Urban Agriculture Webinar - The State of Scientific Knowledge and Research Needs Transcript
STEPHANIE CWIK: Hi, everybody. Thanks for joining us today for the first of our special Webinar series on Brownfields and Urban Ag Reuse. This Webinar will present the state of scientific knowledge and research teams, a snapshot of the state of science regarding creating urban ag projects on Brownfields sites.
So, a couple of administrative things to start. This Webinar is being recorded and we'll post it in a few days to the new Brownfields website at www.epa.gov/brownfields/urbanag. Please note that we're taking typed questions via the Webinar service only to reduce any accidental noise on the line. Everyone is muted except for our speakers. We plan to take one or two questions between each speaker with time for more lengthy Q&A at the end. So send your questions via the question box in the "Go To Webinar" dock at the right of your screen.
We expect our Webinar to take two hours, and then at the conclusion you'll be asked to provide some feedback, so please complete this form so that we may continue to improve our offerings in the future.
JIM VAN DER KLOOT: And the speaker you just heard was Stephanie Cwik who is the organizer of this Webinar. My name is Jim Van Der Kloot with EPA in Region 5. We're excited by the tremendous proliferation of new community gardens and urban ag projects. We've toured a number of projects over the last year, and have been struck by the creativity and by the wide range of approaches to gardening.
At the same time, we're hearing a lot of questions being raised about the potential for exposure to contaminated urban soils, and contamination of food. This Webinar is our first attempt at assessing the state of knowledge on this subject. We feel that this is the key gap in public policy right now and in knowledge, and we would like to help in the future by identifying and filling gaps in policy and knowledge. This Webinar is an early step in that process, and will give an overview of the current state of knowledge.
STEPHANIE CWIK: Thanks, Jim. So, as we mentioned before, the goal of this Webinar is not to present all of the answers to all of the questions regarding urban agriculture projects of Brownfields sites. Depending on who you ask, we have quite a way to go before we know everything. Rather we're presenting a brief snapshot of the information that we do know, so that folks can continue to get the work that they have begun in the safest way possible.
So by now you've noticed the outline of the presentations we've got lined up today, and we'll waste no more time with introductions. Let's get started with our first presentation on assessing the hazards at the Cleveland case study -- Karla, Lilah, and Dave. Let's bring up Karla.
KARLA AUKER: Its -- Lilah's first.
STEPHANIE CWIK: Oh, Lilah's first. Sorry.
LILAH ZAUTNER: Hello, everyone.
STEPHANIE CWIK: Go ahead, Lilah.
LILAH ZAUTNER: Thank you. And thank you for inviting us to take part in this Webinar today. So I'll just jump right in to set up the Cleveland case study. My name is Lilah Zautner. I'm in Cleveland, Ohio, and I am the sustainability manager for a large non-profit development company called Neighborhood Progress. We are in the midst of re-imagining a more sustainable Cleveland. I will talk briefly and then turn it over to Karla with the EPA.
So, re-imagining Cleveland started off several years ago, much like many mid-western cities, and actually cities across the U.S. We have major issues with vacant land, which is both a challenge and an opportunity. We have over 3,000 acres of vacant land in the City of Cleveland, and we also have growing energy around the local food movement, as well as sustainable land reuse.
Recognizing the challenge, and also recognizing our opportunities, we launched in 2008 a study that was funded by the Surdna Foundation to look at where our vacant land is, and then furthermore, looking at where our vacant land is in relation to social and biophysical characteristics. So using GIS and stakeholder engagement, we looked at vacant land, then we layered on top of it things such as our combined sewer overflows, our tree canopy, our pervious surfaces, and then furthermore, layered on top of those the social factors, such as areas where development was likely -- our food deserts where access to nutritious food is an issue.
From that, we put all those layers on top of each other to understand where our assets are, where weaknesses are, and then furthermore, to be able to see kind of from a 35,000 mile view, to look at where are the most logical places to put different vacant land reuse strategies into play. The strategies that we're talking about are urban agriculture, of course. And then on the other side some greening projects such as pocket parks, native plantings, storm water controls and so forth.
So, after the study this last year, we jumped into the pilot projects. This is where we really looked at how can we further this movement around vacant land reuse. Currently, we have 56 pilot projects, take up about 15 acres in the 130 or so residential vacant lots. Thirty-one of those projects are urban agriculture projects. So those are gardens, urban farms, vineyards and orchards. This is on top of our existing 230 plus community and market gardens in the City of Cleveland.
We recognize that these pilot projects are really just one piece of the solution. We have a 3,300 acre problem. Fifteen acres is a drop in the bucket and it's not going to solve the problem. The bigger picture we see is many actions by many people over the next 20 years. And the study and pilot projects were just kind of a boost -- something to push forward an agenda that will be in place for the next, like I said, for the next 20 plus years.
Understanding that we are building a movement, this takes a lot. In order to build a movement, we recognize that we have to reduce the barriers that stand in people's way, and also to create policy that empower people to exert their own personal responsibility and stewardship. One of those hard issues that we've tackled, or that we're attempting to tackle, is urban soils. For the urban people out there, I'm sure you understand what comes with the term urban soils.
With that, we decided we really needed to understand our soils. We have great resources here with the Ohio State Extension, which has been very helpful in helping our local food movement thus far. But what we started to see is maybe it's not just an issue of lead, and we started to see this with the pilot project. At this point, we partnered with the USEPA to get a better understanding of what kind of contaminants exist in our urban setting. And what do we need to focus on, aside from lead, but are there other risks and so forth.
I'm going to turn it over briefly to Karla who will talk about the testing that the EPA did on our re-imagining sites. But what we've learned thus far through re-imagining, the pilot projects and then our partnership with the EPA, that there really are a range of contaminants of concern in Cleveland, and most likely, in older industrial cities. That's it not just an issue of lead or 400 parts per billion.
We've also learned that our sector, which is the sector around non-profit urban re-development, or green space creation, or even local food, doesn't really -- as we stand now, don't have the capacity to analyze the soil data. We need to add capacity to our systems, be able to analyze, to advise grassroots, Mr. and Mrs. Smith, urban farmers, and make decisions about soil contamination. And with that, we've recognized that there really is a need for protocols in risk assessment standards for urban agriculture that can be fed into sectors like ours, and easily interpreted for the people actually on the ground doing these projects. They're, in essence, building the movement forward.
So we're very happy to hear that the EPA has taken up this huge beast and we're looking forward to how they can help the people on the ground doing this work in urban areas throughout the country.
So, with that I'll turn it over to Karla Auker with the EPA and she'll talk about the testing that the EPA has done in partnership with Neighborhood Progress. Thank you.
KARLA AUKER: Thank you, Lilah. Can everyone hear me OK?
STEPHANIE CWIK: Yes.
KARLA AUKER: As Lilah mentioned, NPI realized that the potential existed for there to be contamination other than--
STEPHANIE CWIK: Karla, you are a little bit far from your microphone there, and we don't see your slides yet.
KARLA AUKER: Do you see them now?
STEPHANIE CWIK: No. Barely. We see "do not."
JIM VAN DER KLOOT: Do not mow.
STEPHANIE CWIK: Do not mow.
KARLA AUKER: Do not mow -- that's part of that.
STEPHANIE CWIK: OK.
KARLA AUKER: As Lilah mentioned, NPI realized that the potential existed for there to be contamination other than just lead on the properties that were proposed for funding through the Neighborhood Projects Stabilization Grant. With that in mind, NPI asked USEPA to help them with the sampling of the properties for a range of contaminants. The USEPA saw this not only as a way to ensure the safety of the NPI grantees, but also as an opportunity to begin to develop a database that could be found -- a database of what contaminants could be found on vacant residential land in big cities.
USEPA's hope was, and still is, that the data from this NPI project will be used to develop a reference document that can be used by cities and private individuals to determine exactly how much and what kind of sampling they need to do to ensure the safety of the people gardening on the site. USEPA realizes that it's impractical and cost prohibitive to sample every urban agriculture lot for the full suite of contaminants. With that, I'd like to go through what we did when we worked with NPI, and just in general, what kinds of contaminants that we found.
What we did initially when NPI contacted us is we just sampled a subset of the sites that had been chosen to do the urban agricultural projects on. And the sites that we looked at, we reviewed the applications that NPI received and we prioritized those sites. And we prioritized them based upon mostly whether children would be exposed to the contaminants in the soil.
We weren't overly concerned about the intake of plants and vegetables that they were going to uptake the contaminants that were in the soil. What we were mostly interested in is the contaminants that would be in the soil and could be ingested by the children, and then also by the other workers at the site. Once we looked at each of the sites, and set up kind of a priority list for ourselves, we went out and we visited each of the sites, and we looked for what I call red flags.
We looked at the land use around each site -- was it all residential, were there old factories right next to the properties where the community gardens or market gardens were proposed. Were there any waste piles on the site that might give us a heads-up as to what contaminants we should be sampling for. Then we also went back and we reviewed historical data. We looked at Sanborn maps, fire insurance maps, that showed previous land use around the properties. And we also looked at old aerial photos.
