One pleasure of growing up a child of the suburbs was kicking off my shoes each summer, throwing a basket over my arm and shuffling through the backyard to harvest raspberries, green beans, carrots and zucchini from my mom's vegetable garden. Since moving to Chicago, I've found growing food in the city can't be approached with the same innocent abandon, and not just because of the cigarette butts, condom wrappers and ubiquitous plastic bags I have to disentangle from my irises on a semi-weekly basis; the pollutants floating around our urban airspace settle on the ground, too. One of the biggest offenders in Chicago soil is lead.
Up until the late 1970s, lead was a common ingredient in house paint, so plots of land close to older homes can gather heavy metal from the buildings over the years. The prevalence of leaded gasoline until the mid-'80s means that ground near roads, driveways and alleys picked up a good deal of lead in the form of exhaust, too. 1985 may have been long enough ago for fashion to forget, but lead doesn't decompose; once it hits the dirt, it lingers there longer than my collection of gummy bracelets stayed in the back of my sock drawer.
A little bit of lead isn't necessarily a cause for panic; about 10 to 50 parts per million worth of lead occurs naturally in soil. Up to 100 PPM is a safe level for children and pets to roll around in (according to GreenNet, toddlers consume an aspirin-sized dose of dirt each day); up to 400 PPM is still considered acceptable for growing vegetables—for adults. Any higher concentration than that gets into the danger zone for adults, too.
My own plot is in the backyard and away from the house and alley, but it's such a brave little island in a vast sea of concrete, god knows what's been poured, dumped and flicked into it over the years. I decided to test the soil before even thinking of sticking in any edible plants. Several labs across Illinois test soil for lead and other contaminants. Opting to save time and money on postage, I picked the one located in Chicago: STAT Analysis. I called the lab first to see what sort of sample they required.
The phone was answered by Craig, who kicked off with a line of questions about the location of the garden: Is it next to a road? Are there any industrial buildings nearby? What about railroad tracks? When I affirmed the tracks, Craig immediately paused and said, "Just put in a raised bed." Railroads are huge polluters. In addition to the tar used in building railroads and the diesel emissions from heavy-rail engines, arsenic—arsenic—is used as a preservative for rails. Looks like I'd be sticking to flowers and shrubs in the main bed. But I was still curious about the lead content of my soil, so I dug up a couple six-inch-deep samples from different locations in the bed, sealed them in a Ziploc bag, and biked it down to STAT.
Two days later, the results came in via e-mail: over 600 PPM. The number sounded awfully high to me, but the GreenNet guide to lead contamination in soil labels 400-1000 PPM as "moderate," meaning safe for fruiting plants, like beans and berries, but no good for root vegetables and leafy greens. Plants themselves absorb very little lead, particularly if the soil is alkaline and rich in organic matter like compost, so most lead contamination is carried on the surface of the plant. If you have mild concerns about your produce, be sure to peel root vegetables and wash them in water with a splash of vinegar. Also, be careful to remove the outer layers of leafy crops.
I'll be sticking to pots and planters for my herbs and veggies, and I'm starting plans for a raised bed full of clean, lead- and arsenic-free soil topped with plenty of protective mulch. To get your own soil tested, contact STAT or another lab, and check out the EPA's info on lead in paint, dust and soil.
It took a move from the regimented lawnscapes of the suburbs to the congestion of a major metropolis for Sharon to look twice at what she puts in the trash, down the sink and into her own body. She reports fortnightly on her endeavors to change "greening" from calculated deviation to a practicable way of life. You can contact her here.