents in facilitating healthy aging lifestyle interventions.

DISCUSSION

A location dynamics model and ADRD-focused future directions are offered for guiding rural practitioners, researchers, and policymakers in mitigating rural disparities.

HIGHLIGHTS

Rural residents face heightened Alzheimer's disease and related dementia (ADRD) risks and burdens due to health disparities. Defining the unique rural barriers and facilitators to cognitive health yields insight. The strengths and resilience of rural residents can mitigate ADRD-related challenges. A novel "location dynamics" model guides assessment of rural-specific ADRD issues.

The Relationship Between Telomeres, Cognition, Mood, and Physical Function: A Systematic Review

Background and Purpose: Cognitive, affective, and physical symptoms and alterations in their function are seen across chronic illnesses. Data suggest that environmental, psychological, and physiological factors contribute to symptom experience, potentially through loss of telomeres (telomere attrition), structures at the ends of chromosomes. Telomere length is affected by many factors including environmental (e.g., exercise, diet, smoking) and physiological (e.g., response to stress), as well as from oxidative damage and inflammation that occurs in many disease processes. Moreover, telomere attrition is associated with chronic disease (cancer, cardiovascular disease, Alzheimer's disease) and predicts higher morbidity and mortality rates. However, findings are inconsistent among telomere roles and relationships with health outcomes. This article aims to synthesize the current state-of-the-science of telomeres and their relationship with cognitive, affective, and physical function and symptoms. Method: A comprehensive literature search was performed in two databases: CINAHL and PUBMED. A total of 33 articles published between 2000 and 2022 were included in the final analysis. Results: Telomere attrition is associated with various changes in cognitive, affective, and physical function and symptoms. However, findings are inconsistent. Interventional studies (e.g., meditation and exercise) may affect telomere attrition, potentially impacting health outcomes. Conclusion: Nursing research and practice are at the forefront of furthering the understanding of telomeres and their relationships with cognitive, affective, and physical function and symptoms. Future interventions targeting modifiable risk factors may be developed to improve health outcomes across populations.

Work-Related Psychosocial Factors and Global Cognitive Function: Are Telomere Length and Low-Grade Inflammation Potential Mediators of This Association?

The identification of modifiable factors that could maintain cognitive function is a public health priority. It is thought that some work-related psychosocial factors help developing cognitive reserve through high intellectual complexity. However, they also have well-known adverse health effects and are considered to be chronic psychosocial stressors. Indeed, these stressors could increase low-grade inflammation and promote oxidative stress associated with accelerated telomere shortening. Both low-grade inflammation and shorter telomeres have been associated with a cognitive decline. This study aimed to evaluate the total, direct, and indirect effects of work-related psychosocial factors on global cognitive function overall and by sex, through telomere length and an inflammatory index. A random sample of 2219 participants followed over 17 years was included in this study, with blood samples and data with cognitive function drawn from a longitudinal study of 9188 white-collar workers (51% female). Work-related psychosocial factors were evaluated according to the Demand-Control-Support and the Effort-Reward Imbalance (ERI) models. Global cognitive function was evaluated with the validated Montreal Cognitive Assessment (MoCA). Telomere length and inflammatory biomarkers were measured using standardised protocols. The direct and indirect effects were estimated using a novel mediation analysis method developed for multiple correlated mediators. Associations were observed between passive work or low job control, and shorter telomeres among females, and between low social support at work, ERI or iso-strain, and a higher inflammatory index among males. An association was observed with higher cognitive performance for longer telomeres, but not for the inflammatory index. Passive work overall, and low reward were associated with lower cognitive performance in males; whereas, high psychological demand in both males and females and high job strain in females were associated with a higher cognitive performance. However, none of these associations were mediated by telomere length or the inflammatory index. This study suggests that some work-related psychosocial factors could be associated with shorter telomeres and low-grade inflammation, but these associations do not explain the relationship between work-related psychosocial factors and global cognitive function. A better understanding of the biological pathways, by which these factors affect cognitive function, could guide future preventive strategies to maintain cognitive function and promote healthy aging.

Air pollution and human cognition: A systematic review and meta-analysis

BACKGROUND

This systematic review summarises and evaluates the literature investigating associations between exposure to air pollution and general population cognition, which has important implications for health, social and economic inequalities, and human productivity.

METHODS

The engines MEDLINE, Embase Classic+Embase, APA PsycInfo, and SCOPUS were searched up to May 2022. Our inclusion criteria focus on the following pollutants: particulate matter, NOx, and ozone. The cognitive abilities of interest are: general/global cognition, executive function, attention, working memory, learning, memory, intelligence and IQ, reasoning, reaction times, and processing speed. The collective evidence was assessed using the NTP-OHAT framework and random-effects meta-analyses.

RESULTS

Eighty-six studies were identified, the results of which were generally supportive of associations between exposures and worsened cognition, but the literature was varied and sometimes contradictory. There was moderate certainty support for detrimental associations between PM_2.5 and general cognition in adults 40+, and PM_2.5, NOx, and PM₁₀ and executive function (especially working memory) in children. There was moderate certainty evidence against associations between ozone and general cognition in adults age 40+, and NOx and reasoning/IQ in children. Some associations were also supported by meta-analysis (N = 14 studies, all in adults aged 40+). A 1 μg/m³ increase in NO₂ was associated with reduced performance on general cognitive batteries (β = -0.02, p < 0.05) as was a 1 μg/m³ increase in PM_2.5 exposure (β = -0.02, p < 0.05). A 1μgm³ increase in PM_2.5 was significantly associated with lower verbal fluency by -0.05 words (p = 0.01) and a decrease in executive function task performance of -0.02 points (p < 0.001).