When we sampled the sites, we biased our sampling. Because, like I said, one of the goals of USEPA sampling was to try to, to come up with kind of a short list of what communities should be sampling for on these urban garden sites, so that they wouldn't have to sample for everything under the sun, because it's infeasible -- it's just cost prohibitive.
So we sampled on all the sites, we sampled for metals, we sampled for polyaromatic hydrocarbons, which we refer to as PAHs. Those are the things that are found in asphalt, and also it's found when buildings burn down and you get the soot from the buildings and they get distributed on the soil.
We look for asbestos because we were concerned that there could be asbestos in the soils from asbestos piles in the houses when the houses were demolished, asbestos roofing, asbestos siding, pipe wrap -- all your normal things. And we also look for volatile organic compounds. Those are things that volatilize easily, things like dry cleaning fluid. If there was a dry cleaner, say, next to one of these properties, that could be an issue.
We also look for another volatile organic compound would be something like mineral spirits or turpentine. Then, when we did our site visit, we looked for sites that had full transformers either on the property or adjacent to the property that we were looking at. Any of them that had transformers on them, we also sampled for PCBs
What we found, in short, was we found a lot of metal, which we expected to find. Most of the metals that we found were lead and arsenic, lead being the most prevalent. When we looked at the results, we needed something to compare them to, to try to figure out what was safe and what was not safe, just to give us a basis. So we chose to look at Ohio Voluntary Action Program residential use standards. We call it the VAP. The VAP residential use standards are numbers that are used as clean-up numbers to allow a property to safely be reused for residential use.
Ohio EPA also has commercial industrial standards, and commercial industrial standards take into consideration that people don't actually live at the site. They may be at the site, say, eight hours a day, say, 48 weeks out of the year, when you take into consideration vacations and holidays. What we found is it 100% of the sites that we sampled exceeded Ohio Voluntary Action program residential land use standards.
But then we started thinking, well, is that really practical? Are people going to be doing what's the equivalent of living on these sites? So we thought, well, let's see whether the sites will exceed the Voluntary Action Program's commercial land use standards. And we found that 45% of the sites that we sampled still exceeded the VAP commercial industrial land use standards.
Then we continued to look a little bit deeper, and one of the things that we realized, and I think this is going to be a problem even on a national level, is that the arsenic standards for residential land use are greater than what the background concentrations are for arsenic in Ohio. And that's something that's going to have to be taken into consideration as we're giving the yea or nay on whether sites are safe to be used for urban gardening.
Once again, the purpose of this Webinar is not necessarily to present all the answers, but to say the state of where we're at, as far as urban land use and urban land reuse for urban gardens. This is one of the questions that we're going to have to wrestle with.
Another thing that we found on almost all of the sites was polyaromatic hydrocarbons, or the PAHs. If you remember, those are the compounds that are very, very prevalent in asphalt. Those are also compounds that are prevalent when there's a fire in the area and you get soot redistribution. We found that 75% of the sites, two-thirds of our sites exceeded the VAP residential land use standards or the PAHs. And 33% still exceeded them when we compared the concentrations to the commercial industrial land use standards. So that's going to be another thing that we're going to need to wrestle with. Maybe raised beds are the answer to this, maybe they're not. But it's something we're going to have to talk about.
Now one important thing that we found or didn't find, which I thought was interesting, and to really help us as we tried to make recommendations to help people focus the sampling, is that we found no asbestos on these properties where the houses had been demolished. We found no PCBs, however, I would still recommend that if you've got a transformer on a property that you want to use for urban gardening, that you still sample for PCBs. And we didn't find any VOCs. The VOCs are the volatile organic compounds, like I said, like mineral spirits, that kind of thing.
So, what I'd like to leave you with is where we're at from an EPA standpoint. And we're looking at the data we have, we're looking at potentially -- we're working with Ohio EPA to try to come up with a different, maybe different assumptions for risk assessments. We need to look at urban properties and try to figure out what is an appropriate risk assumption. Are people essentially living on these properties? Well, probably not. But are they on them more than you would be for a normal commercial industrial property. Yeah, they probably are.
So, I just want to kind of leave everyone with some food for thought regarding risk. So one of the questions we have is what risk scenario is appropriate for urban gardening? Residential? Commercial? Industrial? Or something in between? As I said, chances are it's going to be something in between, and we're in the process of evaluating that now. Should we use different risk assumptions for neighborhood community gardens versus market gardens?
The answer, off the top of my head at this point, is probably. You've got totally different scenarios when you have one single vacant property that's completely surrounded by residential land uses. Those kinds of situations, maybe we should look at those in more of a residential land use scenario, because the people are literally walking out of their houses over to the garden and walking straight back into their garden -- or back into their house tracking the dirt in. Versus market gardens where you've got more of a commercial industrial sort of scenario where there's limited access by people in the neighborhood. And you're going to have employees on the property, but are they going to be on there year round in the way that most commercial industrial scenarios are.
Then, also, another question is what if naturally occurring background concentrations of metal are higher than the risk-based standard. That's something that we need to wrestle with. It seems unreasonable to say, no you can't garden on this property because it doesn't meet the risk standards, when you go a property next door or a property out in the country and you have arsenic concentrations that are just as high or similar to what you have on the urban garden that you're not allowed -- or property that you're not allowing people to use for an urban garden.
That's one of the things that's going to be addressed later on in this presentation by one of the other presenters is what about soil amendments? There are soil amendments available that can make these contaminants less bioavailable. So maybe 400 or 600 or 800 parts per million lead isn't the same across the board, depending on the pH of your soil, and what the other chemical make-up of the soil is. And a question, too, are raised beds the answer. Some people say yeah. But one of the things you need to think about is where's the soil coming from that you're using for those raised beds? Should there be standards for raised bed construction? Should the soil be tested before it's used?
With that, I'd like to turn the presentation over to Dave Behringer. He's going to address some of the more general and far-reaching methods for sampling, and what contaminants need to be sampled for.
STEPHANIE CWIK: Go ahead, Dave.
DAVE BEHRINGER: All right. Am I loaded up here?
STEPHANIE CWIK: No.
DAVE BEHRINGER: How about now?
STEPHANIE CWIK: Yup, there you go. We see your whole screen there. There you go, it looks good.
DAVE BEHRINGER: That's good.
All right. My name is Dave Behringer. I'm with Behr Geo Environmental. And I've been happy to be able to help and work with NPI on some of the sites that Karla was just talking about. But today I'm going to be talking about chemicals of concern and sampling considerations at urban gardens in sort of a general way.
The primary chemicals of concern at urban gardens, as Karla mentioned, and what she found in Cleveland, and this applies pretty much anywhere, are the metals lead and arsenic, and you've got the polynuclear aromatic hydrocarbons, the PAHs or PNAs. These compounds have several different names, but they're all the same and they always seem to be present. They're the primary contaminants of concern because they can be present on just about any site in the urban setting because of how they were deposited. Typically they ended up on the sites by airborne deposition.
Whereas the secondary contaminants of concern, the VOCs, PCBs, other metals besides lead and arsenic, like mercury, cadmium, chromium, you've got your herbicides, pesticides, dioxins. And then some of the other semi-volatile organic compounds. These are all site-specific, meaning that it depended how the site was used in the past whether or not these would be present. For example, was there a dry cleaner on the site? If there was a dry cleaner on the site, then there's a good chance you might have some VOCs.
But moving forward, what do you look for? You know what all the contaminants could be -- I mean just about anything could be there. How do you know what to look for? Well, pretty much almost always you're going to be looking for lead. But that's not the only thing. Other contaminants of concern, in order to determine the other contaminants of concern, you've got to consider the site history. And typically that's determined through, or can be determined through a phase one environmental site assessment, which is probably the most thorough way.
But again, it's not the only way. You can look at just some of the basic historic information -- the Sanborn maps, old aerial photograph, things like that. I mean you don't have to go through a full-blown phase one environmental side effect.
Planned use is another thing you've got to consider in determining what you need to look for. Are you going to be looking at surface planting? Or are you going to be planting right in the soil at the site as it is, as it exists? Are you using raised beds with imported soil? Are you going to be putting an orchard on the site, or is there going to be a greenhouse? A greenhouse, just as an example, if you had a dry cleaner on the site -- I'm going to keep going back to that because I think this was a VOCs associated with dry cleaner.
If you had a dry cleaner on the site, you could have VOCs coming up into and concentrating in the air inside the greenhouse. That would be certainly an issue you'd want to look at. But if you were going to be doing surface planting at the site, well maybe the VOCs wouldn't be such a big deal. Because if they did make it up to the surface, they'd probably volatilize into the air and be diluted. And really wouldn't pose that much of a concern. So those are the kinds of things you want to look at. Who's going to be exposed? Is it going to be a community garden where children might be present? Or is it going to be a commercial garden?
I think the one thing that I want to stress is that no one strategy fits every single site. It's not a one size fits all scenario here.
