Distribution of Potentially Toxic Elements in an Andean Dairy System Affected by Volcanic Ash

This study evaluated the distribution of lead (Pb), cadmium (Cd), chromium (Cr), and arsenic (As), collectively referred to as potentially toxic elements (PTEs), in Andean dairy production systems affected by volcanic ash deposition and examined their relevance to raw milk safety. Samples of soil, forage, supplementary feed, drinking water, and raw milk were collected from 15 georeferenced dairy farms in Bilbao Parish, Ecuador. Soil and forage were assessed as interconnected environmental matrices, whereas supplementary feed and drinking water were considered additional exposure sources. PTE concentrations and selected physicochemical properties were examined using descriptive statistics, box plots, exploratory principal component analysis, and Spearman correlation analysis. Element distribution differed among matrices and did not follow a uniform or strictly linear soil–forage–milk pathway. Pb and As concentrations were lower in milk than in the environmental and dietary matrices, indicating limited occurrence in the final product under the conditions studied. Cd remained detectable in milk and therefore warrants attention because of its potential relevance to chronic dietary exposure. Cr occurred at comparatively higher concentrations in forage and supplementary feed but was substantially lower in milk. Exploratory correlations showed that Pb, Cr, and As varied positively with corrected density, protein, lactose, and total solids, whereas Cd showed inverse associations with these variables. These relationships should not be interpreted as causal because of the limited number of milk samples. Overall, the findings support an integrated, element-specific assessment of milk safety that considers environmental matrices, supplementary dietary inputs, drinking water, and milk composition. Larger seasonal studies and elemental speciation are recommended to clarify exposure pathways and potential risks.