Fate of Exhaled Droplets From Breathing and Coughing in Supermarket Checkouts and Passenger Cars.

The global pandemic of COVID-19 has highlighted the importance of understanding the role that exhaled droplets play in virus transmission in community settings. Computational Fluid Dynamics (CFD) enables systematic examination of roles the exhaled droplets play in the spread of SARS-CoV-2 in indoor environments. This analysis uses published exhaled droplet size distributions combined with terminal aerosol droplet size based on measured peak concentrations for SARS-CoV-2 RNA in aerosols to simulate exhaled droplet dispersion, evaporation, and deposition in a supermarket checkout area and rideshare car where close proximity with other individuals is common. Using air inlet velocity of 2 m/s in the passenger car and ASHRAE recommendations for ventilation and comfort in the supermarket, simulations demonstrate that exhaled droplets <20 µm that contain the majority of viral RNA evaporated leaving residual droplet nuclei that remain aerosolized in the air. Subsequently ~ 70% of these droplet nuclei deposited in the supermarket and the car with the reminder vented from the space. The maximum surface deposition of droplet nuclei/m2 for speaking and coughing were 2 and 819, 18 and 1387 for supermarket and car respectively. Approximately 15% of the total exhaled droplets (aerodynamic diameters 20-700 µm) were deposited on surfaces in close proximity to the individual. Due to the non-linear distribution of viral RNA across droplet sizes, however, these larger exhaled droplets that deposit on surfaces have low viral content. Maximum surface deposition of viral RNA was 70 and 1.7 × 103 virions/m2 for speaking and 2.3 × 104 and 9.3 × 104 virions/m2 for coughing in the supermarket and car respectively while the initial airborne concentration of viral RNA was 7 × 106 copies per ml. Integrating the droplet size distributions with viral load distributions, this study helps explain the apparent importance of inhalation exposures compared to surface contact observed in the pandemic.

Emissions Measurements from Household Solid Fuel Use in Haryana, India: Implications for Climate and Health Co-benefits.

A large concern with estimates of climate and health co-benefits of "clean" cookstoves from controlled emissions testing is whether results represent what actually happens in real homes during normal use. A growing body of evidence indicates that in-field emissions during daily cooking activities differ substantially from values obtained in laboratories, with correspondingly different estimates of co-benefits. We report PM2.5 emission factors from uncontrolled cooking (n = 7) and minimally controlled cooking tests (n = 51) using traditional chulha and angithi stoves in village kitchens in Haryana, India. Minimally controlled cooking tests (n = 13) in a village kitchen with mixed dung and brushwood fuels were representative of uncontrolled field tests for fine particulate matter (PM2.5), organic and elemental carbon (p > 0.5), but were substantially higher than previously published water boiling tests using dung or wood. When the fraction of nonrenewable biomass harvesting, elemental, and organic particulate emissions and modeled estimates of secondary organic aerosol (SOA) are included in 100 year global warming commitments (GWC100), the chulha had a net cooling impact using mixed fuels typical of the region. Correlation between PM2.5 emission factors and GWC (R2 = 0.99) implies these stoves are climate neutral for primary PM2.5 emissions of 8.8 ± 0.7 and 9.8 ± 0.9 g PM2.5/kg dry fuel for GWC20 and GWC100, respectively, which is close to the mean for biomass stoves in global emission inventories.

Emission Measurements from Traditional Biomass Cookstoves in South Asia and Tibet.

Traditional biomass stoves are a major global contributor to emissions that impact climate change and health. This paper reports emission factors of particulate matter (PM2.5), carbon monoxide (CO), organic carbon (OC), black carbon (EC), optical absorption, and scattering from 46 South Asian, 48 Tibetan, and 4 Ugandan stoves. These measurements plus a literature review provide insight into the robustness of emission factors used in emission inventories. Tibetan dung stoves produced high average PM2.5 emission factors (23 and 43 gkg-1 for chimney and open stoves) with low average EC (0.3 and 0.7 gkg-1, respectively). Comparatively, PM2.5 from South Asian stoves (7 gkg-1) was in the range of previous measurements and near values used in inventories. EC emission factors varied between stoves and fuels ( p < 0.001), without corresponding differences in absorption; stoves that produced little EC, produced enough brown carbon to have about the same absorption as stoves with high EC emissions. In Tibetan dung stoves, for example, OC contributed over 20% of the absorption. Overall, EC emission factors were not correlated with PM2.5 and were constrained to low values, relative to PM2.5, over a wide range of combustion conditions. The average measured EC emission factor (1 gkg-1), was near current inventory estimates.

Field Emission Measurements of Solid Fuel Stoves in Yunnan, China Demonstrate Dominant Causes of Uncertainty in Household Emission Inventories.

Emission factors of carbon monoxide (CO), particulate matter (PM2.5), organic carbon (OC), and elemental carbon (EC), as well as combustion efficiency and particle optical properties were measured during 37 uncontrolled cooking tests of residential stoves in Yunnan Province, China. Fuel mixtures included coal, woody biomass, and agricultural waste. Compared to previously published emission measurements of similar stoves, these measurements have higher CO and PM2.5 emission factors. Real-time data show two distinct burn phases: a devolatilization phase after fuel addition with high PM2.5 emissions and a solid-fuel combustion phase with low PM2.5 emissions. The average emission factors depend on the relative contributions of these phases, which are affected by the services provided by the stoves. Differences in stove and fuel characteristics that are not represented in emission inventories affect the variability of emission factors much more than do the type of solid fuel or stove. In developing inventories with highly variable sources such as residential solid-fuel combustion, we suggest that (1) all fuels should be accounted for, not just the primary fuel; (2) the household service provided should be emphasized rather than specific combinations of solid fuels and devices; and (3) the devolatilization phase should be explicitly measured and represented.

Fugitive Emissions and Health Implications of Plancha-Type Stoves.

Plancha-type stoves have been widely disseminated in Mexico and Central America, but the contribution of fugitive emissions from these stoves to indoor air concentrations has been poorly quantified. In this study, fugitive emissions were measured for four plancha-type cookstoves most disseminated in Mexico (Patsari, ONIL, Ecostufa, and Mera-Mera). In controlled testing, fugitive emissions from plancha-type chimney stoves ( n = 15 for each stove) were on average 5 ± 3% for PM2.5 and 1 ± 1% for CO, much lower than defaults in WHO Guidelines (25 ± 10%). Using a Monte Carlo single zone model with locally measured parameters, average kitchen concentrations resulting from fugitive emissions were 15 ± 9 µg/m3 for PM2.5 and 0.06 ± 0.04 mg/m3 for CO. On the basis of these models, plancha-type stoves meet benchmarks for WHO Air Quality Guidelines (AQG) Interim Target I for PM2.5 and the 24 h AQG for CO, respectively, with on average 97% of homes meeting the guideline for PM2.5. Similarly, all four plancha-type stoves were ISO IWA Tier 4 for indoor emissions of CO and Tier 3 for indoor emissions of PM2.5. Three-dimensional computational fluid dynamics (CFD) analysis was used to estimate neighborhood pollution impacts of upstream chimney emissions. When chimney emissions were included as background concentrations combined with indoor contributions from fugitive emissions, plancha-type stoves would still meet the WHO AQG Annual Interim Target I for PM2.5 and the 24 h AQG for CO for the scenario modeled in this study.

Health assessment of future PM2.5 exposures from indoor, outdoor, and secondhand tobacco smoke concentrations under alternative policy pathways in Ulaanbaatar, Mongolia.

