Stark et al. 2019 - Wild edible greens in the East Bay

Stark and colleagues combined urban foraging observations with soil and plant-tissue testing of wild edible greens from disadvantaged East Bay neighborhoods in California. The paper is routeable as direct leafy-greens occurrence context because it reports rinsed plant-tissue cadmium values, lead non-detects in tissue, and corresponding urban-soil metal measurements.

Key numbers

The first-page methods summary states that the field observations, soil tests, and tissue toxicology tests covered three study sites of roughly nine square blocks each in the East San Francisco Bay Area during 2014-2015.

The Methods section reports soil sampling at 28 Richmond and Oakland addresses on 2014-06-18 and tissue sampling targeted to the highest-soil-metal Oakland locations on 2015-05-12, with additional wet tissue samples collected on 2016-03-21.

Table 3 reports two soil locations with lead above the USEPA limit and identifies the highest soil values as Pb 700.9 mg/kg and Cd 58.8 mg/kg.

Table 5 reports dry plant-tissue metal results in mg/kg. The paper states that lead was below quantification limits in all samples. The text highlights sample 5005 wild lettuce with dry-tissue cadmium 5.383 mg/kg; using the reported dry-weight percentage 12.6%, the authors estimate original wet-tissue cadmium at 0.678 ppm.

The discussion states that even the highest measured tissue-metal amounts were below the US EPA reference dose assumptions for a standard serving after rinsing in tap water.

Methods (brief)

Soil samples were homogenized from 3-4 roadside subsamples per address. Plant tissues were rinsed in tap water as if making salad, then dried for botanical voucher preparation and laboratory analysis. Soil testing was performed by the University of Massachusetts Amherst Soil and Plant Nutrient Testing Laboratory, and tissue metals were measured by Brookside Laboratories. The paper reports total Pb and Cd results only; no arsenic or mercury speciation is involved.

Implications

Certification: This is urban leafy-greens occurrence context, not a market-benchmark row for packaged retail produce. It is still useful for showing that rinsed wild greens can carry measurable cadmium even when tissue lead is below quantification.

Courses: Useful case study on why upstream soil exceedances do not map one-to-one onto edible-tissue concentrations after rinsing and plant-specific uptake.

App: Can support a cautionary leafy-greens context note for urban foraging, with the rinsed-tissue and soil distinction kept explicit.

Wiki pages this source may touch

• Leafy / Green Vegetables, Other
• Leafy Greens
• Leafy Vegetables
• Cadmium
• Lead
• Soil-to-plant transfer of heavy metals

Verification notes

Recovered from the corpus-rescreen queue under the 2026-06-10 inclusion-by-default rule. The paper includes both routeable edible-tissue numbers and urban-soil pathway context. Product and ingredient routing is kept broad because the tested greens span multiple wild species rather than a single commercial crop row.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.