First diagnosis of allergenic airborne pollen and its interaction with atmospheric pollutants in the Mexico City Metropolitan Zone   (MCMZ) and their transport and dispersion in the atmosphere.

Ma Carmen Calderon E.1, Rodolfo Sosa E2, Benjamin Martínez l.3, Cesar Guerrero4, Juan Alcivar5, Fernando Téllez U6, Invonn Santiago L.7, Ma Luisa Alarcon J.8, Ma Carmen Torres B.9, Pablo Sánchez A.10 and Mónica Jaimes P.11

Air pollution is one of the main characteristics of areas where human population density is very high; It plays an important role in the health of the entire population. In addition to the atmospheric pollutants (gases and particles) emitted by human activities, the atmosphere is the transport medium for a wide variety of biogenic particles. These include bioaerosols such as viruses, bacteria, fungi, plant fragments, pollen grains, their allergenic proteins or small airborne particles containing pollen allergens.

Atmospheric pollutants have direct effects on pollen, modifying their biological and reproductive functions, causing a decrease in viability and germination; alteration of the physicochemical characteristics of the pollen surface and its allergenic potential and adjuvant effect, increasing the potential risks to health. It has been reported that pollutants such as O3, NO2, SO2 and atmospheric deposition (wet and dry) interact with allergenic pollen in the atmosphere aggravating asthma symptoms and particulate matter together with pollen allergens play a very important role in increasing the allergic inflammatory response.  Therefore, the objective of this work was to perform a first diagnosis of airborne allergenic pollen from MCMZ, its interaction with atmospheric pollutants and their transport and dispersion in the atmosphere. Sampling of air pollen grains was carried out at four city stations belonging to the Mexican Aerobiology Network (REMA) during the period 2014 to 2016. Records of atmospheric pollutants and meteorological conditions, including wind fields, were analyzed for the same study period. The first spatial-temporal interpretation (diurnal and seasonal cycle) was performed among all variables evaluated, their transportation through the atmosphere of Mexico City and the risk to the health of the population were determined.

In this study, spatial and temporal variations in the air quality (RAMA Network) and chemical composition of rain (REDA Network) in Mexico City between 2014 to 2016 were analyzed. Major ions (Na+, NH4+, K+, Mg2+, Ca2+, SO42-, NO3- and Cl-), pH, and electrical conductivity (EC) were analyzed weekly at 4 sampling stations located in the same region MCMZ.

Spatial distribution of wet atmospheric deposition shows that pH decreases throughout the study from north to south in the MCMZ.

In the stations located in a rural area, a strong correlation was found between NH4+ and SO42-, NO3-, and Cl-; this is likely due to their origin in soil (i.e., fertilizer use).

The same concentration trend was observed for SO42- and NO3 in the MCMZ stations; this indicates that the sources of acid rain precursors are upwind (i.e., to the north) of the study area.

Considering that external emission sources play a decisive role in driving acid rain within the MCMZ, it is necessary to establish strategies for the emission reductions of acid rain precursors from upwind sources outside the MCMZ.

This shows the need to continue multidisciplinary studies as well as to expand the interaction among the different available networks: REMA, REDA and RAMA


1Universidad Nacional Autonoma de Mexico (UNAM),