Experimental human exposure to air pollutants is essential to understand adverse health effects

Temporal and Spatial Variations of Potentially Toxic Elements in PM10 Collected in Jeddah City, Saudi Arabia

Air pollution causes environmental and health problems around the world. In this study, ambient particulate matter with an aerodynamic diameter equal to or less than 10 microns (PM10) has been collected at three different locations in Jeddah city, Saudi Arabia. The locations are characterized by differences in terms of traffic, residential intensity, industrial, and non-road mobile machinery activities. The monthly and annual mass concentration of the PM10 exceeds the recommended annual limit of the World Health Organization (15 µg/m3) and the European air quality standard (40 µg/m3) at the three locations. The collected PM10 samples as well as a certified reference material of atmospheric particulates (NIST 1678a) were digested in aqua regia using microwave digestion. The quantitative elemental analysis was carried out using inductively coupled plasma mass spectrometry. The variations of the elemental concentration in terms of workdays, weekends, seasons, and annual were determined at the three locations. The spatial and temporal elemental variations were found to be different between the three sites, pointing to local influences that should be further evaluated. The concentration of Cd was found to be high and may cause health problems.

Effects of Ozone on Sickness and Depressive-like Behavioral and Biochemical Phenotypes and Their Regulation by Serum Amyloid A in Mice

Ozone (O₃) is an air pollutant that primarily damages the lungs, but growing evidence supports the idea that O₃ also harms the brain; acute exposure to O₃ has been linked to central nervous system (CNS) symptoms such as depressed mood and sickness behaviors. However, the mechanisms by which O₃ inhalation causes neurobehavioral changes are limited. One hypothesis is that factors in the circulation bridge communication between the lungs and brain following O₃ exposure. In this study, our goals were to characterize neurobehavioral endpoints of O₃ exposure as they relate to markers of systemic and pulmonary inflammation, with a particular focus on serum amyloid A (SAA) and kynurenine as candidate mediators of O₃ behavioral effects. We evaluated O₃-induced dose-, time- and sex-dependent changes in pulmonary inflammation, circulating SAA and kynurenine and its metabolic enzymes, and sickness and depressive-like behaviors in Balb/c and CD-1 mice. We found that 3 parts per million (ppm) O₃, but not 2 or 1 ppm O₃, increased circulating SAA and lung inflammation, which were resolved by 48 h and was worse in females. We also found that indoleamine 2,3-dioxygenase (Ido1) mRNA expression was increased in the brain and spleen 24 h after 3 ppm O₃ and that kynurenine was increased in blood. Sickness and depressive-like behaviors were observed at all O₃ doses (1-3 ppm), suggesting that behavioral responses to O₃ can occur independently of increased SAA or neutrophils in the lungs. Using SAA knockout mice, we found that SAA did not contribute to O₃-induced pulmonary damage or inflammation, systemic increases in kynurenine post-O₃, or depressive-like behavior but did contribute to weight loss. Together, these findings indicate that acute O₃ exposure induces transient symptoms of sickness and depressive-like behaviors that may occur in the presence or absence of overt pulmonary neutrophilia and systemic increases of SAA. SAA does not appear to contribute to pulmonary inflammation induced by O₃, although it may contribute to other aspects of sickness behavior, as reflected by a modest effect on weight loss.

Short-term associations between barbecue fumes and respiratory health in young adults

BACKGROUND

Epidemiological studies have associated biomass combustion with (respiratory) morbidity and mortality, primarily in indoor settings. Barbecuing results in high outdoor air pollution exposures, but the health effects are unknown.

OBJECTIVE

The objective was to investigate short-term changes in respiratory health in healthy adults, associated with exposure to barbecue fumes.

METHODS

16 healthy, adult volunteers were exposed to barbecue smoke in outdoor air in rest during 1.5 h, using a repeated-measures design. Major air pollutants were monitored on-site, including particulate matter <2.5 μm (PM_2.5), particle number concentrations (PNC) and black- and brown carbon. At the same place and time-of-day, subjects participated in a control session, during which they were not exposed to barbecue smoke. Before and immediately after all sessions lung function was measured. Before, immediately after, 4- and 18 h post-sessions nasal expression levels of interleukin (IL)-8, IL6 and Tumor Necrosis Factor alpha (TNFα) were determined in nasal swabs, using quantitative polymerase chain reaction. Associations between major air pollutants, lung function and inflammatory markers were assessed using mixed linear regression models.

