CCA leaches out of the treated timber over time there can be residues
of arsenic, copper and chromium on the surfaces of the wood and
it can be washed off by rain to accumulate in the soil or water
below. All three metals pose a potential threat to the environment.
According to the US EPA: ‘The amount and rate at which arsenic
leaches, however, varies considerably depending on numerous factors,
such as local climate, acidity of rain and soil, age of the wood
product, and how much CCA was applied.’ (Office of Pesticide
contamination from CCA-treated timber can occur at many points along
the life cycle of the product, from manufacture, to handling and
use, and to disposal. The APVMA concluded that there are ‘unintended
harmful environmental effects… [such as] contamination during
the treatment process, leaching of arsenic from treated timber into
soils or water, and disposal or burning of discarded timber’
(APVMA, 2003, p.9).
impacts of heavy metal leaching into surrounding soil and water,
and dioxins and furans being released into the air when treated
timber is burned, particularly after bushfires, have been the subject
of a number of academic studies (see section on Waste
plants can also get particularly contaminated. An audit undertaken
by the NSW EPA of five timber treatment plants found contamination
through inadequate storage of materials and wastes at 5 plants,
failure to maintain drains, dams or treatment facility at 4 plants,
and inadequate surface water controls at 4 plants (NSW EPA, 2003).
There have been no corresponding audits of Victorian timber treatment
plants by the Victorian EPA.
Committee on Toxicity, Ecotoxicity and the Environment (CSTEE) of
the European Commission noted: ‘There is extensive documentation
of past substantial soil and groundwater contamination at wood treatment
sites…There is also evidence in the published literature…
that contamination of the soil and vegetation can extend to the
area beyond the immediate boundaries of such sites, something that
has been attributed to wind erosion, percolation, surface drainage
as well as on-site incineration of wood waste’ (CSTEE, 1998).
(2003), The Reconsideration Of Registrations Of Arsenic Timber
Treatment Products (CCA And Arsenic Trioxide) And Their Associated
Labels (Review Summary), Australian Pesticides And Veterinary
Medicines Authority, Canberra. (pdf - 1.2MB)
(Scientific Committee on Toxicity, Ecotoxicity and the Environment)
(1998), ‘Opinion on the Report by WS Atkins International
Ltd (Vol. B) "Assessment of the Risks to Health and to the
Environment of Arsenic in Wood Preservatives and of the Effects
of Further Restrictions on Its Marketing and Use" Expressed
at the 5th CSTEE Plenary Meeting.’ Brussels: European Commission
(EC). 15 September.
EPA (2003), Environmental Compliance Report- Wood Preservation
Industry: Part A, Compliance Audit, NSW Environment Protection
of Pesticide Programs (2002). ‘Questions & Answers:
What You Need to Know About Wood Pressure Treated with Chromated
Copper Arsenate (CCA).’ US Environmental Protection Agency
(EPA). 12 February. http://www.epa.gov/oppad001/reregistration/cca/cca_qa.htm.