<p>Air pollution affects human health and ecosystems all over the world. However, little attention is paid to its monitoring in tropics, mainly due to the high costs of automated monitoring systems. Biomonitoring may be an alternative, particularly for species of <i>Tillandsia</i> genus, although most species are not yet calibrated for this purpose. Therefore, 1) to determine the biomonitoring potential of <i>T. juncea</i> and <i>T. schiedeana</i> and, 2) to compare the sources and magnitudes of atmospheric pollutants at five urban parks and one rural site in a tropical metropolitan area in Mexico, we measured the elemental and isotopic composition of carbon and nitrogen of four <i>Tillandsia</i> species. Carbon content was consistent across sites and species with no differences. The nitrogen content showed a clear trend of increasing from rural to urban areas, with significantly higher values observed in urban environments. The more negative δ¹³C values were recorded in urban parks, while less negative values were recorded in rural areas, reflecting differences in environmental CO₂ sources. Similarly, δ¹⁵N values were more negative in rural sites and shifted toward positive values in urban areas, showing the influence of anthropogenic nitrogen sources. These highlight the different environmental conditions across the rural and urban landscape. The four species can be used as biomonitors of C and N emissions, since their specific variations reflect the source and concentration of these atmospheric pollutants. Furthermore, the tillandsias showed that pollution in the metropolitan area is different depending on the activity at each site.</p>