RESULTS

High PM_2.5 levels and PNCs were observed during barbecue sessions, with averages ranging from 553 to 1062 μg/m³ and 109,000-463,000 pt/cm³, respectively. Average black- and brown carbon levels ranged between 4.1-13.0 and 5.0-16.2 μg/m³. A 1000 μg/m³ increase in PM_2.5 was associated with 2.37 (0.97, 4.67) and 2.21 (0.98, 5.00) times higher expression of IL8, immediately- and 18 h after exposure. No associations were found between air pollutants and lung function, or the expression of IL6 or TNFα.

DISCUSSION

Short-term exposure to air pollutants emitted from barbecuing was associated with a mild respiratory response in healthy young adults, including prolonged increase in nasal IL8 without a change in lung function and other measured inflammatory markers. The results might indicate prolonged respiratory inflammation, due to short-term exposure to barbecue fumes.

NOx and CO Fluctuations in a Busy Street Canyon

Busy street canyons can have a large flow of vehicles and reduced air exchange and wind speeds at street level, exposing pedestrians to high pollutant concentrations. The airflow tended to move with vehicles along the canyon and the 1-s concentrations of NO, NO2 and CO were highly skewed close to the road and more normally distributed at sensors some metres above the road. The pollutants were more autocorrelated at these elevated sensors, suggesting a less variable concentration away from traffic in the areas of low turbulence. The kerbside concentrations also showed cyclic changes approximating nearby traffic signal timing. The cross-correlation between the concentration measurements suggested that the variation moved at vehicle speed along the canyon, but slower vertically. The concentrations of NOx and CO were slightly higher at wind speeds of under a metre per second. The local ozone concentrations had little effect on the proportion of NOx present as NO2. Pedestrians on the roadside would be unlikely to exceed the USEPA hourly guideline value for NO2 of 100 ppb. Across the campaign period, 100 individual minutes exceeded the guidelines, though the effect of short-term, high-concentration exposures is not well understood. Tram stops at the carriageway divider are places where longer exposures to higher levels of traffic-associated pollutants are possible.

A comparison of alternative selection methods for reporting spirometric parameters in healthy adults

Alternative methods have been proposed to report spirometry indices from test sessions (forced expiratory volume 1 s, FEV₁; forced vital capacity, FVC). However, most use the American and European Societies’ standard (ATS/ERS) which stops sessions once a repeatability threshold is met which may not accurately represent intra-session variability. Our goal was to repeat trials beyond the repeatability threshold and evaluate alternative reporting methods. 130 adults performed spirometry across two visits. Spirometry indices were reported using the ATS/ERS standard and four alternatives. 78 participants (60%) had valid data for all methods and visits. Intra-session coefficients of variation were low (FEV₁: 3.1–3.7%; FVC: 2.3–2.8%). Our four alternative methods yielded FEV₁ and FVC values ≤ 0.08 L different from ATS/ERS standard, which is not clinically meaningful. Intraclass correlation coefficients were ≥ 0.97 indicating consistency across repeated measures. The smallest real differences ranged from FEV₁: 0.20–0.27 L and FVC: 0.18–0.24 L indicating consistency and low measurement error. Overall, all methods for reporting FEV₁ and FVC demonstrated similar measurement error, precision, and stability within- and between-visits. These results suggest that once ATS/ERS repeatability is achieved, which approach is used for reporting spirometric variables may be of low clinical significance in a healthy population.

Concentration-dependent health effects of air pollution in controlled human exposures

BACKGROUND

Air pollution is a leading contributor to premature mortality worldwide and is often represented by particulate matter (PM), a key contributor to its harmful health effects. Concentration-response relationships are useful for quantifying the effects of air pollution in relevant populations and in considering potential effect thresholds. Controlled human exposures can provide data on acute effects and concentration-response relationships that complement epidemiological studies.

OBJECTIVES

We examined PM concentration-responses after controlled human air pollution exposures to examine exposure-response markers, assess effect modifiers, and identify potential effect thresholds.

