A mathematical modeling approach to risk assessment for normal and anemic women chronically exposed to carbon monoxide from biomass-fueled cookstoves

In developing countries, the chronic exposure to carbon monoxide (CO) from biomass-fueled cookstoves may pose a significant health risk for women who use these stoves, especially for those with underlying clinical conditions that impair tissue oxygenation, e.g., anemia and coronary artery disease. CO concentrations measured in the vicinity of these cookstoves often exceed World Health Organization (WHO) indoor air guidelines for an 8-h average (9 ppm) and a 1-h maximum (26 ppm). Carboxyhemoglobin levels, reported infrequently because they are difficult to obtain, often exceed the WHO threshold of 2.5%. Despite this evidence, specific adverse effects have not yet been linked with chronic CO exposures in these women. Furthermore, anemia, which is prevalent in populations that use biomass fuels, could exacerbate the adverse effects of chronic CO exposure. Because of the difficulties inherent in conducting prospective studies to address this issue, we used a mathematical model to calculate the effects of reported CO levels and exercise on carboxyhemoglobin for women living in 1) Guatemalan villages at altitudes of 4,429-4,593 ft, and 2) coastal villages in Pakistan. In addition, we used the model to calculate the effects of CO exposures in women with moderate to severe anemia on specific physiological parameters (carboxyhemoglobin, carboxymyoglobin, cardiac output, and tissue Po(2)) at exercise levels representing the activities in which these women would be engaged. Our results demonstrate the efficacy of using a mathematical model to predict the physiologic responses to CO and also demonstrate that chronic anemia is a critically important determinant of CO toxicity in these women.