Although global energy consumption from biomass fuels or biofuels is only a small part of the total (12%), the use is much more prevalent in developing countries than in developed countries (33% vs 3%).¹ It is estimated that almost 3 billion people or 50% of households worldwide use biomass and coal as their main source of energy for cooking, heating and other household needs.^2,3 Biofuels have higher emission factors for particulate matter and other pollutants, especially during incomplete combustion at lower temperatures,⁴ which generates indoor airborne particles at levels much higher than those for cleaner fuels⁵ or outdoors,³ and well above levels in most polluted cities.⁶ Such particles also have small aerodynamic diameters (ranging from 0.05 to 1 μm for wood smoke, for example)¹ and can penetrate deep into the alveolar region to induce adverse pulmonary effects. Some of the earliest work concerned with respiratory health and the burning of biofuels in developing countries started with investigations into wood smoke exposure in the 1960s in Papua New Guinea.^1,7,8 More studies on domestic smoke pollution and chronic bronchitis were conducted in rural Nepal.^9,10 In the past two decades a number of epidemiological studies have been conducted specifically to evaluate the burning of solid biofuels as a risk factor for chronic obstructive pulmonary disease (COPD). These studies, performed in various regions of the developing world such as Saudi Arabia,¹¹ Columbia,¹² Mexico,¹³ Turkey¹⁴ and Nepal,⁵ have shown a link between biofuel cooking and COPD in women. In addition, a link has also been found in developed countries.¹⁵ Little has been reported, however, …