Nine Latin American cities, which together are home to some 68 million people, yesterday called for a regional alliance to fight smog. The cities’ senior environmental officials signed a declaration acknowledging that half the health problems in their urban areas are attributable to environmental degradation. The declaration also called on local authorities to take serious action to combat pollution, asked oil producers and refiners to make cleaner fuel, and criticized nations that export vehicles with obsolete technology to Latin America. The cities are the Argentine capital Buenos Aires, the Costa Rican capital San Jose, Callao and Lima in Peru, Rio de Janeiro and Sao Paulo in Brazil, Bogota in Colombia, Santiago in Chile, and Mexico City.