Effects of wood smoke particles from wood-burning stoves on the respiratory health of atopic humans

Polycyclic aromatic hydrocarbons from environmental tobacco smoke and wood stoves dominate in settled house dust from Northwestern Ontario First Nations communities

Rates of respiratory tract infections for children living in remote First Nations communities in the Sioux Lookout Zone in Northwestern Ontario are elevated and associated with poor indoor environmental quality including high exposures to endotoxin and serious dampness and mould damage. The studies also revealed a high prevalence of cigarette smoking and most houses have wood stoves, of variable quality. Depending on structure, polycyclic aromatic hydrocarbons (PAH) are carcinogens, immunotoxins and/or inflammatory mediators that are byproducts of the incomplete combustion of organic materials. Indoor sources of PAHs include tobacco smoke, cooking, and burning wood and/or fossil fuels for house heating. Twelve PAHs were measured in the <300 µm fraction of settled house dust by GC-MS in 59 houses. Nine PAHs were detected in all 59 houses, and median concentrations of individual PAHs measured ranged from 66 to 804 ng/g. PAHs associated with environmental tobacco smoke and with wood smoke dominated the PAH profile. Limiting tobacco smoking indoors and upgrading to low emission airtight wood stoves would improve indoor air quality and the respiratory health of children in this remote region of Ontario.

Effect of prednisone on woodsmoke-induced sputum inflammation in healthy volunteers: A randomized, placebo-controlled pilot study

Background

Inhalation of biomass smoke is associated with adverse respiratory effects in those with chronic pulmonary conditions. There are few published data regarding the effects of anti-inflammatory interventions on these outcomes.

Objective

Our aim was to assess the effects of postexposure prednisone on woodsmoke (WS)-induced sputum neutrophilia.

Methods

We carried out a randomized, placebo-controlled, crossover pilot study assessing the effect of a postexposure dose of 60 mg prednisone on induced sputum inflammation after controlled exposure to WS (500 μg/m3 for 2 hours) in healthy adults who had been identified in a separate screening protocol as being "PMN responsive" to WS. Secondary end points were sputum cytokine level and mucociliary clearance as measured by γ-scintigraphy.

Results

A total of 11 subjects yielded complete data for the primary analysis. At 24 hours after WS exposure, there was a significant increase in sputum percentage of PMNs (%PMN) versus at baseline after placebo (median = 42% [IQR = 31%-53%]) (P = .02) but not after prednisone (median = 32% [IQR = 18%-40%]) (P = .09). Prednisone reduced Δ%PMN at 24 hours, but this difference did not reach statistical significance. However, for the 8 of 11 subjects who were PMN responsive after placebo, prednisone reduced Δ%PMN significantly (P = .05). Prednisone had no significant effects on sputum levels of IL-1β, IL-6, IL-8, or TNF-α. WS exposure tended to reduce mucociliary clearance in the placebo arm but not in the prednisone arm.

Conclusions

Prednisone taken immediately after exposure to WS mitigated short-term increase in sputum %PMN among healthy volunteers selected for their underlying inflammatory responsiveness to WS. Our data support future studies assessing anti-inflammatory interventions and the role of mucus clearance in WS-induced respiratory health effects.

Associations between short-term exposure to airborne carbonaceous particles and mortality: A time-series study in London during 2010-2019

Exposure to ambient particulate matter (PM) has been identified as a major global health concern; however, the importance of specific chemical PM components remains uncertain. Recent studies have suggested that carbonaceous aerosols are important detrimental components of the particle mixture. Using time-series methods, we investigated associations between short-term exposure to carbonaceous particles and mortality in London, UK. Daily counts of non-accidental, respiratory, and cardiovascular deaths were obtained between 2010 and 2019. For the same period, daily concentrations of carbonaceous particles: organic (OC), elemental (EC), wood-burning (WC), total carbon (TC) and equivalent black carbon (eBC) were sourced from two centrally located monitoring sites (one urban-traffic and one urban-background). Generalized additive models were used to estimate the percentage change in mortality risk associated with interquartile range increases in particulate concentrations. Lagged effects up to 3 days were examined. Stratified analyses were conducted by age, sex, and season, separate analyses were also performed by site-type. For non-accidental mortality, positive associations were observed for all particle species at lag1, including statistically significant percentage risk changes in WC (0.51% (95%CI: 0.19%, 0.82%) per IQR (0.68 μg/m3)) and OC (0.45% (95%CI: 0.04%, 0.87% per IQR (2.36 μg/m3)). For respiratory deaths, associations were greatest for particulate concentrations averaged over the current and previous 3 days, with increases in risk of 1.70% (95%CI: 0.64%, 2.77%) for WC and 1.31% (95%CI: -0.08%, 2.71%) for OC. No associations were found with cardiovascular mortality. Results were robust to adjustment for particle mass concentrations. Stratified analyses suggested particulate effects were greatest in the summer and respiratory associations more pronounced in females. Our findings are supportive of an association between carbonaceous particles and non-accidental and respiratory mortality. The strongest evidence of an effect was for WC; this is of significance given the rising popularity of wood-burning for residential space heating and energy production across Europe.

Controlled human exposures: a review and comparison of the health effects of diesel exhaust and wood smoke

One of the most pressing issues in global health is air pollution. Emissions from traffic-related air pollution and biomass burning are two of the most common sources of air pollution. Diesel exhaust (DE) and wood smoke (WS) have been used as models of these pollutant sources in controlled human exposure (CHE) experiments. The aim of this review was to compare the health effects of DE and WS using results obtained from CHE studies. A total of 119 CHE-DE publications and 25 CHE-WS publications were identified for review. CHE studies of DE generally involved shorter exposure durations and lower particulate matter concentrations, and demonstrated more potent dysfunctional outcomes than CHE studies of WS. In the airways, DE induces neutrophilic inflammation and increases airway hyperresponsiveness, but the effects of WS are unclear. There is strong evidence that DE provokes systemic oxidative stress and inflammation, but less evidence exists for WS. Exposure to DE was more prothrombotic than WS. DE generally increased cardiovascular dysfunction, but limited evidence is available for WS. Substantial heterogeneity in experimental methodology limited the comparison between studies. In many areas, outcomes of WS exposures tended to trend in similar directions to those of DE, suggesting that the effects of DE exposure may be useful for inferring possible responses to WS. However, several gaps in the literature were identified, predominantly pertaining to elucidating the effects of WS exposure. Future studies should strongly consider performing head-to-head comparisons between DE and WS using a CHE design to determine the differential effects of these exposures.

The effect of indoor air filtration on biomarkers of inflammation and oxidative stress: a review and meta-analysis of randomized controlled trials

Improvement of indoor air quality is beneficial for human health. However, previous studies have not reached consistent conclusions regarding the effects of indoor air filtration on inflammation and oxidative stress. This study aims to determine the relationship between indoor air filtration and inflammation and oxidative stress biomarkers. We conducted an electronic search that evaluated the association of indoor air filtration with biomarkers of inflammation and oxidative stress in five databases (PubMed, Cochrane Library, EMBASE, Web of Science, and Scopus) from the beginning to April 23, 2023. Outcomes included the following markers: interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), malondialdehyde (MDA), 8-hydroxy-2deoxyguanosine (8-OHdG), and 8-iso-prostaglandinF2α (8-isoPGF2α). We extracted data from the included studies according to the system evaluation and the preferred reporting item for meta-analysis (PRISMA) guidelines and used the Cochrane risk of bias tool to assess bias risk. Our meta-analysis included 15 studies with 678 participants to assess the combined effect size. The meta-analysis demonstrated that indoor air filtration could have a marked reduction in IL-6 (SMD: -0.275, 95% CI: -0.545 to -0.005, p = 0.046) but had no significant effect on other markers of inflammation or oxidative stress. Subgroup analysis results demonstrated a significant reduction in 8-OHdG levels in the subgroup with < 1 day of duration (SMD: -0.916, 95% CI: -1.513 to -0.320; p = 0.003) and using filtrete air filter (SMD: -5.530, 95% CI: -5.962 to -5.099; p < 0.001). Our meta-analysis results depicted that indoor air filtration can significantly reduce levels of inflammation and oxidative stress markers. Considering the adverse effects of air pollution on human health, our study provides powerful evidence for applying indoor air filtration to heavy atmospheric pollution.

