Drugs of abuse and tranquilizers in Dutch surface waters, drinking ...

RIVM Report 703719064consumption of these Dutch cities is within the range of cocaine consumption for41 Belgian cities as estimated in other studies.Comparison with provisional drinking water limitsThe concentrations of the DOA detected in drinking water are below the generalsignal value of 1 µg/L, which is specified for organic compounds ofanthropogenic origin in the Dutch Drinking water act. To assess possible risks tohuman health, provisional toxicological limits for drinking water were derivedbased on the currently available toxicological knowledge.For the three barbiturates that are detected in finished drinking water, theprovisional drinking water limit is about 1800 times higher than the actualconcentrations detected. Based on this information, effects on public health arenot expected. However, possible effects of combined exposure to multiplecompounds in low concentrations are less clear.For the substances that are detected in raw water (benzoylecgonine, sumoxazepam and temazepam, and sum pentobarbital, phenobarbital and barbital),the provisional drinking water is between 300 and 7000 times higher than theconcentrations detected. For the surface waters of the rivers Rhine and Meuse,the provisional drinking water limits for all substances are more than 1000 timeshigher than the concentrations detected, except for sum oxazepam andtemazepam (provisional drinking water limit 80 times higher).In the STPeffluents, the safety margins between the provisional drinking water limits andthe concentrations detected are smaller. For sum oxazepam and temazepam thethe provisional drinking water limit is smallest: three times higher than themaximum concentration detected. For the other compounds the the provisionaldrinking water l limit is about 100 – 1500 times higher.4.2 RecommendationsAlthough there is no indication of human health risks with respect to thecompounds detected in finished drinking water, alertness is required. Ongoingresearch with respect to possible effects of combined exposure to multiplecompounds in low concentrations needs attention, as well as the development ofanalytical techniques to detect possible new emerging contaminants.As this first screening monitoring campaign was limited, a more thoroughmonitoring yielding information on statistical uncertainty and variability in timeand space is recommended. In order to be able to better evaluate the presenceof DOA in these waters, a more thorough derivation of human andecotoxicological health standards for DOA in surface waters and drinking water isrequired.An ecotoxicological risk assessment of DOA in the aquatic environment isrecommended, especially at locations where these DOA are discharged intosurface waters through STP effluents. Further research is necessary toinvestigate the contributions of STPs with respect to amounts of DOAs that aredischarged into surface waters and the rivers Rhine and Meuse, what kinds ofprocesses occur within the STP, their effects on the fate of the compounds andconcentrations that are detected in STP effluent.Page 47 of 90