Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Residential Coal Combustion

Impaired Detoxification of Trans, Trans-2,4-Decadienal, an Oxidation Product from Omega-6 Fatty Acids, Alters Insulin Signaling, Gluconeogenesis and Promotes Microvascular Disease

Omega-6 fatty acids are the primary polyunsaturated fatty acids in most Western diets, while their role in diabetes remains controversial. Exposure of omega-6 fatty acids to an oxidative environment results in the generation of a highly reactive carbonyl species known as trans, trans-2,4-decadienal (tt-DDE). The timely and efficient detoxification of this metabolite, which has actions comparable to other reactive carbonyl species, such as 4-hydroxynonenal, acrolein, acetaldehyde, and methylglyoxal, is essential for disease prevention. However, the detoxification mechanism for tt-DDE remains elusive. In this study, the enzyme Aldh9a1b is identified as having a key role in the detoxification of tt-DDE. Loss of Aldh9a1b increased tt-DDE levels and resulted in an abnormal retinal vasculature and glucose intolerance in aldh9a1b-/- zebrafish. Transcriptomic and metabolomic analyses revealed that tt-DDE and aldh9a1b deficiency in larval and adult zebrafish induced insulin resistance and impaired glucose homeostasis. Moreover, alterations in hyaloid vasculature is induced by aldh9a1b knockout or by tt-DDE treatment can be rescued by the insulin receptor sensitizers metformin and rosiglitazone. Collectively, these results demonstrated that tt-DDE is the substrate of Aldh9a1b which causes microvascular damage and impaired glucose metabolism through insulin resistance.

Abundant oxygenated volatile organic compounds and their contribution to photochemical pollution in subtropical Hong Kong

Volatile organic compounds (VOCs), which are ubiquitous pollutants in the urban and regional atmosphere, promote the formation of ozone (O3) and secondary organic aerosols, thereby significantly affecting the air quality and human health. The ambient VOCs at a coastal suburban site in Hong Kong were continuously measured using proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) from November 2020 to December 2020. 83 VOC species, including 23 CxHy, 53 CxHyO1-3, and 7 nitrogen-containing species, were measured during the campaign, with a mean concentration of 36.75 ppb. Oxygenated VOCs (OVOCs) accounted for most (77.4%) of the measured species, including CxHyO1 (50.7%) and CxHyO2 (25.1%). The measured VOC species exhibited distinct temporal and diurnal variations. High concentrations of isoprene and OVOCs were measured in autumn with more active photochemistry, whereas large evening peaks of aromatics from local and regional primary emissions were prominent in winter. The OH reactivity and O3 formation potential (OFP) of key precursors were quantified. OVOCs contributed about half of the total OH reactivity and OFP, followed by alkenes and aromatics, and the contribution of aromatics increased significantly in winter. The potential source contribution function was used to investigate the potential source regions associated with high VOC concentrations. Through positive matrix factorization analysis, six major sources were identified based on fingerprint molecules. The contributions of biogenic sources and secondary formation to the observed species were notable in late autumn, whereas vehicle emissions and solid fuel combustion had higher contributions in winter. The findings highlight the important role of OVOCs in photochemical pollution and provide valuable insights for the development of effective pollution control strategies.

VOC emission profiles from typical solid fuel combustion in Fenhe River Basin: Field measurements and environmental implication

This study examined volatile organic compounds (VOCs) emitted from the combustion of seven typical biomass fuel types in a traditional stove, elevated kang, and biomass furnace and from the combustion of three types of coal in coal furnaces. The results revealed that emission factors (EFs) of VOCs emitted from combustion processes ranged from 48.8 ± 29.1 mg/kg (for anthracite combustion in an outdoor boiler) to 5700 ± 6040 mg/kg (for sesame straw combustion in a traditional stove). Changing the fuel type engendered a more significant EF reduction (82.7%) than changing the stove type (51.8%). The emitted VOCs (including oxygenated VOCs, OVOCs) can be ordered as follows (in descending order) in terms of proportion: OVOCs > alkenes > aromatic VOCs > alkanes > halo hydrocarbons > alkynes. These results indicate solid fuel combustion processes warrant attention because they produce high OVOC emissions. The ozone formation potential (OFP) values derived for VOCs emitted from solid fuel combustion ranged from 5.83 ± 0.72 to 1910 ± 1750 mg/kg. Clean fuel and clean stove technologies both exhibited >80% efficiency levels in reducing OFP emissions (e.g., 80.6% reduction for the optimal fuel; 89.4% reduction for a clean stove). Therefore, the difference between VOC emission profiles from different combustion technologies should not be ignored. This study also noted substantial differences between VOC emissions from residential combustion and industrial combustion. Accordingly, attention should be paid to the local characteristics of fuels and stoves and to VOC emissions from residential combustion.

