Endothelial biomarkers (Von willebrand factor, BDCA3, urokinase) as predictors of mortality in COVID-19 patients: cohort study.

BACKGROUND: SARS-CoV-2 is a systemic disease that affects endothelial function and leads to coagulation disorders, increasing the risk of mortality. Blood levels of endothelial biomarkers such as Von Willebrand Factor (VWF), Thrombomodulin or Blood Dendritic Cell Antigen-3 (BDCA3), and uUokinase (uPA) increase in patients with severe disease and can be prognostic indicators for mortality. Therefore, the aim of this study was to determine the effect of VWF, BDCA3, and uPA levels on mortality. METHODS: From May 2020 to January 2021, we studied a prospective cohort of hospitalized adult patients with polymerase chain reaction (PCR)-confirmed COVID-19 with a SaO2 ≤ 93% and a PaO2/FiO2 ratio < 300. In-hospital survival was evaluated from admission to death or to a maximum of 60 days of follow-up with Kaplan-Meier survival curves and Cox proportional hazard models as independent predictor measures of endothelial dysfunction. RESULTS: We recruited a total of 165 subjects (73% men) with a median age of 57.3 ± 12.9 years. The most common comorbidities were obesity (39.7%), hypertension (35.4%) and diabetes (30.3%). Endothelial biomarkers were increased in non-survivors compared to survivors. According to the multivariate Cox proportional hazard model, those with an elevated VWF concentration ≥ 4870 pg/ml had a hazard ratio (HR) of 4.06 (95% CI: 1.32-12.5) compared to those with a lower VWF concentration adjusted for age, cerebrovascular events, enoxaparin dose, lactate dehydrogenase (LDH) level, and bilirubin level. uPA and BDCA3 also increased mortality in patients with levels ≥ 460 pg/ml and ≥ 3600 pg/ml, respectively. CONCLUSION: The risk of mortality in those with elevated levels of endothelial biomarkers was observable in this study.

Microbiota composition in the lower respiratory tract is associated with severity in patients with acute respiratory distress by influenza.

Several factors are associated with the severity of the respiratory disease caused by the influenza virus. Although viral factors are one of the most studied, in recent years the role of the microbiota and co-infections in severe and fatal outcomes has been recognized. However, most of the work has focused on the microbiota of the upper respiratory tract (URT), hindering potential insights from the lower respiratory tract (LRT) that may help to understand the role of the microbiota in Influenza disease. In this work, we characterized the microbiota of the LRT of patients with Influenza A using 16S rRNA sequencing. We tested if patients with different outcomes (deceased/recovered) and use of antibiotics differ in their microbial community composition. We found important differences in the diversity and composition of the microbiota between deceased and recovered patients. In particular, we detected a high abundance of opportunistic pathogens such as Granulicatella, in patients either deceased or with antibiotic treatment. Also, we found antibiotic treatment correlated with lower diversity of microbial communities and with lower probability of survival in Influenza A patients. Altogether, the loss of microbial diversity could generate a disequilibrium in the community, potentially compromising the immune response increasing viral infectivity, promoting the growth of potentially pathogenic bacteria that, together with altered biochemical parameters, can be leading to severe forms of the disease. Overall, the present study gives one of the first characterizations of the diversity and composition of microbial communities in the LRT of Influenza patients and its relationship with clinical variables and disease severity.

Impaired lung function in multiple sclerosis: a single-center observational study in 371 persons.

INTRODUCTION: Abnormal lung function in people with multiple sclerosis (PwMS) could be considered as the result of muscle weakness or MS-specific structural central nervous system (CNS) abnormalities as a precipitant factor for the worsening of motor impairment or cognitive symptoms. METHODS: This is a cross-sectional observational study in PwMS. Forced spirometry was conducted, and normative metrics of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and the relation FEV1/FVC were calculated. Qualitative and quantitative brain magnetic resonance imaging (MRI) examinations were carried out. RESULTS: A total of 371 PwMS were included in the study. Of those, 196 (53%) had RRMS, 92 (25%) SPMS, and 83 (22%) PPMS. Low FVC and FEV1 was present in 16 (8%), 16 (19%), and 23 (25%) of the patients in the RRMS, PPMS, and SPMS, respectively. PwMS with T2-FLAIR lesions involving the corpus callosum (CC) had a significantly higher frequency of abnormally low FVC and FEV1 (OR 3.62; 95% CI 1.33-9.83; p = 0.012) than patients without lesions in that region. This association remained significant in the RRMS group (OR 10.1; 95% CI 1.3-67.8; p 0.031) when the model excluded PPMS and SPMS. According to our study, for every increase of 1 z score of FVC, we observed an increase of 0.25 cm3 of hippocampal volume (ß 0.25; 95% CI 0.03-0.47; p 0.023) and 0.43 cm3 of left hippocampus volume (ß 0.43; 95% CI 0.16-0.71; p 0.002). CONCLUSIONS: We observed an incremental prevalence of abnormally low pulmonary function tests that parallels a sequence from more early relapsing courses to long-standing progressive courses (RRMS to PPMS or SPMS).

