- Contaminants from the roadway may affect consumables, therefore vegetable gardening is not encouraged.
Just how contaminated boulevards can be would be interesting to know. Lead is the contamination most often mentioned. In 1990 lead in gasoline was banned in Canada, so there could be some residual lead contamination along the roads with heavy traffic prior to 1990.
There are other particulates in the air from vehicle exhaust and from industry. With our recent snowfalls not melting for a long time, the deposit of particulates from the air is easy to see. Snow piles get particularly grey near busy arteries. I do not know how much danger these particulates in the air pose for growing vegetables.
Plants vary in what contaminants they take up. Here are some sources of further information:
"What You Should Know about Lead in Soil" published by the Ontario Ministry of the Environment
"Home Gardening in Lead-Contaminated Soil" published as a Niagara Region Public Health Fact Sheet, Fall 2005
Lead in Urban-grown Vegetables; research done at Cornell University using soils from contaminated areas of New York City
Uptake of heavy metals by vegetable plants grown on contaminated soil and their bioavailability in the human gastrointestinal tract