Love Canals in the Making

In many places, you can smell the border before you see it. Some days an acrid brown cloud hangs over the city of El Paso in the U.S. and nearby Ciudad Juarez in Mexico, blotting out office buildings and the surrounding mountains. A fetid creek called the Nogales Wash carries raw sewage from shantytowns south of the border to Nogales, Ariz. In Matamoros, just across the Rio Grande from Brownsville, Texas, children and dogs play along ditches that are coated with an iridescent slick of aromatic chemicals, many of which are known or suspected carcinogens. "These are Love Canals in the...