Trace Element Contaminents - Paul Grossl

Thanks, Dan.

What's a biogeochemist?

Well, I look at soil chemical interactions

and how that affects—
how those chemicals are taken up by plants

and eventually how
they're transferred into the food chain.

So that's probably
the simplest way of describing it.

But anyway,
welcome to my talk

on trace element contaminants
in urban soil environments.

And before I go on,
I'd like to acknowledge my coauthors,

Melanie Stock and Eli Oliver.

We've been working on a soil survey
of the whole Wasatch Front,

looking at different gardens,
trying to get an idea

of what the metal levels
are in these soils,

as well as organic contaminants.

And we're kind of in the midst of that
right now.

Also, before I go on,
I should probably define

what I mean by trace elements.

They are defined as
having indigenous popu—

indigenous concentrations...

less than a hundred parts per million.

So that's either in the solid
or liquid phase.

So it's interesting.

About 15 minutes before
Dan came to my office

to ask me to present here,

in this vegetable session,

I just got done reading an article
in the New York Times.

You may have seen it,
where it says some baby food

may contain toxic metals
in the U.S.,

and it said that the levels were high
in some of these foods

with arsenic, lead and cadmium.

And as I was reading that,
I noticed carrots came up,

and sweet potatoes,
and I thought—

and then Dan comes to my office and
I said, well, this would be totally ideal.

I could talk a little bit
about what I've found

in some of these urban communities.

Also, this is about the time of year
where a lot of you, and people in general,

are getting, or planning,
their backyard gardens.

And they may not even be aware
that there could be issues

with some of these trace elements.

Now, the two trace elements that I'm going
to focus on are lead and arsenic.

Mostly because they're EPA's
two priority trace element pollutants.

And what I'd like to do
is just kind of give you an idea

of why you need to be concerned
and when you need to be concerned,

an idea of what soil tests to ask for
if you are concerned,

and then some tips on gardening,

if you have soils that
are a little bit elevated

in terms of lead and arsenic.

So what are some
of the health concerns?

Lead—it's the most ubiquitous
toxic element in the environment.

And mostly we're concerned about it
because it impairs cognitive development,

especially in children.

So lead poisoning is the most—

Woops, I got my, panel picture here,
So I'm going to move that—

is the most universal and serious disease
to impact young children.

The most frequent mode of poisoning
arising from ingestion of lead paint chips

and from soil.

And, anyway, most of us,
in terms of getting sick by lead,

70% of it comes from food.

Arsenic, the acute symptoms are vomiting,
if you ingest too much arsenic,

and gastrointestinal distress.

And if those levels are high enough,

you'll start getting numbness and tingling
in the extremities.

Muscle cramps.

And eventually, if you eat enough of it,
death.

Long term exposure,
it's a carcinogen,

causes skin lesions.

It's also associated
with cardiovascular disease and diabetes.

And, it can be linked to negative impacts

on cognitive development
and increased deaths in young adults.

Oops.

Let me go on here.

Here we go.

So let me give you an idea

of what some of the background levels
of lead and arsenic are,

and what they are in urban environments.

So lead in uncontaminated surface soils

ranges from anywhere from 20 to 27 ppm,
or mg/kg of soil.

In urban soil, we find that those levels

start creeping up to
150 mg/kg or higher,

some cases greater than 1000 ppm.

The EPA has set a regional
screening level of 400 mg/kg.

and I'm going to use that
as our kind of action level.

And that's why I have it here in red.

Arsenic, typical background
levels are anywhere from .1,

less than 0.1 to 40 ppm.

Now, the regional screening
levels are all over the place

in terms of how they vary
from state to state...

Even within states and municipalities
as well as EPA—

EPA has set a level of 0.39.

But we're finding that all of the soils
that we test here,

along the Wasatch Front,
exceed that.

And, we don't start getting concerned

until that level starts approaching
20 ppm or higher.

So some of the urban sources
of lead and arsenic contamination,

well, lead comes from auto emissions.

It could be from former paint chips.

In the past, lead arsenate pesticides
were frequently used.

Again, if you're close
to any industry and smelters,

could be a source of lead and arsenic,

as well as mining activities
and biosolids.

Or, if you're adding
composted sewage sludge to your soil.

So when to suspect
that you may have a contaminated soil?

Well, if you live within 20 feet
of an older building,

and usually where that building
had been painted

at least prior to 1978,

there could be the potential
of leaded paint

having been used in those paint chips,

flaking off and entering your soil
near that building.

If you live within 20 feet of roadways,
parking areas, and higher traffic areas,

there's potential for lead being
accumulating in your soil

because of, well, actually,

leaded gasoline was banned in 1996,
so it hasn't been that long ago.

If you live within one mile of smelters,

fossil fuel power plants
and cement facilities,

there could be the potential for lead
and arsenic contamination of your soils.

One thing people aren't aware about
is that if there was a former orchard

on your property,
and that's pre 1950,

lead arsenate was the pesticide of choice,
and that's probably still in your soil.

