Lead in Urban Soil

Learn about safe levels of lead in soil, testing soil for lead, lead remediation, and how to take a few simple precautions to take when gardening in urban soil.


| Winter 2016-17



Raised beds

Using raised beds with clean soil can go a long way toward reducing the impact of lead in your garden soil.

Photo by istock/bgwalker

Growers are taking urban soil by storm. Guerrilla gardeners blanket abandoned properties with wildflower seeds, and guerrilla grafters coax fruit from ornamental pear and crab apple trees. Urban farmers crop vacant lots and high-rise rooftops. Meanwhile, neighbors band together to create gardens on barren ground, cultivating community as they garden together. Individually, gardeners line their foundations with beds of greens and beans, their patios and balconies with tomatoes and peppers in pots.

Green, growing plants and vibrant flowers drastically improve upon broken concrete, crumbling brick, rusted chain-link, and shattered glass. However, there are different challenges to gardening in the city, and one of the biggest issues for urban gardeners is lead in soils.

The Lead in Soil Around Us

Lead is a dull, grayish-white heavy metal, which is soft, workable, and incredibly useful both in its pure, metallic form and in many different compounds. Ancient Rome’s water flowed through lead pipes — the word plumber comes from plumbum, lead’s Latin name. Fashionable Elizabethan ladies and gentlemen wore cosmetics of red and white lead. Until relatively recently, medicines, paints, and gasoline all contained lead compounds. Stained glass windows, car batteries, and fishing weights all depend on lead.

As useful as lead may be, the stuff is also a health hazard. More than a half million children ages 1 to 5 in the United States are living with high enough levels of lead to damage their health, according to the Centers for Disease Control and Prevention (CDC). Lead poisoning affects children in many ways, including irritability, appetite loss, weight loss, muscle pain, vomiting and constipation, memory loss and learning difficulties, developmental delays, and even death in severe cases. Although adults can be affected by lead, children, especially those under 6, are at the highest risk of serious lead poisoning. Minor symptoms of lead poisoning will go away over time if the lead source is removed, but severe damage is permanent. There is no known safe threshold of lead in the blood for children; any lead at all in the body is a concern.

What Are Safe Levels of Lead in Soil?

What does this have to do with urban gardening? Lead contaminates many city soils. All soil contains a small amount of lead, measured in parts per million (ppm). Normal soils can contain 10 to 50 ppm of lead. Many governments and researchers have established guidelines for lead in soil. Some give a threshold as low as 100 ppm, and some set it at 300 or 400 ppm or more; overall, acceptable levels have continuously fallen since 1970. But lead levels in urban soil may exceed 200 ppm and can be as high as 10,000 ppm, particularly where lead-based paint has been in use.

Soil lead comes from many sources. Many buildings bear deteriorating coats of lead-based paints. Leaded gas exhaust lingers in soils near gas stations and busy streets. Discarded car batteries and other automotive wastes contaminate areas surrounding garages, junkyards, and manufacturing facilities. Lead also leaks into soil from stained glass windows, solder in discarded electronics, and even some aging brass fixtures.





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