Prevalence, attitude, knowledge, and risk perception towards COVID-19 in COPD patients associated to biomass exposure.

Chronic obstructive pulmonary disease (COPD) patients due to biomass exposure (BE-COPD) could be more affected than COPD due to tobacco smoke (TE-COPD) by the coronavirus disease 2019 (COVID-19) pandemic. The aim of this work was to determine the prevalence of COVID-19 in BE-COPD and TE-COPD and if housing conditions, poor attitude, knowledge, and risk perception towards COVID-19, particularly in BE-COPD women, could represent a risk factor for contagion.An 11% prevalence of COVID-19 was found with no significant difference between COPD groups. The BE-COPD group showed poorer socioeconomic status. No significant differences were found to be associated with SARS-CoV-2 infection regarding housing conditions, poor knowledge, attitude, and risk perception towards COVID-19. Living in urban areas and perceiving risk in COVID-19 were significantly associated with increased adherence to sanitary measures and concern of contagion. Around 40% of all patients showed poor risk perception and adherence to sanitary measures towards COVID-19.

Arterial Blood Gases in Normal Subjects at 2240 Meters Above Sea Level: Impact of Age, Gender, and Body Mass Index.

Background: The values of arterial blood gases (ABG) change with altitude above sea level; empirical verification is essential because ventilatory acclimatization varies with ethnicity and a population's adaptation. Objective: The aim of the study was to describe ABG in a healthy population residing at 2,240 meters above sea level, to identify the mean level of alveolar ventilation (PaCO2), and to know whether a progressive increase in PaCO2 occurs with age and the impact of increasing body mass index (BMI). Methods: We conducted a cross-sectional study in a referral center for respiratory diseases in Mexico City. Associations among variables with correlation coefficient and regression models of PaO2, SaO2, and P(A-a)O2 as dependent variables as a function of age, BMI, minute ventilation, or breathing frequency were explored. Results: Two hundred and seventeen healthy subjects were evaluated with a mean age of 40 ± 15 years, mean of the PaO2 was 71 ± 6 mmHg, SaO2 94% ± 1.6%, PaCO2 30.2 ± 3.4 mmHg, HCO3 20 ± 2 mmol/L, BE-2.9 ± 1.9 mmol/L, and the value of pH was 7.43 ± 0.02. In a linear regression, the main results were PaO2 = 77.5-0.16*age (p < 0.0001) and with aging P(A-a)O2 tended to increase 0.12 mmHg/year. PaCO2 in women increased with age by 0.075 mmHg/year (p = 0.0012, PaCO2 =26.3 + 0.075*age). SaO2 and PaO2 decreased significantly in women with higher BMI 0.14% and 0.52 mmHg per kg/m2, (p = 0.004 and 0.002 respectively). Conclusion: Mean PaCO2 was 30.7 mmHg, implying a mean alveolar ventilation of around 30% above that at sea level.

Addiction to Tobacco Smoking and Vaping.

The tobacco epidemic has been one of the biggest public health threats, and smoking is one of the world's largest preventable causes of premature death. An estimated 15.4% of all deaths in the world are attributable to tobacco smoking. The present review aims to describe addiction to tobacco smoking and vaping. Tobacco and vaping devices contain nicotine, a highly addictive drug, which explains why smoking is so prevalent and persistent. Electronic cigarettes are a group of novel nicotine or tobacco products that have rapidly gained popularity in recent years. Electronic cigarette devices allow for the use of other drugs, including THC, while the lax regulation may allow for the introduction of toxic compounds that can lead to acute or subacute toxicity, such as the e-cigarette- or vaping-associated lung injury that has been linked to vitamin E acetate. In addition, regular vapers and heated tobacco devices emit toxins, although at lower concentrations than burned tobacco. However, more and more side effects have been identified. No new effective treatment for nicotine addiction has been developed recently, despite its huge adverse impact on overall health and other outcomes. As for the primary line of medications, the last one started in 2006, the varenicline, demonstrating a low interest in developing new medications against smoking, an unacceptable state of affairs, given the huge impact of smoking on morbidity and mortality.