So, you might want
to have your soil checked

if that's the case.

If you live near tailings
from current and former metal ore mines,

you might want to suspect
that your lead and arsenic

levels could be elevated,

as well as, again,
the addition of biosolids.

Now, before I go on to talk about
some of the best management practices,

I want to just briefly
go over this concept of bioavailability

and how not only plant nutrients,
but how these contaminant trace elements

enter the food chain.

So when I talk about bioavailability,
I'm focusing here—

and see here's my cursor—

The soil solution—
so for in order for those elements

to be taken up by a plant,

they have to be present
in the soil solution.

So some things can be more bioavailable
if it's more soluble.

Or sometimes people refer to
an element as being mobile.

So there's a constant tug of war
going on between elements

being released or retained by the soil
and entering the soil solution,

and then making their way into the plant.

So I want to introduce this concept
of the soil plant barrier.

And fortunately, lead and arsenic
are strongly sorbed to soil

and very little is translocated
to the edible portions of plants,

despite the amount present in the soil.

So if we look at this chart here,

lead and arsenic tend to be retained
by the soil particles.

They're not very soluble or mobile,

and therefore they're not transferring
into the food chain.

So the toxicity from food chain
transfer is low.

And when you ask for a soil testing,
those values I reported earlier,

the test you should request
is the Total Elemental Composition.

It's EPA test 3050.

But that test actually looks at
not only the bioavailable level,

but the total sorbed or retained level.

So the values that we reported here
for lead and arsenic

are mostly the values of lead and arsenic
that are retained by the soil.

So it's not giving you
an indication of its bioavailability.

Excellent article came out in
2015 by Sally Brown.

And I'm just going to kind of
summarize it here.

Recent studies have shown that lead
in contaminated urban garden soils

mainly existed in the carbonate fraction
complexed with organic matter

or adsorbed to iron oxide.

So in other words, again,
lead and arsenic are mostly retained

by some of these soil particle surfaces.

But you need to consider that lead
entering the soils,

from lead based paints,
from the paint chips,

or from leaky gas tanks will generally
have higher bioavailability.

So when you do get your soil test

and you know that it's from
paint chips or gasoline,

there's probably a greater likelihood
that the levels in your plant tissue

are going to be a little bit higher.

Okay, let me talk about some of
the best management practices,

now that we know
how lead and arsenic behave in soils.

Let's focus on vegetables here.

So if you at all expect that

the concentrations of lead and arsenic
could be higher—

So just avoid growing
any kind of vegetable in that area.

In particular, avoid growing
root vegetables and leafy greens

because that's where lead and arsenic
tend to be higher.

So if we're looking at lead uptake,

typically higher levels
are found in root crops.

So we're looking at carrots, beets.

And they're a little bit higher
than leafy crops,

like your salad greens, spinach, etc.

And typically, we find that very little
of the lead or arsenic

is transferred into fruiting—

The edible portions of fruiting plants,
like tomatoes or peppers, legumes,

as well as grain crops.

But it's also just a good idea,
no matter what,

to wash or peel any soil
off the vegetables before eating.

Because that's where the lead and arsenic,
if there is any,

or are any lead laden soil particles,

that's where they're going to be found.

Now, on the soil side,
if your levels come out high...

The best thing to do, again,

because we're trying to minimize exposure,
especially exposure to small children,

keep your soils covered.

You want to minimize exposure
to bare soil.

What you can do is plant turf over that.

Again, it doesn't transfer so much
into the turf,

or the plant portion of turf.

You can grow shrubs or nettles, etc.

And in between those bare areas,
add a mulch layer.

So you do want to, again,
avoid any exposure to the bare soil.

Then if your levels aren't real high,
you can always dilute that,

those levels out,

by adding a contaminant-free material.

So you can bring in a quality topsoil.

Make sure you test it to make—
that the lead and arsenic levels are low

before you add it.

You can add a quality compost.

Again, make sure
the lead and arsenic levels

are low before adding it.

And by mixing that in with that soil,

you're going to be diluting out
the concentration of lead and arsenic

in that soil.

And also, these materials will help retain
more of that lead and arsenic

so that it doesn't make its way
within the food chain.

And of course, in severe cases,
just get a raised bed,

containing materials that, again,
are free of lead and arsenic.

Always, no matter what,
if you're working in a garden,

thoroughly wash your hands
after working in the garden

and before eating any
of your vegetable crops,

just to make sure that you're not
transferring any soil bound lead to you.

And—

So you don't want to tract
a lot of this material into your house.

Always remove or rinse off your garden
shoes before entering the house.

So those are some
best management practices.

Now, what I'd like to do is just,
go through two examples here and—

ah, I'm doing okay on time—

That we—that I've encountered
through the last year.

So if you look at the first example,
I'm going to look at a typical

backyard vegetable garden
in Salt Lake City.

And this home was built in 1903.

