Priority Substances List Assessment Report for Releases from Primary and Secondary Copper Smelters and Copper Refineries - Releases from Primary and Secondary Zinc Smelters and Zinc Refineries

Synopsis

Assessments of the two substances "Releases from primary and secondary copper smelters and copper refineries" and "Releases from primary and secondary zinc smelters and zinc refineries" have been conducted and reported together due to the similar nature of the two types of facilities and the common approach used in assessing their releases. For the purposes of these assessments, a smelter is defined as a facility that uses high-temperature chemical processes to recover base metals, while a refinery is a plant in which impurities are separated from metals using thermal or electrolytic processes. Zinc operations use integrated processes that are a combination of smelting and refining and are conventionally referred to as "zinc plants." The six copper smelters, four copper refineries and four zinc plants currently operating in Canada were considered in the assessments.

Releases from copper smelters/refineries and zinc plants are complex mixtures, containing varying amounts of numerous substances. Since most releases (on a mass basis) are discharged to air, and releases to air have the greatest potential for causing widespread effects, these assessments have focused on environmental and human health risks of air emissions. The components of releases to air that were examined most closely are sulphur dioxide (SO₂), the metals (largely in the form of particulate matter) copper, zinc, nickel, lead, cadmium, chromium and arsenic, and particulate matter less than or equal to 10 microns (PM₁₀). For facilities having multiple operations, source emission attribution was evaluated to estimate the fraction of ambient and deposited contaminants attributable to those operations that are the subject of these assessments.

Risk due to SO₂ released from copper smelters/refineries and zinc plants was assessed based on both direct exposure to SO₂ and associated acidic deposition. Effects thresholds for direct exposure to SO₂ were based on vegetation exposed for periods of 1 hour (acute) and one growing season (chronic). Results for direct exposure indicate that there is a risk to vegetation over varying areas near both copper smelters/ refineries and zinc plants, to a maximum distance of about 10 km. For acidic deposition, it was determined that copper smelters contributed up to 8% (relative to all anthropogenic and natural sources) of the SO₂ resulting in acidic deposition at the four eastern Canadian receptor areas considered. Copper refineries and zinc plants were responsible for significantly lower fractions (up to 0.1% and 0.2%, respectively). U.S. sources were the largest contributors at all four receptor sites.

Endpoint organisms were identified for exposure to each metal examined in both aquatic and terrestrial environments (relating to deposition to surface waters and land, respectively). The 95th percentiles of natural background metal concentrations were used as lower limits for the effects thresholds. The transport and fate of metals deposited on surface waters and soils were modelled to permit estimation of critical metal deposition values ("critical loads") - defined as the amount of annual deposition required for steady-state metal concentrations to reach these low effect concentrations in receiving surface waters and soils. Probabilistic modelling was based on the range of receptor conditions (soil types, pH, lake size, etc.) encountered on the Canadian Shield. Estimated free metal ion concentrations were assumed to be representative of the concentration of biologically available metal.

Estimated annual metal deposition rates were compared with 25th percentile critical loads representative of effects on sensitive organisms under 25% of conditions in sandy soils or acidic lake water of the Canadian Shield. It was concluded that there is potential for effects on aquatic and/or soil-dwelling organisms from exposure to steady-state concentrations of metals in the vicinity of copper smelters/refineries and zinc plants resulting from emissions (especially of copper and zinc, respectively) from these facilities. Impacted areas were estimated to extend up to about 13-14 km from the facilities. In all cases, it is recognized that the range of impact is dependent on the emissions of the individual facilities as well as on local meteorology and geography. Range of impact is also dependent on the percentile of the critical load on which the comparisons are based. A lower percentile critical load, representing risk under a smaller fraction of Canadian Shield conditions, would result in estimation of impacts to greater distances. It is also recognized that emissions from zinc plants using exclusively pressure-leach technology will be significantly less than those from plants using roasting processes.

Screening-level evaluations of the environmental effects of aquatic releases from the three facilities (namely Cominco-Trail, Noranda-CCR and Noranda-CEZinc) that are not currently required to report their aquatic releases under the Metal Mining Liquid Effluent Regulations of the Fisheries Act were conducted. Constituents of releases to water considered in these assessments include all metal contaminants reported to be present, as well as ammonia, fluoride and pH. The results of the assessments of these three facilities indicated the potential for detrimental effects on the environment. However, the indicators of risk were fairly low, especially given the slightly conservative nature of the assessment.

The assessed facilities are also sources of carbon dioxide, nitrous oxide, methane and volatile organic compound (VOC) emissions. The former three contribute to global climate change, while VOCs contribute to tropospheric photochemical ozone creation, and some VOCs contribute to stratospheric ozone depletion. Emissions of all of these substances from copper smelters and refineries and zinc plants are, however, minor in comparison to those from other emission sources.