INTRODUCTION: Winter air pollution in Ulaanbaatar, Mongolia is among the worst in the world. The health impacts of policy decisions affecting air pollution exposures in Ulaanbaatar were modeled and evaluated under business as usual and two more-strict alternative emissions pathways through 2024. Previous studies have relied on either outdoor or indoor concentrations to assesses the health risks of air pollution, but the burden is really a function of total exposure. This study combined projections of indoor and outdoor concentrations of PM2.5 with population time-activity estimates to develop trajectories of total age-specific PM2.5 exposure for the Ulaanbaatar population. Indoor PM2.5 contributions from secondhand tobacco smoke (SHS) were estimated in order to fill out total exposures, and changes in population and background disease were modeled. The health impacts were derived using integrated exposure-response curves from the Global Burden of Disease Study. RESULTS: Annual average population-weighted PM2.5 exposures at baseline (2014) were estimated at 59 µg/m3. These were dominated by exposures occurring indoors, influenced considerably by infiltrated outdoor pollution. Under current control policies, exposures increased slightly to 60 µg/m3 by 2024; under moderate emissions reductions and under a switch to clean technologies, exposures were reduced from baseline levels by 45% and 80%, respectively. The moderate improvement pathway decreased per capita annual disability-adjusted life year (DALY) and death burdens by approximately 40%. A switch to clean fuels decreased per capita annual DALY and death burdens by about 85% by 2024 with the relative SHS contribution increasing substantially. CONCLUSION: This study demonstrates a way to combine estimated changes in total exposure, background disease and population levels, and exposure-response functions to project the health impacts of alternative policy pathways. The resulting burden analysis highlights the need for aggressive action, including the elimination of residential coal burning and the reduction of current smoking rates.

Small, Smart, Fast, and Cheap: Microchip-Based Sensors to Estimate Air Pollution Exposures in Rural Households.

Over the last 20 years, the Kirk R. Smith research group at the University of California Berkeley-in collaboration with Electronically Monitored Ecosystems, Berkeley Air Monitoring Group, and other academic institutions-has developed a suite of relatively inexpensive, rugged, battery-operated, microchip-based devices to quantify parameters related to household air pollution. These devices include two generations of particle monitors; data-logging temperature sensors to assess time of use of household energy devices; a time-activity monitoring system using ultrasound; and a CO2-based tracer-decay system to assess ventilation rates. Development of each system involved numerous iterations of custom hardware, software, and data processing and visualization routines along with both lab and field validation. The devices have been used in hundreds of studies globally and have greatly enhanced our understanding of heterogeneous household air pollution (HAP) concentrations and exposures and factors influencing them.

Promoting smoke-free homes: a novel behavioral intervention using real-time audio-visual feedback on airborne particle levels.

Interventions are needed to protect the health of children who live with smokers. We pilot-tested a real-time intervention for promoting behavior change in homes that reduces second hand tobacco smoke (SHS) levels. The intervention uses a monitor and feedback system to provide immediate auditory and visual signals triggered at defined thresholds of fine particle concentration. Dynamic graphs of real-time particle levels are also shown on a computer screen. We experimentally evaluated the system, field-tested it in homes with smokers, and conducted focus groups to obtain general opinions. Laboratory tests of the monitor demonstrated SHS sensitivity, stability, precision equivalent to at least 1 µg/m(3), and low noise. A linear relationship (R(2) = 0.98) was observed between the monitor and average SHS mass concentrations up to 150 µg/m(3). Focus groups and interviews with intervention participants showed in-home use to be acceptable and feasible. The intervention was evaluated in 3 homes with combined baseline and intervention periods lasting 9 to 15 full days. Two families modified their behavior by opening windows or doors, smoking outdoors, or smoking less. We observed evidence of lower SHS levels in these homes. The remaining household voiced reluctance to changing their smoking activity and did not exhibit lower SHS levels in main smoking areas or clear behavior change; however, family members expressed receptivity to smoking outdoors. This study established the feasibility of the real-time intervention, laying the groundwork for controlled trials with larger sample sizes. Visual and auditory cues may prompt family members to take immediate action to reduce SHS levels. Dynamic graphs of SHS levels may help families make decisions about specific mitigation approaches.

Investigation of roadside fine particulate matter concentration surrounding major arterials in five Southern Californian cities.

