Impact of partial fuel switch on household air pollutants in sub-Sahara Africa

Geospatial analysis of spatial distribution, patterns, and relationships of health status in the belt and road initiative

The Health Silk Road plays a crucial role in the Belt and Road Initiative, and comprehending the health status within the participating countries is fundamental for fostering cooperation in public health. This paper collected five health indicators to represent the health status of the Belt and Road countries. Employing spatial statistics, the spatial patterns of health indicators and the associations with influencing factors were investigated. The utilized spatial statistics encompass spatial autocorrelation methods, geographical detector and spatial lag model. The results revealed obvious disparities and significant positive spatial autocorrelation of health indicators within the Belt and Road countries. Specifically, countries in Sub-Saharan Africa exhibited significant clustering of limited health indicators, while countries in Europe and Central Asia demonstrated significant clustering of robust health indicators. Furthermore, the health indicators exhibited significant spatial heterogeneity and association with the influencing factors. Universal health coverage, household air pollution, and the prevalence of undernourishment emerge as influential factors affecting health indicators. Overall, our findings highlighted complex influencing factors that contributed to the profound health inequalities across the Belt and Road countries. These factors should be duly considered in public health collaborations within the Belt and Road Initiative.

A Critical Review on the Development and Utilization of Energy Systems in Uganda

We live in a world that is completely dependent on energy; thus, humankind can no longer live without power. With electricity being the main form of energy today, this has increased the complexity of our life today. In Uganda, electricity generation is mainly through hydropower, which puts the country in the bottleneck of overdependence on one source of energy. There are many energy systems out there that the country can use to diversify its electricity generation. Therefore, the need to understand the level of development and utilization of various energy systems has been the underlying question for this present study. A comprehensive literature survey was conducted using electronic databases, including ScienceDirect, Wiley, Sage, Scopus, Taylor & Francis, and Google Scholar. The publications in the form of reports, conference papers, working papers, discussion papers, journal articles, book sections, and textbooks were considered in this study. In total, 11 energy systems, including human and animal energy, solid biomass (firewood), hydropower, wind, geothermal, solar, nuclear, peat, coal, petroleum, and nonsolid biomass (methanol, hydrogen, ethanol, biodiesel, and biogas), are described. The current and future development and utilization of these energy systems have been described. The challenges for developing and utilizing these systems were elaborated on, and the solutions for their challenges were presented. Hydropower from the Nile River, being the main river for large hydropower plant construction, is the dominant energy system in Uganda. Nuclear energy will be the salvation for the country's electric energy supply in the near future. Therefore, Uganda needs to bet big on nuclear energy.

Physical and chemical properties of dust in the Pre-Aral region of Uzbekistan

The aim of this work is study of physical and chemical properties of dust of the Pre-Aral region of Uzbekistan such as Karakalpakstan and Khorezm that are located near the three deserts such as the Aralkum, Karakum, and Kyzylkum. The dust particles fell on glass have been collected in Karakalpakstan and Khorezm and studied systematically by employing wide range of methods. Particle volume vs size distribution has been measured with maximum around 600 nm and ~ 10 µm. The major and minor constituent materials present in the dust have been studied systematically by X-ray fluorescence spectroscopy, energy dispersive X-ray diffraction, and inductively coupled plasma optical emission spectroscopy. Main characteristic absorption bands corresponding to Si-O, Si-O-Si bonding in quartz and Fe-O bonds in hematite Fe₂O₃ have been identified by infrared and Raman spectroscopy. Quartz, hematite, lime, corundum, magnesia, and several other trace minerals have been identified in the dust particles. X-ray diffraction peaks corresponding to quartz, hematite, and corundum are sharp and are found to be more crystalline with some level of disorder. Analysis of the particle size and crystallinity on human being has been performed: disordered or crystalline quartz can create the lung disease; the particles in the size of 0.5-0.7 µm may produce diseases such as chronic silicosis, silicosis, and silica tuberculosis whereas hematite might create lung disease. Dust particles worsen optical transmittance of glass of the panels.

Will open waste burning become India's largest air pollution source?