Emission factors and chemical profile of I/SVOCs emitted from household biomass stove in China

Household combustion of biomass straw for cooking or heating is one of the most important emission sources of intermediate volatility and semi-volatile organic compounds (I/SVOCs). However, there are limited studies on the emission factors (EFs) and speciation profiles of I/SVOCs from household stoves burning biomass straw. In this study, experiments were conducted in a typical Chinese stove to test the EFs and species of I/SVOCs in three commonly used straws. It was revealed that EFs of I/SVOCs emitted from the burning of corn straw, rice straw, and wheat straw were 6.7, 1.9, and 9.8 g/kg, respectively, which accounted for 48.3 %, 36.8 %, and 48.6 % of total organic compounds emitted. Particulate organic compounds were dominated by ketones, oxygenated aromatics, acids, esters, and nitrogen-containing compounds, whereas the gaseous phase was dominated by aldehydes, acids, and aromatics. Although I/SVOCs only accounted for 18.1-23.6 % of the gaseous emissions from burning of straw, they represented 64.8-72.9 % of the secondary organic aerosol formation potential (SOAFP). The EFs of 16 priority polycyclic aromatic hydrocarbons (PAHs) were 362.0, 262.5, and 1145.2 mg/kg for corn straw, rice straw, and wheat straw, respectively, among which 3-ring and 4-ring PAHs were the main components. Thus, the results of this study provide new reliable I/SVOCs data that are useful for the development of an accurate emission inventory of organic compounds, simulation of secondary organic aerosol (SOA) formation, and health risk assessment.

Volatile organic compounds in wintertime North China Plain: Insights from measurements of proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS)

The characteristics of wintertime volatile organic compounds (VOCs) in the North China Plain (NCP) region are complicated and remain obscure. VOC measurements were conducted by a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) at a rural site in the NCP from November to December 2018. Uncalibrated ions measured by PTR-ToF-MS were quantified and the overall VOC compositions were investigated by combining the measurements of PTR-ToF-MS and gas chromatography-mass spectrometer/flame ionization detector (GC-MS/FID). The measurement showed that although atmospheric VOCs concentrations are often dominated by primary emissions, the secondary formation of oxygenated VOCs (OVOCs) is non-negligible in the wintertime, i.e., OVOCs accounts for 42% ± 7% in the total VOCs (151.3 ± 75.6 ppbV). We demonstrated that PTR-MS measurements for isoprene are substantially overestimated due to the interferences of cycloalkanes. The chemical changes of organic carbon in a pollution accumulation period were investigated, which suggests an essential role of fragmentation reactions for large, chemically reduced compounds during the heavy-polluted stage in wintertime pollution. The changes of emission ratios of VOCs between winter 2011 and winter 2018 in the NCP support the positive effect of "coal to gas" strategies in curbing air pollutants. The high abundances of some key species (e.g. oxygenated aromatics) indicate the strong emissions of coal combustion in wintertime of NCP. The ratio of naphthalene to C8 aromatics was proposed as a potential indicator of the influence of coal combustion on VOCs.

Effects of pH on light absorption properties of water-soluble organic compounds in particulate matter emitted from typical emission sources

Water-soluble organic compounds (WSOC) have a significant impact on aerosol radiative forcing and climate change, and there is considerable uncertainty in predicting and mitigating their climate and environmental effects. Here, the effects of pH on the light absorption properties of WSOC in particulate matter from different typical emission sources and ambient aerosols were systematically investigated using UV-vis spectrophotometer. pH (2-10) had an important impact on the light absorption properties of WSOC. The absorption, aromaticity, and the light absorption capacity of WSOC increased significantly with increasing pH for all samples. The difference absorbance spectra (∆absorbance) showed that the change of light absorption properties with pH was related to the deprotonate of carboxyl and phenolic groups resonating with aromatic and conjugated systems, with the most likely structures being carboxylic acids and phenols. Coal combustion and summer samples exhibited much higher susceptibility of light absorption properties to pH variation (increased by 27.0% and 65.9% relative to the pH 2 level, respectively). Absorption indices of almost all samples were significantly correlated with pH, indicating that the light absorption properties of WSOC may be quantitatively related to pH. The pH-dependent light absorption properties may have profound implications for evaluating the climate impacts of aerosol WSOC such as radiative forcing.

