Returning to his presentation, Jon reviewed NO2, which is an important pollutant in Mexico City. NO2 is a respiratory irritant and also an ozone precursor. 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.