Indoor air pollution, cookstove quality, and housing characteristics in two Honduran communities

The effect of biomass smoke exposure on quality-of-life among Ugandan patients treated for tuberculosis: A cross-sectional analysis

More than half the global population burns biomass fuels for cooking and home heating, especially in low-middle income countries. This practice is a prominent source of indoor air pollution and has been linked to the development of a variety of cardiopulmonary diseases, including Tuberculosis (TB). The purpose of this cross-sectional study was to investigate the association between current biomass smoke exposure and self-reported quality of life scores in a cohort of previous TB patients in Uganda. We reviewed medical records from six TB clinics from 9/2019-9/2020 and conducted phone interviews to obtain information about biomass smoke exposure. A random sample of these patients were asked to complete three validated quality-of-life surveys including the St. Georges Respiratory Questionnaire (SGRQ), the EuroQol 5 Dimension 3 Level system (EQ-5D-3L) which includes the EuroQol Visual Analog Scale (EQ-VAS), and the Patient Health Questionnaire 9 (PHQ-9). The cohort was divided up into 3 levels based on years of smoke exposure-no-reported smoke exposure (0 years), light exposure (1-19 years), and heavy exposure (20+ years), and independent-samples-Kruskal-Wallis testing was performed with post-hoc pairwise comparison and the Bonferroni correction. The results of this testing indicated significant increases in survey scores for patients with current biomass exposure and a heavy smoke exposure history (20+ years) compared to no reported smoke exposure in the SGRQ activity scores (adj. p = 0.018) and EQ-5D-3L usual activity scores (adj. p = 0.002), indicating worse activity related symptoms. There was a decrease in EQ-VAS scores for heavy (adj. p = 0.007) and light (adj. p = 0.017) exposure groups compared to no reported exposure, indicating lower perceptions of overall health. These results may suggest worse outcomes or baseline health for TB patients exposed to biomass smoke at the time of treatment and recovery, however further research is needed to characterize the effect of indoor air pollution on TB treatment outcomes.

Assessing household fine particulate matter (PM2.5) through measurement and modeling in the Bangladesh cook stove pregnancy cohort study (CSPCS)

Biomass fuel burning is a significant contributor of household fine particulate matter (PM2.5) in the low to middle income countries (LMIC) and assessing PM2.5 levels is essential to investigate exposure-related health effects such as pregnancy outcomes and acute lower respiratory infection in infants. However, measuring household PM2.5 requires significant investments of labor, resources, and time, which limits the ability to conduct health effects studies. It is therefore imperative to leverage lower-cost measurement techniques to develop exposure models coupled with survey information about housing characteristics. Between April 2017 and March 2018, we continuously sampled PM2.5 in three seasonal waves for approximately 48-h (range 46 to 52-h) in 74 rural and semi-urban households among the participants of the Bangladesh Cook Stove Pregnancy Cohort Study (CSPCS). Measurements were taken simultaneously in the kitchen, bedroom, and open space within the household. Structured questionnaires captured household-level information related to the sources of air pollution. With data from two waves, we fit multivariate mixed effect models to estimate 24-h average, cooking time average, daytime and nighttime average PM2.5 in each of the household locations. Households using biomass cookstoves had significantly higher PM2.5 concentrations than those using electricity/liquefied petroleum gas (626 μg/m3 vs. 213 μg/m3). Exposure model performances showed 10-fold cross validated R2 ranging from 0.52 to 0.76 with excellent agreement in independent tests against measured PM2.5 from the third wave of monitoring and ambient PM2.5 from a separate satellite-based model (correlation coefficient, r = 0.82). Significant predictors of household PM2.5 included ambient PM2.5, season, and types of fuel used for cooking. This study demonstrates that we can predict household PM2.5 with moderate to high confidence using ambient PM2.5 and household characteristics. Our results present a framework for estimating household PM2.5 exposures in LMICs, which are often understudied and underrepresented due to resource limitations.

Wood cookstove use is associated with gastric cancer in Central America and mediated by host genetics

Biomass cookstove food preparation is linked to aero-digestive cancers, mediated by ingested and inhaled carcinogens (e.g., heterocyclic amines, and polycyclic aromatic hydrocarbons). We investigated the association between gastric adenocarcinoma, wood cookstove use, H. pylori CagA infection and risk modification by variants in genes that metabolize and affect the internal dose of carcinogens. We conducted a population-based, case-control study (814 incident cases, 1049 controls) in rural Honduras, a high-incidence region with a homogeneous diet and endemic H. pylori infection, primarily with the high-risk CagA genotype. We investigated factors including wood cookstove use, H. pylori CagA serostatus, and 15 variants from 7 metabolizing genes, and the interactions between wood stove use and the genetic variants. Male sex (OR 2.0, 1.6-2.6), age (OR 1.04, 1.03-1.05), wood cookstove use (OR 2.3, 1.6-3.3), and CagA serostatus (OR 3.5, 2.4-5.1) and two SNPs in CYP1B1 (rs1800440 and rs1056836) were independently associated with gastric cancer in multivariate analysis. In the final multivariate model, a highly significant interaction (OR 3.1, 1.2-7.8) was noted between wood cookstove use and the rs1800440 metabolizing genotype, highlighting an important gene-environment interaction. Lifetime wood cookstove use associates with gastric cancer risk in the high-incidence regions of Central America, and the association is dependent on the rs1800440 genotype in CYP1B1. H. pylori CagA infection, wood cookstove use and the rs1800440 genotype, all of which are highly prevalent, informs who is at greatest risk from biomass cookstove use.

Kitchen Characteristics and Practices Associated with Increased PM2.5 Concentration Levels in Zimbabwean Rural Households

Household air pollution (HAP) from biomass fuels significantly contributes to cardio-respiratory morbidity and premature mortality globally. Particulate matter (PM), one of the pollutants generated, remains the most accurate indicator of household air pollution. Determining indoor air concentration levels and factors influencing these levels at the household level is of prime importance, as it objectively guides efforts to reduce household air pollution. This paper describes household factors associated with increased PM_2.5 levels in Zimbabwean rural household kitchens. Our HAP and lung health in women study enrolled 790 women in rural and urban households in Zimbabwe between March 2018 and December 2019. Here, we report data from 148 rural households using solid fuel as the primary source of fuel for cooking and heating and where indoor air samples were collected. Data on kitchen characteristics and practices were collected cross-sectionally using an indoor walk-through survey and a modified interviewer-administered questionnaire. An Air metrics miniVol Sampler was utilized to collect PM_2.5 samples from the 148 kitchens over a 24 h period. To identify the kitchen features and practices that would likely influence PM_2.5 concentration levels, we applied a multiple linear regression model. The measured PM_2.5 ranged from 1.35 μg/m³ to 1940 μg/m³ (IQR: 52.1-472). The PM_2.5 concentration levels in traditional kitchens significantly varied from the townhouse type kitchens, with the median for each kitchen being 291.7 μg/m³ (IQR: 97.2-472.2) and 1.35 μg/m³ (IQR: 1.3-97.2), respectively. The use of wood mixed with other forms of biomass was found to have a statistically significant association (p < 0.001) with increased levels of PM_2.5 concentration. In addition, cooking indoors was strongly associated with higher PM_2.5 concentrations (p = 0.012). Presence of smoke deposits on walls and roofs of the kitchens was significantly associated with increased PM_2.5 concentration levels (p = 0.044). The study found that kitchen type, energy type, cooking place, and smoke deposits were significant predictors of increased PM₂.₅ concentrations in the rural households. Concentrations of PM_2.5 were high as compared to WHO recommended exposure limits for PM_2.5. Our findings highlight the importance of addressing kitchen characteristics and practices associated with elevated PM_2.5 concentrations in settings where resources are limited and switching to cleaner fuels may not be an immediate feasible option.

Effects of household and participant characteristics on personal exposure and kitchen concentration of fine particulate matter and black carbon in rural Honduras

Traditional cooking with solid fuels (biomass, animal dung, charcoals, coal) creates household air pollution that leads to millions of premature deaths and disability worldwide each year. Exposure to household air pollution is highest in low- and middle-income countries. Using data from a stepped-wedge randomized controlled trial of a cookstove intervention among 230 households in Honduras, we analyzed the impact of household and personal variables on repeated 24-h measurements of fine particulate matter (PM2.5) and black carbon (BC) exposure. Six measurements were collected approximately six-months apart over the course of the three-year study. Multivariable mixed models explained 37% of variation in personal PM2.5 exposure and 49% of variation in kitchen PM2.5 concentrations. Additionally, multivariable models explained 37% and 47% of variation in personal and kitchen BC concentrations, respectively. Stove type, season, presence of electricity, primary stove location, kitchen enclosure type, stove use time, and presence of kerosene for lighting were all associated with differences in geometric mean exposures. Stove type explained the most variability of the included variables. In future studies of household air pollution, tracking the cooking behaviors and daily activities of participants, including outdoor exposures, may explain exposure variation beyond the household and personal variables considered here.

Assessing exposure to household air pollution in children under five: A scoping review

Understanding the differences in the approaches used to assess household air pollution (HAP) is crucial for evaluating HAP-related health effects and interpreting the effectiveness of stove-fuel interventions. Our review aims to understand how exposure to HAP from solid fuels was measured in epidemiological studies in children under five. We conducted a search of PubMed, EMBASE, Cochrane Central Register of Controlled Trials, Global Health Library, Web of Science, and CINAHL to identify English-language research articles published between January 1, 2000 and April 30, 2022. Two researchers applied the inclusion and exclusion criteria independently. Study region, type of measurement, study design, health outcomes, and other key characteristics were extracted from each article and analyzed descriptively. Our search strategy yielded 2229 records, of which 185 articles were included. A large proportion was published between 2018 and 2022 (42.1%), applied a cross-sectional study design (47.6%), and took place in low- or lower middle-income countries. Most studies (130/185, 70.3%) assessed HAP using questionnaires/interviews, most frequently posing questions on cooking fuel type, followed by household ventilation and cooking location. Cooking frequency/duration and children's location while cooking was less commonly considered. About 28.6% (53/185) used monitors, but the application of personal portable samplers was limited (particulate matter [PM]: 12/40, 30.0%; carbon monoxide [CO]: 13/34, 38.2%). Few studies used biomarkers or modeling approaches to estimate HAP exposure among children under five. More studies that report household and behavioral characteristics and children's location while cooking, apply personal exposure samplers, and perform biomarker analysis are needed to advance our understandings of HAP exposure among infants and young children, who are particularly susceptible to HAP-related health effects.