Ethanol-based disinfectant sprays drive rapid changes in the chemical composition of indoor air in residential buildings

The COVID-19 pandemic has resulted in increased usage of ethanol-based disinfectants for surface inactivation of SARS-CoV-2 in buildings. Emissions of volatile organic compounds (VOCs) and particles from ethanol-based disinfectant sprays were characterized in real-time (1 Hz) via a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) and a high-resolution electrical low-pressure impactor (HR-ELPI+), respectively. Ethanol-based disinfectants drove sudden changes in the chemical composition of indoor air. VOC and particle concentrations increased immediately after application of the disinfectants, remained elevated during surface contact time, and gradually decreased after wiping. The disinfectants produced a broad spectrum of VOCs with mixing ratios spanning the sub-ppb to ppm range. Ethanol was the dominant VOC emitted by mass, with concentrations exceeding 103 μg m-3 and emission factors ranging from 101 to 102 mg g-1. Listed and unlisted diols, monoterpenes, and monoterpenoids were also abundant. The pressurized sprays released significant quantities (104-105 cm-3) of nano-sized particles smaller than 100 nm, resulting in large deposited doses in the tracheobronchial and pulmonary regions of the respiratory system. Inhalation exposure to VOCs varied with time during the building disinfection events. Much of the VOC inhalation intake (>60 %) occurred after the disinfectant was sprayed and wiped off the surface. Routine building disinfection with ethanol-based sprays during the COVID-19 pandemic may present a human health risk given the elevated production of volatile chemicals and nano-sized particles.

Intermediate Volatile Organic Compound Emissions from Residential Solid Fuel Combustion Based on Field Measurements in Rural China

Residential solid fuel combustion (RSFC) is a key cause of air pollution in China. In these serial studies, field measurements of RSFC from 166 rural households in eastern China were conducted to update the database of emission factors (EFs) and chemical profiles of gaseous and particulate organic pollutants, and the present study focuses on the intermediate volatile organic compounds (IVOCs), which are precursors of secondary organic aerosol (SOA). The results show that the averaged EFs of IVOCs (EF_IVOC) for crop straw, fuelwood, and coal are 550.7 ± 397.9, 416.1 ± 249.5, and 361.9 ± 308.0 mg/kg, respectively, which are among the EF_IVOC of gasoline vehicle, diesel vehicle, non-road machinery, and heavy fuel oil vessel, and are significantly affected by fuel, stove, and combustion efficiency. The percentages of normal alkanes (n-alkanes), branched alkanes (b-alkanes), polycyclic aromatic hydrocarbons (PAHs), and unresolved complex mixture from RSFC are 3.5 ± 1.6, 8.0 ± 3.7, 17.6 ± 6.7, and 70.9 ± 8.1%, respectively, and the compositions are featured by lower b-alkanes and higher PAHs than those of vehicle sources. The proportions of some individual n-alkanes and PAHs (such as n-C₁₂-n-C₁₅, naphthalene, and its alkyl substituents) can be used as indicators to differentiate RSFC from vehicle sources, while methoxyphenols can be used to distinguish biomass burning from coal combustion. Based on China's energy statistics, the total IVOC emissions from RSFC in 2014 were 175.9 Gg. These data will help to update the IVOC emission inventory and improve the estimates of SOA production in China.

