Questions from the Master Gardener Hort Line
Volunteers
for the Philadelphia Master Gardener Hot Line have researched and answered some interesting questions.
If
you have a question about gardening, call us at 215 314 8711 or send an email
to philadelphiamg@psu.edu
Lead Contamination: Is My Garden Soil Safe?
By Pat Vance
Beginning on June 18 of this year, the Philadelphia Inquirer
ran a series of articles on residential land contaminated with lead. The first
piece was titled “Toxic City: Tainted Soil” and written by Wendy Ruderman,
Barbara Laker, and Dylan Pudell. Here is the link to the stories: (http://www.philly.com/philly/news/special_packages/toxic-city)
These articles prompted a couple of questions to the Hort Line from people who
wanted to know if their garden soil was safe.
Philadelphia’s
Industrial Past
The Inquirer article points out that Philadelphia was home
to many lead smelters in the past. The smelters are gone and there are now homes
on many of the sites. The surface lead level in some of these areas is
elevated. Additionally, when builders dig out foundations and dump the soil,
the contaminated soil and dust can fill the air and settle on neighborhood yards.
The authors focused on Kensington, Fishtown and Port
Richmond. They conducted a survey of that area and found that 75% of samples
contained lead levels in excess of the EPA recommendation of 400 parts per million
(ppm). Some were almost 25 times that level. Differing opinions are strongly
held on the health significance of lead in soil, as opposed to the clear threat
of paint chips and water, but it’s easy to understand why people are concerned.
Lead poisoning is a serious health concern and children are especially
vulnerable.
The Centers for Disease Control and Prevention publishes information
on the health risks of lead
exposure at this site: https://www.cdc.gov/nceh/lead/
Previous Land Use in
Your Area
One of the first steps you can take to calculate your garden’s
risk is to review the site history for your property. This may help determine if
there was industrial use in the area. Greater Philadelphia GeoHistory Resources
provides interactive online maps of land use going back to the 17th century in
at least some areas. The links for "Industrial Site Surveys" and "Land
Use/Zoning/Development" have helpful information. I didn't find a way to
search by address, but you can move the maps around and zoom in and out. The
link is: https://www.philageohistory.org/geohistory/.
Also, the Inquirer article includes a map showing relative
risk of lead contamination in the city. Here is the link: http://www.philly.com/philly/news/special_packages/Philadelphia_lead_risk_map.html
Don’t Guess: Soil
Test!
If you have any concerns, you can have your soil tested
through Penn State University (PSU). The Penn State Extension Philadelphia
Office is located at 675
Sansom St, Philadelphia, PA 19106, and the phone number is 215-471-2200. 
Anna Herman, PSU Extension Master Gardener Coordinator, is
collecting soil samples to be tested for free by the EPA. You can drop off a
soil sample at the office. Several times a year, Anna will send them to be
analyzed. The current estimated schedule is Nov 15, April 15, May 15 and July
15. Results typically return a couple of weeks after Anna delivers the samples.
If you want a test result in under two weeks, PSU Extension
Agricultural Analysis Services Lab will test for heavy metals in soil samples
if you check off “environmental soil testing” on their form. You can pick up a
kit from the office. The cost is $27 for a test for lead. The price is $65 for
a heavy metal panel that includes lead, copper, cadmium, nickel, chromium, and
zinc. All of these metals plus arsenic, mercury, molybdenum and selenium is $160.
(It is $10 if you only want soil fertility information)
It’s
best to call ahead for instructions and to be sure someone will be there when
you arrive.
The Inquirer article also listed several agencies that test
soil. The link to that list is:
Interpreting Test
Results
Penn State Extension has a publication that specifically
discusses lead in residential soils. Here is the link: https://extension.psu.edu/lead-in-residential-soils-sources-testing-and-reducing-exposure
This publication ranks lead levels as follows:
Soil Lead Level
(Total Sorbed Lead Test) |
Level of Lead
Contamination
mg/kg or ppm |
Less
than 150
|
None
to very low
|
From
150 to 400
|
Low
|
From
400 to 1,000
|
Medium
|
From
1,000 to 2,000
|
High
|
Greater
than 2,000
|
Very
high
|
The EPA puts the safe level at 400 ppm, even in areas where
children play.
The health effects of lead in soil have not been studied as extensively
as the effects of lead in paint and water, and there is some disagreement
between agencies and experts.
Handling Lead
Contamination in Your Garden
For the following sections, go to these links for more
specific advice and information:
http://www.eldcacag.org/wp-content/uploads/2015/11/Penn-State-Extension-Gardening-from-the-ground-up.pdf
http://www.eldcacag.org/wp-content/uploads/2015/11/Penn-State-Extension-Gardening-from-the-ground-up.pdf
Growing Food Plants
in Soil with Elevated Lead Levels
As a rule, plants do not take up lead very well. Fruiting
plants such as tomatoes are the least likely, and leafy plants such as lettuce
are the most likely to take up very small amounts when grown in contaminated
soil.
However, the soil itself can be hazardous. Lead is harmful
if ingested or inhaled. Lead can cling tightly to soil and produce grown in
contaminated soil must be washed very thoroughly before eating, especially root
crops. It is recommended to peel all root vegetables.
Gardeners also need to be careful not to bring soil into the
home on gloves and clothing. Wash hands and exposed skin thoroughly.
Raised Beds
You can prevent plant contamination by using raised beds
filled with uncontaminated soil. Cover the ground with plastic sheeting or some
other barrier and then construct and fill the raised beds.
Non-Produce gardens
Covering the contaminated soil with sod will help lower your
exposure. In beds for ornamental plants, shrubs, and trees, thick layers of uncontaminated
soil and mulch is recommended. Again,
use more caution in areas that children will use.
Removing Lead-Contaminated
Soil
It is possible to have the soil removed and replaced, but
this is very costly and difficult, and is often prohibitive for the average homeowner.
New Contamination
As the Inquirer article points out, new construction may
throw lead dust into the air, allowing it to settle on neighborhood yards. Roadways
can also be sources of toxins that can end up in the soil. Try to reduce
contact with soil within several feet of a busy road. Place low-maintenance
ornamental plants close together and apply mulch. Plant your food gardens as
far away from roads and construction as possible. Planting a windbreak between
the road and the garden will help reduce the amount of wind-blown contaminants.
Ending on a positive
note
For most of you, your soil is safe. As we always say: don’t
guess, soil test! If you do find you have elevated lead levels, there are a
number of steps you can take to assure your safety, and the safety of your families.
No comments:
Post a Comment