By Sarah B. Gewurtz, Alexandra S. Auyeung, Steven Teslic and Shirley Anne Smyth
Municipal wastewater treatment plants (WWTPs) are not designed to remove pharmaceuticals and personal care products (PPCPs) or other chemical substances. Therefore, WWTP effluent discharges and land application of treated biosolids are important pathways for PPCPs to the environment.
Previous research has shown incomplete and highly variable removal efficiencies of PPCPs between chemicals and WWTPs. Wastewater influent can provide information on community usage of PPCPs, whereas effluent and biosolids provide information on PPCPs being released to the environment
Using the results of Environment and Climate Change Canada’s (ECCC) wastewater monitoring program, we evaluated trends of 135 PPCP concentrations in seven representative Canadian WWTPs in 2022, assessed changes during treatment, and evaluated time trends in influent, effluent, and biosolids between 2010-13 and 2022. The PPCPs were chemically analyzed by SGS AXYS Analytical Services Limited (SGS AXYS) using a method based on U.S. EPA Method 1694. The results were published in Environmental Science and Pollution Research.
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PPCP concentrations in influent, effluent and biosolids
The PPCP with the highest concentrations in influent was metformin (Figure 1). It is an antidiabetic widely used in Canada and throughout the world. Four PPCPs in the analgesic/anti-inflammatories category were also present at relatively high concentrations in Canadian wastewater: acetaminophen, ibuprofen and its metabolite 2-hydroxy-ibuprofen, and naproxen.
These substances are easily accessible without a prescription and widely used. The concentrations of caffeine and its metabolite (1,7−dimethylxanthine) were also relatively elevated, which is not surprising considering the popularity of coffee and other caffeine-containing food and beverages.
Theophylline was present at similar concentrations as caffeine. Theophylline is a bronchodilator and is used to treat chronic obstructive pulmonary disease and asthma. Theophylline is also a minor metabolite of caffeine. N,N-diethyl-m-toluamide (DEET), an insect repellent, and iopamidol, which is used as a contrast media for x-rays, were also present at relatively high concentrations in wastewater influents.
The PPCPs dominant in biosolids were different than those found in wastewater and were characterized by their greater sorption to solids (Figure 2). PPCPs with the highest concentrations in biosolids included ciprofloxacin, ofloxacin, and moxifloxacin, which are fluoroquinolone antibiotics used to treat bacterial infections (Figure 2).
Sertraline and citalopram, which are frequently prescribed antidepressants in the selective serotonin reuptake inhibitors family (SSRIs), were also present at high concentrations. Other dominant PPCPs found in biosolids included triclosan, a commonly used preservative and chemical microbial agent that was subjected to risk management activities in 2020; diphenhydramine, an antihistamine that is available without a prescription; doxycycline, a broad-spectrum antibiotic of the tetracycline class; clotrimazole, an antifungal medication that is commonly available without a prescription; and amitriptyline, an antidepressant that is also used off-label to treat chronic pain, anxiety, and insomnia.
Removal of PPCPs during wastewater treatment
For many PPCPs, higher removal was observed at plants that use biological treatment (lagoons, secondary and advanced treatment) compared to primary physical/chemical treatment. The greater PPCP removal in lagoons, secondary, and advanced treatment plants compared to primary WWTPs was likely a result of PPCP biotransformation and greater hydraulic retention time.
PPCP time trends in wastewater
Changes in PPCP concentrations between 2010-13 and 2022 were assessed to evaluate time trends in wastewater (Figure 3). A detailed analysis of the time trends of PPCPs in influent, effluent, and biosolids is available in our paper published in Environmental Science and Pollution Research.
The concentrations of many PPCPs did not change consistently over time. For example, concentrations of over-the-counter pharmaceuticals including analgesic/anti-inflammatories (i.e., acetaminophen, ibuprofen and its metabolite 2-hydroxy-ibuprofen, and naproxen), as well as the antihistamine, diphenhydramine, did not change significantly with time in wastewater matrices.
The lack of time change for these chemicals was likely because they are easily accessible and popular for treating common ailments. Cotinine is a metabolite of nicotine. Although there has been a reduction in smoking in Canada since 2010, our data indicate no changes in cotinine concentrations in wastewater between 2010-13 and 2022. This could be due to increased use of non-tobacco nicotine products (vaping, nicotine replacement therapies, etc.).
Metformin is an example of a PPCP that increased in wastewater matrices over time. The rate of diagnosed diabetes is increasing in Canada and in 2008, the Canadian Diabetes Association (CDA) recommended metformin as the initiating treatment for patients newly diagnosed with type 2 diabetes due to lower incidence of side effects and its relatively cheap cost compared to other medications.
Concentrations of sertraline and theophylline also increased in wastewater over time. The Canadian Paediatric Society indicated sertraline as a second line of treatment for depression and there has been a shift towards prescribing sertraline to children and adolescents. It was also shown to exhibit antiviral activity against SARS-CoV-2 and to alleviate symptoms associated with infection.
Theophylline is a respiratory medication that was found to be an effective treatment for the symptoms of the SARS-CoV-2 virus. Therefore, it is possible that concentration increases of sertraline and theophylline in Canadian wastewater are associated with the COVID-19 pandemic. Additional data between 2013 and 2020 would strengthen this hypothesis.
Concentrations of many of the antibiotics included in this study decreased in Canadian wastewater matrices between 2010-13 and 2022. These decreases could be due to greater awareness of antimicrobial resistance and efforts to reduce antibiotic use.
Triclosan concentrations decreased significantly between 2010-13 and 2022 in wastewater media. It had the third highest median concentration in biosolids of all the PPCPs analyzed in this study but was subjected to risk management activities in 2020.
Future directions
The time trends of PPCPs in wastewater matrices between 2010-13 and 2022 varied and may have been influenced by factors such as risk management measures, warnings, development of new pharmaceuticals, and the COVID-19 pandemic. In Canada, there is limited information on PPCP use in the community and release into the environment. Our wastewater data reflect the limited information available and therefore continued periodic monitoring of PPCPs in wastewater matrices is recommended to fill data gaps.
Acknowledgements
© Crown 2025. This study was published under a Creative Commons license, is open access, and is available at: https://doi.org/10.1007/s11356-025-36007-0. The data used in this study are available at: https://data-donnees.az.ec.gc.ca/data/substances/monitor/chemicals-management-plan-wastewater-monitoring-program/?lang=en.
Sarah B. Gewurtz, Steven Teslic, and Shirley Anne Smyth are with Environment and Climate Change Canada. Alexandra S. Auyeung was with Environment and Climate Change Canada at the time the work was completed and is now at the University of Toronto. For more information, email: shirleyanne.smyth@ec.gc.ca
This article appeared in the April 2025 edition of Environmental Science & Engineering Magazine. Read the full issue below.
