Wastewater treatment plants (WWTPs) are a primary source of many contaminants to the environment. Processing complex mixtures of waste, they can result in the continuous discharge of bioactive and endogenous compounds into sensitive aquatic ecosystems. Isoprostanes (IsoPs) are a class of potential emerging contaminants, produced in a range of vertebrate species, including humans, in response to oxidative stress. Released following exposure to various toxicants or disease, IsoPs are also mediators of inflammatory processes. Even in the low nanomolar range, these compounds have potent biological activities and can induce multiple pathophysiological responses, stimulating the continuation of oxidative stress. Their urinary excretion provides a mechanism for the entry of IsoPs to WWTPs and subsequently the wider environment, where they may initiate a cycle of oxidative stress in aquatic biota exposed to these compounds. Following which, additional IsoPs may be produced within these organisms, further perpetuating this cycle of toxicity.

To examine WWTPs as a source of IsoPs to the environment, an analytical method for their detection in wastewater based on solid phase extraction (SPE) and gas chromatography mass spectroscopy (GC-MS) was developed. Firstly, the novel method involved a deconjugation treatment with b-glucuronidase to increase the concentration of IsoPs available for detection. Subsequently, SPE followed by either silica gel chromatography or hexane liquid-liquid extraction were used to extract and purify the samples, removing the matrix inferences. Finally, a MSTFA derivatisation method was developed and resulted in the reliable detection of these compounds through GC-MS analysis.

A survey of Canterbury WWTPs was then conducted to assess the concentrations of IsoPs present in both wastewater influent and effluent. These compounds were detected at three of the four WWTPs assessed, with recovery-corrected concentrations ranging from ND-79.9 ng/L and ND-55.9 ng/L in the influent and effluent, respectively. As IsoPs were detected in wastewater effluent, this indicates that these compounds are not sufficiently removed during the treatment process, and that WWTPs may represent a source of these compounds to the environment. Further research is required to improve the extraction and purification methods in order to reliably assess the concentrations of IsoPs in wastewater. A series of comprehensive environmental surveys and ecotoxicological assays are also necessary to determine the potential roles of IsoPs as emerging contaminants.