Knowledge, attitudes, perceptions, and COVID-19 hesitancy in a large public university in Mexico city during the early vaccination rollout.

BACKGROUND: Vaccination against COVID-19 is a primary tool for controlling the pandemic. However, the spread of vaccine hesitancy constitutes a significant threat to reverse progress in preventing the disease. Studies conducted in Mexico have revealed that vaccination intention in Mexico among the general population ranges from 62 to 82%. OBJECTIVE: To know the prevalence of COVID-19 vaccine hesitancy and associated factors among academics, students, and administrative personnel of a public university in Mexico City. METHODS: We administered an online survey investigating sociodemographic aspects, knowledge, attitudes, practices, and acceptance/hesitancy regarding the COVID-19 vaccine. Using generalized linear Poisson models, we analyzed factors associated with vaccine hesitancy, defined as not intending to be vaccinated within the following six months or refusing vaccination. RESULTS: During May and June 2021, we studied 840 people, prevalence of vaccine hesitancy was 6%. Hesitancy was significantly associated with fear of adverse effects, distrust of physician's recommendations, lack of knowledge regarding handwashing, age younger than 40 years, refusal to use face masks, and not having received influenza vaccination during the two previous seasons. CONCLUSIONS: Vaccine hesitancy in this population is low. Furthermore, our results allowed us the identification of characteristics that can improve vaccine promotion.

Affective Comorbidity Associated with Symptoms, Lung Function, and Differences Between Patients with COPD for Biomass and Tobacco Smoke Exposure.

Anxiety and depression are common entities in patients diagnosed with Chronic Obstructive Pulmonary Disease (COPD). This study aimed to determine the prevalence of affective comorbidity (depression and anxiety) associated with lung function, functional capacity, dyspnea, and quality of life; as well as the differences between groups of patients diagnosed with COPD associated with biomass (COPD-BE) and patients with COPD secondary to tobacco (COPD-TS). Comparative cross-sectional observational study. Multiple hierarchical regression models, analysis of variance, and covariance were carried out. A total of 291 COPD patients were evaluated, symptoms of depression were found to be higher in patients with COPD-BE than in patients with COPD-TS (5.3 ± 4.2 versus 4.2 ± 4, 1, p = 0.016), as well as anxiety complications (4.1 ± 3.8 versus 3.8 ± 3.3, p = 0.095), although with anxiety it was not statistically significant, being adjusted for age and FEV1. Patients with COPD-BE had higher prevalence of depression, compared to COPD-TS (41.2% versus 27.7%, p = 0.028). In the multivariate regression models, the variables of dyspnea and quality of life were associated with depression and anxiety, explaining 25% and 24% of the variability, respectively. Depression is higher in COPD-BE patients compared to COPD-TE patients, it is necessary to consider affective comorbidity in routine evaluation and provide a comprehensive intervention to prevent the effects on other clinical conditions of the disease.

Impact of moderate altitude on lung diseases and risk of high altitude illnesses.

A large world population resides at moderate altitudes. In the Valley of Mexico (2240 m above sea level) and for patients with respiratory diseases implies more hypoxemia and clinical deterioration, unless supplementary oxygen is prescribed or patients move to sea level. A group of individuals residing at 2500 or more meters above sea level may develop acute or chronic mountain disease but those conditions may develop at moderate altitudes although less frequently and in predisposed individuals. In the valley of México, at 2200 m above sea level, re-entry pulmonary edema has been reported. The frequency of other altituderelated diseases at moderate altitude, described in skiing resorts, remains to be known in visitors to Mexico City and other cities at similar or higher altitudes. Residents of moderate altitudes inhale deeply the city's air with all pollutants and require more often supplementary oxygen.