India struggles with frequent exceedances of the ambient air quality standard for particulate matter and benzene. In the past two decades, India has made considerable progress in tackling indoor air pollution, by phasing out kerosene lamps, and pushing biofuel using households towards Liquefied Petroleum Gas (LPG) usage. In this study, we use updated emission inventories and trends in residential fuel consumption, to explore changes in the contribution of different sectors towards India's largest air pollution problem. We find that residential fuel usage is still the largest air pollution source, and that the <10% households using cow dung as cooking fuel contribute ∼50% of the residential PM_2.5 emissions. However, if current trends persist, residential biofuel usage in India is likely to be phased out by 2035. India's renewable energy policies are likely to reduce emissions in the heat and electricity sector, and manufacturing industries, in the mid-term. PM_2.5 emissions from open waste burning, on the other hand, hardly changed in the decade from 2010 to 2020. We conclude that without strong policies to promote recycling and upcycling of non-biodegradable waste, and the conversion of biodegradable waste to biogas, open waste burning is likely to become India's largest source of air pollution by 2035. While our study is limited to India, our findings are of relevance for other countries in the global South suffering from similar waste management challenges.

Cooking with biomass fuels and mortality among Chinese elderly people: A prospective cohort study

This study used data from the Chinese Longitudinal Healthy Longevity Survey (n = 9765, age 65+) to investigate the impact of biomass fuels on the mortality of the Chinese elderly population. The association between biomass fuels and mortality was examined using a Cox proportional hazards model. We evaluated the difference in risk of death between those who switched fuel types from biomass to clean fuels and from clean to biomass fuels versus those who did not during the follow-up period. Participants who used biomass fuels had a higher risk of death than participants who used clean fuels (HR = 1.09, 95% CI: 1.01-1.17). For participants who switched cooking fuel types during the follow-up period, switching from biomass to clean fuels significantly reduced the risk of death (HR = 0.78, 95% CI: 0.67-0.91), while no evidence of an association between switching from clean to biomass fuels and risk of death was found (p > 0.05). Interactions and subgroup analyses indicated that effect estimates were greater for women and non-smokers. Biomass fuels may be associated with a higher risk of death among Chinese elderly. Research measuring personal exposure levels to indoor air pollution caused by biomass fuels combustion is required to confirm our results.

Cooking with biomass fuels increased the risk for cognitive impairment and cognitive decline among the oldest-old Chinese adults (2011-2018): A prospective cohort study

BACKGROUNDS

While the pernicious effects of outdoor air pollution on cognitive ability have been previously examined, evidence regarding household air pollution is scarce.

METHODS

Using data from the Chinese Longitudinal Healthy Longevity Survey, we explored the relationship between cooking with biomass fuel and cognitive impairment and cognitive decline using a Cox proportional hazards model. We further assessed the correlation of biomass fuels and cognitive score using a generalized estimating equation. Cognitive ability was measured based on the Chinese version of the Mini-Mental State Examination (MMSE) and cognitive impairment was defined as MMSE < 24 points and cognitive decline was defined as a reduction of MMSE ≥ 3 points. On follow-up, we investigated the effect of switch-cooking combustibles on cognitive ability.

RESULTS

The mean (SD) age of 4161 participants was 81.7 (10.0) years old. The reported cooking with biomass fuels was correlated with an elevated risk of cognitive impairment (hazard ratio (HR): 1.19, 95% confidence interval (CI): 1.04, 1.37) and cognitive decline (HR: 1.18, 95% CI: 1.04, 1.33). Besides, cooking with biomass fuels was related to a decrease in cognitive score (β: -0.43, 95% CI: -0.73, -0.14). In comparison to persistent biomass fuel users, participants who reported changing their primary cooking fuels from biomass to clean fuels exhibited a reduced risk of cognitive impairment (HR: 0.68, 95% CI: 0.57, 0.82) and cognitive decline (HR: 0.66, 95% CI: 0.56, 0.76) and a higher cognitive score (β: 0.72, 95% CI: 0.17, 1.26). Cooking without ventilated cookstoves was associated with a higher risk of cognitive impairment (HR: 1.31, 95% CI: 1.10, 1.58) and cognitive decline (HR: 1.18, 95% CI: 1.02, 1.38), regardless of types of cooking fuels. Interaction and stratified analyses showed relatively poor cognitive ability in participants who engaged in irregular exercise or were not living with family members.

CONCLUSIONS

Cooking with biomass fuels was correlated with a higher risk of cognitive impairment and cognitive decline. Among the oldest-old population, this risk may, however, be lower for those changing their primary cooking fuels from biomass to clean fuels.

