Burning cowdung cakes can be 10 times more harmful than burning wood in poorly ventilated kitchens, something that can damage the lungs, a study comparing the two widely used kitchen fuels has found. Women who spend many hours cooking food in poorly ventilated homes can develop chronic obstructive lung disease (COPD), asthma, tuberculosis and lung cancer, says Dr Sundeep Salvi, director of Pune’s Chest Research Foundation. Exposure to biomass fuel smoke, he says, is a bigger risk factor for COPD than smoking.