Urban Agriculture: Tonic or Toxic?

Ever since I was child, I have been mother’s little helper in the garden. Organic, fresh, vegetables were always the preference in our household. Then, with maturity came my acceptance to college and my big move to New York City. To no surprise, there is only a limited number of organic produce available in most large-scale urban environments, which was slightly concerning until I discovered the magical world of urban farming! Urban agriculture is changing the way people are living. It is providing people with the locally grown food that they want at a distance close to home. Although urban farming is adding more greenery to cities, my mom had a concern that the produce grown could be contaminated by the toxins of the city atmosphere. So I guess the real question is, can some of these crops be toxic?

One of the most serious constraints to a harvest in an urban setting is the contamination of soil by lead, mercury, and other heavy metals that are urbanized due to former industrial sites. Lead is usually people’s biggest concern because it can be integrated into the soil by lead-based paint when paint chips from old buildings, or by the lead produced from auto emissions. The most toxic way someone can be exposed to lead is through direct ingestion of contaminated soil or dust. In general, plants do not absorb or accumulate lead. However, in soils testing high in lead, it is possible for some lead to be taken up. Studies have shown that plants transmit a relatively low amount of many of these toxins into the fruiting parts of vegetable and fruit crops such as tomatoes, strawberries, and apples. Higher concentrations are more likely to be found in leafy vegetables like lettuce, and on the surface of root crops like carrots. That’s one reason why it’s important to thoroughly wash your vegetables!

It is also important to test your soil. Soil tests can be completed for a very cheap price by mailing your soil in to a soil testing lab, purchasing a soil test kit from your local university extension office or home improvements store, or even performing a do it yourself soil test at home. All of these methods are quick and will keep your soil healthy and at the right levels.

According to the “Farmer Education Program (PEPA) Resource Guide,” farmers can prevent post-harvest diseases and food borne illnesses by using a disinfectant in wash water. Also, chlorine in the form of a sodium hypochlorite solution, for example Clorox, or as a dry, powdered calcium hypochlorite can be used in hydro-cooling. This cools the produce immediately after harvest in order to deliver the highest quality product to the consumer.

There are also some techniques for soil remediation, or ways to reduce the level of contamination in the soil itself. This can be done either physically which generally involves the use of technology, or biologically which takes a more natural route.

The physical soil remediation process using excavation
The physical soil remediation process using excavation

is a very quick method to use which physically removes contaminated soil, usually for disposal at a landfill using heavy machinery, at a relatively high cost. Geotextiles are a synthetic blanket-like material. These are typically used after the excavation process to provide a protective barrier that is impermeable to contaminants that might migrate into the new soil. However this barrier is not foolproof because it can tear allowing contaminants to enter the soil. Soil vapor extraction involves the installation of wells and pipes in the soil, through which soil contaminants are extracted. Biological remediation is much more low-cost. Microbial remediation uses microbes to degrade contaminants into a less toxic form. Phytoremediation is the process of using plants to extract contaminants or to degrade them in the soil. This process is much longer, and not as effective since one species of plant can eliminate only one type of contaminant.

Compost remediation
Compost remediation

The method I am the most familiar with is compost remediation, which involves the addition of compost to the soil. This is cheap, and quick to do. However, it is not a true remediation technique, because contaminants generally remain intact in the soil. Compost can remove solids, oil, grease, and heavy metals from storm-water runoff, as well as destroy a large percentage of industrial volatile organic chemicals in contaminated air. The addition of compost can also be used to create a raised bed so that plant roots cannot reach any contaminated soil.

Organic foods typically cost more than conventional foods. The higher price is usually related to natural fertilizer and labor-intense pest control tactics. Regulations limit the number of pesticide products available to organic producers. Research has demonstrated that organic fruits and vegetables have smaller amounts of pesticide residue than produce that was grown conventionally. However, pesticide residue is reduced substantially by routine food handling practices such as washing, peeling and cooking. Some research has found higher levels of phenolic compounds, which play an important role in cancer prevention and treatment, as well as certain vitamins in organic produce. Other research has found no significant difference in the nutritional quality of organic and conventionally grown foods.

Although urban agriculture does have some risks, the benefits are plentiful too. There is some hesitation when it is comes to toxins integrated in produce, which is why as a consumer everyone has a careful living decision to make!


By: Sandy Beharry

These are some of the crops harvested from the NYU Urban Farm Lab
These are some of the crops harvested from the NYU Urban Farm Lab

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