Interesting question. I did some research recently and found that the people who say tires are safe equal the number of people who say they are NOT safe just about 50-50! I was researching planting potatoes in them. The one site said that the ground tires (now used to make mulch) weren't good because grinding up the tires allowed the bad stuff to leech out into the soil where whole tires have anything that's a potential problem sealed in. Not sure if that's true, but that's what I read!

I know I've seen a lot of tire retaining walls in pics in various places...maybe you could contact a state office that deals with pollution or water and ask them. I'd like to hear what you find out!

All I can tell you is that they use old tires as retaining walls on the Chesapeake Bay....not sure who you would need to call to get info though.

They also grind them up & use them to make new roads. Not sure I would want anything like that near my food/water.
A lot of the applications we don't get to have a choice...OUR government does it for us...but if I get to choose...NO, I wouldn't use them.
Some schools where they used them for play areas have removed that chunked rubber...to many instances of kids getting sick...it increased after it had been put down!

I saw on tv how they had been used to (try to) rebuild reefs off the Florida coast, and it is a terrible mess. SEa life wouldn't grow on them. I would be concerned about growing food in them, tho not flowers so much.
Kathy

Here is a link that might be useful: Story about tires off Florida

No no. We would not be using them for planting anything & they would be used as whole tires. Not cut up. It would be used as a wall retainer. Thank you for the replies though.