Brown Carbon in Primary and Aged Coal Combustion Emission

Smog chamber experiments were conducted to characterize the light absorption of brown carbon (BrC) from primary and photochemically aged coal combustion emissions. Light absorption was measured by the UV-visible spectrophotometric analysis of water and methanol extracts of filter samples. The single-scattering albedo at 450 nm was 0.73 ± 0.10 for primary emissions and 0.75 ± 0.13 for aged emissions. The light absorption coefficient at 365 nm of methanol extracts was higher than that of water extracts by a factor of 10 for primary emissions and a factor of 7 for aged emissions. This suggests that the majority of BrC is water-insoluble even after aging. The mass absorption efficiency of this BrC (MAE₃₆₅) for primary OA (POA) was dependent on combustion conditions, with an average of 0.84 ± 0.54 m² g^-1, which was significantly higher than that for aged OA (0.24 ± 0.18 m² g^-1). Secondary OA (SOA) dominated aged OA and the decreased MAE₃₆₅ after aging indicates that SOA is less light absorbing than POA and/or that BrC is bleached (oxidized) with aging. The estimated MAE₃₆₅ of SOA (0.14 ± 0.08 m² g^-1) was much lower than that of POA. A comparison of MAE₃₆₅ of residential coal combustion with other anthropogenic sources suggests that residential coal combustion emissions are among the strongest absorbing BrC organics.

Identifying Volatile Chemical Product Tracer Compounds in U.S. Cities

With traffic emissions of volatile organic compounds (VOCs) decreasing rapidly over the last decades, the contributions of the emissions from other source categories, such as volatile chemical products (VCPs), have become more apparent in urban air. In this work, in situ measurements of various VOCs are reported for New York City, Pittsburgh, Chicago, and Denver. The magnitude of different emission sources relative to traffic is determined by measuring the urban enhancement of individual compounds relative to the enhancement of benzene, a known tracer of fossil fuel in the United States. The enhancement ratios of several VCP compounds to benzene correlate well with population density (R² ∼ 0.6-0.8). These observations are consistent with the expectation that some human activity should correlate better with the population density than transportation emissions, due to the lower per capita rate of driving in denser cities. Using these data, together with a bottom-up fuel-based inventory of vehicle emissions and volatile chemical products (FIVE-VCP) inventory, we identify tracer compounds for different VCP categories: decamethylcyclopentasiloxane (D5-siloxane) for personal care products, monoterpenes for fragrances, p-dichlorobenzene for insecticides, D4-siloxane for adhesives, para-chlorobenzotrifluoride (PCBTF) for solvent-based coatings, and Texanol for water-based coatings. Furthermore, several other compounds are identified (e.g., ethanol) that correlate with population density and originate from multiple VCP sources. Ethanol and fragrances are among the most abundant and reactive VOCs associated with VCP emissions.

Assessment of kitchen emissions using a backpropagation neural network model based on urinary hydroxy polycyclic aromatic hydrocarbons

Kitchen emissions are mixed indoor air pollutants with adverse health effects, but the large-scale assessment is limited by costly equipment and survey methods. This study aimed to discuss the application of backpropagation (BP) neural network models in the assessment of kitchen emissions based on the exposure marker. A total of 3686 participants were recruited for the kitchen survey, and their sleep quality was measured by the Pittsburgh sleep quality index (PSQI). After excluding the confounders, 365 participants were selected to assess their urinary hydroxy polycyclic aromatic hydrocarbons (OH-PAHs) concentrations by ultra-high-performance liquid chromatography/tandem mass spectrometry. Two BP neural network models were then set up using the survey and detection data from the 365 participants and used to predict the total urinary OH-PAHs concentrations of all participants. The total urinary OH-PAHs and 1-hydroxy-naphthalene (1-OHNap) concentrations were significantly higher among the 365 participants with poor sleep quality (global PSQI score > 5; P < 0.05). Results from internal and external validation showed that our model has high credibility (model 2). Further, the participants with higher predicted total urinary OH-PAHs concentrations were associated with the global PSQI score of >5 (odds ratio (OR) = 1.284, 95% confidence interval (CI) = 1.082-1.525 for participants with predicted total urinary OH-PAHs concentrations of over 1.897 μg/mmol creatinine in model 1, and OR = 1.467, 95% CI = 1.240-1.735 for participants with predicted total urinary OH-PAHs concentrations of over 2.253 μg/mmol creatinine in model 2) after adjusting for the confounders. Findings suggest that the BP neural network model is suitable for assessing kitchen emissions, and the urinary OH-PAHs concentrations can be taken as the model outlay.

Spatial and temporal distribution characteristics and ozone formation potentials of volatile organic compounds from three typical functional areas in China

BACKGROUND

Ozone is currently one of the most important air pollutants. Volatile organic compounds (VOCs) can easily react with atmospheric radicals to form ozone. In-field measurement of VOCs may help in estimating the local VOC photochemical pollution level.

