--- topic: "Garden Soil Contaminants" title: "Lead and Other Contaminants in Garden Soil" order: 1 description: "Lead from old paint, gasoline and pesticides is the main soil worry, mostly through dust children swallow. How to test, amend, grow and wash safely." question: "Is your garden soil safe to grow food in?" answer: "Likely, but test first: soil near old buildings, roads or orchards can hold lead, and children swallowing soil and dust matters more than the vegetables." actions: - "Test soil for lead before growing food, especially near old homes, roads or orchards; EPA screens at 200 ppm [5], and 81% of 141 Boston gardens topped 400 ppm [1]." - "If lead is high, add compost, use raised beds of clean soil, mulch bare ground, keep soil outdoors; compost cut vegetable lead 50–71% [6], but dust recontaminated raised beds [1]." - "Wash all produce well and rinse leafy greens thoroughly: household washing removed about 56% of lead from leafy vegetables on average, but not all of it [4]." cautions: - "Children and pregnant people are most vulnerable: low blood lead goes with lower IQ [7] and reduced fetal growth [5]; keep children off bare soil and ask about lead testing." - "Do not reuse pressure-treated lumber made with chromated copper arsenate (CCA) for garden beds or play areas; CCA is restricted in most countries, but older structures still leak metals [8]." - "On a former orchard or near an old industrial site, test for lead and arsenic: 4 of 19 Washington childcare centers on former orchards exceeded lead standards, 8 arsenic [9]." confidence: 3 confidenceNote: "Field surveys, exposure models and reviews agree that swallowed soil and dust matter most, but crop contamination by clinging soil particles varies by site and some models show real risk." evidenceSummary: rctCount: 0 observationalCount: 7 metaAnalysisCount: 1 totalParticipants: "1,300+" replicated: true newestStudyYear: 2024 references: - id: "1" pmid: "18456252" title: "Urban gardens: lead exposure, recontamination mechanisms, and implications for remediation design" authors: "Clark HF, Hausladen DM, Brabander DJ" year: 2008 journal: "Environ Res" - id: "2" pmid: "26828157" title: "Lead in Urban Soils: A Real or Perceived Concern for Urban Agriculture?" authors: "Brown SL, Chaney RL, Hettiarachchi GM" year: 2016 journal: "J Environ Qual" - id: "3" pmid: "15016510" title: "Lead levels of edibles grown in contaminated residential soils: a field survey" authors: "Finster ME, Gray KA, Binns HJ" year: 2004 journal: "Sci Total Environ" - id: "4" pmid: "36539086" title: "Managing health risks in urban agriculture: The effect of vegetable washing for reducing exposure to metal contaminants" authors: "Augustsson A, Lundgren M, Qvarforth A, et al." year: 2023 journal: "Sci Total Environ" - id: "5" url: "https://www.epa.gov/system/files/documents/2024-01/olem-residential-lead-soil-guidance-2024_signed_508.pdf" title: "Updated Residential Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities" authors: "US Environmental Protection Agency, Office of Land and Emergency Management" year: 2024 journal: "US EPA memorandum" - id: "6" pmid: "25602223" title: "Safety of gardening on lead- and arsenic-contaminated urban brownfields" authors: "Defoe PP, Hettiarachchi GM, Benedict C, et al." year: 2014 journal: "J Environ Qual" - id: "7" pmid: "16002379" title: "Low-level environmental lead exposure and children's intellectual function: an international pooled analysis" authors: "Lanphear BP, Hornung R, Khoury J, et al." year: 2005 journal: "Environ Health Perspect" - id: "8" pmid: "34063914" title: "Environmental and Health Hazards of Chromated Copper Arsenate-Treated Wood: A Review" authors: "Morais S, Fonseca HMAC, Oliveira SMR, et al." year: 2021 journal: "Int J Environ Res Public Health" - id: "9" pmid: "27823776" title: "Legacy lead arsenate soil contamination at childcare centers in the Yakima Valley, Central Washington, USA" authors: "Durkee J, Bartrem C, Möller G" year: 2017 journal: "Chemosphere" - id: "10" pmid: "26555531" title: "When Vacant Lots Become Urban Gardens: Characterizing the