My son wants to use wooden pallets for a vegetable garden. Is the wood in these pallets safe for contact with food crops?
Pallets (especially those used in international shipping) are very likely to be treated, since wood packaging must now comply with the International Plant Protection Convention’s International Standards for Phytosanitary Measures Guidelines for Regulating Wood Packaging Material in International Trade (ISPM 15). Here is more information from an article by Wendy Priesnitz, editor of Natural Life Magazine:
“Pallets made of raw, untreated wood are not compliant with ISPM 15. To be compliant, they must be debarked and either heat-treated to certain specifications or fumigated with methyl bromide, which affects the central nervous and respiratory systems. Heat-treated pallets bear the initials HT (or sometimes KD for kiln dried) near the IPPC logo. Pallets treated with methyl bromide bear the initials MB. In 2010, a phase-out of the use of methyl bromide began because it is an ozone depleting substance under the Montreal Protocol. However, many pre-2010 pallets are still around and, in fact, are likely to be the ones nearing the end of their useful lives as pallets.
“Older pallets could also have been pressure-treated with chromated copper arsenate (CCA), which has been phased out for many residential uses. The arsenic in CCA-treated wood can be dislodged so that direct contact with wood can lead to exposure, thought to be a problem especially for children, and it can leach into ground water. A 2008 Australian study found that one percent of pallets tested contained CCA. Copper-treated wood varies in color from a very light green to an intense green color, depending upon the amount of chemical impregnated into the wood. However, it ages to a silver color, as does untreated wood, so color is not a reliable indicator, especially with older wood.”
A related question about reusing wooden pallets appeared in the online journal Grist, and their columnist raised the issue of chemical treatment as well as the possibility of the wood having absorbed dangerous bacteria, so I think it’s wise not to use wooden pallets for growing food.
If you want to recycle the pallets, there are places in King County which will accept wooden pallets for reuse, listed on the King County Solid Waste website What Do I Do With…. ?. If you know where the pallets came from, you might ask that business if they will let you return them.