Exposure to cooking fumes is associated with perturbations in nasal microbiota composition: A pilot study

Air pollution is one of the leading causes of overall mortality globally. Cooking emissions are a major source of fine particulate matter (PM2.5). However, studies on their potential perturbations on the nasal microbiota as well as their association with respiratory health are lacking. This pilot study aims to assess the environmental air quality among occupational cooks and its associations with nasal microbiota and respiratory symptoms. A total of 20 cooks (exposed) and 20 unexposed controls (mainly office workers), were recruited in Singapore from 2019 to 2021. Information on sociodemographic factors, cooking methods, and self-reported respiratory symptoms were collected using a questionnaire. Personal PM2.5 concentrations and reactive oxygen species (ROS) levels were measured using portable sensors and filter samplers. DNA was extracted from nasal swabs and sequenced using 16s sequencing. Alpha-diversity and beta-diversity were calculated, and between-group variation analysis of species was performed. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between exposure groups and self-reported respiratory symptoms. Higher daily mean PM2.5 (P = 2 × 10-7) and environmental ROS exposure (P = 3.25 × 10-7) were observed in the exposed group. Alpha diversity of the nasal microbiota between the two groups was not significantly different. However, beta diversity was significantly different (unweighted UniFrac P = 1.11 × 10-5, weighted UniFrac P = 5.42 × 10-6) between the two exposure groups. In addition, certain taxa of bacteria were slightly more abundant in the exposed group compared to unexposed controls. There were no significant associations between the exposure groups and self-reported respiratory symptoms. In summary, the exposed group had higher PM2.5 and ROS exposure levels and altered nasal microbiotas as compared to unexposed controls, though further studies are required to replicate these findings in a larger population.

Exercise in bushfire smoke for high performance athletes: A Position Statement from the Australian Institute of SportEndorsed by Australasian College of Sport and Exercise Physicians (ACSEP) and Sport Medicine Australia (SMA)

OBJECTIVES

The frequency of bushfires in Australia is increasing and it is expected bushfire smoke will become a more prevalent phenomenon impacting air quality. The objective of this position statement is to provide guidance to the sport sector regarding exercise in air affected by bushfire smoke.

DESIGN

This is position statement from the Australian Institute of Sport, based on a narrative review of the literature regarding bushfire smoke and its effects on health and exercise performance.

METHODS

A narrative review of scientific publications regarding the effects of bushfire smoke on health and exercise performance.

RESULTS

Bushfire smoke has negative impacts on health and performance. Athletes exercising at high intensity over a prolonged duration will increase their exposure to air pollutants. Athletes with a history of elevated airway responsiveness are likely to be at increased risk of an adverse response to bushfire smoke exposure.

CONCLUSIONS

Athletes, coaches, support staff and sport organisations should monitor air quality (PM2.5 concentration) and make appropriate adjustments to training duration and intensity.

Exposure of children to smoke in clay figures craft in Caruaru, state of Pernambuco, Brazil

Introduction

Alto do Moura, a neighborhood located in the city of Caruaru, state of Pernambuco, Brazil, is known by the production of figurative art in clay, which uses wood as the main fuel in its finishing process. Chronic exposure to toxic gases released in combustion can trigger respiratory atopies.

Objectives

To identify children with respiratory atopies accompanied by the Alto do Moura Family Health Unit and the spatial distribution of furnaces used in the burning of figurative art in clay.

Methods

This was an exploratory, observational, descriptive, cross-sectional study analyzing 596 medical records of children with respiratory atopies living in the aforementioned neighborhood from July 2018 to October 2020. Fifty-two children aged 2 to 10 years were identified. A sociodemographic questionnaire was applied, and the location of furnaces, source of smoke, was mapped. Data were collected using the HC Maps^® application, which stores and generates an electronic spreadsheet for analysis. The prevalence of respiratory atopies and the average distance between children's homes and furnaces were calculated.

Results

A prevalence of respiratory atopies of 8.6% was found in the population studied. Allergic rhinitis was the most common diagnosis, followed by asthma. School-age children were the most affected group, and the average distance between children's homes and furnaces was 76.8 meters.

Conclusions

The presence of environmental pollution resulting from burning wood for making figurative art in clay may be contributing to the occurrence of respiratory atopies in children. Preventive measures, such as using exhaust fans, opening windows, and increasing ventilation, should be encouraged.

Residential Wood Burning and Pulmonary Function in the Agricultural Lung Health Study

BACKGROUND

In low- and middle-income countries, burning biomass indoors for cooking or heating has been associated with poorer lung function. In high-income countries, wood, a form of biomass, is commonly used for heating in rural areas with increasing prevalence. However, in these settings the potential impact of chronic indoor woodsmoke exposure on pulmonary function is little studied.

OBJECTIVE

We evaluated the association of residential wood burning with pulmonary function in case-control study of asthma nested within a U.S. rural cohort.

METHODS

Using sample weighted multivariable linear regression, we estimated associations between some and frequent wood burning, both relative to no exposure, in relation to forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC), their ratio (FEV 1 / FVC ), and fractional exhaled nitric oxide (FeNO). We examined effect modification by smoking or asthma status.

RESULTS

Among all participants and within smoking groups, wood burning was not appreciably related to pulmonary function. However, in individuals with asthma (n = 1,083 ), frequent wood burning was significantly associated with lower FEV 1 [β : - 164 mL ; 95% confidence interval (CI): - 261 , - 66 mL ], FVC (β : - 125 mL ; 95% CI: - 230 , - 20 mL ), and FEV 1 / FVC (β : - 2 % ; 95% CI: - 4 , - 0.4 % ), whereas no appreciable association was seen in individuals without asthma (n = 1,732 ). These differences in association by asthma were statistically significant for FEV 1 (p i n t e r a c t i o n = 0.0044 ) and FEV 1 / FVC (p i n t e r a c t i o n = 0.049 ). Frequent wood burning was also associated with higher FeNO levels in all individuals (n = 2,598 ; β : 0.1  ln ( ppb ) ; 95% CI: 0.02, 0.2), but associations did not differ by asthma or smoking status.

DISCUSSION

Frequent exposure to residential wood burning was associated with a measure of airway inflammation (FeNO) among all individuals and with lower pulmonary function among individuals with asthma. This group may wish to reduce wood burning or consider using air filtration devices. https://doi.org/10.1289/EHP10734.

Health impacts of PM2.5 originating from residential wood combustion in four nordic cities

Background

Residential wood combustion (RWC) is one of the largest sources of fine particles (PM_2.5) in the Nordic cities. The current study aims to calculate the related health effects in four studied city areas in Sweden, Finland, Norway, and Denmark.

Methods

Health impact assessment (HIA) was employed as the methodology to quantify the health burden. Firstly, the RWC induced annual average PM_2.5 concentrations from local sources were estimated with air pollution dispersion modelling. Secondly, the baseline mortality rates were retrieved from the national health registers. Thirdly, the concentration-response function from a previous epidemiological study was applied. For the health impact calculations, the WHO-developed tool AirQ + was used.

Results

Amongst the studied city areas, the local RWC induced PM_2.5 concentration was lowest in the Helsinki Metropolitan Area (population-weighted annual average concentration 0.46 µg m^− 3) and highest in Oslo (2.77 µg m^− 3). Each year, particulate matter attributed to RWC caused around 19 premature deaths in Umeå (95% CI: 8–29), 85 in the Helsinki Metropolitan Area (95% CI: 35–129), 78 in Copenhagen (95% CI: 33–118), and 232 premature deaths in Oslo (95% CI: 97–346). The average loss of life years per premature death case was approximately ten years; however, in the whole population, this reflects on average a decrease in life expectancy by 0.25 (0.10–0.36) years. In terms of the relative contributions in cities, life expectancy will be decreased by 0.10 (95% CI: 0.05–0.16), 0.18 (95% CI: 0.07–0.28), 0.22 (95% CI: 0.09–0.33) and 0.63 (95% CI: 0.26–0.96) years in the Helsinki Metropolitan Area, Umeå, Copenhagen and Oslo respectively. The number of years of life lost was lowest in Umeå (172, 95% CI: 71–260) and highest in Oslo (2458, 95% CI: 1033–3669).