Now, the sampling strategy that you're going to want to look at, there are a couple questions you have to ask. Do you want to pane discreet samples or composite samples? And what I mean by that is do you want to obtain individual samples where you have each sample, or do you want to do composite samples where you take a whole bunch of samples, you combine them, and then in theory get an average result for that sample? How deep are the sample?
Typically, you're looking fairly shallow, if you're looking at a garden scenario.
A number of samples, and these questions really depend on -- I find that the number one thing that it depends on are the budgetary constraints. Money controls everything. If you've got unlimited funds, then you have a lot of samples. But that's not normally the situation. Normally there's enough money to collect maybe three or four or five or so samples, and that's all you can afford so that's what you do. You've got to work with it.
The size of the site plays a big role. If you've got a big site, you definitely need more samples in order to make a determination on whether it's safe or not. The expected contaminant distribution, the chemicals of concern, the size of the site. Again -- oops, I've got that on there twice. And then also, personal preference. Everybody has their own way of going about things and that plays as role.
And be prepared for surprises. You're going to find basements that are filled with garbage, a lot of times they just collapse the old houses or old buildings into the basement, and that's what you have. You're going to have buried foundations on almost all these properties. You're going to find unexpected contaminants and contaminant distribution patterns. And even on residential sites you're going to find underground storage tanks. This picture is an example of a tank that was found very recently on a residential site. It was just doing some poking around on the site and helping to clean it up and there wasn't supposed to be any tank out there, but sure enough, there it was.
Now, just an example case study to kind of highlight some of these issues. So, this was in the City of Cleveland. It was a formerly vacant residential property, and it had an adjacent commercial and light industrial nearby. There was a dry cleaner across the street, an auto repair shop adjacent, a bakery adjacent. The proposed use of those properties was an educational garden for urban teens and, of course, the budget was tight -- it always is.
The sampling strategy started with composite sampling. This was a multi-incremental composite sampling, which means you take a lot of samples and combine them, and you go through a real process of making sure that the sample is uniform. So it really does produce a very uniform average concentration for the property. And we use that for testing for metals -- PAHs, PCBs, herbicides and pesticides, and we did some discreet sampling to test for VOCs. Now, you may look at this and say if money was so tight then why did you test for metals -- PAHs, PCB, all these different things. Well, because there were teens going to be on the site and young kids, and because attorneys got involved, that's how we ended up testing for all those different things.
Now, findings at this site was, well, we had elevated lead and arsenic. One of the composite samples -- the other composite sample came back relatively clean. Now that doesn't mean that there were no isolated areas of elevated lead or arsenic on the site, just in that area where that composite sample was taken. It just means that on average it was relatively clean. So, we were in good shape there. But on the area where it was elevated, what we did is we went back and we re-sampled for lead. And I'll talk about arsenic, why we didn't touch that in just a second.
But we re-sampled for lead with discreet samples to see if we could isolate some hot spots. We did isolate some hot spots, some areas where the lead was higher than others, where that was driving the overall average concentration to be higher. And we went ahead and removed those areas. The garden has been developed and it's planted and it's thriving today.
Now the arsenic wasn't addressed, going back to that, because the arsenic, although it was above the Ohio Residential Standard, the VAP standard, it was not above what's normally considered safe -- not safe, but background concentrations in Ohio. It was below the normal background concentrations or what you might expect to find in the Ohio soils. So we essentially dismissed the arsenic concentrations as not being elevated, they were just normal background.
So, in summary, the sampling strategy should be tailored to the specific needs and site history, and the composed use of each site. I do not recommend policy of one size fits all, unless you just have a whole lot of money that you want to throw at a site. I've seen that once or twice, but not very often. Most of the time that's not the case. You really have to be extraordinarily realistic going into the process. You have to expect surprises. You're going to find things that you didn't expect. In some cases, you just may need to walk away from an unsuitable property and you have to not continue pushing forward with properties that may not be suitable, at least in current conditions.
That's it for me.
STEPHANIE CWIK: Thanks, Dave. We have had a couple of questions for Dave, Karla, and Lilah. Can anyone discuss the order of magnitude for sampling cost?
DAVE BEHRINGER: Sure, I can talk about that a little bit.
The order of magnitude is it depends on how much sampling is actually completed. It can range from a couple thousand dollars typically, up to on sites where there's Brownfields grants and there's a lot of money thrown into it, you could be looking at several tens of thousands, maybe up to $50,000. Now, that doesn't make a garden site very profitable though, if you're doing that--
STEPHANIE CWIK: Sorry, was that per sample?
DAVE BEHRINGER: No.
STEPHANIE CWIK: Or like how many samples would that be?
DAVE BEHRINGER: Oh, that would be hundreds of samples on a site, if you were going to run that high. But on a typical site where you have six or seven samples, you're probably looking at somewhere around $1,000 ballpark. If you have a consultant involved, then you're going to have their time involved. But the actual analytical costs are probably, for six or seven samples, you're going to be looking at around $1,000, in that ballpark.
STEPHANIE CWIK: Great. And then one more. Can anyone tell us what a background arsenic concentration would be for Ohio or for the Cleveland area?
DAVE BEHRINGER: It's about 20 parts per million is what's considered -- anything below that is generally considered normal background.
STEPHANIE CWIK: Great. And just to let everybody know, we will be taking more questions at the end of all of our Webinars -- or all of our presentations. And with that, let's kick it up to Nick Basta from the Ohio State University who will present urban soil contaminant assessment -- important human exposure pathways. Nick?
NICK BASTA: I'm here. Stephanie, can you see my presentation yet?
STEPHANIE CWIK: Nope.
NICK BASTA: OK. How about now?
STEPHANIE CWIK: Nope.
NICK BASTA: Really?
STEPHANIE CWIK: Yeah, we got it.
NICK BASTA: OK.
STEPHANIE CWIK: Take it away.
NICK BASTA: All right. Well, thanks for Region 5 for inviting me to give a presentation. I want to focus on a few more exposure pathways, mainly the soil levels that we've been talking about with contaminant assessment. I'll give you a little background into who I am and what I do. I am a soil chemist that works mainly on environmental chemistry issues, and we do routinely evaluation of contaminants in soil, interpretation, and then also remediation strategies and technologies and evaluation of them. So, this is a topic that is really right up our alley.
I mean this is a nationwide issue, vacant lands, urban soils. The picture here shows a couple of homes. Pretty soon that's going to be gone, the homes be gone, and we'll be looking at sites like the next picture shows. The top site there, it is actually two pictures, had seven homes on them and now they're all gone. The bottom one actually had one. So the question then becomes well, what can we do with this land and can this land actually be used for gardening, specifically going to be used for food production? Is there contamination there? And if there is, does it present unacceptable risk.
So this is the kind of thing. You walk onto a site, there used to be homes there, the homes are gone and you're trying to figure out how this land can be used. This is a daunting task. If you actually do a more comprehensive approach, which is usually done in Superfund areas, you try to evaluate many pathways and many scenarios and many receptors and many contaminants, which means mucho dollars, and many years. Honestly, these sites are going to be a lot easier than that. But we're going to have to look and see what are the possible contaminants of concern. What could have been in those urban areas and residential areas? You probably narrow it down to what can be commonly found for organic contaminants.
Oil is a common contaminant, PAH is a common contaminant. Then earlier the more site-specific things, whether there's transformers and PCB and et cetera. But the commonly found ones are oil and PAH. Metals and trace elements, the more common ones you run into are lead, maybe chromium, sometimes, but more rarely, arsenic and cadmium. So it's not everything, and it's not usually every pathway. It's not as big as some of these more heavily contaminated Superfund sites. We're looking at urban soils that might have a few issues.
When you look at water or soil assessment, I always like to think of it this way. Suppose you start out with a pristine soil -- no contamination at all. Background levels of contaminants or background levels of metals, background levels of organics. Pure, pristine soil. Then you add some contaminant, you add some lead to it, you add some oil to it -- you basically contaminate the soil. You could contaminate a soil a little and not have adverse health effects.
In other words, you could elevate the level of lead in the soil, and you're not at adverse health effects. But if you keep contaminating it, adding more and more contamination, you get to a point where it's excessive, then you have a problem. You could actually start experiencing adverse health effects. We were trying to come up, when we were evaluating these lands, we should actually try to come up with standards that prevent the adverse effects.
Presenting contamination, absolute contamination, would be nice, but it's not going to be possible in many cases. That ship as sailed. Many of these urban areas already are above natural background levels of pristine soils. So we really should be focusing, not whether it's above background, but whether it's at a level that causes unacceptable risk.
First I want to talk a little bit about background, natural soil backgrounds. First of all, soil has all 92 naturally occurring elements of the periodic table in it. Not only soil, but water, and you and me -- biological tissue, bone, hair, et cetera. There's been some good national databases, there's also some data that we're working with in Ohio that's pretty good on background soils. But just know that the table in the right here shows a variety of elements, that there's no such thing as zero. There's always going to be some natural background in soil. Not only in soil but in you.
