Impacts of livestock chewing on treated wood

Livestock chew on treated lumber because of mineral imbalance or boredom. This raises concern over animal health and meat safety.

Treated wood is found in many places on a farm because over time it holds up to weather elements and prevents damage from insects remarkably well. It is treated with a combination of chromium, copper, and arsenic. Thus, wolmanized or treated wood may also be referred to as CCA treated wood. Inadequate mineral balance or consumption, particularly of phosphorus and selenium, or just plain boredom experienced by livestock may cause them to chew on the wood. This can affect the health of the animals, depending on the amount consumed.

The inclusion of arsenic in CCA treated wood is of concern to animal health if ingested. Arsenic in its inorganic form is a carcinogenic in humans. Arsenic is a natural element, ubiquitous in the environment.  In addition to soil and plants, arsenic can also be found in some water sources, thus potentially adding to the amount ingested by an animal. Tolerance levels of inorganic arsenic (As2O3) in animal products ranges from 0.5 to 2.0 ppm. If an animal does ingest large quantities of As2O3 then acute arsenic toxicity could occur. Death could occur in animals with levels higher than 2 ppm in the liver. The concentration of chromium, copper, or arsenic would likely be found in the internal organs, including the liver, kidneys, lungs, and intestines, of animals experiencing toxicity from eating CCA treated wood. The concentration of arsenic in muscle is usually several folds lower than that in the internal organs. Other signs of toxicity that are less severe than death include diarrhea, depression, lack of coordination, and weakness.

The subsequent safety of the meat from an animal that ingests CCA treated wood depends on how much the animal ate and if there are other sources of arsenic in the animal’s diet. Arsenic has a short half-live in animals. Stopping exposure is an effective way to decrease its concentration in the tissues. Again, the highest concentration of arsenic would be found in internal organs like the liver and kidney. Without testing, one could not be certain of the level of inorganic arsenic found in the meat, and whether or not the meat would be safe for consumption. 

Testing of animal products can be done at Michigan State University’s Diagnostic Center for Population and Animal Health (DCPAH) to determine the concentration of any of the involved compounds.

Additionally, organic producers are not allowed to use treated lumber in new construction or with replacement projects in places where the lumber could come in contact with crops, livestock or soil.

Another important reminder when working with wolmanized or CCA-treated wood is to never burn it. Ashes and smoke created from burning CCA-treated lumber have greater health hazards because they are often associated with much higher exposure in human and animals than the wood itself. 

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