The genetic toxicology of organic compounds in natural waters and wastewaters

Abstract

This review was drawn from the literature describing genotoxic organic compounds in natural water (rivers, lakes, streams) and wastewater, as well as from recent discussions with industrial scientists and environmental regulators. Testing of wastewaters for genotoxicity may become a routine requirement for some industrial wastewater discharge permits, not unlike the more common requirement for routine aquatic toxicity tests. The stimuli for this are concerns that aquatic organisms inhabiting waters impacted by wastewater discharges suffer an increased risk of genetic damage or cancer, and that humans utilizing these waters for recreational and drinking water purposes may suffer similar genetic or carcinogenic risks. Some evidence suggests that neoplasia in aquatic organisms is related to habitat contamination, yet field evaluations fail to substantiate adequately a cause-and-effect relationship. Because aquatic organisms respond like mammals to the same genotoxic compounds, the increased burden of genotoxic compounds to the environment may impact certain endemic species. Wastewater discharges may be one source of genotoxic organic compounds in those impacted areas. With respect to potential human health impacts, evidence is supportive of increased cancer risk to individuals drinking water from surface sources; however, this risk may or may not relate to whether the drinking water source received input of wastewater discharges or known carcinogens. Throughout the published literature reviewed herein, the Salmonella/Ames gene mutation test was widely used to assess genotoxic activity, although studies using indigenous plants and aquatic organisms as in vivo monitors of genotoxic activity exist. No “standard” or frequently followed protocols for sample collection, sample processing, selection of tests or their conduct, or interpretation of data exist for most of the genotoxicity studies reviewed. For the Salmonella/Ames test, the aqueous samples were concentrated usually on XAD resin or by liquid:liquid extraction, and without this concentration step few samples exhibited genotoxic activity. Hence, in most instances, the ambient concentration of the compounds causing this activity is below that which is readily detectable by this test, a finding not new to this review. In contrast, aquatic organisms in laboratory and field studies responded to ambient concentrations of genotoxic compounds, thus alleviating the need for sample concentration. However, there appears to be a reluctance to utilize this information for extrapolation to potential human health effects. Unfortunately, no generally accepted and scientifically validated protocol for preparing aqueous samples for genotoxicity testing exists. Developing such a protocol is necessary before embarking on widespread genotoxicity testing of wastewaters, especially if results are to be used for permit compliance. In addition, a systematic review of the aquatic toxicity data generated from routine testing of wastewaters may provide an improved database for environmental risk assessments and extrapolation to human health effects. Which of these data (aquatic toxicity or genotoxicity) offer better utility for risk assessment and in which situation (environmental risk or human health extrapolation) are questions remaining to be addressed.