Conclusions

All four Nordic city areas have a substantial amount of domestic heating, and RWC is one of the most significant sources of PM_2.5. This implicates a substantial predicted impact on public health in terms of premature mortality. Thus, several public health measures are needed to reduce the RWC emissions.

Efficiency of Emission Reduction Technologies for Residential Biomass Combustion Appliances: Electrostatic Precipitator and Catalyst

Residential biomass combustion has been pointed out as one of the largest sources of atmospheric pollutants. Rising awareness of the environmental effects of residential biomass combustion emissions boosted the development of different emission reduction devices that are currently available on the market for small-scale appliances. However, detailed studies on the efficiency of these devices in different combustion systems available in Southern European countries are lacking. In this study, two pollution control devices (catalytic converter and electrostatic precipitator) were tested in two different combustion systems (batch mode operated woodstove and automatically fed pellet stove) in order to assess the emission reduction potential of the devices. Pine firewood was used to fuel the woodstove. One commercial brand of pellets and an agricultural fuel (olive pit) were taken for the experiments in the pellet stove. While the efficiency of the electrostatic precipitator in reducing PM10 was only recorded for woodstove emissions (29%), the effect of the catalyst in decreasing gaseous emissions was only visible when applied to the pellet stove flue gas. For wood pellet combustion, reductions of CO and TOC emissions were in the range of 60–62% and 74–77%, respectively. For olive pit combustion, a lower decrease of 59–60% and 64% in CO and TOC emissions, respectively, was recorded.

Acute differences in blood lipids and inflammatory biomarkers following controlled exposures to cookstove air pollution in the STOVES study

Household air pollution is a leading risk factor for morbidity and premature mortality. Numerous cookstoves have been developed to reduce household air pollution, but it is unclear whether such cookstoves meaningfully improve health. In a controlled exposure study with a crossover design, we assessed the effect of pollution emitted from multiple cookstoves on acute differences in blood lipids and inflammatory biomarkers. Participants (n = 48) were assigned to treatment sequences of exposure to air pollution emitted from five cookstoves and a filtered-air control. Blood lipids and inflammatory biomarkers were measured before and 0, 3, and 24 hours after treatments. Many of the measured outcomes had inconsistent results. However, compared to control, intercellular adhesion molecule-1 was higher 3 hours after all treatments, and C-reactive protein and serum amyloid-A were higher 24 hours after the highest treatment. Our results suggest that short-term exposure to cookstove air pollution can increase inflammatory biomarkers within 24 hours.

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.

Indoor home environments of Danish children and the socioeconomic position and health of their parents: A descriptive study

BACKGROUND

Housing and indoor home environments are associated with the risk of infections and asthma in children. To better understand the determinants and characteristics of these environments, we aimed to describe the associations between parental health and socioeconomic position and housing and indoor home environments of children in Denmark, and the clustering of the factors within these environments.

METHODS

Offspring in the Danish National Birth Cohort (DNBC) whose parents responded to the 11-year follow-up were eligible for inclusion. We included complete cases only. Data on the indoor and housing environments (i.e. variables on housing, sources of gaseous and particle pollution, mould and moisture, and pets) were collected through an online questionnaire responded to by a parent. Data on socioeconomic position were obtained through linkage with registry data on maternal education at offspring birth and household equivalized income at offspring birth. Data on parental health were obtained by linking self-reported data from the 11-year follow-up for mother and father with administrative registry data for the mother. We present descriptive statistics and exploratory factor analyses.

RESULTS

A total of 42 723 offspring were included for analyses. The distributions of nearly all indoor and housing environments differed according to educational and income strata, with patterns similar for both education and income. Generally, higher parental educational and income strata had more favorable indoor and housing environments (less secondhand smoking, gas stove use, mould and condensation and higher house ownership, detached house dwellings and newer building age). However, candle use was approximately similar between strata, fireplace use among lower educational and income strata tended towards the extremes (none or daily), and water damage was more common among higher educational and income strata. Parental health was strongly associated with housing and indoor home environment factors - especially parental affective disorders was strongly associated with mould. Four factors were extracted from the exploratory factor analyses, relating primarily in order of extraction to: housing ownership, mould and moisture, candle use and household density.

CONCLUSION

Parental health and socioeconomic position are strongly related to housing and indoor home environments. Additionally, several factors in these environments correlate strongly and cluster together. Observational studies on associations and causal effects of factors in the indoor and housing environments of children on their morbidity, must consider both of these conclusions to arrive at valid estimates and effects.

Technical standards in allergen exposure chambers worldwide - an EAACI Task Force Report

Allergen exposure chambers (AECs) can be used for controlled exposure to allergenic and non-allergenic airborne particles in an enclosed environment, in order to (i) characterize the pathological features of respiratory diseases and (ii) contribute to and accelerate the clinical development of pharmacological treatments and allergen immunotherapy for allergic disease of the respiratory tract (such as allergic rhinitis, allergic rhinoconjunctivitis, and allergic asthma). In the guidelines of the European Medicines Agency for the clinical development of products for allergen immunotherapy (AIT), the role of AECs in determining primary endpoints in dose-finding Phase II trials is emphasized. Although methodologically insulated from the variability of natural pollen exposure, chamber models remain confined to supporting secondary, rather than primary, endpoints in Phase III registration trials. The need for further validation in comparison with field exposure is clearly mandated. On this basis, the European Academy of Allergy and Clinical Immunology (EAACI) initiated a Task Force in 2015 charged to gain a better understanding of how AECs can generate knowledge about respiratory allergies and can contribute to the clinical development of treatments. Researchers working with AECs worldwide were asked to provide technical information in eight sections: (i) dimensions and structure of the AEC, (ii) AEC staff, (iii) airflow, air processing, and operating conditions, (iv) particle dispersal, (v) pollen/particle counting, (vi) safety and non-contamination measures, (vii) procedures for symptom assessments, (viii) tested allergens/substances and validation procedures. On this basis, a minimal set of technical requirements for AECs applied to the field of allergology is proposed.

Acute health effects from exposure to indoor ultrafine particles-A randomized controlled crossover study among young mild asthmatics

Particulate matter is linked to adverse health effects, however, little is known about health effects of particles emitted from typical indoor sources. We examined acute health effects of short-term exposure to emissions from cooking and candles among asthmatics. In a randomized controlled double-blinded crossover study, 36 young non-smoking asthmatics attended three exposure sessions lasting 5 h: (a) air mixed with emissions from cooking (fine particle mass concentration): (PM_2.5 : 96.1 μg/m³ ), (b) air mixed with emissions from candles (PM_2.5 : 89.8 μg/m³ ), and c) clean filtered air (PM_2.5 : 5.8 μg/m³ ). Health effects (spirometry, fractional exhaled Nitric Oxide [FeNO], nasal volume and self-reported symptoms) were evaluated before exposure start, then 5 and 24 h after. During exposures volatile organic compounds (VOCs), particle size distributions, number concentrations and optical properties were measured. Generally, no statistically significant changes were observed in spirometry, FeNO, or nasal volume comparing cooking and candle exposures to clean air. In males, nasal volume and FeNO decreased after exposure to cooking and candles, respectively. Participants reported additional and more pronounced symptoms during exposure to cooking and candles compared to clean air. The results indicate that emissions from cooking and candles exert mild inflammation in asthmatic males and decrease comfort among asthmatic males and females.

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.

Human Inhalation Study with Zinc Oxide: Analysis of Zinc Levels and Biomarkers in Exhaled Breath Condensate

Workers in the zinc processing, for example, welding or hot-dip galvanizing, are exposed to aerosols consisting of particles and gases, including zinc oxide (ZnO), which can affect human health. In this study, we addressed the effects of short-term controlled exposure to nano-sized ZnO on the airway inflammatory markers in healthy volunteers. To this end, we determined the influence of ZnO inhalation on the content of zinc and biomarkers (leukotriene B₄ (LTB₄), peptide leukotrienes (LTC₄/D₄/E₄), 8-iso-PGF_2α, pH, and prostaglandin E₂ (PGE₂)) in exhaled breath condensate (EBC). Sixteen non-smoking subjects (8 females, 8 men) were exposed to filtered air (sham) or ZnO nanoparticles (0.5, 1.0, and 2.0 mg/m³) for 4 h. EBC samples were collected according to specific study design. We found that the peptide leukotrienes were below the limit of quantification (LOQ) in all the EBC samples. ZnO exposure showed no detectable effect on any other parameters investigated when comparing the two groups. The content of Zn in EBC was unaffected by ZnO inhalation at any concentration used. Therefore, we conclude that the evaluation of Zn and biomarker content in EBC would not be a suitable way to assess the exposure to inhaled ZnO.

