Wood preservation facilities, copper azole : chapter H-3
3. Environmental Effects
3.1 Aquatic Toxicity
Canadian limits for tebuconazole and monoethanolamine have not been established, but limits for copper in aquatic environments are listed in Table 3. However, as these limits are subject to change from time to time, periodic reviews of these limits is recommended.
The guidelines and limitations noted in Table 3 are based on total concentrations, reflecting the recommendations of many scientific reviews that indicate that the current state of knowledge does not enable water quality limitations to be based on either valence state or dissolved fractions in water (6).
Provincial guidelines are applicable and should be consulted. Provincial guidelines may differ from or be more specific than national guidelines. Provincial regulations may require additional measures that may enhance, but not reduce, protection.
Tebuconazole
While tebuconazole is slightly persistent in the environment, it has been shown not to be mobile. In addition, light dramatically enhances the degradation process. In the Organization for Economic Co-operation and Development’s (OECD) Test Guideline 301C, tebuconazole degrades approximately 20% in water. Its half-life in soil is around 100 days. Tebuconazole is considered moderately toxic to aquatic organisms and has a slight potential to bioconcentrate, but it is rapidly eliminated from fish.
Copper
Toxicity depends on bioavailability, but copper is generally reported as toxic to aquatic organisms. Copper is considered not to be bioaccumulative.
Copper-containing pesticides are formulated using various forms of copper, which ultimately dissociate into cupric ion complexes and compounds, including the cupric ion (Cu2+), which is the active component.(7)
The active component of toxicological concern with the majority of copper-containing pesticides is elemental copper (the cupric ion), and most copper compounds can be considered similar in terms of their toxicity.
Copper is expected to pose a risk to aquatic organisms and terrestrial vascular plants. As such, mitigative measures must be taken to minimize adverse effects on plant populations and aquatic organisms. (7) Copper is an element that occurs naturally in the environment and does not break down any further via hydrolysis, metabolism or any other degradation processes. The free cupric ion has a high sorption affinity for soil, sediments and organic matter, and copper applied to the soil surface is not expected to move readily into groundwater. The copper ion is highly reactive, especially in aquatic environments. The form in which copper is found depends on the pH of the medium and the nature and concentration of other forms of copper present.
Copper Monoethanolamines
The amine use in the Wolman® NB product is a copper ethanolamine complex that carries the copper into the wood. The following overall ecotoxicity statement for ethanolamine, as a pure formula, can be used as a reference to understand the potential impact of such substance:
2-Aminoethanol or monoethanolamine (often abbreviated as ETA or MEA) is an organic chemical compound that is both a primary amine and a primary alcohol (due to a hydroxyl group). MEA is not expected to bioaccumulate in aquatic organisms. MEA has demonstrated a relatively low degree of toxicity to aquatic organisms (8).
A series of pan studies was conducted under various environmental conditions to examine the biodegradability of MEA in soil recovered from a gas plant site. Experimental results indicate that MEA was successfully biodegraded or transformed into other compounds under both aerobic and anaerobic conditions even at concentrations greater than 1500 mg/kg. Ammonium, acetate, and nitrogen gas were the dominant by-products in these experiments. The generation of nitrogen gas suggests that simultaneous nitrification and denitrification occurred because of the existence of anoxic zones resulting from diffusion that limited oxygen transport into the soils. Cold temperatures (5°C) reduced biodegradation rates significantly compared to rates at room temperature (9).
MEA is expected to be mobile in soil and is not expected to be adsorb to suspended solids or sediment in water. It readily undergoes biodegradation and is not expected to persist in the environment.
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