ASSESSING PARTICULATE MATTER AND BLACK CARBON EMISSIONS FROM HOMES USING TRADITIONAL AND ALTERNATIVE COOKSTOVES IN RURAL NEPAL

Billions of people throughout the developing world use traditional cookstoves fueled with biomass (such as wood, dried animal manure, and crop residue). Inefficient combustion of biomass results in the formation of large amounts of particulate matter (PM) air pollution. Light reflecting black carbon is a significant component of this PM. Black carbon is considered a short-term climate agent with an average atmospheric residence time on the order of days to weeks, compared to some greenhouse gases that can have an atmospheric residence time of years to centuries. In addition to having an effect on regional hydrological cycles, black carbon deposition on glaciers, sea, or land ice causes a decrease in surface albedo, thus resulting in an acceleration of the melting process. The Himalayas, an area containing the largest snow and ice mass outside the North and South Poles, are vulnerable to black carbon deposition from highly prevalent biomass cooking in surrounding countries. Deposition of black carbon from air pollution has the potential to impact the availability of glaciers in this region, which act as a water source for close to a billion people throughout South and East Asia. As a result, due to the larger population, biomass for cooking in South Central Asia has the potential to impact climate change on a local and global scale. It is believed that a large majority of black carbon production in South Asia is a result of cooking with biomass fuels. However, biomass cooking is not the only source of black carbon. Mobile (diesel vehicles) and stationary (brick kilns) sources can also be significant emitters. This study estimates black carbon emissions associated with traditional and alternative cookstoves at the household level. This study can be further separated into three main components. The first component is a methods paper focusing on improved quality control for a commonly used particulate matter sampling method. Great uncertainty exists around indoor biomass burning exposure-disease relationships due to lack of detailed exposure data in large health outcome studies. Passive nephelometers can be used to estimate high particulate matter (PM) concentrations during cooking in low resource environments. Nephelometric concentration readings can be biased due to particle growth in high humid environments and differences in compositional and size dependent aerosol light scattering characteristics. Chapter 2 explores relative humidity (RH) and gravimetric equivalency adjustment approaches for the pDR-1000, which is used to assess indoor PM concentrations for a cookstove intervention trial in Nepal. Furthermore, new integrated RH and gravimetric conversion methods are presented because they have one response variable (gravimetric PM2.5 concentration), do not contain an RH threshold, and are more straightforward than previously proposed approaches. The second component focuses on characterizing the amount of particulate matter and black carbon that exit the house during the use of traditional, open-design cookstoves in village homes. Cookstove emissions create indoor exposures and contribute to ambient air pollution through passive exchanges between indoor and outdoor air (indirect venting) and direct venting (i.e., chimney) to the outdoors. A fraction of PM produced during cooking will settle and deposit on indoor surfaces as well as in cracks within the walls of the house, while the rest will escape to the outdoor environment (known as exfiltration). Currently, there is a poor understanding of how much cooking-related PM exfiltrates to the outdoor environment. Chapter 3 presents air exchange rates and PM exfiltration estimates from homes in rural Nepal that utilize traditional, open-design cookstoves. Estimates of variability are provided for exfiltration as a function of housing and fuel characteristics in a real-world setting. Furthermore, this chapter assesses the black carbon to PM2.5 ratio produced by biomass cooking in order to estimate black carbon exfiltration from homes. In combination with an assessment of indoor PM concentrations, PM and black carbon exfiltration fractions can be used to estimate house emissions to ambient air in order to better assess regional air quality and climate change impacts. The third component (Chapter 4) extends upon this work by presenting exfiltration estimates of PM that exit to the outdoors via the combined route of indirect (natural) and direct (chimney) ventilation for alternative cookstoves being studied in a large, cookstove intervention trial in rural Nepal. Characterizing these exfiltration pathways allows for homes to be treated as a source, hence aggregating variability related to stove emissions. Future work will utilize estimated black carbon emissions in combination with estimates of cookstove use and cooking pattern estimates to serve as inputs for spatial regression modeling that will allow for the prediction of ground level black carbon concentrations across much of Northern India and Southern Nepal (the Indo-Gangetic Plain). Since a large fraction of the world’s biomass cookstove users are in South Central Asia, this project provides significant insight of cookstove emission to atmospheric contribution

Humidity and gravimetric equivalency adjustments for nephelometer-based particulate matter measurements of emissions from solid biomass fuel in cookstoves

Great uncertainty exists around indoor biomass burning exposure-disease relationships due to lack of detailed exposure data in large health outcome studies. Passive nephelometers can be used to estimate high particulate matter (PM) concentrations during cooking in low resource environments. Since passive nephelometers do not have a collection filter they are not subject to sampler overload. Nephelometric concentration readings can be biased due to particle growth in high humid environments and differences in compositional and size dependent aerosol characteristics. This paper explores relative humidity (RH) and gravimetric equivalency adjustment approaches to be used for the pDR-1000 used to assess indoor PM concentrations for a cookstove intervention trial in Nepal. Three approaches to humidity adjustment performed equivalently (similar root mean squared error). For gravimetric conversion, the new linear regression equation with log-transformed variables performed better than the traditional linear equation. In addition, gravimetric conversion equations utilizing a spline or quadratic term were examined. We propose a humidity adjustment equation encompassing the entire RH range instead of adjusting for RH above an arbitrary 60% threshold. Furthermore, we propose new integrated RH and gravimetric conversion methods because they have one response variable (gravimetric PM2.5 concentration), do not contain an RH threshold, and is straightforward

