Co-occurrence, possible origin, and health-risk assessment of arsenic and fluoride in drinking water sources in Mexico: Geographical data visualization.

Arsenic and fluoride in drinking water present a significant challenge to public health worldwide. In this study, we analyze the results of one of the largest surveys of drinking water quality in Mexico: 14,058 samples from 3951 sites, collected between January and December 2017. We use these data to identify the distribution and possible origin of arsenic and fluoride in drinking water throughout the country, and to estimate the associated health burden. The highest concentrations appear in alluvial aquifers in arid northern Mexico, where high-silica volcanic rock likely releases both arsenic and fluoride to the groundwater. We find fluoride contamination to be significantly correlated with aridity (Pearson correlation = -0.45, p = 0.0105), and also find a significant difference in fluoride concentrations between arid and humid states (Welch's t-test, p = 0.004). We estimate population exposure by assigning to each town in Mexico the average concentration of any sampling sites within 5 km. Our results show that 56% of the Mexican population lives within 5 km of a sampling site, 3.05 million people are exposed to fluoride above the reference dosage of 0.06 mg/(kg ∗ day), 8.81 million people are exposed to arsenic above the limit of 10 µg/L, and an additional 13,070 lifetime cases of cancer are expected from this arsenic exposure alone. This burden of disease is concentrated in the arid states of north-central Mexico.

Small-scale and household methods to remove arsenic from water for drinking purposes in Latin America.

Small-scale and household low-cost technologies to provide water free of arsenic for drinking purposes, suitable for isolated rural and periurban areas not connected to water networks in Latin America are described. Some of them are merely adaptation of conventional technologies already used at large and medium scale, but others are environmentally friendly emerging procedures that use local materials and resources of the affected zone. The technologies require simple and low-cost equipment that can be easily handled and maintained by the local population. The methods are based on the following processes: combination of coagulation/flocculation with adsorption, adsorption with geological and other low-cost natural materials, electrochemical technologies, biological methods including phytoremediation, use of zerovalent iron and photochemical processes. Examples of relevant research studies and developments in the region are given. In some cases, processes have been tested only at the laboratory level and there is not enough information about the costs. However, it is considered that the presented technologies constitute potential alternatives for arsenic removal in isolated rural and periurban localities of Latin America. Generation, handling and adequate disposal of residues should be taken into account in all cases.