For example, the background level of gold in soil is 0.06 to 20 part per billion. Your hair probably contains between 5 and 10 parts per trillion. So yeah, we don't even have zero gold in soil, although we don't usually worry about gold contamination. But anyway, just know that all these elements are in soil. So you're starting with something.
A lot of these are actually heavy metals and trace elements that are naturally occurring -- heavy metals being really dense metals, and trace elements being they're in low concentrations. But when you look at heavy metals and trace elements, that's most of the periodic table. So most of the periodic table elements already have natural abundance in your soil. We don't usually focus on the whole periodic table when we're worried about risk. We usually focus on the ones that cause health issues that are commonly occurring, and they're the usual suspects, like cadmium, lead, mercury, arsenic, molybdenum. So it becomes a shorter list of elements, all of which have natural occurrence.
It's good to have natural occurrence because, actually, plants and animals need small amounts of these elements, and it's good that they're naturally occurring -- molybdenum, iron, manganese, copper, zinc -- are all required for plant growth and for animals, all the above, nickel and chromium. The problem is if you have excessive amounts, which, again, means too high of a concentration. You get into problems. Background levels are not an issue; high levels that can cause adverse effects are. And I've got a picture of vitamins. If you take vitamins in the morning, you've taken your share of heavy metals and trace elements this morning.
Polyaromatic hydrocarbons occur in all soils. All soils have PAHs. PAHs, the smallest one is naphthalene, two rings -- you have to have more than one ring. There's a range of different PAHs, depending on how many rings in the structure. The one that usually gets focused on is benzopyrene because it's a potent carcinogen, BaP.
So, when people look at PAHs in soil, they usually want to know not that there is PAH, but how much benzopyrene or other carcinogenic types are there. And PAHs, I mention they're in soil because they come from incomplete combustion of organic materials. Meaning auto exhaust is a source, any kind of fire is a source -- forest fires, grass fires, home fires, if these areas had fires before on them, or homes burned, or businesses burned, there's lesser amounts in charbroiled food. So any time there's been incomplete combustion you'll find PAH.
So, if the soil has PAH to begin with, you have to really talk about, well, how much is in the urban background, naturally occurring? And do I really have elevated levels at this site? Meaning do I have PAHs that can cause health issues, and then you're going to be focusing on those PAHs that are the most risky, which is likely benzopyrene. But there is an urban background for BaP. It's out there and it's all over the city.
Lead, you're going to run into lead, of course, a lot, because lead was commonly used in paint and gas. Most of the lead from leaded gasoline was deposited within 100 meters of the road from car exhaust. Lead paint is basically found quite a bit in these areas from old lead paint. We know the health effects with lead in urban areas. We know the problems in Cleveland and Cuyahoga County. There are elevated blood lead in children in those areas. A lot of that's probably due to house dust, not the soil outside. But nevertheless, soil is considered a source.
So we know that there's an issue there because we have a health effect. By the way, Cleveland's not unique. Most urban soils have historical lead contamination. This data's from Baltimore, and you can see it was collected in 1983. Just to show you that the average content of lead in the inner city is 1,000 parts per million lead. In the 1 to 50 kilometer, 424, and notice this was collected from garden soils. So you're going to find lead in the cities in urban areas, historical areas, not an uncommon issue.
So what exposure pathways are you going to worry about from these contaminants? How do we get exposed to these contaminants? And for humans in garden scenarios or urban scenarios, you could think of water, or you could think of ingestion of soil, which is usually called incidental ingestion, which means dust, includes dust. Or taken up by produce and you eat it. Lead and many of these trace elements, and many of the organics, are very insoluble, and because of that they're not in the water, and they don't get absorbed by plants. They have very little availability.
So the risk driver usually become soil ingestion, not food chain or drinking water in these areas. So the residential standards many times are based on soil ingestion or incidental ingestion, and usually by children. So really, that becomes the risk driver that's released in gut, ingestion of soil.
How do you assess the contaminants in a soil? Well, people usually measure total content. If you've never seen these total content methods, you basically boil the material in acid until most of the soil dissolves. So they're very, very aggressive extractants. But they're meant to be. They're meant to measure the total amount in the soil. But this amount may never be available to a plant. Then you compare your soil lead to the soil screening level.
If your soil -- for example, if we're talking about lead, till the soil lead is greater than the soil screening level, then you might have an issue. You have to do further investigation. If it's not below it, you're done. If you're below 400, below the screening level, you don't need further investigation. So for EPA's screening level, and many other people's screening level's 400 part per million for lead. So if you're above 400 you need further investigation, below 400 you don't.
Ohio EPA has a Voluntary Action Program, they have a standard for lead, which is 400 part per million, or 400 milligram per kilogram. So this is the screen level that actually is on sites.
OK. Let's go back to our two sites, our two urban sites. The top site, the soil was analyzed. The total content of lead was 221 to 391 part per million or milligram per kilogram. You compare that to the soil screening level of 400, it's below it. It doesn't exceed the soil screening level, so you don't have any concern, or I should say, further investigation is not needed. So that's a good candidate site for a garden. On a lower site, soil lead is averaging 800, ranging 770 to 900, all above the soil screening level. Can that site be used? I don't know. All I know is if I exceed the soil screening level, further investigation's needed.
So, what you mean further investigation? Well, you could look at the risk assessment associated with that soil ingestion pathway, which is the 400 space, and look at chronic daily intake of lead. So this equation, actually, can be used to estimate the chronic daily intake of lead. If you eat soil with lead in it, this equation can calculate how much gets into your blood. What does it depend on? The total lead content, which is the soil lead in brackets, and a few other things -- exposure frequency, how much soil you eat, and the bioavailability of lead in that soil -- how much dissolves in your gut and gets absorbed.
So how do you reduce the risk from exposures of soils, like that last one that was above 400 part per million. Well, you reduce these source terms, and then you reduce your chronic daily intake. The first term, how do I reduce soil lead? Remove the soil. Take it out. Take it away. No more lead. That'll get rid of the source term. That's really expensive. Really expensive, and then you have to replace it. Another way might be to deep till the surface with the subsoil, if the subsoil has low lead. And this way you dilute the lead.
The other terms in blue, it's duration, frequency of exposure, and the IR, the Ingestion Rate. You can reduce them by limiting your exposure to soil. One way to do that is to put raised beds in. There might be techniques, mulching, plastic techniques to reduce exposure. And the last one, the bioavailability term can be reduced by reducing the lead bioavailability by soil amendment.
Lots of great information out there on using phosphates, phosphorous fertilizer to reduce lead bioavailability. So that's an easy thing that can be done on site. You could use bone meal for an organic source to reduce lead bioavailability. And actually, there's a lot more than you could use than just lead, and Michele Mahoney is going to be talking about her document here. I'll leave this to her to talk about using soil amendments for remediation, reuse and revitalization.
Arsenic, other contaminants to consider, let's pick arsenic. There's several elements we could look at. The soil arsenic on this site was 8.9 to 13, average of 11.4 part per million. Community garden site below 7 to 10 part per million. So averaging about 8 part per million. Now, what I want to mention is how do you evaluate these numbers? OK, I've got 11.4 in one, saw 8 in the other. If you use the Ohio VAP number -- there are actually two numbers. One is a carcinogenic soil screen number, meaning arsenic being evaluated as a carcinogen. The Ohio VAP is 6.7. But the non-carcinogenic screen is 21. So, both soils are above the 6.7 VAP, but below the 21.
It looks like I'm having a hard time advancing here. Can you hear me?
STEPHANIE CWIK: Yeah, we got you.
NICK BASTA: You got me, but I'm having a hard time advancing for some reason. OK, there we go.
So how do I evaluate this? Well, I'm above the Ohio EPA VAP of 6.7, but this is a map of the State of Ohio and the arsenic concentration, and many of our soils have natural background greater than the VAP of 6.7. And by the way, this is going to happen not just for arsenic, this is going to happen for heavy metals, and it's also going to happen for PAHs where we're going to see large areas of soil in the state that are above the screen level, the VAP.
So then the real question is what do you do next? How do you evaluate that? You're above the screening level, you usually do further investigation. If you use a EPA Superfund number -- here's one screening level from Region 9. The arsenic soil screen level is 0.4 part per million arsenic. And I can tell you all of Ohio is above 0.4. In fact, all of the world's soils are above 0.4.
So, exceedingly the soil screening level is not uncommon for screening sometimes. So I would just want people to know, when you exceed the level, that's OK. You just have to do some further thinking about this.
So what does it mean, when our natural soil background exceeds a generic screening level for arsenic or something else? Well, you could say, well, you know, those are risk-based numbers, and if the natural background soil exceeds the screening level, it might cause cancer. But this is just natural background we're talking about. It's not extra arsenic. Or you could say the screening levels are conservative estimates or overly conservative, and they're meant to be because they're screening levels -- screening levels are conservative. So if you exceed them, you just have to think about this a little more, maybe a little further risk investigation.
