Railroad cross ties
How long until they are safe for raised vegetable beds?
Ector County Texas
Thank you for your question. The EPA currently has complete restrictions on the use of creosote-treated wood in gardens. These laws are being reviewed (https://www.epa.gov/ingredients-used-pesticide-products/creosote) While that review process is progressing, there remains a ban on using treated wood in crop containers (https://www.epa.gov/ingredients-used-pesticide-products/overview-wood-preservative-chemicals). You should interpret this as an ongoing ban, and, therefore NEVER safe for raised vegetable beds. Avoid them completely, and dispose of them in the manner advised in the prior publication.
Railroad ties can be safely re-purposed for use in garden construction.
According to an AgriLife publication on building raised beds, "there is some controversy about using treated landscape timbers, but studies have shown that any compounds that leach out are well within safe levels established by the EPA, both in growing media and in harvested produce."
Other studies confirm that even the primary use and exposure to creosote in the manufacture of treated lumber does not increase the risk of cancer. Research has also demonstrated that plants do not effectively absorb creosote. In fact, creosote is often tied up and broken down in both soil and water by naturally occurring microorganisms which use it as a source of food.
Penn State apparently takes a different approach: https://extension.psu.edu/environmental-soil-issues-garden-use-of-treated-lumber