Yardwork: Gardening is heavy metal
Welcome to Yardwork, a summer yard and garden miniseries from Outside/In.
We’re sharing three stories about our relationships with the land around us:
the front yard, the backyard, and down the block.
This is part two.
Sometimes, when Maureen McMurray is digging in her backyard garden, she encounters something she didn’t expect: a lump of coal. She’s planted vegetables in the same soil for a few years now. But as she prepared for an upcoming growing season, she wondered: is her homegrown produce poisoning her family?
The answer is nicer than you might think.
Featuring Maureen McMurray, Nate Bernitz, and Ganga Hettiarachchi.
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Maureen’s lab data from the UNH Cooperative Extension soil test. Note: refer to the total lead result, which uses the EPA method, not the Mehlich 3 test result. When comparing these heavy metal concentration to the from the Cornell Small Farms Program and the NC State Extension, the concentrations of most of the other heavy metals are relatively low. The other elevated result in her soil is arsenic.
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LINKS
Find your state’s cooperative extension and soil testing service in this directory.
Cornell Small Farms Program offers a guide to soil contamination, including ranges of safe levels, with the caveat that toxicity depends on factors like soil texture, pH, and organic matter.
The EPA’s primer to lead in soil.
More information on managing the health risks of lead in New Hampshire soils from the UNH Cooperative Extension.
This open source paper goes even deeper on issues of urban gardening, soil contamination, and public awareness.
CREDITS
Hosted by Nate Hegyi
Reported and produced by Justine Paradis
Edited by Taylor Quimby
Additional editing help from Nate Hegyi, Felix Poon, Rebecca Lavoie and Jessica Hunt.
Executive producer: Rebecca Lavoie
Title art and photo: Justine Paradis.
Special thanks to Tom Lemien, Anna Paltseva, and Jim Garvin.
Music by Walt Adams, Nul Tiel Records, Alexandra Woodward, Martin Gauffin, Blue Dot Sessions, and Arthur Benson.
Outside/In theme by Breakmaster Cylinder
Outside/In is a production of New Hampshire Public Radio
If you’ve got a question for the Outside/In[box] hotline, give us a call! We’re always looking for rabbit holes to dive down into. Leave us a voicemail at: 1-844-GO-OTTER (844-466-8837). Don’t forget to leave a number so we can call you back.
Audio Transcript
Note: Episodes of Outside/In are made as pieces of audio, and some context and nuance may be lost on the page. Transcripts are generated using a combination of speech recognition software and human transcribers, and may contain errors.
Nate Hegyi: Today’s tale starts in the garden.
[opening garden gate]
Justine: He-ey! You’re dressing the part with your overalls.
Nate Hegyi: A garden in Concord, New Hampshire, that Justine visited a little while ago, to talk with Maureen McMurray.
Maureen McMurray: So this is my garden… Tomatoes do really well here. Snap peas. You’ll see there are some strawberries. I have a little section that’s just all herbs, and they thrive.
Nate Hegyi: Full disclosure: Maureen used to work on our show. But these days, she’s a listener.
And for the past few years, Maureen’s been living in a cute neighborhood near the park with her family. She and her husband have a 7-year-old.
And when they moved in, she dug up the bushes in an old flower bed to grow vegetables.
Maureen McMurray: And I’ve grown things from seed back here. So, the plants are alive.
Nate Hegyi: And the reason Maureen is clarifying here that the plants are in fact alive is because often, she’ll be digging in her vegetable garden… and suddenly… her shovel will hit something …
Maureen: *clink*
Nate Hegyi: A distinctive, porous, rock-like lump…
Maureen: I mean you can see it from here.
Justine: Oh yeah, from here you can see it.
Maureen: There are just chunks…
Justine: That’s a lot of coal.
MUX: Pembroke Pines, Walt Adams
Nate Hegyi: And her question is…
Maureen: I’m growing stuff that’s in the same soil as all of this coal… am I poisoning myself and my family?
MUSIC SWELL
Nate Hegyi: This is Outside/In. I’m Nate Hegyi.
Justine Paradis: And I’m Justine Paradis.
Nate Hegyi: And this is Yardwork, our summer yard and garden miniseries. We’ve got three stories on our relationships with the land around us. This is part II: the backyard vegetable patch.
