Huge clouds of foam waft through the municipality of Mosquera on the outskirts of the Colombian capital Bogota, leaving a foul stench and causing health problems, according to locals. For several years, residents of the Los Puentes sector in the municipality have become accustomed to the appearance of the cotton wool-like foam in the Balsillas River, where sewage from Bogota, some seven kilometres away, flows into the river. Unusually heavy rains this year have worsened the problem, as well as poor waste management, according to local authorities. IMAGES AND SOUNDBITES