METHOD

This study examined the spatial and temporal distribution characteristics of VOCs during winter at three typical sites of varying classification in China; industrial (Guangzhou Economic and Technological Development District (GETDD)), urban (Guangzhou higher education mega center (HEMC)), and rural (Pingyuan county (PYC)), using Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS).

RESULTS

The concentrations of total VOCs (TVOCs) at the GETDD, HEMC and PYC sites were 352.5, 129.2 and 75.1 ppb, respectively. The dominant category of VOCs is nitrogen-containing VOCs (NVOCs, accounting for 43.3% of TVOCs) at GETDD, of which C₄H₁₁N (m/z⁺ = 74.10, butyl amine) was the predominant chemical species (80.5%). In contrast, oxygenated VOCs (OVOCs) were the most abundant at HEMC and PYC, accounting for 60.2% and 64.1% of the total VOCs, respectively; here, CH₄O (m/z⁺ = 33.026, methanol) was the major compound, accounting for 40.5% of the VOCs at HEMC and 50.9% at PYC. The ratios of toluene to benzene (T/B) were calculated for different measured sites, as the ratios of T/B can reveal source resolution of aromatic VOCs. The average contributions to total ozone formation potentials (OFP) of the total measured VOCs in each area were 604.9, 315.9 and 111.7 μg/m³ at GETDD, HEMC and PYC, respectively; the highest OFP contributors of the identified VOCs were aliphatic hydrocarbons (AlHs) at GETDD, aromatic hydrocarbons (AHs) at HEMC, and OVOCs at PYC.

CONCLUSIONS

OFP assessment indicated that the photochemical pollution caused by VOCs at GETDD was serious, and was also significant in the HEMC region. The dominant VOC OFP groups (AlHs and AHs) should be prioritized for control, in order to help reduce these effects.

Characterization and sources of volatile organic compounds (VOCs) and their related changes during ozone pollution days in 2016 in Beijing, China

Concentrations of 99 volatile organic compounds (VOCs) were continuously measured online at an urban site in Beijing, China, in January, April, July, and October 2016. Characterization and sources of VOCs and their related changes during days with heavy ozone (O₃) pollution were analysed. The total observed concentration of VOCs (TVOCs) was 44.0 ± 28.9 ppbv. The VOC pollution level has decreased in Beijing but remains higher than in other Chinese cities. Alkanes comprised the highest proportion among seven major sampled VOC groups. The concentrations and sources of ambient VOCs showed obvious temporal variations. Six emission sources were identified by the positive matrix factorization (PMF), including biomass burning, coal combustion, gasoline vehicles, diesel vehicles, solvent usage, and biogenic + secondary emissions. The combustion source was the key control factor for VOC reduction in Beijing. From the potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) model, Beijing, Tianjin, Hebei, Shanxi, Inner Mongolia, Shandong, and Henan were identified as major potential source regions of ambient VOCs. O₃ formation was sensitive to VOCs in Beijing according to the VOC/NOx ratio (ppbC/ppbv, 8:1 threshold). High- and low-O₃ days in July were identified, and high O₃ levels were due to both enhanced VOC emission levels and meteorological conditions favourable to the production of O₃. These findings provide evidence that the fuel combustion and regional transport have a great impact on concentrations and sources of VOCs in urban Beijing.

Volatile organic compounds emissions from traditional and clean domestic heating appliances in Guanzhong Plain, China: Emission factors, source profiles, and effects on regional air quality