Justine Paradis: For the past few years, Maureen’s been growing vegetables in a backyard in New Hampshire’s capital city… in the same soil where she’s also been finding lumps of coal. So, does this mean that the soil is contaminated?
Nate Hegyi: Today, Justine reports on how to know if it’s safe to grow vegetables in the soil in your backyard.
MUX FADE
Justine: At first glance, coal sounded to me like an odd thing to find, mixed evenly into the soil, but upon further investigation, I learned that maybe it’s not that weird. Maureen’s house was built in 1880. And when I emailed a local historian to ask him about this, he told me that at the time almost everyone in this city would have heated their house with a coal furnace. Even in 1940, that was still true for a little over a third of US homes. Once the coal burned, people had to shovel out the ash. Sometimes they put the ash in cans on the curb to get picked up, but other times, people would bury it in the yard to fill in low spots.
So, maybe that happened at Maureen’s place.
For our purposes, I’m comfortable saying these chunks were somehow leftover from the days of home coal furnaces, and it’s probably more common than I realized.
But back to our main question: is it safe to grow vegetables in the same soil?
Nate Bernitz: I think it’s a really good question that everybody should be asking. Is the produce that I’m growing and consuming and feeding to my family safe?
Justine: This is Nate Bernitz. He works at the University of NH Cooperative Extension. And he pointed out that many of us bring a lot of scrutiny to the produce at the grocery store. Like checking the country of origin, or if vegetables are organic. He thinks we should bring that same scrutiny to the soil in the backyard.
Nate Bernitz: There's kind of a thought that food is safer when you when you grow it yourself, which may or may not be true.
Nate recommended getting the soil tested.
There are a bunch of different companies who do this in New Hampshire, but I went with Nate’s outfit – the UNH Cooperative Extension. And by the way, cooperative extensions: I feel like they could be an entire episode of their own.
These are programs which exist in all fifty states. They were originally organized by the USDA with the purpose of getting regular people access to expertise on farming. This was part of the American quote unquote “agricultural revolution,” when farm productivity dramatically increased in this country.
MUX FADE
So, whole other episode, I digress.
One of the things a cooperative extension typically offers is soil testing.
Nate Bernitz: Doing a soil test is very easy and doesn't require any sort of technical expertise, at least for the person submitting the test.
You can test for a lot of different things in the soil. For Maureen, Nate recommended a couple things. Their basic home grounds and garden package, which includes factors like pH and organic matter. And those are actually really important and I’ll talk more about them in a bit. But he also said: yeah, definitely test for heavy metals.
Nate Bernitz: Arsenic, selenium, chromium and mercury.
MUX IN: Creepy Crawly, Arthur Benson
The term “heavy metal” is kind of a loose one, but generally, heavy metals are a class of elements which are toxic even in tiny amounts. Exposure can cause cancer, organ failure, or impact brain development. Some ARE necessary for us as trace elements , like copper, zinc, and iron, and they do occur naturally in the environment – including in coal. But when they’re present at elevated levels, it’s often a result of contamination… like, they’re present in high concentrations in coal ash.
Heavy metals are also dangerous because they bioaccumulate – It’s why we get warned about the risks of eating fish that are higher up in the food chain, like tuna and swordfish. Once they’re in your body, they can be there for a long time.
The most common urban contaminant is a heavy metal. Lead.
Nate Bernitz: Of course, lead is always something that should be tested for for any home that essentially wasn't built recently was was built before lead was banned in New Hampshire in the country.
Like Maureen’s house, which is over a century old – lead paint was only banned in new construction in 1978.
And paint isn’t the only source to consider.
For decades, lead was added to gasoline to improve engine performance, and churned into the air pretty much everywhere… shocker, that was quite bad.
But leaded gasoline wasn’t fully banned in the US until 1996.
And then there’s the last industrial coal plant in New England, which still gets fired up, just seven miles south of Concord. Those emissions aren’t doing anyone any favors, and remember, coal ash also contains heavy metals like lead.
MUX OUT
All this to say, regardless of those chunks of coal Maureen kept finding, it’d be good to know what exactly is going on in the soil.
So, after talking to Nate, I went back to Maureen’s house to collect soil samples.
Justine: So the methodology is you dig down six inches deep, and take samples from, like, 3-5 spots. And so I talked to the soil testing people and – are you ready to hear something? He was like: I would definitely get your soil tested. He was like I would do the heavy metals testing, like for arsenic and mercury.