The health assessment addressed potential risks to nearby populations from current releases from copper smelters/refineries and zinc plants in Canada. Based on recent data, concentrations of arsenic, cadmium, chromium, nickel, lead, SO₂ and particulate matter in air are generally increased in the vicinity of most Canadian copper smelters/refineries and zinc plants in relation both to proximity to the facilities and background concentrations at remote sites.

The results of available epidemiological studies of human populations resident near copper smelters/refineries and zinc plants are inadequate to characterize the potential for both cancer and non-cancer effects from releases from such facilities. Based on assessments conducted previously on the Priority Substances List under the Canadian Environmental Protection Act (CEPA), carcinogenicity is considered to be the critical effect for arsenic, cadmium, chromium and nickel, in light of the sufficient weight of evidence for lung tumours in occupational populations or experimental animals following inhalation of compounds of each of these metals. The range of annual mean concentrations of PM₁₀ near Canadian copper smelters/refineries and zinc plants overlaps those associated with increased cardiorespiratory morbidity and mortality in recent extensive epidemiological studies of the general population exposed to ambient air pollution in various countries, including Canada. The concentrations of SO₂ in ambient air in the vicinity of all Canadian copper smelters/ refineries and zinc plants occasionally exceed health-based guidelines intended to protect against cardiorespiratory effects. Although not directly considered in this assessment, it is also recognized that SO₂ is an important precursor in the secondary formation of respirable particulate matter, especially the fine fraction (PM_2.5). Levels of airborne lead also exceed health-based guidelines near certain of the Canadian facilities involved in smelting copper, indicating potential for lead-induced health effects.

Based on available data, it has been concluded that emissions from copper smelters and refineries and from zinc plants of metals (largely in the form of particulates) and of sulphur dioxide are entering the environment in quantities or concentrations or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. Based on available data, it has been concluded that emissions from copper smelters and refineries and emissions from zinc plants are not entering the environment in quantities or concentrations or under conditions that constitute or may constitute a danger to the environment on which life depends. Based on available data concerning the effects of PM₁₀, sulphur dioxide and compounds of arsenic, cadmium, chromium, lead and nickel, it has been concluded that emissions from copper smelters and refineries and from zinc plants of PM₁₀, of metals (largely in the form of particulates) and of sulphur dioxide are entering the environment in quantities or concentrations or under conditions that constitute or may constitute a danger in Canada to human life or health. Therefore, metals (largely in the form of particulates) contained in emissions from copper smelters and refineries, metals (largely in the form of particulates) contained in emissions from zinc plants, PM₁₀ and sulphur dioxide are considered "toxic" as deflned in Section 64 of the Canadian Environmental Protection Act, 1999 (CEPA 1999).

There are a number of ongoing initiatives that address different release components of copper smelters/refineries and zinc plants. These include activities resulting from the Base Metals Smelting Sector Strategic Options Process, the Canada-wide Standards initiative for PM₁₀ and PM_2.5, and the Canada-wide Acid Rain Strategy for Post-2000. There are also activities resulting from the addition of PM₁₀ to Schedule 1 of CEPA 1999. Any investigations of options to reduce exposure as a result of these assessments should be integrated with these initiatives.

Comparison of estimated exposure to arsenic, cadmium, chromium and nickel in the vicinity of Canadian copper smelters/refineries and zinc plants with the tumorigenic potency indicates that the priority for investigation of options to reduce human exposure to releases from these facilities is considered to be in the high range for copper smelters, to range from low to high for copper refineries, and to range from low to high for zinc plants. Comparison of levels of lead, SO₂ and PM₁₀ in ambient air with health- based guidelines or with concentrations at which health effects have been observed also suggests that the priority for options analysis is high, especially for facilities where copper is smelted.

Given existing controls on effluents put in place by the companies or imposed by Provincial governments or other authorities, Federal prevention or control actions under the Canadian Environmental Protection Act, 1999 (CEPA, 1999) are not recommended at this time. It is believed, however, that an increase in contaminant concentrations or loadings or changes in conditions affecting bioavailability (such as pH) have the potential to significantly increase risk to the environment. It is important that facility operators recognize that if information, such as monitoring data, shows a significant increase in contaminant concentrations or loadings or changes in conditions affecting bioavailability, such information may be subject to reporting under Section 70 of CEPA, 1999.

Assessment of releases from copper smelters/refineries and zinc plants necessitated evaluation of a limited number of components from the complex mixture of substances released. The constituents of emissions to air examined generally represent the substances released in the greatest quantity. This selection does not imply that other release constituents do not pose a risk. Investigations of options for risk management should also take into consideration other substances of potential concern, some examples of which include mercury, selenium, dioxins and furans.