Ups and Downs of Urban Gardening

With 50% of the world’s population now living in cities, growing food in urban gardens makes sense.  Why import food when it can be grow locally?  They not only save on fuel, but also help urban folk get closer to their food and break up the concrete jungle.  Urban gardens can range from full-blown community gardens in the city center that supply food to urban grocers, to containers on balconies that yield salad tomatoes, and anything in between.

With people beginning to be a bit more conscious about where their food comes from, urban gardening is a great way to eat local and organic food.  However, just because food is grown in your backyard, doesn’t necessarily mean it is guaranteed to be safe.

Recent research shows that urban soil may be contaminated with high levels of lead.  Over-exposure to lead can lead to lead poisoning, which may cause reproductive problems and possibly organ failure.  It is particularly harmful to children because it disrupts nervous system development.

The research isn’t at all surprising when I think about it, but it had never occurred to me before.  When I think of Philadelphia (my former urban locale), I now see that lead must be everywhere.  All of the buildings are quite old, probably painted with lead-based paint.  The streets are busy.  Plus, there is an airport and a huge petrochemical refinery just outside of center city.

The research shows that gardens near busy streets, run-down painted buildings or older industrial facilities have more of a risk of being contaminated, so if you plant near one of these risk factors, you may want to consider taking these extra steps:

Raised beds with new soil are a good way to protect your urban garden from lead (much like the photo).  Be sure to cover the old soil before putting the new soil on top.  A high-phosphate fertilizer can also help further immobilize any lead present.  Produce from all urban gardens should be washed carefully.

The problem though is that lead may not just come from the soil; it may also come from above – from blowing paint chips and pollution from cars and industry.  If this is the case, the soil will eventually become contaminated even if it is new.

What is a little unnerving is that you can’t tell just by looking at it.  Soil can be tested for lead content, but home kits are not recognized as being all that reliable.  If you wish to plant in a possibly high-risk area, you can get information about certified lead testing centers by calling 1-800-424-LEAD.

If you do decide to get your soil tested, here are the recommendations on lead levels and gardening from the new research:

Anything below 200 ppm (parts per million) is generally safe and can be used for planting.  A high-phosphate fertilizer can help further immobilize any lead present.

For soil with lead levels from 200 to 500 ppm, measures can be taken to reduce the plants’ exposure to lead, such as covering soil and planting in raised beds.

For levels above 500 ppm, gardeners beware.  The lead may be coming from the soil as well as from the air.  It is not recommended to plant root vegetables or leafy greens; however, taller fruit plants are safer options.


Photo credit:

Flickr creative commons license by Gabriel Kamener

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