Pharmaceuticals in Canadian sewage treatment plant effluents and surface waters: occurrence and environmental risk assessment

Abstract

This review compares the occurrence of pharmaceuticals in Canadian sewage treatment plant (STP) effluents and surface waters (SWs) to those from different countries. The occurrence in Canadian aquatic environments was found to be similar to other countries. The most concentrated drugs in STP effluents were: analgesic drugs, salicylic acid (59.6 μg/L) and naproxen (33.9 μg/L); antibiotics, trimethoprim (3.528 μg/L) and sulphamethoxazole (3.278 μg/L); antidepressants, venlafaxine (0.808 μg/L) and fluoxetine (0.799 μg/L); the antiepileptic and mood-stabilizing drug carbamazepine (3.287 μg/L); a lipid regulator gemfibrozil (2.09 μg/L); and atenolol (a β-blocker) reported at a concentration of 1.68 μg/L. The occurrence of pharmaceuticals in Canadian STPs is likely related to drug consumption and water treatment inefficiencies at the STPs investigated. A similar trend was observed for SWs, but the most concentrated drugs were found at lower concentrations such as salicylic acid (17 μg/L), sulphamethoxazole (0.286 μg/L), gemfibrozil (0.58 μg/L), desmethylvenlafaxine (1.472 μg/L), fluoxetine (0.141 μg/L), and carbamazepine (0.7 μg/L). A risk quotient using maximum concentrations of pharmaceuticals, representing a worst-case scenario, was calculated for Canadian STP effluents and SWs, which included analgesics (i.e. ibuprofen, naproxen, and salicylic acid), antibiotics (i.e. sulphamethoxazole, ofloxacin, and ciprofloxacin), antidepressants (i.e. fluoxetine), and lipid regulators (i.e. clofibric acid and gemfibrozil). This risk characterization showed that pharmaceuticals in Canadian STP effluents are suspected to pose a high ecological risk to aquatic organisms, while in SWs, even at the worst-case scenario, a low to medium risk is suspected for all drugs, except sulphamethoxazole.