What's the thinking? The thinking should be exactly what Dave mentioned before. You should then compare it to the natural background. And if you exceed the screen level but you're still within the natural background or urban baseline, right? Then you're fine. You’re not really talking about probably any kind of adverse effects unless natural soil causes adverse effects.
So I guess with assessment, there really might be two screen levels. The first screen level might be what's the natural baseline background soil level? What's the natural level that you would find? For example, with lead, the natural soil uncontaminated level for lead is 20 to 50 parts per million. That's any kind of soil that is uncontaminated, pristine soil. But in cities, the urban baseline usually runs between 50 to 200 because it's already been contaminated from lead paint, lead exhaust and other things. But that's still not an adverse health effect, it's just elevated.
The second screen level is risk-based, adverse effect type numbers, and for lead, that number's 400. So you see with lead, we already have a screen level that's above the urban baseline and above the urban background. We probably are going to need that for the other elements and other contaminants. I don't think we have that right now for many of these other contaminants.
So if the soil concentration's above the second screen level, then what you do? Suppose you're above 400 lead, what do you do? Then you're considering cultural management practices to reduce the exposure. And that means we're back to this slide I talked about earlier. If you're above 400 lead, you're reducing the ingestion, the concentration term or the ingestion exposure or the bioavailability. OK? And so with that I'll open up to questions. Thank you.
STEPHANIE CWIK: Thanks Nick.
JIM VAN DER KLOOT: Very good. One commenter pointed out something important here is that in putting on a Webinar for a broad audience, we weren't able to really address how the standards apply differently from state to state. So we want to caution you that the 400 part per million level, there's a soil screening level, but there isn't really a nationwide standard. These are applied somewhat differently from state to state. Each state may have different approaches to sampling and what they consider to be acceptable levels. And so that's an important caution there.
NICK BASTA: Yeah, I get it. In fact, I don't think we really have many urban garden soil standards at all. Right?
STEPHANIE CWIK: Right. One more quick question for you, Nick. There was a question about should phosphorous run-off be a concern if you're applying it to the soil for lead?
NICK BASTA: Yeah. This is something you have to watch, the type of phosphorous treatment you add. Now, the hydroxy apatite that I mentioned has virtually no solubility. The phosphorous is basically bone material. Very insoluble. So you could rain on bone apatite and you don't get phosphorous run-off. So that's a very safe source to use, and you won't get phosphorous run-off. But there are other sources like some commercial fertilizers where you're going to get elevated phosphorous levels, and you could have some run-off in the first few years. But you have to really -- I think you have to think about this. But honestly, there are sources that have minimal, if any, like the bone meal. I mean you're not going to see any soluble P.
STEPHANIE CWIK: Great. Thank you so much. We have gotten a couple of other questions for you, but we'll save those for the end and move on to Steve Rock and Kirk Scheckel from our office of research and development to talk about phytoremediation in urban soil. All right. Kirk and Steve, you've got it.
KIRK SCHECKEL: Am I starting, Steve?
STEVE ROCK: Sure.
KIRK SCHECKEL: Well, thank you for having us here. I'm trying to get a couple things arranged here. We were tasked with trying to narrow the focus on plant uptake of metals and contaminants, particularly in the case of bioavailability, plant uptake, and phytoremediation. And some of the questions that we had pertain to what do we know about plant uptake of contaminants and how this relates to specific contaminants that are commonly seen at Brownfields sites, or potentially in urban gardening. One question may be for the audience as well is how is plant uptake determined? How do we measure that to see if it is an agent of concern that we should be worried about?
As a couple of previous speakers have mentioned already, that not all metals are the same because a metal or a contaminant that may be taken up by one plant does not mean it's going to take up all contaminants that are at that particular site. And we also have to be worried about organics as well. The kinds of plants that preferentially take up contaminants are fairly rare, but they are out there. And they typically are not the typical vegetable garden or vegetables that we consume. They tend to be very unique plants from very unique plant species.
So with that in mind, we'll move on to the next slide. And I'll let Steve take over from here.
STEVE ROCK: Great. Thanks, Kirk. So we're going to be talking a little more about the inter-relationships between plants, soil and contaminants. And there's two different focuses for that. One is what can plants do to contaminants, that is what we call phytotechnology or phytoremediation, using plants to improve the environment vis-a-vis, the contaminants. And also a little more of what Nick was just talking about, about the pathway of contaminant from soil to plant to human. And like everybody else, we're looking at the applications for urban soil, which are going to be specifically metals on chlorinated solvents and pesticides.
The plant-soil relationship is much more complicated than most gardeners think. We tend to imagine that we put this plant in the ground and basically the soil provides nutrients and a little stability to hold the plant up. In truth it's a pretty complicated physical and chemical set of relationships. Both water is going into the plant from the soil and the air, going out of the plant into the soil and into the air. Chemicals are moving in both from the air and the soil, being transformed, in some cases, and being released both into the air and into the soil.
One thing that we found that's particularly interesting is that plants create exudates, and some of those exudates are specifically used for cleaning up the soil around the plant. That is, in some cases, when a plant is growing in a minimally contaminated area, perhaps it has too much of the PAHs that were talked about before, plants will start to exude chemicals that will start to break down those contaminants.
So after a certain amount of time, you do have a cleaner soil. The plants create more area for their roots to explore. Partly they do that through chemical means, partly they do that through biological means of encouraging the microbes in the soil to help them out. It's a pretty interesting, and like I say, complicated set of relationships.
What we'll be talking about next, though, are simplifying that. The research that's been done at EPA and a lot of other places has broken this down to two different mechanisms. What we call phytoremediation, which is cleaning up the site, breaking down organic materials, mostly contaminants, but all organic materials break down in the presence of plants and microbes and worms. And then phytoextraction, which is the removing of metals from soil. It's gotten a fair amount of press over the last 10 years, some of which is unjustified, and some of which is actually quite useful. Next slide.
Phytoextraction is a technique, a technology, for cleaning soils of metals. Because metals cannot be degraded, you actually can't get them out, destroy them, any other way. You can make sure that they can't move in a soil, and some of the phosphate treatment that Nick alluded to before. But naturally, they won't move into a plant very easily. You can, however, change the metal or change the soil conditions so the metal will either move more or less easily into or away from the plants. And the next slide.
So, ideally, what happens is you have a set of contaminants in the soil -- here we have nickel, lead, zinc, mercury and cadmium. At some point, you grow a certain kind of plant. This is a broccoli relative. Brassica plants tend to take up some metals in them. And what happens is the plant will take up some of the metals, you have fewer in the soil at that point. And if you harvest that, you can then take away the contaminated plant and leave a cleaner soil behind you. If you harvest that and take it to your table, you are then going to ingest any of the metals that have moved into it. That's both the sort of promise and the fear of phytoextraction of metals from contaminated soils.
The good news is it's very rare. I mean for a commercial firm that wants to clean up soil with plants, it's not particularly good news. There are some plants that will take up some metals in some conditions, but most plants will ignore the metals unless the conditions are very, very carefully arranged. If anybody could find a plant that will take up lead in interesting quantities or dangerous quantities, I would love to know about it. If I could find that plant, I would probably quit my job immediately and form a company and start cleaning up soil with plants. There isn't one out there as far as I know. But that hasn't stopped people from trying.
There have been several well-known studies, some fairly highly publicized things, about ten years ago that suggested that you could, in fact, clean up soils using either mustard plants, brassicas or sunflowers. EPA was involved in some of those studies as an observer. We saw that you could, in fact, induce some plants to take up some metals, but not enough by themselves.
So, natural hyperaccumulators weren't happening. And then there is a way to do chemical enhancement to mobilize metals, especially lead, that moves into plants, and we found that those were not only very expensive, but unreliable. The short version of that research was that those studies tended to mobilize the metals away from the plant as much as into the plant. So that as much was collected and harvested by the plant, equal amounts or more slipped away, skipped into the ground water or the surface water and moved into the environment, which we thought was a really, really bad idea. So I guess I would not advise anybody to try and clean your soil of lead with plants.
Cadmium, zinc, chromium are also talked about as potential candidates for phytoextraction. Similar problems for them, although there have been some hyperaccumulators identified. They are slow or small or specialized or only live in the mountains of Crete, and we haven't been able to grow them in other places commercially yet.
The chemical enhancements that can be used to mobilize some of those contaminants are fairly common. EDTA is an industrial solvent. It's also sold in health food stores as a way of cleaning metals out of people's bodies, actually. Ingest the solvent, it picks up the metals and moves them, much as it is supposed to do in soil. Citric acid is another one. But, like I said, they are all environmentally risky. They do mobilize the metal, and not specifically move it into the water, as well as into the plants. So, not yet ready for prime time as a technology, which is probably good news for gardeners. It means that these metals will not move easily into any plants that you're likely to grow in your garden.
