In large industrialized cities, tons of particles containing heavy metals are released into the environment and accumulate on street surfaces. Such particles cause a potential risk to human health due to their composition and size. The heavy metal contamination levels, main emission sources, and human health risks were identified in 482 samples of street dust. Heavy metal concentrations were obtained by microwave-assisted acid digestion and ICP-OES. The results indicated that street dust in Mexico City is contaminated mainly with Pb, Zn, and Cu, according to the contamination factor and the geoaccumulation index. The pollution load index of the street dust was made with the concentrations of Pb, Zn, Cu, Cr, and Ni. The main sources of Pb, Zn, Cu, and Cr are anthropic, probably due to vehicular traffic. The highest levels of Cr and Pb in urban dust represent a health risk for children. Contamination limits were proposed for heavy metals in street dust of Mexico City. These limits might be useful to generate and apply public policies to decrease anthropic emissions of the heavy metals studied, particularly Cr and Pb.

The composition of urban dust can affect the health of urban populations, making it necessary to study its elemental composition and its sources. Our objectives were: a) to identify the main emission sources of heavy metals, and b) to evaluate the influence of land use and road type on the elemental composition of urban dust. 100 samples of urban dust taken in San Luis Potosí were analyzed using FRX. Descriptive statistics, Pearson's correlations coefficient, kriging interpolations, and analysis of variance were applied to the data. Cu and Zn were spatially associated with a metallurgical complex and, to a lesser extent, with an industrial park; Ca with fluorite and limestone industries, and Si with the surrounding soils. The highest concentrations of Cu, Zn, and Ca were found in mixed and industrial land uses. On the contrary, the highest concentrations of "natural elements" (Al, K, Si, Rb, and Y) were found in developable land and residential areas. The highest contents of Ca were found in secondary and primary roads. The conclusions were: a) the metallurgical complex is the main source of Cu and Zn, and b) the highest concentrations of Cu, Zn, and Ca were found in mixed and industrial land uses.

Heavy metals in street dust represent a risk to the human health due to their toxicity, persistence and bioaccumulation. Using the US Environmental Protection Agency (USEPA) assessment, here, we review the human health risks of such dust worldwide. The street dust in such cities is contaminated by As, Cd, Cr, Cu, Hg, Mn Ni, Pb and Zn beyond the median levels of the world soil background values. Among these elements, the median values of the hazard risk indices (non-carcinogenic risk) are highest for As, Cr and Pb and the median values of the risk indices (carcinogenic risk) for As are in the tolerable risk range for children and adults and in the case of Pb, the median value of the carcinogenic risk indices are also in the tolerable range for children. We emphasize that the level of heavy metals in street dust pose a considerable risk to the human health and require monitoring and approaches to reduce such toxic levels.

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Cities occupy a relatively small percentage of the Earth’s surface. However, they influence the entire biosphere, affect biodiversity and environmental conditions, which end up affecting human health and well-being. Therefore, it is necessary to evaluate the level of contamination by heavy metals in urban environments, as well as the possible ecological and human health risks. In this study, the urban dust of six Mexican cities was analyzed and it was found that all studied cities were contaminated, except for Mérida, when soil world background value was used as reference. In contrast, Mérida and Morelia were the most contaminated when a local background was used (decile 1). The concentrations in the cities for the metals Cu, Pb and Zn, decreased in the order CDMX > San Luis Potosí > Toluca > Morelia-Ensenada > Mérida. In the particular case of Cu and Pb, SLP accompanied CDMX as the most polluted city. For Mn and Fe concentrations, the order was CDMX > Toluca > Ensenada > SLP > Morelia-Mérida. No potential ecological risk was found due to contamination by Cu, Pb, and Zn, in the urban dust of the studied cities. However, the higher metal contribution to the potential ecological risk in all the cities was from Pb; and it represented a moderate ecological risk of more than 25% on CDMX, SLP, and Toluca sites. Pb can also be a potential risk for children’s health. In addition, chronic exposure to Fe and Mn could trigger many ailments. In the future, it is important to identify the main sources of Pb in cities and seek mitigation strategies to reduce the possible adverse effects that this metal may be causing.

