[Community_garden] Zinc and Cadmium and Heavy Metals

[Karen Jones]

Hi All,  I could see this coming from the bio-solids conversations, which I really enjoyed. (Too bad someone did not have the time to compile those informative convos). I'm not a toxicologist but we tested our garden for Nickle, Manganese and Lead and did a bit of research on heavy metals and here is what I found out.  No levels of heavy metals are safe. Heavy metals are not biologically active and they tend to accumulate in tissues until you have physiological stress and wow, you are wandering around wondering where you live, seeing double etc. Even sub-clinical levels of heavy metals can contribute to things that look like Attention Deficit Disorder etc. But, The organs of the plant that sequester the heavy metals are leaves and roots. If you know your plant parts you can eat fairly safely. Potatoes are modified stems, safe to eat, if washed well, rhurbarb is the petiole not the leaf, safe to eat, all fruits (beans, corn, squashes, tomatoes, peas etc. are safe,they are fruits)  and other things you think of as real fruits (strawberries, apples, plums etc).  Any leafs (spinach,lettuce, cabbage) are dodgy.  However, most heavy metals are breathed in as dust, so always wear gloves and always wash anything that you eat from the garden. Also, bad news if you live in a house that is older than 40 years, you have a heavy metal halo around your house. Heavy metals are persistant. Children under 2 should not be allowed in a garden because of the high incidence of pica (soil eating). Last year 59 community gardens were shut down in Montreal, toxic with heavy metals. This just happened to coincide with needing room to build houses and it just became expedient to shut them down then. There are lots of toxic gardens in Winnipeg. They just don't need the land for houses yet. When gardening you have to know what you are doing and be careful. Land can be rehabilitated through growing things like sunflowers and canola. But then when these crops are taken off the soil they have to be treated as toxins. I totally agree with Mike no heavy metals are safe. They bioaccumulate, they are not biologically active and  every little bit accumulates.  Keep those tires out of your garden.  Heavy metals and gardens do not mix. Garden safely!  Karen