The state-owned oil monopoly Petróleos Mexicanos (Pemex) is being blamed for contributing to Mexico City’s notoriously poor air quality by failing to provide motorists with adequate gasoline. According to statistics from the government of the Federal District—the jurisdiction that forms the core of this city—levels of some key contaminants have fallen drastically, such as lead, or remained roughly constant, such as ozone, for most of the last decade. But the district’s statistics do not reveal the true ozone picture and the role Pemex’s gasoline plays in it, says Rodolfo Sosa, a chemist in the atmospheric-pollution department of the National Autonomous University of Mexico (Unam). During the late 1980s and early 1990s, Pemex was obliged to reduce lead levels in its gasoline... [Log in to read more]