Pressure treating is a process of wood preservation, wherein chemical preservatives are applied on the wood, in order to protect it from insects and fungus. This helps extend the lifespan of the wood, and makes it resistant to harsh environmental conditions. Though highly durable, and resistant to harsh conditions and decay, this type of wood has raised concerns about certain possible health hazards.
More About Pressure Treatment
During pressure treatment, the wood is first placed in a cylinder or cylindrical tank. The tank is depressurized so as to remove all air from inside. Then the wood is treated with the chemical preservative under high pressure, so that the chemical can reach the deeper layers of the wood. There are basically three types of preservatives that are used for making highly durable pressure-treated wood. They are known as water-borne preservatives, oil-borne preservatives, and creosote.
The wood treated with water-borne preservatives are mainly used for residential and industrial applications, while oil-borne preservatives are used for treating wood that are to be used in making utility poles. Creosote on the other hand, is primarily used for treating wood, which are to be used in railroad ties and marine structures. The commonly used water-borne preservatives are CCA (Chromated Copper Arsenate), ACQ (Alkaline Copper Quat), sodium borates, and Micronized Copper Quat (MCQ). Wood treated with water-borne preservatives are usually used for walkways, decks, playground equipment, fences, etc.
Risks Associated with Pressure-treated Wood
Most of the possible health hazards associated with treated wood are due to the use of Chromated Copper Arsenate (CCA). Arsenate found in CCA is inorganic arsenic, and so experts are of the opinion that it can easily accumulate inside the living tissues. Inorganic arsenic is considered to be a carcinogen, and the long term exposure to it is believed to raise the risk of several types of cancer, especially in children who regularly play in playsets made of wood that is pressure treated. Children who are regularly exposed to soil contaminated with oil-borne preservatives used in treated wood, may also have an increased risk of developing cancer.
Another concern raised against the use of CCA-treated wood is that, the chemical may leach from the wood into the soil, and then bind to the soil particles and increase the level of inorganic arsenic. Considering the various possible hazards related to chemically-treated wood, EPA (Environmental Protection Agency) has put restrictions on the use of CCA. Presently, CCA is substituted with ACQ in treating wood that are used for residential and consumer use.
But CCA is still used for treating wood that are used for industrial purposes. Apart from CCA, preservatives like creosote and pentachlorophenol can also pose a few health risks. Pentachlorophenol may raise the risk of developing cancerous tumors and birth defects. Creosote may increase the risk of developing cancerous tumors and genetic mutations.
However, the results of various studies conducted to unearth the health hazards associated with treated wood are not very conclusive. Nevertheless, it has been observed that the sawdust of such wood can irritate the eyes, nose and the skin, for which care must be taken to avoid direct contact. It is also not advisable to burn such wood, especially if it is treated with arsenic-containing preservatives. The ash produced while burning such wood can be toxic, as arsenic does not burn-off. Apart from these, making or preparing food on chemically-treated wood should be strictly avoided.
It is true that ACQ is a less toxic chemical than CCA, and is presently being used for treating wood which are used for residential purposes. But still, it is better to be a bit careful with all types of treated wood. It is possible to minimize the CCA and ACQ hazards with the help of a few simple preventive measures. For example, you can paint the treated wood to minimize the exposure to harmful chemicals. You can apply an oil-based sealant on the wood in order to seal in the chemical preservative. This can help minimize leaching as well. Parents should make sure that their children wash their hands properly after playing in an outdoor playset. Putting sand or pea stone on the ground around the treated wood can help prevent direct contact with the soil beneath the wood, which may have high levels of arsenic. Lastly, if the wood is CCA treated, then it should not be used for mulching.