Authors
Year of Publication: 2003
Abstract:
The Trace Air Contaminants Working Group under the Cumulative Environmental Management Association commissioned this study as the first phase in assessing potential risks posed by air contaminants to human health and ecosystems under existing environmental management systems in the Regional Municipality of Wood Buffalo (RMWB). This study consisted of three parts: I) compiling a list of airborne contaminants that are emitted in a study area within the RMWB; 2) ranking the contaminants; and 3) selecting key air contaminants for the following phases of the trace air contaminant program: evaluation of ambient concentrations and potential risk to human and ecological health.
In the first part of this study a detailed inventory of anthropogenic emissions of common air contaminants, volatile organic compounds (VOCs), and reduced sulphur compounds (RSCs) was completed for the northern and southern regions of the study area. The effective reference year for the inventory is 2000 and includes all existing and approved developments, and one applied for development. The one applied-for development in the inventory is the OPTI Long Lake project. Carbon dioxide emissions were specifically excluded from the inventory since they are only of concern as a greenhouse gas and not as an air toxic.
In the second part of this study, groups of contaminants for the northern and southern regions were ranked following three screening exercises:
toxic potential to humans (based on emission rates and toxicity weighting factors), odour potential (based on emission rates and odour thresholds), and the potential to bioaccumulate in biological organisms (based on emission rates and octanol-water partition coefficients).
For the third part of this study, air contaminant rankings were created by combining the results of the three screening exercises. The degree of certainty in the air contaminant selection process is highest for the toxic potential screening and lowest for the bioaccumulative potential screening. Four key conclusions were made:
Over 1400 unique air contaminants are emitted to the atmosphere by anthropogenic sources in the oilsands study area. However, the majority of the total mass of emissions is made up of only a few compounds (i .e. the top 15 compounds, mostly common air contaminants, contribute over 98 percent of the total emissions). The oilsands industry is the dominant source of virtually all emissions in the northern region due to its size and the general lack of other types of activities in the area. In the southern region there are a number of significant contributors including agriculture, forest products, conventional oil and gas, oilsands, and urban centres. Much better delineation of VOC and RSC emissions is available for the northern region than the southern region due to the availability of very detailed measurements conducted by the oilsands sector. Priority pollutants represent a small fraction of the list of air contaminants in the emission inventory. These pollutants comprise 99.9% of the toxic potential, odour potential and bioaccumulation potential of the entire emissions inventory. Based on emissions rates and toxicity weighting factors alone, it is not possible to determine whether some substances may exceed health benchmarks now or in the future. To do this, air dispersion models would be required to predict ambient concentrations in regional communities. Air dispersion modelling was not part of the scope of the current project. In addition, even if air dispersion modelling was done, only a few air quality guidelines are available to which to compare predicted concentrations (i.e. acid gases and particulate matter). Human health risk assessments would be required to evaluate the potential risks associated with other airborne substances.
Based on the findings of this study, the following recommendations are presented: The emission estimates of the priority pollutants identified herein should be refined to better support future efforts that may focus on these critical substances. Atmospheric dispersion modeling should be undertaken for selected compounds from the priority pollutant lists to determine the concentrations of these substances in air within regional communities and in recreational areas that are frequented by people. Human health risk assessments should be conducted based on the results of atmospheric dispersion modeling to determine the degree of potential risk posed to residents of regional communities and recreational users. Further research into the fate, transport, bioavailability and metabolism of compounds with high octanol-water partition coefficient (Kow) values should be undertaken to determine whether these substances will actually bioaccumulate in the environment.
