TWP's improved cook stoves have undergone a number of different tests to determine their ability to reduce carbon monoxide and particulate emissions. Reducing emissions is critical both for improving respiratory health and for cutting down on the greenhouse gases that contribute to global climate change.

University of Illinois, Urbana-Champaign study*

Tami Bond, Ph.D. and doctoral candidate Chris Roden of the University of Illinois, Urbana-Champaign conducted field testing of Eco-stoves in Honduras. Roden and Bond developed a portable battery-operated sampling cart, which included sensors for measuring carbon dioxide and carbon monoxide, particle soot absorption, and particle color and concentration. They found that cook stoves there, which are similar to those used in other developing nations, produce two times more smoke particles than expected, based on previous laboratory studies. These sooty particles, which are darker than those produced by grassland or forest fires, have a greater climate warming effect because they absorb solar energy and heat the atmosphere, according to Roden.

Bond estimated that burning firewood―the principal fuel for cook
stoves in the developing world―produces 800,000 metric tons of soot worldwide each year. In comparison, diesel cars and trucks generate about 890,000 metric tons of soot annually. These two sources each account for about 10 percent of the soot emitted into the world’s atmosphere each year.

Colorado State University study**

The CSU study found that TWP's improved cook stoves substantially reduced indoor air pollution. The study examined a cross-section of 60 non-smoking Honduran women, 30 with traditional stoves and 30 with improved stoves. Carbon monoxide (CO) and particulate matter (PM2.5) were assessed via 8-hour indoor and outdoor area monitoring, as well as 8-hour personal PM2.5 monitoring. Kitchen parameters, carbon dioxide, and relative humidity were determined to estimate ventilation rates that might affect CO and PM2.5. Forced expiratory volume in one second (FEV1), respiratory symptoms, and demographic characteristics were assessed. Stoves were scored on a 4-level subjective scale representing potential for indoor emissions, ranging from poorly functioning traditional stoves to well-functioning improved stoves. Personal PM2.5 means corresponding to this scale were 236 µg/m3, 119 µg/m3, 82 µg/m3, and 66 µg/m3, respectively. Corresponding kitchen PM2.5 means were 1,258 µg/m3, 532 µg/m3, 294 µg/m3, and 218 µg/m3, respectively. Corresponding kitchen CO means were 9.18 ppm, 3.29 ppm, 1.30 ppm, and 0.16 ppm, respectively. Women with improved stoves were older than those with traditional stoves (p=0.03); height, body mass index, and education levels were similar. Usual presence of cough, wheeze, and headache was reported more frequently among traditional stove users as compared to improved stove users (p<0.01). Data collected will allow for examination of the association between air quality measurements and FEV1, while adjusting for important covariates.

University of California-Berkeley study***

In 2002, Center for Entrepreneurship in International Health and Development (CEIHD) researchers conducted a study in Ciudadela de San Martin, Nicaragua, to evaluate the efficacy and effectiveness of two models of the Eco-stove in reducing indoor air pollution (IAP).
IAP exposure is widely accepted as a valid and reliable indicator of health risk. CEIHD evaluated the influence of stove type on kitchen air pollution levels and women’s exposures to particle matter less than 2.5 micrometers in aerodynamic diameter (PM2.5) through a randomized stove intervention trial. After the initial round of measurements among the 60 study participants, half the participating
households received an entirely closed Eco-stove while the others received a newer, slightly less expensive model with a semi-open design.

Both Eco-stove models achieved large reductions in indoor air pollution and exposure among Nicaraguan women cooking in enclosed kitchens. Adjusting for the effects of study group, duration of cooking, burning trash and average daily temperature, introduction of the closed Eco-stove was associated with an 86% reduction in PM2.5 exposure, while the introduction of the semi-open model was associated with an 80% reduction. However, the two Eco-stove models did have significantly different effects on kitchen levels of PM2.5 (p-value = 0.028), with the closed Eco-stove reducing kitchen PM2.5 levels by 94% and the semi-open Eco-stove reducing kitchen PM2.5 levels by 87%. The magnitude of the exposure reductions for both Eco-stove models is expected to have great health benefits for Nicaraguan families.

*Emission Factors and Real-Time Optical Properties of Particles Emitted from Traditional Wood Burning Cookstoves. Christoph A. Roden, Tami C. Bond, Stuart Conway, Anibal Benjamin Osorto Pinel (Department of Civil and Environmental Engineering, University of Illinois, Urbana-Champaign, Urbana, Illinois, 2006)

**Indoor Air Pollution and Respiratory Health Among Honduran Women. M.L. Clark, J.L. Peel, S. Conway, J.B. Burch, S.J. Reynolds (Colorado State University, Fort Collins, Colorado, 2006)

***Evaluation of the Efficacy and Effectiveness of the EcoStove for Reducing Indoor Air Pollution Exposures Among Nicaraguan Women. John McCracken and Dana Charron (Center for Entrepreneurship in International Health and Development, University of California-Berkeley, Berkeley, California, 2003)