Polycyclic aromatic hydrocarbons in PM2.5 in the metropolitan zone of Mexico Valley: Impact of air quality management programmes

Abstract

Atmospheric fine particulate matter ≤2.5 μm (PM2.5) is the main driver of air pollution's burden of disease worldwide. Polycyclic aromatic hydrocarbons (PAHs) are part of PM2.5 and most of them are toxic to human health. In this study, the PAHs in PM2.5 around the Metropolitan Zone of Mexico Valley (MZMV), determined in 2016–2017, were compared against PAHs determined a decade ago in 2006. Decreases of 34 ± 9% in carcinogenic PAHs and 60 ± 7% in benzo[ghi]perylene were observed. This behaviour is consistent with the decreasing trend of primary Atmospheric Criteria Pollutants in the same period. PAHs reductions were observed despite increases in population, vehicle fleet and demand for fuel consumption. PAHs diagnostic ratios (DRs) identified stationary/area sources, and vehicular sources based on a pair of DRs and a range of DR values, rather than on individual values. Greater diversity of stationary and area sources in 2016–2017 was identified. Changes in DRs related to vehicular sources were observed over a decade, associated with improvements in gasoline vehicle technology and the use of better-quality fuels in recent years. Air quality management programs related to reducing pollutant concentrations mainly emitted by gasoline vehicles are discussed. However, future efforts on controlling the emissions from diesel combustion sources is suggested. Finally, a brief comparison of PAHs with other cities around the world is described.