A systematic literature review on indoor PM2.5 concentrations and personal exposure in urban residential buildings

Particulate matter with an aerodynamic diameter less than 2.5μm (PM_2.5) is currently a major air pollutant that has been raising public attention. Studies have found that short/long-term exposure to PM_2.5 lead detrimental health effects. Since people in most region of the world spend a large proportion of time in dwellings, personal exposure to PM_2.5 in home microenvironment should be carefully investigated. The objective of this review is to investigate and summary studies in terms of personal exposure to indoor PM_2.5 pollutants from the literature between 2000 and 2021. Factors from both outdoor and indoor environment that have impact on indoor PM_2.5 levels were explicated. Exposure studies were verified relating to individual activity pattern and exposure models. It was found that abundant investigations in terms of personal exposure to indoor PM_2.5 is affected by factors including concentration level, exposure duration and personal diversity. Personal exposure models, including microenvironment model, mathematical model, stochastic model and other simulation models of particle deposition in different regions of human airway are reviewed. Further studies joining indoor measurement and simulation of PM_2.5 concentration and estimation of deposition in human respiratory tract are necessary for individual health protection.

Assessing the Effects of Stove Use Patterns and Kitchen Chimneys on Indoor Air Quality during a Multiyear Cookstove Randomized Control Trial in Rural India

We conducted indoor air quality (IAQ) measurements during a multiyear cookstove randomized control trial in two rural areas in northern and southern India. A total of 1205 days of kitchen PM_2.5 were measured in control and intervention households during six ∼3 month long measurement periods across two study locations. Stoves used included traditional solid fuel (TSF), improved biomass, and liquefied petroleum gas (LPG) models. Intent-to-treat analysis indicates that the intervention reduced average 24 h PM_2.5 and black carbon in only one of the two follow-up measurement periods in both areas, suggesting mixed effectiveness. Average PM_2.5 levels were ∼50% lower in households with LPG (for exclusive LPG use: >75% lower) than in those without LPG. PM_2.5 was 66% lower in households making exclusive use of an improved chimney stove versus a traditional chimney stove and TSF-exclusive kitchens with a built-in chimney had ∼60% lower PM_2.5 than those without a chimney, indicating that kitchen ventilation can be as important as the stove technology in improving IAQ. Diurnal trends in real-time PM_2.5 indicate that kitchen chimneys were especially effective at reducing peak concentrations, which leads to decreases in daily PM_2.5 in these households. Our data demonstrate a clear hierarchy of IAQ improvement in real world, "stove-stacking" households, driven by different stove technologies and kitchen characteristics.

Improving rural women's health in China: cooking with clean energy

It is well known that women bear the greatest burden of health, work time, and labor supply due to gender disparity in many developing countries. In this study, we analyze the health inequality in rural China caused by indoor air pollution from traditional energy use. Specifically, we study the effect of clean energy access on woman health outcome by exploiting a nationwide rollout of clean cooking fuel program in 2014. Based on interviews with rural women in 2014 and 2016, this study analyzes the impact of clean energy use on women's health by using the propensity score matching method with the difference-in-differences model (PSM-DID). We also analyze the heterogeneous health effects of clean energy uptake on rural women with different characteristics. The results show that clean energy applications can significantly improve the health of rural women. The positive health effects are substantial for middle-aged and older women, illiterate women, and those women lived in northeastern China. The results highlight the role of clean energy in reducing gender disparities in health inequality.

Maternal exposure to indoor PM2.5 and associated adverse birth outcomes in low socio-economic households, Durban, South Africa

The association between in utero exposure to indoor PM_2.5 and birth outcomes is not conclusive. We assessed the association between in utero exposure to indoor PM_2.5 , birth weight, gestational age, low birth weight, and/or preterm delivery. Homes of 800 pregnant women were assessed using a structured walkthrough questionnaire. PM_2.5 measurements were undertaken in 300 of the 800 homes for a period of 24 h. Repeated sampling was conducted in 30 of these homes to determine PM_2.5 predictors that can reduce within-and/or between-home variability. A predictive model was used to estimate PM_2.5 levels in unmeasured homes (n = 500). The mean (SD) for PM_2.5 was 37 µg/m³ (29) with a median of 28µg/m³ . The relationship between PM_2.5 exposure, birth weight, gestational age, low birth weight, and preterm delivery was assessed using multivariate linear and logistic regression models. We explored infant sex as a potential effect modifier, by creating an interaction term between PM_2.5 and infant sex. The odds ratio of low birth weight and preterm delivery was 1.75 (95%CI: 1.47, 2.09) and 1.21 (95%CI: 1.06, 1.39), respectively, per interquartile increase (18 µg/m³ ) in PM_2.5 exposure. The reduction in birth weight and gestational age was 75 g (95%CI: 107.89, 53.15) and 0.29 weeks (95%CI: 0.40, 0.19) per interquartile increase in PM_2.5 exposure. Infant sex was an effect modifier for PM_2.5 on birth weight and gestational age, and the reduction in birth weight and gestational age was 103 g (95%CI: 142.98, 64.40) and 0.38 weeks (95% CI: 0.53, 0.23), respectively, for boys, and 54 g (95%CI: 91.78,15.62) and 0.23 weeks (95%CI:0.37, 0.08), respectively, for girls. Exposure to PM_2.5 is associated with adverse pregnancy outcomes. To protect the population during their reproductive period, public health policy should focus on indoor PM_2.5 levels.

Modeling approaches and performance for estimating personal exposure to household air pollution: A case study in Kenya

This study assessed the performance of modeling approaches to estimate personal exposure in Kenyan homes where cooking fuel combustion contributes substantially to household air pollution (HAP). We measured emissions (PM_2.5 , black carbon, CO); household air pollution (PM_2.5 , CO); personal exposure (PM_2.5 , CO); stove use; and behavioral, socioeconomic, and household environmental characteristics (eg, ventilation and kitchen volume). We then applied various modeling approaches: a single-zone model; indirect exposure models, which combine person-location and area-level measurements; and predictive statistical models, including standard linear regression and ensemble machine learning approaches based on a set of predictors such as fuel type, room volume, and others. The single-zone model was reasonably well-correlated with measured kitchen concentrations of PM_2.5 (R²  = 0.45) and CO (R²  = 0.45), but lacked precision. The best performing regression model used a combination of survey-based data and physical measurements (R²  = 0.76) and a root mean-squared error of 85 µg/m³ , and the survey-only-based regression model was able to predict PM2.5 exposures with an R² of 0.51. Of the machine learning algorithms evaluated, extreme gradient boosting performed best, with an R² of 0.57 and RMSE of 98 µg/m³ .

A Comparison of Occupational CO Levels, HbCO, and Lung Functions Between Grill and Non-grill Street Vendors

BACKGROUND

There is a surge increase in grills-fast food outlet in the urban areas that plays an essential role in producing air pollution. Chronic accumulation of carbon monoxide might affect the airway and destroy alveolus as well as correlated with the disturbance of lung function.

OBJECTIVE

The purpose of this study is to compare the occupational CO levels, HbCO, and lung functions between grill and non-grill street vendors.

METHODS

This was an observational analytic study with a case-control design. The subjects were grill street vendors and non-grill street vendors in Medan city who fulfilled several inclusion criteria. The questionnaire was used to determine some characteristics, while smokerlyzer, and ELISA for expiration CO level and blood CO level, spirometer was used to determining lung function. Logistic regression was performed with p-value < 0.05 considered to be significant using SPSS ver 24.0.

RESULTS

A total of 50 subjects enrolled into this study with the majority of subjects in the case group were in red (40%) zone in CO exhaled test with the results in pulmonary function test, predominantly restrictive (56%) and mixed-type (40%) with the mean value of HbCO was 486.16 (ng/mL). Meanwhile, the majority of subjects were green zone with mixed type of lung function disturbance in the control group with 540.15 (ng/mL) as HBCO mean value. Grilled street vendors have a higher level of exhaled CO level (p- value: 0.03) without significant difference in HbCO and lung functions (p-value > 0.05). Age, smoking status, HbCO, and lung function did not significantly affect the CO level (p-value: 0.05).

CONCLUSION

There was a significant difference in exhaled CO level between grill-and non-grill street vendors without significant difference in HbCO and lung functions.

Residential indoor air quality interventions through a social-ecological systems lens: A systematic review

Indoor air quality (IAQ) is an important consideration for health and well-being as people spend most of their time indoors. Multi-disciplinary interest in IAQ is growing, resulting in more empirical research, especially in affordable housing settings, given disproportionate impacts on vulnerable populations. Conceptually, there is little coherency among these case studies; they traverse diverse spatial scales, indoor and outdoor environments, and populations, making it difficult to implement research findings in any given setting. We employ a social-ecological systems (SES) framework to review and categorize existing interventions and other literature findings to elucidate relationships among spatially and otherwise diverse IAQ factors. This perspective is highly attentive to the role of agency, highlighting individual, household, and organizational behaviors and constraints in managing IAQ. When combined with scientific knowledge about the effectiveness of IAQ interventions, this approach favors actionable strategies for reducing the presence of indoor pollutants and personal exposures.