The Driving Influence of Multi-Dimensional Urbanization on PM2.5 Concentrations in Africa: New Evidence from Multi-Source Remote Sensing Data, 2000-2018

Africa’s PM_2.5 pollution has become a security hazard, but the understanding of the varying effects of urbanization on driven mechanisms of PM_2.5 concentrations under the rapid urbanization remains largely insufficient. Compared with the direct impact, the spillover effect of urbanization on PM_2.5 concentrations in adjacent regions was underestimated. Urbanization is highly multi-dimensional phenomenon and previous studies have rarely distinguished the different driving influence and interactions of multi-dimensional urbanization on PM_2.5 concentrations in Africa. This study combined grid and administrative units to explore the spatio-temporal change, spatial dependence patterns, and evolution trend of PM_2.5 concentrations and multi-dimensional urbanization in Africa. The differential influence and interaction effects of multi-dimensional urbanization on PM_2.5 concentrations under Africa’s rapid urbanization was further analyzed. The results show that the positive spatial dependence of PM_2.5 concentrations gradually increased over the study period 2000–2018. The areas with PM_2.5 concentrations exceeding 35 μg/m³ increased by 2.2%, and 36.78% of the African continent had an increasing trend in Theil–Sen index. Urbanization was found to be the main driving factor causing PM_2.5 concentrations changes, and economic urbanization had a stronger influence on air quality than land urbanization or population urbanization. Compared with the direct effect, the spillover effect of urbanization on PM_2.5 concentrations in two adjacent regions was stronger, particularly in terms of economic urbanization. The spatial distribution of PM_2.5 concentrations resulted from the interaction of multi-dimensional urbanization. The interaction of urbanization of any two different dimensions exhibited a nonlinear enhancement effect on PM_2.5 concentrations. Given the differential impact of multi-dimensional urbanization on PM_2.5 concentrations inside and outside the region, this research provides support for the cross-regional joint control strategies of air pollution in Africa. The findings also indicate that PM_2.5 pollution control should not only focus on urban economic development strategies but should be an optimized integration of multiple mitigation strategies, such as improving residents’ lifestyles, optimizing land spatial structure, and upgrading the industrial structure.

A system dynamics-based scenario analysis of residential solid waste management in Kisumu, Kenya

The problem of solid waste management presents an issue of increasing importance in many low-income settings, including the progressively urbanised context of Kenya. Kisumu County is one such setting with an estimated 500 t of waste generated per day and with less than half of it regularly collected. The open burning and natural decay of solid waste is an important source of greenhouse gas (GHG) emissions and atmospheric pollutants with adverse health consequences. In this paper, we use system dynamics modelling to investigate the expected impact on GHG and PM_2.5 emissions of (i) a waste-to-biogas initiative and (ii) a regulatory ban on the open burning of waste in landfill. We use life tables to estimate the impact on mortality of the reduction in PM_2.5 exposure. Our results indicate that combining these two interventions can generate over 1.1 million tonnes of cumulative savings in GHG emissions by 2035, of which the largest contribution (42%) results from the biogas produced replacing unclean fuels in household cooking. Combining the two interventions is expected to reduce PM_2.5 emissions from the waste and residential sectors by over 30% compared to our baseline scenario by 2035, resulting in at least around 1150 cumulative life years saved over 2021–2035. The contribution and novelty of this study lies in the quantification of a potential waste-to-biogas scenario and its environmental and health impact in Kisumu for the first time.

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We present a system dynamics study of solid waste management in Kisumu, Kenya.

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Scenarios involve a waste-to-biogas initiative and a ban on open burning in landfill.

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Combined scenario generates 1.1m tonnes cumulative GHG savings by 2035.

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Largest contribution (42%) is from biogas substituting traditional cooking fuels.

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Combined scenario may save 1,150 cumulative life years by 2035, plus ~220 more p.a.

