Water Journal : Water Journal July 2012
refereed paper wastewater water JULY 2012 87 hospital wastewater. The highest degree of E. coli resistance that they observed was for the antibiotic tetracycline. Among the six hospitals investigated in our study, RBWH was found to be a major contributor to the loads of tetracycline in municipal wastewater, but corresponding MOEs in both hospital effluent and municipal wastewater were well above 100,000. This suggests that if our approach helps in screening antibiotics for which hospitals would be major contributors and of potential concern for human health, further investigations on potential human health risks resulting from the spread of antibiotic-resistant bacteria that may originate from hospitals are warranted. Seven antineoplastic agents (anagrelide, capecitabine, procarbazine, carmustine, vincristine, busulfan and mitomycin) presented MOE values below 100 in the hospital effluents at four of the six hospitals investigated. But concentrations in the corresponding STPs dropped significantly, making vincristine the only cytotoxic compound remaining with a MOE below 100 in the catchment of PA and PC hospitals (Table 1), with concentrations below 0.012μg L-1. Although such a concentration seems low and in accordance with low concentrations typically observed for this category of substances in the environment (Webb, 2004), it would deserve additional investigations. Indeed, anticancer drugs are among the most toxic substances used in medicine and are known to be poorly biodegradable (Aherne et al., 1990; Kümmerer, 2004). The real impact of hospital effluents on the load of anticancer drugs in municipal wastewater is difficult to assess. The administration of some of these compounds to outpatients, as well as the slow excretion of some of these substances (e.g. capecitabine, fluorouracil) means that significant fractions of antineoplastic drugs are excreted at home (Johnson et al., 2008). A trend towards home-based administration of anticancer treatments has recently been confirmed in France by Besse et al. (2012). Their analysis of consumption data from a local chemotherapy centre showed that 50% of the antineoplastic agents consumed in that centre were prescribed to outpatients and that only 20% of the drugs prescribed to outpatients were excreted onsite. This trend implies that hospitals may no longer be a major source of chemotherapeutic drugs. Conclusions The consumption-based approach used in this study showed that the contribution of hospitals towards the total load of pharmaceuticals in the influent of STPs is limited. Indeed, the six hospitals investigated overall were found to contribute less than 6% of the total mass of APIs consumed in a catchment. For up to 84% of the 589 APIs evaluated, the contribution of an individual hospital is likely to be less than 15%. However, depending on the hospital investigated, hospital contributions of 100% were obtained for 54 to 123 APIs. Among these hospital-specific compounds, the predicted concentrations of only 12 compounds were less than 100 times below a concentration "of no concern" in the influent of STPs. They warrant more detailed investigations including environmental and human toxicity, biodegradation and treatment or source control options. However, it should be noted that concentrations of pharmaceuticals in raw wastewater are expected to be significantly reduced after conventional wastewater treatment and advanced water treatment. Therefore, the results obtained for hospital-specific compounds indicate that these are unlikely to be present in STP effluents at levels representing a risk to humans. The outcomes of this study then suggest that decentralised treatment of hospital wastewater to reduce pharmaceutical loads in municipal wastewater would be of limited benefit. However, additional aspects, including the impact of hospital wastewater on the propagation of antibiotic-resistant bacteria, will require specific attention to fully evaluate whether source treatment of hospital wastewater is relevant or not. Table 1. List of hospital-specific compounds* with an MOE below 100 in influents of the STPs to which the hospitals investigated discharge their effluents (values in grey are MOE values above 100). Hospitals QEII CAB IPS PC PA RBWH Number of hospital-specific compounds 54 56 74 92 112 123 Corresponding STP Oxley Caboolture Ipswich Luggage Point Number of compounds with a MOE ≤100 0 3 3 8 9 9 Generic name (API) Therapeutic class MOE 1 Bupivacaine AA 33663 71 47 69 69 69 2 Piperacillin AB 7599 79 2058 8 8 8 3 Tazobactam AB 3030 32 820 3 3 3 4 Oxybuprocaine AA 594 248 126 71 71 71 5 Pancuronium NB 1122 NU 912 48 48 48 6 Ropivacaine AA 532 365 892 68 68 68 7 Tropicamide MY 2121 1415 519 53 53 53 8 Cefazolin AB NC NC NC 32 NC NC 9 Infliximab ARh NU NU NU NU 81 81 10 Vincristine sulphate AN NU NU NU NU 0.4 0.4 11 Levobupivacaine AA 67325 447 100 NU NU 2978 12 Suxamethonium AA 15213 256 98 371 357 357 AA = Anaesthetic agent; AB = Antibiotic; AN = Antineoplastic; ARh = Antirheumatic agent; MY = Mydriatic; NB = Neuromuscular blocking agent; NU = Not used at the hospital; NC = Not considered (i.e. contribution <97%). *Contributions comprised between 97% and 100% were taken into account.
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