And then in the second example,

I want to talk about a garden area
where we know that

that was contaminated
with lead containing paint chips.

And in that contaminated area,
they're still growing some fruit trees,

in this case, peach and fig trees.

And there's a rhubarb patch there.

So let me go through what we found
and some of the recommendations

that I gave regarding those two scenarios.

So the first one, again,
is a typical backyard garden.

You saw this picture before.

Actually, for those of you that are
in the Salt Lake area,

this is just south
of I-80 off of 700 East.

So it's kind of on that edge as you're
approaching Sugar House.

So soil samples were taken throughout,
around this house.

And again, this house was built in 1903.

And, we collected some samples—

let me get my cursor here—

Right here where they have
the vegetable garden.

Now, we did collect these samples
before this garden was actually planted.

And, we found that, again,
requesting that EPA test 3050,

we found that the lead in the soil
was at 100 ppm,

and arsenic was at 7 ppm.

When I looked at those results,

it's pretty typical of what we find
in residential areas

within urban environments.

And I wasn't too concerned.

Again, even if they grew root crops,
as long as they wash those root crops...

There shouldn't be any concern
about any lead getting into their food.

So my recommendation is,

your soil is fine and there's no
restrictions on what you grow.

Now, in the front of the house,
and you can't see it here,

this was the front east corner,

we took some samples
within 20 feet of that.

And we did find that the lead levels
were slightly elevated, 200 ppm.

Still below that level of 400 ppm
that I showed you earlier.

And arsenic was above 20,
so it was about 21 ppm.

So I'm starting to get concerned here
that there could be some issues,

especially if they grew edible food crops.

So my recommendation was,
no edible food crops.

And luckily, they didn't intend
to grow any there anyhow.

And my recommendation was
to keep that soil covered,

so that it wasn't bare.

And they did have shrubs
that they were planning to grow there.

They were going to incorporate mulch
in between those shrubs,

and grow turf around that too.

So that took care of that soil
for that area.

And then the other one was that lead—

that garden that had
lead contaminated paint chips,

or contaminated
with lead containing paint chips.

So there the level was
580 parts per million

and arsenic was a little bit high,
it was around 19 ppm.

And they were concerned,
because they had some fruit trees

growing in that,
within that 20 feet area there.

And they had a rhubarb patch.

And I called back the...

gardeners or homeowners and told them,

why don't you just send me
some of your fruit tissue?

Send me some peaches and some figs
and some rhubarb stalks,

and let me analyze those
and see if you need to be concerned.

And just like I thought,

when the lead and arsenic levels came back
on the peaches and the fig fruit,

they were actually below detection.

We couldn't even pick up a signal.

And we usually find that it just
doesn't transfer up into...

especially with fruit trees,
into the actual fruit.

Now, with the rhubarb, we did pick up
some lead in the stalks,

at a level of 2.5 parts per million.

No arsenic was detected.
So that's good.

And then I started doing some
back-of-the-envelope calculations.

And I thought, well, how much would they
eat in a piece of pie or whatever?

So I determined,

I had some of the values there
for FDA levels

for how much lead you can ingest.

And I thought that if they ate
a cup of that rhubarb stalk,

I calculated they still would be
about a thousand times lower

than the FDA provisional tolerable
total intake level,

which is 75 micrograms of lead per day.

So—And that level would be 25 micrograms
for pregnant women,

and six micrograms per day
for infants and children.

So they weren't going
to eat that rhubarb anyway,

and they were going to put the patch
in a different area,

where there was no contamination
from lead chips.

So, those were two typical scenarios
that I often see.

There's one I'm just going to mention.

There was a homeowner
that had bought a property.

Had some—
on that property,

they found out that
they had some old trucks

that were leaking gasoline into the soil.

And there, the levels total arsenic—

lead levels were over a thousand.

But again, the concern was that
the bioavailable levels were high.

So that was a scenario
that you don't see too often,

but it was one
where we actually called

the State Department
of Environmental Quality.

And they just put a cement slab over it.

So there was no exposure at all.

Anyway,
let me just summarize the talk here.

So if you're at all concerned
about lead and arsenic contamination,

get yourself tested and use that
EPA 3050 Total Elemental Composition.

And again, the levels
that I presented here,

where we start getting concerned,

are if your lead levels exceed 400 ppm,

and your arsenic levels exceed 20 ppm.

Now, I just want to point out, too,
that arsenic level may change

as we start getting more data
from our survey.

Again, avoid growing root crops
and leafy greens

in contaminated soils.

Follow best management practices.

In other words,
you want to cover your soil.

Dilute that soil,

if you do have lead and arsenic
contamination issues,

or use raised beds in severe cases.

Always wash your hands
and vegetables before eating,

and rinse your soil from shoes
before entering the house.

If you're still concerned,
I recommend,

and you have
vegetables that you collected,

have those analyzed for trace metals,

and you'll have a better idea
of what's going on there.

Okay.
I think—

let me just—
I think that's it.