[Greenbuilding] Roofing material for Rain Harvesting

[Arnie Katz]

I was recently working on a prototype extra high raised bed, using salvaged
galvanized 5V roofing. A friend suggested that might not be such a good
idea, since, along with the zinc, cadmium is used in the galvanized
coating. A bit of research verified that, yes, galvanized steel typically
has cadmium in it; cadmium is one of the heavy metals that accumulates in
our bodies over a lifetime, relatively small amounts can have significant
negative health impacts; cadmium will leach out of the material into the
soil; and vegetable plants do take it up and are a source of cadmium in
people who then eat those vegetables.
That was enough for me to abandon the experiment and move to a different
design for enabling my wife, who is having difficulty bending and stooping,
to continue gardening.
Perhaps someone on the list knows a lot more about this? It does make me
question whether galvanized roofing is suitable for rainwater collection if
the water is to be used for food crops.
Arnie Katz
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