[en] Studies on air pollution have intensified in recent years, due to the diversity of emissions and the effect caused to the health of populations. Consequently, several techniques have been investigated for air pollution evaluation and among them one that has gained considerable attention is that of biomonitoring. In this study chemical elemental levels in the atmosphere of Sao Paulo city were evaluated, by means of passive biomonitoring, using epiphytic Canoparmelia texana species, in order to compare between the results obtained in samples from different sites of Sao Paulo city and in a reference site of Ubatuba city, SP. Neutron activation analysis (NAA) procedure applied in the analyses consisted of irradiating aliquots of samples along with synthetic standards of elements in the nuclear reactor IEA-R1 for 16 hours under a thermal neutron flux of about 5.0 x 10¹² n cm^-2 s^-1, followed by gamma ray spectrometry for the determination of As, Br, Ca, Co, Cr, Cs, Fe, K, La, Rb, Sc, Se and Zn. Results obtained in the analyses of lichens samples in replicates presented good reproducibility indicating homogeneity of the prepared samples. The precision and accuracy of the results were evaluated by the analyses of certified reference materials IAEA-336 Lichen and INCT-TL-1 Tea Leaves. Results obtained in the reference materials presented, in general, good precision, with relative standard deviations between 0.4 and 14.8% and good accuracy with relative errors between 0.2 and 8.7%. In Sao Paulo city, the lichens were collected in the following sites: Parque Dom Pedro II, Congonhas, Cidade Universitaria, Lapa, Mooca, Morumbi, Nossa Senhora do O, Parque Ibirapuera, Pinheiros, Santana, Santo Amaro and Taboao da Serra. Element concentrations found in lichens indicated a great variability depending on the sites where the samples were collected. The results obtained in the lichens submitted to the cluster analysis indicated three groups of sampling sites according to the chemical similarity obtained in lichens. Lichen collected in the reference site of Ubatuba indicated that most of element concentrations are lower or at the same order of magnitude when compared with those obtained in lichens collected in Sao Paulo city. The highest element concentrations in the sample from Ubatuba were obtained for Br, K and Zn. Results obtained in this study indicated that the origins of elements present in the atmosphere of Sao Paulo city are due to mainly vehicular emissions followed industrial emissions and from soil. Elements named vehicular emission markers (Br, Co, Sb and Zn), industrial markers (Cr, Co and Fe) and from soil (Sb, Se, Rb e La) were determined in the lichens. (author)