Pallets are either heat-treated (heated to a high temperature in kilns to seal the wood) or treated with methyl bromide — a toxic pesticide that has been linked to human health problems and ozone layer depletion. When sourcing used pallets, look for wood bearing the IPPC seal and an “HT” stamp, designating it was heat-treated rather than sealed with toxic pesticides.
Look for the IPPC stamp on the side of the wood to determine how it was treated. Pallets marked with an “HT” were heat-treated and did not come into contact with chemicals during the treating process. Avoid unmarked pallets or those stamped with an “MB” for methyl bromide.
You may have read an article or two online that advises cleaning used pallets with hot soapy water, vinegar, or a bleach solution to vanquish bacteria and other contaminants, but these methods aren’t always effective.
Wood is very porous, and you’re really never sure if you’ve gotten everything out of there. The same thing with sealing or painting it. I don’t think the effectiveness of that has been totally proven yet, either.
To avoid coming in contact with contaminated wood, be sure you can confirm the origin and use of a pallet before repurposing it at home. Pallets used locally for innocuous materials such as textiles or paper products are your best bet, but you still want to make sure these are from a trusted source.