Spatial Analysis of Particulate Matter (PM10) Air Pollution in Cities Surrounding a Ceramic Industrial Hub in the State of São Paulo, Brazil

Industrial activity is among the principal sources of atmospheric emissions in urban areas. The ceramic industry, for example, emits high quantities of atmospheric contaminants, including particulate matter produced during clay extraction and production. The Santa Gertrudes ceramic industrial hub (SGCIH), located in the state of São Paulo, Brazil, is the sixth largest exporter of ceramic products in the world. The aim of this research is to present preliminary results concerning the effects of SGCIH ceramic industry agglomeration on the spatial distribution of particulate matter (PM₁₀) in cities located in surrounding areas. In addition to the Santa Gertrudes (23,192 inhabitants; 48 ceramic industries in 2025) and Rio Claro (210,323 inhabitants; 18 industries), which are cities located in the SGCIH, we also analyzed PM₁₀ data from four cities located far from the SGCIH, which have smaller numbers of ceramic industries: Piracicaba (440,835 inhabitants; 4 industries), Limeira (301,292 inhabitants; 2 industries), Americana (246,665 inhabitants; 1 industry), and Paulinia (116,674 inhabitants; 1 industry). Daily PM₁₀ data from August 1, 2025, to September 30, 2025, obtained from six air quality monitoring stations located in the aforementioned cities, were used. PM₁₀ medians were calculated and subsequently spatially interpolated using the inverse distance weighting algorithm. A first-degree trend surface map and a spatial autocorrelation pollutant map generated by the Getis‒Ord Gi statistical method were produced. The results revealed that the median PM₁₀ was significantly greater in Santa Gertrudes (86 µg/m³) (p-value<0.001) than in Rio Claro (57 µg/m³), Limeira (47 µg/m³), Piracicaba (42 µg/m³), Americana (41 µg/m³) and Paulinia (32 µg/m³). Municipalities with a greater number of ceramic industries presented the highest concentration of PM₁₀ (r=0.928; p-value=0.004). No significant association was observed between city population quantity and PM₁₀ concentration (r=-0.257; p-value=0.718). These results may indicate that the effect of the number of ceramic industries on PM₁₀ may be more important than city size is. The PM₁₀ regional trend surface showed a slope toward the south-southeast, with the highest positive residual values of PM₁₀ in the cities of the SGCIH and negative residual values in Americana and Paulinia, which were 34 km and 52 km from Santa Gertrudes, respectively. The spatial autocorrelation map revealed that PM₁₀ presented a significant spatial autocorrelation index (z=1.874; p=0.039), with high PM₁₀ values clustered ​​up to a 20-km radius around the SGCIH. We concluded that particulate matter  (PM₁₀) in the atmosphere of the studied area presented a strong and positive spatial autocorrelation, which was influenced by the SGCIH location. We also reported that the PM₁₀ concentration increases significantly with increasing proximity to the SGCIH. Moreover, compared with smaller cities, such as Santa Gertrudes and Rio Claro, which are located within SGCIH, populous cities located farther from the SGCIH presented lower PM₁₀ concentrations. In the next step of this research, we will apply this spatial analysis methodology to evaluate the possible regional dispersion of MP₁₀ and MP_2.5 pollution using longer historical data series and a greater number of cities.