Chemicals considered to be pesticides are used in the pressure treatment of wood products, such as telephone poles, railway ties and consumer lumber products. Scientific information is reviewed to determine whether risks for a wood treatment chemical are acceptable or unacceptable. If risks are acceptable, the wood treatment product is registered, with an approved label, under the Pest Control Products Act.
In addition, Health Canada also has the authority to undertake the periodic reassessment of all registered products and to conduct an up to date safety assessment. The result of this assessment is to decide if continued use is acceptable. Wood treatment products used for pressure treatment are presently undergoing such a safety reassessment in a joint project with the U.S. Environmental Protection Agency. This reassessment is targeted for completion in 1999.
(a) At present, there is a variety of chemicals used for wood preservatives or treatments which are registered and, therefore, approved for pressure treating lumber. They include pentachlorophenol, creosote, copper chromated arsenicals, borax based products, and products based on the common household disinfectant active ingredients called quaternary ammoniums with copper. These chemicals vary in how effective they are in protecting wood and are selected for use according to the intended use of the wood product.
(b) Acceptable levels of use are determined as part of the assessment of risk and performance conducted by the Pest Management Regulatory Agency in Health Canada before a product is approved for use. As part of the performance assessment process, Health Canada determines the lowest amount of chemical that can be used to effectively protect the wood. The selection and verification of the lowest needed amount helps to ensure that risk of exposure is, in turn, the lowest possible. In considering the appropriate level of use, Health Canada also relies, in part, on Canadian Standard Association standard 080, which outlines the amount of chemicals used in order to maintain the structural integrity of certain wood products, for example, telephone poles. The Pest Management Review Agency reviews product performance data against this standard as part of the assessment process. Specific values for use are contained on the product label and in the Canadian Standard Association standard 080.
(c) 1. Provincial regulatory programs have the authority and regular opportunity to monitor activities related to wood treatment.
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Environment Canada and Health Canada have worked co-operatively in the development of technical recommendation documetns, TRDs, that would foster a best practice approach to the use of wood treatment chemicals.
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Federal regulatory activities are largely based on complaints and incidents requiring investigation.
(d) Before a wood treatment chemical can be used in Canada it must be registered, or approved for use, under the Pest Control Products Act. In order for it to be registered, the chemicals undergoes a safety assessment that includes considerations of possible effects and exposure to the chemical. These effects are considered for those involved in the treatment process as well as those using the treated wood. Furthermore, health risks are considered for all new products as well as those that are currently being reassessed.
Labels on registered products include information regarding personal protection, to be observed in the handling of treated wood at the time of treatment as well as the time of post treatment. Additional labelling information includes prohibitions specific to the handling, use and disposal of treated wood. For example, it is not permitted to burn treated wood due to the possibility of releases of toxic materials during burning.
Health Canada is responsible for protecting the health of Canadians who use wood treatment chemicals and the resulting treated wood. These chemicals undergo an extensive safety assessment process prior to being made available to the wood treatment industry. As part of the safety assessment process, the safety of those involved in the treatment industry, as well as users, both industrial and consumer of treated wood products is considered. Health Canada is currently engaged in a reassessment of these products with its U.S. colleagues which will address health safety considerations associated with these products.