Air pollution and asthma: how can a public health concern inform the care of individual patients?

Air pollutants contribute to epithelial barrier dysfunction and allergic diseases

Air pollution is a global problem associated with various health conditions, causing elevated rates of morbidity and mortality. Major sources of air pollutants include industrial emissions, traffic-related pollutants, and household biomass combustion, in addition to indoor pollutants from chemicals and tobacco. Various types of air pollutants originate from both human activities and natural sources. These include particulate matter, pollen, greenhouse gases, and other harmful gases. Air pollution is linked to allergic diseases, including atopic dermatitis, allergic rhinitis, allergic conjunctivitis, food allergy, and bronchial asthma. These pollutants lead to epithelial barrier dysfunction, dysbiosis, and immune dysregulation. In addition, climate change and global warming may contribute to the exacerbation and the development of allergic diseases related to air pollutants. Epigenetic changes associated with air pollutants have also been connected to the onset of allergic diseases. Furthermore, these changes can be passed down through subsequent generations, causing a higher prevalence of allergic diseases in offspring. Modulation of the aryl hydrocarbon receptor could be a valuable strategy for alleviating air pollutant-induced epidermal barrier dysfunction and atopic dermatitis. A more effective approach to preventing allergic diseases triggered by air pollutants is to reduce exposure to them. Implementing public policies aimed at safeguarding individuals from air pollutant exposure may prove to be the most efficient solution. A pressing need exists for global policy initiatives that prioritize efforts to reduce the production of air pollutants.

Environmentally vulnerable or sensitive groups exhibiting varying concerns toward air pollution can drive government response to improve air quality

Air pollution seriously threatens human health, and its consequences are particularly prevalent among environmentally vulnerable or sensitive groups. However, whether the concerns among these groups are different and how they affect air pollution governance remain unclear. Here, we extract 3.8 million haze-related posts from China’s Sina Weibo and analyze the concerns raised by these groups by constructing an air pollution notability index. The results show that protection is the key theme for women aged 20–35 years, while elderly individuals are easily influenced by haze-related product ads yet lack awareness of scientific-based protection. Concerns shared by young individuals are more effective in pressuring the government in cities that experience higher levels of pollution. Concerns shared by women are more effective in cities that experience lower levels of pollution. This study evidences the influence of the public concerns conveyed via social media on air pollution governance in China.

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Online haze concerns from environmentally vulnerable groups can drive air clean

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Government response to their concern plays the key role in improving air quality

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When PM2.5 exceeds 200 μg/m³, their concern shifts from self-protection to governance

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Elders are easily drawn by haze-related ads yet lack aware of scientific protection

The economics of precision health: preventing air pollution-induced exacerbation in asthma

The demonstrable value of precision medicine, in the context of common environmental exposures, has scarcely been explored. This study evaluated the cost effectiveness of a preventive personalised intervention to reduce the adverse effect of air pollution in the context of asthma.

A decision–analytic model was used to conduct a cost-utility analysis of prevention interventions in case of acute exposure to air pollution in mild asthma. Three different strategies, as follows, were compared: no preventive intervention; precision health strategy based on information from genotype testing, followed with treating high-risk patients; and prescribing additional medication to all mild asthmatics as a preventive intervention. The costs and quality-adjusted life years (QALYs) in the base case and alternative scenarios were obtained through probabilistic analysis.

The results showed that the precision prevention intervention (anticipatory intervention for asthmatics, guided by relevant genetic abnormality, in the face of acute air pollution) is a cost-effective strategy compared with no such intervention, with an incremental cost-effectiveness ratio of CAD 49 555 per QALY. Furthermore, this strategy is a dominant strategy compared with an intervention that prescribes medication indiscriminately to all asthmatics.

The incorporation of genomic testing to stratify risk of asthmatics to pollution-driven exacerbations, and then tailoring a preventive intervention accordingly, may be cost effective relative to untailored methods. These results lend plausibility to the use of precision medicine for limiting asthma exacerbation in the context of air pollution and, potentially, other exposures.

Glutathione-S-transferase genotyping to determine the use of preventive asthma medication in the face of air pollution is cost effective in this model. Precision prevention in the setting of common environmental exposures may be used in other contexts.https://bit.ly/35Lab4b

Synergistic Association of House Endotoxin Exposure and Ambient Air Pollution with Asthma Outcomes

Rationale: House endotoxin and ambient air pollution are risk factors for asthma; however, the effects of their coexposure on asthma are not well characterized.Objectives: To examine potential synergistic associations of coexposure to house dust endotoxin and ambient air pollutants with asthma outcomes.Methods: We analyzed data of 6,488 participants in the National Health and Nutrition Examination Survey 2005-2006. Dust from bedding and bedroom floor was analyzed for endotoxin content. The Community Multiscale Air Quality Modeling System (CMAQ) and Downscaler Model data were used to determine annual average particulate matter ≤2.5 μm in aerodynamic diameter (PM_2.5), ozone (O₃), and nitrogen dioxide (NO₂) exposures at participants' residential locations. The associations of the coexposures with asthma outcomes were assessed and tested for synergistic interaction.Measurements and Main Results: In adjusted analysis, PM_2.5 (CMAQ) (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.07-1.18), O₃ (Downscaler Model) (OR, 1.07; 95% CI, 1.02-1.13), and log₁₀ NO₂ (CMAQ) (OR, 3.15; 95% CI, 1.33-7.45) were positively associated with emergency room visits for asthma in the past 12 months. Coexposure to elevated concentrations of house dust endotoxin and PM_2.5 (CMAQ) was synergistically associated with the outcome, increasing the odds by fivefold (OR, 5.01; 95% CI, 2.54-9.87). A synergistic association was also found for coexposure to higher concentrations of endotoxin and NO₂ in children (OR, 3.45; 95% CI, 1.65-7.18).Conclusions: Coexposure to elevated concentrations of residential endotoxin and ambient PM_2.5 in all participants and NO₂ in children is synergistically associated with increased emergency room visits for asthma. Therefore, decreasing exposure to both endotoxin and air pollution may help reduce asthma morbidity.