Analysis and modeling of the thermal behavior of an improved pellet cookstove

In Sub-Saharan countries, cooking is usually done at a domestic scale using rudimentary stoves with wood or charcoal as combustibles. To improve the cooking behavior and reduce the deforestation, an improved pellet cookstove was conceptualized with guiding ideas in mind such as simplicity, robustness and ability to burn pellets built with local wood residues under a natural draught. Combustion and water ebullition tests were performed with two configurations of the upper part of the cookstove: thick steel plate or ring, and with standardized EN+ pellets as combustible. The main pollutant gases (CO, CO2 and NOx), together with O2, were continuously measured at different positions of the cookstove during a water ebullition test with the ring configuration. The levels measured above the pot were lower than the thresholds currently proposed by the World Health Organization. Simple and phenomenological thermal models were proposed to simulate the plate, or ring, and water temperatures during the combustion or water ebullition tests and to determine the intrinsic convection coefficients. The maximal relative differences between the experimental and simulated temperatures were computed between 7 and 21%. The stove power was evaluated at 4336 ± 23 W. The cookstove yield for the water ebullition test with the ring configuration was computed equal to 12.3 ± 0.1%, slightly lower than that of cookstoves previously analyzed in the literature.

Household air pollution related to biomass cook stove emissions and its interaction with improved cookstoves

Introduction

Household air pollution (HAP) is associated with significant global morbidity and mortality. Newer initiatives including improved cookstove (IC) and cleaner fuels are being implemented to improve HAP effects.

Methods

A literature review was conducted for household air pollution related to biomass cookstoves in resource limited countries. In January 2018, we electronically searched the PubMed database for the term cookstoves with no date restrictions. We included cohort, case-control, cross-sectional studies, conference abstracts, editorials, and reviews; studies that assessed the emissions related to cookstove and factors affecting HAP emissions.

Results

Twenty-three articles met the objectives of the review. Fine particulate matter with aerodynamic diameter <2.5 µm (PM_2.5), carbon monoxide (CO) and polycyclic aromatic hydrocarbons (PAH) are the major HAP emissions. Emission factors are based on the stove and fuel used while the activity is based on cooking practices. Changes in composition and sources of PM_2.5 causes modification to its resulting toxicity. Many PAHs and their metabolites released by HAP have carcinogenic, teratogenic and mutagenic potential. Improving ventilation decreases concentrations of PM_2.5 and CO in the household air. Few standard tools are available to measure ventilation and continued IC efficacy in long term.

Conclusion

Unavailability of tools to measure ventilation and continued IC efficacy in long term affect uniformity and comparability of IC study results. Community education about the health effects of HAP and importance of ventilation in decreasing HAP is an important aspect of public health policy to prevent HAP effects.

Seasonal variability of resources: The unexplored adversary of biogas use in rural Ethiopia

Biogas digester programmes have been rolled out across many countries in sub-Saharan Africa over the past decade with varying levels of success. In Ethiopia, reported success rates have been low, despite high levels of interaction between non-governmental organisations and various levels of government, plus the establishment of practical eligibility criteria. In Halaba, Ethiopia, we investigated physical and social factors affecting feedstock and water availability using a face-to-face questionnaire-based survey (n = 112) in four kebeles (local administration areas). We found that practices of fuel use and water collection were markedly different between seasons. Fuel use was almost entirely dependent on season, with wood being burned in the wet season and crop residues and cow dung being used instead in the dry season. A matched pair t-test found a significant difference between seasons in terms of water collection times (p = 7.4 × 10-16), with households spending more time and money obtaining clean drinking water in the dry season. Results indicate that seasonal differences in resource availability may reduce the proportion of households that meet the physical characteristics for maintaining a biogas digester by approximately 62% from wet season to dry season. Conversely, the greatest benefits of digester use would be gained in the dry season, when dung could be returned to the soil as a nutrient-rich bioslurry, instead of being combusted as a dirty and inefficient fuel. Seasonality is rarely considered in feasibility studies, so we recommend that these factors should be built into future analyses.

Air Pollution and Climate Forcing of the Charcoal Industry in Africa

The demand for charcoal in Africa is growing rapidly, driven by urbanization and lack of access to electricity. Charcoal production and use, including plastic burning to initiate combustion, release large quantities of trace gases and particles that impact air quality and climate. Here, we develop an inventory of current (2014) and future (2030) emissions from the charcoal supply chain in Africa that we implement in the GEOS-Chem model to quantify the contribution of charcoal to surface concentrations of PM_2.5 and ozone and direct radiative forcing due to aerosols and ozone. We estimate that the charcoal industry in 2014 required 140-460 Tg of biomass and 260 tonnes of plastic and that industry emissions could double by 2030, so that methane emissions from the charcoal industry could outcompete those from open fires by 2025. In 2014, the largest enhancements in PM_2.5 (0.5-1.4 μg m^-3) and ozone (0.4-0.7 ppbv) occur around the densely populated cities in East and West Africa. Cooling due to aerosols (-100 to -300 mW m^-2) is concentrated over dense cities, whereas warming due to ozone is widespread, peaking at 4.2 mW m^-2 over the Atlantic Ocean. These effects will worsen with ongoing dependence on this energy source, spurred by rapid urbanization and absence of viable cleaner alternatives.

