Chromated copper arsenate

Chromated copper arsenate (CCA) is a chemical compound used as a wood preservative. It is a water-based mixture of chromium, copper, and arsenic formulated as oxides or salts. CCA is used to protect wood from rotting due to insects and microbial agents. It has been widely used in the treatment of timber for outdoor applications such as decks, fences, and playground equipment.

Chemical Composition

CCA is composed of three primary elements:

• Chromium: Acts as a fixative, binding the preservative chemicals to the wood fibers.
• Copper: Serves as a fungicide, preventing the growth of fungi that can cause wood decay.
• Arsenic: Functions as an insecticide, deterring wood-boring insects.

The typical formulation of CCA is a mixture of these elements in the form of oxides or salts, which are dissolved in water and applied to wood under pressure.

History and Usage

CCA was first developed in the 1930s and became widely used in the 1970s. It was favored for its effectiveness in preserving wood and its ability to penetrate deeply into the wood fibers. However, due to concerns about the potential health risks associated with arsenic exposure, the use of CCA-treated wood has been restricted in many countries.

In the early 2000s, the United States Environmental Protection Agency (EPA) and other regulatory bodies began to phase out the use of CCA for residential applications. As of 2004, CCA is no longer used for residential purposes in the United States, although it is still used for industrial applications such as utility poles and marine pilings.

Health and Environmental Concerns

The primary concern with CCA-treated wood is the potential for arsenic leaching into the environment and human exposure through direct contact or inhalation of sawdust. Arsenic is a known carcinogen, and prolonged exposure can lead to serious health issues.

Studies have shown that CCA-treated wood can leach arsenic into the soil and water, posing risks to both human health and the environment. As a result, alternative wood preservatives, such as alkaline copper quaternary (ACQ) and copper azole, have been developed and are now more commonly used.

Regulations and Alternatives

Due to the health risks associated with CCA, many countries have implemented regulations to limit its use. In the United States, the EPA has restricted CCA for residential use, and similar regulations exist in the European Union and other regions.

Alternatives to CCA include:

• Alkaline copper quaternary (ACQ)
• Copper azole
• Micronized copper

These alternatives are considered to be less toxic and more environmentally friendly.

Also see

• Wood preservation
• Pressure-treated wood
• Arsenic
• Copper
• Chromium