I never claimed that CO2 was the only pollutant, my meaning was very different to that. Nor does that research cover wastes exhaled by people & animals.
In itself exhaled CO2 becomes an issue when we have high concentrations of people in confined, poorly ventilated areas - greenhouse gases such as human methane ain't much fun either btw.
To restate & as a summary; Mexico City is already heavily polluted. Adding to CO2 emissions would exacerbate the current pollution load, including CO2 exhaled by 25m people. At high concentrations CO2 becomes toxic but even at lower levels it adds to the total pollution load.
CO2 & methane are greenhouse gases & even Monckton admits that global air temperatures are rising - not that he appears to understand how that manifests itself in the environment [eg. tundra thawing & consequent release of otherwise locked up greenhouse gases].