Indoor fine particulate matter and demographic, household, and wood stove characteristics among rural US homes heated with wood fuel

Household heating using wood stoves is common practice in many rural areas of the United States (US) and can lead to elevated concentrations of indoor fine particulate matter (PM_2.5 ). We collected 6-day measures of indoor PM_2.5 during the winter and evaluated household and stove-use characteristics in homes at three rural and diverse study sites. The median indoor PM_2.5 concentration across all homes was 19 µg/m³ , with higher concentrations in Alaska (median = 30, minimum = 4, maximum = 200, n = 10) and Navajo Nation homes (median = 29, minimum = 3, maximum = 105, n = 23) compared with Montana homes (median = 16, minimum = 2, maximum = 139, n = 59). Households that had not cleaned the chimney within the past year had 65% higher geometric mean PM_2.5 compared to those with chimney cleaned within 6 months (95% confidence interval [CI]: -1, 170). Based on a novel wood stove grading method, homes with low-quality and medium-quality stoves had substantially higher PM_2.5 compared to homes with higher-quality stoves (186% higher [95% CI: 32, 519] and 161% higher; [95% CI:27, 434], respectively). Our findings highlight the need for, and complex nature of, regionally appropriate interventions to reduce indoor air pollution in rural wood-burning regions. Higher-quality stoves and behavioral practices such as regular chimney cleaning may help improve indoor air quality in such homes.

Maternal exposure to cooking smoke and risk of low birth weight in India

Over half of the households in India are using unclean cooking fuels (UCF) and exposed to harmful pollutants that has adverse effects on weight of new born baby. Though studies examined the contextual determinants of birth weight, the association of cooking practices and kitchen location with low birth weight (LBW) is limited in India. This paper investigates the comprehensive effects of household air pollution (HAP) on LBW, mean birth weight (MBW) and birth size in India. Data from 93,721 full-term singleton births from the fourth round of National Family Health Survey, conducted during 2015-16 is used in the analyses. Binary logistic and linear regression methods were used to assess the effect of cooking practices on the outcome variables. Children born in households using clean cooking fuels (CCF) (2877 g, 95% CI: 2876-2877) had 80 g higher birth weight compared with UCF (2797 g, 95% CI: 2796-2798). Households using UCF and cooking without separate kitchen (2779 g, 95% CI:2778-2780) had 59 g and 98 g lower MBW as compared to the households using UCF and cooking in separate kitchen (2817 g, 95% CI:2816-2818) and CCF respectively. Significant associations of LBW observed with the place of cooking and cooking practices but no significant association found for cooking fuels. The HAP from poor cooking practices is associated with risks of LBW in India. Transition from unclean to clean fuels, provision of the separate kitchen should be encouraged to reduce the maternal exposure to HAP and improve birth outcomes.

Low-Cost Air Quality Sensing towards Smart Homes

The evolution of low-cost sensors (LCSs) has made the spatio-temporal mapping of indoor air quality (IAQ) possible in real-time but the availability of a diverse set of LCSs make their selection challenging. Converting individual sensors into a sensing network requires the knowledge of diverse research disciplines, which we aim to bring together by making IAQ an advanced feature of smart homes. The aim of this review is to discuss the advanced home automation technologies for the monitoring and control of IAQ through networked air pollution LCSs. The key steps that can allow transforming conventional homes into smart homes are sensor selection, deployment strategies, data processing, and development of predictive models. A detailed synthesis of air pollution LCSs allowed us to summarise their advantages and drawbacks for spatio-temporal mapping of IAQ. We concluded that the performance evaluation of LCSs under controlled laboratory conditions prior to deployment is recommended for quality assurance/control (QA/QC), however, routine calibration or implementing statistical techniques during operational times, especially during long-term monitoring, is required for a network of sensors. The deployment height of sensors could vary purposefully as per location and exposure height of the occupants inside home environments for a spatio-temporal mapping. Appropriate data processing tools are needed to handle a huge amount of multivariate data to automate pre-/post-processing tasks, leading to more scalable, reliable and adaptable solutions. The review also showed the potential of using machine learning technique for predicting spatio-temporal IAQ in LCS networked-systems.

Proinflammatory Effects in Ex Vivo Human Lung Tissue of Respirable Smoke Extracts from Indoor Cooking in Nepal

Rationale: Exposure to biomass smoke is believed to increase the risk of developing chronic obstructive pulmonary disease. However, little is known about the mechanisms underlying responses to biomass smoke in human lungs.Objectives: This study had two objectives: first, to quantify "real-life" exposures to particulate matter <2 μm in diameter (PM_2.5) and carbon monoxide (CO) measured during cooking on stoves in rural areas of Nepal in different geographical settings; and second, to assess the effect of biomass smoke extracts on inflammatory responses in ex vivo human lung tissue.Methods: Personal exposures to PM_2.5 and indoor near-stove CO concentrations were measured during cooking on a range of stoves in 103 households in 4 different Nepalese villages situated at altitudes between ∼100 and 4,000 m above sea level. Inflammatory profiles to smoke extracts collected in the field were assessed by incubating extracts with human lung tissue fragments and subsequent Luminex analysis.Results: In households using traditional cooking stoves, the overall mean personal exposure to PM_2.5 during cooking was 276.1 μg/m³ (standard deviation [SD], 265 μg/m³), and indoor CO concentration was 16.3 ppm (SD, 19.65 ppm). The overall mean PM_2.5 exposure was reduced by 51% (P = 0.04) in households using biomass fuel in improved cook stoves, and 80% (P < 0.0001) in households using liquefied petroleum gas. Similarly, the indoor CO concentration was reduced by 72% (P < 0.001) and 86% (P < 0.0001) in households using improved cook stoves and liquefied petroleum gas, respectively. Significant increases occurred in 7 of the 17 analytes measured after biomass smoke extract stimulation of human lung tissue (IL-8 [interleukin-8], IL-6, TNF-α [tumor necrosis factor-α], IL-1β, CCL2, CCL3, and CCL13).Conclusions: High levels of real-life exposures to PM_2.5 and CO occur during cooking events in rural Nepal. These exposures induce lung inflammation ex vivo, which may partially explain the increased risk of chronic obstructive pulmonary disease in these communities.

Understanding the association between gradient of cooking fuels and low birth weight in India

BACKGROUND

Birth weight is positively associated with physical and cognitive development of children and adversely associated with the use of unclean cooking fuels. Though studies have examined the contextual determinants of birth weight, no attempt has been made to understand the association of gradient of cooking fuels with birth weight in India. The objective of this paper is to understand the association of type of cooking fuel with low birth weight in India.

METHODS

Unit data from the fourth round of the National Family Health Survey (NFHS) (2015-16), covering 8206 singleton births from four states of India, was used in the analysis. These states reported more than 80% of birth weights by way of health cards issued by a public authority. Linear regression analysis was used to estimate mean birth weight, adjusting for confounders. We computed a new wealth index, excluding electricity and cooking fuels, using principal component analysis to capture the economic gradient of cooking fuel.

RESULTS

Our results suggest a strong gradient of cooking fuels on mean birth weight. The adjusted mean birth weight in households using electricity was 2957 g (95% CI: 2939-2975). It was 2908 g (95% CI: 2907-2910) for LPG, 2792 g (95% CI: 2784-2801) for biogas, 2819 g (95% CI: 2809-2829) for kerosene, 2841 g (95% CI: 2816-2866) for coal/lignite/charcoal, and 2834 g (95% CI: 2831-2836) in households using biomass. A difference of 165 g in predicted mean birth weight was found among children born in households that used electricity in relation to those that used biogas. The difference in relation to kerosene, coal/lignite/charcoal, and biomass was 138 g, 116 g, and 123 g respectively. Significant differences in mean birth weight were also observed by wealth quintiles, mother's underweight, social groups, birth interval, and mother's anemia status.

CONCLUSION

Findings from the study suggest to strengthen the policies on access to clean fuels and meet the interconnected goals of sustainable development.

Longitudinal associations between household solid fuel use and depression in middle-aged and older Chinese population: A cohort study

BACKGROUND

Previous studies found that ambient air pollution was associated with a higher prevalence of depressive symptoms. However, the longitudinal associations between household solid fuel use, which is the main source of household air pollution, and depressive symptoms remain unclear. This cohort study aimed to explore the associations between household solid fuel use and incidence of depressive symptoms in China.

METHODS

In total, 8637 participants were enrolled in this prospective cohort study. Depressive symptoms were assessed using the 10-item Center for Epidemiological Studies Depression Scale. The associations between baseline household solid fuel use and the incidence of depressive symptoms were examined using Cox proportional hazards regression models.

RESULTS

During the 4-year of follow-up, 2074 of 8637 participants developed depressive symptoms. Compared with participants who used clean fuel for both heating and cooking, the multivariate-adjusted hazard ratio (HR) (95% confidence intervals [95% CI]) for depressive symptoms incidence in participants who used solid fuels for two purposes (cooking and heating) was 1.15 (1.01, 1.31). In the solid fuel use subgroup analysis, use of solid fuels for cooking (HR, 1.12; 95% CI, 1.02-1.24) was associated with a higher incidence of depressive symptoms after adjustments while use for heating (HR, 1.05; 95% CI, 0.93-1.18) was not. Moreover, compared with persistent solid fuel users, switching from solid to clean fuels for cooking resulted in a lower risk of depressive symptoms before adjustments (HR, 0.82; 95% CI, 0.71-0.95) and a non-significant association (HR, 0.90; 95% CI, 0.77-1.04) afterwards.

CONCLUSIONS

The results suggest that household solid fuel use for cooking was associated with a higher incidence of depressive symptoms. Preventive strategies based on improving household cooking environment for depressive symptoms should be established.

Household air pollution exposure and associations with household characteristics among biomass cookstove users in Puno, Peru

BACKGROUND

Household air pollution (HAP) from combustion of biomass fuel, such as wood and animal dung, is among the leading environmental risk factors for preventable disease. Close to half of the world's population relies on biomass cookstoves for their daily cooking needs. Understanding factors that affect HAP can inform measures to maximize the effectiveness of cookstove interventions in a cost-effective manner. However, the impact of kitchen and household characteristics, as well as the presence of secondary stoves, on HAP concentrations is poorly understood in Puno, Peru.

OBJECTIVE

To explore how household characteristics explain variability of kitchen area concentrations and personal exposures to CO, PM2.5 and BC from biomass cookstoves among women in rural Peru.