DISCUSSION

Evidence was found in support of some exposure-outcome associations, however more good quality research is required, particularly with older teenagers and young adults (14-40 years), using multi-exposure modelling, incorporating mechanistic investigation, and in South America, Africa, South Asia and Australasia.

Long-term exposure to ambient air pollution and cognitive function in older US adults: The Multi-Ethnic Study of Atherosclerosis

Air pollution effects on cognitive function have been increasingly recognized. Little is known about the impact of different sources of fine particulate (PM2.5). We aim to evaluate the associations between long-term air pollution exposure, including source-specific components in PM2.5, and cognition in older adults.

Methods

Cognitive assessment, including the Cognitive Abilities Screening Instrument (CASI), Digit Symbol Coding (DSC), and Digit Span (DS), was completed in 4392 older participants in the United States during 2010-2012. Residence-specific air pollution exposures (i.e., oxides of nitrogen [NO2/NOx], PM2.5 and its components: elemental carbon [EC], organic carbon [OC], sulfur [S], and silicon [Si]) were estimated by geo-statistical models. Linear and logistic regression models were used to estimate the associations between each air pollutants metric and cognitive function.

Results

An interquartile range (IQR) increase in EC (0.8 μg/m3) and Si (23.1 ng/m3) was associated with -1.27 (95% confidence interval [CI]: -0.09, -2.45) and -0.88 (95% CI: -0.21, -1.54) lower CASI scores in global cognitive function. For each IQR increase in Si, the odds of low cognitive function (LCF) across domains was 1.29 times higher (95% CI: 1.04, 1.60). For other tests, NO X was associated with slower processing speed (DSC: -2.01, 95% CI: -3.50, -0.52) and worse working memory (total DS: -0.4, 95% CI: -0.78, -0.01). No associations were found for PM2.5 and two PM2.5 components (OC and S) with any cognitive function outcomes.

Conclusion

Higher exposure to traffic-related air pollutants including both tailpipe (EC and NO x ) and non-tailpipe (Si) species were associated with lower cognitive function in older adults.

Effects of air pollution on telomere length: Evidence from in vitro to clinical studies

Air pollution remains the major environmental problem globally. There is extensive evidence showing that the variety of air pollutants from environmental and occupational exposures cause adverse effects to our health. The clinical symptoms of those effects may present at a late stage, so surveillance is difficult to manage. Several biomarkers have been used for the early detection of health issues following exposure to air pollution, including the use of telomere length which indicates cellular senescence in response to oxidative stress. Oxidative stress is one of the most plausible mechanisms associated with exposure to air pollutants. Some specific contexts including age groups, gender, ethnicity, occupations, and health conditions, showed significant alterations in telomere length after exposure to air pollutants. Several reports demonstrated both negative and positive associations between telomere length and air pollution, the studies using different concentrations and exposure times to air pollution on the study of telomere lengths. Surprisingly, some studies reported that low levels of exposure to air pollutants (lower than regulated levels) caused the alterations in telomere length. Those findings suggest that telomere length could be one of most practical biomarkers in air pollution surveillance. Therefore, this review aimed to summarize and discuss the relationship between telomere length and exposure to air pollution. The knowledge from this review will be beneficial for the planning of public health to reduce health problems in the general population, particularly in vulnerable people, who still live in areas with high air pollution.

Air Pollution and Cognitive Impairment across the Life Course in Humans: A Systematic Review with Specific Focus on Income Level of Study Area

Cognitive function is a crucial determinant of human capital. The Lancet Commission (2020) has recognized air pollution as a risk factor for dementia. However, the scientific evidence on the impact of air pollution on cognitive outcomes across the life course and across different income settings, with varying levels of air pollution, needs further exploration. A systematic review was conducted, using Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) Guidelines to assess the association between air pollution and cognitive outcomes across the life course with a plan to analyze findings as per the income status of the study population. The PubMed search included keywords related to cognition and to pollution (in their titles) to identify studies on human participants published in English until 10 July 2020. The search yielded 84 relevant studies that described associations between exposure to air pollutants and an increased risk of lower cognitive function among children and adolescents, cognitive impairment and decline among adults, and dementia among older adults with supportive evidence of neuroimaging and inflammatory biomarkers. No study from low- and middle-income countries (LMICs)was identified despite high levels of air pollutants and high rates of dementia. To conclude, air pollution may impair cognitive function across the life-course, but a paucity of studies from reLMICs is a major lacuna in research.

Long-term exposure to fine particulate matter, lung function and cognitive performance: A prospective Dutch cohort study on the underlying routes

BACKGROUND

Exposure to fine particulate matter and black carbon is related to cognitive impairment and poor lung function, but less is known about the routes taken by different types of air pollutants to affect cognition.

