Higher heavy metal contamination indoors than outdoors during COVID-19 in Mexico City.

People spend most of their time indoors, especially during the coronavirus disease. Prolonged exposure to heavy metal-contaminated dust can be harmful to human health. The objectives of this study were to identify the contamination level in outdoor and indoor dust, compare contamination in both environments, and assess the human health risk. Two-hundred thirty-nine samples of dust were taken by Mexico City citizens in 38 homes on the weekends of May 2020. Heavy metal concentrations were measured through XRF. The contamination level was set using the contamination factor with a local and global background value, mixed linear models were used to identify indoor and outdoor differences, and USEPA human health risk methodology was used. Pb, Zn, and Cu had the highest contamination levels, followed by Sr and Mn, using both the local and global background values. The Pb, Zn, and Cu contamination was greater indoors, while higher Mn, Sr, and Fe were detected outdoors. According to the outdoor/indoor ratios, the main sources of Ca, Pb, Zn, and Cu must be indoors, while the main sources of Fe, Mn, Sr, Y, and Ti are outdoors. A human health risk was not detected, as the hazard index was lower than one. However, ailments can be developed due to exposure to Pb, Mn, and Fe in children (hazard index > 0.1). A higher risk due to Pb exposition was found indoors. Indoor environments in Mexico City were more contaminated by heavy metals and represented a higher risk to human health than outdoors during the pandemic isolation.

Soil profile photograph dataset from central Mexico to delineate horizons and quantify coarse fragments.

This database consists of a digital photograph set of soil profiles from the physiographic provinces of the Trans-Mexican Neovolcanic Axis and Sierra Madre del Sur of central Mexico. Although the official and government databases of soil profiles from Mexico do not contain the percentage of coarse fragments (stoniness), they contain soil profile photographs from which the percentage of coarse fragments can be extracted. The dataset has two data source types: (a) Soil profile photographs taken in the field and (b) soil profile photographs from the official database of the government of Mexico. The images were analyzed using the Gallegos-Bautista (GB) method. In the GB method, the horizon delineation of the soil profiles includes preprocessing the profile image with k-means segmentation; conversion of the preprocessed image to CIE L*a*b* (lightness, red/green value, blue/yellow value) and HSV (hue, saturation, value) color systems; k-means segmentation of HSV and CIE L*a*b* images, delineation of horizons, and clarity and topography determinations of the outlined horizons. The soil groups studied correspond to the Andosol, Cambisol, Luvisol, Alisol, Kastanozem, Phaeozem, Umbrisol, and Solonchak groups, some of which had contrasting color horizons, allowing us to identify how to follow the analysis of the digital images according to the horizons of the soil profiles.