Impact of trash burning on air quality in Mexico City

Air pollution experienced by expanding urban areas is responsible for serious health effects and death for millions of people every year. Trash burning is a common disposal method in poor areas, yet it is uncontrolled in many countries, and its contribution to air pollution is unclear due to uncertainties in its emissions. Here we develop a new trash burning emission inventory for Mexico City based on inverse socioeconomic levels and recently measured emission factors, and apply a chemistry-transport model to analyze the effects on pollutant concentrations. Trash burning is estimated to emit 25 tons of primary organic aerosols (POA) per day, which is comparable to fossil fuel POA emissions in Mexico City, and causes an increase in average organic aerosol concentrations of ~0.3 μg m⁻³ downtown and up to 2 μg m⁻³ in highly populated suburbs near the sources of emission. An evaluation using submicrometer antimony suggests that our emission estimates are reasonable. Mitigation of trash burning could reduce the levels of organic aerosols by 2-40% and those of PM2.5 by 1-15% over the metropolitan area. The trash burning contributions to carbon monoxide, nitrogen oxides, and volatile organic compounds were found to be very small (<3%), and consequently the contributions to secondary nitrate, sulfate, and secondary organic aerosols are also very small.