Water contamination is threatening residents in Mexico City, the Mexican capital. <br /><br />Many in the city rely heavily on surrounding water basins for fresh water. One of the main sources is a series of canals constructed during the time of the Aztecs. <br /><br />But booming expansion in the much hailed "mega city" is polluting the canals at an alarming level. <br /><br />Franc Contreras reports from Mexico City.
