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Wood Pallet & Pharmaceutical Industries Working Together
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part 2


Wood Pallet and pharmaceutical industries working together



By David Ulrich, Jorgelina González and Edgar Deomano

This is the second of four articles in a series meant to further the conversation and cooperative efforts between the wood packaging and the pharmaceutical industries. This installment focuses on controls that are needed at the mill and the pallet manufacturing site in order to lower the risk of taints from wood pallets. It will also help educate pharmaceutical manufacturers on the types of wood and pallets so as to increase their knowledge of the pallet industry.


The plant kingdom is subdivided into major divisions. The division Spermatophyta is separated into two broad groups based on seed type: the gymnosperms, which have exposed seeds, and the angiosperms, whose seeds are encapsulated.

Gymnosperms include all trees that produce softwoods. Softwoods belong to the order Coniferales or more commonly called conifers. Conifer trees have needle- or scale-like evergreen leaves.

Angiosperms are divided into monocotyledons/monocots (i.e. one-seed leaf) and dicotyledons/dicots (i.e. two-seed leaves). Dicots include tree-sized plants that produce hardwood lumber. Hardwood trees have broad-leafed foliage and those found in temperate zones are typically deciduous. Wood species

In the United States, there are more than 100 wood species and approximately 60 species are of commercial importance. Tables 1 and Table 2 show the various U.S. softwood and hardwood species by region. Also included are the European wood species (Table 3) and foreign wood species (Table 4).

The American Softwood Lumber Standard PS 20-10 establishes the sizes and grades of various softwood species. PS 20-10 is used for domestic software lumber production consumed in – and exported from – the United States, and for softwood lumber imported into the United States. For grading of hardwood lumber, the Rules for the Measurement and Inspection of Hardwood and Cypress are used.

Wood pallet component grades were developed to control structural and functional performance, not appearance. There are five Pallet Design System™ (PDS) pallet component grades: select, premium, standard, utility and economy. 

Wood packaging manufacturing and recycling

The National Wooden Pallet and Container Association Uniform Standard for Wood Pallets and International Organization for Standardization (ISO) TC 51 Pallets for unit load methods of materials handling standards establish recognized minimum quality requirements for the wood pallets both nationally and internationally. There are two classes of pallets: stringer and block. The use categories are reusable and single-use pallets. The entry types are two-way, partial four-way and full four-way. Pallets are available in many sizes and designs.

Wood pallets are manufactured by fastening the wood components (i.e. deckboards, stringers, stringerboards, blocks) with nails or staples. It is important that pallet companies know the source of their wood materials (i.e. cants, lumber, plywood, wood-based composites) and also avoid any chemical treatment (e.g. 2,4,6 tribromophenol/TBP, 2,4,6 trichlorophenol/TCP, pentachlorophenol) that can induce anisole taint (e.g. 2,4,6 tribromoanisole/TBA, 2,4,6 trichloroanisole/TCA). Raw materials and pallet components must be properly handled prior to and during manufacture, in order to prevent cross contamination between new and recycled lumber.

Recycling of wood pallets is very common. These pallets are either reused, repaired (replace damaged component[s]) or remanufactured (dismantled then reassembled using recycled components or in combination with new components). Incoming pallets are inspected, sorted then processed (i.e. repaired, disassembled or discarded). During repair, disassembly or assembly, the recycled pallets are inspected as they go through the processing line. Visibly contaminated pallets or components are set aside for cleaning (e.g. power washing) or disposal. The major issue with recycled pallets is no one can tell where a pallet or its components came from (in terms of country origin or the industry in which it was previously used). However, it can be assumed that if a pallet successfully went through its initial life cycle and is then being repaired, taints are highly unlikely if the replacement components are properly sourced and controlled.

Household clean pallets are a must for the pharmaceutical industry. The pallets must have no gross level contaminants such as grease, chemicals, soil/mud, insect infestation, etc. (for the pharmaceutical manufacturer– general good manufacturing process (GMP) and good distribution practices (GDP) process control). New pallets are required for certain applications such as deliveries of raw materials to pharmaceutical companies. New pallets potentially have a higher risk of taints & mold if the ISPM 15 process uses steam heat vs. kiln dried. In other applications, recycled pallets are more practical and viable, and have a low risk if pallet management processes are implemented and followed.


International Standards for Phytosanitary Measures Publication No. 15 (ISPM 15) Regulation of wood packaging materials in international trade was published in order to harmonize the phytosanitary treatment and marking of wood pallets, containers, dunnage, etc. ISPM 15 was implemented to reduce the introduction and spread of forest quarantine pests (e.g. pinewood nematode, bark beetles) by killing the pests during treatment but not intended to provide ongoing protection from these pests.