Impact of traffic-related air pollution on the expression of Platanus orientalis pollen allergens

Air pollutants and their interaction with environmental allergens have been considered as an important reason for the recent increase in the prevalence of allergic diseases. The aim of this study was to investigate the traffic pollution effect, as a stressor, on Platanus orientalis pollen allergens messenger RNA (mRNA) and protein expression. P. orientalis pollen grains were collected along main streets of heavy traffic and from unpolluted sites in Mashhad city, in northeast Iran. The pollen samples were examined by scanning electron microscopy. To assess the abundance of pollen allergens (Pla or 1, Pla or 2, and Pla or 3) from polluted and unpolluted sites, immunoblotting was performed. Moreover, the sequences encoding P. orientalis allergens were amplified using real-time PCR. Scanning electron microscopy showed a number of particles of 150-550 nm on the surface of pollen from polluted sites. Also, protein and gene expression levels of Pla or 1 and Pla or 3 were considerably greater in pollen samples from highly polluted areas than in pollen from unpolluted areas (p < 0.05). In contrast, no statically significant difference in Pla or 2 protein and mRNA expression level was found between samples from the two areas. We found greater expression of allergens involved in plant defense mechanisms (Pla or 1 and Pla or 3) in polluted sites than in unpolluted ones. The high expression of these proteins can lead to an increase in the prevalence of allergic diseases. These findings suggest the necessity of supporting public policies aimed at controlling traffic pollution to improve air quality and prevent the subsequent clinical outcomes and new cases of asthma.

Controlled diesel exhaust and allergen coexposure modulates microRNA and gene expression in humans: Effects on inflammatory lung markers

BACKGROUND

Air pollution's association with asthma may be due to its augmentation of allergenic effects, but the role of microRNA (miRNA) and gene expression in this synergy is unknown.

OBJECTIVE

We sought to determine whether exposure to allergen, exposure to diesel exhaust (DE), or coexposures modulate miRNA, gene expression, or inflammatory pathways and whether these measurements are correlated.

METHODS

Fifteen participants with atopy completed this controlled study of 2 hours of filtered air or DE (300 μg PM_2.5/m³) exposure, followed by saline-controlled segmental bronchial allergen challenge. Gene and miRNA expression in bronchial brushings and lung inflammatory markers were measured 48 hours later, in study arms separated by approximately 4 weeks. Expression of miRNAs, messenger RNAs, and inflammatory markers and their interrelationships were determined using regression.

RESULTS

Robust linear models indicated that DE plus saline and DE plus allergen significantly modulated the highest number of miRNAs and messenger RNAs, respectively, relative to control (filtered air plus saline). In mixed models, allergen exposure modulated (q ≤ 0.2) miRNAs including miR-183-5p, miR-324-5p, and miR-132-3p and genes including NFKBIZ and CDKN1A, but DE did not significantly modify this allergenic effect. Repression of CDKN1A by allergen-induced miR-132-3p may contribute to shedding of bronchial epithelial cells.

CONCLUSIONS

Expression of specific miRNAs and genes associated with bronchial immune responses were significantly modulated by DE or allergen. However, DE did not augment the effect of allergen at 48 hours, suggesting that adjuvancy may be transient or require higher or prolonged exposure. In silico analysis suggested a possible mechanism contributing to epithelial wall damage following allergen exposure.

Vitamin D as an adjunctive therapy in asthma. Part 1: A review of potential mechanisms

Vitamin D deficiency (VDD) is highly prevalent worldwide. The classical role for vitamin D is to regulate calcium absorption form the gastrointestinal tract and influence bone health. Recently vitamin D receptors and vitamin D metabolic enzymes have been discovered in numerous sites systemically supporting diverse extra-skeletal roles of vitamin D, for example in asthmatic disease. Further, VDD and asthma share several common risk factors including high latitude, winter season, industrialization, poor diet, obesity, and dark skin pigmentation. Vitamin D has been demonstrated to possess potent immunomodulatory effects, including effects on T cells and B cells as well as increasing production of antimicrobial peptides (e.g. cathelicidin). This immunomodulation may lead to asthma specific clinical benefits in terms of decreased bacterial/viral infections, altered airway smooth muscle-remodeling and -function as well as modulation of response to standard anti-asthma therapy (e.g. glucocorticoids and immunotherapy). Thus, vitamin D and its deficiency have a number of biological effects that are potentially important in altering the course of disease pathogenesis and severity in asthma. The purpose of this first of a two-part review is to review potential mechanisms whereby altering vitamin D status may influence asthmatic disease.