Speaking of Lead Part 3: the Solution (or, What to Do About Lead in Your Soil)

Now that the shock of the lead discovery has worn off and we have come to understand that a leaden raspberry patch is unlikely to kill anyone, I feel bound to tell you about my response to the lead contamination in the soil next to the garage, i.e., the designated raspberry site. 

After the various stages of tooth-gnashing, hand-wringing, and consternation gave way to disillusionment, fatigue, and finally a sense that this was not in fact the end of the world or even my career as an edible gardener, I built a raised bed for the raspberries. Actually I hired someone to build it for me, since it required  heavier cutting tools than I have or like to use. I had the timbers already (hand-me-downs from my next-door neighbor), which were the perfect size, and I had a few other projects that my landscaper, Roberto Sanchez, was more than happy to undertake.

So Roberto and his guys showed up one day in August with the tools and a truckload of dirt. I had cleared the ground for them and stacked the timbers suggestively:

I was pleased with the site, which was nicely tucked out of the way next to the compost bin:

I had read that a raspberry's root system will extend about 20 inches below the surface; these timbers stacked up to 18 inches or so. I did not line the bottom with garden fabric, although that is technically the best practice. But I know that no system is foolproof; my aim was not to shield the raspberry plants from every last speck of lead dust, which would be impossible, but to provide them with a basically clean, stable environment, knowing that very little lead would make its way up to the berries. It is also worth noting that the soil underneath this raised bed, while full of lead, is also pretty full of organic matter, since it was the former site of my garden waste compost pile. And organic matter, I have learned, binds with lead and makes it less likely to be taken up by plants. So there!

A word about the imported soil: I asked Roberto where he normally ordered his topsoil, and did they test for lead. He typically buys it from Lurvey Landscape Supply in DesPlaines, a very large operation, and he thought that yes, they did test their soil. However, a phone call to Lurvey revealed otherwise. Odds are it was fine, but since I am in the business of broadcasting this story to urban gardeners everywhere, I figured I should set a good example. 

So I called Lake Street Landscape Supply, which is where the city buys materials for its projects, according to my source Aaron Durnbaugh, the city's Deputy Commissioner for the Division of Natural Resources and Water Quality (say that ten times fast). I talked to Pete, who assured me that yes, they test their soil for lead. He recommended a soil mix called Low Soil, which has a relatively low pH level—that's what the raspberries like.

Roberto was happy to oblige and ordered three cubic yards of Low Soil from Lake Street, which set me back about $140. About half of the soil went to the berry patch and half went to some flower beds that I was expanding. A few hours later I had plopped my raspberries in their new beds and was giving them a good soaking.

That's fine, Ange, you say, but how does this all of this apply to the rest of us? What should I be doing about the lead in my soil? First, let's review:

What we know about lead in urban backyard soils:

1) It's everywhere. If you live in Chicago (or any old city) it's probably wise to assume that you have lead in your soil. If it didn't come from years of flaking house paint, it came from gasoline (evaporated or spilled) or from an old industrial source.

If you want to know whether your property (or any Chicago property) has a chemically sordid past, the City of Chicago's Greencorps program will provide you with a Phase I assessment, which is a land-use history. It's a matter of public record, so all you need is a PIN and you can find out whether a given lot was ever home to a paint factory, auto shop, dry cleaner, waste dump, etc.

2) Your house has a halo. Lead concentration tends to be worst in the soil next to old houses (pre-1978), where the paint chips have been falling since soon after the house was built. Brick houses are not immune—they still have windows and sills, some of the peelingest parts of any house.

3) It's not going away. Lead is a very stable element—"molecularly sticky" is one term I've heard. The down side of this is that, obviously, that we're never going to be rid of the damn stuff. The up side is that it's not leaping up out of the soil and grabbing anybody by the throat (at least not without provocation). If you can keep it contained, it will more or less mind its own business, leaving you and your children to yours. And as I mentioned earlier, lead binds to organic matter, so if your soil is heavily composted, the lead is less likely to be "bioavailable," or easily taken up by plants.