Mechanistic Implications of Biomass-Derived Particulate Matter for Immunity and Immune Disorders

Particulate matter (PM) is a major and the most harmful component of urban air pollution, which may adversely affect human health. PM exposure has been associated with several human diseases, notably respiratory and cardiovascular diseases. In particular, recent evidence suggests that exposure to biomass-derived PM associates with airway inflammation and can aggravate asthma and other allergic diseases. Defective or excess responsiveness in the immune system regulates distinct pathologies, such as infections, hypersensitivity, and malignancies. Therefore, PM-induced modulation of the immune system is crucial for understanding how it causes these diseases and highlighting key molecular mechanisms that can mitigate the underlying pathologies. Emerging evidence has revealed that immune responses to biomass-derived PM exposure are closely associated with the risk of diverse hypersensitivity disorders, including asthma, allergic rhinitis, atopic dermatitis, and allergen sensitization. Moreover, immunological alteration by PM accounts for increased susceptibility to infectious diseases, such as tuberculosis and coronavirus disease-2019 (COVID-19). Evidence-based understanding of the immunological effects of PM and the molecular machinery would provide novel insights into clinical interventions or prevention against acute and chronic environmental disorders induced by biomass-derived PM.

Controlled human exposures to wood smoke: a synthesis of the evidence

Background

Exposure to particulate matter (PM) from wood combustion represents a global health risk, encompassing diverse exposure sources; indoor exposures due to cooking in developing countries, ambient PM exposures from residential wood combustion in developed countries, and the predicted increasing number of wildfires due to global warming. Although physicochemical properties of the PM, as well as the exposure levels vary considerably between these sources, controlled human exposure studies may provide valuable insight to the harmful effects of wood smoke (WS) exposures in general. However, no previous review has focused specifically on controlled human exposure studies to WS.

Results

The 22 publications identified, resulting from 12 controlled human studies, applied a range of combustion conditions, exposure levels and durations, and exercise components in their WS exposure. A range of airway, cardiovascular and systemic endpoints were assessed, including lung function and heart rate measures, inflammation and oxidative stress. However, the possibility for drawing general conclusions was precluded by the large variation in study design, resulting in differences in physicochemical properties of WS, effective dose, as well as included endpoints and time-points for analysis. Overall, there was most consistency in reported effects for airways, while oxidative stress, systemic inflammation and cardiovascular physiology did not show any clear patterns.

Conclusion

Based on the reviewed controlled human exposure studies, conclusions regarding effects of acute WS exposure on human health are premature. Thus, more carefully conducted human studies are needed. Future studies should pay particular attention to the applied WS exposure, to assure that both exposure levels and PM properties reflect the research question.

Wood smoke black carbon from Indigenous traditional cultural activities in a subarctic Cree community

Indoor concentrations of black carbon (BC) were measured when wood was burned for traditional cultural activities in a study in a Cree community located in subarctic Canada. The study also included an intervention using a propane-fuelled heater to mitigate in situ BC. Mass concentrations of BC were measured in a game-smoking tent for 39 days and in hunting cabins on the west coast of James Bay, Canada, for 8 days. Five-minute averaged BC mass concentration (N = 12,319) data were recorded and assessed using optimised noise-reduction averaging. Mean BC mass concentrations were lower in hunting cabins (mean = 8.25 micrograms per cubic metre (µg m⁻³)) and higher in the game-smoking tent (mean = 15.46 µg m⁻³). However, excessive BC peaks were recorded in the game-smoking tent (maximum = 3076.71 µg m⁻³) when the fire was stoked or loaded. The intervention with the propane heater in a hunting cabin yielded a 90% reduction in measured BC mass concentrations. We do not presume that exposure to BC is of concern in hunting cabins with appropriate wood-burning appliances that are well-sealed and vent outside. In game-smoking tents, we advise that persons take intermittent breaks outside of the tent for fresh air.

Acute changes in lung function following controlled exposure to cookstove air pollution in the subclinical tests of volunteers exposed to smoke (STOVES) study

Background: Exposure to household air pollution generated as a result of cooking and heating is a leading contributor to global disease. The effects of cookstove-generated air pollution on adult lung function, however, remain uncertain.Objectives: We investigated acute responses in lung function following controlled exposures to cookstove-generated air pollution.Methods: We recruited 48 healthy adult volunteers to undergo six two-hour treatments: a filtered-air control and emissions from five different stoves with fine particulate matter (PM_2.5) targets from 10 to 500 µg/m³. Spirometry was conducted prior to exposure and immediately, and three and 24 h post-exposure. Mixed-effect models were used to estimate differences in post-exposure lung function for stove treatments versus control.Results: Immediately post-exposure, lung function was lower compared to the control for the three highest PM_2.5-level stoves. The largest differences were for the fan rocket stove (target 250 µg/m³; forced vital capacity (FVC): -60 mL, 95% confidence interval (95% CI) -135, 15; forced expiratory volume (FEV₁): -51 mL, 95% CI -117, 16; mid-expiratory flow (FEF_25-75): -116 mL/s, 95% CI -239, 8). At 3 h post-exposure, lung function was lower compared to the control for all stove treatments; effects were of similar magnitude for all stoves. At 24 h post-exposure, results were consistent with a null association for FVC and FEV₁; FEF_25-75 was lower relative to the control for the gasifier, fan rocket, and three stone fire.Conclusions: Patterns suggesting short-term decreases in lung function follow from exposure to cookstove air pollution even for stove exposures with low PM_2.5 levels.

Ambient air pollution is associated with airway inflammation in older women: a nested cross-sectional analysis

BACKGROUND

Air pollution is a risk factor for chronic obstructive pulmonary disease (COPD). Fraction of exhaled nitric oxide (FeNO) could be a useful biomarker for health effects of air pollutants. However, there were limited data from older populations with higher prevalence of COPD and other inflammatory conditions.

METHODS

We obtained data from the German Study on the influence of Air pollution on Lung function, Inflammation and Ageing. Spirometry and FeNO were measured by standard techniques. Air pollutant exposures were estimated following the European Study of Cohorts for Air Pollution Effects protocols, and ozone (O3) measured at the closest ground level monitoring station. Multiple linear regression models were fitted to FeNO with each pollutant separately and adjusted for potential confounders.

RESULTS

In 236 women (mean age 74.6 years), geometric mean FeNO was 15.2ppb. Almost a third (n=71, 30.1%) of the women had some chronic inflammatory respiratory condition. A higher FeNO concentration was associated with exposures to fine particles (PM2.5), PM2.5absorbance and respirable particles (PM10). There were no significant associations with PMcoarse, NO2, NOx, O3 or length of major roads within a 1 km buffer. Restricting the analysis to participants with a chronic inflammatory respiratory condition, with or without impaired lung function produced similar findings. Adjusting for diabetes did not materially alter the findings. There were no significant interactions between individual pollutants and asthma or current smoking.

CONCLUSIONS

This study adds to the evidence to reduce ambient PM2.5 concentrations as low as possible to protect the health of the general population.

Respiratory symptoms and associated risk factors among under-five children in Northwest, Ethiopia: community based cross-sectional study

Introduction

Acute respiratory infections are still a major public health problem resulting in morbidity and mortality among under-five children. This study aims to assess the extent of respiratory symptoms and associated risk factors among under-five children in Gondar city, Northwest Ethiopia.

Methods

A community-based cross-sectional study was carried out from February to June 2019. From 792 study participants, data were collected via face to face interviews by using a semi-structured pre-tested questionnaire. Data were entered in Epi Info version 7, then exported to Stata 14.00 for analysis. Binary (Bivariable and Multivariable) logistic regression analysis was used to test the association of explanatory and outcome variables. Variables with p<0.05 were considered as significantly associated with the outcome variable.