Investigating the Association between Wood and Charcoal Domestic Cooking, Respiratory Symptoms and Acute Respiratory Infections among Children Aged Under 5 Years in Uganda: A Cross-Sectional Analysis of the 2016 Demographic and Health Survey

Background: Household air pollution associated with biomass (wood, dung, charcoal, and crop residue) burning for cooking is estimated to contribute to approximately 4 million deaths each year worldwide, with the greatest burden seen in low and middle-income countries. We investigated the relationship between solid fuel type and respiratory symptoms in Uganda, where 96% of households use biomass as the primary domestic fuel. Materials and Methods: Cross-sectional study of 15,405 pre-school aged children living in charcoal or wood-burning households in Uganda, using data from the 2016 Demographic and Health Survey. Multivariable logistic regression analysis was used to identify the associations between occurrence of a cough, shortness of breath, fever, acute respiratory infection (ARI) and severe ARI with cooking fuel type (wood, charcoal); with additional sub-analyses by contextual status (urban, rural). Results: After adjustment for household and individual level confounding factors, wood fuel use was associated with increased risk of shortness of breath (AOR: 1.33 [1.10-1.60]), fever (AOR: 1.26 [1.08-1.48]), cough (AOR: 1.15 [1.00-1.33]), ARI (AOR: 1.36 [1.11-1.66] and severe ARI (AOR: 1.41 [1.09-1.85]), compared to charcoal fuel. In urban areas, Shortness of breath (AOR: 1.84 [1.20-2.83]), ARI (AOR: 1.77 [1.10-2.79]) and in rural areas ARI (AOR: 1.23 [1.03-1.47]) and risk of fever (AOR: 1.23 [1.03-1.47]) were associated with wood fuel usage. Conclusions: Risk of respiratory symptoms was higher among children living in wood compared to charcoal fuel-burning households, with policy implications for mitigation of associated harmful health impacts.

Exposure to Wood Smoke and Associated Health Effects in Sub-Saharan Africa: A Systematic Review

Background

Observational studies suggest that exposure to wood smoke is associated with a variety of adverse health effects in humans.

Objective

We aimed to summarise evidence from sub-Saharan Africa on levels of exposure to pollutants in wood smoke and the association between such exposures and adverse health outcomes.

Methods

PubMed and Google scholar databases were searched for original articles reporting personal exposure levels to pollutants or health outcomes associated with wood smoke exposure in Sub-Saharan African population.

Results

Mean personal PM_2.5 and carbon monoxide levels in the studies ranged from 26.3 ± 1.48 μg/m³ to 1574 ± 287μg/m³ and from 0.64 ± 2.12 ppm to 22 ± 2.4 ppm, respectively. All the reported personal PM_2.5 exposure levels were higher than the World Health Organization's Air Quality Guideline (AQG) for 24-hour mean exposure. Use of wood fuels in domestic cooking is the major source of wood smoke exposure in this population. Occupational exposure to wood smoke included the use of wood fuels in bakery, fish drying, cassava processing and charcoal production. Females were exposed to higher levels of these pollutants than males of the same age range. Major determinants for higher exposure to wood smoke in SSA included use of unprocessed firewood, female gender and occupational exposure. We recorded strong and consistent associations between exposure to wood smoke and respiratory diseases including acute respiratory illness and impaired lung function. Positive associations were reported for increased blood pressure, low birth weight, oesophageal cancer, sick building syndrome, non-syndromic cleft lip and/or cleft palate and under-five mortality.

Conclusion

There is high level of exposure to wood smoke in SSA and this exposure is associated with a number of adverse health effects. There is urgent need for aggressive programs to reduce wood smoke exposure in this population.

