Wood preservation facilities, chromated copper arsenate: chapter B-1

1. Production and Use

Chromated copper arsenate (CCA) is sold throughout the world as dry mixtures of crystalline powders, as pastes or as liquid concentrates. The registered CCA pesticides in Canada are all in liquid concentrate form. Hartford (1) describes the mixtures, which are prepared with a variety of different ratios of chromium, arsenic and copper. The only CCA formulation currently in use in Canada is known internationally as a Type C oxide formulation, which is prepared from copper oxide and chromic and arsenic acids.

The use of CCA-treated products over the last 40 years has increased significantly, particularly as a result of its acceptance in the residential markets until 2003. The ability to stain or paint CCA-treated wood, as well as the ease of handling treated products, resulted in widespread usage by homeowners for uses such as deck and patio construction, playground equipment, landscaping, foundation lumber and plywood, and fence posts (2). However, CCA was voluntarily withdrawn from use in residential applications; as of December 31, 2003, it can be used only for industrial wood products as per registration requirements. CCA uses for such industrial applications are summarized in Table 1(3).

The conditions of use specified on the pesticide label are mandatory by law. Electronic copies of the pesticide labels for all registered CCA products, which contain information on allowable uses, product handling precautions, minimum worker protective equipment and health hazard warnings, can be obtained from the Health Canada website (7).

The CSA O80 Series of Standards specifies requirements related to the preservation and fire retardance of wood through chemical treatment (pressure), which includes Chromated Copper Arsenate (CCA), Type C"-treated products. (4)   Treatment conditions must be calibrated to yield the target retention levels described on the pesticide label.”