The built environment surrounding arterials affects the dispersion of vehicular emissions in urban areas, modifying the potential risks to public health. In order to study the influence of urban morphometry on flow and dispersion of vehicular fine particulate matter emissions, in the summer of 2008 field measurements were performed in major arterials located in five Southern Californian cities with different building geometries. In each city, local mean wind, turbulence, virtual temperature, roadside DustTrak Fine Particles (DTFP) concentration, and traffic flow data were collected in 2-hr measurement periods during morning and evening rush hours and lighter midday traffic, over a period of 3 days. The calculated Monin-Obukhov length, L, suggests that near-neutral and slightly unstable conditions were present at both street and roof levels. The nondimensional forms of turbulent wind and temperature fluctuations show,that the data at street level within the urban canopy can be represented using the Monin-Obukhov similarity theory. Generalized additive models were applied to analyze the impact of meteorological and traffic-related variables on fine particle concentrations at street level Compared to other variables, urban-scale background concentrations were the most important variables in all five models. The results confirmed that turbulent mixing in urban areas dominated the variation of roadside particle concentrations regardless of urban geometry. The distance from the local sites to the nearby monitoring stations affected model performance when urban-scale concentrations were used to predict middle-scale concentrations by generalized additive models (GAMs). A radius ofinfluence for background concentrations was 6-10 km. There were also relationships between concentration and other variables affecting the local components of the concentrations, such as wind direction, sensible heat flux, and vertical wind fluctuation, although the influences were much weaker Implications: The built environment surrounding major arterials affects the dispersion of vehicular emissions in urban areas, modifying the potential risks to public health. Dispersion of pollutants within the urban canopy is governed by flow and turbulence characteristics caused by building morphometry. Current dispersion models used for regulatory purposes have difficulties simulating the flow and dispersion for complex building cases, especially when fine resolution is needed. Urban planning strategies, such as limitation of building height, pedestrian-friendly community design, or zoning of building structures, modify concentrations of vehicular emissions in built environments surrounding major arterials, which may modify health risks for adjacent communities.

A low-cost particle counter as a realtime fine-particle mass monitor.

Exposure to particles with aerodynamic diameters less than 2.5 µm is estimated to cause significant morbidity and mortality worldwide leading many countries to develop ambient air pollution standards and guidelines. At local scales, community and environmental justice groups are also concerned about PM 2.5 concentrations that may be elevated above regional concentrations typically measured by centrally located monitors and standards as well. In an attempt to develop a low cost, easy to use monitor we evaluated a low-cost optical particle counter, the Dylos™, as a fine particulate mass sensor. Modified into a system called the Berkeley Aerosol Information Recording System (BAIRS), we compared performance against standard commercial instruments in chambers using polystyrene latex spheres, ammonium sulphate, and woodsmoke and in an urban ambient setting. Overall we find that the limit of detection of the BAIRS is less than 1 µg m (-3) and the resolution is better than 1 µg m(-3) for PM 2.5. The BAIRS sizes small (<0.5 µm) particles, and is able to accurately estimate the mass concentration of particles of varying composition including organic, inorganic, and ambient particles. It is able to measure concentrations up to 10.0 mg m (-3). In an ambient roof-top test of the BAIRS and a more expensive commercially available light scattering particle monitor the BAIRS response tracked well with the commercial monitor and daily means were within 80% of each other. We conclude that with appropriate modification the system could be developed into an accurate low cost realtime particle mass monitor for use in a wide range of applications.

Global burden of disease as a result of indoor air pollution in Shaanxi, Hubei and Zhejiang, China.

Indoor air pollution in developing countries is a major global health problem, yet estimates of the global burden of disease vary widely and are associated with large uncertainty. The World Health Organization uses the fuel based approach to estimate 1.6 million premature deaths globally each year associated with exposure to indoor air pollution, of which 420000 are in China. The fuel based approach uses a ventilation factor to account for differences in indoor air concentrations and exposures in different parts of the world based on regional differences in stove technology. In China this approach assumes that flues eliminate the majority of indoor air pollution, with a ventilation factor of 0.25. To account for historic exposure leading to current disease patterns the ventilation factor was adjusted to 0.5 for adult health endpoints. Measurements in three Chinese provinces, Shaanxi, Hubei and Zhejiang, however, show that high PM(4) concentrations are present in kitchens and living rooms even with stoves with flues as a result of multiple stove and flue use. Comparison of Indian and Chinese indoor air concentrations suggests more appropriate ventilation factors in the range 0.76-1.0 for women and children, and 1.0 for men. Premature mortality in the three provinces using these estimates would be closer to 60600, rather than current estimates of 46000. With the addition of cardiovascular diseases these estimates would increase by 92000. Pollutant based estimates using measured indoor air concentrations and combined with dose-response estimates would imply a burden of disease of 157800 premature deaths including cardiovascular diseases, a tripling of current estimates.

