Welcome to the Bunnings Workshop community @huluman. It's fantastic to have you join us and many thanks for your question.
150 x 25mm 2.4M Rough Sawn Treated Pine has a CCA treatment and is generally recognised as not suitable for building vegetables and herb planter boxes. A solution would be to use our Sienna range of sleepers as they have an alternative treatment to CCA and are safe for edible crops.
Please let me know if you need further assistance or had questions.