Neurologic adverse events among 704,003 first-dose recipients of the BNT162b2 mRNA COVID-19 vaccine in Mexico: A nationwide descriptive study.

mRNA vaccines against SARS-CoV-2 are remarkably effective. Limited information exists about the incidence of adverse events following immunization (AEFI) with their use. We conducted a prospective observational study including data from 704,003 first-doses recipients; 6536 AEFI were reported, of whom 65.1% had at least one neurologic AEFI (non-serious 99.6%). Thirty-three serious events were reported; 17 (51.5%) were neurologic (observed frequency, 2.4/100,000 doses). At the time of writing this report, 16/17 cases had been discharged without deaths. Our data suggest that the BNT162b2 mRNA COVID-19 vaccine is safe; its individual and societal benefits outweigh the low percentage of serious neurologic AEFI. This information should help to dissipate hesitancy towards this new vaccine platform.

Genomic Analysis of Early SARS-CoV-2 Variants Introduced in Mexico.

The coronavirus disease 2019 (COVID-19) pandemic has affected most countries in the world. Studying the evolution and transmission patterns in different countries is crucial to enabling implementation of effective strategies for disease control and prevention. In this work, we present the full genome sequence for 17 SARS-CoV-2 isolates corresponding to the earliest sampled cases in Mexico. Global and local phylogenomics, coupled with mutational analysis, consistently revealed that these viral sequences are distributed within 2 known lineages, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lineage A/G, containing mostly sequences from North America, and lineage B/S, containing mainly sequences from Europe. Based on the exposure history of the cases and on the phylogenomic analysis, we characterized 14 independent introduction events. Additionally, three cases with no travel history were identified. We found evidence that two of these cases represented local transmission cases occurring in Mexico during mid-March 2020, denoting the earliest events described for the country. Within this local transmission cluster, we also identified an H49Y amino acid change in the Spike protein. This mutation represents a homoplasy occurring independently through time and space and may function as a molecular marker to follow any further spread of these viral variants throughout the country. Our results provide a general picture of the SARS-CoV-2 variants introduced at the beginning of the outbreak in Mexico, setting the foundation for future surveillance efforts.IMPORTANCE Understanding the introduction, spread, and establishment of SARS-CoV-2 within distinct human populations as well as the evolution of the pandemics is crucial to implement effective control strategies. In this work, we report that the initial virus strains introduced in Mexico came from Europe and the United States and that the virus was circulating locally in the country as early as mid-March. We also found evidence for early local transmission of strains with a H49Y mutation in the Spike protein, which could be further used as a molecular marker to follow viral spread within the country and the region.

Emergence and spread of the potential variant of interest (VOI) B.1.1.519 of SARS-CoV-2 predominantly present in Mexico.

SARS-CoV-2 variants emerged in late 2020, and at least three variants of concern (B.1.1.7, B.1.351, and P1) have been reported by WHO. These variants have several substitutions in the spike protein that affect receptor binding; they exhibit increased transmissibility and may be associated with reduced vaccine effectiveness. In the present work, we report the identification of a potential variant of interest, harboring the mutations T478K, P681H, and T732A in the spike protein, within the newly named lineage B.1.1.519, that rapidly outcompeted the preexisting variants in Mexico and has been the dominant virus in the country during the first trimester of 2021.

Associated risks of smoking and possible benefits of cessation in Covid-19: a rapid narrative review.

OBJECTIVE: To describe the possible risks associated to smoking in the spread and complications of Covid-19, em-phasizing in the benefits of quitting smoking. MATERIALS AND METHODS: The narrative review methodology and the established process for Cochrane rapid reviews were used. RESULTS: The scientific evidence related to smoking and Covid-19 remains limited. However, there is an already documented trend in cross-sectional, clinical studies and meta-analyses on the increased risk of adverse outcomes with Covid-19 associated with tobacco use. CONCLUSIONS: It is necessary to issue a warning that persons who smoke would have greater risks in the Covid-19 pandemic, which add to the many already known risks of tobacco use. Thus, quitting smoking becomes a relevant preventive measure to better confront SARS-CoV-2.

Smoke exposure from chronic biomass burning induces distinct accumulative systemic inflammatory cytokine alterations compared to tobacco smoking in healthy women.