METHODS

Household characteristics (including kitchen materials and layout, wealth, and cooking behaviors) and HAP measurements were collected from 180 households in Puno, Peru, from baseline measurements of a randomized trial. Kitchen area concentrations and personal exposures to carbon monoxide (CO), fine particulate matter (PM2.5) and black carbon (BC) were sampled for 48 h. We implemented simple and multivariable linear regression models to determine the associations between household characteristics and both kitchen area concentration and personal exposure to each pollutant.

RESULTS

Mean daily kitchen area concentrations and personal exposures to HAP were, on average, 48 times above World Health Organization indoor guidelines for PM2.5. We found that roof type explained the most variability in HAP and was strongly associated with both kitchen area concentrations and personal exposures for all pollutants after adjusting for other household variables. Personal exposures were 27%-36% lower for PM2.5, CO and BC, in households with corrugated metal roofs, compared to roofs made of natural materials (straw, totora or reed) after adjusting for other factors. Higher kitchen area concentrations were also associated with less wealth, owning more animals, or sampling during the dry season in multivariable models. Having a liquefied petroleum gas (LPG) stove and having a chimney were associated with lower personal exposures, but were not associated with kitchen area concentrations. Personal exposures were lower by 21% for PM2.5 and 28% for CO and BC concentrations among participants who had both LPG and biomass stoves compared to those with only biomass cookstoves adjusting for other household factors.

CONCLUSIONS

Characterizing HAP within different settings can help identify effective and culturally-relevant solutions to reduce HAP exposures. We found that housing roof type is strongly related to kitchen area concentrations and personal exposures to HAP, perhaps because of greater ventilation in kitchens with metal roofs compared to those with thatch roofs. Although HAP concentrations remained above guidelines for all households, promoting use of metal roof materials and LPG stoves may be actionable interventions that can help reduce exposures to HAP in high-altitude rural Peru and similar settings.

Exposure assessment of indoor particulate matter during pregnancy: a narrative review of the literature

OBJECTIVE

The aim of this review was to summarize the evidence of the exposure assessment approaches of indoor particulate matter (PM) during pregnancy and to recommend future focus areas.

CONTENT

Exposure to indoor PM during pregnancy is associated with adverse birth outcomes. However, many questions remain about the consistency of the findings and the magnitude of this effect. This may be due to the exposure assessment methods used and the challenges of characterizing exposure during pregnancy. Exposure is unlikely to remain constant over the nine-month period. Pregnant females' mobility and activities vary - for example, employment status may be random among females, but among those employed, activities are likely to be greater in the early pregnancy than closer to the delivery of the child.

SUMMARY

Forty three studies that used one of the five categories of indoor PM exposure assessment (self-reported, personal air monitoring, household air monitoring, exposure models and integrated approaches) were assessed. Our results indicate that each of these exposure assessment approaches has unique characteristics, strengths, and weaknesses. While questionnaires and interviews are based on self-report and recall, they were a major component in the reviewed exposure assessment studies. These studies predominantly used large sample sizes. Precision and detail were observed in studies that used integrated approaches (i. e. questionnaires, measurements and exposure models).

OUTLOOK

Given the limitations presented by these studies, exposure misclassification remains possible because of personal, within and between household variability, seasonal changes, and spatiotemporal variability during pregnancy. Therefore, using integrated approaches (i. e. questionnaire, measurements and exposure models) may provide better estimates of PM levels across trimesters. This may provide precision for exposure estimates in the exposure-response relationship.

Predictors of urban household variability of indoor PM2.5 in low socio-economic communities

In epidemiological studies, levels of PM2.5 need to be estimated over time and space. Because of logistical constraints, very few studies have been conducted to assess the variability within and across homes and the predictors of this variability. This study evaluated within- and between-home variability of indoor PM2.5 and identified predictors for PM2.5 in homes of mothers participating in the urban Mother and Child in the Environment birth cohort study in Durban, South Africa. Thirty homes were selected from 300 homes that were previously sampled for PM2.5. Two measurements of PM2.5 levels were conducted in each home within a 1 week interval in both warm and cold seasons (four samplings per home) using Airmetrics MiniVol samplers. A linear mixed-effect model was used to evaluate within- and between-home variability and to identify fixed effects (predictors) that result in reduced variability. The PM2.5 levels in the 30 homes ranged from 2 to 303 μg m-3. The within-home variability accounted for 94% of the total variability in the log-transformed PM2.5 levels for the 30 homes. The fixed effects extracted from the repeated samplings in the present study were used to improve a previously developed multivariable linear regression model for 300 homes, and thereby increased the R2 from 0.50 to 0.54. Inclusion of fixed-effects in multivariable linear regression models resulted in a reasonably robust model that can be used to predict PM2.5 levels in unmeasured homes of the cohort.

Kitchen concentrations of fine particulate matter and particle number concentration in households using biomass cookstoves in rural Honduras

Cooking and heating with solid fuels results in high levels of household air pollutants, including particulate matter (PM); however, limited data exist for size fractions smaller than PM2.5 (diameter less than 2.5 μm). We collected 24-h time-resolved measurements of PM2.5 (n = 27) and particle number concentrations (PNC, average diameter 10-700 nm) (n = 44; 24 with paired PM2.5 and PNC) in homes with wood-burning traditional and Justa (i.e., with an engineered combustion chamber and chimney) cookstoves in rural Honduras. The median 24-h PM2.5 concentration (n = 27) was 79 μg/m3 (interquartile range [IQR]: 44-174 μg/m3); traditional (n = 15): 130 μg/m3 (IQR: 48-250 μg/m3); Justa (n = 12): 66 μg/m3 (IQR: 44-97 μg/m3). The median 24-h PNC (n = 44) was 8.5 × 104 particles (pt)/cm3 (IQR: 3.8 × 104-1.8 × 105 pt/cm3); traditional (n = 27): 1.3 × 105 pt/cm3 (IQR: 3.3 × 104-2.0 × 105 pt/cm3); Justa (n = 17): 6.3 × 104 pt/cm3 (IQR: 4.0 × 104-1.2 × 105 pt/cm3). The 24-h average PM2.5 and particle number concentrations were correlated for the full sample of cookstoves (n = 24, Spearman ρ: 0.83); correlations between PM2.5 and PNC were higher in traditional stove kitchens (n = 12, ρ: 0.93) than in Justa stove kitchens (n = 12, ρ: 0.67). The 24-h average concentrations of PM2.5 and PNC were also correlated with the maximum average concentrations during shorter-term averaging windows of one-, five-, 15-, and 60-min, respectively (Spearman ρ: PM2.5 [0.65, 0.85, 0.82, 0.71], PNC [0.74, 0.86, 0.88, 0.86]). Given the moderate correlations observed between 24-h PM2.5 and PNC and between 24-h and the shorter-term averaging windows within size fractions, investigators may need to consider cost-effectiveness and information gained by measuring both size fractions for the study objective. Further evaluations of other stove and fuel combinations are needed.

Open fire ovens and effects of in-home lavash bread baking on carbon monoxide exposure and carboxyhemoglobin levels among women in rural Armenia

Lavash is a traditional flatbread commonly baked at home by women in Armenia and other Middle Eastern and Caucasus countries. The baking process follows centuries' old recipes and is done primarily in open fire ovens. Data are limited regarding the impact of baking on indoor air quality and health outcomes. This study aimed at assessing the effects of lavash baking on household air pollution and cardiovascular outcomes among women who bake lavash in rural Armenia. A convenience sample of 98 bakers, all women, never-smokers, representing 36 households were enrolled. Carbon monoxide (CO) concentrations and carboxyhemoglobin (COHb) levels were monitored before, during, and/or after baking. As expected, exposure to concentrations of CO peaking at/or above 35-ppm during baking was more likely to occur in homes with fully enclosed and poorly ventilated baking rooms, compared to those with three or fewer walls and/or one or more windows. Bakers in homes where CO concentrations peaked at/or above 35-ppm were more likely to have an increase in post-baking COHb levels compared to those in homes with lower CO concentrations.

Predictors of personal exposure to black carbon among women in southern semi-rural Mozambique

Sub-Saharan Africa (SSA) has the highest proportion of people using unclean fuels for household energy, which can result in products of incomplete combustion that are damaging for health. Black carbon (BC) is a useful marker of inefficient combustion-related particles; however, ambient air quality data and temporal patterns of personal exposure to BC in SSA are scarce. We measured ambient elemental carbon (EC), comparable to BC, and personal exposure to BC in women of childbearing age from a semi-rural area of southern Mozambique. We measured ambient EC over one year (2014-2015) using a high-volume sampler and an off-line thermo-optical-transmission method. We simultaneously measured 5-min resolved 24-h personal BC using a portable MicroAeth (AE51) in 202 women. We used backwards stepwise linear regression to identify predictors of log-transformed 24-h mean and peak (90th percentile) personal BC exposure. We analyzed data from 187 non-smoking women aged 16-46 years. While daily mean ambient EC reached moderate levels (0.9 μg/m³, Standard Deviation, SD: 0.6 μg/m³), daily mean personal BC reached high levels (15 μg/m³, SD: 19 μg/m³). Daily patterns of personal exposure revealed a peak between 6 and 7 pm (>35 μg/m³), attributable to kerosene-based lighting. Key determinants of mean and peak personal exposure to BC were lighting source, kitchen type, ambient EC levels, and temperature. This study highlights the important contribution of lighting sources to personal exposure to combustion particles in populations that lack access to clean household energy.