METHODS

We reviewed primary research from published controlled human exposure studies where responses were reported at multiple target PM concentrations or summarized per unit change in PM to identify concentration-dependent effects.

RESULTS

Of the 191 publications identified through PubMed and supplementary searches, 31 were eligible. Eligible studies collectively represented four pollutant models: concentrated ambient particles, engineered carbon nanoparticles, diesel exhaust, and woodsmoke. We identified concentration-dependent effects on oxidative stress markers, inflammation, and cardiovascular function that overlapped across different pollutants. Metabolic syndrome and glutathione s-transferase mu 1 genotype were identified as potential effect modifiers.

DISCUSSION

Improved understanding of concentration-response relationships is integral to biomonitoring and mitigation of health effects through impact assessment and policy. Although we identified potential concentration-response markers, thresholds, and modifiers, our conclusions on these relationships were limited by a dearth of eligible publications, considerable variability in methodology, and inconsistent reporting standards between studies. More research is required to validate these observations. We recommend that future studies harmonize estimate reporting to facilitate the identification of robust response markers across research and applied settings.

Exposure to total particulate matter obtained from combustion of diesel vehicles (EURO 3 and EURO 5): Effects on the respiratory systems of emphysematous mice

Air pollution has association with chronic obstructive pulmonary disease (COPD) and reduced life expectancy. This study investigated the deleterious effects caused by tobacco smoke and diesel exhaust particles (DEP) from vehicles operating under EURO 3 and EURO 5 standards. Experiments were carried out on C57BL/6 mice divided into six groups: control group, group exposed to cigarette smoke (CS), two groups exposed to DEP (AAE3 and AAE5), and two groups exposed to tobacco smoke and vehicle DEP (CSE3 and CSE5). Results showed that, when compared to AA, groups AAE3 and AAE5 showed changes in respiratory mechanics, and that DEP originating from EURO 5 diesel vehicles was less harmful when compared to DEP originating from EURO 3 diesel vehicles. Analyses of groups CSE3 and CSE5 revealed increased inspiratory capacity and decreased tissue elastance, when compared to their respective controls, suggesting an exacerbation of changes in respiratory system mechanics compatible with COPD development.

Air pollution aggravating COVID-19 lethality? Exploration in Asian cities using statistical models

The present work estimates the increased risk of coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 by establishing the linkage between the mortality rate in the infected cases and the air pollution, specifically Particulate Matters (PM) with aerodynamic diameters ≤ 10 µm and ≤ 2.5 µm. Data related to nine Asian cities are analyzed using statistical approaches, including the analysis of variance and regression model. The present work suggests that there exists a positive correlation between the level of air pollution of a region and the lethality related to COVID-19, indicating air pollution to be an elemental and concealed factor in aggravating the global burden of deaths related to COVID-19. Past exposures to high level of PM_2.5 over a long period, is found to significantly correlate with present COVID-19 mortality per unit reported cases (p < 0.05) compared to PM₁₀, with non-significant correlation (p = 0.118). The finding of the study can help government agencies, health ministries and policymakers globally to take proactive steps by promoting immunity-boosting supplements and appropriate masks to reduce the risks associated with COVID-19 in highly polluted areas.

Guidance to Reduce the Cardiovascular Burden of Ambient Air Pollutants: A Policy Statement From the American Heart Association

In 2010, the American Heart Association published a statement concluding that the existing scientific evidence was consistent with a causal relationship between exposure to fine particulate matter and cardiovascular morbidity and mortality, and that fine particulate matter exposure is a modifiable cardiovascular risk factor. Since the publication of that statement, evidence linking air pollution exposure to cardiovascular health has continued to accumulate and the biological processes underlying these effects have become better understood. This increasingly persuasive evidence necessitates policies to reduce harmful exposures and the need to act even as the scientific evidence base continues to evolve. Policy options to mitigate the adverse health impacts of air pollutants must include the reduction of emissions through action on air quality, vehicle emissions, and renewable portfolio standards, taking into account racial, ethnic, and economic inequality in air pollutant exposure. Policy interventions to improve air quality can also be in alignment with policies that benefit community and transportation infrastructure, sustainable food systems, reduction in climate forcing agents, and reduction in wildfires. The health care sector has a leadership role in adopting policies to contribute to improved environmental air quality as well. There is also potentially significant private sector leadership and industry innovation occurring in the absence of and in addition to public policy action, demonstrating the important role of public-private partnerships. In addition to supporting education and research in this area, the American Heart Association has an important leadership role to encourage and support public policies, private sector innovation, and public-private partnerships to reduce the adverse impact of air pollution on current and future cardiovascular health in the United States.

