Chemical Alternatives

There are several alternative chemicals being promoted as alternatives to CCA, as listed in the table below. None of the available alternatives is a complete substitute on its own for all the uses of CCA and, although they do not involve arsenic or chrome, they still pose environmental and health risks.

Description of Chemical Alternatives to CCA

In addition, many of the alternatives listed in the table cost between 8 and 15 percent more than CCA-treated timber, although it is anticipated that costs will fall if demand rises because of limitations to the use of CCA (NSW EPA, 2003b).

These alternative chemicals employ copper as the main biocide, but also include co-biocides mainly to prevent copper-tolerant fungal decay (Lebow, 2004b). In their evaluation of alternative chemicals, Solo-Gabriele et al (2000) noted that ‘viable non-arsenical waterborne alternatives are available for above ground and ground contact applications’, which accounts for 60% of the treated wood volume. However, little is known of the impact of the co-biocides, and they recommend that their environmental impacts be further evaluated before they are promoted. Townsend et al (2003a) also warn against complete changeover to these chemicals, recommending chemical alternatives to CCA for all situations except those that might ‘impact sensitive aquatic ecosystems’, especially those with limited flushing (Townsend et al, 2003a).

Finally, if CCA-treated timber is to remain in place, the leaching and dislodgement impacts can be reduced temporarily by coating with a stain. Research by Strömberg (2003) found that acrylic coatings and stains provided the longest protection. She also determined that the manual application and drying of this stain was the most important phase in terms of minimizing the resultant environmental impacts. Lebow et al (2003) also determined that paint or pigmented stains provided an effective short term barrier to prevent CCA leaching from the treated timber, noting that clear stains or not sealing the timber quintupled the rate of leaching due to ultra-violet exposure.