Implications on Livelihoods and the Environment of Uptake of Gasifier Cook Stoves among Kenya’s Rural Households

A majority of people in developing countries use biomass energy for cooking and heating due to its affordability, accessibility and convenience. However, unsustainable biomass use leads to forest degradation and climate change. Therefore, this study was carried out in Kwale County, Kenya, on the use of a biochar-producing gasifier cook stove and implications of its uptake on livelihoods and the environment. Fifty households were trained and issued with a gasifier for free. After 2–3 months of gasifier use, a survey was conducted to investigate the implications of its uptake. The direct impacts included reduced fuel consumption by 38%, reduced time spent in firewood collection, reduced expenditure on cooking fuel, diversification of cooking fuels, improved kitchen conditions and reduced time spent on cooking. The potential benefits included income generation, increased food production, reduced impacts on environment and climate change and reduced health problems. Improved biomass cook stoves can alleviate problems with current cooking methods, which include inefficient fuel use, health issues caused by smoke, and environmental problems. These benefits could contribute to development through alleviating poverty and hunger, promoting gender equality, enhancing good health and sustainable ecosystems and mitigating climate change. The study recommends the promotion of cleaner cooking stoves, particularly gasifiers, among households in rural areas while paying attention to user needs and preferences.

Women and girls in resource poor countries experience much greater exposure to household air pollutants than men: Results from Uganda and Ethiopia

Household Air Pollution (HAP) from burning biomass fuels is a major cause of mortality and morbidity in low-income settings worldwide. Little is known about the differences in objective personal HAP exposure by age and gender. We measured personal exposure to HAP across six groups defined by age and gender (young children, young males, young females, adult males, adult females, and elderly) in rural households in two sub-Saharan African countries. Data on 24-hour personal exposure to HAP were collected from 215 participants from 85 households in Uganda and Ethiopia. HAP exposure was assessed by measuring carbon monoxide (CO) and/or fine particulate matter (PM_2.5) concentrations using five types of devices. 24 h PM_2.5 personal exposure was highest among adult females with Geometric Mean (GM) and Geometric Standard Deviation (GSD) concentrations of 205 μg/m³ (1.67) in Ethiopia; 177 μg/m³ (1.61 GSD) in Uganda. The lowest PM_2.5 exposures were recorded among young males GM (GSD) 30.2 μg/m³ (1.89) in Ethiopia; 26.3 μg/m³ (1.48) in Uganda. Young females had exposures about two-thirds of the adult female group. Adult males, young children and the elderly experienced lower exposures reflecting their limited involvement in cooking. There was a similar pattern of exposure by age and gender in both countries and when assessed by CO measurement. There are substantial differences in exposure to HAP depending on age and gender in sub-Saharan Africa rural households reflecting differences in household cooking activity and time spent indoors. Future work should consider these differences when implementing exposure reduction interventions. There was a strong agreement between optical and gravimetric devices measurements although optical devices tended to overestimate exposure. There is need to calibrate optical devices against a gravimetric standard prior to quantifying exposure.

Performance of low-cost monitors to assess household air pollution

Exposure to household air pollution is a leading cause of morbidity and mortality globally. However, due to the lack of validated low-cost monitors with long-lasting batteries in indoor environments, most epidemiologic studies use self-reported data or short-term household air pollution assessments as proxies of long-term exposure. We evaluated the performance of three low-cost monitors measuring fine particulate matter (PM_2.5) and carbon monoxide (CO) in a wood-combustion experiment conducted in one household of Spain for 5 days (including the co-location of 2 units of HAPEX and 3 units of TZOA-R for PM_2.5 and 3 units of EL-USB-CO for CO; a total of 40 unit-days). We used Spearman correlation (ρ) and Concordance Correlation Coefficient (CCC) to assess accuracy of low-cost monitors versus equivalent research-grade devices. We also conducted a field study in India for 1 week (including HAPEX in 3 households and EL-USB-CO in 4 households; a total of 49 unit-days). Correlation and agreement at 5-min were moderate-high for one unit of HAPEX (ρ = 0.73 / CCC = 0.59), for one unit of TZOA-R (ρ = 0.89 / CCC = 0.62) and for three units of EL-USB-CO (ρ = 0.82-0.89 / CCC = 0.66-0.91) in Spain, although the failure or malfunction rate among low-cost units was high in both settings (60% of unit-days in Spain and 43% in India). Low-cost monitors tested here are not yet ready to replace more established exposure assessment methods in long-term household air pollution epidemiologic studies. More field validation is needed to assess evolving sensors and monitors with application to health studies.