Presence of Illicit Drugs and Pharmaceutical Residues in the Wastewaters of an Eastern Canadian City

Tracing consumption patterns of stimulants, opioids, and ketamine in China by wastewater-based epidemiology

Illicit drug use has long been a key issue of international concern, and the true situation is unknown to the relevant authorities. To develop a profile of comprehensive consumption patterns of illicit drugs in China, data from 34 wastewater treatment plants in 25 cities were collected to analyze four classes of drugs, including amphetamine-type stimulants, opioids, ketamine, and cocaine. They were identified and quantified in samples using methods based on gas chromatography coupled to mass spectrometry. According to the wastewater-based epidemiology (WBE) approach, an analysis of the consumption pattern was performed regarding per inhabitant consumption based on the revised metabolic rate. The consumption quantity of illicit drug and precursor was divided into four categories based on statistical difference analyses: methamphetamine and ephedrine (precursor) were the predominant drugs in the first category, followed by ketamine and heroin in the second category, methcathinone and 3,4-methylenedioxymethamphetamine (MDMA) in the third category, and cocaine and methadone in the fourth category. There were distinctive spatial patterns: heroin and cocaine consumption was higher in Southern China than in Northern China, heroin consumption was higher in Western China than in Eastern China, and the consumption of each drug differed across seven regions of China, especially with ephedrine and methcathinone consumption higher in North China; heroin consumption higher in Southwest, Central, and Northwest China; and ketamine and MDMA consumption higher in East, South, and Central China. Compared with findings in previous studies, there were temporal patterns, in which ketamine consumption presented a downward trend but heroin remained stable. Based on correlation analyses, there were the polydrug abuse patterns between heroin and cocaine, methcathinone and ketamine, and cocaine and MDMA. In general, this study based on WBE provides a comprehensive evaluation of drug consumption in China.

A critical review on the detection, occurrence, fate, toxicity, and removal of cannabinoids in the water system and the environment

Cannabinoids are a group of organic compounds found in cannabis. Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD), the two major constituents of cannabinoids, and their metabolites are contaminants of emerging concern due to the limited information on their environmental impacts. As well, their releases to the water systems and environment are expected to increase due to recent legalization. Solid-phase extraction is the most common technique for the extraction and pre-concentration of cannabinoids in water samples as well as a clean-up step after the extraction of cannabinoids from solid samples. Liquid chromatography coupled with mass spectrometry is the most common technique used for the analysis of cannabinoids. THC and its metabolites have been detected in wastewater, surface water, and drinking water. In particular, 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (THC-COOH) has been detected at concentrations up to 2590 and 169 ng L^-1 in untreated and treated wastewater, respectively, 79.9 ng L^-1 in surface water, and 1 ng L^-1 in drinking water. High removal of cannabinoids has been observed in wastewater treatment plants; this is likely a result of adsorption due to the low aqueous solubility of cannabinoids. Based on the estrogenicity and cytotoxicity studies and modelling, it has been predicted that THC and THC-COOH pose moderate risk for adverse impact on the environment. While chlorination and photo-oxidation have been shown to be effective in the removal of THC-COOH, they also produce by-products that are potentially more toxic than regulated disinfection by-products. The potential of indirect exposure to cannabinoids and their metabolites through recreational water is of great interest. As cannabinoids and especially their by-products may have adverse impacts on the environment and public health, more studies on their occurrence in various types of water and environmental systems, as well as on their environmental toxicity, would be required to accurately assess their impact on the environment and public health.

Transformation of Illicit Drugs and Pharmaceuticals in Sewer Sediments

In-sewer stability of human excreted biomarkers is a critical factor of wastewater-based epidemiology in back-estimating illicit drug and pharmaceutical use in the community. Biomarker stability has been investigated in sewers with the presence of biofilms, but the understanding in sewer sediments is still lacking. This study for the first time employed a laboratory sediment reactor to measure 18 illicit drug and pharmaceutical biomarkers under gravity sewer environments with the presence of sediments. Biomarkers exhibited various stability patterns due to transformation processes occurring in the bulk wastewater and sediments. The attenuation of a biomarker by sediments is driven by complex processes involving biodegradation, diffusion, and sorption, which is directly proportional to the ratio of sediment surface area against wastewater volume. The sediment-driven transformation coefficients of biomarkers are higher than the accordingly biofilm-mediated rates because of stronger microbial activities in sediments. Additionally, the stability of most biomarkers was insensitive to the natural pH variation in sewers, except for a few compounds (e.g., methadone, ketamine, and paracetamol) susceptible to pH changes. In general, this study delineates the stability data of various biomarkers in gravity sewers with sediments, which are novel and long-missing information for wastewater-based epidemiology and improve the reliability of back-estimation in complex sewer networks.