Ecosystem Exposure Polycyclic Aromatic Compounds (Passive), Oil Sands Region

Environment and Climate Change Canada has been monitoring ambient air in the oil sands region for polycyclic aromatic compounds (PACs) using passive air samplers since November 2010. Ambient air samples collected using the established protocols of the Global Atmospheric Passive Sampling (GAPS) Network are termed passive PAC samples. Passive samplers are deployed for two-month periods across a network of 17 sites that are maintained by the Wood Buffalo Environmental Association. Average PAC levels across the passive sampling sites in the oil sands region are comparable to urban/sub-urban levels across Canada and are elevated compared with background rural sites in Canada. Higher concentrations of PACs are measured at sites that are closer to oil sands mining and upgrading facilities compared with sites that are further away. Benzo(a)pyrene (BaP) is a PAC formed mainly as a result of incomplete combustion of carbon-based materials and fuels during industrial and other human activities, as well as natural events such as forest fires. It is associated with heavy molecular weight PACs that may be more carcinogenic. The data from the measurements conducted so far (excluding data from May and June 2011 due to forest fires) indicate that BaP levels exceed the Alberta ambient air quality objective of 0.3 ng/m3 as an annual average concentration (based on chronic and carcinogenic human health effects) at one location. In October 2013, Environment and Climate Change Canada began investigating levels of nitro-PAHs (NPAHs) and oxy-PAHs (OPAHs) in the air monitoring samples. These types of PACs are either formed in the atmosphere as secondary organic pollutants (e.g. through atmospheric oxidation reactions of PACs) or co-released with other PACs from incomplete combustion processes. The spatial distribution of NPAH and OPAH concentration in air across the oil sands region is different than that of the directly emitted parent PACs concentration which decline with increasing distance from the oil sands mining and upgrading facilities. The different distribution results from their formation and transport in air. Their formation depends on the availability of precursor molecules, levels of atmospheric oxidants, as well as by physical and chemical processes in the atmosphere. Currently there are no air quality guidelines for NPAHs and OPAHs against which to assess the level of concern. Also, NPAHs and OPAHs are typically not monitored in air due to the complexity in analyzing them and therefore data from other parts of Canada are not available for comparison. Environment and Climate Change Canada in collaboration with Health Canada is looking into these compounds further and developing novel ways to assess their potential toxicity.