Pressure-treated wood once contained chromated copper arsenate as a preservative. This substance protects the wood so that the wood can resist damage caused by high moisture. However, because of the arsenic contained in the chromated copper arsenate, the Environmental Protection Agency banned the use of pressure-treated wood for residential use in 2004, though industrial and agricultural endeavors still use the material.
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When burning the wood, the arsenic enters into the air and it can kill those who breath in the fumes directly. Because of this, burning pressure-treated wood is illegal in all 50 states. The arsenic has no distinct odor, so those breathing in the fumes will not realize what they're breathing. As a result, firefighters and landfill operators must take special precautions when working with burning pressure-treated wood. Even small amounts of pressure-treated wood ash can lead to major health problems. When cleaning up after burned pressure-treated wood, technicians should wear a respirator and treat the region as a toxic zone.
While no studies have been done, pressure-treated wood often has warning labels that advise against grinding the wood into sawdust, since this practice might release harmful arsenic. However, the EPA recommends that any workers surrounded by sawdust should wear face protection. Direct contact with pressure-treated wood can cause the arsenic to absorb through the hands. This can be especially problematic for children playing near pressure-treated wood.
Acid Rain Leaching
The arsenic in the wood can leach into the soil when acid rain and other acidic materials abrade the pressure-treated wood, causing the arsenic to potentially leach into groundwater, which can lead to accidental human consumption. Also, arsenic and zinc can combine to form arsine gas, which can cause minute health problems.
The pressure-treated wood is not very durable compared to new types of treated wood. For residential areas, manufacturers now use alkaline copper quat or copper azole, which can protect the wood from pests, and also prevent rot caused by mold and other microbial agents. However, the increased copper content can make the wood more expensive. Also, the copper content makes the wood materials corrode more during adverse weather conditions. The corrosion can make the structures more vulnerable in tornadoes and hurricanes. Manufacturers can also use borate-treated wood to stop bugs and mold. The human body can absorb borate and release it when no longer needed. Those who have pressure-treated wood in their homes can coat the wood with an oil-based stain.