A framework for investigating the air quality variation characteristics based on the monitoring data: Case study for Beijing during 2013-2016

In this study, an analysis framework based on the regular monitoring data was proposed for investigating the annual/inter-annual air quality variation and the contributions from different factors (i.e., seasons, pollution periods and airflow directions), through a case study in Beijing from 2013 to 2016. The results showed that the annual mean concentrations (MC) of PM_2.5, SO₂, NO₂ and CO had decreased with annual mean ratios of 7.5%, 28.6%, 4.6% and 15.5% from 2013 to 2016, respectively. Among seasons, the MC in winter contributed the largest fractions (25.8%~46.4%) to the annual MC, and the change of MC in summer contributed most to the inter-annual MC variation (IMCV) of PM_2.5 and NO₂. For different pollution periods, gradually increase of frequency of S-1 (PM_2.5, 0~75 μg/m³) made S-1 become the largest contributor (28.8%) to the MC of PM_2.5 in 2016, it had a negative contribution (-13.1%) to the IMCV of PM_2.5; obvious decreases of frequencies of heavily polluted and severely polluted dominated (44.7% and 39.5%) the IMCV of PM_2.5. For different airflow directions, the MC of pollutants under the south airflow had the most significant decrease (22.5%~62.5%), and those decrease contributed most to the IMCV of PM_2.5 (143.3%), SO₂ (72.0%), NO₂ (55.5%) and CO (190.3%); the west airflow had negative influences to the IMCV of PM_2.5, NO₂ and CO. The framework is helpful for further analysis and utilization of the large amounts of monitoring data; and the analysis results can provide scientific supports for the formulation or adjustment of further air pollution mitigation policy.

Environmental Health Sciences in a Translational Research Framework: More than Benches and Bedsides

BACKGROUND

Environmental health scientists may find it challenging to fit the structure of the questions addressed in their discipline into the prevailing paradigm for translational research.

OBJECTIVE

We aim to frame the translational science paradigm to address the stages of scientific discovery, knowledge acquisition, policy development, and evaluation in a manner relevant to the environmental health sciences. Our intention is to characterize differences between environmental health sciences and clinical medicine, and to orient this effort towards public health goals.

DISCUSSION

Translational research is usually understood to have evolved from the bench-to-bedside framework by which basic science transitions to clinical treatment. Although many health-related fields have incorporated the terminology and context of translational science, environmental health research has not always found a clear fit into this paradigm. We describe a translational research framework applicable to environmental health sciences that retains the basic structure that underlies the original bench-to-bedside paradigm. We propose that scientific discovery (T1) in environmental health research frequently occurs through epidemiological or clinical observations. This discovery often involves understanding the potential for human health effects of exposure to a given environmental chemical or chemicals. The practical applications of this discovery evolve through an understanding of exposure-response relationships (T2) and identification of potential interventions to reduce exposure and improve health (T3). These stages of translation require an interdisciplinary partnership between exposure sciences, exposure biology, toxicology, epidemiology, biostatistics, risk assessment, and clinical sciences. Implementation science then plays a crucial role in the development of environmental and public health practice and policy interventions (T4). Outcome evaluation (T5) often takes the form of accountability research, as environmental health scientists work to quantify the costs and benefits of these interventions.

CONCLUSION

We propose an easily visualized framework for translation of environmental health science knowledge-from discovery to public health practice-that reflects the crucial interactions between multiple disciplines in our field. https://doi.org/10.1289/EHP4067.

Pulmonary challenge with carbon nanoparticles induces a dose-dependent increase in circulating leukocytes in healthy males

Background

Inhalation of particulate matter, as part of air pollution, is associated with increased morbidity and mortality. Nanoparticles (< 100 nm) are likely candidates for triggering inflammatory responses and activation of coagulation pathways because of their ability to enter lung cells and pass bronchial mucosa. We tested the hypothesis that bronchial segmental instillation of carbon nanoparticles causes inflammation and activation of coagulation pathways in healthy humans in vivo.

