Natural Life Magazine

Old wooden pallets can be contaminated with bacteria  or chemicals.

Ask Natural Life:
Do You Know Where Your Wood Pallet Has Been?
by Wendy Priesnitz

Q: I’m seeing a huge number of cool-looking projects on the Internet using wooden shipping pallets, from flooring to beds (including baby cribs) and tables to garden furniture and planters...even cutting boards. At first, I thought it was a great way to “upcycle” and they seem to be a wonderful source of found wood. But as I think about it, I’m wondering if the wood is treated in any way that could be harmful. Could you look into this please?

A: You’re right to be extremely cautious about what is being brought inside when a pallet is rescued from a dumpster or a pile behind a store or warehouse. We receive shipments of magazines and books on pallets on a regular basis, and we normally give them back to the shipping company for re-use the next time they make a delivery. Some of them are in good shape, but some of them are beyond being ready to be retired. I would not want to use those dirty, broken bits of wood in my home.

The cheapest pallets – the ones that you’ll often find discarded as trash – are made of softwood and may contain pressboard or other low-grade engineered wood (typically as the spacers between two layers of slats). Hardwood pallets – along with their plastic counterparts – are costlier, and often require a deposit so they are returned to the sender for re-use.

No matter what the pallet is made of, its life is probably an adventurous one. They are loaded with products, then put into trucks, transported to their destination, and unloaded. Then, if they’re still in one piece, the cycle begins again, making it difficult to know where the pallet has been. We do know that pallets often spend some time outdoors in spite of industry “best practice” recommendations – think back alleys – where they are inevitably exposed to water (which can quickly breed mold), rodents, insects, bird droppings, and who knows what else. (And, of course, those are the pallets that often end up in garages and workshops, destined for various craft projects.)

In spite of the hygienic properties of wood, the pallets harbor whatever pathogens they’re exposed to and can, as a result, carry dangerously high bacteria counts. In 2010, after an outbreak of E. coli on romaine lettuce, the Washington-based National Consumers League (NCL) called for stricter safety standards for the pallets used to transport food throughout the United States. NCL had an independent lab test pallets for food borne pathogens and found that ten percent of them tested positive for E.coli and almost three percent tested positive for Listeria, one of the most virulent food borne pathogens with a twenty to thirty percent rate of mortality. They also found high aerobic plate counts, which reflect unsanitary conditions and where bacteria could easily grow, on approximately one third of the wood pallets.
Be extremely cautious about what is being brought inside when a pallet is rescued from a dumpster or a pile behind a store or warehouse. Does it harbor bugs, bacteria, or chemicals?

Those findings were replicated by Pace Analytical testing lab (on behalf of iGPS, an international plastic pallet rental service), which echoed the NCL’s call for stronger standards for shipping pallets.

To add to the potential bacterial danger, products that are shipped on pallets – including imported produce and other materials – are routinely fumigated with toxic pesticides, sometimes in order to be allowed into their destination country.

Pallets not used to transport food can also be problematic. Various fungicides such as propiconazole (a suspected carcinogen) are common treatments. A few years ago, McNeil Consumer Healthcare was involved in two product recalls attributed to contamination from treated pallets. A Tylenol recall happened after consumers complained of a moldy, musty, mildew-like odor that was associated with nausea, stomach pain, vomiting, and diarrhea. The odor was attributed to wood pallets that had been treated with a mold control chemical called “tribromophenol” or TBP. Later, the diabetes drug Glumetza was also recalled due to TBP contamination, thought to have originated with pallets used to transport the product’s bottles to its contract manufacturer in Puerto Rico. TBP is not sanctioned in many countries, including the USA (although other mold treatments are).

The reverse can also happen, and harmful materials or chemicals that are being transported on a pallet may spill onto the pallet wood, be absorbed, and off-gas or otherwise affect the person reusing the wood or living with the end product.

The millions of pallets that contain pressed wood are also dangerous for repurposing because most engineered wood contains formaldehyde, which is a known carcinogen that eco- and health-conscious people try to avoid. It can off-gas from the pallets for quite some time after manufacture.

The millions of pallets that contain pressed wood are also dangerous for repurposing because most engineered wood contains formaldehyde, which is a known carcinogen that eco- and health-conscious people try to avoid. It can off-gas from the pallets for quite some time after manufacture.
One of the big issues with the use of wooden pallets has been their ability to give a ride to invasive pests. For instance, they are blamed for introducing into Canada the destructive citrus long-horned beetle, the Asian long-horned beetle, and the emerald ash borer. In an attempt to stop this migration of pests, many countries have signed on to a set of International Standards for Phyto-sanitary Measures (ISPM 15) under the International Plant Protection Convention (IPPC). Since 2006, most pallets shipped across national borders must be made of materials that are incapable of being a carrier of invasive species of insects and plant diseases.

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 effects 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 and therefore prone to being picked up for reuse.

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.

Aside from possible chemical contamination, wood pallets tend to have a relatively low fire flash point, making them combust quite easily. That is why many people like to burn them in bonfires and even stoves (also a bad idea if they’re treated with chemicals). But it also makes them a questionable material from a fire safety perspective for building furniture to be used indoors.

They will be recycled even if you don’t use them. In order to keep them out of landfills, pallets that are beyond repair are increasingly being ground up and used for garden mulch, stove pellets, and animal bedding, or to produce particleboard.

If you can’t resist the free wood, restrict yourself to pallets stamped with “H.” Even so, you still can’t know for sure that the wood has not been tampered with somewhere in its multiple-use life, or contaminated with fungicides, pesticides, other chemicals, mold, or bacteria. Pallets might be okay for outdoor projects like potting benches, flower boxes, and fencing – and some people use them to make compost bins. But my caution about leaching chemicals should be considered when using them to grow food or even to hold compost.

And finally, given the potential risks, I don’t think pallets should ever be used for children’s items or those that will be in contact with food, or for furniture used in a bedroom.

Wendy Priesnitz is Natural Life Magazine’s editor, a journalist with over 40 years of experience, and the author of 13 books. 


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