Thank you! We have a great local supply of pallets that are extremely clean. There are some pallets that may be pressure treated but because you are removing so much of surface area here, anything that was on it is likely gone. Plus, bees naturally coat the inside with a wax/ propolis combination that will seal anything that would have possibly remained. So, from our research, there seems to be no reason for concern for the use of pallets. Thanks so much for reading!