The next slide talks about some successful natural accumulators. Nickel is one that will move into plants very nicely. There are, in fact, commercial companies that are using nickel for extraction. There is some amazing plants that if you -- in fact, they use these plants for prospecting, for finding nickel deposits. If you tap the sap of some of these trees, the nickel will actually flow out of it in large percentage. 11.2% is the wet percentage, 35% percent is the dry weight percentage for nickel in the sap of these plants. Like I said, that's being commercialized. However, nickel is not much of a contaminant for us. We're not too concerned. You haven't heard it talked about before. Unfortunately, we have a tool that will clean up nickel contamination, we just don't have a nickel contamination much that needs to be cleaned up.
Mercury is something that we do find in soils fairly regularly. There are a couple plants that will take mercury out of the soil, transform it into a less toxic form of mercury, and then volatilize it into the atmosphere. EPA has not ever endorsed that technology. It's called media switching, although there have been some demonstration studies done and it is reasonably successful.
Some states will allow that as the technology, with the idea that it's better to get mercury out of the soil and into the atmosphere as elemental mercury where it is less toxic and will do less harm, so they say. Not a widespread problem mostly because if you have mercury in the plant root range, that is the top, say, 8 inches, 12 inches of soil, and you till the soil back and forth, mercury's going to volatilize pretty much before the plants have a chance to get to it.
Another phyto success story is arsenic. There are several hyperaccumulators. There's one that grows pretty readily in this country in a number of different areas. The arsenic brake fern, or Pteris vittata, grows fast, grows large, will accumulate a fair amount of mercury -- sorry, of arsenic naturally, and can be harvested. In warm climates, if you harvest the fronds, the roots stay intact and will grow another crop for you either the same year or the following year.
In cooler climates, you have to do some very heroic measures. You have to cover it with a couple feet of mulch to keep the plants alive. They much prefer subtropical areas, southeast China and Florida, but it has been grown successfully as far north as New Jersey. So, that's a plant that has some success. It's been used to take arsenic out of housing developments, especially when you don't want to go in and scrape the soil, dig it up.
There's a successful case study in a suburb of Washington, D.C. where a residential area -- houses, sidewalks, driveways, trees -- lots of arsenic in the soil. They planted all the available space with break ferns for several years in a row, and were actually able to take the soil down to reasonable levels and not disturb any of the sidewalks, driveways or trees while they were doing it. So, that's sort of phytotechnology at its best.
There are plants that will help degrade most of the VOCs that are likely to show up in urban soils. A lot of the TCE, DCE, PCE family comes from dry cleaners specifically, or body shops use those sort of solvents. Those will break down fairly reasonably in the presence of plant roots and their associated microbes. Some plants seem to do a little better than others, but generally it's just having a vigorous root zone that promotes the degradation of the light solvents.
So, it's one of those truisms that we keep coming back that if you have good gardening practices, if you get the pH in the right area, work organic material into the soil -- if you make it so the plants will thrive, you're going to be cleaning up some of the contaminants anyway. So that's the good news about some of these contaminants. It may not be an issue, and if they are an issue, they will continue to clean themselves up.
One area of increasing concern is that there is one particular type of plant, certain kinds of squash that seem to defy the rules of plant physiology, and they will take up chlordane, DDT and PCBs. Mostly those don't move into it any other plants, but they have been demonstrated to move into these plants in a couple different laboratories, one in Canada, one in Connecticut. It's not sure whether they move into the plants to the point where you can use them as a way of cleaning up the soil. They don't seem to accumulate in the fruit of the plant nearly as much as they accumulate in the roots and some of the shoots of the plant.
That research is still sort of in early days. If you are growing those in a place where you know you have this contamination, you probably want to be particularly careful about the waxy surfaces -- cucumbers and squashes have very waxy skins that you're going to want to peel before you consume them. Probably not a bad idea in most cases anyway, as those surfaces will accumulate dust, and we're not entirely sure what's in the dust of urban soils in general. The air of urban soils, for that matter, is going to accumulate on those plants as well.
So, as has been mentioned before, what we're really thinking about is perhaps maybe not so much what will move into the plants, but using the plants to help keep the gardens clean for you. One thing that seems to be true is that there is more hazard coming from the dust of the soil than from anything that will be taken up by the plants. So one of the main advantages of covering urban soils with gardens is that there will be less urban soil moving around in the form of dust.
If you grow a garden and you have areas that are not planted, then if you mulch those or plant a cover crop or let a grass grow on that and keep the dust down, that's probably the most useful thing you can do. The same is actually true for non-gardens. If you have an urban lot, it's probably best to keep a plant cover on it as much as possible anyway, and it doesn't really matter what plant, as long as it's fairly vigorous with as close to 100% vegetation coverage as you can.
If you do a few minimum garden practices like ensuring the proper pH, keeping up the phosphate levels, you're probably not going to have contamination into plant problems. Really, it's not going to be easy to move them into the bioavailable range. And as I said before, nickel and arsenic can move into plants, you have to work at it though, and there are very, very few plants that do it, even fewer of which are edible. Some of the oils and solvents will degrade in the soil, which is nice -- don't have to work at it too much. Just grow those plants and they will help you clean the contaminants up.
KIRK SCHECKEL: All right. That's it.
STEPHANIE CWIK: Well, thanks, Kirk and Steve. We have just a couple of seconds here before our next talk, but I just wanted to bring up that you mentioned squash and pesticides and that mostly nothing's going to move into plants. But we've heard things about should we worry about tomatoes or our carrots or our leafy greens. Could you just reinforce that real quick for us?
KIRK SCHECKEL: Do you want me to take that?
STEVE ROCK: Sure.
KIRK SCHECKEL: And for each plant it's element-specific. I mean there's research out there from the 70s that had demonstrated cadmium uptake into leafy vegetables, such as Swiss chard or lettuce. So if your soil's elevated in cadmium there could be a concern there. And tomatoes that you tend not to have an issue within the fruit material, but you could have some accumulation of contaminants within the roots, so very similar to the squash situation. Zinc never tends to be an issue with plants because you'll never get enough concentration of zinc into a plant, because the plant will actually become phytotoxic before it gets to a level that would cause harm to humans. The plant would eventually die before it reaches that level.
STEPHANIE CWIK: Great. Thanks. So, thanks so much for that, you guys. And last but not least we have Michele Mahoney of the Office of Superfund Remediation and Technology Innovation, to discuss using soil amendments to reuse urban land. Michele, are you there?
MICHELE MAHONEY: Yes, I'm here. Thank you, Stephanie. I'm going to pull up my presentation. I've pulled it up, can you see it?
STEPHANIE CWIK: We see your desktop -- there it is. Thanks, Michele.
MICHELE MAHONEY: Great. And thanks for having me as part of this presentation today. Like Stephanie said, I'm Michele Mahoney. I work with USEPA in the Superfund Program in the Technology Innovation Office. I work primarily on large sites that have had mining issues or some sort of land degradation in which we've had success in using soil amendments to not only remediate the contaminants on those sites, but also build the soil so you can actually grow something on them. Because a lot of these sites, all the soil has been removed, and essentially there's nothing there that can support plant life.
So what I'm going to present to you today is information that was gathered probably about four or five years ago on using soil amendments for remediation and reuse of sites. Basically, this document gives background on what soil amendments are and how they can be beneficial to soils. I guess I'm going to go through a lot of information in this presentation, but also referring you back to this document, because I think it can be very valuable in urban gardening scenarios because a lot of the information in this document can be related to some of the contaminant issues that you'll find in some of these urban soils.
As I mentioned, soil amendments can be used to not only mitigate the contamination issue, but are also valuable for just building healthy soils. People are always using mulch and compost and things like that to build their soils and keep weeds down, and just make a better environment for plants to grow.
Another good thing about using soil amendments is that you're recycling organic materials that may have otherwise been destined for a landfill. Whether it was the feedstocks that went into making the soil amendments, whether it's food waste, yard waste, and things like that. We've been studying the use of soil amendments and I have lots of examples for well over a decade now. So, I'm going to present a bunch of information. It is available on this paper, the cover is on this slide, and I'll provide a link to that paper as we go throughout the presentation. You can also feel free to contact me if you'd like a paper copy of the document.
So, soil amendments are generally residuals from other processes that can be used to reduce exposure -- reduce the exposure pathways or limit the exposure pathways of a lot of contaminants, and also immobilize contaminants, limiting their bioavailability. They can also be used to restore soil quality by balancing pH, adds organic matter, which increases the water holding capacity of soils, re-establishes microbial communities, and alleviates soil compaction. It has also been shown to lead to site remediation, revegetation and reuse. Using soil amendments, as I mentioned before, can avoid landfill disposal of these materials. We also have been doing some studies and how it increases the land's ability to store carbon, which can have a greenhouse gas importance.
So this is a list of some of the commonly used soil amendments, some of which can be used for gardening, such as composted organics and lime and fertilizers. So, some of the benefits of using soil amendments is to improve your soil quality, decrease the bioavailability and mobility of contaminants in your soils. In some cases, it may be the only economically viable treatment option. If you have a large area in which you have elevated levels of contaminants, removal may not be an option, and filling in with clean, you might only be able to use soil amendments to bind up the metals and reduce exposure. Then also, recycling the municipal and industrial materials and putting them to a good use so they're not put into our landfills or incinerated.