OBJECTIVES

We tested two possible routes of fine particulate matter (PM_2.5) and black carbon (BC) in impairing cognition, and evaluated their importance: a direct route over the olfactory nerve or the blood stream, and an indirect route over the lung.

METHODS

We used longitudinal observational data for 49,705 people aged 18+ from 2006 to 2015 from the Dutch Lifelines cohort study. By linking current home addresses to air pollution exposure data from ELAPSE in 2010, long-term average exposure to PM_2.5 and BC was assessed. Lung function was measured by spirometry and Global Initiative (GLI) z-scores of forced expiratory volume in 1s (FEV₁) and forced vital capacity (FVC) were calculated. Cognitive performance was measured by cognitive processing time (CPT) assessed by the Cogstate Brief Battery. Linear structural equation modeling was performed to test direct/indirect associations.

RESULTS

Higher exposure to PM_2.5 but not BC was related to higher CPT and slower cognitive processing speed [Total Effect PM_2.5: FEV₁ model = 8.31 × 10^-3 (95% CI: 5.71 × 10^-3, 10.91 × 10^-3), FVC model = 8.30 × 10^-3 (95% CI: 5.69 × 10^-3, 10.90 × 10^-3)]. The direct association of PM_2.5 constituted more than 97% of the total effect. Mediation by lung function was low for PM_2.5 with a mediated proportion of 1.32% (FEV₁) and 2.05% (FVC), but higher for BC (7.01% and 13.82% respectively).

DISCUSSION

Our results emphasise the importance of the lung acting as a mediator in the relationship between both exposure to PM_2.5 and BC, and cognitive performance. However, higher exposure to PM_2.5 was mainly directly associated with worse cognitive performance, which emphasises the health-relevance of fine particles due to their ability to reach vital organs directly.

Acute effects of short-term exposure to ambient air pollution on reproductive hormones in young males of the MARHCS study in China

Air pollution, which is associated with male reproductive health. However, it is unknown the acute effects of ambient air pollutants exposure on male reproductive hormones. The current study, we measured serum levels of reproductive hormone in 2030 blood samples gathered from The Male Reproductive Health in Chongqing College Students (MARHCS) cohort study. We derived a full coverage of ambient air pollutant (PM₁₀, PM_2.5, SO₂, NO₂, CO and O₃) concentrations by employing machine learning algorithms, and used a mixed-effect model to estimate single-day and cumulative effects of air pollutants exposure on serum reproductive hormones. Our results showed that (1) PM₁₀ and PM_2.5 concentrations were positively associated with estradiol (E₂) in both single and cumulative lag days, but were negatively associated with the ratio of Testosterone/E₂ (the T/E₂ ratio). NO₂ was positively associated with estradiol at lag day 2 (95% CI: 0.290, 0.881; corrected P = 0.048) and lag 0-2 days (95% CI: 0.523, 1.337; corrected P = 0.003), with progesterone (P) at lag day 2 and lag day 3 (corrected P < 0.05). There was also a positive association between CO exposure and progesterone at lag day 2. (2) SO₂ was inversely associated with E₂ at lag day 3, 4 and lag 0-4 days, and progesterone at lag day 0, 1, 2 and lag 0-1, 0-2, 0-4 days, but positively associated with the T/E₂ ratio at lag day 3, 4 and lag 0-4 days (corrected P < 0.05). O₃ exposure was negatively associated with E₂ at lag day 3 (95% CI: -0.216, -0.074, corrected P = 0.03). (3) No significant associations were found between the cumulative daily average air pollutant exposure of CO, O₃ and hormone outcomes. This study suggests that short-term exposure to air pollutants may thus alter reproductive hormone levels, especially on serum estradiol, progesterone levels and the T/E₂ ratio.

Short-term air pollution, cognitive performance and nonsteroidal anti-inflammatory drug use in the Veterans Affairs Normative Aging Study

Air pollution, especially the fine particulate matter (PM_2.5), may impair cognitive performance^1-3, but its short-term impact remains poorly understood. We investigated the short-term associations of PM_2.5 with the cognitive performances of 954 white males measured as the global cognitive function (GCF) and Mini-Mental State Examination (MMSE) scores, and further explored whether taking nonsteroidal anti-inflammatory drugs (NSAIDs) could modify their relationships. Higher short-term exposure to PM_2.5 demonstrated non-linear negative associations with cognitive function. Compared with the lowest quartile of the 28-day average PM_2.5 concentration, the 2^nd, 3^rd, and 4^th quartiles were associated with 0.378-, 0.376-, and 0.499-unit decreases in GCF score, 0.484-, 0.315-, and 0.414-unit decreases in MMSE score, and 69%, 45%, and 63% greater odds of low MMSE scores (≤25), respectively. Such adverse effects were attenuated among NSAIDs users compared to non-users. This study elucidates the short-term impacts of air pollution on cognition and warrants further investigations on the modifying effects of NSAIDs.

Contribution of Long-Term Exposure to Outdoor Black Carbon to the Carcinogenicity of Air Pollution: Evidence regarding Risk of Cancer in the Gazel Cohort

BACKGROUND

Black carbon (BC), a component of fine particulate matter [particles with an aerodynamic diameter ≤2.5 μm (PM2.5)], may contribute to carcinogenic effects of air pollution. Until recently however, there has been little evidence to evaluate this hypothesis.