Environmental pollution is a negative externality of urbanization and is of great concern due to the fact that it poses serious problems to human health. Pollutants, such as heavy metals, have been found in urban road dust; however, it is unclear whether the urban form has a role in its accumulation, mainly in cases where there is no dominant unique source. We collected 482 samples of road dust, we determined the concentrations of five heavy metals (Cr, Cu, Pb, Zn, and Ni) using inductively coupled plasma optical emission spectrometry (ICP-OES), and then we derived the pollution load index (PLI). After estimating the mostly anthropogenic origin of these pollutants based on global levels of reference, there were two main aims of this study. Firstly, to analyze the spatial correlation of heavy metals, and secondly, to identify the main factors that influenced the heavy metal concentrations in the road dust of Mexico City. We did this by using a spatial autocorrelation indicator (Global Moran’s I) and applying ordinary least squares (OLS) and spatial regression models. The results indicated low levels of positive spatial autocorrelation for all heavy metals. Most variables failed to detect any relationship with heavy metals. The median strip area in the roads had a weak (significance level of 90%) but consistent positive relationship with Cr, Cu, Ni, Pb, and the PLI. The distance to the airport had a weak (significance level of 90%) and inverse relationship with Pb. Manufacturing units were associated with an increase in Cu (significance level of 95%), while the entropy index was associated with an increase in Ni (significance level of 95%).

Elemental concentrations measured in 482 street dust samples from different urban and conurbated areas of Mexico City obtained using a portable energy-dispersive X-ray fluorescence spectrometer are reported. The data quality of eight different elements commonly used in pollution studies is evaluated, calculating the data precision and accuracy obtained with this handheld equipment. Precision for the various elements analyzed ranges between 1.2 and 15.9%, which can be considered as adequately precise for portable equipment. In the case of the accuracy, a maximum under-/overestimation of less than 20% was achieved. Pb and Zn correlation factors were 0.725 and 0.923, respectively. Similar mean Pb concentration values to those reported by ICP-OES were obtained. An average value of ~ 100 mg/kg for Pb concentration was estimated, which is significantly lower than the utmost permissible levels for residential/commercial usage. On the contrary, contamination factors calculated to identify the metal accumulation against those of the background values point from considerable to high contamination for 62 and 30% of the street dust samples analyzed, respectively. A comparison of the results recorded in Mexico City 10 years ago against those obtained suggests that no significant reduction in Pb concentration has occurred during this period despite the measures implemented to stop using leaded gasoline for three decades. Finally, the sample's low-amount requirements, simple nondestructive preparation procedure, and rapid elemental concentration determinations make portable XRF a promising geochemical determination technique for the fast and economic evaluation of contamination by heavy metals in large cities.

The COVID-19 pandemic has caused a decrease in outdoor activities, but an increase in indoor ones. This change in the intensity of land use has caused changes in pollution patterns. Urban dust contaminated with heavy metals can be a risk to the human population. Therefore, the objective of this work was to evaluate the pollution caused by heavy metals in urban dust indoors and outdoors due to changes in land use during the pandemic. Sampling was carried out by the Gomez Palacio citizens. The total number of urban dust samples was 330, 50% indoor samples and 50% outdoor sample. The elements studied were Ca, Cu, Fe, K, Mn, Ni, Pb, Rb, Sr, Ti, Y, Zn, and Zr. The heavy metals were measured through a portable XRF; the contamination factor and the load pollution index were used to assess the pollution level. The human health risk was evaluated with the USEPA methodology. Cu, Pb, and Zn presented higher concentrations indoors than outdoors, probably due to domestic factors, such as the age of the houses and the paint on the walls. Zn presented the highest pollution level among all the metals, outdoors and indoors; spatially, the sites sampled in the northwest, close to agricultural areas, presented the highest Zn pollution. Pb had a moderate pollution level in most of the samples (60%), but some samples showed a high Pb pollution. The health risk was considered within the acceptable levels for Cu, Fe, Ni, Pb, Zn. However, Mn deserves attention because the average of the samples slightly exceeded the USEPA safety limits for children. Children are at higher risk compared to adults. Indoor environments need to be better analyzed because they were shown to represent a higher risk to the population than outdoor ones due to heavy metal pollution by Zn, Cu, and Pb. The pandemic impacted land use intensity; this study reports an apparent effect of the pandemic on the amount and type of heavy metals indoors and outdoors.