Long-term exposure to biomass-burning smoke (BS) is associated with chronic obstructive pulmonary disease (COPD), asthma, and other chronic inflammatory lung diseases. BS results from such processes as the burning of wood for indoor cooking and heating, with women and children having the highest exposure rate. This study aimed to analyze the accumulative alterations in cytokine levels associated with BS (from wood) compared to tobacco smoke (TS) in healthy adult women. The levels of 27 cytokines were analyzed in the serum of 100 women, including 40 tobacco smokers/non-exposed to BS (TS+/BS-), 30 never-smokers/exposed to BS (TS-/BS+) and 30 never-smokers/non-exposed to BS (TS-/BS-) as controls, using 27-Plex immunoassay. The chronic BS exposure index was rated at ≥100 h-years, and the tobacco-smoking index was ≥10 pack-years. Compared to TS-/BS-, TS+/BS- had higher levels of IL-2, IL-9, MCP-1, MIP-1ß, and VEGF, while TS-/BS+ showed higher levels of IL-1ra, IL-6, IL-8, Eotaxin, IP-10, RANTES, and VEGF, presenting a distinct inflammatory profile that may favor an eosinophil-derived inflammatory response to BS exposure. Compared to TS+/BS-, TS-/BS+ expressed higher levels of IP-10 and IL-8, but lower levels of IL-2 and MIP-1ß. Gene-disease database analysis showed that altered cytokines in both TS+/BS- and TS-/BS+ are associated with asthma, COPD, lung fibrosis, and lung cancer. In conclusion, chronic BS exposure induces distinct systemic inflammatory cytokine alterations compared to tobacco smokers in healthy women. These findings provide new insights into how long-term exposure to BS affects the inflammatory response-and potentially the health-of adult women.

Arterial blood gases and ventilation at rest by age and sex in an adult Andean population resident at high altitude.

PURPOSE: Arterial blood gases (ABG) are influenced by the altitude above sea level, age and sex. Most studies have been conducted at sea level and in small populations ascending to or residents at very high altitudes. Our objective was to evaluate the ventilation and ABG by age and sex in an Andean population resident at high altitude (2640 m). METHODS: Analytical cross-sectional study was done in healthy volunteers. ABG and minute ventilation (VE) were measured. T test and ANOVA for differences by sex and age, and Pearson test for correlations between age, VE and ABG were performed. RESULTS: We included 374 adults, 55% women from 18 to 83 years and hemoglobin of 15.7 ± 1.6 g/dl. There was a significant decrease in PaO2 and SaO2 and an increase in P(A - a)O2 with age (p < 0.001). Unlike men, with age women had a significant increase in PaCO2 and a higher decrease in PaO2. The correlations between age, the decrease in PaO2 and the increase in PaCO2 were greater in women than in men. The VE adjusted to body surface area decreased with age, but this correlation was significantly higher in women. CONCLUSIONS: In this study, with a considerable number of healthy adults living at high altitude (2640 m), we established the physiological impact of altitude, aging and gender in ABG. The PaO2 and PaCO2 were significantly lower and the hemoglobin values slightly higher than described at sea level. In addition to PaO2 decline with age, there was an age-related increase in PaCO2 in women, associated with a greater reduction of VE.

Screening Tool for Restrictive and Obstructive Ventilatory Abnormalities in a Population-Based Survey.

BACKGROUND: A 6 s spirometry with an inexpensive pocket spirometer efficiently selects individuals for a diagnostic-quality spirometry for airflow limitation, but could also be useful to identify individuals with a restrictive pattern. OBJECTIVES: We evaluated an inexpensive simplified spirometer (chronic obstructive pulmonary disease [COPD]-6) as a screening tool to identify spirometric abnormalities. METHODS: A population-based survey in Mexico City, with 742 participants performing pre- and post-BD spirometry and a three-maneuver 6 s spirometry (pre-BD) with a COPD-6. We evaluated forced expiratory volume in 1 s (FEV1), FEV6, and FEV1/FEV6 from the COPD-6, crude and expressed as the percentage of predicted (%P), to discriminate post-bronchodilator airflow obstruction (FEV1/forced vital capacity [FVC] < 5th percentile) or restriction (FVC or FEV1 <5th percentile with normal FEV1/FVC) through receiver operating characteristics and their area under the curve (AUC). RESULTS: FEV1%P was the best predictor to identify pre- and post-BD ventilatory abnormalities (best cutoff point 87%P, AUC 92% for restrictive pattern, 89% for obstructive pattern, and 91% for any spirometric abnormality). Deriving to clinical spirometry only those with < 87%P (26% of the sample) missed only 12% of spirometric abnormalities most of the latter mild. CONCLUSIONS: An FEV1 < 87%P from a pre-BD 6 s spirometry correctly identified individuals with spirometric ventilatory defects, either obstructive or restrictive.