Machine-learned modeling of PM2.5 exposures in rural Lao PDR

This study presents a machine-learning-enhanced method of modeling PM_2.5 personal exposures in a data-scarce, rural, solid fuel use context. Data collected during a cookstove (Africa Clean Energy (ACE)-1 solar-battery-powered stove) intervention program in rural Lao PDR are presented and leveraged to explore advanced techniques for predicting personal exposures to particulate matter with aerodynamic diameter smaller than 2.5 μm (PM_2.5). Mean 48-h PM_2.5 exposure concentrations for female cooks were measured for the pre- and post-intervention periods (the "Before" and "After" periods, respectively) as 123 μg/m³ and 81 μg/m³. Mean 48-h PM_2.5 kitchen air pollution ("KAP") concentrations were measured at 462 μg/m³ Before and 124 μg/m³ After. Application of machine learning and ensemble modeling demonstrated cross-validated personal exposure predictions that were modest at the individual level but reasonably strong at the group level, with the best models producing an observed vs. predicted r² between 0.26 and 0.31 (r² = 0.49 when using a smaller, un-imputed dataset) and mean Before estimates of 119-120 μg/m³ and After estimates of 86-88 μg/m³. This offered improvement over one typical method of predicting exposure - using a kitchen exposure factor (the ratio of exposure to KAP)- which demonstrated an r² ~ 0.03 and poorly estimated group average values. The results of these analyses highlight areas of methodological improvement for future exposure assessments of household air pollution and provide evidence for researchers to explore the advantages of further incorporating machine learning methods into similar research across wider geographic and cultural contexts.

Combining sensor-based measurement and modeling of PM2.5 and black carbon in assessing exposure to indoor aerosols

Accurate, cost-effective methods are needed for rapid assessment of traffic-related air pollution (TRAP). Typically, real-time data of particulate matter (PM) from portable sensors have been adjusted using data from reference methods such as gravimetric measurement to improve accuracy. The objective of this study was to create a correction factor or linear regression model for the real-time measurements of the RTI's Micro Personal Exposure Monitor (MicroPEM^™) and AethLab's microAeth® black carbon (AE51) sensor to generate accurate real-time data for PM_2.5 (PM_2.5RT) and black carbon (BC_RT) in Cincinnati metropolitan homes. The two sensors and an SKC PM_2.5 Personal Modular impactor were collocated in 44 indoor sampling events for 2 days in residences near major roadways. The reference filter-based analyses conducted by a laboratory included particle mass (SKC PM_2.5 and MicroPEM^™ PM_2.5) and black carbon (SKC BC); these methods are more accurate than real-time sensors but are also more cumbersome and costly. For PM_2.5, the average correction factor, a ratio of gravimetric to real-time, for the MicroPEM^™ PM_2.5 and SKC PM_2.5 utilizing the PM_2.5RT and was 0.94 and 0.83, respectively, with a coefficient of variation (CV) of 84% and 52%, respectively; the corresponding linear regression model had a CV of 54% and 25%. For BC, the average correction factor utilizing the BC_RT and SKC BC was 0.74 with a CV of 36% with the associated linear regression model producing a CV of 56%. The results from this study will help ensure that the real-time exposure monitors are capable of detecting an estimated PM_2.5 after an appropriate statistical model is applied.

Air pollution dispersion from biomass stoves to neighboring homes in Mirpur, Dhaka, Bangladesh

BACKGROUND

Indoor air pollution, including fine particulate matter (PM2.5) and carbon monoxide (CO), is a major risk factor for pneumonia and other respiratory diseases. Biomass-burning cookstoves are major contributors to PM2.5 and CO concentrations. However, high concentrations of PM2.5 (> 1000 μg/m3) have been observed in homes in Dhaka, Bangladesh that do not burn biomass. We described dispersion of PM2.5 and CO from biomass burning into nearby homes in a low-income urban area of Dhaka, Bangladesh.

METHODS

We recruited 10 clusters of homes, each with one biomass-burning (index) home, and 3-4 neighboring homes that used cleaner fuels with no other major sources of PM2.5 or CO. We administered a questionnaire and recorded physical features of all homes. Over 24 h, we recorded PM2.5 and CO concentrations inside each home, near each stove, and outside one neighbor home per cluster. During 8 of these 24 h, we conducted observations for pollutant-generating activities such as cooking. For each monitor, we calculated geometric mean PM2.5 concentrations at 5-6 am (baseline), during biomass burning times, during non-cooking times, and over 24 h. We used linear regressions to describe associations between monitor location and PM2.5 and CO concentrations.

RESULTS

We recruited a total of 44 homes across the 10 clusters. Geometric mean PM2.5 and CO concentrations for all monitors were lowest at baseline and highest during biomass burning. During biomass burning, linear regression showed a decreasing trend of geometric mean PM2.5 and CO concentrations from the biomass stove (326.3 μg/m3, 12.3 ppm), to index home (322.7 μg/m3, 11.2 ppm), neighbor homes sharing a wall with the index home (278.4 μg/m3, 3.6 ppm), outdoors (154.2 μg/m3, 0.7 ppm), then neighbor homes that do not share a wall with the index home (83.1 μg/m3,0.2 ppm) (p = 0.03 for PM2.5, p = 0.006 for CO).

CONCLUSION

Biomass burning in one home can be a source of indoor air pollution for several homes. The impact of biomass burning on PM2.5 or CO is greatest in homes that share a wall with the biomass-burning home. Eliminating biomass burning in one home may improve air quality for several households in a community.

Monitoring and modeling of household air quality related to use of different Cookfuels in Paraguay

In Paraguay, 49% of the population depends on biomass (wood and charcoal) for cooking. Residential biomass burning is a major source of fine particulate matter (PM_2.5 ) and carbon monoxide (CO) in and around the household environment. In July 2016, cross-sectional household air pollution sampling was conducted in 80 households in rural Paraguay. Time-integrated samples (24 hours) of PM_2.5 and continuous CO concentrations were measured in kitchens that used wood, charcoal, liquefied petroleum gas (LPG), or electricity to cook. Qualitative and quantitative household-level variables were captured using questionnaires. The average PM_2.5 concentration (μg/m³ ) was higher in kitchens that burned wood (741.7 ± 546.4) and charcoal (107.0 ± 68.6) than in kitchens where LPG (52.3 ± 18.9) or electricity (52.0 ± 14.8) was used. Likewise, the average CO concentration (ppm) was higher in kitchens that used wood (19.4 ± 12.6) and charcoal (7.6 ± 6.5) than in those that used LPG (0.5 ± 0.6) or electricity (0.4 ± 0.6). Multivariable linear regression was conducted to generate predictive models for indoor PM_2.5 and CO concentrations (predicted R²  = 0.837 and 0.822, respectively). This study provides baseline indoor air quality data for Paraguay and presents a multivariate statistical approach that could be used in future research and intervention programs.

Determinants of the Behavioral Lock-in of Rural Residents’ Direct Biomass Energy Consumption in China

The transition from traditional to modern energy is widely accepted as a critical facilitator of improved health, social, and livelihood outcomes, but over three quarters of China’s rural population are still persisting with traditional energy practices. Using panel data on 28 provinces during 1991–2014, this paper investigates how institutional pressure, status quo inertia, and the allure of power and control affect rural residents’ direct biomass energy consumption (RRDBEC) in China. The empirical results show that: (1) the institutional pressure of the number of staff in rural energy administrative agencies facilitates the lock-in of RRDBEC, but government funding on rural energy development has an opposite impact; (2) status quo inertia, depicted by the lagged term of planting proportion of grain and the expenditure proportion of meat, is verified to lock RRDBEC; (3) the allure of power and control, depicted by the lagged term of ownership of firewood-saving stoves, strengthens the lock-in of RRDBEC; (4) income level, education level, and dependency ratio are verified as significant and negative determinants of RRDBEC, while fuel prices lock RRDBEC. Therefore, the policy implications include transforming the functions of rural energy administrative agencies, increasing government funds, carrying out public education of health and environment awareness, and providing economic incentives.

Global estimation of exposure to fine particulate matter (PM2.5) from household air pollution

BACKGROUND

Exposure to household air pollution (HAP) from cooking with dirty fuels is a leading health risk factor within Asia, Africa and Central/South America. The concentration of particulate matter of diameter ≤ 2.5 μm (PM_2.5) is an important metric to evaluate HAP risk, however epidemiological studies have demonstrated significant variation in HAP-PM_2.5 concentrations at household, community and country levels. To quantify the global risk due to HAP exposure, novel estimation methods are needed, as financial and resource constraints render it difficult to monitor exposures in all relevant areas.

METHODS

A Bayesian, hierarchical HAP-PM_2.5 global exposure model was developed using kitchen and female HAP-PM_2.5 exposure data available in peer-reviewed studies from an updated World Health Organization Global HAP database. Cooking environment characteristics were selected using leave-one-out cross validation to predict quantitative HAP-PM_2.5 measurements from 44 studies. Twenty-four hour HAP-PM_2.5 kitchen concentrations and male, female and child exposures were estimated for 106 countries in Asia, Africa and Latin America.

RESULTS

A model incorporating fuel/stove type (traditional wood, improved biomass, coal, dung and gas/electric), urban/rural location, wet/dry season and socio-demographic index resulted in a Bayesian R² of 0.57. Relative to rural kitchens using gas or electricity, the mean global 24-hour HAP-PM_2.5 concentrations were 290 μg/m³ higher (range of regional averages: 110, 880) for traditional stoves, 150 μg/m³ higher (range of regional averages: 50, 290) for improved biomass stoves, 850 μg/m³ higher (range of regional averages: 310, 2600) for animal dung stoves, and 220 μg/m³ higher (range of regional averages: 80, 650) for coal stoves. The modeled global average female/kitchen exposure ratio was 0.40. Average modeled female exposures from cooking with traditional wood stoves were 160 μg/m³ in rural households and 170 μg/m³ in urban households. Average male and child rural area exposures from traditional wood stoves were 120 μg/m³ and 140 μg/m³, respectively; average urban area exposures were identical to average rural exposures among both sub-groups.

CONCLUSIONS

A Bayesian modeling approach was used to generate unique HAP-PM_2.5 kitchen concentrations and personal exposure estimates for all countries, including those with little to no available quantitative HAP-PM_2.5 exposure data. The global exposure model incorporating type of fuel-stove combinations can add specificity and reduce exposure misclassification to enable an improved global HAP risk assessment.

