Ozone is linked to premature mortality and respiratory hospital admissions. NO2 also forms secondary nitrates in the atmosphere, which are fine particles and cause acid precipitation. Jon replied that since most NO is converted pretty quickly to NO2, the epidemiology literature is based on NO2. Carbon monoxide comes largely from incomplete fuel combustion in motor vehicles. Carbon monoxide poisoning can lead to headaches, nausea, and death at high concentrations, and there is some evidence of acute mortality and cardiovascular health impacts at lower concentrations.
Sulfur dioxide comes from combustion of fuel with high sulfur content.
It is less an issue in Mexico City than, for example, China, where a lot of high-sulfur coal is burned. Others have non-carcinogenic toxic effects. Lead, for example, is associated with neurological function in children and hypertension in adults. There are both direct and indirect health impacts associated with global warming, caused by emissions of greenhouse gases. They conducted a literature review of all epidemiological studies, eliminating studies with methodological problems, and then did a meta-analysis to aggregate the findings by pooling the individual findings and weighting according to the sample size.