OBJECTIVE

This study aimed to estimate the associations between long-term exposure to BC and risk of cancer. This study was conducted within the French Gazel cohort of 20,625 subjects.

METHODS

We assessed exposure to BC by linking subjects' histories of residential addresses to a map of European black carbon levels in 2010 with back- and forward-extrapolation between 1989 and 2015. We used extended Cox models, with attained age as time-scale and time-varying cumulative exposure to BC, adjusted for relevant sociodemographic and lifestyle variables. To consider latency between exposure and cancer diagnosis, we implemented a 10-y lag, and as a sensitivity analysis, a lag of 2 y. To isolate the effect of BC from that of total PM2.5, we regressed BC on PM2.5 and used the residuals as the exposure variable.

RESULTS

During the 26-y follow-up period, there were 3,711 incident cancer cases (all sites combined) and 349 incident lung cancers. Median baseline exposure in 1989 was 2.65 10-5/m [interquartile range (IQR): 2.23-3.33], which generally slightly decreased over time. Using 10 y as a lag-time in our models, the adjusted hazard ratio per each IQR increase of the natural log-transformed cumulative BC was 1.17 (95% confidence interval: 1.06, 1.29) for all-sites cancer combined and 1.31 (0.93, 1.83) for lung cancer. Associations with BC residuals were also positive for both outcomes. Using 2 y as a lag-time, the results were similar.

DISCUSSION

Our findings for a cohort of French adults suggest that BC may partly explain the association between PM2.5 and lung cancer. Additional studies are needed to confirm our results and further disentangle the effects of BC, total PM2.5, and other constituents. https://doi.org/10.1289/EHP8719.

A critical review of the epidemiological evidence of effects of air pollution on dementia, cognitive function and cognitive decline in adult population

Dementia is arguably the most pressing public health challenge of our age. Since dementia does not have a cure, identifying risk factors that can be controlled has become paramount to reduce the personal, societal and economic burden of dementia. The relationship between exposure to air pollution and effects on cognitive function, cognitive decline and dementia has stimulated increasing scientific interest in the past few years. This review of the literature critically examines the available epidemiological evidence of associations between exposure to ambient air pollutants, cognitive performance, acceleration of cognitive decline, risk of developing dementia, neuroimaging and neurological biomarker studies, following Bradford Hill guidelines for causality. The evidence reviewed has been consistent in reporting associations between chronic exposure to air pollution and reduced global cognition, as well as impairment in specific cognitive domains including visuo-spatial abilities. Cognitive decline and dementia incidence have also been consistently associated with exposure to air pollution. The neuro-imaging studies reviewed report associations between exposure to air pollution and white matter volume reduction. Other reported effects include reduction in gray matter, larger ventricular volume, and smaller corpus callosum. Findings relating to ischemic (white matter hyperintensities/silent cerebral infarcts) and hemorrhagic (cerebral microbleeds) markers of cerebral small vessel disease have been heterogeneous, as have observations on hippocampal volume and air pollution. The few studies available on neuro-inflammation tend to report associations with exposure to air pollution. Several effect modifiers have been suggested in the literature, but more replication studies are required. Traditional confounding factors have been controlled or adjusted for in most of the reviewed studies. Additional confounding factors have also been considered, but the inclusion of these has varied among the different studies. Despite all the efforts to adjust for confounding factors, residual confounding cannot be completely ruled out, especially since the factors affecting cognition and dementia are not yet fully understood. The available evidence meets many of the Bradford Hill guidelines for causality. The reported associations between a range of air pollutants and effects on cognitive function in older people, including the acceleration of cognitive decline and the induction of dementia, are likely to be causal in nature. However, the diversity of study designs, air pollutants and endpoints examined precludes the attribution of these adverse effects to a single class of pollutant and makes meta-analysis inappropriate.

Association between prenatal immune phenotyping and cord blood leukocyte telomere length in the PRISM pregnancy cohort

BACKGROUND

Environmental exposures including air pollutants, toxic metals, and psychosocial stress have been associated with shorter telomere length (TL) in newborns. These exposures have in turn been linked to an enhanced inflammatory immune response. Increased inflammation during pregnancy may be a central biological pathway linking environmental factors with reduced TL at birth. Approaches that more comprehensively characterize the prenatal inflammatory milieu rather than targeting specific individual cytokines in relation to newborn TL may better elucidate inflammatory mechanisms.

METHODS

Analyses included 129 mother-child dyads enrolled in the PRogramming of Intergenerational Stress Mechanisms (PRISM) pregnancy cohort. We measured 92 inflammation related proteins during pregnancy in maternal serum using the Olink protein array and quantified cord blood relative leukocyte TL (rLTL) via qPCR. We leveraged a tree-based machine learning algorithm to select the most important inflammatory related proteins jointly associated with rLTL. We then evaluated the combined association between the selected proteins with rLTL using Bayesian Weighted Quantile Sum (BWQS) Regression. Analyses were adjusted for gestational week of serum collection, maternal race/ethnicity, age, and education, and fetal sex. We evaluated major biological function of the identified proteins by using the UniProtKB, a centralized repository of curated functional information.