4) It will be taken up by some plants, but not all. Certain plants are considered "hyperaccumulators" of lead, such as

• sunflowers

• brassicas (kale, cabbage, broccoli, brussels sprouts)

• turnips and rutabagas

• ragweed

• corn

In these plants, any lead is likely to be taken up through the roots and even into the plant shoots. It is not harmful to the plants—only to you if you eat enough of them. (Phytoremediation is the practice of removing metals from the soil by planting and harvesting hyperaccumulators. I have been planting sunflowers next to my garage for several years with this in mind, but having read up on this I now think it a vain effort. As far as I can tell, phytoremediation is incredibly slow and complicated and doesn't make sense for home gardeners.)

Fruiting crops (i.e., beans, apples, squash, tomatoes) are the safest from lead uptake—this seems to be almost a non-issue. However, lead can frequently be found on your leafy greens, because

5) It's dusty. All of my reading and conversations suggest that the greatest danger posed by lead is that it is kicked up along with soil dust, which can then stick to your edible leafy greens, your gardening pants, your shoes, or your children's hands.

And now for the recommendations:

What should I do about lead in my soil?!?

1) Wash. Given the danger posed by lead in your soil dust, the smartest (and easiest) thing you can do is to make sure that dust doesn't get into your house, your food, your mouth, or your children's mouths. Here are some simple precautions:

• After gardening, leave your dirty clothes and shoes at the door, and take a shower. Make your kids take a bath after playing in the dirt. Make sure everybody washes their hands after being outside and before eating.

• Wash your vegetables. Scrub 'em with soap and water (yes, I said soap) or a vinegar-water solution.

• Keep your floors clean, especially in the summer, when you're tracking in a lot of dirt.

This first point was sort of a blow to me, as I've always held a stubbornly romantic notion of "good, clean, dirt." At 5600 parts per million, I'm sad to say it ain't so.

2) If you want, test your soil. A quick internet search or your state or county extension office will give you a list of soil labs. It shouldn't cost more than $30/sample, and some places will certainly do it for less. Follow the lab's sampling instructions; for different fees you can have your soil tested for nutrients, lead, or any number of other contaminants.

Having my soil tested was vivid and startling proof of what I'd already been told—that lead was everywhere in Chicago soil. If you feel you've already been sufficiently startled by my story, I think you can't go too far wrong in assuming the worst and saving yourself the thirty bucks.

If you do have your soil tested, know that anything higher than 300–500 parts per million (the former for children, the latter for adults) is not generally considered safe for edible planting.

3) Keep it down. Bare dirt is the worst thing you can have, especially where children are playing. Better to plant grass or some other ground cover to keep the dust from flying up. At the very least, you can put down wood chips.

4) Build raised beds. The safest way to protect your vegetables from the Lead Menace is to plant them in foot-high raised beds, lined with garden fabric and filled with imported, lead-free dirt. (Ask your soil supplier about its testing practices.) You can also plant in containers—just remember that they need extra water.

5) Mind your compost. If you are in the habit of composting your yard waste, wonderful. Keep it up. But it's probably not a good idea to put this compost in your vegetable garden—better save it for the flower beds. I put my general yard waste in one pile and my kitchen scraps in a separate bin, where I also feel free to compost any waste from my clean raised beds. The compost from the yard pile goes in the flower beds, and the compost from the bin goes in the vegetable beds.

But for God's sake, don't give up on feeding your vegetables with compost! Building your soil is one of the most important things you can do for the little guys.

6) Don't freak out. The world is a dangerous place. Cities are full of pollution. Our food is full of pesticides, hormones, antibiotics, and preservatives, and most of us are still walking around, even if a little fatter and sicker than in previous generations. It is my unscientific but fairly well-considered opinion that the health, social, financial, and spiritual advantages of growing your own food FAR outweigh the risks of consuming what little lead creeps into that food, especially if you exercise some basic precautions.

So happy gardening and bon appetit!

Comments

[Michelle]

So, you segregate your yard waste from your food waste? I find this interesting, as here in Berkeley they collect EVERYTHING, together, in one green bin.

-Michelle

[Angela Bowman]

Re: [nest] Michelle submitted a comment to Speaking of Lead Part 3: the Solution (or, What to Do About Lead in Your Soil)

I do separate yard and food waste, but only because the yard waste doesnt fit in the compost bin. I keep it in a separate (much bigger) pile on the side. Keep in mind I am composting this stuff and not having it collected. Does the city of Berkeley really pick up your food compost? Thats amazing. So this must be separate from your trash and also from your recyclables. Do tell!