Garden soils contaminated with lead can pose a health risk
if vegetables and fruits from the garden are consumed.
We dont usually think
of our gardens as dangerous or toxic, but unfortunately some garden
soils do contain toxic levels of lead. We are familiar with the
danger of lead in paint. Chipping or peeling paint around older
structures will raise the lead level in the soils directly adjacent
to the building. Even today when an old building is demolished,
the soil can still become contaminated with lead from lead paint.
In the 1950s, restrictions were initially placed on lead in
paint. Today, the lead content in paints has been reduced, however
paint companies are allowed to mix up to 0.05% lead in paints. The
lead content of commercial and artists paints are not restricted.
Lead use has been reduced significantly, but not entirely eliminated.
can be contaminated with lead from several other sourcesindustrial
sites, industrial sludge with heavy metals, until recently from
auto emissions, old lead plumbing pipes or even old orchard sites
in production when lead arsenate was in use. From a gardeners
viewpoint, lead contamination is forever. Without remedial action,
soil lead levels may never return to normal.
do not require lead in our diet or environment. At very low levels
that naturally occur in soils (15-40 ppm), no detrimental health
effects have been noted. The effects of lead contamination can raise
the lead level in the body and thus poses a substantial health risk.
Young children under the age of six and pregnant women are at the
greatest risk. The risk of lead poisoning is disconcerting to families
since it is largely unseen. Physical symptoms, including headache
and nausea, are frequently not present. Children exposed to lead
tend to have lower IQs and may experience learning disabilities
and behavioral disorders.
Testing for lead will help to evaluate
the lead hazard level. See our GreenShare Factsheet on Soil
for information on submitting soil samples. Ultimately, the risk
to you and your family is based on your exposure. Both private
some university soil test labs can determine lead levels in soil.
Work at the University of Massachusetts soil testing lab and the
experiences of the Suffolk County Massachusetts Lead Task Force
has resulted in a classification system for soil lead levels.
increased soil lead level implies a greater hazard. The Massachusetts
recommendations for limiting exposure to lead are based on the
results of soil lead levels. No legal regulations for soil lead
levels are in effect, and no tests have linked health effects
high lead soil levels.
fact, the classification system is a relative scale, designed to
give the gardener an index of how much lead is in the soil and how
to alter his gardening practices to reduce his exposure to the soil
lead. When laboratories analyze lead in soil, the results will be
returned listing the parts per million (ppm) of lead from either
an extracted or total lead test. The values in Table 1 will help
you to understand your test results:
Table 1. Soil Lead Levels
Relative Soil Lead Levels
Extracted Lead (ppm)
Total Lead (ppm)
samples should be taken from several areas to determine the location
of the contamination. The greatest lead concentration is in the
top one to two inches of the soil. Childrens play areas
or vegetable gardens should be sampled separately. Avoid mixing
sites into one sample. Sample high-risk areas to locate potential
Gardeners can use several methods to reduce the risk
of lead poisoning from lead contaminated soils. Fruit and vegetable
be located away from old painted buildings, heavy traffic and sites
where sludge with heavy metals was applied. Vegetables and fruits
can accumulate lead in their leafy green tissues, although lead
accumulation will be lower in fruits. In high-risk lead areas,
crops such as tomatoes, eggplants, peppers, squash, melons and
cucumbers rather than leafy greens such as lettuce, chard, collards
Crops such as carrots, radishes, turnips, onions and potatoes can
accumulate lead and should not be planted in heavily contaminated
ingestion of lead from contaminated soils is a risk. Soil clinging
to the leaves, fruits or roots of crops can be directly ingested.
Wash and peel fruits and vegetables to reduce this risk. A 1% vinegar
solution (2.5 tablespoons per gallon) or soapy water is an effective
way to remove soil. Discard the outer wrapper leaves of greens before
washing. Wash off excess dirt from root crops outside the home,
preferably at an outside hose bib to prevent bringing contaminated
soil into the home.
amount of lead absorbed by plants is affected by the pH, organic
matter and phosphorus content of the soil. To reduce lead uptake
by plants, lime the soil to a pH of 6.5 to 7.0. Add organic matter
such as compost, leaf mold or grass clippings to the gardening site.
Add phosphorus to the soil as recommended by a soil test.
reduce the risk of bringing lead contaminated soil into the home,
rinse and launder gardening clothing promptly. Young children, in
particular, may directly ingest soil when playing. If possible do
not allow children to play in contaminated soils. Hygiene is important,
although understandably difficult, with young children. Frequent
hand washing and rinsing outside toys will reduce the amount of
soil ingested. Wash hands before eating meals or snacks. Do not
let children eat soil or put their hands in their mouths. Mulch
play areas with wood chips or other soft materials to reduce soil
dust. Build a plastic-lined sand box for a clean area to play. Parents
of children under six living in areas with contaminated soils should
consult their pediatrician. A blood test to monitor lead levels
may be recommended.
heavily contaminated soils adjacent to a residence, plant trees,
shrubs or perennials and mulch the area to minimize annual tilling
and cultivation operations. When the soil lead level is over 5000
ppm total lead, the garden soil should be removed and replaced with
clean topsoil. Direct ingestion of contaminated soils and the airborne
soil dust can only be eliminated by removing the soil. Test the
new topsoil before purchasing it. Test for soluble salts, pH and
the standard nutrients (phosphorus, potassium and magnesium). Testing
for lead and other heavy metals is recommended especially if the
topsoil is from an urban area. No food crops should be grown in
a soil that is heavily contaminated. Container gardening or construction
of raised beds filled with purchased soil is an option for the avid
from Denise D. Sharp and David L. Clement, Maryland Cooperative
Extension Service, 2001