RESULTS

Three proteins were negatively and linearly associated with rLTL (CASP8 β: -0.22 p = 0.008, BNGF β: -0.43 p = 0.033, TRANCE β: 0.38 p = 0.004). Results from BWQS regression showed a significant overall decrease in rLTL (β: -0.26 95%CrI: -0.43, -0.07) per quartile increase of the mixture, with CASP8 contributing the greatest weight (CASP8 50%; BNGF 27%, and TRANCE 23%). The identified proteins were involved in the regulation of apoptotic processes and cell proliferation.

CONCLUSIONS

This proteomics approach identifies novel maternal prenatal inflammatory protein biomarkers associated with shortened rLTL in newborns.

Air Pollution and Dementia: A Systematic Review

Background:

Both air pollution and dementia are current and growing global issues. There are plausible links between exposure to specific air pollutants and dementia.

Objective:

To systematically review the evidence base with respect to the relationship between air pollution and later cognitive decline and dementia.

Methods:

Medline, Embase, and PsychINFO^® were searched from their inception to September 2018, for publications reporting on longitudinal studies of exposure to air pollution and incident dementia or cognitive decline in adults. Studies reporting on exposure to tobacco smoke including passive smoking or on occupational exposure to pollutants were excluded. Using standard Cochrane methodology, two readers identified relevant abstracts, read full text publications, and extracted data into structured tables from relevant papers, as defined by inclusion and exclusion criteria. Papers were also assessed for validity. CRD42018094299

Results:

From 3,720 records, 13 papers were found to be relevant, with studies from the USA, Canada, Taiwan, Sweden, and the UK. Study follow-up ranged from one to 15 years. Pollutants examined included particulate matter ≤2.5 μ (PM_2.5), nitrogen dioxide (NO₂), nitrous oxides (NO_x), carbon monoxide (CO), and ozone. Studies varied in their methodology, population selection, assessment of exposure to pollution, and method of cognitive testing. Greater exposure to PM_2.5, NO₂/NO_x, and CO were all associated with increased risk of dementia. The evidence for air pollutant exposure and cognitive decline was more equivocal.

Conclusion:

Evidence is emerging that greater exposure to airborne pollutants is associated with increased risk of dementia.

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

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

Comparative validation of an epigenetic mortality risk score with three aging biomarkers for predicting mortality risks among older adult males

BACKGROUND

A 'mortality risk score' (MS) based on ten prominent mortality-related cytosine-phosphate-guanine (CpG) sites was previously associated with all-cause mortality, but has not been verified externally. We aimed to validate the association of MS with mortality and to compare MS with three aging biomarkers: telomere length (TL), DNA methylation age (DNAmAge) and phenotypic age (DNAmPhenoAge) to explore whether MS can serve as a reliable measure of biological aging and mortality.

METHODS

Among 534 males aged 55-85 years from the US Normative Aging Study, the MS, DNAmAge and DNAmPhenoAge were derived from blood DNA methylation profiles from the Illumina HumanMethylation450 BeadChip, and TL was measured by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

A total of 147 participants died during a median follow-up of 9.4 years. The MS showed strong associations with all-cause, cardiovascular disease (CVD) and cancer mortality. After controlling for all potential covariates, participants with high MS (>5 CpG sites with aberrant methylation) had almost 4-fold all-cause mortality (hazard ratio: 3.84, 95% confidence interval: 1.92-7.67) compared with participants with a low MS (0-1 CpG site with aberrant methylation). Similar patterns were observed with respect to CVD and cancer mortality. MS was associated with TL and DNAmPhenoAge acceleration but not with DNAmAge acceleration. Although the MS and DNAmPhenoAge acceleration were independently associated with all-cause mortality, the former exhibited a higher predictive accuracy of mortality than the latter.

CONCLUSIONS

MS has the potential to be a prominent predictor of mortality that could enhance survival prediction in clinical settings.

Biomarkers of aging and lung function in the normative aging study

Elderly individuals who are never smokers but have the same height and chronological age can have substantial differences in lung function. The underlying biological mechanisms are unclear. To evaluate the associations of different biomarkers of aging (BoA) and lung function, we performed a repeated-measures analysis in the Normative Aging Study using linear mixed-effect models. We generated GrimAgeAccel, PhenoAgeAccel, extrinsic and intrinsic epigenetic age acceleration using a publically available online calculator. We calculated Zhang's DNAmRiskScore based on 10 CpGs. We measured telomere length (TL) and mitochondrial DNA copy number (mtDNA-CN) using quantitative real-time polymerase chain reaction. A pulmonary function test was performed measuring forced expiratory volume in 1 second / forced vital capacity (FEV₁/FVC), FEV₁, and maximum mid-expiratory flow (MMEF). Epigenetic-based BoA were associated with lower lung function. For example, a one-year increase in GrimAgeAccel was associated with a 13.64 mL [95% confidence interval (CI), 5.11 to 22.16] decline in FEV₁; a 0.2 increase in Zhang's DNAmRiskScore was associated with a 0.009 L/s (0.005 to 0.013) reduction in MMEF. No association was found between TL/mtDNA-CN and lung function. Overall, this paper shows that epigenetics might be a potential mechanism underlying pulmonary dysfunction in the elderly.