Ways in which soil amendments can help mitigate exposure to contaminants, the metals in the amended area can be chemically precipitated by using soil amendments, and they can be sequestered by complexing and sorption mechanisms within the contaminated substrate. Which leads to minimization of the metal availability to plants. Also, the leaching of metals into groundwater is reduced. Then also, the availability of the metals below the treated area may also be reduced. Then the main thing is once you reduce the exposure is getting your plant establishment, which can help stabilize the landscape from erosion and reducing any run-off of contaminants or sediment losses and things like that.
So, some of the problems that can be addressed at sites by using soil amendments is the toxicity of various soil contaminants, principally metals that can be harmful to plants can be reduced. They can be used to deal with soil pH, since high or low soil pH can cause soil infertility and can cause some metals to go into solution. You might have an excess sodium problem, which can cause toxicity to plants, and also break down the soil physical structure and disburse soil which can lead to limited root growth and limited water infiltration.
Soil amendments can also help in situations where there's excess faults that are limiting plant rooting and water and nutrient uptake. And then also, soil amendments can improve soil physical properties, like soil density, aggregation, texture. And can also help with water infiltration and moisture holding capacity of the soil. Soil amendments can also be used to address deficiencies in some micronutrients like zinc and manganese, which can sometimes lower the fertility of soil. However, you want to keep in mind that some of those elements can also be toxic at higher concentrations.
So, what I'm going to do in the next couple of slides is present to you how you can find more information on soil amendments in this document that we have produced, which has a plethora of information on all the different types of amendments and sites that can use soil amendments to remediate soils. As you see on this slide, this information here is in Table 1 of this document where we talk about how soil amendments can be used to address two primary categories or problems at contaminated sites. One being contaminant bioavailability and phytoavailability. Then also, the second one being poor soil health and ecosystem function.
So, some of the specific problems, as I mentioned before, is the toxicity, high or low pH, the sodicity, salinity, soil physical properties, and nutrient deficiencies and low fertility.
So here's a closer picture of what Table 1 looks like and how it's organized by the problems that I just identified on the previous slide. So, for each toxic element that we're concerned about, the table will identify the exposure pathway for that toxic component, whether it's phytotoxicity, food chain contamination, soil ingestion, run-off, leaching. Then also the concerns with interactions of that contaminant, such as some contaminants can be co-occurring. Interactions based on the soil pH or the calcium concentration.
Then, also, the table offers solutions on how to alleviate that toxic element of concern. Actually, most of the solutions that we found to these contaminant problems is to raise or lower the pH, add organic matter and/or phosphate, and then also tillage and other management type solutions.
So, an example here of what you would see in this table, I'm going to let you know what it says for lead. So in the first column, it would say "toxicity lead," and then under exposure pathways and adverse effects, we'd let you know that the exposure pathway for lead is soil ingestion. Then the interactions that we know about for lead is that if there's low phosphorous then it can be more toxic. Then the solution would be to -- it would be dependent on whether or not you have arsenic present. If there isn't any arsenic, you would raise the pH to six or greater, and then if arsenic is present, you would want to raise the pH to five and a half to six and a half, but then also add phosphorous and iron oxide.
So, this slide, we're moving on to information that you can find in Table 2 of this document. And this is where we've organized using soil amendments by the types of sites that you would use them at. We have identified the contaminants, the problem, and the solution associated with these types of sites. So some of the contaminants that are addressed are inorganics, organics, metals, nutrients and others. Then, the example of the type of site that would be related to urban soils where there would be gardening are mixed contaminant sites where we tend to find low levels of metals and organics.
Then this information moves onto the Table 3 of the document where we talk about the types of soil amendments. So that would be the type, the mix, the amounts of soil amendments that you need, varying from site to site. You'd have to look at what your site contaminants are, soil conditions and types of desired vegetation. But the first and most essential component of using soil amendments and creating a strategy is really doing an accurate assessment of your existing soil site conditions, and have a knowledge of the range of your target soil conditions appropriate for the vegetation you're trying to grow. Really, the application rates are site specific. You're going to be using higher rates of soil amendments when you're really rebuilding soil that has no quality, as compared to just remediating a damaged soil.
So, for the various soil amendments that we have listed in this table, we present the availability of these amendments, what their uses can be, the public acceptance, the cost advantages and disadvantages. Then there's also some links to other resources, whether it's associations or other individuals that can provide you with more information with use and availability of these soil amendments.
So, as far as the soil amendment and its availability, soil amendments are pretty much available almost anywhere. Some of the sources that you're going to find are your publicly owned treatment works, your animal feeding operations, and also, especially for gardeners, your retail sources. What you'll find as far as the uses of these soil amendments, as you might be needing a nutrient source, an organic matter source, an amendment that can adjust your pH and improve the overall physical properties of the soil.
As far as public acceptance, we've identified issues that we've come across and we've learned about that may arise in terms of public acceptance of using these different types of materials. We also have gathered information on what the cost of the materials may be. Then also the consideration of transportation and application of the materials and what cost is associated with that. Then, also, identifying the advantages and disadvantages of using each of these amendments, whether it be economic, environment or social.
Then, also, for each of these different types of soil amendments that can be used for building soils, we've outlined the logistics associated with using them, transporting sources. If you have to store the material on site for any period of time while you're prepping the area. If there's any blending, if you need to use one amendment for building organic matter, but then you also need to use another amendment for adjusting the pH -- what you might think about in blending those materials for the application. Then also talking about different types of application methods that are used for the different types of amendments along with any potential equipment you might need.
Then just some of the other considerations to think about when using soil amendments, particularly with the maintenance aspect of soil amendments, and particularly with gardening, is most likely you'll be applying some sort of composted material on an annual basis to just to keep the soil in good quality and weeds down.
Then this table, we summarized the common types of equipment that can be available to apply amendments to soil, along with their limitations, cost, advantages and disadvantages.
Then, also, provided -- we have some information on the regulatory requirements for sites that are using selected soil amendments. I'm not sure exactly if all this information would be directly applicable to a gardening purpose, but I wanted to make you aware that this information was there and that there are a variety of regulatory requirements that may pertain to different types of soil amendments. And you just want to just be aware of that.
Then here's my contact information, along with a link to the document that has much more detailed information that you can look up, and your specific site toxicity concerns and find out what potential soil amendments might be able to be used at your sites. Then we also have on our Clu-In website an EcoTools web page, which talks a lot about soil quality and finding resources in areas where you live that can help you in cleaning up a site that you want to put into a good reuse such as gardening.
So that's all I have.
STEPHANIE CWIK: Thanks, Michele. One question that we had was how do you verify the reduction of bioavailability?
MICHELE MAHONEY: Well, you would have to take some testing before the amendment. Then you can either do some -- what we doing in our cases, we'll do some pot studies to see which amendments will change the bioavailability of contaminants in soil. But it's basically doing a before and after type of measurement.
STEPHANIE CWIK: OK. So, thank you, Michele. And as our attendees are furiously typing in questions for us, I hope, I'm going to send out a question to all of our presenters now, and ask what are the gaps in knowledge that you've identified? What research still needs to be done? I'm just sending it out to everyone. So whoever would like to speak first, go for it.
There's nothing. We've covered everything.
NICK BASTA: Well, I'll jump in.
STEPHANIE CWIK: Thanks.
NICK BASTA: I think that there's a lot of different things that could be done. But having said that, probably the most immediate thing that's holding people up from getting urban gardens off the ground is some kind of assessment framework. And this assessment framework for -- really we have to be talking about risk-based standards to be developed. And we have to have a contaminant list that's more applicable for urban gardens, not Superfund sites.
So, we really have to be careful. These are not Superfund sites we're studying, it's going to be a much more limited number of contaminants. But right now I think what's holding people up is concern over having a structure in place, a framework that they can know how to sample, know what to analyze, and compare it against numbers.
STEVE ROCK: In addition to that, there aren't good tests for a lot of what we're trying to find out. If you want to do a bioavailability before and after test, it's hard. It's hard and expensive, and we're not exactly sure how to do that. It's not something that a gardener or even a group of gardeners in a community garden are going to be able to pull off. Certainly it's not going to happen on any kind of a smaller scale because those are tricky tests. Even getting the basic tests on metals is increasingly difficult and expensive.
NICK BASTA: But we do have tests. I mean we do know how to evaluate the pre and post for bioavailability. It's just that what we need to do, and we do this all the time, is basically like, for example, with 503 regulations and all. We don't expect everybody to go out and do all the testing by themselves. We actually leave that up to research people to do the testing. Then they recommend management protocol so that people know that if they add so much compost or so much rock phosphate, that they'll reduce the bioavailability 50%. I think that's what we got to be doing. We can't be asking people to do bioavailability tests. We have to be coming up with the bioavailability measurements and giving recommendations of how much of what to add to reduce the bioavailability.