Usage and impacts of the Envirofit HM-5000 cookstove

Burning solid fuels to fulfill daily household energy needs results in chronic exposure to household air pollution (HAP), which is among the world's greatest health risks. This paper presents the results of a cross-sectional study of cookstove usage, fuel consumption, and indoor PM_2.5 concentrations in rural and urban Honduran homes cooking with the Envirofit HM-5000 metal plancha stove (n = 32) as compared to control households using baseline cooking technologies (n = 33). Temperature-based stove usage measurements showed high HM-5000 acceptance, with significant displacement of the traditional cookstoves at both the urban (99%, P < .05) and rural study sites (75%, P < .05). However, longer-term usage data collected in peri-urban households showed that participants cooked on the HM-5000 more frequently during the 3-day monitoring period than during the following 3 weeks. Average indoor PM_2.5 was 66% lower in HM-5000 households as compared to control households (P < .05). Lower indoor PM_2.5 concentrations observed in participant homes as compared to control households, supported by high usage and traditional stove displacement, suggest the potential for the HM-5000 to yield health improvements in adopting Honduran households.

Sources of household air pollution and their association with fine particulate matter in low-income urban homes in India

INTRODUCTION

Household air pollution (HAP) is poorly characterized in low-income urban Indian communities.

MATERIALS AND METHODS

A questionnaire assessing sources of HAP and 24 h household concentrations of particulate matter less than 2.5 microns in diameter (PM_2.5) were collected in a sample of low-income homes in Pune, India.

RESULTS

In 166 homes, the median 24 h average concentration of PM_2.5 was 167 μg/m³ (IQR: 106-294). Although kerosene and wood use were highly prevalent (22% and 25% of homes, respectively), primarily as secondary fuel sources, high PM_2.5 concentrations were also found in 95 (57%) homes reporting LPG use alone (mean 141 μg/m³; IQR: 92-209). In adjusted linear regression, log PM_2.5 concentration was positively associated with wood cooking fuel (GMR 1.5, 95% CI: 1.1-2.0), mosquito coils (GMR 1.5, 95% CI: 1.1-2.1), and winter season (GMR 1.7, 95% CI: 1.4-2.2). Households in the highest quartile of exposure were positively associated with wood cooking fuel (OR 1.3, 95% CI: 1.1-1.5), incense (OR 1.1, 95% CI: 1.0-1.3), mosquito coils (OR 1.3, 95% CI: 1.1-1.6), and winter season (OR 1.2, 95% CI: 1.1-1.4).

DISCUSSION

We observed high concentrations of PM_2.5 and identified associated determinants in urban Indian homes.

Children under Five from Houses of Unclean Fuel Sources and Poorly Ventilated Houses Have Higher Odds of Suffering from Acute Respiratory Infection in Wolaita-Sodo, Southern Ethiopia: A Case-Control Study

Background

Acute respiratory tract infection is the most common illness in childhood. Ninety-five percent (99% of rural and 80% of urban) of households in Ethiopia primarily use solid fuel for cooking. This study investigated the effect of household fuel use and house ventilation on acute respiratory infection in children, Wolaita-Sodo, Southern Ethiopia.

Methods

A community based case-control study design was used, covering a sample of 1144 children with ratio of 1 : 3 (286 cases and 858 controls) aged between 0 and 59 months. A case was defined as a child who suffered from cough, followed by short, rapid breathing in the last two weeks that preceded the survey, while control was defined as a child who had not any of the respiratory infection signs and symptoms. Study subjects were recruited after a census from households. Data were entered using EpiData version 3.1 and analyzed using SPSS version 21.

Results

The proportion of children aged 1–3 years and 3–5 years was 76% and 24%, respectively. Two-thirds of children lived in households that used solid fuels for cooking (charcoal 62.76% and biomass 24.73%). The majority of households (83%) used open/traditional three-stone stoves. Unclean fuel users for cooking (AOR = 2.09, 95% CI 1.03–4.22), poorly ventilated houses (AOR = 4.32, 95% CI 2.61–7.15), large family size (AOR = 1.85, 95% CI 1.31–2.62), and carrying of a child while cooking (AOR = 1.66, 95% CI 1.18–2.34) were significant risk factors of acute respiratory infection in children under five.

Conclusions

Children from houses of unclean fuel sources and poorly ventilated houses were more likely to be affected by acute respiratory infection. Using clean energy sources and improved stoves is highly suggested.

Developing a predictive model for fine particulate matter concentrations in low socio-economic households in Durban, South Africa

In low-resource settings, there is a need to develop models that can address contributions of household and outdoor sources to population exposures. The aim of the study was to model indoor PM_2.5 using household characteristics, activities, and outdoor sources. Households belonging to participants in the Mother and Child in the Environment (MACE) birth cohort, in Durban, South Africa, were randomly selected. A structured walk-through identified variables likely to generate PM_2.5 . MiniVol samplers were used to monitor PM_2.5 for a period of 24 hours, followed by a post-activity questionnaire. Factor analysis was used as a variable reduction tool. Levels of PM_2.5 in the south were higher than in the north of the city (P < .05); crowding and dwelling type, household emissions (incense, candles, cooking), and household smoking practices were factors associated with an increase in PM_2.5 levels (P < .05), while room magnitude and natural ventilation factors were associated with a decrease in the PM_2.5 levels (P < .05). A reasonably robust PM_2.5 predictive model was obtained with model R² of 50%. Recognizing the challenges in characterizing exposure in environmental epidemiological studies, particularly in resource-constrained settings, modeling provides an opportunity to reasonably estimate indoor pollutant levels in unmeasured homes.

Differential exposure and acute health impacts of inhaled solid-fuel emissions from rudimentary and advanced cookstoves in female CD-1 mice

BACKGROUND

There is an urgent need to provide access to cleaner end user energy technologies for the nearly 40% of the world's population who currently depend on rudimentary cooking and heating systems. Advanced cookstoves (CS) are designed to cut emissions and solid-fuel consumption, thus reducing adverse human health and environmental impacts.

STUDY PREMISE

We hypothesized that, compared to a traditional (Tier 0) three-stone (3-S) fire, acute inhalation of solid-fuel emissions from advanced natural-draft (ND; Tier 2) or forced-draft (FD; Tier 3) stoves would reduce exposure biomarkers and lessen pulmonary and innate immune system health effects in exposed mice.

RESULTS

Across two simulated cooking cycles (duration ~ 3h), emitted particulate mass concentrations were reduced 80% and 62% by FD and ND stoves, respectively, compared to the 3-S fire; with corresponding decreases in particles visible within murine alveolar macrophages. Emitted carbon monoxide was reduced ~ 90% and ~ 60%, respectively. Only 3-S-fire-exposed mice had increased carboxyhemoglobin levels. Emitted volatile organic compounds were FD ≪ 3-S-fire ≤ ND stove; increased expression of genes involved in xenobiotic metabolism (COX-2, NQO1, CYP1a1) was detected only in ND- and 3-S-fire-exposed mice. Diminished macrophage phagocytosis was observed in the ND group. Lung glutathione was significantly depleted across all CS groups, however the FD group had the most severe, ongoing oxidative stress.

CONCLUSIONS

These results are consistent with reports associating exposure to solid fuel stove emissions with modulation of the innate immune system and increased susceptibility to infection. Lower respiratory infections continue to be a leading cause of death in low-income economies. Notably, 3-S-fire-exposed mice were the only group to develop acute lung injury, possibly because they inhaled the highest concentrations of hazardous air toxicants (e.g., 1,3-butadiene, toluene, benzene, acrolein) in association with the greatest number of particles, and particles with the highest % organic carbon. However, no Tier 0-3 ranked CS group was without some untoward health effect indicating that access to still cleaner, ideally renewable, energy technologies for cooking and heating is warranted.

Quantifying the Contribution to Uncertainty in Mortality Attributed to Household, Ambient, and Joint Exposure to PM2.5 From Residential Solid Fuel Use

While there have been substantial efforts to quantify the health burden of exposure to PM_2.5 from solid fuel use (SFU), the sensitivity of mortality estimates to uncertainties in input parameters has not been quantified. Moreover, previous studies separate mortality from household and ambient air pollution. In this study, we develop a new estimate of mortality attributable to SFU due to the joint exposure from household and ambient PM_2.5 pollution and perform a variance-based sensitivity analysis on mortality attributable to SFU. In the joint exposure calculation, we estimate 2.81 (95% confidence interval: 2.48-3.28) million premature deaths in 2015 attributed to PM_2.5 from SFU, which is 580,000 (18%) fewer deaths than would be calculated by summing separate household and ambient mortality calculations. Regarding the sources of uncertainties in these estimates, in China, India, and Latin America, we find that 53-56% of the uncertainty in mortality attributable to SFU is due to uncertainty in the percent of the population using solid fuels and 42-50% from the concentration-response function. In sub-Saharan Africa, baseline mortality rate (72%) and the concentration-response function (33%) dominate the uncertainty space. Conversely, the sum of the variance contributed by ambient and household PM_2.5 exposure ranges between 15 and 38% across all regions (the percentages do not sum to 100% as some uncertainty is shared between parameters). Our findings suggest that future studies should focus on more precise quantification of solid fuel use and the concentration-response relationship to PM_2.5, as well as mortality rates in Africa.

