I looked into this before building my beds and what I found was that most of the treated wood these days is not treated with the toxic chromium and arsenic that was used in the past. Supposedly, they are today treated with mostly non-toxic substance but I can't tell you what that is. I never went that far into it. I have difficulty believing that somehow, the trace amount of chemicals that may leach out of the treated wood are going to be transmitted into the flesh of various vegetables any more than substances contained in dog, cat, or horse feces is transmitted through the root system and into the fruit, leaf or vegetables. I suppose root crops could possibly absorb some amount through direct contact if concentrations were high enough but still, I find it hard to believe that it would absorb more than negligible amounts. Considering all the added unnatural chemicals/preservatives/dyes etc, we consume daily in our food and beverages, not to mention everything we breath, I concluded that, for me and my family at least, any chemicals in treated lumber is a non-issue vs. the benefits of eating fresh vegetables. YMMV

I haven't used it on wood yet Jean. I have, however, used it in my house and on my pets for fleas, ticks and also those nasty Palmetto bugs we get here in SWFL. My last dog has gotten a horrible case of ticks and her fur was so dense we didn't know until she, and our house, was infested. The Vet was amazed when I told him how we got rid of them. He now uses the stuff himself. It also works well as a mosquito repellant! As for the wood treatment. I watched the youtube video, which was very informative. I am sure that it is a similar formula of Cedar oil in a carrier like the repellant is. We are going to try it on some outdoor benches we picked up from an abandoned house. They are very weathered so we will clean them, use the wood treatment and then stain them. If it works well, we will then use it for our wood fence.

The old CCA Pressure Treated wood could leach out Arsenic which you could possibly pick up on your hands and if you did not properly wash them might ingest some of that Arsenic. It tool some 50 years for the researchers to discover this about the CCA PT wood before it was removed from the market so it really remains to be seen about the others. The EPA seems to think that the concerns about the Arsenic were overblown now and it is considering allowing CCA PT wood back on the market. If Pressure Treated wood is used to make raised beds the plants that grow nearest that wood need special care in handling if that PT wood leaches some of the chemicals so you know they have been washed off. Plants generally do not pick up these heavy metals since they are not needed for growth.

I thought of using cedar, but when I priced it, it was way too expensive and didn't make sense to do it. And I'm sorry to say, but if you're trying to grow as much food as you can, two 4x4 beds are not very much and I think that is a lot of money for two small beds. I have one long bed 12" high, 11ft long and 4ft wide. I have four beds 12" high, 4ft x 4ft. I made them with Pine because I had some already and didn't have to buy much more. It's actually been about 8 years since we built them and they are ready to be replaced now. Now I want to double the square footage that I can grow in. So I want to build… Two beds 12" high, 16ft long, 4ft wide Six beds 12" high, 6ft long, 4ft wide That doubles my growing space. I don't feel I need deeper beds, because vegetables are annuals and I've read somewhere recently that they don't really need 18" deep beds. 12" is just right for me and I don't mind bending and kneeling. So less wood. I priced what cedar I could find and it was going to cost me over $600. to build those beds. I called 12 lumber yards and only two had cedar and they weren't the dimensions I wanted either. Finally, one lumber yard, said he was steering people to use Eastern Hemlock rough sawn, which is very inexpensive. It is more rot resistant than Pine but less than Cedar. Estimates were 5yrs for Pine, 8-10 years for Hemlock, and 15yrs for Cedar. I priced the Hemlock and it was going to cost me $198. to build the same beds. So, if I built the hemlock and had to replace them in 10 years for another $200. It would still be $200. less than building the cedar beds, and would last me 5yrs longer.