Wood preservation facilities, alkaline copper quaternary: chapter G-3


3. Environmental Effects

3.1 Aquatic Toxicity

In considering the aquatic toxicity of ACQ, the following points should be borne in mind:

  • The toxicity of the concentrates and working solutions should be considered since they are all handled at ACQ facilities.
  • The valence of copper may change in the environment, and these changes may reduce or enhance copper’s toxicity. No studies have been reported in the literature on valence inter-conversion of copper in soils, groundwater or surface runoff waters at or from wood preserving facilities. Nonetheless, it is known that reduced forms of copper rarely occur in aqueous environments (11).

Copper:

There is no acute aquatic ecotoxicity data available for this Copper Ethanolamine Complex but Copper is the component of this substance that imparts the pesticidal activity and is, therefore, the component of interest for a review of environmental fate and toxicity.

Several processes influence the fate of copper in the aqueous environment. These include complex formation, sorption to hydrous metal oxides, clays and organic materials, and bioaccumulation. Information on the physicochemical forms of copper (speciation) is more informative than total copper concentrations. Much of the copper discharged to water is in particulate form and tends to settle out, precipitate out or be adsorbed by organic matter, hydrous iron, manganese oxides and clay in the sediment or water column. In the aquatic environment the concentration of copper and its bioavailability depend on factors such as water hardness and alkalinity, ionic strength, pH and redox potential, complexing ligands, suspended particulate matter and carbon, and the interaction between sediments and water (12).

ADBAC: (n-Alkyl (67% C12, 25% C14, 7% C16, 1% C18) dimethyl benzyl ammonium chloride)

USEPA Reregistration Eligibility Decision categorized ADBAC as highly toxic to fish (LC50 = 280 μg ai/L) and very highly toxic to aquatic invertebrates (LC50 = 5.9 μg ai/L) on an acute exposure basis. Chronic effects were seen in fish at a concentration of 32.2 μg ai/L and a no observable adverse effect concentration of 4.15 μg ai/L was established for aquatic invertebrates.

The ADBAC component of ACQ-C is hydrolytically stable under abiotic and buffered conditions over the pH 5-9 range. However, based on a biodegradation study, the U.S. Environmental Protection Agency (USEPA) concluded that ADBAC readily degrades into 60% carbon dioxide in 13 days. The soil mobility study indicated that ADBAC is immobile in soil. ADBAC was not expected to pose a concern for bioconcentration in aquatic organisms (10)

DDACB/DDAC: (didecyl dimethyl ammonium chloride / carbonate / bicarbonate)

Didecyl dimethyl ammonium chloride (DDAC) is the representative of the group of quaternary ammonium compounds, and hazard data generated for DDAC are considered to be representative of the hazards associated with all chemicals assigned to this class of quaternary ammonium chemicals (7).

DDAC-based pesticides are persistent in soil and water/sediment systems. It is stable to hydrolysis, phototransformation and biotransformation and does not form any major transformation products in the environment. It strongly binds to soils; therefore, it has a low potential to leach into groundwater and contaminate it.

As DDACB-based pesticides partition into sediment, bind strongly and are persistent, they have a high potential to pose a risk to sediment-dwelling organisms. If surface runoff water from stacked treated wood in open lumber yards and effluents from treatment plants enter into aquatic systems, they will pose a risk to aquatic organisms (13).

Because DDAC is immobile in soil and is not subject to runoff contamination of water bodies, bioaccumulation of DDAC in freshwater fish or aquatic organisms is not likely to occur. Information on the aqueous availability of DDAC from wood indicates that the use of DDAC as a preservative may result in minimal releases to the environment (6).

In British Columbia, where DDAC is used in antisapstain formulations, provincial regulations state that the concentration of DDAC in effluent shall not exceed 700 mg/L (14).

Boron:

Boric Acid may be present at various concentrations in ACQ solution. The boric acid is added as a corrosion inhibitor and not as an active ingredient which why it is generally present in low concentration.

Boron’s effects on aquatic plants are highly species-specific (15). Borate, like silicate, is an essential micronutrient for the growth of aquatic plants. Boron, under conditions of excess, alleviates nutrient deficiency in some phytoplankters and may cause temporal variations of phytoplankton composition in coastal waters (15). Phytoplankton can tolerate up to 10 mg inorganic B/L in the absence of stress from pH adversity and nutrient deficiency, although higher borate concentrations up to 100 mg/L are expected to cause species redistribution by favoring the growth of some species and suppressing that of others (16). Boron has been shown to accumulate in aquatic plants, which may be evidence for its importance in plant nutrition. Despite a tendency to accumulate in plants and algae, boron does not appear to biomagnify through the food chain (17).

Juvenile Pacific oysters (Crassostrea gigas) accumulated boron in relation to availability, but showed no prolonged retention following cessation of exposure. At current industrial discharge levels of about 1.0 mg B/L, no hazard is clear to oysters and aquatic vertebrates (18).

The most sensitive aquatic vertebrates tested for which data are available were coho salmon (Oncorhynchus kisutch), with a median lethal concentration (LC50) value of 12 mg B/L in seawater (16-day exposure), and sockeye salmon (O. nerka), showing elevated tissue residues after exposure for 3 weeks in seawater containing 10 mg B/L.

Boron concentrations between 0.001 and 0.1 mg/L had little effect on survival of rainbow trout embryos after exposure for 28 days. These low levels may represent a reduction in reproductive potential of rainbow trout, and > 0.2 mg B/L may impair survival of other fish species, according to Birge and Black (19); however, additional data are needed to verify these speculations. Birge and Black reported that concentrations of 100-300 mg B/L killed all species of aquatic vertebrates tested; that embryonic mortality and teratogenesis were greater in hard water than in soft water, but that larval mortality of fish and amphibians was higher in soft water than in hard water; and that boron compounds were more toxic to embryos and larvae than to adults (20).

Canadian guidelines on maximum concentrations for ACQ solution and ethanolamine in aquatic environments have not been established, but guidelines do exist for DDACB, ammonia and copper as listed in Table 3. However, as these limits are subject to change from time to time, periodic reviews of the limits and guidelines are recommended.

The guidelines and limitations for copper 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 (21).

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.

3.2 Air Pollution

Airborne pollution from ACQ facilities can have significant levels of ammonia and/or ethanolamine emissions. Air emission levels should be monitored, and appropriate control devices such as scrubbers can be employed where necessary to meet air emission regulatory limits.

3.3 Soil Contamination

In the terrestrial environment a number of factors influence the fate of copper in soil, including: the nature of the soil itself, pH, presence of oxides, redox potential, charged surfaces, organic matter and cation exchange. Most copper deposited in soil is strongly adsorbed. Bioaccumulation of copper from the environment occurs if the copper is biologically available. Accumulation factors vary greatly between different organisms, but tend to be higher at lower exposure concentrations. Accumulation may lead to exceptionally high body burdens in certain animals (such as bivalves) and terrestrial plants (such as those growing on contaminated soils). However, many organisms are capable of regulating their body copper concentration (12).

Copper is an essential element required for good health and proper functioning of biological processes in plants and animals. Copper overexposure and deficiency can both have serious adverse effects (22).

Page details

Date modified: