HUNTING DOWN HIDDEN DANGERS AND HEALTH BENEFITS OF URBAN FRUITS
Forgotten
trees from long lost orchards and 20th-century city landscaping are being
rediscovered in urban areas, and their fruits are proving not only largely free
of urban pollutants, but more nutritious than their retail counterparts.
Scientists at
Wellesley College have joined forces with the League of Urban Canners (LUrC),
based in Cambridge/Somerville and greater Boston area, to collect and
eventually analyze 166 samples of apples, peaches, cherries and other urban
fruits and herbs, collected from remnants of historical farms, urban parkland,
and residential properties. The efforts grew out of concern for a LUrC member
who was found to have high levels of lead in their blood. Members of LUrC
wanted to make sure that the urban fruits they were harvesting and processing
were not harboring toxic metals.
"This is a
story with a good ending: not much lead in these urban harvested fruit,"
said Wellesley geosciences and environmental studies professor Dan Brabander,
who has previously studied lead exposure risk in urban gardens and in areas
impacted by historical mining activities.
The LUrC study
investigated the concentrations of lead in urban fruits when they were peeled
and unpeeled as well as washed and unwashed. That was intended to distinguish
whether the fruits were taking up lead internally or being contaminated by dry
deposition from the air or from soil dust.
"We found
there was no difference between these variables," said Ciaran Gallagher,
an undergraduate researcher majoring in Environmental Chemistry at Wellesley
College, who will be presenting the research on Monday, Nov. 2 at the annual
meeting of the Geological Society of America in Baltimore. Gallagher will be
co-presenting with geoscience undergraduates Hannah Oettgen and Disha Okhai.
The researchers
also looked at arsenic in the fruits, because in older orchards farmers
commonly used lead arsenate as a pesticide. "So we are keeping an eye on
places where this pesticide might have been historically applied." To date
the researchers have not found evidence of use in the LUrC samples.
For the lead
analysis, fourteen urban and eight commercial fruit samples were dried in a
fruit dehydrator to mimic methods used by LUrC members in their home kitchens,
and analyzed for trace elements. Gallagher and her colleagues found that the
lead concentrations in urban apples ranged from 0.5 to 1.2 ug/g (dry weight
basis). They then looked at the estimated consumption of the fruit to model how
much lead the urban fruit eaters were being exposed to. The resulting finding
suggest that eating urban fruit is not a significant source of lead exposure,
when compared to the EPA regulated benchmark for lead in drinking water.
In addition to
lead and arsenic, they also looked into the nutritional value of urban fruit.
They compared micronutrient levels with those in commercially grown fruits and
found that calcium concentrations in urban apples and peaches are more than 2.5
times those in their commercial counterparts. Concentrations of calcium and
iron were higher in urban fruits for every fruit type tested, and manganese, zinc,
magnesium, and potassium concentrations were higher in certain urban fruit
types. On average, urban fruit contains a wider range of micronutrients than
its commercial counterparts.
"When they
grow in a commercial setting the soils can become quite impoverished,"
Brabander explained. "In the urban setting where the trees sampled tend to
be older perhaps they are able to shuttle micronutrients from a wider and more
diverse range of horizons." Planned future soil coring work into urban soils
will try to figure out the mechanism of nutrient transfer in this unique
setting.
"That's
not to say that all urban produce is safe to eat, however, because local
conditions vary and antique fruit trees are found in some very unexpected --
and sometimes very polluted places, like along major roadways," said
Brabander.
"By
working with the Wellesley researchers the LUrC members are able to get a much
broader, clearer look at the health benefits and any potential health threats
from urban fruit than they ever could have if they had randomly spot checked
fruits," said Brabander.
"The
citizen-science component to both study initiation and sampling is so central
to how this project has been conceived and executed to date," said
Gallagher. "Simply stated, without the League of Urban Canners, this
project would not have been possible."
Brabander
concludes, "The intersection of urban geohealth and citizen science is an
emerging research paradigm for prioritizing projects that have immediate
implications for designing best practices that promote a wide expression of
safe and sustainable urban agriculture."
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