Solid (biomass and coal) fuels burned for residential heating are major sources of atmospheric volatile organic compounds (VOCs). In this study, VOC samples were collected in-situ from chimneys in 10 typical heating scenarios in rural areas of the Guanzhong Plain. A modified SUMA canister approach was then employed, followed by gas chromatography/mass spectrometry analysis. Emission factors (EFs) (as received basis) of targeted non-methane VOCs (NMVOCs) varied from 90.3 ± 29.3 to 12300 ± 1510 mg kg^-1 in descending order of fuel wood > maize straw > bitumite ≫ anthracite (p < 0.05). Both clean stove and coal briquetting technologies effectively reduced VOC EFs compared with traditional heating methods. The EFs of methane (CH₄) had similar characteristics to those of NMVOCs. However, they yielded different correlations with CO because of their differing mechanisms of formation. Coefficient of divergence (CD) values showed that a semi-gasifier has a limited effect on changing VOC profiles compared with a traditional stove using the same fuels. However, different types of fuel produce CD values over 0.50, which should therefore be classified as different sub-categories in source apportionment models. Correlation analysis showed that volatile matter content (V%) and modified combustion efficiency (MCE) were the two primary factors influencing NMVOC and CH₄ emissions. A stepwise linear regression analysis showed that V%, MCE, and element nitrogen content (N%) can be used to predict total VOC (TVOCs, including CH₄ and NMVOCs) emissions with regression coefficients of 0.23, -72.8 and -6.53, respectively (R² = 0.92, p < 0.001). Ozone formation potential (OFP) EFs from burning solid fuel ranged from 72 to 18680 mg kg^-1, with an approximate 50% contribution from alkenes. VOCs from burning solid fuel were equivalent to 62 to 22200 mg kg^-1 secondary organic aerosol formation potential (SOAP), most of which (>95%) were contributed by aromatics. A semi-gasifier and coal briquettes were effective in reducing TVOC emissions, even when used in conjunction with a traditional stove and fuels. It is estimated that over 15,000 ton year^-1 emissions can be reduced in Guanzhong Plain by adopting a semi-gasifier and coal briquettes, resulting in a 57,000 and 65,000 ton year^-1 reduction of OFP and SOAP emissions, respectively. These results demonstrate that the use of clean heating technologies in Guanzhong Plain has considerable potential in relation to emissions reduction and thus provides a feasible solution to mitigate VOCs and related secondary pollutants emitted by residential solid fuel burning.

Time-Resolved Intermediate-Volatility and Semivolatile Organic Compound Emissions from Household Coal Combustion in Northern China

Coal combustion in low-efficiency household stoves results in the emission of large amounts of nonmethane organic compounds (NMOCs), including intermediate-volatility compounds (IVOCs) and semivolatile organic compounds (SVOCs). This conceptual picture is reasonably well established, however, quantitative assessment of I/SVOC emissions from household stoves is rare. We used a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) to quantify the emissions of organic gases from a typical Chinese household coal stove operated with anthracite and bituminous coals. Most NMOCs (approximately 64-88%) were dominated by hydrocarbons and emitted during the ignition and flaming phases. The ratio of oxidized hydrocarbons increased during the flaming and smoldering stages due to the elevated combustion efficiency. The average emission factors of NMOCs were 121 ± 25.7 and 3690 ± 930 mg/kg for anthracite and bituminous coals, respectively. I/SVOCs contributed to approximately 30% of the total emitted NMOC mass during bituminous coal combustion, much higher than the contribution of biomass burning (approximately 1.5%). Furthermore, I/SVOCs may contribute over 70% of the secondary organic aerosol (SOA) mass formed from gaseous organic species emitted as a result of bituminous coal combustion. This study highlights the importance of inventorying coal-originated I/SVOCs when conducting SOA formation simulation studies.

A Laboratory Assessment of 120 Air Pollutant Emissions from Biomass and Fossil Fuel Cookstoves

Cookstoves emit many pollutants that are harmful to human health and the environment. However, most of the existing scientific literature focuses on fine particulate matter (PM2.5) and carbon monoxide (CO). We present an extensive data set of speciated air pollution emissions from wood, charcoal, kerosene, and liquefied petroleum gas (LPG) cookstoves. One-hundred and twenty gas- and particle-phase constituents-including organic carbon, elemental carbon (EC), ultrafine particles (10-100 nm), inorganic ions, carbohydrates, and volatile/semivolatile organic compounds (e.g., alkanes, alkenes, alkynes, aromatics, carbonyls, and polycyclic aromatic hydrocarbons (PAHs))-were measured in the exhaust from 26 stove/fuel combinations. We find that improved biomass stoves tend to reduce PM2.5 emissions; however, certain design features (e.g., insulation or a fan) tend to increase relative levels of other coemitted pollutants (e.g., EC ultrafine particles, carbonyls, or PAHs, depending on stove type). In contrast, the pressurized kerosene and LPG stoves reduced all pollutants relative to a traditional three-stone fire (≥93% and ≥79%, respectively). Finally, we find that PM2.5 and CO are not strong predictors of coemitted pollutants, which is problematic because these pollutants may not be indicators of other cookstove smoke constituents (such as formaldehyde and acetaldehyde) that may be emitted at concentrations that are harmful to human health.