Lead in soil.

Most yard soil in older U.S. cities is contaminated with lead from two sources: weathered exterior paint that's been falling off houses for decades, and tetraethyl-lead exhaust deposits from the leaded-gasoline era (1923–1996). The dirt your kid plays in remembers.

Why soil holds lead for decades.

Lead does not biodegrade. Once it lands in soil, it stays in the top 6 inches for hundreds of years. Two big legacy sources put it there in the first place: leaded paint chipping off the exterior of houses (the dripline along the foundation is the worst), and tetraethyl-lead emitted from cars during the 1923–1996 leaded gasoline era, which deposited along every road, street, highway, and downtown block in America.

EPA's residential soil cleanup standard is 200 ppm in play areas, 400 ppm in non-play areas. Most pre-1978 urban yards in the U.S. exceed at least one of those thresholds. Boston, Chicago, Detroit, Newark, New Orleans, Cleveland — typical urban yard soil samples come back at 300–1,500 ppm in the dripline along the house and 150–400 ppm in the open yard.

The hot spots in a typical yard.

Soil lead concentrates predictably. Walk the yard once and you can identify the spots that need testing first.

• The dripline. The strip of dirt directly below the eaves of pre-1978 painted houses. Decades of paint chips have ended up here.
• Within 10 feet of the road. Tetraethyl-lead exhaust deposits during the 1923–1996 era settled along every road shoulder.
• Old play areas. Where a swing set, sandbox, or kid play structure has been for years.
• Vegetable garden beds. Particularly leafy greens and root crops, which uptake soil lead into the edible portion.
• Around old painted fences and outbuildings. Same story as the house dripline.
• Demolition fill from prior buildings. Common in city lots that have been redeveloped.
• Industrial-adjacent properties. Anything within a half-mile of a former smelter, battery plant, or paint factory.

How to test the soil.

1. Pick three zones. The dripline, the play area, and the garden. These are the highest-traffic spots for kids and the highest-risk spots for lead.
2. Take samples from the top 2 inches. Lead concentrates in the top layer. Scoop a small sample from each zone into a clean container.
3. Wet the sample slightly. The reagent works on damp soil, not dry dust.
4. Spray FluoroSpec on the soil. A few sprays is enough.
5. Wait 60 seconds, then UV. Bright green glow = lead. The brighter the glow, the more lead.
6. For a quantitative number, send a sample to your state extension lab. Most state cooperative extension services run soil tests for $15–25 per sample. Ask for "lead, total" and "lead, bioaccessible." The bioaccessible number is what matters.

If your soil tests positive.

You don't have to remediate the whole yard. The realistic interventions are: cap high-risk play areas with 6 inches of clean wood chips or sod, build raised garden beds with imported clean soil and a barrier, and run a wet-towel ritual for shoes and hands when kids come inside. Most exposure happens through hand-to-mouth contact and tracked-in soil dust, not through standing on the dirt.

Phosphate amendments (bone meal, fish meal) bind soil lead into less-absorbable forms over time. Compost dilutes high-lead soil. Sod or wood chip cover physically separates kids and dirt. None of these is expensive or complicated.

Test the dirt your kid plays in.

The dripline. The play area. The garden beds. The sandbox. One spray, 60 seconds, UV. Done.