Mitochondria and aging in older individuals: an analysis of DNA methylation age metrics, leukocyte telomere length, and mitochondrial DNA copy number in the VA normative aging study

Population aging is a looming global health challenge. New biological aging metrics based on DNA methylation levels have been developed in addition to traditional aging biomarkers. The prospective relationships of aging biomarkers with mitochondrial changes are still not well understood. Here, we examined the prospective associations of mitochondrial copy number (mtDNAcn) with several aging biomarkers – DNAm-Age, DNAm-PhenoAge, DNAm-GrimAge, and leukocyte telomere length. We analyzed 812 individuals from Veteran Affairs Normative Aging Study (NAS) with available blood samples from 1999-2013. Whole blood mtDNAcn and relative leukocyte telomere length were measured via qPCR. DNA methylation was assessed and used to calculate DNAm-Age, DNAm-GrimAge, and DNAm-PhenoAge. Linear mixed models were used to quantify the associations of mtDNAcn with DNAm-Age, DNAm-GrimAge, DNAm-PhenoAge, and leukocyte telomere length. In multivariable cross-sectional analyses, mtDNAcn is negatively associated with DNAm-Age PhenoAge and DNAm-PhenoAge. In contrast, mtDNAcn is associated with prospective measures of higher DNAm-PhenoAge and shorter leukocyte telomere length. Our study shows that higher mtDNAcn is associated with prospective measures of greater DNAm-PhenoAge and shorter leukocyte telomere length independent of chronological age. This indicates a role for mitochondrial in aging-related disease and mortality, but not the departure of biological age from chronological age.

Air Pollution Exposure and Cognitive Function in Taiwanese Older Adults: A Repeated Measurement Study

Studies related to air pollution exposure and neurocognitive disorders, specifically cognitive impairment, among older adults are limited. We investigated the association between short-term and long-term exposure to ambient air pollution (i.e., particulate matter with an aerodynamic diameter of <10 μm and ozone) and the effects of their interaction on cognitive function in a community-dwelling, free-living elderly population. Study participants were in a multiple-wave representative sample, namely the Taiwan Longitudinal Study on Aging (n = 2241). In four surveys between 1996 and 2007, their cognitive function was assessed using the Short Portable Mental Status Questionnaire (SPMSQ). We estimated air pollution from 1993 to 2007, including daily concentrations of PM₁₀ and O₃ from air quality monitoring stations, based on the administrative zone of each participant’s residence. Generalized linear mixed models were used to examine these associations after adjusting for covariates. We found that long-term exposure to PM₁₀ and O₃ was significantly associated with cognitive impairment (OR = 1.094, 95% CI: 1.020, 1.174 for PM₁₀; OR = 1.878, 95% CI: 1.363, 2.560 for O₃). The joint effect of exposure to PM₁₀ and O₃ was associated with cognitive impairment (p < 0.001). Co-exposure to ambient PM₁₀ and O₃ may deteriorate cognitive function in older adults.

Prenatal and Childhood Traffic-Related Air Pollution Exposure and Telomere Length in European Children: The HELIX Project

BACKGROUND

Telomere length is a molecular marker of biological aging.

OBJECTIVE

Here we investigated whether early-life exposure to residential air pollution was associated with leukocyte telomere length (LTL) at 8 y of age.

METHODS

In a multicenter European birth cohort study, HELIX (Human Early Life Exposome) ([Formula: see text]), we estimated prenatal and 1-y childhood exposure to nitrogen dioxide ([Formula: see text]), particulate matter with aerodynamic diameter [Formula: see text] ([Formula: see text]), and proximity to major roads. Average relative LTL was measured using quantitative real-time polymerase chain reaction (qPCR). Effect estimates of the association between LTL and prenatal, 1-y childhood air pollution, and proximity to major roads were calculated using multiple linear mixed models with a random cohort effect and adjusted for relevant covariates.

RESULTS

LTL was inversely associated with prenatal and 1-y childhood [Formula: see text] and [Formula: see text] exposures levels. Each standard deviation (SD) increase in prenatal [Formula: see text] was associated with a [Formula: see text] (95% CI: [Formula: see text], [Formula: see text]) change in LTL. Prenatal [Formula: see text] was nonsignificantly associated with LTL ([Formula: see text] per SD increase; 95% CI: [Formula: see text], 0.6). For each SD increment in 1-y childhood [Formula: see text] and [Formula: see text] exposure, LTL shortened by [Formula: see text] (95% CI: [Formula: see text], [Formula: see text]) and [Formula: see text] (95% CI: [Formula: see text], 0.1), respectively. Each doubling in residential distance to nearest major road during childhood was associated with a 1.6% (95% CI: 0.02, 3.1) lengthening in LTL.

CONCLUSION

Lower exposures to air pollution during pregnancy and childhood were associated with longer telomeres in European children at 8 y of age. These results suggest that reductions in traffic-related air pollution may promote molecular longevity, as exemplified by telomere length, from early life onward. https://doi.org/10.1289/EHP4148.

