wastewater
refereed paper
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 Number of hospital-specific compounds Corresponding STP Number of compounds with a MOE ≤100 Generic name (API)
QEII
CAB
IPS
PC
PA
RBWH
54
56
74
92
112
123
Oxley
Caboolture
Ipswich
0
3
3
Therapeutic class
Luggage Point 8
9
9
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. 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.
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JULY 2012 87