Contamination Near American Gardens

9,799 EPA-mapped PFAS sampling locations — public water utilities that tested positive for "forever chemicals." Manufactured since the 1950s for non-stick cookware, firefighting foam, and waterproof clothing, PFAS resist environmental breakdown because of their carbon-fluorine bonds. The EPA UCMR 5 program tests the public water systems that serve most American homes — a hit at a sampling point means the utility serving that area tested positive, and every parcel on its drinking and irrigation supply is affected, not just neighbors of the sample. Contamination clusters near military bases, airports, and fluorochemical manufacturing. The 2022 health advisory level is 4 parts per trillion — among the lowest contaminant thresholds in federal regulation.

The pattern rewards a precise read. Bioaccumulation factors vary by crop: leafy greens concentrate PFAS at 15–46× soil levels; fruiting crops show factors below 1. If your land is on a flagged municipal system, every property on that utility is in scope; check the consumer confidence report. Private-well users near a sampling point test directly. Carbon and reverse-osmosis filtration reduce PFAS in irrigation water meaningfully, and crop choice (fruiting over leafy) takes care of the rest.

14,809 Superfund sites — the most severe contamination in the federal record. The EPA tracks every site that meets the federal Hazard Ranking System threshold under the National Priorities List. Two pathways carry contamination toward a garden: groundwater migration, which can move dissolved metals and solvents laterally for hundreds of meters, and direct soil contact from historic dumping, spills, or airborne deposition. Many listings have completed remediation and operate under institutional controls; status is public.

A Superfund site within two kilometers is information, not a verdict. Many listings have completed remediation and operate under institutional controls that meaningfully reduce active risk — the EPA tracks status publicly. For native-soil planting, lean toward fruiting crops and tree fruits over leafy greens or root crops. Raised beds with imported clean soil and a barrier fabric eliminate the soil-contact pathway entirely. The constraint shapes the choice; it doesn't end it.

580,074 brownfields — former commercial land where legacy contamination may persist. The EPA's ACRES database catalogs every property in the program. The spectrum is wide: a former dry cleaner has a very different fingerprint than a former gas station or print shop. Many sites have completed cleanup under EPA or state programs and operate with institutional controls; raised beds with imported soil are the standard pattern for safe food production on the rest.

Brownfields reward reading. Cleanup status, the property's historic use, and the contaminants of concern are all public — and once you have them, the path forward usually clarifies. Many brownfields have become community gardens through the EPA's Brownfields-to-Greenfields framework, precisely because raised beds with imported soil and barrier fabric let safe food production happen on land with a complicated past.

737,077 underground storage tanks — the most common source near American homes. The EPA's UST Finder catalogs every registered tank in the country. When tanks corrode, they release petroleum hydrocarbons (BTEX: benzene, toluene, ethylbenzene, xylenes). Lawrence Livermore plume studies show subsurface plumes typically self-limit at around 800 ft from the source. Most tanks sit in commercial corridors near residential neighborhoods; tank status (active vs closed-and-remediated) shapes the risk profile.

UST proximity is one of the most actionable contamination signals you can get. Tank status matters — closed and remediated tanks pose substantially lower risk than active leaking ones. BTEX has low translocation to above-ground fruit, so tomatoes and tree fruits accumulate very little even when nearby soil is affected. The default playbook: raised beds with imported soil for root crops and leafy greens within 800 ft of an active leak; fruiting crops and tree fruits work in native soil. The mitigations are well-studied and they work.

64,741 mining records — heavy metals that persist in soil for decades. The USGS Mineral Resources Data System catalogs historic and active sites that leach arsenic, lead, cadmium, and mercury into soil and water long after operations end. Concentrations follow a power-law decay with distance: sharp drop from the source, never reaching zero. EPA smelter studies document measurable soil contamination extending 10+ kilometers downwind from large operations. Liming to pH 6.5+ reduces bioavailability significantly.

Soil chemistry is one of the most controllable variables in the equation. Liming acidic soils to raise pH above 6.5 binds heavy metals to soil particles and reduces uptake significantly — the metals stay put rather than moving into roots. Raised beds with imported clean soil over a geotextile barrier sever the pathway entirely. For any food production within 6 mi of a known mining site, soil testing for heavy metals is the right starting point.