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

Alternative cookstoves are designed to improve biomass fuel combustion efficiency to reduce the amount of fuel used and lower emission of air pollutants. The Nepal Cookstove Trial (NCT) studies effects of alternative cookstoves on family health. Our study measured indoor particulate matter concentration (PM2.5), boiling time, and fuel use of cookstoves during a water-boiling test in a house-like setting in rural Nepal. Study I was designed to select a stove to be used in the NCT; Study II evaluated stoves used in the NCT. In Study I, mean indoor PM2.5 using wood fuel was 4584 μg/m3 , 1657 μg/m3 , and 2414 μg/m3 for the traditional, alternative mud brick stove (AMBS-I) and Envirofit G-series, respectively. The AMBS-I reduced PM2.5 concentration but increased boiling time compared to the traditional stove (p-values \u3c 0.001). Unlike AMBS-I, Envirofit G-series did not significantly increase overall fuel consumption. In Phase II, the manufacturer altered Envirofit stove (MAES) and Nepal Nutrition Intervention Project Sarlahi (NNIPS) altered Envirofit stove (NAES), produced lower mean PM2.5, 1573 μg/m3 and 1341 μg/m3 , respectively, relative to AMBS-II 3488 μg/m3 for wood tests. The liquid propane gas stove had the lowest mean PM2.5 concentrations, with measurements indistinguishable from background levels. Results from Study I and II showed significant reduction in PM2.5 for all alternative stoves in a controlled setting. In study I, the AMBS-I stove required more fuel than the traditional stove. In contrast, in study II, the MAES and NAES stoves required statistically less fuel than the AMBS-II. Reductions and increases in fuel use should be interpreted with caution because the composition of fuels was not standardized—an issue which may have implications for generalizability of other findings as well. Boiling times for alternative stoves in Study I were significantly longer than the traditional stove—a trade-off that may have implications for acceptability of the stoves among end users. These extended cooking times may increase cumulative exposure during cooking events where emission rates are lower; these differences must be carefully considered in the evaluation of alternative stove designs

Exposure to extreme heat and precipitation events associated with increased risk of hospitalization for asthma in Maryland, U.S.A.

Several studies have investigated the association between asthma exacerbations and exposures to ambient temperature and precipitation. However, limited data exists regarding how extreme events, projected to grow in frequency, intensity, and duration in the future in response to our changing climate, will impact the risk of hospitalization for asthma. The objective of our study was to quantify the association between frequency of extreme heat and precipitation events and increased risk of hospitalization for asthma in Maryland between 2000 and 2012. We used a time-stratified case-crossover design to examine the association between exposure to extreme heat and precipitation events and risk of hospitalization for asthma (ICD-9 code 493, n = 115,923). Occurrence of extreme heat events in Maryland increased the risk of same day hospitalization for asthma (lag 0) by 3 % (Odds Ratio (OR): 1.03, 95 % Confidence Interval (CI): 1.00, 1.07), with a considerably higher risk observed for extreme heat events that occur during summer months (OR: 1.23, 95 % CI: 1.15, 1.33). Likewise, summertime extreme precipitation events increased the risk of hospitalization for asthma by 11 % in Maryland (OR: 1.11, 95 % CI: 1.06, 1.17). Across age groups, increase in risk for asthma hospitalization from exposure to extreme heat event during the summer months was most pronounced among youth and adults, while those related to extreme precipitation event was highest among ≤4 year olds. Exposure to extreme heat and extreme precipitation events, particularly during summertime, is associated with increased risk of hospitalization for asthma in Maryland. Our results suggest that projected increases in frequency of extreme heat and precipitation event will have significant impact on public health.https://doi.org/10.1186/s12940-016-0142-

Additional file 1: of Exposure to extreme heat and precipitation events associated with increased risk of hospitalization for asthma in Maryland, U.S.A.

Supplemental Materials. Table A.1. Sensitivity Analysis Showing the Impact of Lag Structures for the Odds Ratios and 95 % Confidence Intervals. Table A.2. Sensitivity analysis across extreme threshold combinations for overall model for the entire state of Maryland. Table A.3. Analysis Showing the Odds Ratios and 95 % Confidence Intervals for Exposure to Extreme Events for the Spring, Winter, and Autumn seasons. Figure A.1. Location of weather stations in Maryland. Figure A.2. Monthly averaged number of extreme heat and extreme precipitation events by county, for overall years and during summer months only (2000–2012). (DOCX 62764 kb