Organic and inorganic speciation of particulate matter formed during different combustion phases in an improved cookstove

Residential solid fuel combustion in cookstoves has established health impacts including bladder and lung cancers, cataracts, low birth weight, and pneumonia. The chemical composition of particulate matter (PM) from 4 commonly-used solid fuels (coal, dung, ambient/dry applewood, and oakwood pellets), emitted from a gasifier cookstove, as well as propane, were examined. Temporal changes between the different cookstove burn-phases were also explored. Normalized concentrations of non-refractory PM₁, total organics, chloride, ammonium, nitrate, sulfate, and 41 particle-phase polycyclic aromatic hydrocarbons (PAHs) were measured using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a Thermal desorption Aerosol Gas chromatograph (TAG), respectively. Coal demonstrated the highest fraction of organic matter in its particulate emission composition (98%), followed by dung (94%). Coal and dung also demonstrated the highest numbers and concentrations of PAHs. While dry applewood emitted ten times lower organic matter compared to ambient applewood, a higher fraction of these organics was composed of PAHs, especially the more toxic ones such as benzo(a)pyrene (9.63ng/L versus 0.04ng/L), and benzo(b)fluoranthene (31.32ng/L versus 0.19ng/L). Data from the AMS demonstrated no clear trends for any of the combustion fuels over the different combustion phases unlike the previously reported trends observed for the physical characteristics. Of the solid fuels, pellets demonstrated the lowest emissions. Emissions from propane were below the quantification limit of the instruments. This work highlights the benefits of incorporating additional metrics into the cookstove evaluation process, thus enriching the existing PM data inventory.

Pilot Intervention Study of Household Ventilation and Fine Particulate Matter Concentrations in a Low-Income Urban Area, Dhaka, Bangladesh

Fine particulate matter (PM_2.5) is a risk factor for pneumonia; ventilation may be protective. We tested behavioral and structural ventilation interventions on indoor PM_2.5 in Dhaka, Bangladesh. We recruited 59 good ventilation (window or door in ≥ 3 walls) and 29 poor ventilation (no window, one door) homes. We monitored baseline indoor and outdoor PM_2.5 for 48 hours. We asked all participants to increase ventilation behavior, including opening windows and doors, and operating fans. Where permitted, we installed windows in nine poor ventilation homes, then repeated PM_2.5 monitoring. We estimated effects using linear mixed-effects models and conducted qualitative interviews regarding motivators and barriers to ventilation. Compared with poor ventilation homes, good ventilation homes were larger, their residents wealthier and less likely to use biomass fuel. In multivariable linear mixed-effects models, ventilation structures and opening a door or window were inversely associated with the number of hours PM_2.5 concentrations exceeded 100 and 250 μg/m³. Outdoor air pollution was positively associated with the number of hours PM_2.5 concentrations exceeded 100 and 250 μg/m³. Few homes accepted window installation, due to landlord refusal and fear of theft. Motivators for ventilation behavior included cooling of the home and sunlight; barriers included rain, outdoor odors or noise, theft risk, mosquito entry, and, for fan use, perceptions of wasting electricity or unavailability of electricity. We concluded that ventilation may reduce indoor PM_2.5 concentrations but, there are barriers to increasing ventilation and, in areas with high ambient PM_2.5 concentrations, indoor concentrations may remain above recommended levels.

Effectiveness of interventions to reduce household air pollution and/or improve health in homes using solid fuel in low-and-middle income countries: A systematic review and meta-analysis

BACKGROUND

Cookstove intervention programs have been increasing over the past two (2) decades in Low and Middle Income Countries (LMICs) across the globe. However, there remains uncertainty regarding the effects of these interventions on household air pollution concentrations, personal exposure concentrations and health outcomes.

OBJECTIVES

The primary objective was to determine if household air pollution (HAP) interventions were associated with improved indoor air quality (IAQ) in households in LMICs. Given the potential impact of HAP interventions on health, a secondary objective was to evaluate the effectiveness of HAP interventions to improve health in populations receiving these interventions.

DATA SOURCES

OVID Medline, Ovid Embase, SCOPUS and PubMED were searched from their inception until December 2015 with no restrictions on study design. The WHO Global database of household air pollution measurements and Members' archives were also reviewed together with the reference lists of identified reviews and relevant articles.

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS AND INTERVENTION

We considered randomized controlled trials, or non-randomized control trials, or before-and-after studies; original studies; studies conducted in a LMIC (based on the United Nations Human Development Report released in March 2013 (World Bank, 2013); interventions that were explicitly aimed at improving IAQ and/or health from solid fuel use; studies published in a peer-reviewed journal or student theses or reports; studies that reported on outcomes which was indicative of IAQ or/and health. There was no restriction on the type of comparator (e.g. household receiving plancha vs. household using traditional cookstove) used in the intervention study.

STUDY APPRAISAL AND SYNTHESIS METHODS

Five review authors independently used pre-designed data collection forms to extract information from the original studies and assessed risk of bias using the Effective Public Health Practice Project (EPHPP). We computed standardized weighted mean difference (SMD) using random-effects models. Heterogeneity was computed using the Q and I2-statistics. We examined the influence of various characteristics on the study-specific effect estimates by stratifying the analysis by population type, study design, intervention type, and duration of exposure monitoring. The trim and fill method was used to assess the potential impact of missing studies.

RESULTS

Fifty-five studies met our a priori inclusion criteria and were included in the systematic review. Fifteen studies provided 43 effect estimates for our meta-analysis. The largest improvement in HAP was observed for average particulate matter (PM) (SMD=1.57) concentrations in household kitchens (1.03), followed by daily personal average concentrations of PM (1.18), and carbon monoxide (CO) concentrations in kitchens. With respect to personal PM, significant improvement was observed in studies of children (1.26) and studies monitoring PM for ≥24h (1.32). This observation was also noted in terms of studies of kitchen concentrations of CO. A significant improvement was also observed for kitchen levels of PM in both adult populations (1.56) and in RCT/cohort designs (1.59) involving replacing cookstoves without chimneys. Our findings on health outcomes were inconclusive.

LIMITATIONS, CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

We observed high statistical between study variability in the study-specific estimate. Thus, care should be taken in concluding that HAP interventions - as currently designed and implemented - support reductions in the average kitchen and personal levels of PM and CO. Further, there is limited evidence that current stand-alone HAP interventions yield any health benefits. Post-intervention levels of pollutants were generally still greatly in excess of the relevant WHO guideline and thus a need to promote cleaner fuels in LMICs to reduce HAP levels below the WHO guidelines.

SYSTEMATIC REVIEW REGISTRATION NUMBER

The review has been registered with PROSPERO (registration number CRD42014009768).

A comparative study of human exposures to household air pollution from commonly used cookstoves in Sri Lanka

Solid fuel burning cookstoves are a major source of household air pollution (HAP) and a significant environmental health risk in Sri Lanka. We report results of the first field study in Sri Lanka to include direct measurements of both real-time indoor concentrations and personal exposures of fine particulate matter (PM_2.5 ) in households using the two most common stove types in Sri Lanka. A purposive sample of 53 households was selected in the rural community of Kopiwatta in central Sri Lanka, roughly balanced for stove type (traditional or improved 'Anagi') and ventilation (chimney present or absent). At each household, 48-h continuous real-time measurements of indoor kitchen PM_2.5 and personal (primary cook) PM_2.5 concentrations were measured using the RTI MicroPEM^™ personal exposure monitor. Questionnaires were used to collect data related to household demographics, characteristics, and self-reported health symptoms. All primary cooks were female and of an average age of 47 years, with 66% having completed primary education. Median income was slightly over half the national median monthly income. Use of Anagi stoves was positively associated with a higher education level of the primary cook (P = 0.026), although not associated with household income (P = 0.18). The MicroPEM monitors were well-received by participants, and this study's valid data capture rate exceeded 97%. Participant wearing compliance during waking hours was on average 87.2% on Day 1 and 83.3% on Day 2. Periods of non-compliance occurred solely during non-cooking times. The measured median 48-h average indoor PM_2.5 concentration for households with Anagi stoves was 64 μg/m³ if a chimney was present and 181 μg/m³ if not. For households using traditional stoves, these values were 70 μg/m³ if a chimney was present and 371 μg/m³ if not. Overall, measured indoor PM_2.5 concentrations ranged from a minimum of 33 μg/m³ to a maximum of 940 μg/m³ , while personal exposure concentrations ranged from 34 to 522 μg/m³ . Linear mixed effects modeling of the dependence of indoor concentrations on stove type and presence or absence of chimney showed a significant chimney effect (65% reduction; P < 0.001) and an almost significant stove effect (24% reduction; P = 0.054). Primary cooks in households without chimneys were exposed to substantially higher levels of HAP than those in households with chimneys, while exposures in households with traditional stoves were moderately higher than those with improved Anagi stoves. As expected, simultaneously measuring both indoor concentrations and personal exposure levels indicate significant exposure misclassification bias will likely result from the use of a stationary monitor as a proxy for personal exposure. While personal exposure monitoring is more complex and expensive than deploying simple stationary devices, the value an active personal PM monitor like the MicroPEM adds to an exposure study should be considered in future study designs.

Patterns of domestic exposure to carbon monoxide and particulate matter in households using biomass fuel in Janakpur, Nepal

Household Air Pollution (HAP) from biomass cooking fuels is a major cause of morbidity and mortality in low-income settings worldwide. In Nepal the use of open stoves with solid biomass fuels is the primary method of domestic cooking. To assess patterns of domestic air pollution we performed continuous measurement of carbon monoxide (CO) and particulate Matter (PM2.5) in 12 biomass fuel households in Janakpur, Nepal. We measured kitchen PM2.5 and CO concentrations at one-minute intervals for an approximately 48-h period using the TSI DustTrak II 8530/SidePak AM510 (TSI Inc, St. Paul MN, USA) or EL-USB-CO data logger (Lascar Electronics, Erie PA, USA) respectively. We also obtained information regarding fuel, stove and kitchen characteristics and cooking activity patterns. Household cooking was performed in two daily sessions (median total duration 4 h) with diurnal variability in pollutant concentrations reflecting morning and evening cooking sessions and peak concentrations associated with fire-lighting. We observed a strong linear relationship between PM2.5 measurements obtained by co-located photometric and gravimetric monitoring devices, providing local calibration factors of 4.9 (DustTrak) and 2.7 (SidePak). Overall 48-h average CO and PM2.5 concentrations were 5.4 (SD 4.3) ppm (12 households) and 417.6 (SD 686.4) μg/m3 (8 households), respectively, with higher average concentrations associated with cooking and heating activities. Overall average PM2.5 concentrations and peak 1-h CO concentrations exceeded WHO Indoor Air Quality Guidelines. Average hourly PM2.5 and CO concentrations were moderately correlated (r = 0.52), suggesting that CO has limited utility as a proxy measure for PM2.5 exposure assessment in this setting. Domestic indoor air quality levels associated with biomass fuel combustion in this region exceed WHO Indoor Air Quality standards and are in the hazardous range for human health.