Results

The prevalence of respiratory symptoms among under-five children was 37.5% at [95% (CI: 34.3-41)]. Uterine irritability during pregnancy [AOR = 1.89 at 95% CI: (1.11-3.23)], physical exercise during pregnancy [AOR = 0.60 at 95% CI: (0.41-0.89)], using wood and coal for heating [AOR = 2.42 at 95% CI: (1.65-3.53)], cockroaches infestation [AOR = 1.95 at 95% CI: (1.36 – 2.90)], presence of new carpets [AOR = 2.38 at 95% CI: (1.33-4.29)], damp stain [AOR = 2.45 at 95% CI: (1.02-2.69)], opening windows during cooking [AOR = 0.58 at 95% CI: (0.36-0 .93)], living less than 100 m heavy traffic [AOR = 1.94 at 95% CI: (1.16-3.27)], and living less than 100 m (unpaved roads/streets) [AOR= 2.89 at 95% CI: (1.89-4.55)] were significantly associated with respiratory symptoms.

Conclusion

The prevalence of respiratory symptoms among under-five children was relatively high in the study area. Personal and environmental characteristics influencing symptom occurrence were identified. Respiratory symptoms will be minimized by reducing exposure to indoor and outdoor air pollution and enhancing housing quality.

Acute differences in pulse wave velocity, augmentation index, and central pulse pressure following controlled exposures to cookstove air pollution in the Subclinical Tests of Volunteers Exposed to Smoke (SToVES) study

Household air pollution emitted from solid-fuel cookstoves used for domestic cooking is a leading risk factor for morbidity and premature mortality globally. There have been attempts to design and distribute lower emission cookstoves, yet it is unclear if they meaningfully improve health. Using a crossover design, we assessed differences in central aortic hemodynamics and arterial stiffness following controlled exposures to air pollution emitted from five different cookstove technologies compared to a filtered air control. Forty-eight young, healthy participants were assigned to six 2-h controlled treatments of pollution from five different cookstoves and a filtered air control. Each treatment had a target concentration for fine particulate matter: filtered air control = 0 μg/m³, liquefied petroleum gas = 10 μg/m³, gasifier = 35 μg/m³, fan rocket = 100 μg/m³, rocket elbow = 250 μg/m³, three stone fire = 500 μg/m³. Pulse wave velocity (PWV), central augmentation index (AIx), and central pulse pressure (CPP) were measured before and at three time points after each treatment (0, 3, and 24 h). Linear mixed models were used to assess differences in the outcomes for each cookstove treatment compared to control. PWV and CPP were marginally higher 24 h after all cookstove treatments compared to control. For example, PWV was 0.15 m/s higher (95% confidence interval: -0.02, 0.31) and CPP was 0.6 mmHg higher (95% confidence interval: -0.8, 2.1) 24 h after the three stone fire treatment compared to control. The magnitude of the differences compared to control was similar across all cookstove treatments. PWV and CPP had no consistent trends at the other post-treatment time points (0 and 3 h). No consistent trends were observed for AIx at any post-treatment time point. Our findings suggest higher levels of PWV and CPP within 24 h after 2-h controlled treatments of pollution from five different cookstove technologies. The similar magnitude of the differences following each cookstove treatment compared to control may indicate that acute exposures from even the cleanest cookstove technologies can adversely impact these subclinical markers of cardiovascular health, although differences were small and may not be clinically meaningful.

Acute Effects on Blood Pressure Following Controlled Exposure to Cookstove Air Pollution in the STOVES Study

Background

Exposure to air pollution from solid fuel used in residential cookstoves is considered a leading environmental risk factor for disease globally, but evidence for this relationship is largely extrapolated from literature on smoking, secondhand smoke, and ambient fine particulate matter (PM_2.5).

Methods and Results

We conducted a controlled human‐exposure study (STOVES [the Subclinical Tests on Volunteers Exposed to Smoke] Study) to investigate acute responses in blood pressure following exposure to air pollution emissions from cookstove technologies. Forty‐eight healthy adults received 2‐hour exposures to 5 cookstove treatments (three stone fire, rocket elbow, fan rocket elbow, gasifier, and liquefied petroleum gas), spanning PM_2.5 concentrations from 10 to 500 μg/m³, and a filtered air control (0 μg/m³). Thirty minutes after exposure, systolic pressure was lower for the three stone fire treatment (500 μg/m³PM_2.5) compared with the control (−2.3 mm Hg; 95% CI, −4.5 to −0.1) and suggestively lower for the gasifier (35 μg/m³PM_2.5; −1.8 mm Hg; 95% CI, −4.0 to 0.4). No differences were observed at 3 hours after exposure; however, at 24 hours after exposure, mean systolic pressure was 2 to 3 mm Hg higher for all treatments compared with control except for the rocket elbow stove. No differences were observed in diastolic pressure for any time point or treatment.

Conclusions

Short‐term exposure to air pollution from cookstoves can elicit an increase in systolic pressure within 24 hours. This response occurred across a range of stove types and PM_2.5 concentrations, raising concern that even low‐level exposures to cookstove air pollution may pose adverse cardiovascular effects.

Optical properties investigation of the reactions between methylglyoxal and glycine/ammonium sulfate

In recent years, "brown carbon" (BrC), as an important contributor to light absorption and climate forcing as aerosols, has been one of the forefronts in the field of atmospheric research. Aqueous BrC aerosols can be formed through aqueous reactions of methylglyoxal (MG) with nitrogen compounds, such as glycine (Gly) and ammonium sulfate (AS). When exposed to nitrogen compounds for several days, aqueous carbonyl compound MG became absorbent and fluorescent in the ultraviolet and near visible regions, according to UV/Vis and fluorescence spectroscopies. Experiment results showed that optical absorption of two aqueous BrC solutions in the spectral range of 250-480 nm significantly increased with increasing reaction time. After the reactions of MG with Gly and AS, the product absorbance followed the order of MG-Gly>MG-AS. For H₂O₂ oxidation photolysis, the atmospheric aqueous BrC showed the dynamic nature. Reaction kinetic, effective quantum yields and size distribution studies were conducted in the paper. Fluorescence lifetime values of the two BrC solutions were calculated. LC/MS analysis results clearly indicated that complicated organic compounds were formed in the reactions of MG with Gly and AS.

Measuring acute pulmonary responses to occupational wildland fire smoke exposure using exhaled breath condensate

Wildland firefighters are directly exposed to elevated levels of wildland fire (WF) smoke. Although studies demonstrate WF smoke exposure is associated with lung function changes, few studies that use invasive sample collection methods have been conducted to investigate underlying biochemical changes. These methods are also either unrepresentative of the deeper airways or capable of inducing inflammation. In the present study, levels of biomarkers of oxidative stress (8-isoprostane) and pro-inflammatory response (interleukin-6 [IL-6], interleukin-8 [IL-8], C-reactive protein [CRP], and soluble intercellular adhesion molecule-1 [sICAM-1]) were determined in exhaled breath condensate (EBC) samples that were collected from firefighters before, after, and next morning following prescribed burn and regular work shifts. Results show only a marginal cross-shift increase in 8-isoprostane on burn days (.05 < p value < .1), suggesting WF smoke exposure causes mild pulmonary responses.

Exposure to Household Air Pollution from Biomass Cookstoves and Levels of Fractional Exhaled Nitric Oxide (FeNO) among Honduran Women

Household air pollution is estimated to be responsible for nearly three million premature deaths annually. Measuring fractional exhaled nitric oxide (FeNO) may improve the limited understanding of the association of household air pollution and airway inflammation. We evaluated the cross-sectional association of FeNO with exposure to household air pollution (24-h average kitchen and personal fine particulate matter and black carbon; stove type) among 139 women in rural Honduras using traditional stoves or cleaner-burning Justa stoves. We additionally evaluated interaction by age. Results were generally consistent with a null association; we did not observe a consistent pattern for interaction by age. Evidence from ambient and household air pollution regarding FeNO is inconsistent, and may be attributable to differing study populations, exposures, and FeNO measurement procedures (e.g., the flow rate used to measure FeNO).

