Ozone and its nighttime concentration in the southern Mexico City metropolitan area

Pollen is an important cause of allergic respiratory ailments in the Mexico City Metropolitan Area (MCMA). However, very little is known if ambient air temperature correlates with the early blooming of plants observed in other urban areas around the world. A research study was conducted during the dry season of 2012-2013 at three representative sites of the MCMA with different urban characteristics with the aim to understand the relationships between the profusion and diversity of pollen against temperature and other meteorological variables and degree of urbanization. Pollen samples were collected using a Hirst-type trap sampler in the sites: Merced (highly urbanized), Iztapalapa (medium-high urbanized) and Coyoacan (moderately urbanized). Urbanization levels were determined using a composite index based on population density, proportion of surface covered by construction and asphalt, and urban heat island intensity. A set of representative pollen sampling tapes were assayed under a light microscope at magnification of ×1,000 and converted to grains per cubic meter. The most representative pollen types found in the three sites were, regardless of urbanization levels were: Fraxinus, Cupressaceae/Taxodiaceae, Casuarina, Alnus, Myrtaceae, and Pinus. Total pollen concentration was greatest in the moderately urbanized area, although earlier blooming took place at the highly urbanized zone. Total pollen concentration in the medium-high urbanized site has the lowest because the green areas in this zone of MCMA are few. In a diurnal basis, the most abundant pollen types peaked near midday or in the afternoon evening at the three sites. A Spearman test showed a positive correlation among bihourly pollen concentrations, temperature and relative humidity in all sites, but wind speed just correlated in Iztapalapa and Coyoacan. The results obtained suggest that Urban Heat Island Intensity can disturb flowering periods and pollen concentrations, largely in the highly urbanized areas. A principal components analysis established that the concentrations of each pollen type differed across the urbanization gradients. Additionally, it was found that a large number of allergenic pollens are produced by ornamental trees, some only recently introduced by urban planners.

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Diurnal variations of airborne pollen concentration and the effect of ambient temperature in three sites of Mexico City

Ríos

Torres‐Jardón

Ramírez‐Arriaga³

et al. 2015

Int J Biometeorol

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Analysis of the change in atmospheric urban formaldehyde and photochemistry activity as a result of using methyl-t-butyl-ether (MTBE) as an additive in gasolines of the metropolitan area of Mexico city

Bravo

Camacho

Roy-Ocotla

et al. 1991

Atmospheric Environment. Part B. Urban Atmosphere

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Cell proliferation in nasal respiratory epithelium of people exposed to urbanpollution

Calderón‐Garcidueñas¹,

Rodrı́guez-Alcaraz²,

Garcı́a³

et al. 1999

Carcinogenesis

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The nasal passages are a common portal of entry and are a prime site for toxicant-induced pathology. Sustained increases in regenerative cell proliferation can be a significant driving force in chemical carcinogenesis. The atmosphere in Mexico City contains a complex mixture of air pollutants and its residents are exposed chronically and sequentially to numerous toxicants and potential carcinogens. We were concerned that exposure to Mexico City's atmosphere might induce cytotoxicity and increase nasal respiratory epithelial cell proliferation. Nasal biopsies were obtained for DNA cell cycle analysis from 195 volunteers. The control population consisted of 16 adults and 27 children that were residents in a Caribbean island with low pollution. The exposed Mexico City population consisted of 109 adults and 43 children. Sixty-one of the adult subjects were newly arrived in Mexico City and were followed for 25 days from their arrival. Control children, control adult and exposed Mexico City children all had similar percentages of cells in the replicative DNA synthesis phase (S phase) of the cell cycle (%S). A significant increase in %S in nasal epithelial cells was seen in exposed adult residents in Mexico City biopsied at three different dates compared with control adults. Newly arrived adults exhibited a control level of cell turnover at day 2 after coming to the city. However, at days 7, 14 and 25 they exhibited significant increases in %S. These data demonstrate an increased and sustained nasal cell turnover rate in the adult population observable in as little as 1 week of residence in Mexico City. This increase in cell proliferation is in agreement with other reports of induced pathological changes in the nasal passages of Mexico City dwellers. These observations suggest an increased potential risk factor of developing nasal neoplasms for residents of large cities with heavy pollution.

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Ozone and its nighttime concentration in the southern Mexico City metropolitan area

Cited by 4 publications

References 2 publications

Diurnal variations of airborne pollen concentration and the effect of ambient temperature in three sites of Mexico City

Diurnal variations of airborne pollen concentration and the effect of ambient temperature in three sites of Mexico City

Analysis of the change in atmospheric urban formaldehyde and photochemistry activity as a result of using methyl-t-butyl-ether (MTBE) as an additive in gasolines of the metropolitan area of Mexico city

Cell proliferation in nasal respiratory epithelium of people exposed to urbanpollution

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