Spatio-temporal measurement of indoor particulate matter concentrations using a wireless network of low-cost sensors in households using solid fuels

Many households use solid fuels for cooking and heating purposes. There is currently a knowledge gap in our understanding of the variations in indoor air quality throughout the household as most of the studies focus on the areas in the close proximity of the cookstove. A low-cost wireless particulate matter (PM) sensor network was developed and deployed in households in Raipur, India to establish the spatio-temporal variation of PM concentrations. The data from multiple sensors were acquired in real-time with a wireless system. Data collected from the sensors agreed well (R² =0.713) with the reference data collected from a commercially available instrument. Low spatial variability was observed within the kitchen due to its small size and poor ventilation - a common feature of most rural Indian kitchens. Due to insufficient ventilation from open doors and windows, high PM concentrations similar to those found in the kitchen were also found in the adjoining rooms. The same household showed significantly different post-extinguished cookstove PM concentration decay rates (0.26mg/m³-min and 0.87mg/m³-min) on different days, owing to varying natural air exchange rates (7.68m³/min and 37.40m³/min).

[Indoor air pollution by fine particulate matter in the homes of newborns]

INTRODUCTION

Air pollution by particulate matter (PM) is a major public health problem. In Chile, the study has focused on outdoor air and PM₁₀, rather than indoor air and PM_2.5. Because newborns and infants spend most of their time at home, it is necessary to evaluate the exposure to indoor air pollution in this susceptible population.

OBJECTIVE

To determine concentration of PM_2.5 in the homes of newborns and identify the emission sources of the pollutants.

PATIENTS AND METHOD

The PM_2.5 concentration ([PM_2.5]) was collected over a 24hour period in 207 households. Baseline sociodemographic information and environmental factors (heating, ventilation, smoking and house cleaning), were collected.

RESULTS

The median [PM_2.5] was 107.5μg/m³. Family history of asthma was associated with lower [PM_2.5] (P=.0495). Homes without heating showed a lower median [PM_2.5], 58.6μg/m³, while those using firewood, kerosene, and electricity ranged between 112.5 and 114.9, and coal users' homes reached 162.9μg/m³. Wood using homes had significant differences (P=.0164) in median [PM_2.5] whether the stove had complete combustion (98.2μg/m³) vs. incomplete (112.6μg/m³), or a salamander stove (140.6μg/m³). Cigarette smoking was reported in 8.7% of the households, but was not associated with the [PM_2.5]. Ventilation was associated with a higher median [PM_2.5] (120.6 vs. 99.1μg/m³, P=.0039).

CONCLUSION

We found homes with high [PM_2.5]. Residential wood consumption was almost universal, and it is associated with the [PM_2.5]. Natural ventilation increased MP_2.5, probably due to infiltration from outside.

Ambient and household air pollution: complex triggers of disease

Concentrations of outdoor air pollution are on the rise, particularly due to rapid urbanization worldwide. Alternatively, poor ventilation, cigarette smoke, and other toxic chemicals contribute to rising concentrations of indoor air pollution. The World Health Organization recently reported that deaths attributable to indoor and outdoor air pollutant exposure are more than double what was originally documented. Epidemiological, clinical, and animal data have demonstrated a clear connection between rising concentrations of air pollution (both indoor and outdoor) and a host of adverse health effects. During the past five years, animal, clinical, and epidemiological studies have explored the adverse health effects associated with exposure to both indoor and outdoor air pollutants throughout the various stages of life. This review provides a summary of the detrimental effects of air pollution through examination of current animal, clinical, and epidemiological studies and exposure during three different periods: maternal (in utero), early life, and adulthood. Additionally, we recommend future lines of research while suggesting conceivable strategies to curb exposure to indoor and outdoor air pollutants.

Indoor Particulate Matter Concentration, Water Boiling Time, and Fuel Use of Selected Alternative Cookstoves in a Home-Like Setting in Rural Nepal

Alternative cookstoves are designed to improve biomass fuel combustion efficiency to reduce the amount of fuel used and lower emission of air pollutants. The Nepal Cookstove Trial (NCT) studies effects of alternative cookstoves on family health. Our study measured indoor particulate matter concentration (PM2.5), boiling time, and fuel use of cookstoves during a water-boiling test in a house-like setting in rural Nepal. Study I was designed to select a stove to be used in the NCT; Study II evaluated stoves used in the NCT. In Study I, mean indoor PM2.5 using wood fuel was 4584 μg/m3, 1657 μg/m3, and 2414 μg/m3 for the traditional, alternative mud brick stove (AMBS-I) and Envirofit G-series, respectively. The AMBS-I reduced PM2.5 concentration but increased boiling time compared to the traditional stove (p-values < 0.001). Unlike AMBS-I, Envirofit G-series did not significantly increase overall fuel consumption. In Phase II, the manufacturer altered Envirofit stove (MAES) and Nepal Nutrition Intervention Project Sarlahi (NNIPS) altered Envirofit stove (NAES), produced lower mean PM2.5, 1573 μg/m3 and 1341 μg/m3, respectively, relative to AMBS-II 3488 μg/m3 for wood tests. The liquid propane gas stove had the lowest mean PM2.5 concentrations, with measurements indistinguishable from background levels. Results from Study I and II showed significant reduction in PM2.5 for all alternative stoves in a controlled setting. In study I, the AMBS-I stove required more fuel than the traditional stove. In contrast, in study II, the MAES and NAES stoves required statistically less fuel than the AMBS-II. Reductions and increases in fuel use should be interpreted with caution because the composition of fuels was not standardized--an issue which may have implications for generalizability of other findings as well. Boiling times for alternative stoves in Study I were significantly longer than the traditional stove--a trade-off that may have implications for acceptability of the stoves among end users. These extended cooking times may increase cumulative exposure during cooking events where emission rates are lower; these differences must be carefully considered in the evaluation of alternative stove designs.

Children's personal exposure to air pollution in rural villages in Bhutan

Exposure assessment studies conducted in developing countries have been based on fixed-site monitoring to date. This is a major deficiency, leading to errors in estimating the actual exposures, which are a function of time spent and pollutant concentrations in different microenvironments. This study quantified school children's daily personal exposure to ultrafine particles (UFP) using real-time monitoring, as well as volatile organic compounds (VOCs) and NO2 using passive sampling in rural Bhutan in order to determine the factors driving the exposures. An activity diary was used to track children's time activity patterns, and difference in mean exposure levels across sex and indoor/outdoor were investigated with ANOVA. 82 children, attending three primary schools participated in this study; S1 and S2 during the wet season and S3 during the dry season. Mean daily UFP exposure (cm(-3)) was 1.08×10(4) for children attending S1, 9.81×10(3) for S2, and 4.19×10(4) for S3. The mean daily NO2 exposure (µg m(-3)) was 4.27 for S1, 3.33 for S2 and 5.38 for S3 children. Likewise, children attending S3 also experienced higher daily exposure to a majority of the VOCs than those attending S1 and S2. Time-series of UFP personal exposures provided detailed information on identifying sources of these particles and quantifying their contributions to the total daily exposures for each microenvironment. The highest UFP exposure resulted from cooking/eating, contributing to 64% of the daily exposure, due to firewood combustion in houses using traditional mud cookstoves. The lowest UFP exposures were during the hours that children spent outdoors at school. The outcomes of this study highlight the significant contributions of lifestyle and socio-economic factors in personal exposures and have applications in environmental risk assessment and household air pollution mitigation in Bhutan.

Real-time particulate and CO concentrations from cookstoves in rural households in Udaipur, India

Almost 3 billion people around the globe use traditional three-stone cookstoves and open fires to warm and feed themselves. The World Health Organization estimates annual mortality rates from domestic solid fuel combustion to be around 4 million. One of the most affected countries is India. Quantifying pollutant concentrations from these cookstoves during different phases of operation and understanding the factors influencing their variability may help to identify where improvements should be targeted, enhancing indoor air quality for millions of the world's most vulnerable people. Gas and particulate measurements were collected between June and August, 2012, for 51 households using traditional cookstoves, in the villages of Udaipur district, Rajasthan, India. Mean pollutant concentrations during steady-state mode were 4989 μm(2) cm(-3), 9835 μg m(-3), and 18.5 ppm for lung-deposited surface area, PM2.5, and CO, respectively. Simple and multivariate regression analysis was conducted. Fuel amount, fuel diameter, duration of the cookstove run, roof-type, and the room dimension explained between 7% and 21% of the variability for the pollutant metrics. CO demonstrated weaker correlations with explanatory variables. Some of these variables may be indicative of socio-economic status and could be used as proxies of exposure in lieu of pollutant measurements, hence these variables may help identify which households to prioritize for intervention. Such associations should be further explored.

Adverse effects of coal combustion related fine particulate matter (PM2.5) on nematode Caenorhabditis elegans

The toxic effects of coal combustion related fine particulate matter (PM2.5), collected from Datong, Shanxi province, China, on nematode Caenorhabditis elegans were investigated. Exposure to PM2.5 resulted in deficits in development, reproduction, locomotion behavior, and lifespan, and induction of intestinal autofluorescence or reactive oxygen species (ROS) production. Prolonged exposure to PM2.5 led to more severe toxicity on nematodes than acute exposure. In addition, exposure to PM2.5 induced altered expression patterns of genes required for the control of oxidative stress. Reduction in mean defecation cycle length and developmental deficits in AVL and DVB neurons, which are involved in the control of defecation behavior, were also triggered by PM2.5 exposure. Thus, oxidative stress and abnormal defecation behavior may contribute greatly to the toxicity of coal combustion related PM2.5 in nematodes. The results also imply that the long-term adverse effects of coal combustion related PM2.5 on environmental organisms should be carefully considered.