Perceived and Actual Food Safety Concerns of Urban Agriculture in Ohio" authors: "Kaiser ML, Williams ML, Basta N, et al." year: 2015 journal: "J Food Prot" - id: "11" pmid: "31611401" title: "The concurrent decline of soil lead and children's blood lead in New Orleans" authors: "Mielke HW, Gonzales CR, Powell ET, et al." year: 2019 journal: "Proc Natl Acad Sci U S A" - id: "12" pmid: "37474053" title: "Urban vegetable contamination - The role of adhering particles and their significance for human exposure" authors: "Augustsson A, Lundgren M, Qvarforth A, et al." year: 2023 journal: "Sci Total Environ" --- Garden soil can hold lead and other contaminants, especially near older homes, busy roads, former orchards or industry. The bigger risk is usually children swallowing soil and dust, not eating the vegetables [1][2]. Most fruiting crops take up little lead, but leafy greens and root crops can carry more, so testing, clean raised beds and thorough washing are sensible [3][4]. ## How it works ### Where the contamination comes from Lead is the most common contaminant in urban soil [2]. In soils tested at six sites in Ohio neighborhoods, paint appeared to be the main source of lead, and the soils also held zinc, cadmium and copper [10]. In New Orleans, median topsoil lead fell 44% over 15 years while children's blood lead fell 64%, and the authors concluded that falling topsoil lead was an important factor in the decline [11]. In Washington's Yakima Valley, orchards were sprayed with lead arsenate from the early 1900s to the 1950s, leaving lead and arsenic in the soil [9], and older pressure-treated wood made with chromated copper arsenate (CCA) can leach arsenic [8]. ### How people are actually exposed In an exposure model for 141 backyard gardens in Boston, homegrown produce accounted for about 3% of a child's daily lead exposure and swallowed fine soil for 82% [1]. A review reached a similar view: plant uptake of lead is typically very low, with exceptions in low-growing leafy crops, where soil splashes onto leaves, and in root vegetables such as carrots [2]. A field survey found most lead concentrated in roots, fruiting vegetables below the detection limit, and some leafy vegetables and herbs high enough to add to body burden [3]. ### What the guideline numbers mean In January 2024 the US EPA lowered its residential soil lead screening level from 400 to 200 parts per million, or 100 where other lead sources exist. These are screening tools for flagging sites, not cleanup rules or a line between safe and unsafe, but they help you read a lab result [5]. ### What reduces the risk Compost and soil amendments diluted soil lead and cut lead in vegetables by 50-71% in field plots [6]. Raised beds help but can be recontaminated by wind-blown lead dust, so they need maintenance [1]. Household washing removed about 56% of lead on leafy vegetables on average, though adhering soil particles can remain [4][12]. Keeping soil out of the house is a standard practice [2]. For another lead source, see [Lead in Tap Water](/lead-in-water/neurotoxin-in-tap-water). For a metal that arrives with fertilizer and crops, see [Cadmium in Food](/cadmium-in-food/dietary-sources-and-health-risks). The benefits of growing food are covered in [Is Gardening Good for Your Health?](/gardening-and-health/is-gardening-good-for-your-health). ## The evidence in detail ### Lead in garden soil and crops Clark and colleagues tested 141 backyard gardens in Roxbury and Dorchester, Massachusetts, by X-ray fluorescence and found 81% above 400 micrograms per gram [1]. Raised beds started at 150 (plus or minus 40) micrograms per gram but averaged 336 four years later, and wind-transported particles with a lead-paint signature were the mechanism [1]. Their exposure model attributed about 3% of children's daily lead exposure to homegrown produce and 82% to ingestion of fine soil (under 100 micrometers) [1]. Limitations: a model with assumptions, and one neighborhood; the authors conclude remediation needs constant maintenance and may need to happen at neighborhood scale. Finster and colleagues surveyed