107,742 county-level pesticide records — orchard land predating the 1940s is highest-flag. USGS NAWQA EPest provides ambient indicators of agricultural chemical application by county — not site-specific measurements. The data reflects cumulative footprint. Historic organochlorines (DDT, chlordane, dieldrin) persist in soil for decades. Lead arsenate, used widely in apple orchards before the 1940s, persists essentially permanently. The county number screens; site-specific soil testing decides.

County-level data reads as a screening signal that prompts the test, not a verdict. Site-specific soil testing closes the gap and runs cheaply through state extension offices. Raised beds with imported clean soil over a geotextile barrier eliminate the soil-contact pathway. Modern pesticides break down faster than the legacy chemicals — orchard land predating the 1940s is the highest-priority test. Cover crops and organic matter additions help bind residual compounds over time.

310,265 USGS nitrate records — public water samples, private-well samples, and groundwater monitoring combined. Contamination comes mainly from agricultural fertilizer runoff and failing septic systems. The USGS Water Quality Portal tracks the federal record nationwide — a mix of public water-system tests, private-well samples, and groundwater monitoring wells. The EPA drinking-water standard is 10 mg/L; municipal systems are regulated to that threshold, but agricultural-region utilities occasionally exceed it, and a hit at a public water sampling point affects the utility's whole service area. A hit at a groundwater well speaks to local private-well users in that radius. Certain leafy greens — arugula, spinach, lettuce — are well-documented natural nitrate accumulators.

Nitrate is one of the most testable, most fixable contaminants in the federal record. Municipal users check the utility's consumer confidence report for exceedances near or above 10 mg/L; private-well users test the water directly. The test is cheap, results return quickly, and the answer is binary above 10 mg/L. Crop selection takes care of the rest — fruiting crops and tree fruits show low accumulation. Cover crops and avoiding over-fertilization further reduce nitrate leaching in garden soils over time.

10,110 Concentrated Animal Feeding Operations — biological risk, not chemical. The EPA's NPDES program tracks large-scale livestock and poultry facilities. The contamination profile is biological: ammonia emissions and pathogen risk (E. coli, Salmonella, Cryptosporidium) drive the concern, not heavy metals or solvents. Pathogen risk shows up most acutely on crops eaten raw — leafy greens face the highest exposure from splash and aerosol deposition from manure handling. Washing, cooking, and row covers handle most of it.

CAFO proximity is essentially a food-safety question, and food-safety questions have well-established affordances. Cooking eliminates pathogen risk completely. Washing under running water reduces contamination on raw-consumption crops substantially. Row covers cut splash and aerosol deposition. Fruiting crops elevated above the soil face minimal direct exposure. Most of the playbook lives in standard food-safety practice rather than in any specialized mitigation — closer than any other contamination class to "kitchen-handled, not field-handled."

73,333 EPA-tracked TRI facilities — downwind exposure 2–3× higher than upwind. Industrial sites report annual chemical releases to air, water, and land under federal disclosure law. The primary pathway from a TRI facility to a garden is airborne deposition, following Gaussian plume dispersion. Risk is strongly wind-direction dependent: a parcel downwind of an active facility faces meaningfully higher exposure than one upwind or crosswind. The EPA's TRI Explorer makes the per-facility chemical mix public.

Crop selection becomes the most powerful lever here. Leafy greens accumulate the most because their broad surfaces catch deposition; fruiting crops with peelable skins accumulate far less; tree fruits, elevated and protected by bark, accumulate the least. Not every TRI release poses equal risk — the EPA's TRI Explorer makes the per-facility chemical mix public. Wind, chemical mix, and crop choice together give a reading that proximity alone never can.

Every interstate and US/state highway — concentrations highest within 100 ft, near-background by 1,000 ft. Census TIGER/Line PRISECROADS catalogs the federal record of major roads. Vehicles emit lead from pre-1986 leaded gasoline still bound in roadside soil, polycyclic aromatic hydrocarbons from incomplete combustion, and fine particulates from brake and tire wear. The EPA's Near-Road Air Quality 2010 evidence shows the distance-decay curve: roughly 70–80% drop by 500 ft. Wind asymmetry adds a 2–3× downwind/upwind difference at the same distance.

This is one of the most readable contamination patterns in the federal record — distance does most of the work, and wind direction sharpens the read further. For gardens within 500 ft, raised beds with imported clean soil sever the soil-contact pathway. A vegetative buffer between road and growing area reduces particulate deposition. Leafy greens warrant the larger setback; fruiting crops accumulate the least. The map encodes both axes — see the asymmetry, not just the proximity dot.