Maureen: (gasps)
Justine: Because apparently that’s associated with coal ash. I’m sorry to tell you this!
Maureen: Oh no.
Justine: But we’ll see. We’re gonna do a whole suite. And then you’ll know exactly what it is.
MUX IN: Nul Tiel Records, Reverie
Justine: Do you regret asking this question?
Maureen: No, I don’t! I’m glad to know. Oy. Let me know what you find!
MUX SWELL
Maureen said something else which stuck with me. She said she felt this shame because she hadn’t tested her soil sooner.
I’m a gardener too. I grow a lot of herbs and a few vegetables. And I actually live just a few blocks from Maureen’s house, in the same historic city. And I’ve also suspected for a while that I should get my soil tested too, but every year… I just… don’t do it.
There’s something about taking a bit of effort to figure out even how to do it, and the fact that it costs a bit of money.
But honestly, more than any of that, it’s this cognitive dissonance. It’s “an ignorance is bliss” situation. A fear that, as soon as I find out what’s in the soil, especially if it’s something scary… what if I have to stop gardening? What if I find out that I’ve been eating tomatoes laced with mercury fo r years? There’s nothing I can do about that now anyway.
I wanted to know – but I was also afraid to know. And as the summers went by, I felt shame. It was preferable not to think about what could be in my soil, and the path-of-least-resistance is avoidance.
Mux fade
But Maureen inspired me. So, I grabbed a trowel and collected the samples - in her garden, and in mine too.
Frankly, it was pretty easy. It took maybe 10 minutes. The Cooperative Extension explains how, right on the form. You dig up a few spots in the garden, take samples from around 6 inches deep, mix ‘em together, pick out the roots and rocks, let it air dry.
Then, you put one cup of your soil in a labeled ziplock bag, and mail it to the lab with a check.
Speaking of the check – the basic test starts at $20 bucks. But I wanted to see about heavy metals too, including a couple which required special processing and extra fees. All told, it was around $150, which seems comparable to other states. And then we waited. Apparently there’s always a bit of a backlog in spring, when everyone’s thinking about gardening again.
But after about a month, I got an email with the results.
Those results… after the break.
MUX IN: Nul Tiel Records, Little World
Nate: We’re gonna hear the results right after the break.
But first – we’re loving your responses to our episode on lawns, which we released last week as the first installment in our summer yardwork series.
Harold wrote in. He grew up in upstate New York with FOUR ACRES of lawn. Apparently this was a “bear” to manage, especially during mud season in spring. Looking back, Harold wishes they’d planted willow or other riparian vegetation in some particularly wet spots. That would have been better than mud, he said, and carbon storage too.
We also heard from Jen. She and her husband live in Portland, Oregon. They took out both their front and back lawns, and they installed raised beds and a beneficial insect + herb garden.
We really love hearing from you and we do tend to share your responses, sometimes here, sometimes in our newsletter – which is free and comes every two weeks. Our email is outsidein@nhpr.org.
Alright, we’ll be right back.
/// BREAK ///
Justine: Welcome back to Outside/In. At first glance, the soil test results were… confusing.
MUX IN: Alexandra Woodward, Backbeat Planet
It was a lab report. And we’d tested Maureen’s garden soil for over a dozen variables. The basics: pH and organic matter, nitrogen, phosphorus, potassium. All important for crop productivity. The heavy metals: cadmium, copper, nickel, chromium, zinc, lead – plus an extra test for mercury and arsenic.
And I am not going to list all of these results because numbers are famously difficult to follow in audio form. We’ll post more details on our website.
But there are two results I want to focus on here. The first one: is lead.
Which is very toxic. People have been aware of for literal millenia. It’s banned from paint, it’s banned from pipes, it is a POISON that impedes development of the human brain, especially in kids.
And in Maureen’s soil, the test results said lead was present at 453 ppm.
Which… at first, was meaningless to me. Even with the added noted from the lab informing me that this is a “medium” level.
Because, again, heavy metals do occur naturally in soils that haven't been industrially contaminated.
How bad is 453 ppm?
MUX SWELL AND FADE
My own soil, by the way, was almost the same – actually, just a little even higher. I found out that’s ABOVE the background level in local soils… it’s ABOVE the acceptable level for a “child’s play area.” But it’s below the general threshold for a residential property.