Spatial analysis of bioavailable soil lead concentrations in Los Angeles, California.

Lead (Pb) poisoning causes permanent neurologic and developmental disorders and remains an important environmental health problem for US children, despite removal of Pb from gasoline and household paints. To better understand the contribution of Pb from historical traffic and residential Pb based paint to soil Pb concentrations in Los Angeles, we analyzed 550 soil Pb samples from south central Los Angeles County, CA, in relation to land-use patterns (commercial, industrial, residential, and parks and open areas) and proximity to freeways, highways, and major arterials. House age variables (surrogates of historical Pb-based paint) and traffic index variables (surrogates of historical traffic) were created at different buffer distances (10-5000m). Total and bioavailable Pb concentrations near freeways and major arterials were significantly higher than those collected elsewhere. Total and bioavailable Pb concentrations were highly correlated (r=0.96) after the removal of one outlier. Both parcel-age related variables and traffic variables were important predictors of current soil bioavailable Pb concentrations. Average age of parcels within 30m and length of small streets within 3000m explained 57% and 38% of the variance, respectively, in soil bioavailable Pb concentrations in residential areas away from freeways and major arterials (N=44). Road length of freeways within 750m explained 28% of bioavailable Pb concentrations in parks and open areas (N=26). Multi-variable regression models predicted 16-61% of the variances in bioavailable Pb concentrations, depending on land-use type and spatial relationship to roadways. Based on these models a map of spatial distributions of soil Pb concentrations was created for the Los Angeles area that shows promise as a screening tool to evaluate continued Pb poisoning in children.

Personal child and mother carbon monoxide exposures and kitchen levels: methods and results from a randomized trial of woodfired chimney cookstoves in Guatemala (RESPIRE).

During the first randomized intervention trial (RESPIRE: Randomized Exposure Study of Pollution Indoors and Respiratory Effects) in air pollution epidemiology, we pioneered application of passive carbon monoxide (CO) diffusion tubes to measure long-term personal exposures to woodsmoke. Here we report on the protocols and validations of the method, trends in personal exposure for mothers and their young children, and the efficacy of the introduced improved chimney stove in reducing personal exposures and kitchen concentrations. Passive diffusion tubes originally developed for industrial hygiene applications were deployed on a quarterly basis to measure 48-hour integrated personal carbon monoxide exposures among 515 children 0-18 months of age and 532 mothers aged 15-55 years and area samples in a subsample of 77 kitchens, in households randomized into control and intervention groups. Instrument comparisons among types of passive diffusion tubes and against a continuous electrochemical CO monitor indicated that tubes responded nonlinearly to CO, and regression calibration was used to reduce this bias. Before stove introduction, the baseline arithmetic (geometric) mean 48-h child (n=270), mother (n=529) and kitchen (n=65) levels were, respectively, 3.4 (2.8), 3.4 (2.8) and 10.2 (8.4) p.p.m. The between-group analysis of the 3355 post-baseline measurements found CO levels to be significantly lower among the intervention group during the trial period: kitchen levels: -90%; mothers: -61%; and children: -52% in geometric means. No significant deterioration in stove effect was observed over the 18 months of surveillance. The reliability of these findings is strengthened by the large sample size made feasible by these unobtrusive and inexpensive tubes, measurement error reduction through instrument calibration, and a randomized, longitudinal study design. These results from the first randomized trial of improved household energy technology in a developing country and demonstrate that a simple chimney stove can substantially reduce chronic exposures to harmful indoor air pollutants among women and infants.

New approaches to performance testing of improved cookstoves.

