What question did this study set out to answer?

The study aims to assess the health risks associated with toxic metal exposure in soils and vegetables from smallholder farms.

March 21, 2026Open Access

Human Health Risk Assessment From Exposure to Toxic Metals in Soils and Leafy Vegetables in Smallholder Farms of Northeastern Brazil

Key Points

The study aims to assess the health risks associated with toxic metal exposure in soils and vegetables from smallholder farms.
Sampled soils and leafy vegetables from 18 agricultural areas.
Analyzed samples for toxic metals including cadmium and lead.
Conducted human health risk assessments following USEPA guidelines.
Evaluated exposure pathways including ingestion and dermal contact.
Dominant exposure pathways were soil ingestion and vegetable consumption.
Children showed higher exposure doses and risk quotients than adults.
Noncarcinogenic risk estimates for adults were below concern thresholds.
Localized hotspots of risk were identified for children, especially concerning cadmium and lead.
Findings highlight the importance of age-specific assessment in risk evaluation.

Abstract

This study assessed human health risks associated with exposure to potentially toxic metals (PTMs) in soils and leafy vegetables cultivated in smallholder agricultural systems in Northeastern Brazil. Soil and vegetable samples were collected from 18 agricultural areas and analyzed for cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn). A harmonized human health risk assessment (HHRA) was conducted following US Environmental Protection Agency (USEPA) guidelines, considering soil ingestion, dermal contact, inhalation of resuspended particles, and dietary intake of vegetables for adults and children. Recalculated average daily doses indicated that soil ingestion and vegetable consumption were the dominant exposure pathways, whereas dermal and inhalation contributions were minor. Children consistently exhibited higher exposure doses and hazard quotients than adults due to lower body weight and higher intake rates. Noncarcinogenic risk estimates for adults remained below the threshold of concern in all areas. In contrast, localized exceedances of the hazard index (HI > 1) were identified for children, revealing spatially explicit risk hotspots rather than uniform risk across the study area. Lettuce and arugula contributed substantially to dietary exposure, particularly for Cd, Pb, and Cr. A conceptual sensitivity analysis incorporating hypothetical bioaccessibility fractions demonstrated that risk estimates near the regulatory threshold are sensitive to realistic reductions in bioaccessible metal fractions. At the same time, the highest risk hotspots remain robust under conservative assumptions. Overall, the findings represent conservative, screening-level estimates that underscore the importance of age-specific exposure scenarios, spatially explicit risk evaluation, and targeted risk management strategies in smallholder farming systems.

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