Wastewater analysis reveals regional variability in exposure to abused drugs and opioids in Finland

Abused drug concentrations were determined in nine Finnish wastewater treatment plants (WWTPs), representing the metropolitan area, university cities and rural towns. In an eight-day study period in August 2012, 24-hour composite influent wastewater samples were collected. Biological markers and census-based information were used to estimate the size of the population served. The analytical method included solid phase extraction, liquid chromatographic separation, tandem mass spectrometric identification, and quantification using isotope-labeled internal standards. The study covered amphetamines, cannabis and cocaine. The levels of some opioids used in treatment and their metabolites were also determined. Amphetamine was the most prevalent drug of abuse, the median loads varying between the cities from 4.16 to 29.6 mg/1000 inhabitants/d. In three western cities methamphetamine was detected in even higher amounts, ranging from 0.87 to 47.5 mg/1000 inhabitants/d. Ecstasy (MDMA) and cocaine (as benzoylecgonine, BE) were found in higher concentrations during weekends compared to weekdays, the difference being statistically significant. The concentration of tetrahydrocannabinol-9-carboxylic acid (THCA) was below the limit of quantification in the two rural towns, while in the other cities the load varied between 3.77 and 20.7 mg/1000 inhabitants/d. The average variation in BE load was 0.05-6.82 and that of MDMA 0-20.6 mg/1000 inhabitants/d. While the metropolitan area showed the highest loads of abused drugs, the substances were continuously detected at all WWTPs included in the study. The median concentration of codeine ranged from 164 to 325 mg/1000 inhabitants/d and that of morphine from 18.8 to 31.5 mg/1000 inhabitants/d. The methadone load was below the level of detection in two towns, and at the other locations were 1.22-9.46 mg/1000 inhabitants/d. The first metabolite of heroin, 6-monoacetylmorphine (6-MAM), was not detected at all. Although the method has limitations, wastewater analysis gives additional information for assessing the degree of drug abuse and range of drugs abused in a society.