But what about for vegetable gardens?
I found a guide to lead in soil, published by the Environmental Protection Agency, the EPA… which included a visual spectrum: a colored line, on end, green - safe - when lead is present in low concentrations. In the middle, yellow, for caution. On the far end - red, danger. And 453 ppm is right at the spot where the green is turning to yellow. Right between safety and caution.
I’d really WANTED a straightforward NUMBER. Below X concentration, you’re good to plant a garden – above it, it’s dangerous.
But I could not find such a thing – and I was like, either I’m a terrible reporter… or this doesn’t exist.
Ganga Hettiarachchi: It doesn't exist [laughs] That doesn't.
So, this is Ganga Hettiarachchi. She’s a professor of soil and environmental chemistry at Kansas State University.
Ganga Hettiarachchi: Most people want, and I know most researchers want, to come up with these numbers as well. But at the same time, I am I have some concerns about that, too.
One of Ganga’s concerns is: what if an agency comes up with levels that are unrealistically LOW?
Ganga Hettiarachchi: Keeping gardeners away from gardening.
Ganga has actually worked with communities to safely START GARDENS on contaminated sites - brownfields.
Ganga Hettiarachchi: Because when it comes to any of these soil contaminants, what is important is their bioavailability, not their total concentration in soil.
MUX IN: Ice Fields, Martin Gauffin
What’s important is the bioavailability of these contaminants.
This is relevant when it comes to nutrients and the human body, too. We need to cook and process certain foods to better access nutrients, or sometimes to digest them at all.
Take tomatoes.
SFX tomato slicing
They contain a compound called lycopene – it’s an antioxidant, it’s super good for you.
SFX oil sizzling
And some scientists have found that when tomatoes are cooked with olive oil, which perhaps not coincidentally is delicious, lycopene absorption goes up.
It’s chemistry. And it’s the same principle when it comes to soil and plants.
Plants have the ability to absorb, or “uptake” elements through their roots. And that uptake changes d pending on the conditions of the soil.
SFX + MUX SWELL AND OUT
Which brings me to the second result I want to look at more closely. Soil pH.
pH is the measure of how acidic or alkaline a solution is, and it was included in that basic $20 test.
And pH really matters… truly for anything that happens in soil. Ganga called it one of the “master variables” at play here, because pH is a deciding factor as for what chemical reactions are even possible.
So, when we’re growing vegetables, we are hoping for conditions in which lead will NOT be bioavailable to plants. So, ideally, we want pH to be near neutral – maybe just a little acidic.
Soil pH isn’t the only important factor determining lead bioavailability. Another is organic matter, which is all the detritus from the once-living-stuff, like leaves and insects and twigs.
The more organic matter, the better heavy metals bind to the soil, which is what we want: because the metal stays in the soil and doesn’t wind up in the plant tissue. And it can also dilute the heavy metal concentration.
MUX IN: Bundt, Blue Dot Sessions
So, what does all this mean for lead? Again Maureen’s soil tested for lead at 453 ppm. The lab results said this is a “medium” level. Now, the CDC says: there is no safe level of lead exposure for human beings, especially kids. Which makes it sounds like the limit for lead in garden soil should be zero, and absolutely not 453 ppm.
So, that doesn’t sound good. But the presence of lead is not the same as exposure to lead.
This is why bioavailability is so significant. Is the lead in a form in which plants can actually absorb it? Ganga says: if you pay attention to pH and a couple other factors:
Ganga Hettiarachchi: Most of the time the lead uptake by plants is going to be pretty insignificant, in most soils.
Justine: Great news. And in Maureen’s soil, the pH was more or less where it should be – just a touch on the acidic side. So, the vegetables growing in her soil probably won’t absorb much of that lead… with a couple exceptions.
Ganga Hettiarachchi: Except root crops… like carrots, radishes, turnip...
So, the type of plant matters too. Above-ground fruiting crops, like tomatoes, are better in this situation.
And while Ganga wasn’t too concerned about plant uptake, she was more concerned about something else.
Ganga Hettiarachchi: The major pathways of most of these soil contaminants is direct ingestion.
