Birdies beds are made from Aluzinc galvanized steel and then further powder-coated with non-toxic paint. Neither the paint nor the metal itself will leach anything harmful into your soil and the beds are safe to grow in!
If you'd like to read a bit more, I've prepared an in-depth article covering the safety in more detail here: https://www.epicgardening.com/galvanized-steel-garden-beds-safe/
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