Differences in oxidative potential of black carbon from three combustion emission sources in China

Black carbon (BC) is mainly derived from the incomplete combustion of fossil fuels and biomass, and poses a serious threat to human health. Actual BC from extensive emission sources presents a variety of characteristics that are likely associated with different oxidative potentials (OP) and health endpoints. In the present study, BC derived from three main emission sources (residential coal combustion, biomass burning, and diesel engine exhaust) in China was subjected to physiochemical characterization and its OP was tested using dithiothreitol (DTT) assay. In order to obtain actual BC, the water-soluble part (WS) and organic extract (OE) were eluted successively from PM and the residue particle (RP) were reserved. PM from diesel vehicles had the most effective DTT consumption capacity, followed by PM from biomass and coal burning. And the OP of PM was mostly attributed to its RP part which mainly consisted of metals and BC. SEM/TEM, OC/EC, IC, and ICP-MS measurements confirmed that soluble ions and organic compounds were washed off effectively, while some metals were still retained in the RP part. Thus, the OP of BC was evaluated after adding DTPA to inhibit DTT activity caused by metals in the RP. Significant differences in OP and physiochemical characteristics of BC from the three emission sources were observed. BC from diesel exhaust exhibited the highest DTT activity (15.5 ± 12.6 pmol min^-1 μg^-1) compared to that of BC from biomass (2.5 ± 1.0 pmol min^-1 μg^-1) and coal (1.3 ± 0.5 pmol min^-1 μg^-1) burning. Diesel exhaust BC, which was emitted under the highest combustion temperature, had the smallest size. Coal consumption in China contributes to the highest amount of BC mass emission, but our result indicates that diesel exhaust BC has the greatest OP. An emission inventory based on health impacts is urgently needed to control air pollution sources in the future.

Air Pollution and Dementia: A Systematic Review

BACKGROUND

Both air pollution and dementia are current and growing global issues. There are plausible links between exposure to specific air pollutants and dementia.

OBJECTIVE

To systematically review the evidence base with respect to the relationship between air pollution and later cognitive decline and dementia.

METHODS

Medline, Embase, and PsychINFO® were searched from their inception to September 2018, for publications reporting on longitudinal studies of exposure to air pollution and incident dementia or cognitive decline in adults. Studies reporting on exposure to tobacco smoke including passive smoking or on occupational exposure to pollutants were excluded. Using standard Cochrane methodology, two readers identified relevant abstracts, read full text publications, and extracted data into structured tables from relevant papers, as defined by inclusion and exclusion criteria. Papers were also assessed for validity. CRD42018094299Results:From 3,720 records, 13 papers were found to be relevant, with studies from the USA, Canada, Taiwan, Sweden, and the UK. Study follow-up ranged from one to 15 years. Pollutants examined included particulate matter ≤2.5 μ (PM2.5), nitrogen dioxide (NO2), nitrous oxides (NOx), carbon monoxide (CO), and ozone. Studies varied in their methodology, population selection, assessment of exposure to pollution, and method of cognitive testing. Greater exposure to PM2.5, NO2/NOx, and CO were all associated with increased risk of dementia. The evidence for air pollutant exposure and cognitive decline was more equivocal.

CONCLUSION

Evidence is emerging that greater exposure to airborne pollutants is associated with increased risk of dementia.

Air pollution and telomere length in adults: A systematic review and meta-analysis of observational studies

Telomere length (TL) has been suggested to be a surrogate for cellular ageing, and a record of cumulative inflammation and oxidative stress over life. An emerging body of evidence has associated exposure to air pollution to changes in TL. To date there is no available systematic review of literature on this association. We aimed to systematically review and conduct meta-analysis of published studies on the relationship between air pollution and TL in adults. Electronic databases were systematically searched for available English language studies on the association between air pollution and TL published up to 1 July 2018. Meta-analyses were conducted following MOOSE guidelines. The heterogeneity in the reported associations was assessed using Cochran's Q test and quantified as I² index. Publication bias was assessed using Egger's regression. Our search identified 19 eligible studies including 11 retrospective and eight prospective studies of which, four had excellent quality, ten had good quality and five had fair quality. Meta-analysis result of two studies on long-term exposure to PM_2.5 showed an inverse association between these exposures and TL (for 5 μg/m³ PM_2.5-0.03 95% CI; -0.05, -0.01). Meta-analysis of short-term exposure to PM_2.5 with three studies and Polychlorinated Biphenyls (PCBs) with two studies revealed a direct association between these exposures and TL (0.03 95% CI; 0.02, 0.04 and 0.10 95% CI; 0.06, 0.15 respectively). No statistically significant relationship between exposure to PM₁₀ and polycyclic aromatic hydrocarbons (PAHs) exposure and TL were observed. We observed suggestive evidence for associations between air pollution and TL with potentially different direction of associations for short- and long-term exposures.

Air Pollution and Successful Aging: Recent Evidence and New Perspectives

PURPOSE OF REVIEW

Worldwide demographic changes occurring in a relatively short period have led to a growing interest in the determinants of aging "successfully" and how to promote a healthier old age. As environmental exposures such as ambient air pollution are believed to play a role in the process of aging, they might represent one of the pathways turning potential successful agers to unsuccessful agers. We aimed to critically review the current epidemiological evidence of the associations between chronic exposure to ambient air pollution and several key determinants of unsuccessful aging and to identify specific populations of unsuccessful agers that are potentially more vulnerable to air pollution's health effects.

