Mature oil sands fine tailings (MFTs) pose a large environmental problem in northern Alberta. GC-MS analyses of the base/neutral (B/N) extract of MFTs PW showed the presence of PACa, such as naphthalene, phenanthrene, dibenzothiophene, fluoranthene, pyrene, chrysene, and their alkylated derivatives. Concentrations of individual PACs did not exceed 500 ng/L, with a total concentration of 2.6 $\mu$g/L.

A calculated benzo (a) pyrene equivalent quotient (BEQ) of the B/N extracts mutagenic potential was equivalent to 0.14 $\mu$g of B (a) P/L. A negative mutagenic response was indicated in strain TA98 and TA100 in the presence of metabolic activation. Ames testing of the concentrated BM extracts in TA98 and TA100 resulted in no detectable positive mutagenic response to detection limits of 0.99 $\mu$g of B (a) P/L (TA98) and 6.3 $\mu$g of B (a) P/L (TA100). A Tier 1 risk assessment, under a worst case scenario, showed no evidence of risk to the wet landscape strategy from the MFTs PW.