Justine: Direct ingestion: eating the soil. Which with adults is typically an accident, but which can easily happen… like when rain splashes dirt onto leafy greens, and you don’t wash them well enough, or if you breathe it in when it’s windy. But there are people who deliberately eat dirt, and who are also especially vulnerable to heavy metal exposure: kids.
Ganga: When it comes to children, since they are more vulnerable, we have to minimize every possible pathway, so that we should co nsider any pathway. like even touching.
Luckily, there’s a relatively simple answer to that one – wash your veggies, and don’t leave bare dirt exposed. Cover it up with mulch.
MUX OUT
So, as for Maureen’s question: is she poisoning herself and her family… based on the science we have right now, probably not.
MUX IN
Justine Paradis: So I have some answers for you, from the soil testing a little while ago. You ready?
Maureen McMurray: Eee. I am ready. And I have, I actually just picked some peas… Maybe after we can go through it after, what I decided to grow.
Justine: Again, based on these results, I think that Maureen can keep gardening there, but there are some steps that she can take to manage risk. And a lot of these principles can be applied to other gardens too.
1) Mulch! Which Maureen has actually already done.
Maureen: The beds that I use are covered with mulch and compost
She can keep the ground covered with wood chips, which removes the possibility of the soil getting kicked up by the wind and inadvertently breathing it in, and it mitigates the possibility of her kid playing with and maybe eating the dirt.
2) She could install raised beds, and lift the plants out of that soil. Nate Bernitz from the cooperative extension recommended 12” deep.
Maureen: Okay, cool.
3) Crop selection: she should avoid root vegetables and go for more fruiting crops like tomatoes.
Maureen: Okay. Oh! I didn’t do root crops.
Justine: oh, fabulous!
Maureen: I’ve only planted them once and they didn’t do well.
As far as leafy greens, expert advice varies. After root vegetables, they’re the next riskiest. Some say don’t plant it at all when lead is elevated like this, others say: if you do, wash it really well.
Maureen: Lettuce… chipmunk ate it. So. But I would have washed it anyway. Alright!
4) She could amend her soil. And there are a lot of ways she could go with this. Adding phosphorus could help, as could adding compost. And – there’s that master variable: pH.
Maureen: And can you change the pH?
Justine: Yes.
Maureen: Okay, how? [laughs]
Justine: No, you add lime! That’s one way. Yeah.
Maureen: oh!
But there are trade-offs here – because lead isn’t the ONLY heavy metal to think about. But these are questions of soil chemistry. And if you want to understand your soil, you don’t have to figure this out alone. If you decide to get your soil tested through your state’s cooperative extension, typically they’ll help you interpret your results and share recommendations for your garden.
Maureen: that is so cool. And I wish I had done that a long time ago. Just right in our backyard. That’s amazing.
Justine: how are you feeling after all this?
Maureen: Empowered!
Mux in
It’s not only the information. It’s that you can call in for help and guidance. I feel empowered, excited, and relieved.
–
CREDITS
Nate Hegyi: Part II of Yardwork was produced and reported by Justine Paradis. Special thanks to Jim Garvin, Tom LeMien, and Anna Paltseva
We tested Maureen’s soil with the UNH Cooperative Extension, but you do not have to live in New Hampshire to do the same thing.
We will put a link to find your local cooperative extension in the show notes, plus a couple other resources on soil lead.
And, if you decide to test your soil, we’d really like to hear about it. Tell us about your garden – what you’re growing and where, and what you learned by testing the soil.
Again, we love hearing from you. And, we usually share a handful of responses in our newsletter, which is really fun and comes every two weeks.
You can get in touch by sending us an email – as always our address is outsidein@nhpr.org.
And you can sign up for the newsletter on our website – that’s outsideinradio.org.
This was part II of Yardwork, our summer yard and garden miniseries. Next week is the third and last installment – can a community garden… survive gentrification?
So he started an online smear campaign about the Berkeley Garden. It was anti-Chinese. I mean, it was anti-immigrant.
This episode was edited by Taylor Quimby with help from Felix Poon, Jessica Hunt, and me, Nate Hegyi.
Rebecca Lavoie is our executive producer.
Music in this episode was by Walt Adams, Nul Tiel Records, Alexandra Woodward, Martin Gauffin, Blue Dot Sessions, and Arthur Benson.
Outside/In is a production of New Hampshire Public Radio.