Toxicity of Urban PM10 and Relation with Tracers of Biomass Burning

The chemical composition of particles varies with space and time and depends on emission sources, atmospheric chemistry and weather conditions. Evidence suggesting that particles differ in toxicity depending on their chemical composition is growing. This in vitro study investigated the biological effects of PM₁₀ in relation to PM-associated chemicals. PM₁₀ was sampled in ambient air at an urban traffic site (Borgerhout) and a rural background location (Houtem) in Flanders (Belgium). To characterize the toxic potential of PM₁₀, airway epithelial cells (Beas-2B cells) were exposed to particles in vitro. Different endpoints were studied including cell damage and death (cell viability) and the induction of interleukin-8 (IL-8). The mutagenic capacity was assessed using the Ames II Mutagenicity Test. The endotoxin levels in the collected samples were analyzed and the oxidative potential (OP) of PM₁₀ particles was evaluated by electron paramagnetic resonance (EPR) spectroscopy. Chemical characteristics of PM₁₀ included tracers for biomass burning (levoglucosan, mannosan and galactosan), elemental and organic carbon (EC/OC) and polycyclic aromatic hydrocarbons (PAHs). Most samples displayed dose-dependent cytotoxicity and IL-8 induction. Spatial and temporal differences in PM₁₀ toxicity were seen. PM₁₀ collected at the urban site was characterized by increased pro-inflammatory and mutagenic activity as well as higher OP and elevated endotoxin levels compared to the background area. Reduced cell viability (−0.46 < r_s < −0.35, p < 0.01) and IL-8 induction (−0.62 < r_s < −0.67, p < 0.01) were associated with all markers for biomass burning, levoglucosan, mannosan and galactosan. Furthermore, direct and indirect mutagenicity were associated with tracers for biomass burning, OC, EC and PAHs. Multiple regression analyses showed levoglucosan to explain 16% and 28% of the variance in direct and indirect mutagenicity, respectively. Markers for biomass burning were associated with altered cellular responses and increased mutagenic activity. These findings may indicate a role of biomass burning in the observed adverse health effect of particulate matter.

Lung function measures following simulated wildland firefighter exposures

Across the world, biomass smoke is a major source of air pollution and is linked with a variety of adverse health effects. This is particularly true in the western U.S. where wood smoke from wildland forest fires are a significant source of PM2.5. Wildland firefighters are impacted as they experience elevated PM2.5 concentrations over extended periods of time, often occurring during physical exertion. Various epidemiological studies have investigated wood smoke impacts on human health, including occupational field exposures experienced by wildland firefighters. As there are numerous challenges in carrying out these field studies, having the ability to research the potential health impacts to this occupational cohort in a controlled setting would provide important information that could be translated to the field setting. To this end, we have carried out a simulated wildland firefighter exposure study in a wood smoke inhalation facility. Utilizing a randomized crossover trial design, we exposed 10 participants once to clean filtered-air, 250 µg/m3, and 500 µg/m3 wood stove-generated wood smoke PM2.5. Participants exercised on a treadmill at an absolute intensity designed to simulate wildland firefighting for 1.5 hr. In addition to measured PM2.5 smoke concentrations, mean levels of CO2, CO, and % relative humidity were continuously monitored and recorded and were representative of occupational "real-world" exposures. Pulmonary function was measured at three time points: before, immediately after, and 1-hr post-exposure. Although there were some reductions in FVC, FEV1, and FVC:FEV1 measures, results of the spirometry testing did not show significant changes in lung function. The development of this wood smoke inhalational facility provides a platform to further address unique research questions related to wood smoke exposures and associated adverse health effects.

Measured Pulmonary and Systemic Markers of Inflammation and Oxidative Stress Following Wildland Firefighter Simulations

OBJECTIVE

A controlled human exposure study was conducted to investigate the impact of inhalational exposures to wood smoke PM2.5 on measured concentrations of airway and systemic inflammatory biomarkers.

METHODS

Mimicking wildland firefighter activities, 10 participants were exposed to three doses of wood smoke PM2.5 (filtered-air, 250 μg/m, and 500 μg/m) while exercising on a treadmill. Exhaled breath condensate (EBC) and blood plasma samples were obtained pre-, immediately post-, and 1-hour postexposure. 8-isoprostane, pH, and myeloperoxidase were measured in EBC, while H2O2, surfactant protein D, and pentraxin-3 (PTX3) were measured in both EBC and plasma.

RESULTS

Only pH, 8-isoprostane, and PTX3 displayed significant changes when comparing pre- and postexposures.

CONCLUSIONS

Markers of inflammation and oxidative stress, including PTX3, pH, and 8-isoprostane in EBC and/or plasma, are sensitive to wood smoke inhalation, with further investigations warranted.

Review of the health effects of wildland fire smoke on wildland firefighters and the public

Each year, the general public and wildland firefighters in the US are exposed to smoke from wildland fires. As part of an effort to characterize health risks of breathing this smoke, a review of the literature was conducted using five major databases, including PubMed and MEDLINE Web of Knowledge, to identify smoke components that present the highest hazard potential, the mechanisms of toxicity, review epidemiological studies for health effects and identify the current gap in knowledge on the health impacts of wildland fire smoke exposure. Respiratory events measured in time series studies as incidences of disease-caused mortality, hospital admissions, emergency room visits and symptoms in asthma and chronic obstructive pulmonary disease patients are the health effects that are most commonly associated with community level exposure to wildland fire smoke. A few recent studies have also determined associations between acute wildland fire smoke exposure and cardiovascular health end-points. These cardiopulmonary effects were mostly observed in association with ambient air concentrations of fine particulate matter (PM2.5). However, research on the health effects of this mixture is currently limited. The health effects of acute exposures beyond susceptible populations and the effects of chronic exposures experienced by the wildland firefighter are largely unknown. Longitudinal studies of wildland firefighters during and/or after the firefighting career could help elucidate some of the unknown health impacts of cumulative exposure to wildland fire smoke, establish occupational exposure limits and help determine the types of exposure controls that may be applicable to the occupation.

Changes in HPBMC markers of immmune function following controlled short-term inhalation exposures of humans to hardwood smoke

Previous studies have shown that complex mixtures containing particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) produce systemic immunotoxicity in animal models following inhalation exposures. While we and others have shown that emissions associated with hardwood smoke (HWS), cigarette smoke and diesel exhaust can suppress the immune systems of animals in vitro and in vivo, there have been few immune function studies on human peripheral blood mononuclear cells (HPBMC) following exposure of humans to HWS. Our work shows that T cells are an important targets of PM and PAH immunotoxicity. These studies were conducted on HPBMC from 14 human volunteers receiving four 2 h nightly exposures to clean air or HWS at a concentration of 500 ug/m(3). We measured anti-CD3/anti-CD28 stimulated T-cell proliferation and HPBMC cytokine production in cell supernatants, including interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), interleukin 8 (IL-8), TH1 cytokines γIFN and IL-2, TH2 cytokine IL-4, Th17 cytokine interleukin 17A (IL-17A) and interleukin 10 (IL-10). We analyzed results using analysis of variance (ANOVA), t-tests and Pearson correlation. Results showed that there was significant variation in the amount of T-cell proliferation observed following polyclonal activation with anti-CD3/anti-CD28 antibodies in both the air and HWS-exposed groups. There was not a significant effect of HWS on T-cell proliferation. However, we did find a strong relationship between the presence of proinflammatory cytokines (IL-1β, TNF-α, IL-6, but not IL-8) and the amount of T-cell proliferation seen in individual donors, demonstrating that brief exposures of humans to HWS can produce changes in systemic immunity that is associated with proinflammatory cytokines.

Physico-chemical properties and biological effects of diesel and biomass particles

Diesel combustion and solid biomass burning are the major sources of ultrafine particles (UFP) in urbanized areas. Cardiovascular and pulmonary diseases, including lung cancer, are possible outcomes of combustion particles exposure, but differences in particles properties seem to influence their biological effects. Here the physico-chemical properties and biological effects of diesel and biomass particles, produced under controlled laboratory conditions, have been characterized. Diesel UFP were sampled from a Euro 4 light duty vehicle without DPF fuelled by commercial diesel and run over a chassis dyno. Biomass UFP were collected from a modern automatic 25 kW boiler propelled by prime quality spruce pellet. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images of both diesel and biomass samples showed aggregates of soot particles, but in biomass samples ash particles were also present. Chemical characterization showed that metals and PAHs total content was higher in diesel samples compared to biomass ones. Human bronchial epithelial (HBEC3) cells were exposed to particles for up to 2 weeks. Changes in the expression of genes involved in xenobiotic metabolism were observed after exposure to both UFP already after 24 h. However, only diesel particles modulated the expression of genes involved in inflammation, oxidative stress and epithelial-to-mesenchymal transition (EMT), increased the release of inflammatory mediators and caused phenotypical alterations, mostly after two weeks of exposure. These results show that diesel UFP affected cellular processes involved in lung and cardiovascular diseases and cancer. Biomass particles exerted low biological activity compared to diesel UFP. This evidence emphasizes that the study of different emission sources contribution to ambient PM toxicity may have a fundamental role in the development of more effective strategies for air quality improvement.

