Using galvanized wire mesh for supporting tomatoes is suggested on your website. I know that working with galvanized wire entails risks — one roll of standard galvanized wire I bought recommended washing hands before eating and avoiding repeated exposure — so why would this material be safe for growing food, especially if the food comes in contact with the wire?
People have been drinking water from galvanized steel pipes, galvanized “tinware,” etc., for years. Galvanized steel isn’t appropriate for preparing acidic foods or beverages (especially brewing), and it isn’t the best material for vessels designed to serve up your favorite drinks.
From the CRC Handbook of Chemistry and Physics: “Zinc poisoning is mostly accidental from the intake of pesticides, inadvertent therapeutic use of heavy doses of zinc salts (oral supplements), or drinking of acidic juices or brews made in galvanized iron utensils.”
The only real risk with galvanized steel fencing is from breathing fumes while cutting, burning or welding, or from breathing dust from grinding, etc. The warning label on the wire is the brainchild of some litigation department. Zinc toxicity is most generally caused by inhalation, not ingestion. And in the case of the wire fencing, the only risk is in the small amount of zinc dust that might be present. I would be much more worried about taking a zinc supplement than handling wire on a weekly basis.
So, I cannot think of any reason to worry about handling galvanized wire fencing of any kind, or from swimming in galvanized steel stock tanks, or from drinking Ogallala Aquifer water from galvanized steel pipes emanating from windmill-powered galvanized reciprocating pumps, all while leaning on a galvanized steel windmill tower. But, if that galvanized metal is burning, I will definitely avoid the yellowish-white, zinc-laden smoke. And if that galvanized steel is sitting in a pickling acid, I will definitely avoid drinking or swimming in the effluent.
I most definitely wouldn’t worry about galvanized wire for my tomato cages.