garden plants grown in contaminated residential soils, washing samples with detergent or water, and found lead mostly in roots (root-to-soil ratios 0.02-0.51), with shoot-to-soil ratios up to 0.10 [3]. Fruiting vegetables were below the 10 ppm detection limit, while some leafy vegetables and herbs had levels that could add to body burden [3]. Defoe and colleagues set up plots in Tacoma (soil lead 51-312 mg/kg, arsenic 39-146) and Seattle (lead 506-2,022, arsenic under 20) and tested a biosolids mix or compost plus dolomite [6]. Amendments diluted soil lead by 10-23% in Tacoma and 20-50% in Seattle, lowered vegetable lead by 50-71% and arsenic by 46-80%, and laboratory cleaning reduced the transfer of lead and arsenic from vegetables [6]. Limitations: two sites and three vegetables. ### Washing and clinging particles Augustsson and colleagues analyzed 63 samples of chard, kale, lettuce and parsley grown near a busy road in Sweden, with half of each sample washed [4]. Washing removed on average 56% of lead, 45% of arsenic, 13% of copper and 7% of cadmium, and without washing the average daily lead intake would be 130% higher [4]. A companion paper found that vegetables still carried 0.05-1.3% adhering particles by weight after washing; at 0.5%, an adult eating an average amount of vegetables could ingest about 100 mg of particles a day [12]. Particles supplied 25-29% of vegetable lead, and across 20 urban soils from five European countries, lead posed the greatest risk, with hazard quotients often above 1 for particle ingestion in adults and 3-6 year-olds [12]. These are models of hypothetical scenarios, but they suggest that limiting dust and soil splash matters as much as choosing clean soil. ### Optimistic and cautious readings Brown and colleagues concluded that it is highly unlikely that urban agriculture will raise children's blood lead, because gardening tends to improve soil, plant uptake is typically low and little lead is absorbed when eaten with food, and that the benefits of urban agriculture far outweigh the risks [2]. The Swedish modeling is more cautious about clinging particles [12]. The views are compatible: the open question is how much adhering soil matters, which varies by site. ### Children and soil lead Mielke and colleagues compared 274 New Orleans communities across about 15 years: median topsoil lead fell 44% (99 to 54 mg/kg) while children's blood lead fell 64% (3.6 to 1.2 micrograms per deciliter) [11]. This is an ecological comparison, and other lead sources fell too. Lanphear and colleagues pooled seven cohorts of 1,333 children followed from infancy and found IQ fell by 3.9 points (95% CI 2.4-5.3) as blood lead rose from 2.4 to 10 micrograms per deciliter, with a steeper loss per unit at lower levels than at higher ones [7]. ### Other sources: pesticides, treated wood, vacant lots Durkee and colleagues sampled soil at 19 childcare centers in Washington's Yakima Valley, where orchards were sprayed with lead arsenate from the early 1900s to the 1950s [9]. Four (21%) exceeded the regulatory standard for lead and eight (42%) for arsenic, and historic land use was significantly associated with elevated levels [9]. A review of CCA-treated wood notes that it is restricted in most countries but still present in outdoor structures that leak metals, with children the main concern [8]. In soils from six locations in low-income Ohio neighborhoods, lead, zinc, cadmium and copper were elevated, paint was the main source, PAHs were well below levels of concern and no foodborne pathogen targets were detected; long-established gardens had lower contamination, perhaps because tillage mixed in cleaner soil [10]. Limitation: six sites. ### Bottom line (confidence 3 of 5) Lead in soil is a real, well-documented exposure, mainly through swallowed soil and dust, and testing is worth doing before you grow food in older urban or orchard soils. Crop uptake is usually low, but leafy and root crops and soil clinging to leaves can matter at some sites. The protective steps are simple and cheap: clean beds, compost, mulch, washing, and soil kept outside.