Methods

This was an investigator-initiated, randomized controlled, dose-escalation study in 26 healthy males. Participants received saline (control) in one lung segment and saline (placebo) or carbon nanoparticles 10 μg, 50 μg, or 100 μg in the contra-lateral lung. Six hours later, blood and bronchoalveolar lavage fluid (BALF) was collected for inflammation and coagulation parameters.

Results

There was a significant dose-dependent increase in blood neutrophils (p = 0.046) after challenge with carbon nanoparticles. The individual top-dose of 100 μg showed a significant (p = 0.05) increase in terms of percentage neutrophils in blood as compared to placebo.

Conclusions

This study shows a dose-dependent effect of bronchial segmental challenge with carbon nanoparticles on circulating neutrophils of healthy volunteers. This suggests that nanoparticles in the respiratory tract induce systemic inflammation.

Trial registration

Dutch Trial Register no. 2976. 11 July 2011. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2976

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0463-x) contains supplementary material, which is available to authorized users.

A joint ERS/ATS policy statement: what constitutes an adverse health effect of air pollution? An analytical framework

The American Thoracic Society has previously published statements on what constitutes an adverse effect on health of air pollution in 1985 and 2000. We set out to update and broaden these past statements that focused primarily on effects on the respiratory system. Since then, many studies have documented effects of air pollution on other organ systems, such as on the cardiovascular and central nervous systems. In addition, many new biomarkers of effects have been developed and applied in air pollution studies.This current report seeks to integrate the latest science into a general framework for interpreting the adversity of the human health effects of air pollution. Rather than trying to provide a catalogue of what is and what is not an adverse effect of air pollution, we propose a set of considerations that can be applied in forming judgments of the adversity of not only currently documented, but also emerging and future effects of air pollution on human health. These considerations are illustrated by the inclusion of examples for different types of health effects of air pollution.

A Review of the Effects of Major Atmospheric Pollutants on Pollen Grains, Pollen Content, and Allergenicity

This review summarizes the available data related to the effects of air pollution on pollen grains from different plant species. Several studies carried out either on in situ harvested pollen or on pollen exposed in different places more or less polluted are presented and discussed. The different experimental procedures used to monitor the impact of pollution on pollen grains and on various produced external or internal subparticles are listed. Physicochemical and biological effects of artificial pollution (gaseous and particulate) on pollen from different plants, in different laboratory conditions, are considered. The effects of polluted pollen grains, subparticles, and derived aeroallergens in animal models, in in vitro cell culture, on healthy human and allergic patients are described. Combined effects of atmospheric pollutants and pollen grains-derived biological material on allergic population are specifically discussed. Within the notion of "polluen," some methodological biases are underlined and research tracks in this field are proposed.

Environmental factors in cardiovascular disease

Environmental exposure is an important but underappreciated risk factor contributing to the development and severity of cardiovascular disease (CVD). The heart and vascular system are highly vulnerable to a number of environmental agents--ambient air pollution and the metals arsenic, cadmium, and lead are widespread and the most-extensively studied. Like traditional risk factors, such as smoking and diabetes mellitus, these exposures advance disease and mortality via augmentation or initiation of pathophysiological processes associated with CVD, including blood-pressure control, carbohydrate and lipid metabolism, vascular function, and atherogenesis. Although residence in highly polluted areas is associated with high levels of cardiovascular risk, adverse effects on cardiovascular health also occur at exposure levels below current regulatory standards. Considering the widespread prevalence of exposure, even modest contributions to CVD risk can have a substantial effect on population health. Evidence-based clinical and public-health strategies aimed at reducing environmental exposures from current levels could substantially lower the burden of CVD-related death and disability worldwide.

Interaction effects of temperature and ozone on lung function and markers of systemic inflammation, coagulation, and fibrinolysis: a crossover study of healthy young volunteers

BACKGROUND

Trends in climate suggest that extreme weather events such as heat waves will become more common. High levels of the gaseous pollutant ozone are associated with elevated temperatures. Ozone has been associated with respiratory diseases as well as cardiovascular morbidity and mortality and can reduce lung function and alter systemic markers of fibrinolysis. The interaction between ozone and temperature is unclear.