RECENT FINDINGS

Epidemiologic evidence supports the association between air pollution and increased risk for several major chronic diseases, cognitive impairment, frailty, and decreased longevity-all important determinants of unsuccessful aging-as well as evidence for higher vulnerability among frail populations. However, several methodological shortcomings, including possible publication bias, lack of use of an adequate indicator of unsuccessful aging, limitations in exposure assessment, and residual confounding particularly due to socioeconomic status, hinder inference of causal relationship at this stage. Future studies should use constructs such as frailty index to estimate successful aging, as well as integrate time activity patterns into the exposure assessment metric. Additionally, studies in low- and middle-income countries are needed.

Silica inhalation altered telomere length and gene expression of telomere regulatory proteins in lung tissue of rats

Exposure to silica can cause lung fibrosis and cancer. Identification of molecular targets is important for the intervention and/or prevention of silica-induced lung diseases. Telomeres consist of tandem repeats of DNA sequences at the end of chromosomes, preventing chromosomal fusion and degradation. Regulator of telomere length-1 (RTEL1) and telomerase reverse transcriptase (TERT), genes involved in telomere regulation and function, play important roles in maintaining telomere integrity and length. The goal of this study was to assess the effect of silica inhalation on telomere length and the regulation of RTEL1 and TERT. Lung tissues and blood samples were collected from rats at 4, 32, and 44 wk after exposure to 15 mg/m3 of silica × 6 h/d × 5 d. Controls were exposed to air. At all-time points, RTEL1 expression was significantly decreased in lung tissue of the silica-exposed animals compared to controls. Also, significant increases in telomere length and TERT were observed in the silica group at 4 and 32 wk. Telomere length, RTEL1 and TERT expression may serve as potential biomarkers related to silica exposure and may offer insight into the molecular mechanism of silica-induced lung disease and tumorigeneses.

Cognitive Effects of Air Pollution Exposures and Potential Mechanistic Underpinnings

PURPOSE OF REVIEW

This review sought to address the potential for air pollutants to impair cognition and mechanisms by which that might occur.

RECENT FINDINGS

Air pollution has been associated with deficits in cognitive functions across a wide range of epidemiological studies, both with developmental and adult exposures. Studies in animal models are significantly more limited in number, with somewhat inconsistent findings to date for measures of learning, but show more consistent impairments for short-term memory. Potential contributory mechanisms include oxidative stress/inflammation, altered levels of dopamine and/or glutamate, and changes in synaptic plasticity/structure. Epidemiological studies are consistent with adverse effects of air pollutants on cognition, but additional studies and better phenotypic characterization are needed for animal models, including more precise delineation of specific components of cognition that are affected, as well as definitions of critical exposure periods for such effects and the components of air pollution responsible. This would permit development of more circumscribed hypotheses as to potential behavioral and neurobiological mechanisms.

Oxidative Stress, DNA Methylation, and Telomere Length Changes in Peripheral Blood Mononuclear Cells after Pulmonary Exposure to Metal-Rich Welding Nanoparticles

Welding fume is a complex mixture of different potentially cytotoxic and genotoxic metals, such as chromium (Cr), manganese (Mn), nickel (Ni), and iron (Fe). Documented health effects have been observed in workers exposed to welding fume. The objective of the study was to use an animal model to identify potential biomarkers of epigenetic changes (e.g., changes in telomere length, DNA methylation) in isolated peripheral blood mononuclear cells (PBMCs) after exposure to different welding fumes. Male Sprague-Dawley rats were exposed by intratracheal instillation (ITI) of 2.0 mg/rat of gas metal arc-mild steel (GMA-MS) or manual metal arc-stainless steel (MMA-SS) welding fume. Vehicle controls received sterile saline by ITI. At 4 h, 14 h, 1 d, 3 d, 10 d, and 30 d, bronchoalveolar lavage (BAL) was performed to assess lung inflammation. Whole blood was collected, and PBMCs were isolated. Dihydroethidium (DHE) fluorescence and 4-hydroxylnonenal protein adduct (P-HNE) formation were measured in PBMCs to assess reactive oxygen species (ROS) production. DNA alterations in PBMCs were determined by evaluating changes in DNA methylation and telomere length. Metal composition of the two fumes was different: MMA-SS (41 % Fe, 29 % Cr, 17 % Mn, 3 % Ni) versus GMA-MS (85 % Fe, 14 % Mn). The more soluble and chemically complex MMA-SS sample induced a more persistent and greater inflammatory response compared to the other groups. Also, oxidative stress markers increased at 24 h in the PBMCs recovered from the MMA-SS group compared to other group. No significant differences were observed when comparing DNA methylation between the welding fume and control groups at any of the time points, whereas the MMA-SS sample significantly increased telomere length at 1 and 30 d after a single exposure compared to the other groups. These findings suggest that genotoxic metals in MMA-SS fume (e.g., Cr and Ni), that are absent in the GMA-MS fume, may enhance lung toxicity, as well as induce markers of oxidative stress and increase telomere length in PBMCs. Importantly, the measurement of telomere length in cells isolated from peripheral blood may serve as a potential biomarker of response in the assessment of toxicity associated with welding fumes.