Here's a summary of the history of peoples' opinions of the safety of growing in old tires: "they're safe" "they're not safe" "they're safe" "they're not safe" "well maybe they are safe".
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Current thinking seems to be that perhaps they do not actually leach meaningful amounts of harmful stuff into garden soil or veggies.
However to me the evidence on which these conclusions are based (what I've been able to find anyhow) is not directly comparable to what people do in their gardens. My opinion: probabably not a suicidal way to garden or anything like that, but I ain't doing it myself. Very old, weathered tires are probably actually *riskier* than relatively newer tires, btw.
If you are buying bulk topsoil, ask a buncha questions first. Where topsoil comes from is the stuff that is sc-raped off of land that's being built over for houses, shopping malls etcetera, and the history of that land can vary a LOT. While most commercially-obtained topsoil is not too bad, some of it is
tremendously weedy, and if you get stuff from land that was a cornfield last year it can be full of so many herbicides that not much will grow in it. Uncommon but it does happen.
Personally I would buy triple mix rather than topsoil, if I had to buy soil. It's not without variation or risk either, but arguably less so than topsoil, and arguably better to grow stuff in.
Pat