METHODS

Sixteen healthy volunteers were exposed in a randomized crossover study to 0.3 ppm ozone and clean air for 2 hr at moderate (22°C) temperature and again at an elevated temperature (32.5°C). In each case lung function was performed and blood taken before and immediately after exposure and the next morning.

RESULTS

Ozone exposure at 22°C resulted in a decrease in markers of fibrinolysis the next day. There was a 51.8% net decrease in PAI-1 (plasminogen activator inhibitor-1), a 12.1% net decrease in plasminogen, and a 17.8% net increase in D-dimer. These significantly differed from the response at 32.5°C, where there was a 44.9% (p = 0.002) and a 27.9% (p = 0.001) increase in PAI-1 and plasminogen, respectively, and a 12.5% (p = 0.042) decrease in D-dimer. In contrast, decrements in lung function following ozone exposure were comparable at both moderate and elevated temperatures (forced expiratory volume in 1 sec, -12.4% vs. -7.5%, p > 0.05). No changes in systemic markers of inflammation were observed for either temperature.

CONCLUSION

Ozone-induced systemic but not respiratory effects varied according to temperature. Our study suggests that at moderate temperature ozone may activate the fibrinolytic pathway, while at elevated temperature ozone may impair it. These findings provide a biological basis for the interaction between temperature and ozone on mortality observed in some epidemiologic studies.

Health risk assessment of exposure to TriCresyl Phosphates (TCPs) in aircraft: a commentary

Possible exposure to TriCresyl Phosphates (TCPs) has led to concerns among airline crew members. One isomer, Tri-ortho-Cresyl Phosphate (ToCP) is known to be neurotoxic and exposure to ToCP via contaminated cabin air has been suggested to be associated with the alleged Aerotoxic syndrome. The symptoms associated with Aerotoxic syndrome are diverse, including headaches, loss of balance, numbness and neurobehavioral abnormalities such as emotional instability, depression and cognitive dysfunction. Other ortho-isomers are toxic as well, but the non-ortho isomers are regarded as less toxic. In a collaborative effort to increase insight into the possible association between exposure to TCPs via contaminated cabin air and Aerotoxic syndrome, we performed an exposure- and toxicological risk assessment. Measurements in KLM 737 aircraft have demonstrated the presence of non-ortho isomers in low concentrations, though ToCP and other ortho-isomers could not be detected. Based on this exposure assessment, we established a toxicological risk model that also takes into account human differences in bioactivation and detoxification to derive a hazard quotient. From this model it appears unlikely that the health effects and alleged Aerotoxic syndrome are due to exposure to ToCP. Alternative explanations for the reported symptoms are discussed, but evaluation of the current findings in light of the criteria for occupational disease leads to the conclusion that the Aerotoxic Syndrome cannot be regarded as such. Additional research is thus required to unravel the underlying causes for the reported health complaints.

Controlled exposures to air pollutants and risk of cardiac arrhythmia

BACKGROUND

Epidemiological studies have reported associations between air pollution exposure and increases in cardiovascular morbidity and mortality. Exposure to air pollutants can influence cardiac autonomic tone and reduce heart rate variability, and may increase the risk of cardiac arrhythmias, particularly in susceptible patient groups.

OBJECTIVES

We investigated the incidence of cardiac arrhythmias during and after controlled exposure to air pollutants in healthy volunteers and patients with coronary heart disease.

METHODS

We analyzed data from 13 double-blind randomized crossover studies including 282 participants (140 healthy volunteers and 142 patients with stable coronary heart disease) from whom continuous electrocardiograms were available. The incidence of cardiac arrhythmias was recorded for each exposure and study population.

RESULTS

There were no increases in any cardiac arrhythmia during or after exposure to dilute diesel exhaust, wood smoke, ozone, concentrated ambient particles, engineered carbon nanoparticles, or high ambient levels of air pollution in either healthy volunteers or patients with coronary heart disease.

CONCLUSIONS

Acute controlled exposure to air pollutants did not increase the short-term risk of arrhythmia in participants. Research employing these techniques remains crucial in identifying the important pathophysiological pathways involved in the adverse effects of air pollution, and is vital to inform environmental and public health policy decisions.