Rossini-Oliva & López Nuñez 2024 — Urban garden vegetables and PTE exposure in Andalusia, Spain
This study measured eleven potentially toxic elements (As, B, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn) in 282 edible plant samples and 102 paired topsoils from urban community gardens across three Andalusian cities (Seville, Cordoba, Huelva) and two towns in the heavily contaminated Riotinto mining district (Nerva, Minas de Riotinto), collected 2021–2023. The same vegetables were simultaneously purchased from Seville local markets to benchmark urban garden concentrations against commercially available produce. Human health risk was assessed via hazard quotient (HQ), hazard index (HI), and carcinogenic risk for As; all HQ values were below 1 for all PTEs in all urban garden samples, and cancer risk for As remained within acceptable limits even in the mining-area gardens.
Key numbers
Vegetables sampled: lettuce, chard, tomato, onion, pepper, zucchini, and eggplant.
Analytical method: ICP-MS following acid block digestion (0.25 g DW per sample in HNO3). Accuracy verified against Apple Leaves NIST 1515 standard reference material. Units: mg/kg dry weight.
Soil contamination (mining area vs cities): Riotinto-area soils were more contaminated with As, Cr, Cu, Pb, and Zn than urban-city soils; urban soils from Seville, Huelva, and Cordoba showed higher As, Pb, and Zn than the peri-urban reference site.
Plant concentrations (selected key values from Tables 4–5):
- Cd: mean concentrations ranged from below detection to ~0.29 mg/kg DW depending on species and site; leafy species (lettuce, chard) consistently higher than fruiting (tomato, pepper, zucchini) or bulbous (onion) species.
- Pb: mean concentrations in leafy vegetables from city gardens (e.g. chard from market Mk: 0.272 mg/kg DW; lettuce from mining area Riotinto-TIN site: 167.8 mg/kg DW for soil Pb context). Pb in edible fractions generally below or comparable to EU limits in non-mining sites.
- As: present at low concentrations in most vegetables; carcinogenic risk (CR) for As was below established limits (<10⁻⁴) in all urban garden samples including mining-area soils.
- Market comparison: urban garden produce generally did not exceed market vegetable concentrations for most PTEs, except lettuce which had higher values for almost all elements vs. market lettuce.
Health risk: HQ < 1 for all PTEs across all urban garden types; HI < 1 in all sites. Cancer risk for As below 10⁻⁴ threshold in all sites including the Riotinto mining area.
Saharan dust event (March 2022): Lettuce and chard sampled after a documented red-rain Saharan dust transport event in Seville showed elevated PTE levels; these data were analyzed separately and are not included in the garden-comparison statistics.
Methods (brief)
Field-collected 2021–2023 from organic-practice plots in six municipalities plus a peri-urban reference and Seville market. ICP-MS (nitric acid block digestion, 0.25 g DW). QC: NIST 1515 Apple Leaves CRM. Total PTE set: As, B, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn. Total-metal analysis only (no speciation reported for As or Cr). Results on dry weight basis.
Limitation: Total As reported, not iAs speciation — for regulatory comparison to EU vegetable limits or HMT&C, iAs/tAs split is unknown. Significant within-species variation by site. Mining-area results reflect extreme historical contamination context not representative of typical agricultural soils.
Implications
Certification: Documents that Cd and Pb concentrations in Andalusian urban garden vegetables are generally below health-based guidance values, with lettuce as the highest-risk leafy species. Confirms leafy > fruiting > bulbous PTE accumulation hierarchy. Directly relevant to HMT&C product-category risk framing for leafy vegetables and fresh produce.
Courses: Clear real-world example of how urban soil contamination context (proximity to mines, traffic, industrial hubs) drives vegetable PTE concentrations. Mining-area chard/lettuce contrast vs. same-city market produce is a strong pedagogical case for the soil-to-crop pathway.
App: ICP-MS data for seven edible vegetable species across six locations provides Cd, Pb, and As range values for leafy vegetables and fruiting vegetables grown in urban/semi-urban Mediterranean contexts. Data gaps: no speciation for As; no Hg, Sn, U, or Al reported.