Monitoring and evaluation of improved cookstove performance is a critical factor in program success; however, consistent evidence indicates water boiling tests and controlled cooking tests are not representative of stove performance during daily cooking activities, and there is no ability to link these tests to kitchen performance tests during normal daily cooking activities. Since emissions from cookstoves contribute heavily to regional estimates of carbonaceous aerosols and other short-lived greenhouse species and given the current importance of stove performance tests as a basis for global climate prediction models and IPCC inventories, improvements in performance testing are critical to derive more representative estimates. Here real-time combustion efficiencies and emissions rates from daily burn cycles of open fires and improved stoves in Mexico are used to propose a new approach to stove performance testing, using simple and economical measurement methods, based on replication of the distribution of emission rates and combustion efficiencies seen during daily cooking activities in homes. This approach provides more relevant information for global climate models and inventories, while also providing a means to recreate representative emissions profiles in a laboratory setting for technical analyses. On the basis of emission rates and combustion efficiencies during normal daily cooking, we suggest performance criteria that can be used as benchmarks for laboratory testing of improved stoves in the absence of site-specific information, although requiring confirmation by field testing during daily cooking activities.

Potential for atmospheric-driven lead paint degradation in the South Coast Air Basin of California.

Exposure to lead in paint or lead residues in house dust and soil is one of the leading environmental risks to the health of children in the United States. Components of photochemical smog can increase the degradation of binders in lead paint, leading to increased release of lead pigment granules to hands in surface contact or for deposition in house dust and soil. This study uses photochemical air quality modeling to map areas susceptible to increased lead paint degradation as a result of photochemical atmospheric pollutants to prioritize areas of concern. Typical air quality episodes in the South Coast Air Basin of California (SoCAB) are modeled for the 1970s, 1980s, and 1990s. Results indicate that large areas of the SoCAB were susceptible to atmospheric-driven accelerated lead paint degradation. Inner city urban areas from central Los Angeles to Azusa and most of Orange County had the highest susceptibility to accelerated lead paint degradation, followed by inland locations near the San Bernardino Mountains. This study identifies photochemical oxidant gases as contributors to greater lead release from indoor painted surfaces in urban areas.

An ultrasound personal locator for time-activity assessment.

The UC Berkeley Time-Activity Monitoring System (UCB-TAMS) was developed to measure time-activity in exposure studies. The system consists of small, light, inexpensive battery-operated 40-kHz ultrasound transmitters (tags) worn by participants and an ultrasound receiver (locator) attached to a datalogger fixed in an indoor location. Presence or absence of participants is monitored by distinguishing the unique ultrasound ID of each tag. Efficacy tests in rural households of highland Guatemala showed the system to be comparable to the gold-standard time-activity measure of direct observation by researchers, with an accuracy of predicting time-weighted averages of 90-95%, minute-by-minute accuracy of 80-85%, and sensitivity/specificity values of 86-89%/71-74% for one-minute readings on children 3-8 years-old. Additional controlled tests in modern buildings and in rural Guatemalan homes confirmed the performance of the system with the presence of other ultrasound sources, with multiple tags, covered by clothing, and in other non-ideal circumstances.

Ouantification of carbon savings from improved biomass cookstove projects.

In spite of growing interest, a principal obstacle to wider inclusion of improved cookstove projects in carbon trading schemes has been the lack of accountability in estimating CO2-equivalent (CO2-e) savings. To demonstrate that robust estimates of CO2-e savings can be obtained at reasonable cost, an integrated approach of community-based subsampling of traditional and improved stoves in homes to estimate fuel consumption and greenhouse gas emissions, combined with spatially explicit community-based estimates of the fraction of nonrenewable biomass harvesting (fNRB), was used to estimate CO2-e savings for 603 homes with improved Patsari stoves in Purépecha communities of Michoacán, Mexico. Mean annual household CO2-e savings for CO2, CH4, CO, and nonmethane hydrocarbons were 3.9 tCO2-e home(-1) yr(-1) (95% Cl +/- 22%), and for Kyoto gases (CO2 and CH4) were 3.1 tCO2-e home(-1) yr(-1) (95% Cl +/- 26%), respectively, using a weighted mean fNRB harvesting of 39%. CO2-e savings ranged from 1.6 (95% Cl +/- 49%) to 7.5 (95% Cl +/- 17%) tCO2-e home(-1) yr(-1) for renewable and nonrenewable harvesting in individual communities, respectively. Since emission factors, fuel consumption, and fNRB each contribute significantly to the overall uncertainty in estimates of CO2-e savings, community-based assessment of all of these parameters is critical for robust estimates. Reporting overall uncertainty in the CO2-e savings estimates provides a mechanism for valuation of carbon offsets, which would promote better accounting that CO2-e savings had actually been achieved. Cost of CO2-e savings as a result of adoption of Patsari stoves was U.S. $8 per tCO2-e based on initial stove costs, monitoring costs, and conservative stove adoption rates, which is approximately 4 times less expensive than use of carbon capture and storage from coal plants, and approximately 18 times less than solar power. The low relative cost of CO2-e abatement of improved stoves combined with substantial health cobenefits through reduction in indoor air pollution provides a strong rationale for targeting these less expensive carbon mitigation options, while providing substantial economic assistance for stove dissemination efforts.