Increase in oxidative stress levels following welding fume inhalation: a controlled human exposure study

BACKGROUND

Tungsten inert gas (TIG) welding represents one of the most widely used metal joining processes in industry. It has been shown to generate a large majority of particles at the nanoscale and to have low mass emission rates when compared to other types of welding. Despite evidence that TIG fume particles may produce reactive oxygen species (ROS), limited data is available for the time course changes of particle-associated oxidative stress in exposed TIG welders.

METHODS

Twenty non-smoking male welding apprentices were exposed to TIG welding fumes for 60 min under controlled, well-ventilated settings. Exhaled breathe condensate (EBC), blood and urine were collected before exposure, immediately after exposure, 1 h and 3 h post exposure. Volunteers participated in a control day to account for oxidative stress fluctuations due to circadian rhythm. Biological liquids were assessed for total reducing capacity, hydrogen peroxide (H2O2), malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) concentrations at each time point. A linear mixed model was used to assess within day and between day differences.

RESULTS

Significant increases in the measured biomarkers were found at 3 h post exposure. At 3 h post exposure, we found a 24 % increase in plasma-H2O2 concentrations ([95%CI: 4 % to 46 %], p = 0.01); a 91 % increase in urinary-H2O2 ([2 % to 258 %], p = 0.04); a 14 % increase in plasma-8-OHdG ([0 % to 31 %], p = 0.049); and a 45 % increase in urinary-8-OHdG ([3 % to 105 %], p = 0.03). Doubling particle number concentration (PNC) exposure was associated with a 22 % increase of plasma-8-OHdG at 3 h post exposure (p = 0.01).

CONCLUSION

A 60-min exposure to TIG welding fume in a controlled, well-ventilated setting induced acute oxidative stress at 3 h post exposure in healthy, non-smoking apprentice welders not chronically exposed to welding fumes. As mass concentration of TIG welding fume particles is very low when compared to other types of welding, it is recommended that additional exposure metrics such as PNC are considered for occupational risk assessments. Our findings highlight the importance of increasing awareness of TIG welding fume toxicity, especially given the realities of welding workplaces that may lack ventilation; and beliefs among interviewed welders that TIG represents a cleaner and safer welding process.

Design and characterization of human exposure to generated sulfate and soot particles in a pilot chamber study

A number of literatures have documented adverse health effects of exposure to fine particulate matter (PM2.5), and secondary sulfate aerosol and black carbon may contribute to health impacts of PM2.5 exposure. We designed an exposure system to generate sulfate and traffic soot particles, and assessed the feasibility of using it for human exposure assessment in a pilot human exposure study. In the designed exposure system, average mass concentrations of generated sulfate and soot particles were 74.19 μg/m3 and 11.54 μg/m3 in the chamber and did not vary significantly during two-hour human exposure sessions. The size ranges of generated sulfate were largely between 20 to 200 nm, whereas those of generated soot particles were in the size ranges of 50 to 200 nm. Following two-hour exposure to generated sulfate and soot particles, we observed significant increases in fractional exhaled NO (FeNO) in young and health subjects. Building on established human exposure system and health response follow-up methods, future full-scale studies focusing on the effects of mixed particulates and individual PM2.5 components would provide data in understanding the underpinning cardio-respiratory outcomes in relation to air pollution mixture exposure.

IMPLICATIONS

Controlled exposure is a useful design to measure the biological responses repeatedly following particulate exposures of target components and set exposure at target levels of health concerns. Our study provides rational and establishes method for future full-scale studies to focus on examining the effects of mixed particulates and individual PM2.5 components.

Health impacts of anthropogenic biomass burning in the developed world

Climate change policies have stimulated a shift towards renewable energy sources such as biomass. The economic crisis of 2008 has also increased the practice of household biomass burning as it is often cheaper than using oil, gas or electricity for heating. As a result, household biomass combustion is becoming an important source of air pollutants in the European Union.This position paper discusses the contribution of biomass combustion to pollution levels in Europe, and the emerging evidence on the adverse health effects of biomass combustion products.Epidemiological studies in the developed world have documented associations between indoor and outdoor exposure to biomass combustion products and a range of adverse health effects. A conservative estimate of the current contribution of biomass smoke to premature mortality in Europe amounts to at least 40 000 deaths per year.We conclude that emissions from current biomass combustion products negatively affect respiratory and, possibly, cardiovascular health in Europe. Biomass combustion emissions, in contrast to emissions from most other sources of air pollution, are increasing. More needs to be done to further document the health effects of biomass combustion in Europe, and to reduce emissions of harmful biomass combustion products to protect public health.

Wood smoke enhances cigarette smoke-induced inflammation by inducing the aryl hydrocarbon receptor repressor in airway epithelial cells

Our previous studies showed that cigarette smokers who are exposed to wood smoke (WS) are at an increased risk for chronic bronchitis and reduced lung function. The present study was undertaken to determine the mechanisms for WS-induced adverse effects. We studied the effect of WS exposure using four cohorts of mice. C57Bl/6 mice were exposed for 4 or 12 weeks to filtered air, to 10 mg/m(3) WS for 2 h/d, to 250 mg/m(3) cigarette smoke (CS) for 6 h/d, or to CS followed by WS (CW). Inflammation was absent in the filtered air and WS groups, but enhanced by twofold in the bronchoalveolar lavage of the CW compared with CS group as measured by neutrophil numbers and levels of the neutrophil chemoattractant, keratinocyte-derived chemokine. The levels of the anti-inflammatory lipoxin, lipoxin A4, were reduced by threefold along with cyclo-oxygenase (COX)-2 and microsomal prostaglandin E synthase (mPGES)-1 in airway epithelial cells and PGE2 levels in the bronchoalveolar lavage of CW compared with CS mice. We replicated, in primary human airway epithelial cells, the changes observed in mice. Immunoprecipitations showed that WS blocked the interaction of aryl hydrocarbon receptor (AHR) with AHR nuclear transporter to reduce expression of COX-2 and mPGES-1 by increasing expression of AHR repressor (AHRR). Collectively, these studies show that exposure to low concentrations of WS enhanced CS-induced inflammation by inducing AHRR expression to suppress AHR, COX-2, and mPGES-1 expression, and levels of PGE2 and lipoxin A4. Therefore, AHRR is a potential therapeutic target for WS-associated exacerbations of CS-induced inflammation.

Systemic effects of wood smoke in a short-term experimental exposure study of atopic volunteers

OBJECTIVE

To investigate whether short-term systemic effects of wood smoke occurred in atopic subjects after experimental wood smoke exposures.

METHODS

A double-blind climate chamber study was conducted on 20 healthy atopic subjects with exposures to filtered air and wood smoke. Pneumoproteins, coagulation and adhesion factors, and cytokines were measured. Heart rate was monitored with pulse monitors. Data were analyzed with mixed models.

RESULTS

Few differences in the outcomes were observed. Plasma tissue factor remained elevated during filtered air exposure (P = 0.002). P-selectin declined independent of exposure (P = 0.0006). Interleukin-6 increased after filtered air (P = 0.03).

CONCLUSIONS

The study confirmed previous observations among nonatopics of limited changes after a 3-hour wood smoke exposure.