Heat treatment (HT) and methyl bromide (MB) fumigation are the two approved phytosanitary measures in ISPM 15. HT is exposing wood packaging to heat with a time-temperature schedule that achieves a minimum temperature of 56°C for a minimum duration of 30 continuous minutes throughout the entire profile of the wood (including the core). Different energy sources (e.g. natural gas, woody biomass, electricity) or processes (kiln-drying, microwave, radio frequency) can be used to achieve the HT parameters.

Kiln-drying is a process of drying lumber in a dry kiln to a specified moisture content using the correct drying schedule (combination of dry- and wet-bulb temperature settings). Steam HT essentially heat the lumber or wood packaging in an HT chamber or dry kiln to achieve the 56°C-30-min. parameters without significant moisture content reduction. Kiln-dried softwood lumber used in wood packaging manufacture requires no further treatment (HT or MB fumigation) and can be considered ISPM 15-compliant. On the other hand, hardwood pallets and containers are typically assembled first then heat treated inside an HT chamber, or MB fumigated in order to be ISPM 15-certified.

In most countries, the National Plant Protection Organization (NPPO) directly certifies the wood packaging facility, and inspects or audits regularly the facility to maintain its certification. In the United S tates and Canada, facilities are certified by third-party inspection agencies that are accredited by non-government organizations (NGO) (e.g. American Lumber Standards Committee/ALSC, Canadian Wood Pallet and Container Association/CWPCA and NWPCA). These NGOs have an agreement with their respective NPPO (e.g. Canada and the Canadian Food Inspection Agency [CFIA], the United States and Animal and Plant Health Inspection Service [APHIS].

Mold Growth

When mold spores grow on wood, they normally discolor (black, orange, yellow, green) the surface only. The pharmaceutical industry has concerns on discoloration of wood packaging, not due to integrity issues (since mold does not affect the structural integrity of the wood pallet or container) nor because of potential product contamination from the mold (since the product is sealed away from the environment).

The concern: visible mold on the pallet is “just not a good practice” (and pharmaceutical supply chain partners would reject the shipment). The risk is that the mold could migrate onto the corrugate and the customer would reject the shipment. So mold not a product quality issue per se, but rather a customer satisfaction issue.

Food, oxygen, water/moisture and suitable temperature are required for mold growth. Wood has sugars, starches and proteins that serve as food. It also contains water but when wood is dried below 20 percent, this makes mold growth less likely. Hence, it is advisable to use dry components or dry the assembled wood pallets under 20 percent. Softwood pallets normally use components that have been kiln-dried to 19 percent. Hardwood pallets typically use green components and must be air or kiln dried after assembly in order to achieve the desired moisture content that will retard mold growth.

Another option to prevent mold growth is to use fungicides. This chemical treatment has been used to protect logs and lumber against mold. It can also be used on wood packaging as long as it has the proper formulation (without the halophenols) and verified with its Material Safety Data Sheet (MSDS).

Storage and Shipment

It is strongly recommended that pallets be maintained in a dry, well ventilated atmosphere. Indoor storage is the preferred method however, storage at the pallet manufacturing site can be “opened walled” but should have adequate ventilation. All pallets that have been stored outdoors must be re-inspected prior to shipment/delivery at all times. Pest mitigation procedures should be coordinated with pest control service providers at the pallet manufacturing site. Using compressed air to “blow the pallet clean” by removing any residual sawdust is an acceptable practice.

Pallet providers should use clean trailers and flat beds for deliveries to avoid contamination of pallets. It is suggested that records for every outbound trailer must be kept and maintained. Pallets must be unloaded from enclosed trailers as soon as possible. Leaving pallets inside enclosed trailers for extended period of time must be avoided since a non-ventilated trailer can provide optimal conditions for mold growth.

Conclusion – Part 2

The intent of this article was to provide information on wood, wood pallets and pallet manufacturing, recycling and handling. As pharmaceutical companies want pallet companies to comply with their supplier quality assurance (SQA) program, pallet companies should be diligent in making sure that the pallets they supply meets the GMP and GDP requirements of their customers in the pharmaceutical industry. The next article will include the pallet management program being instituted by a pharmaceutical company and hopefully the entire pharmaceutical industry.

(Article published in PalletCentral Magazine, July-August 2012)

David Ulrich holds the title of QA director Pharma Supply Chain at Abbott Laboratory. Jorgelina González is the Technical Lead at Paleteras Unidas & Caribe Recycling. Edgar Deomano is former Technical Director at NWPCA.