Contenido de Metales en el Tracto Respiratorio Bajo de Personas que Residieron en la Ciudad de México

Abstract

Background. It is known that when metals are inhaled, they cause damage to the respiratory and cardiovascular tract and the central nervous system, damage that can evolve from a swelling process to chronic diseases, cancer or even death. On the other hand, one of the components of air particles are metals, especially of the transition type, which apparently have an important role in the observed ominous effects such as the increase in mortality and morbidity observed during the days in which the air particles surpass the permissible exposure limits, mainly as a result of respiratory, cardiovascular and central nervous system causes. Residents of Mexico City are constantly exposed to polluted air, especially containing high levels of particles (PM10, PM2,5) which are found in the breathable fraction, these contain different metals and on variable concentrations of them, according to the geographic location and the season of the year. Objective. To determine the metal content as well as the respiratory pathologies, in the low respiratory tract of individuals who lived in Mexico City for more than 2 years, considering their social and biological background and to classify the population according to vulnerability levels. Methods. An exploratory investigation was developed in 36 accidentally deceased individuals, from which biological, social and environmental exposition backgrounds were analyzed and 250 respiratory tissue samples were obtained (lobes, lymph nodes, bronchi and hilium). During the investigation, the presence of 24 elements were studied by flame atomic absorption spectroscopy, graphite furnace and inductive coupled plasma-optical emission spectroscopy (ICP-OES). Samples were previously dried, ground and digested. The reading of the samples in the histopathologic study, took place with a Axioplan binocular Zeiss microscope of five objective lenses. The statistical analysis considered the internal data consistency, descriptive analysis, univariate analysis, analysis of variance and multivariate analysis. Results. 18 metals were identified in the respiratory tissue samples, from which the presence of only 14 elements was consistent with the statistical analysis used, i.e., they were found in all tissue samples. Such elements were: Li, Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Se, Sr and Pb. Moreover, 15 pathologic findings were identified – incipient bronchitis, bronchitis, pulmonary edema, alveolar edema, pulmonary hemorrhage, alveolar hemorrhage, intra alveolar hemorrhage, pneumonia, multiple pneumonitis, emphysema, fibrosis, pulmonary congestion, anthracosis, nodule hyperplasia, and adenitis , from the latter pulmonary edema, alveolar edema, emphysema, anthracosis, hemorrhage, pulmonary congestion, pneumonitis, nodule hyperplasia and history of cardiovascular disease and respiratory illnesses positively correlate with metal contents in the low respiratory tract. The aggregate multivariate analysis showed that the sample was composed by four groups of clearly differentiated individuals according to the amount and pattern of the metals found in the respiratory tract, according to age, time of residence in Mexico City and found pathologies. Conclusion: The individuals studied showed different social and biologic backgrounds however, they were all exposed to polluted air in Mexico City for more than two years. The results obtained show the presence of metals in all respiratory tissue samples, however, the amount of each element varies among individuals and among the respiratory segments analyzed. The higher concentration was found in the peribronchial nodules, which suggests first, a high inhalation dose of the identified metals and second, an overcharge of the defense mechanisms or damage of the respiratory system or both. Aspects such as age, histological damage, environmental exposition and periods of time in indoor and outdoor environments, locomotion hours and time of residence, determined the amount and distribution of the metals in the respiratory tract and made it possible to classify the population of this study, in four clearly differentiated groups.