Biomarkers of oxidative stress and inflammation after wood smoke exposure in a reconstructed Viking Age house

Exposure to particles from combustion of wood is associated with respiratory symptoms, whereas there is limited knowledge about systemic effects. We investigated effects on systemic inflammation, oxidative stress and DNA damage in humans who lived in a reconstructed Viking Age house, with indoor combustion of wood for heating and cooking. The subjects were exposed to high indoor concentrations of PM2.5 (700-3,600 µg/m(3)), CO (10.7-15.3 ppm) and NO2 (140-154 µg/m(3)) during a 1-week stay. Nevertheless, there were unaltered levels of genotoxicity, determined as DNA strand breaks and formamidopyrimidine DNA glycosylase and oxoguanine DNA glycosylase 1 sensitive sites in peripheral blood mononuclear cells. There were also unaltered expression levels of OGG1, HMOX1, CCL2, IL8, and TNF levels in leukocytes. In serum, there were unaltered levels of C-reactive protein, IL6, IL8, TNF, lactate dehydrogenase, cholesterol, triglycerides, and high-density lipoproteins. The wood smoke exposure was associated with decreased serum levels of sICAM-1, and a tendency to decreased sVCAM-1 levels. There was a minor increase in the levels of circulating monocytes expressing CD31, whereas there were unaltered expression levels of CD11b, CD49d, and CD62L on monocytes after the stay in the house. In conclusion, even a high inhalation exposure to wood smoke was associated with limited systemic effects on markers of oxidative stress, DNA damage, inflammation, and monocyte activation.

Respiratory effects of fine and ultrafine particles from indoor sources--a randomized sham-controlled exposure study of healthy volunteers

Particulate air pollution is linked to impaired respiratory health. We analyzed particle emissions from common indoor sources (candles burning (CB), toasting bread (TB), frying sausages (FS)) and lung function in 55 healthy volunteers (mean age 33.0 years) in a randomized cross-over controlled exposure study. Lung-deposited particle surface area concentration (PSC), size-specific particle number concentration (PNC) up to 10 µm, and particle mass concentration (PMC) of PM₁, PM_2.5 and PM₁₀ were determined during exposure (2 h). FEV₁, FVC and MEF_25%–75% was measured before, 4 h and 24 h after exposure. Wilcoxon-rank sum tests (comparing exposure scenarios) and mixed linear regression using particle concentrations and adjusting for personal characteristics, travel time and transportation means before exposure sessions were performed. While no effect was seen comparing the exposure scenarios and in the unadjusted model, inverse associations were found for PMC from CB and FS in relation to FEV₁ and MEF_25%–75%. with a change in 10 µg/m³ in PM_2.5 from CB being associated with a change in FEV₁ of −19 mL (95%-confidence interval:−43; 5) after 4 h. PMC from TB and PNC of UFP were not associated with lung function changes, but PSC from CB was. Elevated indoor fine particles from certain sources may be associated with small decreases in lung function in healthy adults.

Public health and components of particulate matter: the changing assessment of black carbon

In 2012, the WHO classified diesel emissions as carcinogenic, and its European branch suggested creating a public health standard for airborne black carbon (BC). In 2011, EU researchers found that life expectancy could be extended four to nine times by reducing a unit of BC, vs reducing a unit of PM2.5. Only recently could such determinations be made. Steady improvements in research methodologies now enable such judgments. In this Critical Review, we survey epidemiological and toxicological literature regarding carbonaceous combustion emissions, as research methodologies improved over time. Initially, we focus on studies of BC, diesel, and traffic emissions in the Western countries (where daily urban BC emissions are mainly from diesels). We examine effects of other carbonaceous emissions, e.g., residential burning of biomass and coal without controls, mainly in developing countries. Throughout the 1990s, air pollution epidemiology studies rarely included species not routinely monitored. As additional PM2.5. chemical species, including carbonaceous species, became more widely available after 1999, they were gradually included in epidemiological studies. Pollutant species concentrations which more accurately reflected subject exposure also improved models. Natural "interventions"--reductions in emissions concurrent with fuel changes or increased combustion efficiency; introduction of ventilation in highway tunnels; implementation of electronic toll payment systems--demonstrated health benefits of reducing specific carbon emissions. Toxicology studies provided plausible biological mechanisms by which different PM species, e.g, carbonaceous species, may cause harm, aiding interpretation of epidemiological studies. Our review finds that BC from various sources appears to be causally involved in all-cause, lung cancer and cardiovascular mortality, morbidity, and perhaps adverse birth and nervous system effects. We recommend that the US. EPA rubric for judging possible causality of PM25. mass concentrations, be used to assess which PM2.5. species are most harmful to public health.

IMPLICATIONS

Black carbon (BC) and correlated co-emissions appear causally related with all-cause, cardiovascular, and lung cancer mortality, and perhaps with adverse birth outcomes and central nervous system effects. Such findings are recent, since widespread monitoring for BC is also recent. Helpful epidemiological advances (using many health relevant PM2.5 species in models; using better measurements of subject exposure) have also occurred. "Natural intervention" studies also demonstrate harm from partly combusted carbonaceous emissions. Toxicology studies consistently find biological mechanisms explaining how such emissions can cause these adverse outcomes. A consistent mechanism for judging causality for different PM2.5 species is suggested.

High prevalence of asthma symptoms in Warao Amerindian children in Venezuela is significantly associated with open-fire cooking: a cross-sectional observational study

Background

The International Study on Asthma and Allergies in Childhood (ISAAC) reported a prevalence of asthma symptoms in 17 centers in nine Latin American countries that was similar to prevalence rates reported in non-tropical countries. It has been proposed that the continuous exposure to infectious diseases in rural populations residing in tropical areas leads to a relatively low prevalence of asthma symptoms. As almost a quarter of Latin American people live in rural tropical areas, the encountered high prevalence of asthma symptoms is remarkable. Wood smoke exposure and environmental tobacco smoke have been identified as possible risk factors for having asthma symptoms.

Methods

We performed a cross-sectional observational study from June 1, 2012 to September 30, 2012 in which we interviewed parents and guardians of Warao Amerindian children from Venezuela. Asthma symptoms were defined according to the ISAAC definition as self-reported wheezing in the last 12 months. The associations between wood smoke exposure and environmental tobacco smoke and the prevalence of asthma symptoms were calculated by means of univariate and multivariable logistic regression analyses.

Results

We included 630 children between two and ten years of age. Asthma symptoms were recorded in 164 of these children (26%). The prevalence of asthma symptoms was associated with the cooking method. Children exposed to the smoke produced by cooking on open wood fires were at higher risk of having asthma symptoms compared to children exposed to cooking with gas (AOR 2.12, 95% CI 1.18 - 3.84). Four percent of the children lived in a household where more than ten cigarettes were smoked per day and they had a higher risk of having asthma symptoms compared to children who were not exposed to cigarette smoke (AOR 2.69, 95% CI 1.11 - 6.48).

Conclusion

Our findings suggest that children living in rural settings in a household where wood is used for cooking or where more than ten cigarettes are smoked daily have a higher risk of having asthma symptoms.

Short-term chamber exposure to low doses of two kinds of wood smoke does not induce systemic inflammation, coagulation or oxidative stress in healthy humans

Introduction:

Air pollution increases the risk of cardiovascular diseases. A proposed mechanism is that local airway inflammation leads to systemic inflammation, affecting coagulation and the long-term risk of atherosclerosis. One major source of air pollution is wood burning. Here we investigate whether exposure to two kinds of wood smoke, previously shown to cause airway effects, affects biomarkers of systemic inflammation, coagulation and lipid peroxidation.

Methods:

Thirteen healthy adults were exposed to filtered air followed by two sessions of wood smoke for three hours, one week apart. One session used smoke from the start-up phase of the wood-burning cycle, and the other smoke from the burn-out phase. Mean particle mass concentrations were 295 µg/m³ and 146 µg/m³, and number concentrations were 140 000/cm³ and 100 000/cm³, respectively. Biomarkers were analyzed in samples of blood and urine taken before and several times after exposure. Results after wood smoke exposure were adjusted for exposure to filtered air.

Results:

Markers of systemic inflammation and soluble adhesion molecules did not increase after wood smoke exposure. Effects on markers of coagulation were ambiguous, with minor decreases in fibrinogen and platelet counts and mixed results concerning the coagulation factors VII and VIII. Urinary F₂-isoprostane, a consistent marker of in vivo lipid peroxidation, unexpectedly decreased after wood smoke exposure.

Conclusions:

The effects on biomarkers of inflammation, coagulation and lipid peroxidation do not indicate an increased risk of cardiovascular diseases in healthy adults by short-term exposure to wood smoke at these moderate doses, previously shown to cause airway effects.