Reduction in personal exposures to particulate matter and carbon monoxide as a result of the installation of a Patsari improved cook stove in Michoacan Mexico.

UNLABELLED: The impact of an improved wood burning stove (Patsari) in reducing personal exposures and indoor concentrations of particulate matter (PM(2.5)) and carbon monoxide (CO) was evaluated in 60 homes in a rural community of Michoacan, Mexico. Average PM(2.5) 24-h personal exposure was 0.29 mg/m(3) and mean 48-h kitchen concentration was 1.269 mg/m(3) for participating women using the traditional open fire (fogon). If these concentrations are typical of rural conditions in Mexico, a large fraction of the population is chronically exposed to levels of pollution far higher than ambient concentrations found by the Mexican government to be harmful to human health. Installation of an improved Patsari stove in these homes resulted in 74% reduction in median 48-h PM(2.5) concentrations in kitchens and 35% reduction in median 24-h PM(2.5) personal exposures. Corresponding reductions in CO were 77% and 78% for median 48-h kitchen concentrations and median 24-h personal exposures, respectively. The relationship between reductions in median kitchen concentrations and reductions in median personal exposures not only changed for different pollutants, but also differed between traditional and improved stove type, and by stove adoption category. If these reductions are typical, significant bias in the relationship between reductions in particle concentrations and reductions in health impacts may result, if reductions in kitchen concentrations are used as a proxy for personal exposure reductions when evaluating stove interventions. In addition, personal exposure reductions for CO may not reflect similar reductions for PM(2.5). This implies that PM(2.5) personal exposure measurements should be collected or indoor measurements should be combined with better time-activity estimates, which would more accurately reflect the contributions of indoor concentrations to personal exposures. PRACTICAL IMPLICATIONS: Installation of improved cookstoves may result in significant reductions in indoor concentrations of carbon monoxide and fine particulate matter (PM(2.5)), with concurrent but lower reductions in personal exposures. Significant errors may result if reductions in kitchen concentrations are used as a proxy for personal exposure reductions when evaluating stove interventions in epidemiological investigations. Similarly, time microenvironment activity models in these rural homes do not provide robust estimates of individual exposures due to the large spatial heterogeneity in pollutant concentrations and the lack of resolution of time activity diaries to capture movement through these microenvironments.

An inexpensive light-scattering particle monitor: field validation.

We have developed a small, light, passive, inexpensive, datalogging particle monitor called the "UCB" (University of California Berkeley particle monitor). Following previously published laboratory assessments, we present here results of tests of its performance in field settings at high particle concentrations. We demonstrate the mass sensitivity of the UCB in relation to gravimetric filter-based PM(2.5) mass estimates as well as commercial light-scattering instruments co-located in field chamber tests and in kitchens of wood-burning households. The coefficient of variation of the unadjusted UCB mass response in relation to gravimetric estimates was 15%. Although requiring adjustment for differences in sensitivity, inter-monitor performance was consistently high (r(2) > 0.99). Moreover, the UCB can consistently estimate PM(2.5) mass concentrations in wood-burning kitchens (Pearson r(2) = 0.89; N = 99), with good agreement between duplicate measures (Pearson r(2) = 0.94; N = 88). In addition, with appropriate cleaning of the sensing chamber, UCB mass sensitivity does not decrease with time when used intensively in open woodfire kitchens, demonstrating the significant potential of this monitor.