LILAH ZAUTNER: I would just, in terms of from a practitioners perspective also add to what Dr. Basta just said, that from our perspective, we understand that there is a lot of research that needs to be done. But from our perspective these projects, there is a certain level of urgency because research or not, fortunately or unfortunately, projects are going forward each and every day in Cleveland as well as across the nation, that these projects are moving forward. And the 503 kicks in when you're using Federal dollars.
Projects that don't use Federal dollars aren't required to meet any sort of standards and aren't required to show any sort of due diligence as far as soil testing and recommendation. So the sooner that we can get, as Dr. Basta said, just some basic information and guiding principle as to how much is too much, and then options for soil amendments and remediation, the sooner the better on that. Because the sooner we can actually get them into projects hitting the ground, the better health and safety going forward.
So I would just say some sort of best practices that practitioners can rely on and that can actually be submitted to environmental compliance officers, and to agencies that are acceptable and will allow projects to move forward. Then, also, can be given to the grassroots organization that aren't forced with having to comply and are moving forward anyway.
Lastly, that those guiding principles, based on the research that exists today, be put into a format that is easily understood and can easily flow into existing networks around local food and agriculture.
KIRK SCHECKEL: There was one question that came through asking about 400 part per million being too conservative for urban gardening. I guess just to back up a little bit, numbers like the soil screening levels that are developed, Nick, and I can't remember which of the first three speakers brought it up as well, is that those numbers are assuming that an individual is in constant contact at a site, that you live at that home site. You have so many days a year exposure to that.
If you consider an urban gardening situation, you go out there and you work on the weekends or maybe one night a week. So you have two or three days a week that you're there over a few month period, that your exposure to that site is typically much lower. So I think what Professor Basta was kind of alluding to that those numbers are conservative in terms of your total exposure, rather than just the full content that you'd get if you lived at that site.
STEPHANIE CWIK: And just a quick note, in our next Webinar, we're going to be talking policy questions like those, and we'll have some of our folks from Ohio EPA talk about how they're looking at that question in specific.
Another great question we got was "Does reducing bioavailability of soil contamination help if soil is directly ingested, or is this simply less available for plant uptake?"
NICK BASTA: Yes.
STEPHANIE CWIK: Speak up.
KIRK SCHECKEL: Well, Nick I can answer that one, too.
JIM VAN DER KLOOT: And this is Kirk Scheckel speaking.
KIRK SCHECKEL: A good example of that is a lot of mining sites have had these issues before where you have a lot of dust blowing contaminated soil around. Mainly because the plant growth was just unable to be accomplished there due to the toxicity of the metal. And through a soil amendment, you could bring back fertility to that soil, get a plant base established, and you could also demonstrate a reduction in bioavailability through ingestion from animal studies.
So, work like this has been done before, but in a different context. So I guess the question being asked there is yeah, if you can reduce the bioavailability that will reduce the amount of plant uptake, there's probably a very good chance that you're also going to reduce the bioavailability if the soil's ingested by the urban gardener.
STEPHANIE CWIK: Thanks. And thank you to all of you for your many questions. If we don't get to your question, I assure you we are seeing them all, and we will try to post them up on the brownfields/urbanag website after our presentation is done here, since we have only ten minutes left.
Another question to our panel is when you're assessing a site, does the presence or appearance of weeds and shrubs indicate any specific problems or contaminants? Can you tell anything by just looking at what's growing there already?
STEVE ROCK: Absolutely not. Some of the most contaminated sites tend to be the most pristine because people stay away from them and they look wonderful and lovely, and just because the plants are growing there doesn't means that the site is clean or that the plants are clean, actually. The extreme example of that are the old nuclear bomb-making sites, like Oak Ridge, where people have been excluded for 50 or 60 years, and not only the plants, but many of the animals are radioactive. So, no, you can't tell by looking. You really have to sample a site to understand what's going on there.
STEPHANIE CWIK: Thanks. And then a couple of questions about exposure. "If plants are not likely to take up most contaminants, is the risk to growers involved with the direct soil ingestion or contact? Like are the growers more at risk for exposure than the produce consumers? Also, is dermal exposure a risk or should airborne deposition be considered?" That's a lot of questions.
NICK BASTA: I think that what Dr. Scheckel said was right on the money where you have to -- ingestion's usually the issue, but there's assumptions in there -- exposure frequency and duration. And I would say it's going to be different from urban gardens just because people aren't out there every day, and maybe those numbers are pretty conservative numbers. So, I guess if ingestion's the issue, I'm not sure how we adjust those numbers, but we have to come up with some protocol how many hours that people are out -- I don't know how much risk there is to growers, really.
KARLA AUKER: My perception of what the question is is for the growers, are we more concerned -- or is the risk mostly ingestion of the soils of growers that are out there working the soil, versus eating the fruits and vegetables from the garden. Correct me if I'm wrong, but my impression from the knowledge that I've gathered over the last few months is that really it's more of an exposure -- the risk is more exposure and ingestion of the soil as you're gardening as opposed to eating the vegetable. As long as you wash the vegetables and get the soil off of the vegetables that you're eating, your risk of contamination from the vegetables themselves is relatively low.
NICK BASTA: Yes.
STEVE ROCK: I think we all agree on that.
KARLA AUKER: Yeah.
STEPHANIE CWIK: OK. How about "Has there been any success using fungi as a remediation technique?"
KIRK SCHECKEL: There's been some studies in the scientific literature for organics, but in terms of metals, it really would be kind of a useless thing unless you could demonstrate a very specific chemical form shift.
STEVE ROCK: And it's a very hard crop. So, although I have read some studies on that, I've not seen it used commercially.
DAVE BEHRINGER: Yeah. Every once in a while, somebody asks me about bioremediation of lead and metals. It really doesn't work.
KIRK SCHECKEL: Right. Well, Nick, stay close because there's a question that's come up a couple of times about using the IUEBK model to develop a value for lead in urban soils. And Nick's kind of alluded to this a little bit, but you have to have the right criteria in order to put into that model which incorporates the number of days of exposure, the concentration. So there's many aspects I can put into it. And I would assume you could do that, but it would be, again, it would almost be a site-specific or garden-specific number for each of those cases.
Yeah, and it was the IUEBK model that developed the 400 part per million for residential soils to begin with.
STEPHANIE CWIK: OK. Here's another question to our panelists. "What about using Brownfields sites for foragers, like chicken or livestock, instead of for vegetable gardening? What kind of parameters or consideration should someone be aware of before doing that?"
STEVE ROCK: I think it's a broader question of what else can you do with it besides growing food crops. And clearly, if it's not bioavailable for food crops, then it's not going to be much taken up by the chickens, although they're fairly indiscriminate about what they eat, and they ingest a fair amount of soil. Probably chickens are not a bad solution, if you have a site that you're concerned about. Also, I've heard people talking about fruit crops, berries, vines, or flowers are other things that are marketable and a little farther removed from the food chain.
I don't think there have been a lot of studies on chickens in contaminated soil.
DAVE BEHRINGER: I'd like to mention that biosolids was really thoroughly investigated, risk pathways, and what we're talking about, the animal pathway is one of them that was thoroughly investigated. And they came up with a set of standards that were risk-based. And basically, that's something that if you want to start looking at multiple pathways -- you know, whether to grow chickens or different scenarios. There's even the garden scenario in the biosolids part 503. There is a process that was already conducted by EPA to develop standards that way. And so the answer might be out there already and in use for the part 503 standards for biosolids.
Now, whether you want to use them for this exact scenario, I don't know about that. But I think what those standards were showing were basically animal ingestion was not really any riskier to any kind of gardening under any condition. Well, I think molybdenum might have been a case for foraging. But those guidelines they're already out there, and usually animal production on a land is less risky than vegetable production -- of accumulating vegetables like lettuce.
JIM VAN DER KLOOT: This is Jim Van Der Kloot. I just have one statement in conclusion. We've gotten a real lot of good and very specific questions that have come in, and they're a lot more than we're going to have time to over. But I think a lot of the questions really point to the overall problem here. This is an issue on which there are serious gaps in basic knowledge and in public policy. The current systems are not really set up to deal with contamination issues as they apply to community gardens and urban agriculture.
We're very interested in taking a role in helping to fill those gaps and convening the appropriate people to get on that. And your questions, as you've written them in are going to be helpful in helping to find the gaps.
So, thank you very much everyone.
STEPHANIE CWIK: Thanks everyone for spending your afternoon with us. We really appreciate your participation and all your wonderful questions. They're really going to help guide our efforts. This is being recorded. It will be available online in a few days, hopefully, at the brownfields/urbanag website.
JIM VAN DER KLOOT: And thank you very much to all of our speakers.
STEPHANIE CWIK: Don't forget our next Webinar is covering the policy questions around Brownfields and urban ag reuse, and that will be October 7. Don't forget to register for that. And we'll see you in two weeks. Thanks.