CHRONIC OBSTRUCTIVE PULMONARY DISEASE: PERSPECTIVES FOR PRIMARY HEALTH CARE.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) has become a major health challenge worldwide due to its increasing incidence and mortality, which have serious repercussions for health-care systems. METHODS: We conducted a review of international efforts to control COPD in primary care. RESULTS: The WHO created the Alma-Ata declaration which established for the first time, access to health care as a human right. This precept led to the implementation of numerous programs including practical approach to Lung Health and variants in several countries; schemes designed to centralize medical care; and resources to improve attention of respiratory diseases by adapting approaches to the health-care needs of local populations. Primary respiratory health care should include actions for timely detection, health education, and targeted treatment, but the challenge for all health systems is to ensure that their programs function adequately, for they still show shortcomings in terms of their application. CONCLUSIONS: We conclude that offering primary health care based on models that combine opportune diagnoses with suitable treatment can positively influence the course of COPD by treating early stages, thus slowing its progression. However, more extensive education and broader dissemination of information are necessary to achieve this goal.

CONTROVERSIES AND LIMITATIONS IN THE DIAGNOSIS OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE.

Chronic obstructive pulmonary disease (COPD) is a major cause of chronic morbidity and mortality worldwide. While the cut-off point to define airflow obstruction has been controversial, it is widely accepted that the spirometry test is vital, as well as performing it after using a bronchodilator. The 6-second spirometry and the forced expiratory volume in 1 second/forced expiratory volume in 6 seconds (FEV1/FEV6) have demonstrated validity for defining obstruction, and it would be advisable to incorporate them in the definitions of obstruction. Another relevant issue is that spirometry with borderline obstruction can vary over time, changing to above or below the cut-off point. Thus, surveillance should be considered over time, repeating the spirometry to have a greater certainty in the diagnosis. The objective of this article was to conduct an in-depth review of the controversies in the diagnosis of COPD. During the past years, COPD definition has been updated in different times; however, it is now considered more as a complex syndrome with systemic participation, requiring a multidimensional assessment, and not only a spirometry.

RESPIRATORY IMPACT OF ELECTRONIC CIGARETTES AND "LOW-RISK" TOBACCO.

Electronic cigarettes, handheld devices that generate an aerosol that may contain nicotine by heating a solution or e-liquid, have been increasingly used especially in the young population. The aerosol's composition is determined by temperature, and by the substances contained in the heated liquid: glycerin, propylene glycol, nicotine in variable concentrations, flavoring agents, and other non-nicotine compounds. >80 compounds (including known toxics, e.g., formaldehyde, acetaldehyde, metallic nanoparticles, and acrolein) have been found in e-liquid and aerosols. Airway irritation, mucus hypersecretion, and inflammatory response, including systemic changes, have been observed after the exposure to e-cigarettes, leading to an increase in respiratory symptoms and changes in respiratory function and the host defense mechanisms. E-cigarette has been linked with an increase of symptoms in individuals with asthma, cystic fibrosis, and chronic obstructive pulmonary disease. One of the major concerns in public health is the rise in e-cigarette experimentation among never-smokers, especially children and adolescents, which leads to nicotine addiction and increases the chances of becoming with time a conventional smoker. There is an urgent need to regulate e-cigarettes and electronic nicotine delivery systems, at least with the same restrictions to those applied to tobacco products, and not to consider them as harmless products.

ERS/ATS workshop report on respiratory health effects of household air pollution.

Exposure to household air pollution (HAP) from solid fuel combustion affects almost half of the world population. Adverse respiratory outcomes such as respiratory infections, impaired lung growth and chronic obstructive pulmonary disease have been linked to HAP exposure. Solid fuel smoke is a heterogeneous mixture of various gases and particulates. Cell culture and animal studies with controlled exposure conditions and genetic homogeneity provide important insights into HAP mechanisms. Impaired bacterial phagocytosis in exposed human alveolar macrophages possibly mediates several HAP-related health effects. Lung pathological findings in HAP-exposed individuals demonstrate greater small airways fibrosis and less emphysema compared with cigarette smokers. Field studies using questionnaires, air pollution monitoring and/or biomarkers are needed to better establish human risks. Some, but not all, studies suggest that improving cookstove efficiency or venting emissions may be associated with reduced respiratory symptoms, lung function decline in women and severe pneumonia in children. Current studies focus on fuel switching, stove technology replacements or upgrades and air filter devices. Several governments have initiated major programmes to accelerate the upgrade from solid fuels to clean fuels, particularly liquid petroleum gas, which provides research opportunities for the respiratory health community.